Canadian Researchers Link DICER1 Gene Mutation to Non-Epithelial Ovarian Cancers & Other Rare Tumor Types

Canadian researchers affiliated with the Ovarian Cancer Research Program of British Columbia report that recurrent, lifetime-acquired mutations affecting the DICER1 gene occur in a range of nonepithelial ovarian tumors as well as other rare cancer tumor types, and appear common in Sertoli-Leydig ovarian tumors. The study findings were published online today in the New England Journal of Medicine.

Dr. Gregg Morin, Head of Proteomics, Michael Smith Genome Sciences Centre, BC Cancer Agency; DICER 1 Mutation Ovarian Cancer Study Co-Leader

Dr. David Huntsman, Genetic Pathologist & Director of the Ovarian Cancer Research Program of British Columbia at the BC Cancer Agency & Vancouver Coastal Health Research Institute; DICER 1 Mutation Ovarian Cancer Study Co-Leader

Scientists at the British Columbia (BC) Cancer Agency, Vancouver Coastal Health Research Institute, and the University of British Columbia (UBC) are excited over a discovery made while studying rare tumor types.

Dr. David Huntsman, genetic pathologist and director of the Ovarian Cancer Program of BC (OvCaRe) at the BC Cancer Agency and Vancouver Coastal Health Research Institute, and Dr. Gregg Morin, a lead scientist from the Michael Smith Genome Sciences Centre at the BC Cancer Agency, led a research team who discovered that mutations in rare, seemingly unrelated cancers were all linked to the same gene, known as “DICER1.” The study findings were published online today in the New England Journal of Medicine. [1]

Background: RNA Interference, MicroRNAs, and DICER.

Nucleic acids are molecules that carry genetic information and include DNA (deoxyribonucleic acid) and RNA (ribonucleic acid). The DNA segments that carry genetic information are called “genes.” Together these molecules form the building blocks of life. DNA contains the genetic code or “blueprint” used in the development and functioning of all living organisms, while “messenger RNAs” or mRNAs help to translate that genetic code into proteins by acting as a messenger between the DNA instructions located in the cell nucleus and the protein synthesis which takes place in the cell cytoplasm (i.e., outside the cell nucleus, but inside the outer cell membrane). Accordingly, DNA is first “transcribed” or copied into mRNA, which, in turn, gets “translated” or synthesized into protein.

RNA interference” (RNAi) is a mechanism through which gene expression is inhibited at the translation stage, thereby disrupting the protein production within a cell. RNAi is considered one of the most important discoveries in the field of molecular biology. Andrew Fire, Ph.D., and Craig C. Mello, Ph.D. shared the 2006 Nobel Prize in Physiology or Medicine for work that led to the discovery of the RNAi mechanism. While the mechanism itself is termed “RNA interference,” there are two major types of RNA molecules that play a key role in effectuating that interference. The first type of RNA molecules consists of “microRNAs” or miRNAs, while the second type consists of “small interfering RNAs” or siRNAs.

Current thinking suggests that RNAi evolved as a cellular defense mechanism against invaders such as RNA viruses. When they replicate, RNA viruses temporarily exist in a double-stranded form. This double-stranded intermediate would trigger RNAi and inactivate the virus’ genes, thereby preventing viral infection. RNAi may also have evolved to combat the spread of genetic elements called “transposons” within a cell’s DNA. Transposons can wreak havoc by jumping from spot to spot on a genome, sometimes causing mutations that can lead to cancer or other diseases. Like RNA viruses, transposons can take on a double-stranded RNA form that would trigger RNAi to clamp down on the potentially harmful “jumping gene” activity. Also, as noted above, RNAi is important for regulating gene expression. For example, the turning down of specific genes is critical to proper embryonic development.

Of relevance to the Canadian study findings within the context of RNAi are miRNAs. MiRNAs can bind to mRNAs and either increase or decrease their activity, for example, by preventing a mRNA from producing a protein. [2] In this context, “gene silencing” can occur through mRNA degradation or prevention of mRNA translation.  MiRNAs play an integral role in numerous biological processes, including the immune response, cell-cycle control, metabolism, viral replication, stem cell differentiation and human development. MiRNA expression or function is significantly altered in many disease states, including cancer.

Because of its involvement in miRNA processing, the DICER1 gene plays an important role in maintaining health. It carries out a “factory style” function which involves chopping up miRNAs to activate them. [Ref. 2] These miRNAs, in turn, control hundreds of other genes as noted above. Based upon a study led by investigators from the University of Texas M.D. Anderson Cancer Center, the expression levels of DICER have global effects on the biogenesis of miRNA, and reduced gene expression correlates with a poor outcome in ovarian cancer. [3] In the M.D. Anderson study, two somatic (i.e., lifetime-acquired) missense DICER mutations were discovered in two epithelial ovarian cancer tumors. The M.D. Anderson investigators concluded that the DICER mutations were not associated with the alterations in DICER expression found in mRNAs. It is important to note that the type of somatic missense DICER mutations discovered in the M.D. Anderson study were not the same as those discovered in the Canadian study as discussed below.

Recurrent DICER Mutations Are Predominant In A Rare Form of Non-Epithelial Ovarian Cancer.

At the outset of the Canadian study, the OvCaRe team sequenced ovarian, uterine, and testicular tumors, expecting to find that their genomes would be distinct with specific, differing abnormalities. Much to their amazement, the researchers discovered that the same fundamental mutation in the DICER1 gene represented a common process underlying the different cancers which they examined.

Specifically, the Canadian investigators sequenced the whole transcriptomes or exomes of 14 nonepithelial ovarian tumors, which included two Sertoli–Leydig cell tumors, four juvenile (not adult) granulosa-cell tumors, and eight primitive germ-cell tumors of the yolk-sac type. The researchers identified closely clustered mutations in the region of DICER1 which encode the RNase IIIb domain in four samples. Based on these findings, the OvCaRe team sequenced the same region of DICER1 in additional ovarian tumors, and tested for the effect of the mutations on the enzymatic activity of DICER1.

Recurrent somatic (i.e., lifetime-acquired) DICER1 mutations in the RNase IIIb domain were identified in 30 of 102 nonepithelial ovarian tumors (29%), including 4 tumors which also possessed germline (i.e., inherited) DICER1 mutations. The highest frequency of somatic DICER1 mutations occurred in Sertoli–Leydig cell tumors (26 of 43, or 60%). Notably, the mutant DICER1 proteins identified in the samples possessed reduced RNase IIIb activity, but retained RNase IIIa activity.

The Canadian researchers also performed additional tumor testing and detected the DICER1 mutations in 1 of 14 nonseminomatous testicular germ-cell tumors, 2 of 5 embryonal rhabdomyosarcomas, and in 1 of 266 epithelial ovarian and endometrial carcinomas.

The groundbreaking nature of this discovery is reflected in the fact that the DICER1 “hotspot” mutations are not present in the 1000 Genomes Project data or the public data repository of The Cancer Genome Atlas consortium. To date, no recurrent DICER1 mutations have been reported in the mutation database of the Catalogue of Somatic Mutations in Cancer (COSMIC), in which 4 of 938 reported cancers possess somatic mutations but none in the RNase IIIb domain hot spots or RNase IIIa equivalents. Moreover, the Canadian researchers note that the newly-discovered DICER1 mutations were not observed in any of the more than 1000 cancer sequencing libraries which were studied.

Based upon the foregoing , the researchers concluded that somatic missense mutations affecting the RNase IIIb domain of DICER1 occur in a range of nonepithelial ovarian tumors, and possibly other cancers. Furthermore, the DICER1 mutations appear to be common in Sertoli-Leydig ovarian tumors (which are a subtype of nonepithelial, sex cord-stromal ovarian tumors). The researchers believe that the recurrent DICER1 mutations identified implicate a novel defect in miRNA processing which does not entirely destroy DICER1 functionality, but alters it.

Accordingly, the Canadian researchers suggest that the newly-discovered DICER1 mutations may represent an oncogenic event within the specific context of nonepithelial ovarian tumors, rather than a permissive event in tumor onset (as may be expected for loss of function in a tumor suppressor gene). The researchers note that DICER1 expression in tumors possessing the hotspot DICER1 somatic mutations argues against a role for DICER1 as a classic tumor suppressor gene. They further explain that the localized and focal pattern of the identified DICER1 mutations is typical of dominantly acting oncogenes, like KRAS and BRAF.

In sum, the Canadian researchers believe that the recurrent and focal nature of the DICER1 mutations and their restriction to nonepithelial ovarian tumors suggest a common oncogenic mechanism associated with a specifically altered DICER1 function that is selected during tumor development in specific cell types.

The Canadian study was supported through funding by Canadian Institutes for Health Research, Terry Fox Foundation, BC Cancer Foundation, VGH & UBC Hospital Foundation, Michael Smith Foundation for Health Research, and Genome BC.

Expert Commentary

DICER is of great interest to cancer researchers” said Dr. Huntsman, who also holds the Dr. Chew Wei Memorial Professorship in the departments of Obstetrics and Gynecology and Pathology and Laboratory Medicine at UBC. “There have been nearly 1,300 published studies about it in the last 10 years, but until now, it has not been known how the gene functions in relation to cancer.”

“This discovery shows researchers that these mutations change the function of DICER so that it participates directly in the initiation of cancer, but not in a typical ‘on-off’ fashion,” says Dr. Morin who is also assistant professor in the department of Medical Genetics at UBC. “DICER can be viewed as the conductor for an orchestra of functions critical for the development and behavior of normal cells. The mutations we discovered do not totally destroy the function of DICER rather they warp it—the orchestra is still there but the conductor is drunk.”

This finding is the third of a series of papers published recently in the New England Journal of Medicine (NEJM) in which the OvCaRe team used new genomic technologies to unlock the molecular basis of poorly understood types of ovarian cancer. The first finding, published in the NEJM in 2009, identified mutations in the FOXL2 (forkhead box L2) gene as the molecular basis of adult granulosa cell ovarian cancer tumors. The second finding, published in the NEJM in 2010, determined that approximately one-half of clear-cell ovarian cancers and one-third of endometrioid ovarian cancers possess ARID1A  (AT rich interactive domain 1A) gene mutations.

The DICER gene mutation breakthrough discovery is particularly pivotal because it could lead to solutions for treatment of more common cancers.

“Studying rare tumors not only is important for the patients and families who suffer from them but also provides unique opportunities to make discoveries critical to more common cancers – both in terms of personalized medicine, but also in applying what we learn from how we manage rare diseases to more common and prevalent cancers,” said Dr. Huntsman “The discovery of the DICER mutation in this varied group of rare tumors is the equivalent of finding not the needle in the haystack, but rather the same needle in many haystacks.”

Dr. Phillip A. Sharp, Professor, Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology; Co-winner of the 1993 Nobel Prize in Physiology and Medicine

“This breakthrough will be of interest to both the clinical and the fundamental science communities,” says Dr. Phillip A. Sharp, Professor, Koch Institute for Integrative Cancer Research at the Massachusetts Institute of Technology, and co-winner of the 1993 Nobel Prize in Physiology or Medicine for the discovery that genes are not contiguous strings but contain introns, and that the splicing of mRNA to delete those introns can occur in different ways, thereby yielding different proteins from the same DNA sequence. “Huntsman, Morin and colleagues’ very exciting discovery of specific mutations in DICER, a factor essential for syntheses of small regulatory RNAs in ovarian and other human tumors, could lead to new approaches to treatment.”

The Canadian OvCaRe research team is now working to determine the frequency and role of DICER mutations in other types of cancers. The research team is also expanding its collaboration to discover whether mutant DICER and the pathways it controls can be modulated to treat the rare cancers in which the mutations were discovered and more common cancers.

The Michael Smith Genome Sciences Centre (Michael Smith GSC), located at the BC Cancer agency, played a key role in this discovery. By way of background, Dr. Michael Smith was a co-winner of the 1993 Nobel Prize in Chemistry for his development of oligonucleotide-based site-directed mutagenesis, a technique which allows the DNA sequence of any gene to be altered in a designated manner. His technique created a groundbreaking method for studying complex protein functions, the basis underlying a protein’s three-dimensional structure, and a protein’s interaction with other molecules inside the cell.

A decision was made more than 10 years ago, championed by Drs. Michael Smith, Victor Ling, and others to create and locate the Michael Smith GSC within the BC Cancer Agency and in close proximity to Vancouver General Hospital (VGH). The chosen location for this critical facility provided the multidisciplinary cancer research teams in Vancouver with access to state-of-the-art technologies.

“We are one of less than five places in the world doing this type of work successfully. This discovery is one of a series of recent landmark findings from Vancouver that are reshaping our understanding of many cancers,” says Dr. Huntsman. “Since my arrival in Vancouver 20 years ago I have never before sensed such a strong feeling of communal pride and excitement within our research community. Our next task is to bring the discoveries into the clinic.”

About the Ovarian Cancer Research Program of British Columbia (OvCaRe)

OvCaRe is a multidisciplinary research program involving clinicians and research scientists in gynecology, pathology, and medical oncology at VGH and BC Cancer Agency. OvCaRe is a unique collaboration between the BC Cancer Agency, Vancouver Coastal Health Research Institute, and UBC. The OvCaRe team is considered a leader in ovarian cancer research which is breaking new ground in better identifying, understanding, and treating this disease. The OvCaRe seminal paper in PLoS (Public Library of Science), which addresses ovarian cancer as a group of distinct diseases, has been embraced by the global research community who has adopted the BC approach to ovarian cancer research. To learn more, visit www.ovcare.ca.

About the Michael Smith Genome Sciences Centre

Canada’s Michael Smith Genome Sciences Centre is an internationally recognized state-of-the-art facility applying genomics and bioinformatics tools and technologies to cancer research. Led by Dr. Marco Marra, the Michael Smith GSC is one of ten leading genomic research centres in the world and the only one of its kind in the world integrated into a cancer facility. With a primary focus on cancer genomics research, its scientists have been involved in many world-class groundbreaking discoveries over the past decade. To learn more, visit www.bcgsc.ca.

About the Vancouver Coastal Health Research Institute

Vancouver Coastal Health Research Institute is the research body of Vancouver Coastal Health Authority, which includes BC’s largest academic and teaching health sciences centres: Vancouver General Hospital, UBC Hospital, and GF Strong Rehabilitation Centre. The institute is academically affiliated with the UBC Faculty of Medicine, and is one of Canada’s top-funded research centres, with $82.4 million in research funding for 2009/2010. To learn more, visit www.vchri.ca.

About the British Columbia Cancer Agency

The BC Cancer Agency, an agency of the Provincial Health Services Authority, is committed to reducing the incidence of cancer, reducing the mortality from cancer, and improving the quality of life of those living with cancer. It provides a comprehensive cancer control program for the people of British Columbia by working with community partners to deliver a range of oncology services, including prevention, early detection, diagnosis and treatment, research, education, supportive care, rehabilitation and palliative care. To learn more, visit www.bccancer.ca.

About the University of British Columbia

The University of British Columbia is one of North America’s largest public research and teaching institutions, and one of only two Canadian institutions consistently ranked among the world’s 40 best universities. Surrounded by the beauty of the Canadian West, it is a place that inspires bold, new ways of thinking that have helped make it a national leader in areas as diverse as community service learning, sustainability, and research commercialization. UBC offers more than 55,000 students a range of innovative programs and attracts $550 million per year in research funding from government, non-profit organizations, and industry through 7,000 grants. To learn more, visit www.ubc.ca.

References

1/Morin G, Hunstman, DG et al.  Recurrent Somatic DICER1 Mutations in Nonepithelial Ovarian CancersNEJM, published online December 21, 2011 (10.1056/NEJMoa1102903).

2/The Canadian investigators describe the operation of the RNAi pathway with respect to miRNA biogenesis as follows:

“MicroRNAs (miRNAs) are a functional class of noncoding RNA molecules that regulate translation and degradation of messenger RNA. MiRNA transcripts are processed from hairpin pre-miRNA precursors into short miRNA:  miRNA* duplexes consisting of the miRNA targeting strand and the imperfectly complementary miRNA* strand (star strand, or inert carrier strand) by Dicer, an endoribonuclease with two RNase III–like domains. The RNase IIIb domain cuts the miRNA strand, whereas the RNase IIIa domain cleaves the miRNA* strand. The resultant RNA duplex is loaded into the RNA-induced silencing complex (RISC) containing an Argonaute protein. The miRNA* strand is then removed, leaving the miRNA strand, which targets messenger RNAs (mRNAs) for degradation or interacts with the translation initiation complex to inhibit and destabilize translation of the targeted messenger RNAs.” [footnote citations omitted]

3/Merritt WM, et al. Dicer, Drosha, and outcomes in patients with ovarian cancer. N Engl J Med. 2008 Dec 18;359(25):2641-50. Erratum in: N Engl J Med. 2010 Nov 4;363(19):1877. PubMed PMID: 19092150; PubMed Central PMCID: PMC2710981.

Sources:

FDA Approves Clinical Protocol for Additional Phase 1 Study of TKM-PLK1 in Primary Liver Cancer or Liver Metastases

The U.S. Food and Drug Administration approves the clinical protocol for an additional Phase 1 study of TKM-PLK1 in patients with either primary liver cancer or liver metastases associated with select cancers including ovarian.

RNA Interference

Nucleic acids are molecules that carry genetic information and include DNA (deoxyribonucleic acid) and RNA (ribonucleic acid). Together these molecules form the building blocks of life. DNA contains the genetic code or “blueprint” used in the development and functioning of all living organisms, while one type of RNA (i.e., “messenger RNA” or mRNA) helps to translate that genetic code into proteins by acting as a messenger between the DNA instructions located in the cell nucleus and the protein synthesis which takes place in the cell cytoplasm (i.e., outside the cell nucleus, but inside the outer cell membrane). Accordingly, DNA is first copied or transcribed into mRNA, which, in turn, gets translated or synthesized into protein.

The molecular origin of many diseases results from either the absence or over-production of specific proteins. “RNA interference” (RNAi) is a mechanism through which gene expression is inhibited at the translation stage, thereby disrupting the protein production. RNAi is considered one of the most important discoveries in the field of molecular biology. Andrew Fire, Ph.D., and Craig C. Mello, Ph.D. shared the 2006 Nobel Prize in Physiology or Medicine for work that led to the discovery of the RNAi mechanism.  Because many diseases – cancer, metabolic, infectious and others – are caused by the inappropriate activity of specific genes, the ability to silence genes selectively through RNAi offers the potential to revolutionize the way we treat disease and illness by creating a new class of drugs aimed at eliminating specific gene-products or proteins from the cell. RNAi has been convincingly demonstrated in preclinical models of oncology, influenza, hepatitis, high cholesterol, diabetes, macular degeneration, Parkinson’s disease, and Huntington’s disease.

Small Interfering RNA 

While the mechanism itself is termed “RNAi,” the therapeutic agents that exert the effect are known as “small interfering RNAs” or siRNAs. Sequencing of the human genome has provided the information needed to design siRNA therapeutics directed against a wide range of disease-causing proteins. Based on the mRNA sequence for the target protein, a siRNA therapeutic can be designed relatively quickly compared to the time needed to synthesize and screen conventional small molecule drugs. Moreover, siRNA-based therapeutics are able to bind to a target protein mRNA with great specificity. When siRNA are introduced into the cell cytoplasm they are rapidly incorporated into an “RNA-induced silencing complex” (RISC) and guided to the target protein mRNA, which is then cut and destroyed, preventing the subsequent production of the target protein. The RISC can remain stable inside the cell for weeks, destroying many more copies of the target mRNA and maintaining target protein suppression for long periods of time.

To our knowledge, there are no siRNAs approved yet for medical use outside of a clinical trial, however, a number of R&D initiatives and clinical trials are currently underway, with one of the main areas of research focused on delivery. Because siRNAs are large, unstable molecules, they are unable to access target cells. Delivery technology is required to stabilize these drugs in the human blood stream, allow efficient delivery to the target cells, and facilitate uptake and release into the cell cytoplasm. Tekmira Pharmaceuticals Corporation, a leading developer of RNAi therapeutics has focused its research on identifying lipid nanoparticles (LNPs) that can overcome the challenges of delivering siRNAs.

TKM-PLK1 

TKM-PLK1 is being developed as a novel anti-tumor drug in the treatment of cancer. LNPs are particularly well suited for the delivery of siRNA to treat cancer because the lipid nanoparticles preferentially accumulate within tissues and organs having leaky blood vessels, such as cancerous tumors. Once at the target site, LNPs are taken up by tumor cells and the siRNA payload is delivered inside the cell where it reduces expression of the target protein. Through careful selection of the appropriate molecular targets, LNPs are designed to have potent anti-tumor activity yet be well tolerated by healthy tissue adjacent to the tumor.

Tekmira has taken advantage of this passive targeting effect to develop an siRNA directed against PLK1 (polo-like kinase 1), a protein involved in tumor cell proliferation. Inhibition of PLK1 prevents the tumor cell from completing cell division, resulting in cell cycle arrest and cell death.

Because the standard of care for cancer treatment often involves the use of drug combination therapies, Tekmira has selected gene targets for its oncology applications that synergize with conventional drugs that are currently in use. TKM-PLK1 has the potential to provide both direct tumor cell killing and sensitization of tumor cells to the effects of chemotherapy drugs.

Phase 1 Study of TKM-PLK1 in Primary Liver Cancer or Liver Metastases

Tekmira, along with its collaborators at the U.S. National Cancer Institute (NCI), announced that they have received approval from the U.S. Food and Drug Administration (FDA) to proceed with a new Phase 1 clinical trial for Tekmira’s lead oncology product, TKM-PLK1. This trial, run in parallel with the ongoing Phase 1 trial of TKM-PLK1 (for adult patients with solid tumors or lymphomas that are refractory to standard therapy), provides Tekmira with an early opportunity to validate the mechanism of drug action.

“Patients in this new study, who will have either primary liver cancer or liver metastases, will receive TKM-PLK1 delivered directly into the liver via Hepatic Artery Infusion (HAI). The trial design will allow us to measure tumor delivery, polo-like kinase 1 (PLK1) messenger RNA knockdown, and RNA interference (RNAi) activity in tumor biopsies from all of the patients treated,” said Dr. Mark J. Murray, Tekmira’s President and CEO.

“This NCI clinical trial will run in parallel with our multi-center TKM-PLK1 solid tumor Phase 1 trial, currently underway at three centers in the United States. Working together on this clinical trial with our collaborators at the NCI will allow us to develop an even more robust data package to inform subsequent TKM-PLK1 development. We expect to have interim TKM-PLK1 clinical data before the end of 2011,” added Dr. Murray.

The NCI trial is a Phase 1 multiple-dose, dose escalation study testing TKM-PLK1 in patients with unresectable colorectal, pancreatic, gastric, breast, ovarian and esophageal cancers with liver metastases, or primary liver cancers. These patients represent a significant unmet medical need as they are not well served by currently approved treatments.

The primary objectives of the trial include evaluation of the feasibility of administering TKM-PLK1 via HAI, and characterization of the pharmacokinetics and pharmacodynamics of TKM-PLK1. Pharmacodynamic measurements will examine the effect of the drug on the patient’s tumors, specifically aiming to confirm PLK1 knockdown and RNAi activity. Typically reserved for later stage trials, pharmacodynamic measurements are facilitated in this Phase 1 trial in part through the unique capabilities of the NCI Surgery Branch. Secondary objectives of the trial include establishing maximum tolerated dose and to evaluate response rate.

About the National Cancer Institute

The National Cancer Institute (NCI) is one of 27 institutes and centers under the oversight of the U.S. National Institutes of Health (NIH), and is the primary cancer medical research agency in the U.S. The TKM-PLK1 trial will involve investigators at the NCI’s Center for Cancer Research (CCR) on the main NIH campus located in Bethesda, Maryland. The CCR is home to more than 250 scientists and clinicians working in intramural research at the NCI. CCR’s investigators include some of the worlds most experienced basic, clinical, and translational scientists who work together to advance our knowledge of cancer and develop new therapies.

About TKM-PLK1

TKM-PLK1 targets polo-like kinase 1, or PLK1, a cell cycle protein involved in tumor cell proliferation and a validated oncology target. Cancer patients whose tumors express high levels of PLK1 have a relatively poor prognosis. Inhibition of PLK1 prevents tumor cells from completing cell division, resulting in cell cycle arrest and cancer cell death.

About RNAi and Tekmira’s LNP Technology

RNAi therapeutics have the potential to treat a broad number of human diseases by “silencing” disease causing genes. The discoverers of RNAi, a gene silencing mechanism used by all cells, were awarded the 2006 Nobel Prize for Physiology or Medicine. RNAi therapeutics, such as “siRNAs,” require delivery technology to be effective systemically. LNP technology is one of the most widely used siRNA delivery approaches for systemic administration. Tekmira’s LNP technology (formerly referred to as “stable nucleic acid-lipid particles” or SNALP) encapsulates siRNAs with high efficiency in uniform lipid nanoparticles which are effective in delivering RNAi therapeutics to disease sites in numerous preclinical models. Tekmira’s LNP formulations are manufactured by a proprietary method which is robust, scalable and highly reproducible and LNP-based products have been reviewed by multiple FDA divisions for use in clinical trials. LNP formulations comprise several lipid components that can be adjusted to suit the specific application.

About Tekmira Pharmaceuticals Corporation

Tekmira Pharmaceuticals Corporation is a biopharmaceutical company focused on advancing novel RNAi therapeutics and providing its leading lipid nanoparticle delivery technology to pharmaceutical partners. Tekmira has been working in the field of nucleic acid delivery for over a decade and has broad intellectual property covering LNPs. Further information about Tekmira can be found at www.tekmirapharm.com. Tekmira is based in Vancouver, British Columbia, Canada.

Source

Clinical Trial Information

  • A Phase 1 Dose Escalation Study to Determine the Safety, Pharmacokinetics, and Pharmacodynamics of Intravenous TKM-080301 [a/k/a TKM-PLK1 or PLK1 SNALP] in Patients With Advanced Solid Tumors [or Lymphomas], ClinicalTrials.gov Identifier: NCT01262235. [Note: This clinical trial summary relates to the ongoing Phase 1 TKM-PLK1  solid tumor clinical trial. We will post the second Phase 1 TKM-PLK1 clinical trial summary with respect to primary liver cancer and liver metastases once it becomes publicly available]
Additional Information
  • Wang J, et al. Delivery of siRNA therapeutics: barriers and carriers. AAPS J. 2010 Dec;12(4):492-503. Epub 2010 Jun 11. Review. PubMed PMID: 20544328; PubMed Central PMCID: PMC2977003.

FDA Awards $1.6M Orphan Drug Grant for Clinical Phase II Development of EGEN-001 for Treatment of Ovarian Cancer

EGEN, Inc. announced that the Food and Drug Administration (FDA) awarded the company a four-year grant of $1.6 million to assist in the phase II clinical development of EGEN-001, the company’s lead product. EGEN-001 is under clinical development for the treatment of advanced recurrent ovarian cancer.

EGEN, Inc. announced that the Food and Drug Administration (FDA) awarded the company a four-year grant of $1.6 million to assist in the phase II clinical development of EGEN-001, the company’s lead product. EGEN-001 is under clinical development for the treatment of advanced recurrent ovarian cancer.[1]

EGEN, Inc. is developing gene-based biopharmaceuticals that rely on proprietary delivery technologies such as TheraPlas™ (illustrated above). In preclinical studies, the application of this approach produced anti-cancer activity in the treatment of disseminated abdominal cancers, solid tumors and metastatic cancers. (Photo: EGEN, Inc.)

EGEN-001 was developed as an interleukin-12 (IL‑12) gene therapy for the treatment of disseminated epithelial ovarian cancer. It is a low concentration formulation composed of a human IL-12 plasmid formulated with a proprietary PPC delivery system. EGEN-001 is designed for intraperitoneal (IP) administration. The subsequent IL-12 protein expression is associated with an increase in immune system activity, including T-lymphocyte and natural killer (NK) cell proliferation, and cytotoxic activation and secretion of interferon gamma (IFN-g), which in turn, leads to tumor inhibition. Additionally, IL-12 inhibits angiogenesis and formation of tumor vascularization.

EGEN has successfully completed two Phase I trials of EGEN-001 in ovarian cancer patients.  In the first study, EGEN-001 was administered as monotherapy in platinum-resistant ovarian cancer patients[2] and in the second study in combination with carboplatin/docetaxel chemotherapy in platinum-sensitive ovarian cancer patients.[3] In both studies, EGEN-001 treatment resulted in good safety, biological activity and encouraging efficacy.[4-5] EGEN-001 received Orphan Drug Status from the FDA in 2005, and its first $1 million FDA orphan grant in 2005.

“This is a significant milestone and accomplishment for the company,” commented Dr. Khursheed Anwer, President and Chief Science Officer of EGEN. “We are pleased to receive this FDA support, which has been very useful in the advancement of our novel EGEN-001 product in the clinic for the treatment of recurrent ovarian cancer. The product utilizes the Company’s proprietary TheraPlas® delivery technology and is composed of interleukin-12 (IL-12) gene formulation with a biocompatible delivery polymer. IL-12 is a potent cytokine which works by enhancing the body’s immune system against cancer and inhibiting tumor blood supply.”

About EGEN, Inc.

EGEN, Inc. (EGEN), with laboratories and headquarters in Huntsville, Alabama, is a privately held biopharmaceutical company focused on developing therapeutics for the treatment of human diseases including cancer. The Company specializes in the delivery of therapeutic nucleic acids (DNA and RNAi) and proteins aimed at specific disease targets. The Company has a significant intellectual property position in synthetic carriers, their combination with DNA, and their therapeutic applications. EGEN’s research pipeline products are aimed at treatment of various cancer indications. In addition, the Company has its TheraSilence® delivery technology aimed at delivery of therapeutic siRNA for the treatment of human diseases. EGEN collaborates with outside investigators, biotech organizations, and universities on various projects in these areas.

References:

1/ A Phase II Evaluation of Intraperitoneal EGEN-001 (IL-12 Plasmid Formulated With PEG-PEI-Cholesterol Lipopolymer) in the Treatment of Persistent or Recurrent Epithelial Ovarian, Fallopian Tube or Primary Peritoneal Cancer, Clinical Trial Summary, ClinicialTrials.gov (Identifier:  NCT01118052).

2/A Phase 1, Open Label, Dose Escalation Study of the Safety, Tolerability and Preliminary Efficacy of Intraperitoneal EGEN-001 in Patients With Recurrent Epithelial Ovarian Cancer, Clinical Trial Summary, ClinicialTrials.gov (Identifier: NCT00137865).

3/A Phase 1, Open-Label, Dose Escalation Study of the Safety and Preliminary Efficacy of EGEN-001 in Combination With Carboplatin and Docetaxel in Women With Recurrent, Platinum-Sensitive, Epithelial Ovarian Cancer, Clinical Trial Summary, ClinicialTrials.gov (Identifier:  NCT00473954).

4/Kendrick JE, Matthews KS, Straughn JM, et. al.  A phase I trial of intraperitoneal EGEN-001, a novel IL-12 gene therapeutic, administered alone or in combination with chemotherapy in patients with recurrent ovarian cancer.  J Clin Oncol 26: 2008 (May 20 suppl; abstr 5572).

5/Anwar K, Barnes MN, Kelly FJ, et. al. Safety and tolerability of a novel IL-12 gene therapeutic administered in combination with carboplatin/docetaxel in patients with recurrent ovarian cancer.  J Clin Oncol 28:15s, 2010 (suppl; abstr 5045).

Source: FDA Awards EGEN, Inc. Orphan -Drug Grant for Clinical Development of EGEN-001 for Treatment of Ovarian Cancer, Press Release, EGEN, Inc., February 2, 2011.

BMS-345541 + Dasatinib Resensitizes Carboplatin-Resistant, Recurrent Ovarian Cancer Cells

Johns Hopkins medical researchers discovered through proteomic analysis that RELA and STAT5 are upregulated in carboplatin resistant ovarian cancer cells, according to a published study appearing in the June 18 edition of PLoS One. Moreover, the researchers also demonstrated that BMS-345541 (a NF-kappaB inhibitor) and dasatinib (a STAT5 inhibitor) could resensitize carboplatin-resistant, recurrent ovarian cancer cells.

Although most ovarian cancer patients are initially responsive to platinum-based chemotherapy, almost all develop recurrent chemoresistant tumors. For this reason, Johns Hopkins researchers set out to determine the scientific underpinnings of carboplatin drug resistance in ovarian cancer cells. The researchers compared the proteomes of paired primary and recurrent post-chemotherapy, high grade serous ovarian carcinomas from nine ovarian cancer patients.

As compared to the primary tumors, more than one-half of the recurrent tumors expressed higher levels of several proteins including:  CP, FN1, SYK, CD97, AIF1, WNK1, SERPINA3, APOD, URP2, STAT5B and RELA (NF-kappaB p65).  A short hairpin RNA (shRNA) is a sequence of RNA that makes a tight hairpin turn which can be used to silence gene expression through so-called “RNA interference.” Based on shRNA screening for the upregulated genes in in vitro carboplatin-resistant ovarian cancer cells, the researchers determined that simultaneous silencing of RELA and STAT5B was the most effective way to resensitize tumor cells for carboplatin treatment.

In an attempt to recreate the same results achieved with gene silencing through therapeutic drug use, the researchers used BMS-345541 (a NF-kappaB inhibitor) and dasatinib (Sprycel®)(a STAT5 inhibitor)  to significantly enhance cell sensitivity to carboplatin. The researchers also discovered that expression of RELA and STAT5B enhanced Bcl-xL promoter activity; however, treatment with BMS-345541 and dasatinib decreased such activity.

Accordingly, the researchers concluded that proteomic analysis identified RELA and STAT5 as two major proteins associated with carboplatin resistance in recurrent ovarian cancer tumors. Furthermore, the study results reveal that NF-kappaB and STAT5 inhibitors could resensitize carboplatin-resistant, recurrent ovarian cancer cells, thereby suggesting that these inhibitor drugs can be used to benefit select ovarian cancer patients.

Source: Jinawath N, Vasoontara C, Jinawath A, et. al.  Oncoproteomic analysis reveals co-upregulation of RELA and STAT5 in carboplatin resistant ovarian carcinoma. PLoS One. 2010 Jun 18;5(6):e11198.

Identifying & Overcoming Taxane Drug Resistance

Proteomics study reveals a protein that, when suppressed, makes cancers more susceptible to chemotherapy involving taxane drugs.

Taxanes, a group of cancer drugs that includes paclitaxel (Taxol®) and docetaxel (Taxotere®), have become front-line therapy for a variety of metastatic cancers. But as with many chemotherapy agents, resistance can develop, a frequent problem in breast, ovarian, prostate and other cancers. Now, cancer researchers at Children’s Hospital Boston report a protein previously unknown to be involved in taxane resistance and could potentially be targeted with drugs, making a cancer more susceptible to chemotherapy.

The researchers believe that this protein, prohibitin1, could also serve as a biomarker, allowing doctors to predict a patient’s response to chemotherapy with a simple blood test. The study was published online by the Proceedings of the National Academy of Sciences in its online early edition during the week of January 25.

Bruce Zetter, Ph.D., Charles Nowiszewski Professor of Cancer Biology, Vascular Biology Program, Department of General Surgery, Children's Hospital Boston

The study, led by Bruce Zetter, PhD, of Children’s Vascular Biology Program, used proteomics techniques to compare the proteins present in Taxol-susceptible versus Taxol-resistant human tumor cell lines. The researchers found that the resistant cell lines, but not the susceptible cell lines, had prohibitin1 on their surface. When they suppressed prohibitin1 with RNA interference techniques, the tumor cells became more susceptible to Taxol, both in cell culture and in live mice with implanted Taxol-resistant tumors.

Zetter’s lab is still investigating why having prohibitin1 on the cell surface makes a tumor cell resistant to taxanes. But in the meantime, he believes that not only could prohibitin1 be suppressed to overcome taxane resistance, but that it could also be exploited as a means of targeting chemotherapy selectively to resistant cancer cells.

“We are working to target various cancer drugs to taxane-resistant cells by attaching them to compounds that bind to prohibitin,” Zetter explains. One such compound is already known, and works well in animals to target other prohibitin-rich cells, but has yet to be tested in humans.

Suppressing prohibitin1 alone probably isn’t enough to make a cancer fully Taxol-susceptible, but could be combined with other strategies aimed at increasing taxane susceptibility, such as targeting another protein called GST Pi, the researchers say. Other mechanisms of resistance are known, but they so far haven’t been shown to present effective targets for therapy.

Zetter’s lab is also trying to develop prohibitin1 as a biomarker for taxane resistance that physicians could use in the clinic. Since it’s on the surface of the cell, Zetter believes prohibitin1 may circulate in the blood where it could easily be detected. His lab is in talks with several cancer centers to obtain serum samples from patients who did and didn’t respond to Taxol, so that prohibitin1 levels could be measured and compared.

Zetter notes that prohibitin1 could easily have been overlooked, and was found only because the team happened to look specifically at proteins in the cell membrane, rather than simply doing a whole-cell proteomic analysis.

“The interesting finding was that prohibitin was not just another over-expressed protein,” Zetter says. “It was up-regulated primarily on the cell surface. When we looked at the whole cell, the absolute amount of prohibitin wasn’t changed. Instead, prohibitin was moving from the inside of the cell to the cell surface. It had shifted from one location to another, and when it did, the tumor cells became resistant to taxanes. The fact that it moves to the cell surface also makes it easier to direct drugs to it.”

Children’s Hospital Boston has pending and issued international patents on this technology.  Nish Patel, PhD, was the study’s first author. The study was funded by a grant from the National Institutes of Health.

About Children’s Hospital Boston

Founded in 1869 as a 20-bed hospital for children, Children’s Hospital Boston today is one of the nation’s leading pediatric medical centers, the primary pediatric teaching hospital of Harvard Medical School, and the largest provider of health care to Massachusetts children. In addition to 396 pediatric and adolescent inpatient beds and more than 100 outpatient programs, Children’s houses the world’s largest research enterprise based at a pediatric medical center, where its discoveries benefit both children and adults. More than 500 scientists, including eight members of the National Academy of Sciences, 11 members of the Institute of Medicine and 13 members of the Howard Hughes Medical Institute comprise Children’s research community. For more information about the hospital visit: www.childrenshospital.org/newsroom.

Sources:

A Potential Treatment For Ovarian Cancer – Claudin-3 Gene Silencing Using Small Interfering RNA

“… Ovarian tumors highly express two proteins, claudin-3 and -4. These proteins are associated with both an increase is cellular motility and survival of ovarian tumor cells.  Claudin-3 is also over expressed in breast and prostate tumors. This new therapy is targeting claudin-3 (CLDN3) using small interfering RNA (siRNA). More specifically, this team has developed a nanoparticulate, lipid-like delivery system for intraperitoneal delivery of siRNA to ovarian tumors. Tests of the therapeutic efficacy of CLDN3 siRNA in three different mouse models showed a significant reduction in tumor growth.  Additionally, these mice showed no ill side effects of the CLDN3 siRNA treatment. …”

“PAPER REVEALS POTENTIAL NEW TREATMENT FOR OVARIAN CANCER

Wynnewood, PA, February 9, 2009 – – – – – Ovarian cancer is the fourth most common cancer in women and has the highest mortality rate for gynecologic cancers because it is often diagnosed at an advanced stage. New effective therapies for the treatment of advanced stage ovarian cancer are urgently needed.

Today, a paper published in the Proceedings of the National Academy of Sciences (PNAS) by Dr. Janet Sawicki, Professor at the Lankenau Institute for Medical Research (LIMR), a team headed by Daniel G. Anderson, Ph.D. and Robert Langer, Sc.D. of the David H. Koch Institute for Integrative Cancer Research at the Massachusetts Institute of Technology (MIT) and David Bumcrot, Director of Research at Alnylam Pharmaceuticals, shows that a new therapy suppresses ovarian tumor growth and metastasis in preclinical studies.

Ovarian tumors highly express two proteins, claudin-3 and -4. These proteins are associated with both an increase is cellular motility and survival of ovarian tumor cells.  Claudin-3 is also over expressed in breast and prostate tumors. This new therapy is targeting claudin-3 (CLDN3) using small interfering RNA (siRNA). More specifically, this team has developed a nanoparticulate, lipid-like delivery system for intraperitoneal delivery of siRNA to ovarian tumors. Tests of the therapeutic efficacy of CLDN3 siRNA in three different mouse models showed a significant reduction in tumor growth.  Additionally, these mice showed no ill side effects of the CLDN3 siRNA treatment.

‘We are excited by the preclinical performance of these formulations, and are hopeful that the lipidoid-siRNA nanoparticulates developed here may enable new genetic therapies for ovarian cancer,’ said Anderson.

‘These findings offer new hope for a therapeutic treatment option for individuals with metastatic ovarian cancer and potentially other types of cancers that over-express CLDN3’, states Dr. Janet Sawicki.  ‘Our next step is to begin Phase I clinical trials to test for safety with hopes to bring this treatment to the patient in the next few years.’

This research was made possible through funding from the National Institutes of Health (NIH), the Sandy Rollman Ovarian Cancer Foundation of Havertown, PA, and Wawa.

Lankenau Institute for Medical Research
Founded in 1927, the Lankenau Institute for Medical Research (LIMR) is an independent, nonprofit biomedical research center located in suburban Philadelphia on the campus of the Lankenau Hospital. As part of the Main Line Health System, LIMR is one of the few freestanding, hospital-associated medical research centers in the nation.  The faculty and staff at the Institute are dedicated to advancing an understanding of the causes of cancer and heart disease. They use this information to help improve diagnosis and treatment of these diseases as well as find ways to prevent them. They are also committed to extending the boundaries of human health and well-being through technology transfer and education directed at the scientific, clinical, business and lay public communities. For more information visit: http://www.limr.org.

David H. Koch Institute for Integrative Cancer Research at MIT
Launched by MIT in 2008, the David H. Koch Institute for Integrative Cancer Research (KI) both transforms and transcends the Center for Cancer Research (CCR). CCR was founded in 1974 by Nobel Laureate and MIT Professor Salvador Luria, CCR has made enormous contributions to the field of cancer research. The Koch is one of only seven National Cancer Institute-designated basic research centers in the US and is comprised of faculty that have earned the most prestigious national and international science honors including the Nobel Prize and the National Medal of Science. For more information visit: web.mit.edu/ki/index.html.

Alnylam Pharmaceuticals, Inc.
Alnylam Pharmaceuticals, a leader in RNAi therapeutics, is a biopharmaceutical company developing novel therapeutics based on a breakthrough in biology known as RNA interference, or RNAi; a discovery that enables the creation of a broad new class of human therapeutics. Using RNAi, Alnylam has built a product engine to develop a deep pipeline of drug products to treat a wide array of important diseases. For more information visit: http://www.alnylam.com

Contact: Tava Shanchuk
Phone: (610) 645-3429
E-mail: shanchukt@mlhs.org”

RNA Interference Primer – Alnylam Pharmaceuticals

Quoted Source Paper Reveals Potential New Treatment for Ovarian Cancer, Press Release, Lankenau Institute for Medical Research, Feb. 9, 2009.

Primary CitationClaudin-3 gene silencing with siRNA suppresses ovarian tumor growth and metastasis; Huang YH, Bao Y, Peng W et. al., Proc Natl Acad Sci U S A. 2009 Feb 10. [Epub ahead of print]

Additional Resources:

Liposomal siRNA — Genetic On/Off Switches That Target Ovarian Cancer Through the Trojan Horse Effect

Use of Liposomal siRNA to Target Ovarian Cancer Protein Known as “Interleukin-8 (IL-8)”

“A protein that stimulates blood vessel growth worsens ovarian cancer, but its production can be stifled by a tiny bit of RNA wrapped in a fatty nanoparticle, a research team led by scientists at The University of Texas M. D. Anderson Cancer Center reports in the Journal of the National Cancer Institute.

The protein IL-8 is a potential therapeutic target in ovarian cancer,’ said senior author Anil Sood, M.D., professor in the M. D. Anderson Departments of Gynecologic Oncology and Cancer Biology.

The paper demonstrates that high IL-8 expression in tumors is associated with advanced tumor stage and earlier death for ovarian cancer patients. Lab experiments and research in a mouse model show that short interfering RNA (siRNA) can cut IL-8 expression, reducing tumor size by attacking its blood supply.

‘This comprehensive analysis – with human data, animal data and lab experiments to highlight the molecular mechanisms involved – helps us develop the new targets needed for a more effective approach against ovarian cancer,’ Sood said.

Interleukin-8 is overexpressed in many types of cancer and has previously been shown to promote tumor growth, new blood vessel growth known as angiogenesis, and metastasis, the spread of cancer to other organs. ‘In the long run, this research will have applications in other cancers as well,’ Sood said.

His research focuses on ovarian cancer, for example, while senior co-author Menashe Bar-Eli, Ph.D., professor in M. D. Anderson’s Department of Cancer Biology, examines IL-8’s role in melanoma.

Impact on survival

Ovarian cancer is often detected in late stages. Initial treatment includes surgery and taxane- or platinum-based chemotherapy regimens that keep the cancer at bay for a time in most patients. Recurrence is common and often lethal.

To examine IL-8’s role in ovarian cancer, the researchers analyzed tumors from 102 patients diagnosed and treated between 1988 and 2006 at M. D. Anderson and the University of Iowa. Of those, 43 had tumors with high levels of IL-8 and 59 had low levels. The median survival of those with high IL-8 tumors was 1.62 years, compared with 3.79 years for those with low expression of the protein.

All 43 tumors with high expression of IL-8 were of high grade and 42 of 43 were advanced, either stage III or IV tumors. By comparison, 10 of 59 tumors with low IL-8 expression were early stage tumors and six were of low grade.

Shrinking tumors

Genes transcribe single strands of RNA that in turn are ‘read’ by ribosomes to produce proteins. siRNAs are short, double-stranded bits of RNA capable of halting that process. The team confirmed in a lab experiment that a specific siRNA silences IL-8 and then tested it against two lines of ovarian cancer in a mouse model.

Sood, Gabriel Lopez-Berestein, M.D., professor in M. D. Anderson’s Department of Experimental Therapeutics, and colleagues are building an arsenal of siRNAs capable of silencing genes that produce cancer-promoting proteins. They packaged siRNA that stymies IL-8 into a small ball of fat known as a liposome, a combination they developed to overcome a problem – siRNA is hard to deliver to tumors.

Tumors shrank by a median of 32 percent and 52 percent in the two cancer lines among mice that received injections of the IL-8 siRNA liposome compared to those receiving control siRNA or empty liposomes.

Mice that got both the IL-8 siRNA plus the taxane-based chemotherapy drug docetaxel [Taxotere®] had median tumor weight reduction of 90 percent and 98 percent in the two cell lines. Mice with control siRNA plus docetaxel saw reductions of 67 and 84 percent.

Finally, they tested the approach in mice with an ovarian cancer cell line known to be resistant to taxane-based drugs such as docetaxel. IL-8 siRNA alone reduced the size of these tumors by 47 percent, and when combined with docetaxel reduced tumor size by 77 percent, suggesting that the combination re-sensitizes a resistant tumor to taxanes.

The team gauged the impact of IL-8 siRNA on tumor blood supply by measuring the density of blood vessels in the tumor. The IL-8 siRNA alone reduced blood vessel density by 34 percent and 39 percent in two cancer lines.

Clinical Prospects

‘These are encouraging results. We want to move one of our siRNA agents into the clinic to test its potential for therapy,’ Sood said, ‘and then in the longer term, we’ll consider moving additional siRNA agents into the clinical arena.’

The IL-8 siRNA liposome is the third developed by Sood’s and Lopez-Berestein’s team. Two others target the oncoproteins FAK and EphA2. The EphA2 siRNA liposome is closest to Phase I clinical trial, with required toxicology studies nearly complete. A clinical trial could begin within a year.

Methods used to inject siRNA in high volumes for research purposes are impractical for human therapy. Sood and Lopez-Berestein developed the liposomal approach to ensure that the siRNA reaches the cell intact so it can silence the targeted gene. Their research has shown that the liposome penetrates deeply into cells to deliver its siRNA.

Research reported in JNCI was funded by grants from the National Cancer Institute of the National Institutes of Health, including M. D. Anderson’s Specialized Program of Research Excellence in Ovarian Cancer; the Ovarian Cancer Research Fund, Inc.; and the Zarrow Foundation.”

Quoted Source: [“Researchers Identify and Shut Down Protein that Fuels Ovarian Cancer, M. D. Anderson-led team pinpoints blood vessel promoter’s role and targets it with siRNA,” M.D Anderson News Release, dated February 26, 2008]. See also “Effect of Interleukin-8 Gene Silencing With Liposome-Encapsulated Small Interfering RNA on Ovarian Cancer Cell Growth;” Merritt,W.M., Lin,Y.G., Spannuth,W.A., Fletcher,M.S., Kamat,A.A., Han,L.Y., Landen,C.N., Jennings,M., Geest,K., Langley,R.R., Villares,G., Sanguino,A., Lutgendorf,S.K., Lopez-Berestein,G., Bar-Eli,M.M., Sood, A.K.; Journal of the National Cancer Institute 2008 100(5):359-372.

Use of Liposomal siRNA to Target Ovarian Cancer Protein Known as “Focal-Adhesion Kinase (FAK)”

Recent work reported in October 2006 by Dr. Anil Sood at M.D. Anderson involved the use of a targeted “siRNAliposome in mice to identify and correct defective ovarian cancer cells. M. D. Anderson researchers used siRNA (which acts as a genetic “on/off” switch) to target an ovarian cancer protein known as focal-adhesion kinase (FAK), which is present in all ovarian cancer cells. FAK helps ovarian cancer cells survive and spread. The siRNA was rolled into a liposome – a ball of fat so small that its dimensions are measured in nanometers (billionths of a meter). Because of their tiny size, these liposomes have no problem traveling through the blood supply into cells that make up tumors through the so-called “Trojan Horse” effect. To test how well it worked, mice that were implanted with human ovarian tumors were given injections of the therapy for three to five weeks. The mice ovarian tumors experienced a 44% to 72% reduction in weight. Adding chemotherapy to the treatment boosted tumor weight reduction to the 94% to 98% range. The next step for the FAK siRNA liposome is testing for toxicity prior to studies in human patients.

Source: [ “Novel Therapy Shrinks Ovarian Tumors in Mice, Genetic Fragments Turn Off Cancer Growth Switch,” Cancer Newsline, October 2006, M.D. Anderson Cancer Center, University of Texas.]

Use of Liposomal siRNA to Target the Ovarian Cancer Kinase Known as “EphA2”

In an earlier in vitro studies, Anil Sood, M.D. et. al. demonstrated that when EphA2-targeting siRNA was combined with paclitaxel [Taxol®], tumor growth was dramatically reduced compared with treatment with paclitaxel and a nonsilencing siRNA. These studies show the feasibility of siRNA as a clinically applicable therapeutic modality.

Source: [“Therapeutic EphA2 Gene Targeting In vivo Using Neutral Liposomal Small Interfering RNA Delivery;” Landen,C.N., Chavez-Reyes, A., Bucana, C., Schmandt, R., T. Deavers, M., Lopez-Berestein, G. and Sood, A.K., The University of Texas M.D. Anderson Cancer Center, Houston, Texas; Cancer Research 65, 6910-6918, August 1, 2005.

Comment: The ultimate use of siRNA to treat ovarian cancer in humans holds future promise. Ovarian cancer survivors should monitor the development of this liposomal siRNA form of treatment because its use in human clinical trials could occur in the near future, assuming that pre-clinical trial toxicity tests demonstrate safety. Anil Sood, M.D. has developed the liposomal siRNA for IL-8, FAK, and EphA2. It is reported that human clinical trials with respect to the EphA2 siRNA treatment will begin within 12 months.