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.

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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.

Disarming Specialized Stem Cells Might Combat Ovarian Cancer

Eliminating cancer stem cells (CSCs) within a tumor could hold the key to successful treatments for ovarian cancer, which has been notoriously difficult to detect and treat, according to new findings published this week in the journal Oncogene by Yale School of Medicine researchers.

Eliminating cancer stem cells (CSCs) within a tumor could hold the key to successful treatments for ovarian cancer, which has been notoriously difficult to detect and treat, according to new findings published this week in the journal Oncogene by Yale School of Medicine researchers.

“We found that stopping the expression of two genesLin28 and Oct4—reduces ovarian cancer cell growth and survival,” said Yingqun Huang, M.D., Ph.D., assistant professor in the Department of Obstetrics, Gynecology & Reproductive Sciences at Yale School of Medicine.

Ovarian cancer is challenging to treat because it tends to recur frequently and develop resistance to treatment. The poor outcome for women with ovarian cancer is associated with subtle and nonspecific symptoms—earning it the moniker the “disease that whispers.”

“This recurrence and drug resistance may be due to the presence of CSCs within the tumors that have the capacity to reproduce and to differentiate into non-CSC tumor cells that repopulate the tumor mass,” said Huang, who is a member of Yale Stem Cell Center and Yale Cancer Center. “Eliminating these CSCs may be key to successful treatments.”

While in the process of studying the functions of stem cell proteins in human embryonic stem cells, Huang and her colleagues unexpectedly discovered that a sub-population of ovarian cancer cells express stem cell proteins Lin28 and Oct4. They also found that the two proteins appear to act together in ovarian cancer tissue cells to produce more advanced tumors. Inhibiting their combined expression led to a significant decrease in the growth and survival of cancer cells. A larger-scale ovarian cancer study is currently underway to confirm the significance of the findings.

Genetic researchers prevent genes from functioning — a process commonly referred to as “knocking down” the gene — by inserting small interfering RNA (siRNA) molecules into the cells. Next, the research team will examine the effect of siRNA in ovarian cancer cells in the lab, and test the technique on mice. If successful, human clinical trials would follow. Treatment on cancer patients could occur within 10 years, Huang said.

“We hope we will soon be able to apply this new information to improve outcomes, perhaps by developing better diagnostic markers and treatment strategies that may be useful in customizing treatment for ovarian cancer patients,” said Huang.

The study was supported by Connecticut Innovations, the Fannie E. Rippel Foundation and the National Cancer Institute.

Other Yale authors on the study included Nita Maihle, Ph.D., and Shuping Peng.

Sources:

Trojan Horse* For Ovarian Cancer–Nanoparticles Turn Immune System Soldiers Against Tumor Cells

In a feat of trickery, Dartmouth Medical School immunologists have devised a Trojan horse to help overcome ovarian cancer, unleashing a surprise killer in the surroundings of a hard-to-treat tumor. Using nanoparticles–ultra small bits– the team has reprogrammed a protective cell that ovarian cancers have corrupted to feed their growth, turning the cells back from tumor friend to foe. Their research, published online July 13 for the August Journal of Clinical Investigation, offers a promising approach to orchestrate an attack against a cancer whose survival rates have barely budged over the last three decades …

Hanover, N.H.—In a feat of trickery, Dartmouth Medical School immunologists have devised a Trojan horse to help overcome ovarian cancer, unleashing a surprise killer in the surroundings of a hard-to-treat tumor.

Using nanoparticles–ultra small bits– the team has reprogrammed a protective cell that ovarian cancers have corrupted to feed their growth, turning the cells back from tumor friend to foe. Their research, published online July 13 for the August Journal of Clinical Investigation, offers a promising approach to orchestrate an attack against a cancer whose survival rates have barely budged over the last three decades.

Dr. Jose Conejo-Garcia (right) with graduate student Juan Cubillos-Ruiz  (Photo Source:  Dartmouth Medical School News Release,

Dr. Jose Conejo-Garcia (right) with graduate student Juan Cubillos-Ruiz (Photo Source: Dartmouth Medical School News Release, 13 Jul. 09)

“We have modulated elements of the tumor microenvironment that are not cancer cells, reversing their role as accomplices in tumor growth to attackers that boost responses against the tumor,” said Dr. Jose Conejo-Garcia, assistant professor of microbiology and immunology and of medicine, who led the research. “The cooperating cells hit by the particles return to fighters that immediately kill tumor cells.”

The study, in mice with established ovarian tumors, involves a polymer now in clinical trials for other tumors. The polymer interacts with a receptor that senses danger to activate cells that trigger an inflammatory immune response.

The Dartmouth work focuses on dendritic cells–an immune cell particularly abundant in the ovarian cancer environment. It does take direct aim at tumor cells, so it could be an amenable adjunct to other current therapies.

“The cooperating cells hit by the particles return to fighters that immediately kill tumor cells.” —Dr. Jose Conejo-Garcia

“That’s the beautiful part of story–people usually inject these nanoparticles to target tumor cells. But we found that these dendritic cells that are commonly present in ovarian cancer were preferentially and avidly engulfing the nanoparticles. We couldn’t find any tumor cells taking up the nanoparticles, only the dendritic cells residing in the tumor,” explained Juan R. Cubillos-Ruiz, graduate student and first author.

Dendritic cells are phagocytes–the soldiers of the immune system that gobble up bacteria and other pathogens, but ovarian cancer has co-opted them for its own use, he continued. “So we were trying to restore the attributes of these dendritic cells–the good guys; they become Trojan horses.”

Cancer is more than tumor cells; many other circulating cells including the dendritic phagocytes converge to occupy nearby space. The dendritic cells around ovarian cancer scoop up the nanocomplexes, composed of a polymer and small interfering RNA (siRNA) molecules to silence their immunosuppressive activity.

Nanoparticle incorporation transforms them from an immunosuppressive to an immunostimulatory cell type at tumor locations, provoking anti-tumor responses and also directly killing tumor cells. The effect is particularly striking with an siRNA designed to silence the gene responsible for making an immune protein called PD-L.

The new findings also raise a warning flag about the use of gene silencing complexes in cancer treatment. Inflammation is a helpful immune response, but the researchers urge caution when using compounds that can enhance inflammation in a patient already weakened by cancer.

Ovarian cancer, which claims an estimated 15,000 US lives a year, is an accessible disease for nanoparticle delivery, according to the investigators. Instead of systemic administration, complexes can be put directly into the peritoneal cavity where the phagocytes take them up.

Samples of human ovarian cancer cells show similar responses to nanoparticle stimulation, the researchers observed, suggesting feasibility in the clinical setting. It could be part of a “multimodal approach,” against ovarian cancer, said Conejo-Garcia also a member of the Dartmouth’s Norris Cotton Cancer Center. “The prevailing treatment is surgical debulking, followed by chemotherapy. Our findings could complement those because they target not the tumor cells themselves, but different cells present around the tumor.”

Co-authors are Xavier Engle, Uciane K. Scarlett, Diana Martinez, Amorette Barber, Raul Elgueta, Li Wang, Yolanda Nesbeth and Charles Sentman of Dartmouth; Yvon Durant of University of New Hampshire, Andrew T Gewirtz of Emory, and Ross Kedl of University of Colorado.

The work was supported by grants from the National Institutes of Health, including the National Cancer Institute and National Center for Research Resources, a Liz Tilberis Award from the Ovarian Cancer Research Fund, and the Norris Cotton Cancer Center Nanotechnology Group Award.

Read an interview of Jose Conejo – Garcia with the Ovarian Cancer Research Fund.

Source: Trojan Horse for Ovarian Cancer–Nanoparticles Turn Immune System Soldiers against Tumor Cells, News Release, Dartmouth Medical School, July 13, 2009 (summarizing Cubillos-Ruiz JR, Engle X, Scarlett UK, et. al. Polyethylenimine-based siRNA nanocomplexes reprogram tumor-associated dendritic cells via TLR5 to elicit therapeutic antitumor immunity. J Clin Invest. 2009 Aug 3;119(8):2231-2244. doi: 10.1172/JCI37716. Epub 2009 Jul 13).

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* The Trojan Horse was a tale from the Trojan War, as told in Virgil’s Latin epic poem The Aeneid. The events in this story from the Bronze Age took place after Homer’s Iliad, and before Homer’s Odyssey. It was the strategy that allowed the Greeks finally to enter the city of Troy and end the conflict. In the best-known version, after a fruitless 10-year siege of Troy, the Greeks built a huge horse figure and hid a select force of men within it. The Greeks left the Horse at the city gates of Troy and pretended to sail away.  Thereafter, the Trojans pulled the Horse into their city as a victory trophy. That night the Greek force crept out of the Horse and opened the gates for the returning Greek army, which had sailed back to Troy under cover of night. The Greek army entered and destroyed the city, decisively ending the war. A “Trojan Horse” has come to mean any trick that causes a target to invite a foe into a securely protected bastion or place.

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]

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M.D. Anderson Identifies TG2 As a Potential Target in Chemo-Resistant Ovarian Cancer

“Scientists from The University of Texas M. D. Anderson Cancer Center have found overexpression of tissue type transglutaminase (TG2) in ovarian cancer is associated with increased tumor cell growth and adhesion, resistance to chemotherapy and lower overall survival rates. When researchers targeted and silenced TG2 in animal models, cancer progression was reversed, suggesting the protein may also provide a novel therapeutic approach for late-stage ovarian cancer.”

“Scientists from The University of Texas M. D. Anderson Cancer Center have found overexpression of tissue type transglutaminase (TG2) in ovarian cancer is associated with increased tumor cell growth and adhesion, resistance to chemotherapy and lower overall survival rates. When researchers targeted and silenced TG2 in animal models, cancer progression was reversed, suggesting the protein may also provide a novel therapeutic approach for late-stage ovarian cancer.

These findings in the July 15th issue of Cancer Research by a team of researchers led by Anil K. Sood, M.D., professor in the Departments of Gynecologic Oncology and Cancer Biology, and Kapil Mehta, Ph.D., professor in the Department of Experimental Therapeutics at M. D. Anderson, are among the first to explore TG2’s functionality in ovarian cancer.

‘TG2 appears to fuel different types of cancer through multiple molecular pathways, making it an important therapeutic target,’ said Mehta, whose lab also has connected TG2 overexpression to drug-resistant and metastatic melanoma, breast cancer and pancreatic cancer.

‘Drug resistance and metastasis are major impediments to the successful treatment of ovarian cancer and until now we had little information about the role TG2 played in ovarian cancer,’ Sood said. ‘We began to see its story unfold as we translated this data from tissue samples to cell lines to animal models.’

The American Cancer Society estimates 15,000 U.S. women will die from ovarian cancer this year. Most patients present with advanced stage disease that has spread beyond the primary tumor site. More than 70 percent of ovarian cancer patients will suffer a recurrence and eventually succumb to the disease.

Higher TG2, lower survival

The study, which examined 93 ovarian cancer samples of ranging stages, found that high levels of TG2 corresponded with significantly lower patient survival than those with low levels of TG2. Sixty-nine percent of high-stage ovarian cancers overexpressed TG2 compared with 30 percent of low-stage cancers. In-depth analysis demonstrated that tumors which overexpressed the protein tended to have an increased ability to invade healthy tissue and to survive or avoid the affects of chemotherapy.

‘From this investigation it became clear that TG2 activates the survival pathway p13K/Akt in these tumors, explaining the adverse, resistant behavior we observed on a molecular level,’ said Sood. ‘We then focused on whether silencing TG2 would block these effects.’

Researchers shut off TG2 with a small interfering RNA strand (TG2 siRNA) targeted to the protein, reducing the ability of the tumor cells to invade and killing them through programmed cell death, or apoptosis. ‘When exposed to this potent targeted therapy, ovarian cancer cells greatly reduced cancer cell proliferation and blood vessel development, while increasing apoptosis,’ said Sood.

Mouse model studies of chemotherapy-sensitive and chemotherapy-resistant models showed considerable antitumor activity both with TG2 siRNA alone and in combination with docetaxel chemotherapy. The combination therapy of TG2 siRNA with docetaxel reduced tumor weight by 86 percent, proving to have the greatest efficacy compared to control groups or those without chemotherapy.

‘While it remains to be seen if these results will translate in humans, looking ahead long term, it will be an attractive option against advanced ovarian cancer,’ said co-author Gabriel Lopez-Berestein, M.D. professor in the Department of Experimental Therapeutics at M. D. Anderson.

TG2 fuels pancreatic cancer differently

Sood and Lopez-Berestein, have developed siRNA therapy by packaging the gene-silencing strips of RNA in a fatty nanoparticle called a liposome and delivering it intravenously. TG2 is the third protein they have targeted in preclinical research. Sood and Mehta are moving TG2 siRNA toward Phase I clinical trials for ovarian and pancreatic cancers.

TG2 acts through different pathways in other types of cancer, Mehta noted. For example, TG2 overexpression causes the degradation of the tumor-suppressing protein PTEN in pancreatic cancer, Mehta and colleagues reported in Clinical Cancer Research in April. With PTEN out of the picture, pancreatic cancer is protected from a separate type of cell death called autophagy. In a separate paper, they showed that silencing TG2 with the siRNA liposome reduced tumor size, slowed metastasis and enhanced the effect of gemcitabine chemotherapy.

‘This aberrant protein is doing so many different things, you would have to develop a small-molecule drug to block each function,’ Mehta said. ‘Liposomal siRNA is exciting because it takes out TG2 completely, blocking everything that it does.’

Research was funded by grants from the National Cancer Institute, including M. D. Anderson’s Specialized Program in Research Excellence in Ovarian Cancer grant, a program project development grant from the Ovarian Cancer Research Fund, Inc., and the Zarrow Foundation.

In addition to Sood, Mehta and Lopez-Berestein, authors include Jee Young Hwang, M.D., Lingegowda S. Mangala, Ph.D., co-first authors, and Yvonne G. Lin, M.D., William M. Merritt, M.D., Whitney A. Spannuth, M.D., Alpa M. Nick, M.D., Derek J. Fiterman, M.D., and Robert L. Coleman, M.D., all of M. D. Anderson’s Department of Gynecologic Oncology; Jansina Y. Fok, also a co-first author, and Pablo E. Vivas-Mejia, Ph.D., both of the Department of Experimental Therapeutics; and Michael T. Deavers, M.D., of M. D. Anderson’s Department of Pathology. Hwang is also with the Department of Obstetrics and Gynecology, Dongguk University of College of Medicine, Kyung-ju, Korea. 07/15/08”

Quoted Source: TG2 Identified as Potential Target in Chemo-Resistant Ovarian Cancer – M. D. Anderson team silences protein with siRNA, implicates TG2 in fourth cancer, The University of Texas, M.D. Anderson Cancer Center News Release, July 15, 2008 (summarizing the findings of Clinical and biological significance of tissue transglutaminase in ovarian carcinoma; Sood, AK et. al,  Cancer Res. 2008 Jul 15;68(14):5849-58.)

Additional Information: