Blunting the Activity of Protein Abcc10 May Help Counter Taxane Drug Resistance In Ovarian Cancer

New findings by Fox Chase Cancer Center researchers identify one protein, Abcc10, as being intimately involved in resistance to certain drugs used to treat breast, ovarian, lung, and other cancers. The results suggest that blunting the activity of Abcc10 might help counter resistance and extend the effectiveness of these anticancer drugs.

Today’s anticancer drugs often work wonders against malignancies, but sometimes tumors become resistant to the effects of such drugs, and treatment fails. Medical researchers would like to find ways of counteracting such resistance, but first they must understand why and how it happens. New findings by Fox Chase Cancer Center researchers identify one protein, Abcc10 (ATP-binding cassette transporter 10) (also known as multidrug resistance protein 7 (Mrp7)), as being intimately involved in resistance to certain drugs used to treat breast, ovarian, lung, and other cancers. The results suggest that blunting the activity of Abcc10 might help counter resistance and extend the effectiveness of these anticancer drugs.

The findings appear in the May 15, 2011 issue of the journal Cancer Research.

Elizabeth A. Hopper-Borge, Ph.D., Assistant Professor, Fox Chase Cancer Center, Philadelphia, Pennsylvania

In earlier work, Elizabeth A. Hopper-Borge, Ph.D., an assistant professor at Fox Chase, showed that Abcc10 confers resistance to a number of anticancer agents, particularly taxanes, which include paclitaxel (Taxol) and docetaxel (Taxotere). These drugs––originally derived from the Pacific yew tree––work by disrupting cell division, thus arresting the growth and spread of tumors. The initial finding that Abcc10, a member of a ubiquitous family of proteins called ATP-binding cassette transporters, thwarts taxanes’ anti-tumor activity was something of a surprise, says Hopper-Borge, because none of the other family members seem to have that ability.

In the new research, Hopper-Borge and colleagues wanted to further explore, in both cultured cells and mice, the role of Abcc10. They developed a “knockout” mouse, in which the gene that codes for Abcc10 was missing, or knocked out. These mice appeared normal and healthy in every other respect, suggesting that Abcc10 is not essential for overall health and survival.

The researchers isolated cells from the knockout mice and tested the cells’ reactions to taxanes and two other anticancer drugs, vincristine and Ara-C. Compared to cells from normal mice that still possessed the gene for Abcc10, the knockout mouse cells were much more sensitive to the drugs.

Abcc10 and its ilk work by pumping drugs out of cells, so one might expect to see the drugs accumulating in cells that lack Abcc10, and that’s exactly what Hopper-Borge’s group saw. It had been suggested that other proteins might take over for Abcc10 if that protein were knocked out, but the researchers found no evidence suggesting that had happened.

Next, the research team studied the effects of one particular taxane, paclitaxel, on mice and found that the knockout mice were more sensitive to the drug, as reflected in body weight, white blood cell count, and ability to survive escalating doses of the drug.

“After seeing the effects on white blood cells, we decided to look at the tissue types that produce white blood cells to see if we could actually see differences there,” says Hopper-Borge. As expected, knockout mice treated with paclitaxel had smaller spleens and thymus glands and underdeveloped bone marrow, compared to normal mice treated with the same drug.

The results provide the first evidence from living organisms that Abcc10 is a cell’s built-in protection against the effects of powerful drugs, and raises the possibility of using Abcc10 inhibitors to break down that resistance and sensitize tumor cells to anticancer agents. The fact that mice lacking the protein have no obvious health problems is encouraging, suggesting that Abcc10 inhibitors could be used in human patients without causing side effects that might be expected to result from interfering with the pump’s normal functions.

Several Abcc10 inhibitors already have been identified, but they also inhibit other cellular transporters, which could have deleterious effects. For that reason, Hopper-Borge thinks the best approach may be developing inhibitors that work only in tumor cells or coming up with compounds that modulate, rather than completely inhibit the protein’s activity.

But using such treatments in patients is still far in the future, she emphasizes.

“I’d like to stress that we did this work in a mouse model,” Hopper-Borge says. “Our results so far suggest that this protein may be a clinically relevant target, but we need to do more studies to find out for sure.”

Co-authors on the study include Timothy Churchill, Chelsy Paulose, Emmanuelle Nicolas, Joely D. Jacobs, Olivia Ngo, Andres J. Klein-Szanto and Martin G. Belinsky of Fox Chase; Yehong Kuang of Central South University, Changsha, China; Alex Grinberg and Heiner Westphal of the National Institute of Child Health and Human Development; and Gary D. Kruh of the University of Illinois at Chicago.

The research was supported by the National Institutes of Health.

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The Cancer Biomarker Conundrum: Too Many False Discoveries

The boom in cancer [including ovarian] biomarker investments over the past 25 years has not translated into major clinical success. The reasons for biomarker failures include problems with study design and interpretation, as well as statistical deficiencies, according to an article published online August 12 in The Journal of the National Cancer Institute.

The boom in cancer [including ovarian] biomarker investments over the past 25 years has not translated into major clinical success. The reasons for biomarker failures include problems with study design and interpretation, as well as statistical deficiencies, according to an article published online August 12 in The Journal of the National Cancer Institute.

The National Institutes of Health defines a biomarker as “a characteristic that is objectively measured and evaluated as an indicator of normal biologic processes, pathogenic processes, or pharmacologic responses to a therapeutic intervention.” In the past decade, there have been numerous biomarker discoveries, but most initially promising biomarkers have not been validated for clinical use.

Eleftherios P. Diamandis, M.D., Ph.D., Head, Section of Clinical Biochemistry, Department of Pathology and Laboratory Medicine, Mount Sinai Hospital, Toronto, Ontario, Canada

To understand why so-called biomarker “breakthroughs” have not made it to the clinic, Eleftherios P. Diamandis, M.D., Ph.D., professor of pathology and laboratory medicine at Mount Sinai Hospital in Toronto and associate scientist at the Samuel Lunenfeld Research Institute of Mount Sinai Hospital, reviewed some biomarkers initially hailed as breakthroughs and their subsequent failings.

Diamandis first describes the requirements for biomarkers to be approved for clinical use: A biomarker must be released into circulation in easily detectable amounts by a small asymptomatic tumor or its micro-environment; and it should preferably be specific for the tissue of origin. Also, if the biomarker is affected by a non-cancer disease, its utility for cancer detection may be compromised. For example, the prostate-specific antigen (PSA) biomarker, which is used to detect prostate cancer, is also elevated in benign prostatic hyperplasia.

Diamandis looks at seven biomarkers that have emerged in the past 25 years, all of which were considered promising when they were first described. These include nuclear magnetic resonance of serum for cancer diagnosis; lysophosphatidic acid for ovarian cancer; four– and six-parameter diagnostic panels for ovarian cancer; osteopontin for ovarian cancer; early prostate cancer antigen-2 (EPCA-2) for prostate cancer detection; proteomic profiling of serum by mass spectrometry for ovarian cancer diagnosis; and peptidomic patterns for cancer diagnosis. Problems ranged from inappropriate statistical analysis to biases in case patient and control subject selection. For example, the problems with EPCA-2 included reporting values that were beyond the detection limit of the assay and using inappropriate reagents to test EPCA-2, such as solid surfaces coated with undiluted serum.

Diamandis concludes that “problems with pre-analytical, analytical, and post-analytical study design could lead to the generation of data that could be highly misleading.”

Sources:

The Cancer Biomarker Conundrum: Too Many False Discoveries, Journal of the National Cancer Institute Advance Access,  published on August 12, 2010, DOI 10.1093/jnci/djq335.

Eleftherios P. Diamandis. Cancer Biomarkers: Can We Turn Recent Failures into Success? Commentary, Journal of the National Cancer Institute Advance Access published on August 12, 2010, DOI 10.1093/jnci/djq306.

Expression of Proteins Linked to Poor Outcome in Women with Ovarian Cancer

Scientists have established the presence of certain proteins in ovarian cancer tissues and have linked these proteins to poor survival rates in women with advanced stages of the disease.

Christina M. Annunziata, M.D., Ph.D., Assistant Clinical Investigator, Medical Oncology Branch & Affiliates, Molecular Signaling Section, National Cancer Institute

NF-kB Signaling Pathway

Scientists have established the presence of certain proteins in ovarian cancer tissues and have linked these proteins to poor survival rates in women with advanced stages of the disease. The study, led by scientists at the National Cancer Institute (NCI), part of the National Institutes of Health, appears in Cancer online, April 19, 2010.

The proteins in question belong to the nuclear factor kappa Beta (NF-kB) family. NF-kB controls many processes within the cell including cell survival and proliferation, inflammation, immune responses, and cellular responses to stress.

“This study sheds light on the distinctive genetic features of the NF-kB pathway and may provide targets for the development of novel therapies for ovarian cancer,” said lead investigator, Christina M. Annunziata, M.D., Ph.D., associate clinical investigator, Medical Oncology Branch.

Abnormalities in NF-kB signaling have been found in several types of cancer, including ovarian cancer, but the mechanism and importance of such alterations in ovarian cancer was not defined. To address these knowledge gaps, the research team investigated the expression of NF-kB-related proteins in the cells of tumor tissue obtained at surgery from 33 previously untreated women who were newly diagnosed with advanced epithelial ovarian cancer. The patients had similar stage (all late stage), grade, and type of disease. All patients were treated with a three-drug regimen of standard chemotherapy agents in an NCI clinical trial that was conducted at the NIH Clinical Research Center.

To assess NF-kB family members and associated proteins in ovarian tumor cells, the scientists used immunohistochemistry, a method that uses antibodies — a type of protein that the body’s immune system produces when it detects harmful substances — to identify specific molecules in tissue specimens. Subsequently, they looked for associations between the percentage of tumor cells in individual proteins and patient outcomes.

“This study sheds light on the distinctive genetic features of the NF-kB pathway and may provide targets for the development of novel therapies for ovarian cancer,” said lead investigator, Christina M. Annunziata, M.D., Ph.D.

The data revealed that the presence of one NF-kB family member—p50—in more than one-quarter of the cells was associated with poor survival. Low-frequency or nonexpression of a target gene, matrix metallopeptidase 9 (MMP9), was also associated with poor prognosis. Further, the team identified two NF-kB family members—p65 and RelB—and a protein called IKKa that plays a role in promoting inflammation, that were frequently expressed in the same cells, providing more evidence that NF-kB is active in some ovarian cancers. It is possible that the NF-kB activity in these cancers could increase their growth and/or resistance to treatment.

“This work continues to define and characterize the biological relevance of NF-kB activity in ovarian cancer by translating research findings with ovarian cancer cells in the laboratory to ovarian cancer in women at the time of initial diagnosis,” said Annunziata.

About the National Cancer Institute

NCI leads the National Cancer Program and the NIH effort to dramatically reduce the burden of cancer and improve the lives of cancer patients and their families, through research into prevention and cancer biology, the development of new interventions, and the training and mentoring of new researchers. For more information about cancer, please visit the NCI Web site at http://www.cancer.gov or call NCI’s Cancer Information Service at 1-800-4-CANCER (1-800-422-6237).

About the National Institutes of Health

The National Institutes of Health (NIH) — The Nation’s Medical Research Agency — includes 27 Institutes and Centers and is a component of the U.S. Department of Health and Human Services. It is the primary federal agency for conducting and supporting basic, clinical and translational medical research, and it investigates the causes, treatments, and cures for both common and rare diseases. For more information about NIH and its programs, visit www.nih.gov.

Comment

If NF-kB activity is ultimately determined by Dr. Annunciata et. al. to be biologically significant to ovarian cancer cell growth and/or treatment resistance, there are NF-kB inhibitor drugs (e.g., bortezomib (Velcade) or denosumab (Prolia)) in existence that theoretically could be tested in ovarian cancer clinical trials. In addition genistein, a soy isoflavone, and BAY11-7082, a preclinical compound, could be tested through preclinical/clinical testing as potential NF-kB inhibitors.  See Miller SC et. al. study below for a complete list of known NF-kB pathway inhibiting drugs and compounds.

Sources:

Abbott Labs Seeks FDA 510(k) Clearance For New Automated Ovarian Cancer Detection Test

A new diagnostic tool physicians can use to monitor patients for the most common form of ovarian cancer may soon be available in the United States.

Abbott Laboratories’ ARCHITECT HE4 assay uses a simple blood test to help in monitoring for the recurrence or progression of epithelial ovarian cancer. If approved by the FDA, this important immunoassay would be the first automated HE4 test available in the United States.

A new diagnostic tool physicians can use to monitor patients for the most common form of ovarian cancer may soon be available in the United States.  Abbott Laboratories’ (Abbott’s) ARCHITECT [Human Epididymal Protein 4] HE4 assay uses a simple blood test to help in monitoring for the recurrence or progression of epithelial ovarian cancer. If approved by the U.S. Food & Drug Administration (FDA), this important immunoassay would be the first automated HE4 test available in the United States.

The 2003 Hellstrom et al. study of known ovarian cancer biomarkers found that HE4, which has been detected in high levels in the blood of some ovarian cancer patients, shows the highest sensitivity and specificity of any other marker and is considered the best single marker for stage 1 of the disease.

According to the American Cancer Society, the five-year survival rate of ovarian cancer patients is 46 percent. However, when the disease is diagnosed and treated earlier, the survival rate increases to 93 percent. Less than 20 percent of all ovarian cancer is found in the early stage.

“The ability to monitor the recurrence or progression of ovarian cancer is a critical part of patient care. The ARCHITECT HE4 assay has the potential to be a powerful tool for both physicians and patients in the management of the disease,” said Michael Warmuth, Senior Vice President, Diagnostics, Abbott.

Abbott partnered with Fujirebio Diagnostics, Inc. in the development of the assay. The ARCHITECT HE4 assay is approved for use in Europe, as well as in other countries in Asia Pacific and Latin America. It is currently an investigational device in the United States.

About ARCHITECT HE4 Assay

The ARCHITECT HE4 assay is designed to be used as an aid in monitoring recurrence or progressive disease in patients with epithelial ovarian cancer, and must be used in conjunction with other clinical data. The ARCHITECT HE4 assay should not be used as a cancer screening test. In addition, certain types of cancer (e.g., mucinous or germ cell tumors) rarely express HE4, and the use of the ARCHITECT HE4 assay is not recommended for monitoring patients with those types of cancer.

About Ovarian Cancer

Ovarian cancer is the leading cause of death from gynecological cancers and the fifth-leading cause of cancer death in women. An estimated one in 71 women will develop ovarian cancer in their lifetimes. Women who are postmenopausal are at the greatest risk for ovarian cancer.

About Abbott Diagnostics

Abbott Diagnostics is a global leader in in vitro diagnostics (IVD) and offers a broad range of innovative instrument systems and tests for hospitals, reference labs, blood banks, physician offices and clinics. With more than 69,000 institutional customers in more than 100 countries, Abbott’s diagnostic products offer customers automation, convenience, cost effectiveness and flexibility. The history of Abbott Diagnostics is filled with examples of first-of-a-kind products and significant technological advancements, including the development of the very first diagnostic test to detect HIV.

About Abbott’s Diagnostics Businesses

Abbott is a global leader in in vitro diagnostics and offers a broad range of innovative instrument systems and tests for hospitals, reference labs, molecular labs, blood banks, physician offices and clinics. With more than 69,000 customers in more than 100 countries, Abbott’s diagnostic products offer customers automation, convenience, bedside testing, cost effectiveness and flexibility. Abbott has helped transform the practice of medical diagnosis from an art to a science through the company’s commitment to improving patient care and lowering costs.

About Abbott

Abbott (NYSE: ABT) is a global, broad-based health care company devoted to the discovery, development, manufacture and marketing of pharmaceuticals and medical products, including nutritionals, devices and diagnostics. The company employs more than 72,000 people and markets its products in more than 130 countries.

References:

  • FDA 510(k) Clearances – Overview, Device Approvals & Clearances, Products & Medical Procedures, Medical Devices, U.S. Food & Drug Administration, U.S. Department of Health & Human Services.

Additional Information:

Anderson GL, McIntosh M, Wu L, et. al. Assessing lead time of selected ovarian cancer biomarkers: a nested case-control study. J Natl Cancer Inst. 2010 Jan 6;102(1):26-38. Epub 2009 Dec 30. PubMed PMID: 20042715;PubMed Central PMCID: PMC2802285.

Andersen MR, Goff BA, Lowe KA, et. al. Use of a Symptom Index, CA125, and HE4 to predict ovarian cancer. Gynecol Oncol. 2009 Nov 27. [Epub ahead of print] PubMed PMID: 19945742.

Moore RG, McMeekin DS, Brown AK, et. alA novel multiple marker bioassay utilizing HE4 and CA125 for the prediction of ovarian cancer in patients with a pelvic mass. Gynecol Oncol. 2009 Jan;112(1):40-6. Epub 2008 Oct 12. PubMed PMID: 18851871.

Hellstrom I, Hellstrom KE. SMRP and HE4 as biomarkers for ovarian carcinoma when used alone and in combination with CA125 and/or each other. Adv Exp Med Biol. 2008;622:15-21. Review. PubMed PMID: 18546615.

Havrilesky LJ, Whitehead CM, Rubatt JM, et. al. Evaluation of biomarker panels for early stage ovarian cancer detection and monitoring for disease recurrence. Gynecol Oncol. 2008 Sep;110(3):374-82. Epub 2008 Jun 27. PubMed PMID: 18584856.

Moore RG, Brown AK, Miller MC, et. al. The use of multiple novel tumor biomarkers for the detection of ovarian carcinoma in patients with a pelvic mass. Gynecol Oncol. 2008 Feb;108(2):402-8. Epub 2007 Dec 3. PubMed PMID:  18061248.

Rosen DG, Wang L, Atkinson JN, et. al. Potential markers that complement expression of CA125 in epithelial ovarian cancer. Gynecol Oncol. 2005 Nov;99(2):267-77. Epub 2005 Aug 2.  PubMed PMID: 16061277.

Drapkin R, von Horsten HH, Lin Y, et. al. Human epididymis protein 4 (HE4) is a secreted glycoprotein that is overexpressed by serous and endometrioid ovarian carcinomas. Cancer Res. 2005 Mar 15;65(6):2162-9. PubMed PMID: 15781627.

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:

What’s Feeding Cancer Cells? — Johns Hopkins Researchers Discover How Critical Cancer Gene Controls Nutrient Use.

“Cancer cells need a lot of nutrients to multiply and survive. While much is understood about how cancer cells use blood sugar to make energy, not much is known about how they get other nutrients. Now, researchers at the Johns Hopkins University School of Medicine have discovered how the Myc cancer-promoting gene uses microRNAs to control the use of glutamine, a major energy source. The results, which shed light on a new angle of cancer that might help scientists figure out a way to stop the disease, appear Feb. 15 online at Nature. …”

“February 15, 2009- Cancer cells need a lot of nutrients to multiply and survive. While much is understood about how cancer cells use blood sugar to make energy, not much is known about how they get other nutrients. Now, researchers at the Johns Hopkins University School of Medicine have discovered how the Myc cancer-promoting gene uses microRNAs to control the use of glutamine, a major energy source. The results, which shed light on a new angle of cancer that might help scientists figure out a way to stop the disease, appear Feb. 15 online at Nature.

Chi Dang, M.D., Ph.D. The Johns Hopkins Family Professor in Oncology Research; Professor of Medicine, Cell Biology, Oncology and Pathology; and Vice Dean for Research, School of Medicine

Chi Dang, M.D., Ph.D. The Johns Hopkins Family Professor in Oncology Research; Professor of Medicine, Cell Biology, Oncology and Pathology; and Vice Dean for Research, School of Medicine

‘While we were looking for how Myc promotes cancer growth, it was unexpected to find that Myc can increase use of glutamine by cancer cells,’ says Chi V. Dang, M.D., Ph.D., the Johns Hopkins Family Professor of Oncology at Johns Hopkins. ‘This surprising discovery only came about after scientists from several disciplines came together across Hopkins to collaborate — it was a real team effort.’

In their search to learn how Myc promotes cancer, the researchers teamed up with protein experts, and using human cancer cells with Myc turned on or off, they looked for proteins in the cell’s powerhouse — the mitochondria — that appeared to respond to Myc. They found eight proteins that were distinctly turned up in response to Myc.

At the top of the list of mitochondrial proteins that respond to Myc was glutaminase, or GLS, which, according to Dang, is the first enzyme that processes glutamine and feeds chemical reactions that make cellular energy. So the team then asked if removing GLS could stop or slow cancer cell growth. Compared to cancer cells with GLS, those lacking GLS grew much slower, which led the team to conclude that yes, GLS does affect cell growth stimulated by Myc.

The researchers then wanted to figure out how Myc enhances GLS protein expression. Because Myc can control and turn on genes, the team guessed that Myc might directly turn on the GLS gene, but they found that wasn’t the case. ‘So then we thought, maybe there’s an intermediary, maybe Myc controls something that in turn controls GLS,’ says Ping Gao, Ph.D., a research associate in hematology at Johns Hopkins.

They then built on previous work done with the McKusick-Nathans Institute of Genetic Medicine at Hopkins where they discovered that Myc turns down some microRNAs, small bits of RNA that can bind to and inhibit RNAs, which contain instructions for making proteins. The team looked more carefully at the GLS RNA and found that it could be bound and regulated by two microRNAs, called miR23a and miR23b, pointing to the microRNAs as the intermediary that links Myc to GLS expression.

‘Next we want to study GLS in mice to see if removing it can slow or stop cancer growth,’ says Gao. ‘If we know how cancer cells differ from normal cells in how they make energy and use nutrients, we can identify new pathways to target for designing drugs with fewer side effects.’

This study was funded by the National Institutes of Health, the National Cancer Institute, the Rita Allen Foundation, the Leukemia and Lymphoma Society and the Sol Goldman Center for Pancreatic Cancer Research.

Authors on the paper are Ping Gao, Irina Tchernyshyov, Tsung-Cheng Chang, Yun-Sil Lee, Karen Zeller, Angelo De Marzo, Jennifer Van Eyk, Joshua Mendell and Chi V. Dang, of Johns Hopkins; and Kayoko Kita and Takfumi Ochi of Teikyo University in Japan.

On the Web:
http://www.hopkinsmedicine.org/hematology/faculty_staff/dang.html
http://www.proteomics.jhu.edu/index.php
http://www.hopkinsmedicine.org/geneticmedicine/People/Faculty/mendell.html
http://www.nature.com/nature/index.html

– JHM –

Media Contacts: Audrey Huang; 410-614-5105; audrey@jhmi.edu
Maryalice Yakutchik; 443-287-2251; myakutc1@jhmi.edu

______________________

Quoted SourceWhat’s Feeding Cancer Cells? – Johns Hopkins Researchers Discover How Critical Cancer Gene Controls Nutrient Use, Press Release, Johns Hopkins Medicine, February 15, 2009.

Primary Citationc-Myc suppression of miR-23a/b enhances mitochondrial glutaminase expression and glutamine metabolism; Ping Gao, Irina Tchernyshyov, Tsung-Cheng Chang et. al., Letter, Nature advance online publication 15 February 2009.

TP53 Gene Mutation Found in 80% of High Grade Ovarian Serous Carcinomas; TP53 Not Directly Involved In The Development of Drug Resistance

“… [T]he [Johns Hopkins] research team concluded that the frequency of TP53 gene mutations using purified tumor DNA from ovarian serous carcinomas was 80.3%, which is much higher than previously reported in the medical literature. Furthermore, the research team found that TP53 is not directly involved in the development of drug resistance in high-grade ovarian serous carcinomas.”

The TP53 gene mutation frequency in ovarian serous carcinomas has been reported to range between 50% and 80%. A research team working at the The Sidney Kimmel Comprehensive Cancer Center of The Johns Hopkins Medical Institutions (Johns Hopkins) made several important findings regarding TP53 gene mutations with respect to high grade ovarian serous carcinoma, as reported in the International Journal of Gynecological Cancer. Ovarian serous carcinoma is the most common tumor subtype within the epithelial ovarian cancer histological classification.

According to the Johns Hopkins research team, a stringent analysis of the TP53 gene using purified epithelial tumor samples has not been performed to accurately assess the TP53 gene mutation frequency and its correlation to tumor histologic grade. The research team assessed the TP53 gene mutational profile in a relatively large series of high-grade (53 primary tumors and 18 recurrent tumors) and 13 low-grade ovarian serous tumors. All samples were affinity purified, and the tumor DNA was analyzed for TP53 mutations in exons 4 through 9. In addition, the ovarian serous tumors were subjected to in vitro drug resistance testing. In vitro drug resistance assays were performed on the same tumor samples using carboplatin, cisplatin, paclitaxel, and taxotere, and the results were correlated with the TP53 mutation status.

The reported study findings are as follows:

  • TP53 mutations were detected in 57 (80.3%) of 71 high-grade carcinomas and in one (7.8%) of 13; low-grade serous tumors (an invasive low-grade serous carcinoma);
  • The mutations were predominantly missense mutations (59.6%);
  • TP53 mutations were associated with high-grade serous carcinomas and recurrent disease; and
  • There was no statistically significant correlation between TP53 mutation status and drug resistance assays or clinical stage.

Accordingly, the research team concluded that the frequency of TP53 gene mutations using purified tumor DNA from ovarian serous carcinomas was 80.3%, which is much higher than previously reported in the medical literature. Furthermore, the research team found that TP53 was not directly involved in the development of drug resistance in high-grade ovarian serous carcinomas.

Source: Assessment of TP53 mutation using purified tissue samples of ovarian serous carcinomas reveals a higher mutation rate than previously reported and does not correlate with drug resistance; Salani R, et. al., Int J Gynecol Cancer. 2008 May-Jun;18(3):487-91. Epub 2007 Aug 10.