Glutamine Ratio is Key Ovarian Cancer Indicator

Glutamine plays an important role in cellular growth in several cancers. A Rice University-led study shows how ovarian cancer metabolism changes between early and late stages. In this study, a further link between glutamine dependency and tumor invasiveness is established in ovarian cancer.

A Rice University-led analysis of the metabolic profiles of hundreds of ovarian tumors has revealed a new test to determine whether ovarian cancer cells have the potential to metastasize, or spread to other parts of the body. The study also suggests how ovarian cancer treatments can be tailored based on the metabolic profile of a particular tumor.

The research, which appears online this week in Molecular Systems Biology, was conducted at the Texas Medical Center in Houston by researchers from Rice University, the University of Texas M.D. Anderson Cancer Center, and the Baylor College of Medicine.

Deepak Nagrath

Deepak Nagrath, Assistant Professor of Chemical and Biomolecular Engineering at Rice University

“We found a striking difference between the metabolic profiles of poorly aggressive and highly aggressive ovarian tumor cells, particularly with respect to their production and use of the amino acid glutamine,” said lead researcher Deepak Nagrath Ph.D. of Rice University. “For example, we found that highly aggressive ovarian cancer cells are glutamine-dependent, and in our laboratory studies, we showed that depriving such cells of external sources of glutamine — as some experimental drugs do — was an effective way to kill late-stage cells.

“The story for poorly aggressive cells was quite different,” said Nagrath, Assistant Professor of Chemical and Biomolecular Engineering at Rice. “These cells use an internal metabolic pathway to produce a significant portion of the glutamine that they consume, so a different type of treatment — one aimed toward internal glutamine sources — will be needed to target cells of this type.”

The research is part of a growing effort among cancer researchers worldwide to create treatments that target the altered metabolism of cancer cells. It has long been known that cancer cells adjust their metabolism in subtle ways that allow them to proliferate faster and survive better. In 1924, Otto Warburg showed that cancer cells produced far more energy from glycolysis than did normal cells. The Nobel Prize-winning discovery became known as the “Warburg effect,” and researchers long believed that all cancers behaved in this way. Intense research in recent decades has revealed a more nuanced picture.

“Each type of cancer appears to have its own metabolic signature,” Nagrath said. “For instance, kidney cancer does not rely on glutamine, and though breast cancer gets some of its energy from glutamine, it gets even more from glycolysis. For other cancers, including glioblastoma and pancreatic cancer, glutamine appears to be the primary energy source.”

Rice University Researchers

Researchers at Rice University’s Laboratory for Systems Biology of Human Diseases analyzed the metabolic profiles of hundreds of ovarian tumors and discovered a new test to determine whether ovarian cancer cells have the potential to metastasize. Study co-authors include, from left, Julia Win, Stephen Wahlig, Deepak Nagrath, Hongyun Zhao, Lifeng Yang and Abhinav Achreja.

Nagrath, director of Rice University’s Laboratory for Systems Biology of Human Diseases, said the new metabolic analysis indicates that ovarian cancer may be susceptible to multidrug cocktails, particularly if the amounts of the drugs can be tailored to match the metabolic profile of a patient’s tumor.

The research also revealed a specific biochemical test that pathologists could use to guide such treatments. The test involves measuring the ratio between the amount of glutamine that a cell takes up from outside and the amount of glutamine it makes internally.

“This ratio proved to be a robust marker for prognosis,” said University of Texas M.D. Anderson Cancer Center co-author Anil Sood, M.D., Professor of Gynecologic Oncology and Reproductive Medicine and co-director of the Center for RNA Interference and Non-Coding RNA. “A high ratio was directly correlated to tumor aggression and metastatic capability. Patients with this profile had the worst prognosis for survival.”

The three-year study included cell culture studies at Rice as well as a detailed analysis of gene-expression profiles of more than 500 patients from the Cancer Genome Atlas and protein-expression profiles from about 200 M.D. Anderson patients.

“The enzyme glutaminase is key to glutamine uptake from outside the cell, and glutaminase is the primary target that everybody is thinking about right now in developing drugs,” Nagrath said. “We found that targeting only glutaminase will miss the less aggressive ovarian cancer cells because they are at a metabolic stage where they are not yet glutamine-dependent.”


Lifeng Yang, Study Lead Author & Graduate Student, Systems Biology of Human Diseases, Rice University

Rice University graduate student Lifeng Yang, lead author of the study, designed a preclinical experiment to test the feasibility of a multidrug approach, involving the use of a JAK inhibitor and a glutaminase inhibitor. This “drug cocktail” approach inhibited the early stage production of internal glutamine, while also limiting the uptake of external glutamine.

“That depleted all sources of glutamine for the cells, and we found that cell proliferation decreased significantly,” Yang said.

Nagrath said the study also revealed another key finding — a direct relationship between glutamine and an ovarian cancer biomarker called “STAT3” (Signal Transducer And Activator Of Transcription 3).

“A systems-level understanding of the interactions between metabolism and signaling is vital to developing novel strategies to tackle cancer,” said M.D. Anderson co-author Prahlad Ram Ph.D., Associate Professor of Systems Biology and co-director of the M.D. Anderson Cancer Center’s Systems Biology Program. “STAT3 is the primary marker that is used today to ascertain malignancy, tumor aggression and metastasis in ovarian cancer.”

Nagrath said, “The higher STAT3 is, the more aggressive the cancer. For the first time, we were able to show how glutamine regulates STAT3 expression through a well-known metabolic pathway called the TCA cycle, which is also known as the ‘Krebs cycle.’”

Nagrath said the research is ongoing. Ultimately, Dr. Nagrath hopes the investigations will lead to new treatment regimens for cancer as well as a better understanding of the role of cancer-cell metabolism in metastasis and drug resistance.

Co-authors include Hongyun Zhao, Stephen Wahlig, Abhinav Achreja and Julia Win (all affiliated with Rice University); Tyler Moss, Lingegowda Mangala, Guillermo Armaiz-Pena, Dahai Jiang, Rajesha Roopaimoole, Cristian Rodriguez-Aguayo, Imelda Mercado-Uribe, Gabriel Lopez-Berestein and Jinsong Liu (all affiliated with M.D. Anderson Cancer Center); Juan Marini of Baylor College of Medicine; and Takashi Tsukamoto of Johns Hopkins University.

The research was supported by seed funding from (i) the Collaborative Advances in Biomedical Computing Program at Rice Univesity’s Ken Kennedy Institute for Information Technology, (ii) Rice University’s John and Ann Doerr Fund for Computational Biomedicine, (iii) the Odyssey Fellowship Program at the MD Anderson Cancer Center, (iv) the estate of C.G. Johnson Jr., (v) the National Institutes of Health, (vi) the Cancer Prevention and Research Institute of Texas, (v) the Ovarian Cancer Research Fund, (vi) the Blanton-Davis Ovarian Cancer Research Program, (vii) the Gilder Foundation, and (viii) the MD Anderson Cancer Center.


LabCorp Announces Availability of Ovarian Cancer Blood Test To Assess The Presence of Early Stage Ovarian Cancer

“Laboratory Corporation of America® Holdings is now offering OvaSure™, an Ovarian Cancer Screening test to assess the presence of early stage ovarian cancer in high-risk women. In a recent study of high risk and average risk subjects, this blood test, using six biomarkers and research conducted at Yale University School of Medicine, was shown to discriminate between disease-free women and ovarian cancer patients (stage I-IV) with high specificity (99.4%) and sensitivity (95.3%). Additional studies performed at Yale University School of Medicine demonstrate comparable findings.”

On March 14, 2008, the H*O*P*E*™ weblog reported that a new blood test developed by the Yale University School of Medicine detected early stage ovarian cancer with 99% accuracy in Phase II clinical trial testing. To review the March 14 H*O*P*E*™ weblog post, click here. In 2006, Laboratory Corporation of America (Lab Corp) obtained licensing rights to the ovarian cancer early detection blood test, known as OvaSure™, from Yale. Today, Lab. Corp. announced in a press release that it is making the OvaSure™ blood test immediately available nationwide to women who are at high risk of developing ovarian cancer in the future. The relevant portion of the Lab Corp. press release dated June 23, 2007 is set forth below.

LabCorp Announces Availability of OvaSure™

Burlington, NC, June 23, 2008 – Laboratory Corporation of America® Holdings (LabCorp®) (NYSE: LH) is now offering OvaSure™, an Ovarian Cancer Screening test to assess the presence of early stage ovarian cancer in high-risk women. In a recent study of high risk and average risk subjects, this blood test, using six biomarkers and research conducted at Yale University School of Medicine, was shown to discriminate between disease-free women and ovarian cancer patients (stage I-IV) with high specificity (99.4%) and sensitivity (95.3%). Additional studies performed at Yale University School of Medicine demonstrate comparable findings.

‘LabCorp is pleased to offer for high-risk women the OvaSure test to enhance the potential of detecting and treating ovarian cancer in its early or localized stage when the likelihood of survival is greatest,’ said Myla P. Lai-Goldman, M.D., Executive Vice President, Chief Medical Officer of LabCorp. ‘OvaSure is a significant addition to LabCorp’s family of proteomic tests, and a major component of LabCorp’s strategy to bring the latest in diagnostic technology to women’s healthcare.’

It has been estimated that for the year 2008, 21,650 women will be newly diagnosed with ovarian cancer. It has been further estimated that 15,520 women will die from the disease in 2008. Despite being one-eighth as common as breast cancer, it is three times more lethal. If ovarian cancer is diagnosed and treated at the localized stage, the 5-year survival rate is 92%; unfortunately, only 19% of all cases are found at the localized stage. Most women have their ovarian cancer detected at the regional or distant stage when the 5-year survival rates are 71% and 30% respectively.

‘I am pleased that this test is available to help physicians detect and treat ovarian cancer in its earliest stages,’ said Gil Mor, M.D., associate professor in the Department of Obstetrics, Gynecology & Reproductive Sciences at Yale and a member of Yale Cancer Center. ‘Our team is proud that our research may help play a role in higher survival rates for women with this disease.’”

[Quoted Source: LabCorp Announces Availability of OvaSure™ , Laboratory Corporation of America Press Release dated June 23, 2008.]

Comment**: Although additional Phase III clinical trial testing with a larger patient population is required, the OvaSure™ blood test may represent the “gold standard” for early stage ovarian cancer detection in the near future. The immediate availability of the OvaSure™ blood test for use by women who are at high risk for developing ovarian cancer could save lives by catching ovarian cancer in its earliest stages, thereby making treatment of the disease highly effective. To view the news report regarding the Yale ovarian cancer screening blood test that aired on April 21, 2008, click here.

**As of August 21, 2008, the amended OvaSure™ test “use” information provides, among other things, that a woman who has had both ovaries removed (i.e., a bilateral oophorectomy) should not use the test. Accordingly, it appears that the OvaSure™ test cannot be used by a “high-risk” woman to screen for an ovarian cancer recurrence, if she had both ovaries removed as part of her first line treatment following initial diagnosis of the disease.

OvaSure™ Information: The OvaSure™ blood test is now available nationwide through LabCorp. If you want to review OvaSure™ blood test information on the LabCorp. website, click here (then click on the letter “O” located on the upper left side panel keyboard and scroll down until you find the three OvaSure™ blood test information entries). It is our understanding that the OvaSure™ test cost approximately (U.S.)$225 and test results are available within five business days.

OvaSure™ Use (updated 8/21/08): “The OvaSureTM assay may be used as a tool to identify high-risk women who might have ovarian carcinoma. OvaSureTM is not indicated for a patient who is currently undergoing chemotherapy, who has had both ovaries removed, who is pregnant, or who is lactating. About 10% of women with benign ovarian masses (including cysts) may have positive results by this test.”

OvaSure™ Limitations (updated 8/21/08) : “Pregnant women or women who are lactating should not be screened by the assay because it may lead to false-positive results. A Calculated Risk Index of 0.50 or greater indicates a positive reading, which is suggestive of ovarian cancer (possible presence of disease). In a clinical study (see Journal Abstract below) across all disease stages, the six-marker panel composed of leptin, prolactin, osteopontin, insulin-like growth factor II, macrophage inhibitory factor, and CA-125 demonstrated a sensitivity of 95.3% and a specificity of 99.4% in detecting disease. Greater than 99% sensitivity (119 of 120) was shown in late-stage disease (stage III and stage IV). In early stage disease (stage I and stage II), the assay demonstrated a sensitivity of 91.6%, providing a significant improvement over CA-125 alone (less than 60% of stage I and stage II combined) for ovarian cancer detection. All positive readings should be retested on a new sample drawn at least three weeks after the original sample was collected. Patients with positive results confirmed by retesting on a second sample should be followed by a women’s health specialist who may order additional evaluations, such as sensitive imaging. Components used in this test are labeled as research purposes only. The performance characteristics of this product have not been established by the assay manufacturer. Results should not be used as a diagnosis for ovarian cancer without confirmation of the diagnosis by another medically established diagnostic product or procedure.”

OvaSure™ Journal Abstracts and Full Text Studies:


  • July 2, 2008: The Society of Gynecologic Oncologists (SGO) issued a statement regarding the Labcorp OvaSure™ test. The SGO statement, dated July 2, 2008, is quoted below in its entirety.

“July 2, 2008

Society of Gynecologic Oncologists
Statement Regarding OvaSureTM

The Society of Gynecologic Oncologists (SGO) recognizes the need for accurate early detection biomarkers for ovarian cancer. For this reason, SGO reviewed the literature regarding OvaSure, a serum-based diagnostic test for ovarian cancer.

After reviewing OvaSure’s materials, it is our opinion that additional research is needed to validate the test’s effectiveness before offering it to women outside of the context of a research study conducted with appropriate informed consent under the auspices of an institutional review board.

SGO is committed to actively following and contributing to this vitally important research. As physicians who care only for women with gynecologic cancers, our hope is that these cancers can either be prevented or detected early. Because no currently available test has been shown to reliably detect ovarian cancer in its earliest and most curable stages, we will await the results of further clinical validation of OvaSure with great interest.”

The SGO is a national medical specialty organization of physician-surgeons who are trained in the comprehensive management of women with malignancies of the reproductive tract. The purpose of the SGO is to improve the care of women with gynecologic cancers by encouraging research and disseminating knowledge to raise the standards of practice in the prevention and treatment of gynecologic malignancies, in cooperation with other organizations interested in women’s health care, oncology and related fields.

Quoted Update Source: Society of Gynecologic Oncologists Statement Regarding OvaSure™, Society of Gynecologic Oncologists, July 2, 2008 (Adobe Reader PDF document).

Other Update Sources: Fast Facts: Background on The Society of Gynecologic Oncologists, Society of Gynecologic Oncologists Press Kit, undated.

“AM Nick is a Fellow in the Department of Gynecologic Oncology, and AK Sood is the Bettyann Asche-Murray Distinguished Professor in the Department of Gynecologic Oncology and in the Department of Cancer Biology, both at the University of Texas MD Anderson Cancer Center, Houston, TX, USA.

In order to overcome the significant mortality associated with ovarian cancer, a highly sensitive and specific screening test is urgently needed. CA125 is used to assess response to chemotherapy, detect recurrence, and distinguish malignant from benign disease; however, this marker is elevated in only 50-60% of stage I ovarian cancers, making it inadequate for early detection of malignancy. In this Practice Point, we discuss Visintin et al.‘s attempt to validate a novel multiplex assay that uses a panel of six serum biomarkers-leptin, prolactin, osteopontin, insulin-like growth factor II, macrophage inhibitory factor, and CA125 [medical abstract & full text of Visintin et. al. study provided above]. The study included 362 healthy controls and 156 patients with newly diagnosed ovarian cancer. The final model yielded 95.3% sensitivity, 99.4% specificity, a positive predictive value of 99.3% and a negative predictive value of 99.2%. These results indicate potential utility of this assay for early detection of ovarian cancer, although further validation is needed in a sample set representative of the general population.”

  • August 21, 2008: The Labcorp information with respect to the OvaSure™ test was recently modified. Despite that fact that the test was made available for “high-risk” women, it cannot be used by women who have had both ovaries removed. Consequently, it appears that a woman who had both ovaries removed (i.e., bilateral oophorectomy) after an initial diagnosis of ovarian cancer, cannot use the OvaSure™ test to screen for a potential recurrence of the disease in the future.