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.


To Fight Cancer, Know The Enemy

An Op-Ed entitled “To Fight Cancer, Know the Enemy” was published in The New York Times on August 6, 2009.  The author of the Op-Ed was James D. Watson, Ph.D.  James Watson co-discovered the DNA double helix structure; a discovery for which he received the 1962 Nobel Prize for Physiology or Medicine. In the article, Watson states his belief that beating cancer is now a realistic ambition, and he makes several suggestions designed to ensure that victory.

On August 6, 2009, an Op-Ed entitled To Fight Cancer, Know the Enemy was published in The New York Times (NYT).  The author of the article was James D. Watson, Ph.D. James Watson co-discovered the DNA double helix structure; a discovery for which he received the 1962 Nobel Prize for Physiology or Medicine.  Dr. Watson is the Chancellor Emeritus of Cold Spring Harbor Laboratory, and is generally considered the father of molecular biology. Throughout most of his career, James Watson’s novel scientific ideas generated great controversy among, and resistance from, many members of the scientific community.  The suggestions posed by James Watson in his August 6th NYT Op-Ed are likely no exception.

Watson begins the Op-Ed by suggesting an ambitious, yet optimistic, goal in the area of cancer research:

“The National Cancer Institute, which has overseen American efforts on researching and combating cancers since 1971, should take on an ambitious new goal for the next decade:  the development of new drugs that will provide lifelong cures for many, if not all, major cancers.  Beating cancer now is a realistic ambition because, at long last, we largely know its true genetic and chemical characteristics. …”

James D. Watson

James D. Watson, Ph.D. is the Chancellor Emeritus of the world-renowned Cold Spring Harbor Laboratory. Dr. Watson co-discovered DNA's double helix structure; a discovery for which he received the 1962 Nobel Prize for Physiology or Medicine. In an Op-Ed published in the New York Times on August 6, 2009, Dr. Watson states: "...Beating cancer now is a realistic ambition because, at long last, we largely know its true genetic and chemical characteristics."

Despite President Nixon’s declaration of  war on cancer in 1971, Watson states that the goal of “beating cancer” was not possible prior to the year 2000, because researchers did not possess the necessary scientific understanding of cancer molecular biology. Extensive details about specific cancers only became known after the 2003 completion of the Human Genome Project, says Watson. Researchers have identified most of the major cellular pathways through which cancer-inducing signals move through cells, and Watson notes that 20 or so signal-blocking drugs are in human clinical testing. By way of example, Watson highlights the breast cancer drug Herceptin, which is used to fight an aggressive form of breast cancer. Herceptin was approved initially by the U.S. Food & Drug Administration (FDA) in 1998, and today represents the standard of care in treating so-called “HER-2 positive” breast cancer.

With this scientific background, Dr. Watson outlines several suggested changes to the current U.S. cancer research paradigm. He believes that the various changes listed below will give the nation a fighting chance to win the war on cancer.

Change FDA Regulations To Allow Combination Testing of New Cancer Drugs Which Are Ineffective As Monotherapies.

Noting the lack of new cancer drugs that lead to lifelong cures, Watson explains that there are many types of cancer-causing “genetic drivers” within a single cancer cell. Although an analysis of several cancer genetic drivers may allow a doctor to prescribe more personalized chemotherapy treatments for the patient, Watson believes that use of drugs against one genetic cancer driver would simply lead to the emergence of increasingly destructive second and third drivers due to the inherent genetic instability of cancer cells.  Accordingly, Watson concludes that most anticancer drugs will not reach their full potential unless they are given in combination to shut down multiple cancer genetic drivers within a cancer cell simultaneously.

Dr. Watson, however, is quick to note that current FDA regulations effectively prohibit combination testing of new cancer drugs that, when administered alone, prove ineffective.  Thus, Watson concludes that current FDA regulations must be amended to allow combination testing of new cancer drugs that prove ineffective as monotherapies.

Better Understand The Chemical (Rather Than Genetic) Makeup of Cancer Cells

Dr. Watson believes that researchers should shift the current focus of cancer research away from decoding the genetic characteristics of cancer, and obtain a better understanding of the chemical reactions that occur within cancer cells. This suggestion, Watson explains, is based upon a 1924 discovery made by the German biochemist (and 1931 Nobel Laureate) Otto Warburg.  During experimentation, Warburg observed that cancer cells, irrespective of whether they grow in the presence or absence of oxygen, produce large amounts of lactic acid. Approximately one year ago, the significance of Warburg’s observation was revealed, says Watson. The metabolism of all proliferating cells (including cancer cells) is largely directed toward the synthesis of cellular building blocks from the breakdown of glucose. Based upon this recent discovery, Dr. Watson concludes that glucose breakdown runs faster in growing cells then in differentiated cells (i.e., cells that stop growing and perform specialized functions within the body).

The turbocharged breakdown of glucose in growing cells is attributable to growth-promoting signal molecules that effectively turn up the levels of transporter proteins which move glucose molecules into the cell, explains Watson. With this important discovery in hand, Watson suggests that researchers determine whether new drugs that specifically inhibit the key enzymes involved in the breakdown of glucose can produce an anticancer effect. Because this determination requires a better understanding of the chemical makeup of cancer cells, Watson believes that biochemists (rather than molecular biologists) will again move to the forefront of cancer research.

NCI Should Fund Smaller Biotechnology Companies & Increase Its Funding to Major Research-Oriented Cancer Centers

The next issue addressed by Dr. Watson relates to the lack of funding available to small biotechnology companies, which are generally engaged in highly innovative research. In the past, the requisite funding of these companies was provided by venture capitalists (VCs), Watson notes.  The level of VC funding required by small biotech companies is not currently available due to the severe U.S. economic downturn. To resolve this critical capital funding issue, Watson suggests that the National Cancer Institute (NCI) fund small biotech companies. This action, Watson believes, will allow the biotech companies to move drug discoveries from the laboratory into human clinical testing on an accelerated basis. In tandem with funding small biotech companies, Dr. Watson also requests NCI to increase its funding to major research-oriented cancer centers that engage in “low probability-high payoff” research projects, which are generally turned down by large pharmaceutical and biotech companies.

President Obama Should Appoint A Strong Leader To The Directorship of NCI

In 1971, the U.S. Congress provided the president, rather than the head of the National Institutes of Health, with the authority to appoint the NCI director.  Watson characterizes NCI in his Op-Ed as “an outpost of the White House” that has “… become a largely rudderless ship in dire need of a bold captain who will settle only for total victory.”  To resolve this issue, Dr. Watson advises President Barack Obama to appoint a strong leader, from among the nation’s best cancer researchers, to the directorship of NCI.  As part of this new leadership structure, Watson also recommends that NCI recruit a seasoned pharmaceutical developer who can radically increase the speed of anticancer drug development and human clinical testing.

Application Of Sun Tzu’s Strategies On The Art Of War To Cancer Research

Sun Tzu

A statue of the iconic Chinese military leader Sun Tzu. Sun Tzu wrote the earliest -- and still the most revered -- military treatise in the world. This 6th century BC masterpiece is best known to most of us as "The Art of War."

At the conclusion of his Op-Ed, Watson acknowledges that his views will provoke rebuttals from prominent scientists who believe that it is not the right time to wage war on cancer. Moreover, Watson anticipates that many scientists will recommend that, until victory is more certain, the U.S. should not expend large sums of money on cancer research. Watson admits that money alone will not win the war on cancer, but he emphasizes that victory over cancer will not come ” from biding our time.” As part of the Op-Ed title, Watson uses the phrase “know the enemy;” a phrase commonly attributed to the ancient Chinese military leader Sun Tzu. Sun Tzu wrote the earliest — and still the most revered — military treatise in the world.  This 6th century BC masterpiece is best known to most of us as The Art of War.  The clever use of the phrase “know the enemy” by Dr. Watson may suggest that the enemy is indeed cancer, and perhaps, ourselves as represented by the current U.S. cancer research paradigm.

In chapter III of The Art of War, entitled Attack by Stratagem, Sun Tzu describes the dual knowledge that one must possess to achieve ultimate victory in war:

“…If you know the enemy and know yourself, you need not fear the result of a hundred battles. If you know yourself but not the enemy, for every victory gained you will also suffer a defeat. If you know neither the enemy nor yourself, you will succumb in every battle. …”

To follow the advice of James Watson is to better know ourselves and the formidable enemy known as “cancer.” Will Watson’s advice allow us to achieve ultimate victory in the war on cancer? Perhaps. Only time (and appropriate research funding) will tell.

Source: To Fight Cancer, Know The Enemy, by James D. Watson, Op-Ed, The New York Times, August 6, 2009.