In the study, published in the journal Cancer Research, researchers combined the drug ABT-737 with another agent BEZ235. ABT-737 targets proteins known as B-cell lymphoma 2 (Bcl-2) and Bcl-xL, which prevent apoptosis, a form of cell suicide, in cancer cells. BEZ235 directly inhibits the PI3K/AKT/mTOR pathway, and as a result, reduces the expression of another anti-apoptotic protein known as Mcl-1, which is not targeted by ABT-737. Among their many functions, signaling pathways regulate biological processes required for cellular survival. The PI3K/AKT/mTOR pathway helps keep apoptosis in check, in part, by controlling the production of Mcl-1.
However, the pathway can become dysregulated in cancer, and in so doing, contribute to uncontrolled tumor growth and resistance to conventional cancer therapies. It is activated in 50 to 80 percent of patients with acute myelogenous leukemia (AML), and in some, but not all cases, is associated with genetic mutations. Significantly, disabling both anti-apoptotic proteins, Bcl-2 and Bcl-xL, in conjunction with Mcl-1, caused profound cell death of leukemia cells in the test tube as well as in animal models of AML.
"This study builds on many years of work in our laboratory investigating the mechanisms that regulate apoptosis in human leukemia cells. To the best of our knowledge, it is the first to raise the possibility that activation of the P13K/AKT/mTOR pathway, rather than genetic mutations within the pathway, may represent the best predictor of leukemia cell responses to these targeted agents," says one of the study's key researchers Steven Grant, M.D., Shirley Carter Olsson and Sture Gordon Olsson Chair in Oncology Research, associate director for translational research, program co-leader of Developmental Therapeutics and Cancer Cell Signaling research member at VCU Massey Cancer Center. "These findings could lead to a new therapeutic strategy for patients with AML and potentially other diseases by targeting patients whose leukemia cells display activation of a specific survival pathway."
Grant's team made another discovery that helped explain the new therapy's effectiveness. They found that the therapy releases and/or activates the pro-apoptotic proteins Bim, Bak and Bax, which help trigger apoptosis. Thus, in addition to disabling major pro-survival proteins, the combination therapy also helps to unleash several additional proteins that promote apoptosis.
Moving forward, Grant and his team hope to work with pharmaceutical companies and the National Cancer Institute to develop strategies combining inhibitors of the PI3K/AKT/mTOR pathway with Bcl-2 family antagonists for the treatment of patients with AML.
Grant collaborated on this research with lead author Mohamed Rahmani, Ph.D., associate professor of internal medicine at the VCU School of Medicine, who spearheaded this research. Other collaborators included David C. Williams M.D., Ph.D., co-director of the Tissue and Data Acquisition and Analysis Core at VCU Massey Cancer Center, researcher in the Developmental Therapeutics program at Massey and assistant professor in the VCU Department of Pathology; and Andrea Ferreira-Gonzalez, Ph.D., professor in the VCU Department of Pathology.
This research was supported by National Institutes of Health grants CA93738, CA100866-01, CA130805, CA142509, and CA148431; awards from the Leukemia and Lymphoma Society of America and the Multiple Myeloma Research Foundation; and, in part, by funding from VCU Massey Cancer Center's NIH-NCI Cancer Center Support Grant P30 CA016059.
The full manuscript of this study can be found online at: http://cancerres.aacrjournals.org/content/73/4/1340.long.
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About VCU Massey Cancer Center
VCU Massey Cancer Center is one of only 67 National Cancer Institute-designated institutions in the country that leads and shapes America's cancer research efforts. Working with all kinds of cancers, the Center conducts basic, translational and clinical cancer research, provides state-of-the-art treatments and clinical trials, and promotes cancer prevention and education. Since 1974, Massey has served as an internationally recognized center of excellence. It has one of the largest offerings of clinical trials in Virginia and serves patients in Richmond and in four satellite locations. Its 1,000 researchers, clinicians and staff members are dedicated to improving the quality of human life by developing and delivering effective means to prevent, control and ultimately to cure cancer. Visit Massey online at http://www.massey.vcu.edu or call 877-4-MASSEY for more information.
About VCU and the VCU Medical Center
Virginia Commonwealth University is a major, urban public research university with national and international rankings in sponsored research. Located in downtown Richmond, VCU enrolls more than 31,000 students in 222 degree and certificate programs in the arts, sciences and humanities. Sixty-six of the programs are unique in Virginia, many of them crossing the disciplines of VCU's 13 schools and one college. MCV Hospitals and the health sciences schools of Virginia Commonwealth University compose the VCU Medical Center, one of the nation's leading academic medical centers. For more, see http://www.vcu.edu.
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