Scientists from Virginia Commonwealth University Massey Cancer Center have revealed how two genes interact to kill a wide range of cancer cells. Originally discovered by the study's lead investigator Paul B. Fisher, M.Ph., Ph.D., the genes known as mda-7/IL-24 and SARI could potentially be harnessed to treat both primary and metastatic forms of brain, breast, colon, lung, ovary, prostate, skin and other cancers.
In the study, recently published in the online version of the journal Cancer Research, Fisher's team found that forced expression of MDA-7/IL-24 (melanoma differentiation associated gene-7/interlukin-24) stimulates SARI (suppressor of AP-1, induced by interferon) expression in what is known as an autocrine/paracrine loop, which ultimately causes cancer cells to undergo a form of cell suicide known as apoptosis. Autocrine/paracrine loops occur when the expression of a particular gene or its encoded protein causes cells to secrete molecules that bind to surface receptors and force the expression of more of the same protein in an ongoing cycle.
"Many previous studies show that MDA-7/IL-24 can selectively kill diverse cancer cells through multiple mechanisms, but what was unclear was how exactly MDA-7/IL-24 interacted with other genes to promote cancer toxicity," says Fisher, Thelma Newmeyer Corman Endowed Chair in Cancer Research and co-leader of the Cancer Molecular Genetics research program at VCU Massey Cancer Center, and chairman of the Department of Human and Molecular Genetics and director of the VCU Institute of Molecular Medicine (VIMM) at VCU School of Medicine. "Our study uncovered multiple signaling pathways used by MDA-7/IL-24 that facilitate cancer cell death through the induction of SARI."
Fisher and his team identified an existing combination of receptors, IL-20R1 and IL-20R2, and a discovered new combination of receptors, IL-22R1 and IL-20R1, through which signaling occurs to induce the MDA-7/IL-24 autocrine/paracrine loop. Once activated by the MDA-7/IL-24 protein, these receptors cause both normal and cancer cells to produce and secrete the MDA-7/IL-24 protein, which, in turn, activates SARI. The process was shown to culminate in apoptosis in cancer cells. Normal, healthy cells were not affected in the experiments.
The researchers are now focusing on developing small molecule drugs that induce MDA-7/IL-24 and/or SARI in cancer cells. They have also been experimenting with cancer-selective replicating viruses that seek out cancer cells and infect them with the toxic genes—an approach that has already been successfully employed in a phase 1 clinical trial using engineered viruses that deliver MDA-7/IL-24.
"This study helped us better understand how MDA-7/IL-24 works to kill a broad range of cancer cells through the induction of SARI," says Fisher. "In addition to giving us another target for the development of new therapies, our research also suggests that we may be able to monitor the expression of SARI in order to determine the effectiveness of future therapies under development that target MDA-7/IL-24."
Fisher collaborated on this research with Praveen Bhoopathi, Ph.D., postdoctoral research scientist in the Department of Human and Molecular Genetics at the VCU School of Medicine; Swadesh K. Das, Ph.D., instructor in the VCU Department of Human and Molecular Genetics and VIMM member; Devanand Sarkar, M.B.B.S., Ph.D., Harrison Research Scholar and member of the Cancer Molecular Genetics research program at VCU Massey, associate professor in the VCU Department of Human and Molecular Genetics and associate scientific director of cancer therapeutics at VIMM; Luni Emdad, M.B.B.S., Ph.D., member of the Cancer Molecular Genetics research program at VCU Massey, assistant professor in the VCU Department of Human and Molecular Genetics and VIMM member; Santanu Dasgupta, Ph.D., member of the Cancer Molecular Genetics research program at VCU Massey, assistant professor in the VCU Department of Human and Molecular Genetics and VIMM member; and Rupesh Dash, Ph.D., former postdoctoral research scientist in the VCU Department of Human and Molecular Genetics and now assistant professor at the Institute of Life Sciences in Bhubaneshwar, India.
This research was supported by National Institutes of Health grants 5 R01 CA097318, P01 CA104177 and 1 R01CA127641; and, in part, by VCU Massey Cancer Center's NIH-NCI Cancer Center Support Grant P30 CA016059.
The full manuscript of this study is available online at: http://cancerres.aacrjournals.org/content/early/2013/11/26/0008-5472.CAN-13-1062.full.pdf+html
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About VCU Massey Cancer Center
VCU Massey Cancer Center is one of only 68 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 offers the most cancer clinical trials in Virginia and serves patients at 10 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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