MOLECULAR CHEMOPREVENTION AND THERAPEUTICS
Mohammad Saleem Bhat, Ph.D.
The long term goals of this section are the following:
1. Understanding the biochemical, cellular and molecular processes crucial for the development of prostate, pancreatic and colon cancer
2. Identifying potential agents that could be used to treat and prevent cancer in humans
3. Identifying novel serum as well as urine-based biomarkers, that could be used for diagnosis and prognosis of prostate cancer in humans
4. Understanding the causes of disparity in prostate cancer diagnosis and outcome of therapy in African-American men
The major focus of our laboratory is in the area of translational research. The following programs are underway in our laboratory:
1. Investigation of mechanisms of chemoresistance in prostate cancer patients
Prostate cancer is the most common visceral cancer diagnosed in men; it is the second leading cause of cancer related deaths in males in the United States and the western world. The lack of effective therapies for advanced prostate cancer reflects to a large extent, the paucity of knowledge about the molecular pathways involved in prostate cancer development. After undergoing chemotherapy and radiotherapy, several cancer patients come back to the clinics with recurrence of aggressive forms of the disease. Thus, the identification of new predictive biomarkers will be important for improving clinical management, leading to improved survival of patients with prostate cancer. Such molecular targets, especially those that are indicative of proliferation, invasiveness of the disease and survival of cancerous cells (even after chemotherapy) will also be excellent candidate targets for staging the disease and establishing effectiveness of therapeutic and chemopreventive intervention of prostate cancer. We investigate the molecular mechanism that causes the failure of chemotherapy and radiotherapy in cancer patients. We have identified several molecules (genes and gene-products) responsible for the development and recurrence of aggressive forms of cancer. These include S100A4 (a calcium-binding protein), BMI-1 (a polycomb group gene and stem cell factor), cFLIP (a casapse-8 inhibitor) and matriptase (a serine protease). The main objective of these studies is to take the bench-side research to the bed-side use in clinics.
2. Role of cancer-stem cells in prostate cancer development and outcome of therapy
The critical pathological processes that occur during the development and progression of human prostate cancer and are known to confer aggressiveness to cancer cells are (1) abolishment of senescence of normal prostate epithelial cells, (2) self-renewability of prostate cancer cells even after chemotherapy and radiation, and (3) dysregulated cell cycle resulting in unchecked proliferation of cancer cells. Cellular senescence is physiologically important because it is a potent tumor suppressor mechanism that must be overcome for cells to be immortalized and transformed. Self-renewability of tumor cells is an essential defining property of a pluripotent stem cell–like phenotype of cancer cell which distinguishes it from other cell types. Stem cell–resembling population of cancer cells among the heterogeneous mix of cells constituting a tumor have been reported to be essential for tumor progression and metastasis of epithelialmalignancies. The data generated from our laboratory suggest that several cancer cells which do not respond to chemotherapy or radiotherapy possess the traits of stem cells thus regenerating themselves even after chemo or radiotherapy treatment. Polycomb group (PcG) family of proteins (which form multimeric gene repressing complexes) has been reported to be involved in self-renewability, cell cycle regulation, and senescence. BMI-1 is a transcription repressor and has emerged as an important member of PcG family. We are investigating the role for Bmi-1 protein in prostate cancer development. We hypothesize that BMI-1 protein could be developed as a diagnostic and prognostic of prostate cancer.
3. Reactivation of Tumor Suppressor Genes
Early development of cancer is largely dependent upon androgens. Further suppression of tumor suppressor genes predispose the initiated and premalignant prostate epithelial cells to acquire malignant phenotype. Among the phenotypic changes, the premalignant cells acquire increased motility, changes in cytoskeleton, changes in cell adhesion characteristics and increased tendency for clonal expansion. The interaction between SLIT-ligand and its receptor Roundabout (Robo-1) is reported to guide axons during development of the nervous system. During organogenesis, the SLIT–ROBO pathway regulates numerous processes including cell proliferation, migration and adhesion that seem to be important in the development of disparate tissues including those of the reproductive system. SLIT-ROBO1 signaling has been shown to promote cell adhesion by stimulating the interaction between E-cadherin and beta-catenin at the plasma membrane. Various studies suggest the SLIT/ROBO network acts as a tumor suppressor system in humans. We have started a broad program that is aimed to delineate the mechanism of action (tumor suppressor action) of ROBO in human cancers. We are investigating whether reactivation of ROBO system (in cancer cells within tumors) would stop the proliferation and dissemination of tumor cells to other body organs . To test our hypothesis, we are adopting novel approaches such as combining gene therapy and chemotherapy. Currently, our focus is to test our hypothesis in prostate, pancreatic and skin cancer (melanoma). We are running this program in colloboration with the Division of Translation Studies, Masonic Cancer Center, University of Minnesota. This program has high translational potential for cancer patients.
4. Role of S100A4 in the development of prostate cancer
S100A4, also known as mts1, CAPL, p9Ka, and metastasin, belongs to the S100 super-family of calcium-binding proteins and is located in a 2.05 Mbp segment of the genomic DNA of chromosome 1q21 region where most of the S100 family of gene cluster occurs. S100A4 protein has been reported to be associated with invasion and metastasis of cancer cells and has been reported to be frequently over-expressed in metastatic tumors, normal cells with uninhibited movement, such as macrophages, transformed cells and in various cancer types such as breast, ovary, thyroid, lung, esophageal squamous cell carcinoma, gastric, colon, and prostate. Earlier, we reported that S100A4 is overexpressed during progression of prostate cancer in humans and in TRAMP mouse, an autochthonous transgenic model that develops prostate cancer in a manner similar to human disease. Recently, we showed that S100A4 regulates the events leading to proliferation and invasion of prostate cancer cells. We showed that S100A4 guides the invasive phenomenon of prostate cancer cells by regulating transcription and function of matrix metalloproteinase (MMP-9) in prostate cancer cells. S100A4 is notably known for its role in metastasis. By creating a transgenic mouse model of prostate cancer lacking S100A4, we, for the first time, provide evidence that S100A4 protein, both in its intracellular and extracellular form plays a tumor promoting role in the development of prostate cancer by regulating the function of Nuclear Factor kappa B/Receptor for Advanced Glycation End products molecular circuitry.
5. Transition of androgen-dependent prostate cancer to androgen-independent phenotype
Aberrant Androgen receptor (AR) expression and activation promoted by mutations, and binding partner mis-regulation is presented in several clinical manifestations including androgen insensitivity syndrome, acne vulgaris, androgenetic alopecia, benign prostate hyperplasia (BPH), and different types of cancers in humans. AR has been found to be a principal driver of initiation and progression of prostate cancer. The initial stage of prostate cancer is dependent on androgen and can be managed by a series of therapies that are antagonist to AR or suppress AR signaling. However, the success of these therapies is temporary and after a short remission period, tumors reappear as androgenindependent or commonly known as castration-resistant prostate cancer (CRPC). It is noteworthy that FDA-approved agents (androgen receptor signaling inhibitors) such as Bicalutamide which are widely used in clinics to treat cancer show dismal results in men with advanced prostatic malignancy. Recently, it has been observed that overexpression of AR is the most common event associated with CRPC. AR (which generally responds to androgen) remains active and functional in CRPC disease. We are studying the mechanism through which AR becomes functional in prostate cancer patients exhibiting CRPC disease. Emergence of CRPC phenotype depends on different mechanism such as activation of receptor tyrosine kinase, uncontrolled cell growth, and genomic mutation of AR that allows response to nonspecific AR-ligands. We are testing whether isoforms or splice variants of androgen receptor play a role in the CRPC disease. It has been reported that AR splice variants activate genes involved in the metabolism of androgens and provide a survival advantage for cells in a low-androgen environment. Our laboratory has identified the mechanism through which AR-variants induce their pro-growth activity in tumor cells. Notably, we have identified an agent that inhibits the activity of AR-variants in CRPC cells. The validation of this mechanism-based agent in animal models is expected to provide an excellent alternative or adjuvant modality for the treatment of advanced prostate cancer, particularly of CRPC phenotype.
6. Investigating the causes of racial disparity in prostate cancer
According to the American Cancer Society, the higher overall cancer death rate among African American men is due largely to higher mortality rates from prostate, lung, and colorectal cancers. Although the overall racial disparity in cancer death rates has decreased, the death rate for all cancers combined continued to be 32% higher in African American men than in Caucasian men. African American men with prostate cancer have worse disease, with a higher incidence, younger age and more advanced disease at diagnosis, and a worse prognosis, compared to Caucasian men. In addition to socioeconomic factors and lifestyle differences, molecular alterations have been reported to contribute to this discrepancy. Recent developments in genetics, proteomics, and genomics, among other molecular biotechnologies are anticipated to greatly aid the advancement of translational research on prostate cancer racial disparity and hopefully will culminate in the discovery of novel mechanisms of disease, in addition to prognostic markers and novel therapeutic approaches. The research project running in our section is aimed to investigate the molecular mechanisms that cause the failure of cancer therapy in African American men. Though widely used in clinics, the PSA has been reported to be insufficient as a reliable biomarker for prognosis of prostate cancer in African American men. The larger aim is to identify novel biomarkers which could be used for prostate cancer prognosis in Caucasian as well as in African American men. We recently showed that BMI1, a stem cell protein, could be developed as just such a sensitive and reliable blood-biomarker.
7. Lupeol, a dietary triterpene: testing its efficacy for the prevention and treatment of prostate, pancreatic and colon cancer
Another major goal of our laboratory is to identify novel and non-toxic agents that could be developed as chemopreventive and chemotherapeutic agents for either inhibiting cancer development or treating cancer in humans. We have identified a non-toxic compound called “Lupeol” exhibiting a potential to be developed as a chemopreventive and chemotherapeutic agent against cancer. Lupeol, a fruit and vegetable based triterpene, is found in olives, grapes, cucumbers, berries, and mangoes, as well as in herbs such as aloe vera. Our laboratory has shown that Lupeol application on skin prevents cancer development in animal models. Further, we have shown that Lupeol treatment inhibits the growth of prostate, pancreatic, and skin tumors (of human origin) using relevant mouse models. These studies have generated interest in studying Lupeol for other cancer types. We recently observed that Lupeol has the potential of improving chemotherapy in colon cancer. Our pharmacokinetic studies have shown that Lupeol is bioavailable in relevant mouse models after consumption (as oral administration).
8. Testing cocoa polyphenol (dark chocolate)-based functional foods in the prevention and treatment of cancer
A functional food is any healthy food claimed to have a health-promoting or disease-preventing property beyond the basic function of supplying nutrients. Functional chocolate consumption has been associated with improvements in delayed oxidation of low-density lipoprotein cholesterol and lowered blood pressure in humans. Cocoa-based chocolate consumption has been associated with short-term improvements in delayed oxidation of low-density lipoprotein cholesterol, improved endothelial function, lowered blood pressure, and improved platelet function. Epicatechin is the major component of cocoa powder. We have employed a technique (called ACTICOA) that provides the cocoa polyphenol powder highly rich in epicatechin content. Our studies show that epicatechin rich cocoa polyphenol selectively inhibits growth of premalignant prostate and pancreatic cells while sparing normal cells via modulation of NFκB signaling pathway. We are testing cocoa polyphenol in animal models evaluating its preventive as well as therapeutic value against cancer. For our studies, we have collaborated with Barry Calibaut (Belgium), one of the leading companies in the world producing functional foods including functional chocolates. We are seeking funds for support of this research study. Our current research programs are sponsored by federal agencies including National Institutes of Health and the American Institute for Cancer Research.
Our section has joined forces with internationally renowned research institutions and investigators in its quest to defeat the lethal disease of cancer in humans. Studies are underway in partnership with following research institutions:
1. Institute for Cancer Biology, Danish Cancer Society, Copenhagen, Denmark
2. Research Center for Advanced Science and Technology, University of Tokyo, Japan
3. Mayo Clinic, Rochester, MN, USA
4. Roswell Park Cancer Institute, Buffalo, NY, USA
5. Center for Prostate Disease Research, Uniformed Services University of the Health Sciences, Bethesda, MD, USA
6. Albert Einstein College of Medicine, Bronx, NY, USA
7. University of Illinois-Chicago, IL, USA
8. Clark-Atlanta University, Atlanta, GA, USA
Professional activities of the Section Leader
Scientific Expert on Grant Review Committees of Federal Funding Agencies:
2009 RC-1 translational clinical oncology group, National Cancer Institute, NIH
2009 CBY-2 panel on Breast cancer awards (CDMRP) Department of Defence
2009 CET-2 panel on Breast cancer awards (CDMRP) Department of Defence
2010 CBY-2 panel on Breast cancer awards (CDMRP) Department of Defence
2010 CET-2 panel on Breast cancer awards (CDMRP) Department of Defence
2012 PRBC-2 panel on Peter Rowley awards, New York State Department of Health
2012 Endocrinology panel on Prostate cancer awards (CDMRP) Department of Defence
2012 TRN-DDP panel on Prostate Cancer Awards (CDMRP) Department of Defence.
2013 Endocrinology panel on Prostate cancer awards (CDMRP) Department of Defence
2013 Special Emphasis Panel-ZCA1 SRLB-J (O1)S; National Cancer Institute, NIH
Editorial Board Member of Scientific Journals: American Journal of Stem Cells; Nutrition and Medicine; Chinese Journal of Clinical Medicine; American Journal of Biomedical Sciences (Guest Editor)
Reviewer for Scientific Journals: (1) J Biol Chem, (2) Oncogene, (3) Neoplasia, (4) Cancer Research, (5) Clinical Cancer research, (6) Oncotarget, (7) PLOSE-one, (8) Biochemical pharmacology, (9) Biochemica Biophysica Acta (BBA), (10), Melanoma Pigment research (11) Cancer Letters, (12) Toxicology and Applied Pharmacology; (13) Life Sciences (14) Photochemistry and Photo biology; (15) Chemosphere (16) Clinica Chemica Acta (17) Molecular and Cellular Biochemistry (18) Phytotherapy Research (19) Journal of Pharmacy and Pharmacology (20) Evidence Based Complimentary and Alternative Medicine (21) Food Chemical Toxicology (22) Molecular Carcinogenesis (23) Journal of Environmental Pathology, Toxicology and Oncology (24) International Journal of Cancer (25) Molecular Cancer Therapeutics
Selected Publications of the Section Leader:
1. Siddique HR, Adhami VM, Parray A, Johnson JJ, Siddique I, Shekhani MT, Murtaza I, Ambartsumian N, Konety BR, Mukhtar H, Saleem M. S100A4 Oncoprotein Promotes Prostate Tumorigenesis in Transgenic Mouse Model: Regulates NFκB through RAGE Receptor. Genes and Cancer, 2013 (accepted & In Press).
2. Saleem M, Kweon MH , Johnson JJ, Adhami VM, Elcheva I, Khan N, Hafeez BB, Bhat KM, Sarfaraz S, Reagan-Shaw S, Spiegelman V, Setaluri V and Mukhtar H: “S100A4 accelerates tumorigenesis and invasion of human prostate cancer through the transcriptional regulation of MMP-9.” Proceedings of National Academy of Sciences (PNAS), USA 103:16825-14830, 2006. PMID 16990429.
3. Bhatia N, Thiyagarajan S, Elcheva I, Saleem M, Dlugosz A, Mukhtar H and Spiegelman VS: “Gli2 is targeted for ubiquitnation and degradation by β-TrCP ubiquitin ligase.” Journal of Biological Chemistry, 781: 19320-19326, 2006. PMID: 16651270.
4. Siddique HR, Parray A, Zhong W, Karnes RJ, Bergstralh EJ, Koochekpour S, Rhim JS, Konety BR, Saleem M. BMI1, stem cell factor acting as novel serum-biomarker for Caucasian and African-American prostate cancer. PLoS One. 2013;8(1):e52993. Epub 2013 Jan 7. PubMed PMID: 23308129.
5. Siddique HR, Saleem M. Role of BMI1, a stem cell factor in cancer recurrence and chemoresistance: Preclinical and clinical evidences. Stem Cells, 2012.
6. Siddique HR, Parray A, Tarapore RS, Wang L, Karnes RJ, Deng Y, Konety BR, Saleem M. BMI1 Polycomb Group Protein Acts as a Master Switch for Growth and Death of Tumor Cells: Regulates TCF4-transcriptional Factor-induced BCL2 Signaling. PLoS One. 2013 May 6;8(5):e60664.
7. Mishra SK, Siddique HR, Saleem M. S100A4 calcium-binding protein is key player in tumor progression and metastasis: preclinical and clinical evidence. Cancer Metastasis Review, 2011 Nov 23. [Epub ahead of print] PubMed PMID: 22109080.
8. Siddique HR, Mishra SK, Karnes RJ, Saleem M. Lupeol, a novel androgen receptor inhibitor: implications in prostate cancer therapy. Clinical Cancer Research, 2011 Aug 15;17(16):5379-91. PubMed PMID: 21712449.
9. Johnson JJ, Syed DN, Suh Y, Heren CR, Siddiqui IA, Saleem M, Mukhtar H. Disruption of androgen and estrogen receptor activity in prostate cancer by a novel dietary diterpene carnosol: implications for chemoprevention. Cancer Prevention Research. 2010 Sep;3(9):1112-23. PubMed PMID: 20736335.
10. Saleem M, Kweon MH, Yun JM, Syed DN, Adhami VM and Mukhtar H: “A novel dietary triterpene Lupeol induces Fas-mediated apoptotic death of androgen-sensitive prostate cancer cells and inhibits tumor growth in a xenograft model”. Cancer Research, 2005, 65(23):11203-13. PMID: 16322271.
11. Saleem M, Adhami VM, Ahmad N, Gupta S and Mukhtar H: “Prognostic significance of metastasis-associated protein S100A4 (Mts1) in prostate cancer progression and chemoprevention regimens in an autochthonous mouse model”. Clinical Cancer Research, 11, 147-153, 2005. PMID: 15671539.
12. Tatemichi M, Tazawa H, Masuda M, Saleem M, Wada S, Donehower LA, Ohgaki H, and Ohshima H: “Suppression of thymic lymphomas and increased non-thymic lymphomagenesis in trp53-deficient mice lacking inducible nitric oxide synthase gene” International Journal of Cancer, 111 (6):819-828, 2004. PMID: 15300793.
13. Murtaza I, Saleem M , Adhami VM, Hafeez BB, Mukhtar H. Suppression of cFLIP by Lupeol,a dietary triterpene is sufficient to overcome resistance to TRAIL-mediated apoptosis in chemoresistant human pancreatic cancer cells. Cancer Research, 2009 69(3) 1156-1165. PMID: 19176377
14. Saleem M, Afaq F, Adhami VM and Mukhtar H: “Lupeol modulates NFкB and PI3K /Akt pathways and inhibits skin cancer in CD-1 mice”. Oncogene, 23(30), 5203-5214, 2004. PMID: 15122342.
15. Saleem M, Murtaza I, Witkowsky O, Kohl AM, Maddodi N. Lupeol triterpene, a novel diet-based microtubule targeting agent: disrupts survivin/cFLIP activation in prostate cancer cells. Biochemical and Biophysical Research Communication, 2009 Oct 23;388(3):576-82. PubMed PMID: 19683515
Research Supported by Funding Agencies:
1. Department of Defence
2. National Cancer Institute, NIH
3. American Institute for Cancer Research
4. The Hormel Foundation
5. Prostate Translational Research Grant from Masonic Cancer Center
6. Breast Cancer Pilot Award from Hormel institute