Another area of research interest is androgen receptor (AR) intracellular trafficking in prostate cancer cells, especially in androgen-refractory prostate cancer cells. In androgen-sensitive prostate cancer cells, AR is localized to the cytoplasm in the absence of ligand. The presence of ligand induces nuclear translocation of AR and the nuclear localized, liganded-AR transactivates downstream genes. However, in androgen-refractory prostate cancer cells, AR is localized to the nucleus in the absence or presence of ligand. Ligand-independent AR activation is thought to play a critical role in the development of androgen-refractory prostate cancer. Ligand-independent AR nuclear localization is a prerequisite for AR to undergo ligand-independent activation. Elucidating the mechanism of AR ligand-independent nuclear localization may provide insights into the mechanism of androgen-refractory prostate cancer development, which may lead to new targets for the treatment of androgen-refractory prostate cancer.
We are also interested in translating our research findings into prostate cancer patient treatment. We plan to determine whether intermittent androgen ablation therapy (IAAT) of prostate cancer can be enhanced by 5 alpha-reductase inhibitor, which blocks testosterone conversion to dihydrotestosterone (DHT). We have generated preliminary data indicating that inhibition of the conversion of testosterone to DHT by 5 alpha-reductase inhibitor can enhance the expression of tumor suppressive androgen-response genes during the regrowth of a regressed normal or cancerous prostate. The enhanced expression of tumor-suppressive androgen-response genes should retard the tumor regrowth. Using an androgen-sensitive human prostate xenograft tumor as a model, we showed that 5 alpha-reductase inhibitor finasteride enhanced the efficacy of IAAT. We are establishing collaborations with medical oncologists, urologists, and pathologists to evaluate whether IAAT can be enhanced by 5 alpha-reductase inhibitors in a clinical trial.
In collaborations with Drs. Joel Nelson, Paul Johnston, and Peter Wipf, our lab is trying to identify and develop small molecular inhibitors of AR nuclear localization and function in prostate cancer cells, particularly in castration-resistant prostate cancer cells. Recent studies showed that these small molecules can inhibit prostate cancer cells resistant to the second generation anti-androgen MDV3100. Ongoing research will identify analogs of our lead compounds for pre-clinical and clinical studies.
Most cells can not divide indefinitely due to a process termed cellular senescence. Because cancer cells need to escape cellular senescence in order to proliferate and eventually form tumors, it is well accepted that cellular senescence is a powerful tumor suppressive mechanism. In addition, since several molecular changes that are observed in senescent cells occur in somatic cells during the aging process, investigating the molecular mechanisms underlying cellular senescence will also allow us to better understand the more complicated aging process. Thus, molecules that regulate cellular senescence represent potential therapeutic targets for the prevention and treatment of cancer as well as the fight against aging. Our work is directed at unraveling the role of caveolin-1 as a novel mediator of cellular senescence. Caveolin-1 is the structural protein component of caveolae, invaginations of the plasma membrane involved in signal transduction. Caveolin-1 acts as a scaffolding protein to concentrate, organize, and functionally modulate signaling molecules within caveolar membranes. Our laboratory was the first to demonstrate that caveolin-1 plays a pivotal role in oxidative stress-induced premature senescence. We found that oxidative stress upregulates caveolin-1 protein expression through the p38 MAPK/Sp1-mediated activation of the caveolin-1 gene promoter. We also demonstrated that upregulation of caveolin-1 protein expression promotes premature senescence through activation of the p53/p21Waf1/Cip1 pathway by acting as a regulator of Mdm2, PP2A-C, TrxR1 and Nrf2. Moreover, we found that caveolin-1-mediated premature senescence regulates cell transformation and contributes to cigarette smoke-induced pulmonary emphysema, directly linking caveolin-1's function to age-related diseases. Taken together, our findings indicate that caveolin-1 plays a central role in the signaling events that lead to cellular senescence. Our current main research interest is the identification, at the molecular level, of novel signaling pathways that link caveolin-1 to oxidative stress-induced premature senescence and the characterization of their relevance to aging and age-related diseases using both cellular and animal models. These investigations will provide novel insights into the cellular and molecular mechanisms underlying aging and cancerous cell transformation and will identify novel molecular targets that can be exploited for the development of alternative therapeutic options in the context of age-related diseases, including cancer.
Liver development in mice is initiated at around E8-8.5 stages of gestational development. Once foregut endoderm gains competence hepatic signatures are initiated during the process of which undergo expansion and regulated differentiation into hepatocytes and biliary epithelial cells during the process of morphogenesis. One of the major focuses of the Monga laboratory is to identify the molecular basis of hepatic morphogenesis. More specificallyinduction. The primitive liver bud contains bipotential stem cells or progenitors how does the hepatic progenitor or the bipotential stem cell undergo self-renewal (symmetric division) lineage specification and differentiate further towards primitive bile duct cells or immature hepatocytes (asymmetric division) and then to fully differentiated cells? Using conditional null mice embryonic liver cultures and other modalities the lab is investigating the roles regulation and interactions of various pathways which will not only further our understanding of this fundamental biological process but might also provide insight into the molecular basis of disease that recapitulates development in adulthood hepatocellular cancer (HCC). HCC is the third leading cause of cancer death and remains a disease with poor treatment options. Targeting pathways that are normally upregulated during liver development at the time of peak proliferation and stem cell renewal represents a novel therapeutic measure for the treatment of HCC."
Dr. Prochownik is interested in cancers resulting from the de-regulated expression of the c-Myc oncoprotein. He is using animal models of pediatric and adult liver cancer (hepatoblastoma and hepatocellular carcinoma) to ascertain the molecular, biochemical and metabolic changes that accompany tumor progression, regression and recurrence. He is utilizing over-expression and knockout models to determine how genes that cooperate with or are affected by Myc such as ChREBP and pyruvate dehydrogenase specifically contribute to the metabolic and molecular landscapes of these tumors.