GENERAL MEDICAL SCIENCES (ONCOLOGY)

DAVID DANIELPOUR, PhD Associate Professor General Medical Sciences (Oncology) Phone: 216/368-5670 Fax: 216/368-8919 email: dxd49@case.edu

Research Interests

Function and Regulation of a TGF-Β in the Prostate
My laboratory focuses on the role of transforming growth factor-beta (TGF-Β) as a tumor suppressor and regulator of growth, apoptosis and androgenic responses in the prostate. An important role for TGF-Β in androgenic control of the prostate has been previously implicated by a number of in vivo studies which showed androgens negatively regulate expression of TGF-Βs, TGF-Β receptors (TΒRI and TΒRII) and activation of rSmads (Smads 2 and 3) in the prostate. The normal cellular responses to TGF-Βs are lost or altered during prostatic carcinogenesis, concomitant with loss of TGF-Β receptor levels and loss of androgen dependence, implicating a role for TGF-Β signaling in regulation of androgen dependence and tumor suppression. To test this latter role, we disrupted the function of TGF-Β receptors in non-tumorigenic rat prostate epithelial cell lines, NRP-152 and DP-153, by over-expressing a truncated TΒRII that functions as a dominant-negative receptor (DNR). Overexpression of this DNR by retroviral transduction resulted in the malignant transformation of NRP-152 and DP-153 as assessed by s.c. tumor in athymic mice. These data fully support TGF-Β's role as a tumor suppression of the prostate.

Using primary prostate epithelial cell lines developed in my laboratory, we were first to report that TGF-Β can directly induce apoptosis of isolated prostatic cells in culture. Since then an important focus of our work has been to understand how TGF-Β induces apoptosis and how this mechanism is altered in prostate cancer. Using our cell culture system, we have demonstrated that TGF-Β induces the release of cytochrome c and the subsequent activation of caspases -9 and -3. We showed that TGF-Β may promote apoptosis by down-regulating the expression of the anti-apoptotic proteins Bcl-xl and survivin through distinct mechanisms. Survivin is an inhibitor of apoptosis protein (IAP) whose overexpression is tightly correlated with the aggressiveness of prostate cancer and is believed to play a role in chemo- and hormone-resistance in advanced prostate cancer. We have shown that an intact TGF-Β signaling pathway in pre-neoplastic prostate epithelial cells suppresses the activity of the survivin gene promoter through activating the retinoblastoma protein (Rb) and/or other pocket proteins (by a Smad-dependent mechanism), which then interact with CHR and CDE elements in the proximal region of the survivin promoter.

A second focus of this laboratory is to investigate the mechanisms governing loss of tumor suppression by TGF-Β during prostate cancer progression. Along these lines we have provided evidence that activation of the androgen receptor (AR) and the IGF-I/ PI3K/Akt/mTOR pathway, inactivation of the retinoblastoma protein (Rb) and induced expression of the LIM domain protein Hic-5 in prostate cancer may disrupt the tumor suppressive function of TGF-Β. Some of these pathways may also be important contributors to switching the function of TGF-Β from a tumor suppressor to that of an oncogene, a phenomenon associated with late-stage cancers. Understanding these mechanisms is likely to aid in the development of therapeutic strategies for the intervention of prostate cancer.

We recently made a novel discovery that Smad2 functions as a critical tumor suppressor in prostate epithelial cells. We showed that silencing the expression of Smad2 alone (by lentiviral-mediated shRNA) can promote the malignant transformation of NRP-152 cells. This has opened investigation of the role of Smad2 as a suppressor of the prostate, and we are now exploring potential changes in the posttranslational modification of Smad2 that may occur during prostate carcinogenesis.

Recent Publications

Yang, J, Wahdan-Alaswad, R., Danielpour, D. Critical role of Smad2 in Tumor Suppression and TGF-Β-induced apoptosis of prostate epithelial cells. Cancer Res, 69: 2185-2190, 2009.

Gama, V, Gomez, JA, Mayo, LD, Danielpour, D, Song, K, Jackson, MW, Haas, AL, Matsuyama, S. Hdm2 is a Ubiquitin Ligase of Ku70-Akt that promotes cell survival by inhibiting Hdm2-dependent Ku70 destabilization, Cell Death and Differentiation, 16:758-769, 2009.

Miao, H, Li, DQi Mukherjee, A, Johnson, E, Cutter, J, Basilion, J , Sedor, J, Wu, J, Danielpour, D,, Sloan, AE, Cohen, ML, Wang BC. EphA2 mediates ligand-dependent inhibition and ligand-independent promotion of cell migration through a reciprocal regulatory loop with Akt. Cancer Cell, 16:9-20, 2009.

Gomez JA, Sun W, Gama V, Hajkova D, Yoshida T, Wu Z, Miyagi M, Pink JJ, Jackson MW, Danielpour D, Matsuyama S. The C-terminus of interferon gamma receptor beta chain (IFNgammaR2) has antiapoptotic activity as a Bax inhibitor. Cancer Biol Ther, 8:55-70, 2009.

Nastuik KL, Yoo K, Lo K, Su, K, Yeung, P, Katuka, J, Danielpour, D, Krolewski, JJ. FLICE-like inhibitory protein blocks TGF-Β1 induced caspase activation and apoptosis in prostate epithelial cells, Mol. Cancer Res. 6: 231-342, 2008.

Li N., Zheng L., Lin P, Danielpour D, Pan Z, Ma J. Overexpression of bax induces down-regulation of store-operated calcium entry in prostate cancer cells. J. Cell. Physiol., 216:172-9, 2008.

Garcia JA and Danielpour D. Mammalian target of rapamycin inhibition as a therapeutic strategy for urologic malignancies. Mol Cancer Thera, 6:1347-54, 2008.

Nam, J-S., Terabe, M., Mamura, M., Kang, M-J., Chae,H., Stuelten, C., Kohn, E., Tang, B., Sabzevari,H., Anver, M.R., Lawrence, A., Danielpour,D., Lonning, S., Berzofsky, J., Wakefield, L.M., An anti-TGF-Β antibody suppresses metastasis via cooperative effects on multiple cellular compartments. Cancer Res. 68:3835-43, 2008.

Yang J, Song K, Krebs TL, Jackson MW, Danielpour D. Rb/E2F4 and Smad2/3 link survivin to TGF-Β induced apoptosis and tumor progression. Oncogene, Sep 11;27(40):5326-38, 2008. 2008.

Wang H, Song K, Yang J, Krebs TL, Danielpour D. The LIM protein Hic-5/ARA55 controls TGF-Β signaling through a direct physical interaction with Smad7. Oncogene, Nov 20;27(54):6791-805, 2008.

Song K, Wang H, Krebs TL, Danielpour D. Androgenic Control of TGF-Β Signaling in Prostate Epithelial Cells through Transcriptional Suppression of TGF-Β Receptor II. Cancer Res.;68: 8173-82, 2008.