David Danielpour - US grants

The goal of this proposal is to elucidate the biological function, and mechanism of action of a novel serpin named Trespin (for TGF-beta- repressible serpin) that we have identified in NRP-152 cells by differential display RT-PCR. We will also study the mechanism of transcriptional down-regulation of Trespin by TGF-beta and other apoptosis inducers, and the potential role of Trespin carcinogenesis. We believe that Trespin plays a role as a negative-regulator apoptosis induced by TGF-beta and many other apoptosis inducing agents for the following reasons. Loss of Trespin correlates well with the induction of apoptosis by many agents, and recombinant Trespin blocks the activation of caspase 3 in HL60 and Jurkat cell cytosols and an ICE-like caspase in NRP-152 cell cytosol. Moreover, loss of Trespin expression by TGF-beta precedes the induction of apoptosis and occurs through a transcriptional mechanism. We plan to test the hypothesis that Trespin is a regulator of apoptosis by examining the biological function of Trespin in vivo in cells transfected or retrovirally infected with expression vectors containing sense or anti-sense Trespin cDNAs. We plan to study the regulation of Trespin expression by characterizing the promoter elements and transcription factors responsible for its negative regulation by apoptosis-inducing agents. For this we will isolate the Trespin promoter, study transcriptional regulation of various elements of the Trespin promoter fused to a luciferase reporter construct and identify the transcription factors involved by co-transfection with expression constructs for such factors and mobility shift assays with nuclear extracts. We feel that the data obtained from these latter studies will help the identification of a novel transcriptional factor and/or the role of a known transcription factor in the regulation of apoptosis and its mechanism of action. Lastly, we will study the role of Trespin in carcinogenesis. This will be done by correlating expression Trespin in a variety of malignant and pre-malignant cells and tissues with their malignant phenotype. This will also be done by determining whether over- expression or under-expression of Trespin cDNA in cells transfected/infected with sense or anti-sense Trespin will alter their tumorigenic phenotype.

DESCRIPTION (revised by applicant): In the prostate, transforming growth factor-beta (TGFb) promotes growth arrest and apoptosis of epithelial cells and can either suppress or promotes tumor growth. The mechanisms by which TGFb mediates these processes are under intense investigation. TGFbl signals through promoting the binding and activation of the TGFb type I receptor (TbRI) by TbRII. Activated TbRI phosphorylates Smads 2 and 3, which promotes both their and Smad4's entry in the nucleus, where they directly or indirectly regulate transcription. A current dogma in this field is that TbRII signals only through activation of TbRI. Another dogma is that Smads are the critical trigger of virtually all TGF-b responses including growth arrest and apoptosis. However, accumulating evidence is strengthening the notion that TGFb activates a number of other kinases (i.e., MAPKs) independent of Smads. Despite these advances, nothing is known about how TbRI and TbRII activate such Smad-independent signal. We propose to test the following hypothesis: TbRII is critical to TGFb signal transduction not only through activating TbRI, that activates receptor Smads, but also by mediation of Smad-independent TGFb signals. We will test this hypothesis in prostatic epithelial cell lines by studying: i) the role of EGF in regulating TGFb responses, ii) the structural/functional basis of TbRI and TbRII and the role of Smads and MAPKs in the activation of AP-1, and iii) regulation of growth inhibition by constitutively activated Smads.

DESCRIPTION (provided by applicant): Transforming growth factor-betas (TGF-betas) are 25 kDa multifunctional autocrine/paracrine peptides with potent activity on growth suppression and apoptosis of epithelial cells. In the prostate, expression of TGF-beta protein and their receptors are induced upon androgen ablation, coincident with apoptotic cell death that occurs concomitantly in this tissue. Prostatic cells lose dependence on androgens and become resistant to TGF-beta responses during carcinogenesis, through mechanisms that remain to be defined. Further support for a tumor suppressor role of TGF-beta in the prostate comes from studies where we ablated TGF-beta signaling in two non-tumorigenic cell lines (NRP-152 and DP-153) by retroviral transduction of a dominant-negative TbetaRII, and showed the consequent loss of response to TGF-beta triggers malignant transformation. Loss of TGF-beta receptor expression is one of many potential mechanisms of TGF-beta resistance. Other pathways may involve activation of certain oncogenes that intercept TGF-beta signals at various levels. We have recently reported that DHT can directly block TGF-beta signaling through an association between AR and Smad3, leading to the transcriptional inactivation of Smad3 in LNCaP and NRP-154 prostatic epithelial cells. We provide evidence using EMSAs that AR's inhibitory effect is through blocking the binding of Smad3 to Smad Binding Elements (SBE) of target genes. Here we propose to investigate:1) the effects of DHT/AR on growth arrest and apoptosis induced by TGF-beta (or active Smad3), 2) expression of TGF-beta inducible genes by DHT/AR, 3) the structure/functional basis behind the binding of AR to Smad3, 4) possible function of AR co-activators as co-regulators or Smad3 through AR, and 5) differences in the interaction of AR with Smad3 in various nontumorigenic and tumorigenic cell lines. We believe these studies will most certainly impact on the therapeutic intervention of prostate cancer.

Project Summary: Control of TGF-¿/Smad Signaling by mTOR in Prostate Cancer Transforming growth factor-beta (TGF-¿) is well recognized to function as a potent tumor suppressor of the prostate, where it is believed to play a pivotal role in activation of cell death following androgen withdrawal. The function of TGF-¿ is lost during carcinogenesis of the prostate; however, the underlying mechanisms for this loss of TGF-¿ receptor function remain poorly studied. Studies conducted in Dr. David Danielpour's laboratory in the past several years have demonstrated that both the insulin-like growth factor-I (IGF-I) and the androgen receptor (AR) signaling pathways, which appear to be constitutively activated in a sizable proportion of prostate tumors, can block multiple steps in the TGF-¿ signaling pathway and thus contribute to loss of the ability of TGF-¿ to function as a tumor suppressor. The IGF-I/PI3K/Akt signaling pathway is commonly activated in prostate cancer through loss of PTEN function and/or elevation of IGF-I levels. We published the first reports that the IGF-I/PI3K/Akt pathway suppresses phospho-activation of Smads 2 and 3 through a mechanism that is dependent on the mammalian inhibitor of rapamycin (mTOR). However, the mechanism by which mTOR mediates such suppression is not known, and will be investigated as detailed in Aims 1 and 2 of this proposal. These aims will test our hypothesis that an mTOR complex (TORC1) directly interacts with TGF-¿ receptors and intercepts the TGF-¿ signaling pathway. Aim 2 will develop substantial mechanistic insight at the molecular level of how mTOR interacts with TGF-¿ receptors and is able to modulate TGF-¿ receptor signaling. Recent data from our laboratory suggests that inhibition of mTOR by rapamycin activates Smads 1, 3, 5 or 8 through their c- terminal phosphorylation in prostate cancer cell lines. Aim 3 will validate the identity of the phospho-Smads that are phosphorylated by rapamycin, and test our hypothesis that Smads 1, 3, 5 or 8 are critical to mediation of the cytostatic effects of rapamycin on prostate cancer cells in culture and in growth of prostate tumor xenographs in athymic mice.. Understanding the how PI3K/Akt/mTOR cross-talks with those TGF-¿ and BMP signaling will likely have substantial therapeutic potential in prostate cancer.

Project Abstract The next biannual Great Lakes Nuclear Receptor Conference will be held at the new and award-winning Tinkham Veale University Center at Case Western Reserve University on October 19 - 20, 2016. The GLNR Conference Organizing Committee members include Drs. Noa Noy, Ph.D., David Danielpour, Ph.D., Hannelore Heemers, PhD, Monica Montano, Ph.D., and Hung-Ying Kao, Ph.D. We are expecting 150+ scientists and medical professionals, representing a cross section of universities, institutes, and nonprofit organizations around the Midwest. The Great Lakes Nuclear Receptor Conference will attract experts in all aspects of nuclear receptor research ranging from basic science to clinical studies. The conference will include 16 invited speakers, 4 platform presentation sessions, 2 poster sessions, an on-site dinner on the first day and an on-site breakfast and lunch on the second day. We are very excited to have Drs. Christopher Glass and Lorraine Gudas as our keynote speakers, who we are sure will draw many other acclaimed investigators to this unique conference. The rest of the program will provide a platform for presentations by junior investigators and postdoctoral fellows, with senior researchers serving as session moderators. Participants will also have the opportunity to present their work and closely interact with each other during poster sessions. The conference is especially designed to foster the next generation of nuclear receptor researchers. ? The conference will foster open discussion between basic and clinical scientists to promote exchange of research, ideas and cutting-edge breakthroughs in the field of nuclear receptor and cancer therapeutics. Participants will benefit by gaining a better understanding of the field, and advance innovation research technologies through new collaborations and networking opportunities. ? The GLNR conference will offer many opportunities to reach out to, encourage and support individuals traditionally underrepresented in science, including women, racial/ethnic minorities, and persons with disabilities. Financial, programmatic and career development support will be available to these individuals. ? The main topics to be addressed at the conference include: 1) nuclear receptors in cancer, 2) genome- wide nuclear receptor action, 3) non-classical mechanism androgen receptor action, 4) nuclear receptors in metabolism. ? The overall goal of the proposed conference is to bring together a group of investigators (including senior scientists, mid-career scientists, junior scientists, postdoctoral fellows, and graduate students) who work in diverse disciplines to present, discuss and critique their newest research findings that share a common focus on the nuclear receptor. This is expected to advance the fields by promoting collaborations.