Jialing Xiang - US grants

the development of androgen-independence by prostate cancer cells is a major hurdle in the treatment of prostate cancer with conventional therapies. The major molecular defect is that the cancer cells fail to initiate programmed cell death (apoptosis) in response to various eupeptic stimuli. Recently we have found that over expression of bad, which is a pro-apoptotic molecule and a counterpart of BCL-2, includes apoptose in prostate cancer cells. In fact, androgen-independent LNCaP cells are even more sensitive to Bad-induced cell death than their androgen-dependent counterparts. Furthermore, subcellular localizations of Bad appear to be different in androgen-dependent and independent LNCaP cells. We hypothesize that Bad may play a critical role in the balance between cell survival and death in androgen-independent prostate cancers. We propose to investigate the molecular mechanisms underlying Bad-induced apoptosis in prostate cancer cells, as well as its relationship to the androgen-independent in vitro and in vivo. This work is novel as it will shed light on the interplay between an eupeptic pathway and androgen regulation and might have therapeutic implications for prostate cancer. The training environment for the applicant is excellent. Dr. Shustung Liam, the ,mentor, has been studying androgen regulation and prostate cancer for more tan 40 years and his group has made several ground breaking contributions to the field. The Ben May Institution for Cancer Research has long tradition for prostate cancer research, starting from the Noble Prize winning work of Dr. Huggins on treatment of prostate cancer. The University of Chicago has several excellent prostate cancer research programs. With many investigators and exports working in the field of prostate cancer and many Core facilities, including a prostate tissue bank. With the excellent training I have received in the fields of cycle regulation, apoptosis and gene therapy, I am confident that I will be able to pursue the proposed studies and make a successful transition into the front tier of prostate cancer research. The financial support provided by this NIH award will allow me to complete my training and to launch my carrier ad an independent investigator in an academic setting.

[unreadable] DESCRIPTION (provided by applicant): The androgen receptor (AR) is member of the steroid hormone receptor superfamily. Upon binding to its ligand androgen, AR functions as a transcription factor to induce expression of numerous genes, thereby regulating many physiological or pathological activities, from cell proliferation, tumorigenesis, to neurodegenerative disorders. However, the ligand-independent function of AR was unknown and the role of AR in programmed cell death is also incompletely understood. Recently, we uncovered that AR can promote UV-induced pro-death activity of the Bcl-2 family protein Bax through its non-transcription activity, but inhibits tumor necrosis factor (TNF1)-induced pro-death activity of the MAP kinase JNK through its transcription activity. We hypothesize that AR has dual regulatory role in programmed cell death: promoting or inhibiting apoptosis in a death stimulus-dependent manner. In this proposal, we will first determine the mechanism by which AR promotes Bax-dependent cell death through its non-transcription activity. To this end, we will define the AR pro-death domain(s) that is sufficient to promote Bax pro-death activity and determine whether AR regulates the interaction between Bax and other Bcl-2 family members, thereby promoting Bax activation. Finally, we will study whether specific AR-dependent Bax-associated proteins are involved in AR-mediated cell death, and determine whether the promotion of Bax activity by AR sensitizes cell death in animal model. Next, we will determine the mechanism by which AR inhibits TNF1-induced, JNK-dependent cell death through its transcription activity. To this end, we will determine how androgen/AR via induction of p21 inhibits TNF1-induced JNK activation and whether inhibition of JNK activity by androgen/AR occurs in animal model. We will determine whether in addition to inhibition of JNK, androgen/AR suppresses TNF1-induced cell death through inhibition of other component(s) in the death machinery. Finally, we will determine how differential regulation of JNK and Bax by AR is integrated for suppressing TNF1- induced cell death. Our long-term goal is to uncover the molecular mechanism underlying the ligand-independent function of AR and its differential regulation of programmed cell death, thereby providing molecular basis for developing novel strategies to treat human diseases related to dysregulation of AR function. PROJECT NARRATIVE: The androgen receptor involves many physiological or pathological activities, from cell proliferation, tumorigenesis, to neurodegenerative diseases. In this proposal, we will study molecular mechanisms underlying the non-transcription function of AR and its dual regulatory roles in cell death in response to different death stimuli. This study should provide invaluable information for developing novel strategies for prevention and treatment of human diseases, such as prostate cancer and spinal and bulbar muscular atrophy. [unreadable] [unreadable] [unreadable]

? DESCRIPTION (provided by applicant): Expression of the pro-apoptotic tumor suppressor Bax can be silenced by frameshift mutations in its microsatellite coding region, leading to a Bax-negative phenotype. Such Bax mutations occur in ~50% of hereditary nonpolyposis colorectal cancer (HNPCC) due to deficiency of mismatch repair system associated microsatellite instability (MSI). Loss of Bax has been demonstrated to increase chemoresistance and is associated with poor prognosis. Recently, we found that some Bax-negative tumor cells actually contain a functional Bax isoform, Bax?2, which is generated when alternative splicing corrects the mutation-induced frameshift. Therefore, Bax?2 only exists in microsatellite-mutated cells. We have demonstrated that this salvaged Bax?2 is pro-death, similar to prototype Bax, but induce cell death potential through a non- mitochondrial death pathway. Importantly, colon cancer cells expressing Bax?2 are more sensitive to selected chemotherapeutics. Therefore, we hypothesize that Bax?2 determines tumor malignant potential and chemotherapeutic selectivity in Bax-negative MSI colorectal cancer cells through a non-canonical Bax- death pathway. We have two specific aims: 1) to study the mechanism underlying Bax?2-mediated cell death; and 2) to identify key regulators responsible for controlling Bax?2 expression levels in MSI colorectal tumor cells. Since there was no awareness of the existence of a Bax isoform in the Bax-negative cancer prior to this study, we think the studies proposed in this grant application are conceptually innovative and significant because they will change the current paradigm for understanding the development and prognosis of the Bax-negative MSI colorectal cancer and facilitating selection of specific chemotherapeutics for this subgroup of Bax-negative colon cancer patients. The Illinois Institute of Technology (IIT) is a private university with a wide range of academic disciplines. The University encourages biological research and promotes integrative biomedical research with potential translational impact. IIT currently lacks several biomedical facilities, such as high-level genomic and imaging facilities, a full-featured animal facility, and clinical resources. However, IIT does have a large body of undergraduate and graduate students eager to participate in biomedical research. The PI has a strong academic credential for both education and research. The proposed project is carefully designed to exploit the strengths of IIT's research environment and maximize opportunities for student hands-on research experiences. Successful completion of the proposed studies will have a substantial positive impact on IIT's biomedical research capacity.