This application focuses on a novel signaling link that could have significant implications for chemoprevention and personalized therapy for prostate cancer. Specifically, we identified a functional link between the oncogenic kinase PKC? and inducible cyclooxygenase-2 (COX-2). Studies demonstrated a clear association between COX- 2 up-regulation in primary tumors, development of metastasis, and poor patient survival. There is significant evidence that inhibition of COX isoforms with non-steroidal anti-inflammatory drugs reduces risk of human cancers. In addition, COX-2 inhibitors inhibit proliferation and trigger apoptosis in prostate cancer cells, and impair prostate tumor growth in mouse models. PKC? is markedly up-regulated in prostate cancer and other cancers, and it controls key mitogenic/survival pathways such as Erk, Akt, Stat-3 and NF-?B. We generated a prostate-specific transgenic mouse model for PKC? (PB-PKC?), which develops prostatic intraepithelial neoplasia (PIN) lesions. Most remarkably, in a Pten-deficient (+/-) background, PKC? transgenic mice develop invasive prostate adenocarcinomas with Akt and NF-?B hyperactivation, and COX-2 up-regulation. Prostate epithelial cellular models engineered to recapitulate PKC? overexpression and Pten loss (i.e. PI3K hyperactivation) acquire tumorigenic potential in nude mice, become highly invasive, display COX-2 up- regulation and elevated PGE2 production (which has been linked to prostate cancer), and become highly sensitive to the killing effect of a COX-2 inhibitor.
In Specific Aim 1 the main goal is to determine if COX-2 mediates PKC?-driven tumorigenesis using a number of approaches, including COX-2 shRNA silencing in PKC? expressing/Pten depleted cells orthotopically implanted in mouse prostates, treatment of PB-PKC? mice with COX-2 inhibitors, and the generation of a mouse model for prostate-specific COX-2 gene deletion in the context of PKC? overexpression.
In Specific Aim 2 we will dissect the functional relevance of a link we recently identified between PKC? and the inducible PGE2 synthase mPGES-1. A dual mouse model for prostate specific PKC? overexpression in a mPGES-1-null background will be generated. The role of PGE2 (EP) receptors in driving an autocrine tumorigenic vicious cycle will be mechanistically dissected.
In Specific Aim 3 we will test the hypothesis that specific p110 PI3K isoforms mediate COX-2/mPGES-1/PGE2 induction in prostate models and the tumorigenic phenotype driven by PKC? overexpression/Pten loss. Finally, to add prognostic and translational value to our studies, in Specific Aim 4 we will take advantage of a large collection of human prostate cancer specimens to determine if correlations exist between PKC? overexpression and COX-2/mPGES-1 induction. Samples with different Gleason grades, disease recurrence after prostatectomy, and castration-resistant (CRPC) disease will be used. In addition to the significant mechanistic, prognostic and therapeutic implications, our studies may provide proof-of-principle for the use of inhibitors of the COX-2/mPGES-1/EP receptor pathway for the prevention and treatment of subsets of prostate cancer patients with defined oncogenic alterations.
This application will focus on novel signaling mechanisms leading to prostate tumor progression mediated by the pro-oncogenic kinase protein kinase C epsilon (PKC?). We found that PKC?, which is markedly up-regulated in prostate cancer, cooperates with the loss of the tumor suppressor Pten to promote invasive prostate cancer. PKC? overexpression and Pten loss cooperate to enhance growth, migration and invasiveness in cellular models. Analysis of the mechanisms implicated in this effect suggests the involvement of the NF-?B-regulated gene COX- 2 and its product prostaglandin E2 (PGE2) in these effects, and that PKC? mediates the induction of COX-2 and the PGE2 synthase mPGES-1 in prostate cancer. We will use cellular and animal tumor models generated in our laboratory to investigate how PKC? in conjunction with Pten loss/PI3K hyperactivation drive the tumorigenesis phenotype via COX-2, mPGES-1 and PGE2 induction, and correlate our findings with disease progression using human prostate cancer specimens. The proposed studies have significant mechanistic implications for understanding prostate tumor progression and deciphering effectors of a pro-oncogenic kinase.
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