The PI3K/PTEN pathway is a critical regulator of cell-death and cellular proliferation. The PTEN tumor suppressor gene is mutated in a significant number of prostate tumors, and we have shown that loss of the PTEN protein is associated with high Gleason grade tumors. PTEN loss leads to activation of the Akt kinase. Akt in turn phosphorylates and inhibits a number of downstream targets including BAD, Caspase 9, GSK-3, and the forkhead transcription factors AFX, FKHRL1 and FKHR. Preliminary data suggests that in the absence of PTEN, forkhead transcription factors are deregulated and that restoring Forkhead function is sufficient to suppress the growth of PTEN null tumor cells. Thus, these factors are likely critical regulators of growth suppression downstream of PTEN. Based upon this work, this project aims to study the role of this pathway in the transforming murine prostate epithelial cells.
In aim 1, constitutive activation of Akt in the murine prostate will be achieving using transgenic approaches. Transgenic animals expressing activated Akt in the prostate will be analyzed for the development of approaches. Transgenic animals expressing activated Akt in the prostate will be analyzed for the development of murine tumors. These animals will be analyzed and compared with animals generated by the Roberts and Cantley labs buy array analysis. Here, the goal will be to dissect this pathway in vivo using transcriptional profiling to identify concordant or divergent transcriptional targets.
In aim 2, we will determine whether dominant-negative FKFR is sufficient for inhibition of FKHR function in cells and if so, whether FKHR is necessary for PTEN function in regulating growth. Dominant-negative FKHR will be expressed in the murine prostate to ask whether inhibition of FKHR activity is sufficient for transformation.
In aim 3, in conjunction with the Robert's lab we will study the activation status of this pathway in human tumors do determine whether PTEN loss is accompanied by FKHR relocalization to the cytoplasm, by IGFI-R receptor activation, and be deregulation of the cyclin-dependent kinase inhibitor p27.
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