Role of MLK3 in beta catenin signaling in prostate cancer

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DESCRIPTION (provided by applicant): An intricate balance between cell survival and cell death pathways maintains normal growth and homeostasis in any organism, loss of which can result in serious pathological abnormalities. Understanding of the regulatory mechanisms controlling these processes is important and might allow us to manipulate them for therapeutic interventions. The role of protein kinases in regulating cellular processes has been well documented, dysregulation of which can lead to various pathological disorders. Earlier studies by our collaborators demonstrated that activation of a kinase known as mixed lineage kinase 3 (MLK3) can induce apoptosis in cancer cells, indicating the possibility of utilizing MLK3 agonists as chemotherapeutic agents. Our recent studies showed that 1) MLK3 is expressed in prostate cancer cells, 2) overexpression of MLK3 results in a significant stabilization of ectopic p-catenin, which requires MLK3 kinase activity, 2) SiRNA mediated knockdown of MLK3 reduces endogenous p-catenin levels, 3) MLK3 synergizes with p-catenin to inhibit NFicB activity, and 4) coexpression of MLK3 increases p-catenin mediated apoptosis in prostate cancer cells. The major goal of this proposal is to determine whether p-catenin is involved in MLK3 mediated prostate cell apoptosis, and to elucidate the pathway involved. This is based on the fact that overexpression of p-catenin can lead to apoptosis independent of TCF/LEF transactivation pathway. In fact, MLK3 mediated stabilization of p-catenin inhibits conventional TCF/LEF mediated and NFxB mediated transcription. Since NFxB is a major survival pathway in prostate cancer cells, we hypothesize that MLK3 mediated signaling to p-catenin inhibits NFxB pathway leading to apoptosis. To achieve our goals two aims are proposed: (1) To determine the effect of activation of MLK3/p-catenin signaling in prostate cancer cells, (2) To elucidate the pathway of MLK3 mediated p-catenin signaling in prostate cancer cells. These studies will be performed utilizing various techniques including SiRNA, apoptosis assays, luciferase assay, immunoprecipitation, Western Blotting, immunohistochemistry. Since there is no information available regarding the mechanism how MLK3 induces apoptosis, these studies are expected to shed light into this very novel pathway, which can be utilized towards the future development of drugs for the treatment of prostate tumors based on MLK3 activation.