Project 1: The Role and Mechanism(s) of MUC16 and MUC16-Cter in Potentiating PC Metastasis

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Abstract Pancreatic cancer (PC) is a highly metastatic and therapy-resistant malignancy with patients presenting with local and distant metastases at the time of diagnosis. Like other epithelial cancers, PC progression is characterized with aberrant mucin overexpression. Our previous study indicated that while MUC16 was undetectable in the normal pancreas, there was a progressive increase in MUC16 expression with the increase in grade of PanIN lesions, tumor and metastasis. We also demonstrated that MUC16 and MUC16-Cter play critical roles in metastasis of pancreatic cancer. However, functional and mechanistic involvement of MUC16 in pancreatic cancer metastasis remains poorly understood. MUC16 is a multi-domain protein that can potentially play multifaceted role in metastasis of PC. In our preliminary studies, silencing of MUC16 in PC cells resulted in reduced cell growth and migration along with alterations in EMT markers. We thus hypothesize that MUC16 is associated with PC metastasis, which, in part, is mediated by MUC16-Cter domain. To test the hypothesis and achieve the aforementioned objectives, three specific aims are proposed. First aim will evaluate the role of MUC16 in mediating cell-to-cell interactions during metastatic spread of PC cells. In this aim, we will analyze the cellular and molecular functions of MUC16 by analyzing cell-cell and cell-extracellular matrix interactions. These studies will provide insights into the role of MUC16 in facilitating the interaction of tumor cells with the endothelial cells, platelets and leukocytes during metastasis. Studies in Aim 2 will delineate the molecular mechanism(s) of MUC16-Cter-mediated PC metastasis and identify MUC16 interacting partners. Since MUC16-Cter is enriched in the chromatin bound fraction in the nucleus, its effect on global gene expression will be evaluated using ChIP- Seq analyses. Further, the effect of various point mutations affecting N-glycosylation, ubiquitylation and phosphorylation will be addressed in the light of its functional consequences. Third aim will investigate the cooperative action of MUC16 with other defined oncogenic mutations in the metastasis of PC using Muc16–/–and MUC16Cter transgenic mice. In this context, it is important to determine the role of MUC16, alone and in combination with oncogenic K-ras and p53, during PC development. To validate our in vitro findings of the role of MUC16 in PC, we will generate MUC16Cter transgenic with pancreas specific expression. Further, depending on the phenotypes of MUC16-Cter N-glycosylation, ubiquitylation and/or phosphorylation mutants, we will generate mutant specific transgenic to understand the in vivo relevance of such mutations. Overall the proposed studies will allow us to define the molecular mechanisms by which MUC16 and its Cter facilitate metastasis and contribute to the aggressiveness of PC. These novel insights into the underlying mechanisms of PC metastasis combined with the new data, reagents and models will provide novel avenues for targeting metastatic PC in future.