Abstract LB-24: LPA-mediated oncogenic signaling in ovarian cancer involves p130Cas

Ovarian cancer is the most deadly gynecological cancer and the need for new therapies is evidenced by the fact no new drugs targeting ovarian cancer have been identified. Recent studies have shown that lysophosphatidic acid (LPA), a lipid growth factor, is implicated in the genesis and progression of ovarian cancer, yet the majority of the mechanisms through which LPA promotes cancer genesis and progression remain to be elucidated. Therefore, the underlying theme of our research is to identify novel LPA-activated signaling nodes that can be targeted for therapy in ovarian cancer. Subjecting the lysates from HeyA8 ovarian cancer cells to a high-throughput antibody array analysis, we identified that LPA potently stimulates the tyrosine-phosphorylation of p130Cas, a scaffolding protein, which, upon phosphorylation, recruits an array of signaling molecules that promotes tumor cell proliferation, survival and metastasis. The antibody-array data was validated via immunoprecipitation of p130Cas and immunoblotting with a phospho-tyrosine specific antibody in a panel of ovarian cancer cells consisting of HeyA8, OVCA429, OVCA432 and SKOV3, establishing cell-type independent activation of p130Cas by LPA. Analyzing further, we have identified that tyrosine-410 of p130Cas is phosphorylated in response to LPA. Several past studies, including ours, have shown oncogenic signaling by LPA involves the activation of LPA receptors that are coupled to the α-subunits of the heterotrimeric G proteins, Gi, Gq, G12, and/or G13. To define the specific α-subunit that mediates LPA-induced p130Cas-phosphorylation, we monitored Tyr-410 phosphorylation of p130Cas in response to 20 μM of LPA (20 min) in HeyA8 cells in which the expression of Gαi2, Gαq, Gα12, or Gα13 was silenced by specific shRNAs. Our results indicated that only the silencing of Gαi2 abrogated LPA-mediated Tyr-410 phosphorylation of p130Cas. Since Gαi2 has been shown to play a critical role in LPA-LPAR coupled cell migration, we hypothesized that the LPA-LPAR-Gαi2-p130Cas signaling axis is involved in the invasive migration of ovarian cancer cells. To test this hypothesis, we examined whether the knocking down of p130Cas, via p130Cas-specific siRNA, attenuated LPA-mediated migration of ovarian cancer cells. Our results indicated that the silencing of p130Cas significantly inhibited LPA-stimulated migration of ovarian cancer cells by 58%. Thus, our study is the first to establish LPA-LPAR-Gαi2-mediated stimulation of p130Cas is involved in invasive migration of ovarian cancer cells. Overall, the results presented in our current study point to p130Cas as a critical signaling node in pathological LPA signaling and that by targeting LPA receptors, LPA production and/or the downstream kinases that phosphorylate p130Cas, it may be possible to disable the oncogenic signaling cascades activated by p130Cas in ovarian cancer and enhance the survival of ovarian cancer patients. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr LB-24. doi:1538-7445.AM2012-LB-24