Abstract 2161: MLK3 signals to paxillin in chemokine-induced migration and invasion, and is necessary for breast cancer metastasis

Abstract

Abstract Breast cancer metastasis is the major cause for mortality of patients with invasive breast cancer. Metastasis involves multiple steps including cancer cell invasion through basement membrane, intravasation, survival in the circulation, extravasation and colonization of distant organs. Identification of the signaling pathways through which prometastatic factors promote cancer cell migration and invasion is key to develop effective therapeutics for breast cancer. Mixed lineage kinase 3 (MLK3) is a MAP3K involved in activating each of the three major MAPK signaling pathways. The MLK3-JNK-AP-1 signaling axis has been shown to be required in breast cancer cell migration and invasion. Herein, we demonstrate that the prometastatic factors, CXCL12 and HGF, signal through MLK3-JNK to induce phosphorylation of the focal adhesion scaffold, paxillin on Ser 178, which is required for migration and invasion of human breast cancer cells. Furthermore, we show that MLK3 regulates the phosphorylation of paxillin at Tyr 118 and promotes the interaction of FAK with paxillin, which can be blocked by inhibition of MLK3. To further understand the role of paxillin phosphorylation at S178, a nonphosphorylatable paxillin mutant S178 A was generated. Expression of S178A blocks Y118 phosphorylation of paxillin in breast cancer cells. Silencing of mlk3, inhibition of JNK, or expression of the nonphosphorylatable paxillin S178A increases focal adhesion numbers and increases Rho activity, suggesting that the MLK3-JNK-paxillin axis limits Rho activity in breast cancer cells. Furthermore, MLK3 silencing is sufficient to prevent formation of metastases in a mouse xenograft model of spontaneous breast cancer metastasis. Our findings have identified a novel role of MLK3 in regulation of focal adhesion dynamics and cytoskeletal remodeling in the process of breast cancer cell migration and suggest that MLK3 may be a potential therapeutic target for metastatic breast cancer. 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 2161. doi:1538-7445.AM2012-2161