Abstract 1997: FAK inhibition induced FAK nuclear localization targets both tumor growth and angiogenesis
Authors: Rodriguez Yelitza , Murphy James , Jeong Kyuho , Erin Ahn , Lim Steve 
Published: July 2021

Tumors are not a cell-autonomous event, as most tumors include non-neoplastic stromal cells, so-called tumor microenvironment (TME). The TME is the tumor's immediate surroundings that comprise various types of cells and soluble factors, which stimulate bidirectionally via dynamic paracrine signaling supporting primary tumor progression. Among them, endothelial cells (ECs) significantly contribute to promoting tumor growth and metastasis through their ability to establish tumor vessels. Most cancer therapies have been centered on targeting altered signaling in tumor cells to prevent cancer growth, largely ignoring the importance of the TME. Identifying key signaling pathways that simultaneously prevent both tumor growth and angiogenesis may provide a new therapeutic strategy for various cancers. Focal adhesion kinase (FAK) is an integrin associated protein tyrosine kinase, which is frequently overexpressed in advanced human cancers. Small molecule FAK catalytic inhibitors (FAK-I) are currently being tested in clinical trials as anticancer agents. We found that kinase-inhibited FAK forces FAK nuclear localization in cancer cells. Although the role of nuclear FAK is not fully understood, several studies have shown that nuclear FAK may regulate gene expression. Using B16 melanoma ear tumor model, we found that FAK-I efficiently reduced B16 tumor lesions and tumor angiogenesis. While vehicle-treated mice exhibited high cytoplasmic FAK levels, FAK-I-treated mice exhibited robust FAK nuclear localization within B16 tumor cells and the TME. As FAK-I affects the FAK activity in both tumor cells and the TME, we attempted to dissect respective molecular mechanisms by which nuclear FAK contributes to the reduction in tumor growth and angiogenesis. From RNA sequencing data analysis from FAK-I treated cancer cell lines, we found that FAK inhibition significantly upregulated gene sets involved in cell cycle regulation, including CDK inhibitor p21. Increased expression of p21 in FAK-I treated B16 cells was confirmed using RT-qPCR, immunoblotting, and immunostaining. Prolonged FAK-I treatment increased B16 cell apoptosis both in vitro and in vivo compared to vehicle group. To address if FAK-I also blocks angiogenesis in vivo, we performed a Matrigel plug assay and found that FAK-I significantly reduced VEGF/FGF-stimulated angiogenesis. FAK-I treatment promoted nuclear FAK localization in vitro and in vivo ECs, suggesting that nuclear FAK in ECs inhibits cell proliferation and migration required for angiogenic activity. Using EC-specific FAK kinase-dead mouse, we confirmed that nuclear FAK in ECs is responsible for reducing angiogenic activity in the Matrigel plug model. Together, these results indicate that nuclear FAK induced by FAK-I can be used as a promising therapeutic strategy simultaneously targeting both tumor growth and angiogenesis.

Citation Format: Yelitza Rodriguez, James Murphy, Kyuho Jeong, Ahn Erin, Steve Lim. FAK inhibition induced FAK nuclear localization targets both tumor growth and angiogenesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1997.