Abstract 2507: Axl suppression inhibits cell migration, invasion and survival in breast and prostate cancer cell lines

Abstract

Abstract Cancer is the second leading cause of death in the United States with approximately 90% of cancer-related deaths resulting from metastatic disease. In tumor cells, upregulation of certain signaling pathways promote metastatic phenotypes characterized by enhanced invasion, migration, survival, proliferation and induction of angiogenesis. One pathway of considerable interest involves the receptor tyrosine kinase Axl that is expressed in a variety of tumor types and is associated with poor prognosis and metastasis. Furthermore, Axl's ligand, Growth arrest specific 6 (Gas6) protein, can activate a number of downstream signaling pathways that promote metastatic phenotypes. The purpose of the current study was to characterize Axl and Gas6 in a number of human tumor cell lines and to determine the effect of Axl suppression on the metastatic phenotypes, specifically cell migration, invasion and survival. A panel of human tumor cell lines, including prostate, breast, colorectal, renal, and osteosarcoma, were characterized for Axl expression by Western blot and qPCR. Gas6 expression was assessed by qPCR and Gas6 secretion was determined in conditioned media by ELISA. Axl was genetically inactivated by shRNA in prostate (DU145) and breast (MDA-MB-231) cancer cell lines. The efficiency of knockdown was determined by Western blot. The effect of Axl knockdown on the migratory and invasive potentials of these cell lines was evaluated by transwell migration and invasion assays. A clonogenic cell survival assay was used to assess the impact of Axl knockdown on tumor cell viability. Axl-expressing tumor cells expressed and secreted its ligand Gas6, suggesting that Axl is co-expressed with Gas6, and may be mediated by autocrine regulation. Genetic inactivation of Axl (shRNA) inhibited cell migration, invasion and reduced clonogenic cell survival in both the MD-MB-231 breast and DU145 prostate cancer cell lines. These findings suggest that Axl may be a novel therapeutic target to inhibit the dissemination of tumor cells. Ongoing experiments are evaluating the impact of the Axl-targeting agent R428 on Axl signaling and metastatic phenotype. Citation Format: Mai Tanaka, Samantha S. Dykes, Dietmar W. Siemann. Axl suppression inhibits cell migration, invasion and survival in breast and prostate cancer cell lines [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2507.