Fer Protein-Tyrosine Kinase Promotes Lung Tumor Progression And Metastases

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL FER is a ubiquitously expressed non-receptor protein-tyrosine kinase implicated in regulating cell-cell and cell-matrix interactions, cell growth and migration. Although no activating mutations have been described for FER, recent studies implicate FER as a positive regulator of cancer progression in the prostate and liver. FER is composed of Fer/CIP4 homology-Bin/Amphiphysin/Rvs (F-BAR), extended F-BAR (FX), SH2, and kinase domains. FER oligomerization and membrane targeting is conferred by F-BAR/FX domains, while the SH2 domain allows FER recruitment to tyrosine phosphorylated ligands, including activated Epidermal growth factor (EGF) receptor (EGFR). Since gene amplification or gain-of-function mutations in EGFR are frequently observed in non-small cell lung carcinoma (NSCLC), we tested whether FER participates in EGFR-driven NSCLC migration, progression, and metastases. Here we show that FER is expressed in normal lung epithelial cells and at variable levels in NSCLC cell lines. In a panel of NSCLC homogenates we observed 5 out of 12 cases of increased FER expression over normal adjacent tissue. Furthermore, in a tissue microarray containing a range of lung cancer histological types we observed high FER expression in the NSCLC adenocarcinoma subtype and in SCLC. In human lung epithelial carcinoma H1299 cells that overexpress wild-type EGFR, we detected rapid EGF-induced activation of FER, and subsequent phosphorylation of several putative FER substrates including STAT3, Cortactin, and Vav2. To probe the function of FER, we used a lentiviral shRNA system to achieve stable knock-down (KD) of FER in H1299 cells. Compared to control cells, FER KD cells displayed a significant reduction in EGF-induced migration in scrape wound assays. FER KD cells were also defective in frequency and velocity of invasion under an agarose drop containing EGF. Of the putative FER substrates tested, we observed a significant decrease in Vav2 phosphorylation in Fer KD cells. Since Vav2 promotes Rac activation, we compared localization of active, GTP-bound Rac1 in control and FER KD cells treated with EGF. Interestingly, FER promotes localization of GTP-Rac1 to the leading edge of these cells. To test the role of FER in NSCLC progression and metastasis, H1299 vector control and FER KD cells were grown as subcutaneous tumors in immune compromised mice (Rag2-/-γc-/-) for four weeks. Although we observed no significant differences in tumor mass for FER KD cells compared to control, the potential role of FER in metastasis is currently under investigation. Together, this study may implicate FER as a viable new therapeutic target for treatment of EGFR-driven metastasis of lung cancers. 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 462. doi:1538-7445.AM2012-462