Fibroblast growth factor receptor 1 (FGFR1) gene copy number gain in adenocarcinoma and squamous cell carcinoma of the lung.

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7552 Background: FGFR-1 is a novel target for therapy in non-small cell lung carcinoma (NSCLC). FGFR1 gene has been shown to be amplified in ~20% of squamous cell carcinomas (SCC) of the lung. The frequency of FGFR1 copy number gain (CNG) and gene amplification (GA) in lung adenocarcinoma (AC) is unknown, and the clinicopathological and molecular characteristics of the NSCLC tumors with FGFR1gene increase have not been fully described. Methods: We examined FGFR1 gene copy number (GCN) by fluorescent in-situ hybridization (FISH) and FGFR1 protein expression by immunohistochemistry in 475 surgically resected NSCLCs (162 SCCs, and 313 ACs) stages I-III in tissue microarrays. Three FGFR1 FISH categories were identified: a) no CNG; b) CNG, defined as ≥4 gene copies in ≥40% of cells; c) GA, defined as ratio of copies of FGFR1:CEP8 ≥2 or presence of tight gene clusters in ≥10% of cells. FGFR1 protein expression in the cytoplasm and membrane of tumor cells was quantified using H score. Results: FGFR1 GA was detected only in SCCs (14 cases, 9%). CNG was detected in both SCC (39 cases, 24%) and AC (80 cases, 26%). In AC, significantly higher frequency of CNG was detected in patients with smoking history (P=0.008) and in tumors with low differentiated histology (P=0.0005). No correlation was detected between FGFR1 CNG and mutation of KRAS and EGFR in AC. In SCC, tumors with FGFR1 CNG/GA had higher cytoplasmic FGFR1 protein expression than those with no copy changes (49±39 vs. 26±21, P<0.001), and the protein expression correlated with GCN (R=0.55; P<0.001). In multivariate analysis, patients with stage I/II SCCs having FGFR1 gene copy ≥6 or GA showed a significantly better overall survival (HR=0.26; 95% CI: 0.08-0.84, P=0.02) than patients with <6 gene copy, after adjusting for smoking, gender and tumor size. An increase on FGFR1copy number was detected in 8/45 (18%) brain metastasis compared with primary tumors. Conclusions: In NSCLC, FGFR1 GA occurs only is a small subset of SCCs (9%), whereas CNG is a relatively frequent phenomenon in both SCC (24%) and ACs (25%). FGFR1 copies ≥6 or GA is associated with better outcome in patients with surgically resected stages I/II SCCs of the lung.