Characterization of fibroblast growth factor receptor 1 in small-cell lung cancer

There remains a significant therapeutic need for small-cell lung cancer (SCLC). We and others have reported high frequency of copy number gains in cytogenetic bands encoding fibroblast growth factor receptor 1 (FGFR1) in SCLC tumors and cell lines.

Thirteen SCLC cell lines and 68 SCLC patient tumor samples were studied for FGFR1 amplification. Growth inhibition assays were performed using PD173074, a pan-FGFR inhibitor to determine the correlation between FGFR1 expression and drug sensitivity.

We did not detect FGFR1 mutations in SCLC cell lines. Focal amplification of FGFR1 gene was found in five tumor samples (7%), with high-level focal amplification in only one tumor sample (1%). Amplification owing to polysomy of chromosome 8, where FGFR1 locates, was observed in 22 tumor samples (32%). There was no correlation between FGFR1 gene copy number and messenger RNA expression or protein expression in SCLC cells. FGFR inhibitor sensitivity correlated with FGFR1 copy number determined by real-time polymerase chain reaction assay (r= -0.79; p = 0.01).

FGFR1 gene mutations and focal amplification are rare in SCLC, but polysomy of chromosome 8 is relatively common. FGFR1 copy number gain predicts sensitivity to FGFR inhibition, and FGFR expression correlates inversely with chemosensitivity.