Expression of focal adhesion kinase in small-cell lung carcinoma.

Background: The focal adhesion kinase (FAK) is a non-receptor tyrosine kinase linked to tumor growth, invasion, and metastasis. FAK is overexpressed and associated with prognosis in many cancers, but its prognostic value in small-cell lung carcinoma (SCLC) is unknown and was the focus of this study.

Methods: Total FAK expression was analyzed via immunohistochemistry in tissue microarrays consisting of formalin-fixed, paraffin-embedded SCLC specimens from 85 patients. FAK staining scores were tested for correlations with pathological characteristics and clinical outcomes. Phospho-paxillin was also tested in 35 of the 85 specimens to evaluate whether FAK expression was associated with downstream signaling.

Results: Specific FAK expression was localized to the cytoplasm of 78/85 (92%) SCLCs. FAK expression was scored low in 11 (13%), moderate in 17 (20%), and high in 50 (59%) SCLCs. FAK staining scores treated as continuous variables did not correlate with SCLC disease stage, response to therapy, recurrence/progression-free survival, or overall survival. Moreover, total FAK expression did not correlate with phospho-paxillin Tyr(118) expression.

Conclusions: Total FAK is strongly expressed in a majority of SCLC tumors. However, the expression evaluated via immunohistochemistry is not a prognostic factor in patients with SCLC.