SOX2 expression is associated with FGFR fusion genes and predicts favorable outcome in lung squamous cell carcinomas

OBJECTIVES SOX2 is a gene that encodes for a transcription factor, which functions as an activator or suppressor of gene transcription. SOX2 amplification and overexpression have been found in various types of tumors and play important roles in cancer cells. The aim of the study was to evaluate SOX2 expression and amplification in lung squamous cell carcinomas (SCCs) and to determine the relationship with main clinicopathologic features, patient prognosis, and common driver mutations. MATERIALS AND METHODS SOX2 protein levels were measured by immunohistochemistry, while SOX2 copy numbers were measured by fluorescence in situ hybridization in resected samples from 162 Chinese lung SCC patients. All patients were also analyzed for mutations in EGFR, HER2, BRAF, PIK3CA, NFE2L2, and FGFR fusion genes. Clinical characteristics, including age, sex, smoking status, stage, relapse-free survival (RFS), and overall survival (OS), were collected. RESULTS SOX2 overexpression and amplification were observed in 58.6% and 45.9% of lung SCCs. Lung SCC patients with SOX2 overexpression were significantly associated with absence of malignant tumor family history (P=0.021), FGFR fusion gene (P=0.046), longer RFS (P=0.041), and OS (P=0.025). No correlation was found between SOX2 gene amplification and main clinicopathologic features, patient prognosis, or common driver mutations. CONCLUSION SOX2 overexpression and amplification are common in lung SCCs. SOX2 over-expression was associated with FGFR fusion genes and predicted favorable outcome in lung SCCs. The underlying relationship of SOX2 and FGFR still needs further investigation.