GASC1 expression in lung carcinoma is associated with smoking and prognosis of squamous cell carcinoma.

Abstract

GASC1 (gene amplified in squamous cell carcinoma 1) encodes a nuclear protein that epigenetically catalyses the lysine demethylation of histones. We investigated the expression of GASC1 in different histological subtypes of lung cancer (n=289). Percentage value of GASC1 immunohistochemical expression was evaluated separately in the nuclei and cytoplasms of epithelial cancer cells. The results were compared with clinicopathologic factors and the smoking history of the patients. In lung tumor cells, 38% of nuclei and 54% of the cytoplasms stained positive for GASC1. Adenocarcinomas expressed more GASC1 nuclear (p=0.00011) and cytoplasmic (p=0.00074) positivity than squamous cell carcinoma. Smokers displayed less nuclear and cytoplasmic GASC1 expression than non-smokers (p=0.028 and p=0.036, respectively). Similarly, patients with more cytoplasmic positive staining had fewer pack years (p=0.043). Nuclear GASC1 expression had an impairing effect on survival when all histological lung cancer types were analysed together (p=0.039) and separately in squamous cell lung carcinoma (p=0.016). The results reveal that GASC1 expression is higher in adenocarcinoma than squamous cell carcinoma. Smoking decreases GASC1 expression in tumor cells, indicating that tobacco smoke may influence the methylation of histone 3 lysine residues in lung cancer. Nonetheless, nuclear GASC1 predicts a poor prognosis, especially in squamous cell carcinoma.