Expression and clinical significance of the Trop-2 gene in advanced non-small cell lung carcinoma

Abstract

The Trop-2 gene has been examined in various carcinomas and is reported to be significantly associated with prognosis. Little is known with regard to Trop-2 gene expression in advanced non-small cell lung carcinoma (NSCLC). The present study investigated the expression of Trop-2 and its association with the prognosis of advanced NSCLC. The clinical records of 87 patients with advanced NSCLC, consisting of 37 cases of squamous cell carcinoma (SCC) and 50 cases of adenocarcinoma (AdC), together with 17 tumor-adjacent normal tissues, were retrospectively evaluated. Trop-2 expression was measured using an immunohistochemical method and its association with clinicopathological data and prognosis was also evaluated. The expression of Trop-2 was significantly higher in the cancer tissues compared with the tumor-adjacent normal tissues, and significantly higher in SCC compared with AdC (P=0.018). In SCC, the overexpression of Trop-2 was only correlated with the histological grade of the tumor (P= 0.035) and no correlation was observed with gender, age, lymph node metastasis, TNM stage or Eastern Cooperative Oncology Group (ECOG) performance status (PS). In AdC, the over-expression of Trop-2 was correlated with the histological grade, lymph node metastasis and TNM stage (P= 0.01, 0.024 and 0.015, respectively), while no correlation with gender, age or ECOG-PS was observed. The survival frequency was significantly higher in the Trop-2-negative patients compared with the Trop-2-positive patients [17.25 months (95% CI, 14.922–19.577) vs. 13.274 months (95% CI, 11.507–15.041); P= 0.008]. The survival time was significantly longer in the Trop-2-negative AdC patients [17.275 months (95% CI, 14.575–19.975) vs. 11.469 months (95% CI, 11.507–15.041); P= 0.002], but not in the SCC patients [17.167 months (95% CI, 12.428–21.906) vs. 14.647 months (95% CI, 12.062–17.232); P= 0.276]. The multivariate analysis revealed that Trop-2 expression [hazard ratio (HR) 2.381; P= 0.038], TNM stage (HR, 2.193; P= 0.03) and ECOG-PS (HR, 2.696; P= 0.007) were independent predictors for the survival outcome of patients with AdC. These results suggest that Trop-2 overexpression is closely correlated with an unfavorable prognosis in advanced NSCLC. Trop-2 is an independent prognostic marker and a potential new therapeutic target in advanced AdC.