Objective  ASCL-1 gene expression is closely related to pulmonary neuroendocrine (NE) tumors, such as small cell carcinoma, atypical carcinoid, carcinoid, and large cell NE carcinoma. This study aimed to analyze ASCL-1 protein expression in lung adenocarcinoma (AD) and its correlation with prognosis.

  Methods  ASCL-1 protein expression in 283 cases of AD was determined through immunohistochemical analysis and compared with the expression of traditional NE markers, including chromogranin A, CD56, and synaptophysin. Western blot was performed to detect the ASCL-1 protein expression levels in AD. Single factor Chi-square test and Logistic multiple factor regression analysis were conducted to explore the factors related to ASCL-1 expression. Kaplan-Meier survival analysis was applied to evaluate the prognosis of patients with AD.

  Results  Immunohistochemical analysis showed that ASCL-1 expression was positive in 48/283 (16.9%) AD and positively correlated with NE markers (0 < r < 1, P < 0.05). Western blot revealed that ASCL-1 protein was expressed in 63 cases of AD, in their tumor-adjacent normal samples, and in 9 cases of AD. By contrast, this protein was not expressed in tumor-adjacent normal tissues. Single factor Chi-square test and multivariate logistic regression analysis indicated that ASCL-1 protein expression was associated with smoking, tumor differentiation, TNM staging, and lymph node metastasis. Kaplan-Meier survival analysis demonstrated that overall survival (OS) time was shorter in the ASCL-1-positive group than in the ASCL-1-negative group (P < 0.05).

  Conclusion  ASCL-1 protein expression may serve as an independent prognostic factor for patients with lung AD.