Expression and clinical significance of aminopeptidase N/CD13 in non-small cell lung cancer

Background: The objective of this study was to analyze the expression of aminopeptidase N/CD13 (APN/CD13) in non-small cell lung cancer (NSCLC) and investigate its correlation with various clinical factors, including prognosis and efficacy of adjuvant chemotherapy. Materials and Methods: Using immunohistochemistry analysis, we analyzed the expression of CD13 in clinicopathologically characterized 127 NSCLC cases. The relationship between the expression levels of CD13 and clinical features was analyzed and presented. Statistical Analysis: The data were analyzed using statistical package for the social sciences software (Ver 13.0, IBM, USA). Those conforming to Gauss distribution criteria was represented as Mean +/- SD and those not conforming to Gauss distribution criteria was represented as median (M). The overall survival was recorded from the date of surgery to the date of cancer-specific death. APN/CD13 expression levels and clinicopathological factors were analyzed by Chi-square test or by Fisher's exact test. The Kaplan-Meier method was used to evaluate the probability of survival data and analyzed by Log rank test. Multivariate analysis was performed by Cox regression model. P < 0.05 was considered to be statistically significant. Results: APN/CD13 was mainly expressed in the cellular membrane of cancer cells in pulmonary adenocarcinoma and in the cellular membrane of interstitial cells in squamous carcinoma. Positive APN/CD13 was detected in 62.3% (43 of 69) squamous carcinoma patients and in 50% (29/58) adenocarcinoma patients. Expression of APN/CD13 was not correlated with age, gender, tumor, node, metastasis (TNM) stage, histological type and tumor size, but with TNM stage (P = 0.041) and lymph node metastasis status (P = 0.009). As indicated by Kaplan-Meier survival curve, over-expression of APN/CD13 was significantly correlated with the low survival rate. Cox regression analysis showed that APN/CD13 expression was an independent impact factor for the survival of lung adenocarcinoma patients receiving adjuvant chemotherapy (P = 0.006). Conclusions: Expression of APN/CD13 is a potential unfavorable factor to predict the efficacy and prognosis of post-operative chemotherapy in NSCLC patients, especially in lung adenocarcinoma patients.