Clinical Significance of Aminopeptidase N in Non–Small Cell Lung Cancer

Purpose: The aim of our study is to investigate the mechanism of metastasis, to detect novel metastasis-associated molecules, and to evaluate the molecules from the point of view of clinical application. A monoclonal antibody MH8-11, which we established, recognizes a glycoprotein that is identical to aminopeptidase N (APN/CD13). APN/CD13 degrades the extracellular matrix, while it is also involved in cell motility and improves angiogenesis. Experimental Design: We investigated the expression of APN/CD13 in 194 cases of non–small cell lung cancer (NSCLC) by immunohistochemical analyses and reverse transcription-PCR assay to determine the significance of this prognostic factor; 95 tumors were stage I, 36 were stage II, 39 were stage IIIA, and 24 were stage IIIB. Moreover, we investigated that the relationship between the expression of APN/CD13 and angiogenesis and prognosis for patients with NSCLC. Results: We found a correlation between the expression of APN/CD13 and angiogenesis ( r = 0.659; P < 0.0001). In the 194 patients with NSCLC, we found 68 patients to be APN/CD13 + and 126 patients to be APN/CD13 − . The 5-year survival rate in patients with APN/CD13 + tumors was significantly lower than in those whose tumors had negative APN/CD13 (48.3% versus 67.1%; P = 0.0001). Conclusion: Our data suggest the expression of APN/CD13 for patients with NSCLC to be associated with a poor prognosis and angiogenesis. This is the first study to show the relationship between the expression of APN/CD13 and the prognosis of patients with NSCLC. The inhibition of APN/CD13 may be an effective new molecular target therapy for patients with NSCLC.