Relationship of aquaporin 1, 3, and 5 expression in lung cancer cells to cellular differentiation, invasive growth, and metastasis potential

Abstract

An oncogenic capacity of aquaporins, transmembrane channels for water, was recently proposed. This study seeks to elucidate the involvement of aquaporin 1, 3, and 5 in the development and progression of lung cancer. Expression of aquaporin 1, 3, and 5 was examined by immunohistochemistry, Western blot, and laser-captured microdissection/real-time reverse transcription polymerase chain reaction in 160 lung cancers of various histologic subtypes; and its correlation with clinicopathological factors and survival was analyzed. Aquaporin 1, 3, and 5 were expressed in tumor cells in 71%, 40%, and 56% of lung cancers, respectively. Aquaporin expressions were frequent in adenocarcinomas, whereas aquaporin 1 and 5 were negative in squamous cell carcinomas. Bronchioloalveolar carcinoma cells exhibited an apicolateral aquaporin 1 and apicolateral or basolateral aquaporin 3 localization in nonmucinous type, and apical aquaporin 1 and 5 and basolateral aquaporin 3 expression in mucinous type, which corresponded to aquaporins expression of nonneoplastic lung tissue. Basolateral aquaporin 5 expression was acquired during tumorigenesis of nonmucinous bronchioloalveolar carcinoma. In contrast, invasive adenocarcinoma tumor cells overexpressed aquaporin 1 and 5 with loss of subcellular polarization and with an intracytoplasmic distribution. Overexpression of aquaporin 1 correlated with high postoperative adenocarcinoma metastasis ratios and unfavorable disease-free survival rates (P = .031). We conclude that expression patterns of aquaporin 1, 3, and 5 in lung cancer cells are mostly associated with cellular differentiation. However, the expression of aquaporin 1 and 5 is up-regulated in invading lung cancer cells, particularly in adenocarcinomas; and the overexpression of aquaporin 1 with loss of subcellular polarization is suggested to be involved in their invasive and metastatic potential.