Expression of CD44 in primary lung carcinomas using histological and cytological analyses.

CD44 is a family of transmembrane glycoproteins expressed in hematopoietic and epithelial cells, and associated with diverse physiological functions such as cell-cell and cell-matrix interactions. CD44 exists in a standard form, CD44s, and in multiple isoforms which are produced by alternative splicing of the variant exons (exon v1 to exon v10) encoding parts of the extracellular domain. Recently, CD44 was shown to play a role in the invasive and metastatic properties of tumor cells. In this study, we demonstrated CD44 immunoreactivities in 74 primary lung carcinomas. CD44s was noted in 38% (28 out of 74) of primary lung carcinomas. CD44v3 (38%, 28 out of 74) and CD44v6 (41%, 30 out of 74) were less frequently expressed in the primary lung carcinomas, compared with non-neoplastic lung tissues (CD44v3, 100%, p < 0.001; CD44v6, 73%, p < 0.05), respectively. CD44v3 and CD44v6 were more frequently found in squamous cell carcinomas than the other histological types (p < 0.05). CD44s, CD44v3 and CD44v6 were noted in 33% (6 out of 18), 44% (8 out of 18) and 33% (6 out of 18) of cytology-positive cases, and in 46% (6 out of 13), 38% (5 out of 13) and 31% (4 out of 13) of cytology-negative cases, respectively. It is suggested that decreased CD44v3 and CD44v6 might be correlated with sputum cytology-negative cases of lung adenocarcinoma.