[Expression of standard and variant CD44 in human lung cancer]

CD44 transmembrane glycoprotein, a cell adhesion molecule, is expressed in most adult tissues and in the majority of neoplasms. Due to alternative splicing, this cell adhesion molecule exists in multiple isoforms, some of which have been associated with specific types of tumors as well as with tumor invasion and metastasis. In this study, we observed the expression of CD44 standard (CD44s) and variant forms (CD44v6) in 96 primary lung carcinomas and 12 cases of metastatic lymph nodes by immunohistochemistry and associated the results with clinical outcome. To understand the correlation of CD44's expression with the histological types, differentiation, progression and metastasis of primary lung carcinomas.

Formalin-fixed paraffin-embedded archival tissues from 56 squamous cell carcinomas (SCC), 34 adenocarcinomas (ADC), 6 small cell lung carcinomas (SCLC) and 12 metastatic lymph nodes were immunostained after microwave antigen repair with monoclonal antibodies against CD44s and CD44v6, and the results were associated with histological tumor type, tumor stage and metastasis.

(1) SCC showed much higher membranous expression of CD44s and CD44v6 than ADC (P < 0.01), and there is no expression in all 6 SCLC cases. (2) In 12 metastatic lymph nodes, 10 metastatic lung carcinomas were found strong immunoreactivity for CD44v6 (83%), and in comparison with lung carcinomas without lymph node metastasis (51%), primary lung carcinomas with lymph node metastasis showed strong expression of CD44v6 (91%, chi 2 = 14.92, P < 0.01). (3) The expression of CD44s and CD44v6 is independent from tumor histopathological grading (well, moderate, poor differentiated). Among different tumor stages, however, there is a distinct statistic difference between stage I + II and stage III + IV (chi 2 = 6.05, P < 0.05) with the tendency of higher stage with higher expression of CD44v6.

CD44 expresses mostly in NSCLC. Moreover, there is an stronger expression of CD44s and v6 in SCC over ADC; Immunopositivity of CD44v6 may suggest a potential of high risk for lymph node metastasis in NSCLC; CD44v6 reactivity may be useful to decide TNM stage of NSCLC, especially to discriminate stage I, II with higher stage.