Expression of CD44 splice variants in normal respiratory epithelium and bronchial carcinomas: No evidence for altered CD44 splicing in metastasis

Expression of alternatively spliced CD44 adhesion molecules has been implicated in metastatic spread of various rodent and human tumors. To determine whether specific CD44 splice variants contribute to metastatic spread of bronchial cancers, we compared the expression of CD44 splice variants in normal bronchial epithelium and bronchial cancers, including tumors which already spread to regional lymph nodes or distant organs. Variant CD44 expression was analysed by immunohistochemistry using variant exon-specific monoclonal antibodies. The precise composition of CD44 transcripts was delineated by exon-specific RT-PCR. The concurring data obtained by both methods revealed that high levels of standard CD44 and variants v5 and v6 as well as low levels of variants v7 and v10 are expressed both in normal bronchial epithelium and squamous cell lung cancers. No CD44 expression was observed in the highly metastatic small cell lung cancers and adenocarcinomas with the exception of bronchioalveolar cancers showing weak expression of standard CD44. These data suggest that expression of alternatively spliced CD44 molecules in the bronchial tract is related to the distinct differentiation of the respiratory epithelium. No correlation between expression of specific CD44 splice variants and metastasis of bronchial cancers was observed.