The expression of variant CD44 in nasopharyngeal carcinoma is unrelated to expression of LMP-1.

CD44 expression in undifferentiated nasopharyngeal carcinoma has been analyzed by sequencing cDNA clones and by immunohistochemical staining using monoclonal antibodies specific for defined variant exons. Both sequencing and antibody staining revealed expression of CD44 variants containing exon v6, which has been linked to tumor metastasis. Although nasopharyngeal carcinoma typically contains a mixture of epithelial tumor cells and infiltrating lymphocytes, the CD44 v6 variant expression could be assigned to the tumor cells in biopsies and in a mouse xenograft system. Consistent with earlier studies, biopsies from about 60% of Chinese nasopharyngeal carcinoma cases expressed the Epstein-Barr virus LMP-1 protein, although all contained EBV DNA and expressed the EBER genes. The antibody specific for CD44 exon v6 generally gave a focal pattern of staining in epithelial tumor cells, but the expression of this variant did not appear to be related to the expression of the LMP-1 protein in the tumor.