Molecular genetic characterization of alternatively spliced CD44 transcripts in human stomach carcinoma

CD44 is a member of cell surface glycoproteins which are involved in cell-matrix adhesion and tumor metastasis. Certain types of tumors express complex CD44 isoforms generated by alternative splicing of 2v-10v exons, and their expression appears to promote metastasis of tumor cells. Using a nested RT-PCR, we analyzed expression of CD44 variants in 26 stomach carcinoma, 21 matched normal tissues, and 2 carcinoma cell lines. We observed frequent and complex patterns of CD44 variant expression in tumor tissues. While exons 6v and 7v expression was detected in most normal and tumor tissues, exon 9v was most rarely detected. Exon 5v showed a significantly frequent expression in carcinoma, suggesting that its expression might contribute to the malignant progression. While exon 9v was frequently observed in diffuse-type tumors, the other 8 variant exons including 6v showed more frequent expression in intestinal-type tumors. Exons 9v and 10v were predominantly expressed in advanced tumor tissues and exon 8v was expressed more frequently in tumors of lymph node metastasis. We believe that series with a longer follow-up now need to be tested to clarify the association between CD44 splice variant expression and distant metastasis or long-term prognosis.