Differential expression of CD44 splice variants in human pancreatic adenocarcinoma and in normal pancreas.

Immunohistochemical screening of pancreatic adenocarcinomas from 24 different patients and 9 pancreatic carcinoma cell lines revealed variant CD44 expression in all specimens tested. In contrast to normal pancreatic tissue, carcinomas were strongly positive for epitopes encoded by variant exons v5, whereas v6 was expressed on carcinoma cells as well as normal ductal pancreatic cells. Analysis of RNA expression revealed clear differences between normal pancreatic tissue and tumor specimens. In normal pancreas, v6 and v3 solely and one major chain consisting of v6-v10 were expressed, whereas in pancreatic carcinoma, multiple splice variants were detected. In about 80% of all carcinoma cases and all cell lines tested, the exon v5 appeared in the chain containing at least v4-v10. These data thus far suggest that not the presence alone but the chain composition of the CD44 variant chains could be important for their altered function because one of the major differences between normal and cancer tissue is the linkage of CD44v5 to the CD44v6-containing chain.