Low serum levels of soluble CD44 variant 6 are significantly associated with poor prognosis in patients with pancreatic carcinoma.

Abstract

Variant CD44 splice products, especially CD44 variant 6 (CD44v6), are expressed on activated lymphocytes and tumor cells. The soluble forms of CD44 standard (CD44s) and CD44v6 are present in the serum of normal individuals. The aim of the current study was to evaluate the concentrations and the prognostic potential of soluble CD44s and CD44v6 in patients with pancreatic carcinoma. The serum CD44s and CD44v6 levels were determined quantitatively by enzyme-linked immunosorbent assay. The molecular mass of CD44v6 isoforms was determined by immunoprecipitation and Western blot analysis. CD44 mRNAs were analyzed by reverse transcriptase polymerase chain reaction followed by exon specific analysis. Both serum CD44s and serum CD44v6 were significantly reduced in patients with pancreatic carcinoma (n = 93, P < 0.001 and P < 0.00005). The median survival in the group with CD44v6 serum concentrations below 100 ng/mL was significantly decreased compared with that in the group with serum concentrations higher than 100 ng/mL (6.7 vs. 15.1 months, P < 0.0005). The isoforms containing soluble CD44v6 (sCD44v6) that were detected in the sera of pancreatic carcinoma patients showed molecular masses comparable to the sCD44v6 isoforms detected in the supernatant of lymphocytes activated by phorbol myestral acetate, whereas the sCD44v6 isoforms detected in the supernatant of pancreatic carcinoma cell lines exhibited higher molecular masses. These results suggest that serum CD44v6 is significantly reduced in pancreatic carcinoma patients and could serve as a good prognostic marker for patients with this disease.