DECREASED LEVELS OF CD44 PROTEIN AND MESSENGER-RNA IN PROSTATE CARCINOMA - CORRELATION WITH TUMOR GRADE AND PLOIDY

BACKGROUND. CD44, a transmembrane protein, is associated with cell-cel l and cell-matrix interaction and with tumor growth and metastasis. Ex pression of both standard form and variant isoforms of CD44 protein ha s been associated with aggressive behavior and metastasis in various t umors, but has not been characterized in prostate adenocarcinoma (PAC) . METHODS. The expression of CD44 standard (CD44s) and splice variant v3, v4/5, v6, v7/8, and v10 proteins were studied in 109 PACs and corr elated with tumor grade, DNA ploidy, and mRNA levels. Monoclonal antib odies against the various CD44 proteins were applied to microwave irra diated, formalin fixed, paraffin embedded sections. The DNA content of the tumors was evaluated by the Feulgen method with the CAS200 Image Analyzer. Total RNA exhibiting 18s and 28s bands was derived from two benign prostatic tissues and 5 PACs exhibiting decreased levels of CD4 4 protein by immunohistochemistry. The RNA was analyzed with reverse t ranscriptase polymerase chain reaction using CD44 specific primers. RE SULTS. The basal cells of the benign prostatic acini revealed uniform membranous staining for CD44s, v3, and v6 in 95-97% of cases. Similar staining was observed for v4/5, v7/8, and v10 in 40%, 30%, and 2% of c ases, respectively. Secretory epithelial cells of the benign prostatic acini showed predominant expression of CD44s (97% of cases). Staining for CD44 variant proteins (v3, v4/5, v6, v7/8, and v10) in this locat ion ranged from 9-22% of cases. Approximately 70% of the PACs showed s ignificant loss of CD44s expression, which correlated with high tumor grade (Gleason greater than or equal to 7) (P = 0.01) and aneuploid st atus (P = 0.002). In 93-98% of the PACs, there was a complete lack of membranous expression for all CD44 variant isoforms. The metastatic PA Cs did not show preferential expression of either the standard form or any variant isoform. The cDNA from the normal prostates yielded a pro minent CD44 standard form polymerase chain reaction products at 482 ba se pair (bp) and variant isoforms at similar to 650 and 850 bp. No CD4 4 products could be amplified from the subset of five PAC cDNAs, even when present at four-fold excess. CONCLUSIONS. PACs exhibit down-regul ation of CD44 protein expression, which correlates with high tumor gra de and aneuploidy. v6 and v3 isoforms were preferentially expressed in the basal cells of benign prostatic acini. Based on a subset of cases , loss of CD44 protein expression is associated with decreased abundan ce of CD44 mRNA. (C) 1996 American Cancer Society.