CD44 expression in benign and malignant colorectal polyps

PURPOSE: This retrospective study was undertaken to evaluate immunohistoche mically the expression of CD44 standard protein and CD44v5 and CD44v6 isofo rms in colorectal adenomas and early invasive cancers developing within ade nomas as possible markers characterizing colorectal polyps with a more aggr essive biologic potential. METHODS: Archival tissues of 81 consecutive loca lly resected colorectal polyps, comprising 57 colorectal adenomas and 24 ca rcinomas-in-adenomas, were stained immunohistochemically with the use of co mmercially available mouse monoclonal antibodies: SFF-2 for CD44 standard p rotein, VFF-8 for CD44v5, and VFF-7 for CD44v6. RESULTS: Sixty three percen t of the colorectal polyps were positive for CD44 standard protein, 59 perc ent mere positive for CD44v5, and 27 percent were positive for CD44v6. Nine ty-three percent of the low-grade adenomas were CD44 standard protein-posit ive, in contrast to 50 percent of the high-grade adenomas and only 42 perce nt of the carcinomas-in-adenomas (Kendall's Tau = -0.42; P < 0.0001). CD44v 6 expression was more frequently found in early invasive cancers (54 percen t) than in high-grade adenomas (25 percent) and low-grade adenomas (7 perce nt). This difference also was statistically significant (Kendall's Tau-b = 0.39; P = 0.00003). Surprisingly, a downregulation of CD44 standard protein expression was observed in the adenoma tissue adjacent to carcinomas (62 p ercent) and areas with high-grade atypia (71 percent), compared with low-gr ade adenomas (93 percent; Kendall's Tau-b = -0.28; P = 0.004). CONCLUSIONS: Our data suggest that CD44 standard protein and CD44 isoform vb expression differs considerably in benign and malignant colorectal polyps. Clinical s tudies with larger patient groups could clarify the prognostic potential of CD44 further.