Expression of CD44v6 Protein in the Progression of Colorectal Carcinomas

ABSTRACT

During tumor progression, a subset of cells acquires metastatic properties, presumably through a series of genetic alterations. CD44 variant glycoproteins containing sequences encoded by exon v6 are related to tumor progression of human colorectal cancer. But their expression in normal colonic epithelium is controversial and studies of CD44 on each step of colorectal carcinogenesis are scanty. We studied CD44v6 expression in the normal colonic mucosa, adenoma, carcinoma in situ, and invasive colorectal carcinomas of different Astler-Coller stages. Endoscopically or surgically resected 36 normal colonic mucosa, 19 adenomas, 8 cases of carcinoma in situ, and 25 cases of carcinoma were selected. After immunohistochemical stain with CD44v6 antibody, positivity was graded as 0 to 4 based on the estimated percentage of positively stained tumor cells. The intensity of positive staining cells was also graded as 0 to 3. In all but one cases (97.2%), normal colorectal mucosa was negative for CD44v6. Positive rates in adenoma, carcinoma in situ, Astler-Coller stage A/B and C/D carcinoma were 73.6%, 88.9% and 87.5%, respectively. There was no statistically significant difference in the positivity between these groups. The staining intensity was significantly higher in the cases of stage C/D carcinoma group than those of adenomas (p<0.05). The percentage of positivity for CD44v6 was higher in stage C/D carcinoma group than adenoma, carcinoma in situ, and stage A/B carcinoma group (p<0.05). Expression of CD44v6 in the normal colonic mucosa was extremely rare and the positivity was increased according to the progression of colorectal tumors. Furthermore, it is more important to interpret the CD44v6 positivity according to the estimated percentage of positively stained tumor cells.