Expression of CD44S and CD44v5 is more common in stage III than in stage I serous ovarian carcinomas

Experimental evidence suggests that attachment of ovarian carcinoma cells to the peritoneal mesothelium involves the interaction between CD44 on ovarian carcinoma cells and hyaluronic acid on mesothelial surfaces. The authors therefore evaluated local and disseminated ovarian serous carcinomas for the expression of standard CD44 and CD44 splice variants CD44v5, CD44v6, and CD44v7/8. The relative amount of hyaluronic acid (HA) in stroma surrounding tumor nests also was studied. Using immunohistochemistry and archival tissue, 14 serous ovarian carcinomas confined to the ovary (stage I) and 14 serous ovarian carcinomas with peritoneal implants and positive peritoneal fluid (stage III) were stained with antibodies to standard CD44, CD44v5, CD44v6, and CD44v7/8. All tissues also were analyzed for HA using a HA binding peptide. Immunostaining was classified as focal or diffuse and graded from 1 to 4 based on intensity. Immunoreactivity for standard CD44 was seen in 5 of 14 (36%) stage I tumors and 10 of 14 (71%) stage III tumors. Similarly, immunoreactivity with CD44v5 was seen in 2 of 14 (14%) stage I tumors and 9 of 14 stage III tumors (64%). Hyaluronic acid was present in the stroma surrounding all stage I and III tumors, but was more intense in the stroma adjacent to metastatic implants from stage III carcinomas. Tumor cells were uniformly negative for intracellular HA. These results suggest that CD44S and CD44v5 are differentially expressed in early (stage I) and advanced (stage III) ovarian serous carcinomas and support previous studies that suggest a role for CD44 and stromal HA in the dissemination of ovarian epithelial cancer.