Importance of different CD44v6 expression in human gastric intestinal and diffuse type cancers for metastatic lymphogenic spreading

Abstract

In 42 human gastric adenocarcinomas of intestinal (n = 25) and diffuse types (n = 17) the expression of CD44v6 splice variants was investigated immunohistochemically and compared with the pattern of lymphogenic tumor spreading. Distinct differences were observed between the two cancer types: 92% of intestinal-type tumors expressed CD44v6 as in the intestinal metaplasia in chronic atrophic gastritis, while v6 expression occurred in only 17% of diffuse-type cancers. The analysis of RNA expression confirmed the immunohistochemical data. Intestinal-type cancers yielded a much more complex pattern of amplification products hybridizing to exon v6 than did normal mucosa, whereas diffuse-type tumors did not express exon v6. Also the pattern of lymphogenic spreading was quite different between the two cancer types: in diffuse-type tumors only a sinus carcinosis without CD44v6 expression was observed in a significantly higher number of lymph nodes than in intestinal-type cancers, which showed in particular infiltrative lymph node metastases always with CD44v6 expression as in the primary tumors. When infiltrative lymph node invasion occurred in v6-negative diffuse-type cancers, v6 neoexpression was also demonstrable in the lymph node metastases. Additionally, the number of infiltrative lymphogenic metastases increased with more extensive v6 expression in primary gastric cancers of both types. These data suggest that the expression of CD44v6 isoform is important for the infiltrative spreading of tumor cells into lymph nodes. Additionally, the phenotypic similarities in v6 expression between intestinal metaplasia and intestinal-type cancers, but not of tumors of diffuse type, may support the Correa hypothesis.