CD44v6 is not relevant in colorectal tumour progression

Abstract.

Background and aims: There is a lack of consensus regarding the role of CD44 variants in colorectal cancer, with conflicting reports regarding their expression and correlation with prognosis. We investigated the expression and prognostic significance of CD44v6 protein in our series of colorectal tumour specimens and then analysed the pattern of CD44 variant mRNA transcript expression in a smaller series of colorectal tumour/normal tissue specimens, thus assessing what our data contributes to this debate. Methods: Immunohistochemistry was used to detect CD44v6 protein expression, while reverse transcriptase–polymerase chain reaction in combination with Southern blotting was used to analyse CD44 mRNA transcript expression. Results: Similar levels of expression of CD44v6 protein were observed in each of the Dukes' stages, ranging from 50% to 67%, indicating no correlation with progression of disease or survival rates. CD44 variant mRNA expression was found in 85% of the tumours and 75% of the normal specimens. The majority of tumours expressed each of the variants. The pattern of variant expression was maintained in the corresponding normal tissue in nearly one-half (47%) of the tumour specimens. A sequential pattern of variant expression was observed in the majority of specimens. There was no association between CD44 variant mRNA expression and Dukes' stage, tumour differentiation or survival. Conclusions: The data reported here, along with those already in the literature, suggest that CD44v6 does not play a pivotal role in colorectal cancer progression. Moreover, due to the pattern of expression of contiguous blocks of variant transcripts it is unlikely that expression of any single variant can predict outcome in vivo.