EXPRESSION AND DISTRIBUTION OF TGF-BETA MESSENGER-RNA ISOFORMS IN A SMALL-GROUP OF HUMAN BREAST CANCERS EXAMINED BY IN-SITU HYBRIDIZATION

As transforming growth factor betas (TGF beta s) are of potential impo rtance in the natural history of breast cancer, it is desirable to dev elop assays which allow detection of the isoforms of TGF beta, at the level of mRNA and protein in clinical material. In this study an assay capable of detecting the three human TGF beta mRNA species by in situ hybridization is described. The method was validated using as control s, several tissues known to express one or more isoforms of TGF beta. Subsequently, six breast cancers were examined, all of which expressed the three isoforms of TGF beta mRNA. Although there were slight diffe rences in expression between some tumours for certain of the isoforms, in general TGF beta(1), and beta(2), expression was localized predomi nantly within tumour cells, whilst TGF beta(3), localized mainly to sm ooth muscle underlying blood vessels and residual duct structures. The se observations suggest that tumour epithelial cells are the primary s ites of synthesis of the TGF beta isoforms in breast cancers.