Expression and distribution of TGF? mRNA isoforms in a small group of human breast cancers examined by in situ hybridization

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