Determination of transforming growth factor beta1 mRNA expression in breast carcinomas by in situ hybridization

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Abstract
The expression of transforming growth factor beta1 (TGF-β1) mRNA has been determined in 16 breast carcinomas using in situ hybridization and compared with TGF-β protein as detected by antibodies against TGF-βT1 and TGF-β1 plus TGF-β2. Digoxigenin-labelled riboprobes were used, with alkaline phosphatase and immunogold silver detection systems. TGF-β1 mRNA was only detected in carcinomas in which TGF-β1 protein was found (9 of 16 cases) and not in those with prominent reactivity for TGF-β2. RNA preservation was poor in two other cases in which TGF-β1 protein had been detected. In general, those tumours with greater numbers of cells labelled for TGF-β1 mRNA had prominent reactivity for TGF-β1 protein. The mRNA was localized to cancer cells with no labelling of stromal cells, although in a small number of cases scanty staining for TGF-β1 protein had been observed in stromal cells. The incidence of detection of TGF-β1 mRNA is lower than the published data from Northern analysis studies of breast carcinomas, suggesting that only higher levels of TGF-β1 mRNA expression are being detected by in situ hybridization. However, this approach has provided useful information about the cellular sites of expression of TGF-β1 in breast carcinomas.