The growth promoting effect of transforming growth factor-alpha in human breast cancer cell lines

Two human breast cancer cell lines, BT-20 and ZR-75-1, were examined with the aim of the elucidating the pathological roles of human transforming growth factor (TGF)-alpha in breast cancers. The TGF-alpha receptor was found to be present in both cell lines. A clonogenic assay revealed that concentrations of TGF-alpha greater than 10(10) M induced a significant increase in colony formation, indicating TGF-alpha to be a breast cancer cell growth factor. Northern blot analysis revealed, moreover, that both cell lines expressed TGF-alpha mRNA. Taking these observations together, it is reasonably possible to assume that TGF-alpha is an autocrine growth factor for breast cancer cells. Although it has been proposed that TGF-alpha could be an epidermal growth factor (EGF) superagonist with regard to its colony formation stimulating activity, the present study demonstrated the colony formation stimulating activities of TGF-alpha and EGF not to be all that much different in the two breast cancer cell lines.