Transforming growth factor alpha in chemically transformed hamster oral keratinocytes.

The cheek pouch of the Syrian hamster is an excellent tissue for the experimental induction of oral cancer by carcinogenic chemicals. Lysate prepared from a cell line (HCPC-1) derived from one of these hamster oral tumors greatly increased the growth of these oral tumor cells in vitro. We now show that the mitogenic substance, transforming growth factor alpha (TGF-alpha), is present in all of the chemically transformed hamster oral tumors examined (in vitro and in vivo). In no adult normal tissue of the Syrian hamster can we detect expression of TGF-alpha. TGF-alpha could be partly or wholly responsible for the mitogenic activity detected in the lysate of the chemically transformed hamster oral keratinocytes. Both normal and chemically transformed hamster oral keratinocytes express the receptor to epidermal growth factor. The consistent detection of TGF-alpha and epidermal growth factor receptor mRNAs in these hamster oral tumor cells suggests that an autocrine growth mechanism might be operative. This hamster cheek pouch oral cancer model can be used for the molecular analysis of how TGF-alpha and epidermal growth factor receptor might be involved in the malignant transformation of epithelial tissues.