Growth factor production during multistage transformation of epithelium in vitro. I. Partial purification and characterisation of the factor(s) from a fully transformed epithelial cell line

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Abstract
Transforming growth factor (TGF)‐like activity is characterised from one of a series of salivary epithelial cell lines, CSG 211, chemically transformed in vitro. In this transformation system, we can demonstrate multiple stages in the acquisition of a malignant phenotype by normal diploid ductal epithelial cells from male mouse submandibular gland. The fully transformed, tumorigenic cell TGF‐like activity in serum‐free supernatants resembles no other well‐characterised growth factor and has an apparent molecular weight (Mr) of 14 kd. There is also evidence of a higher Mr activity, which is separable by anion exchange chromatography. We show that the premalignant, nontumorigenic progenitor cells of this line do not produce demonstrable TGF‐like activity and that this property is therefore acquired as CSG 211 cells become carcinoma producing.