Transforming growth factor release by human tumor cell lines and their interactions with other growth factors

We have studied the production of transforming growth factor (TGF) by several human tumor cell lines and their interactions with exogenously added epidermal growth factor (EGF) and insulin. TGF-like activities were present in all the conditioned media tested. The clonogenic capacity of the tumor cell lines had no correlation with the TGF-like activity production. EGF and insulin had a promoting colony-forming activity on tumor cells but this effect was not additive. Moreover, an inverse statistically significant correlation (-0.817, p<0.05) was found between the response to exogenous EGF and the EGF or TGF-α production by tumor cell lines. The EGF receptor (EGF-R) was not detected in any of the melanomas studied, nor in breast adenocarcinoma cell lines which were producers of EGF or TGF-α.