Epidermal growth factor reduces resistance to doxorubicin

Epidermal growth factor (EGF) increased the sensitivity to doxorubicin (DOX) of a human squamous carcinoma cell line, A431. The relative enhancement of sensitivity by EGF was greater in 2 DOX-resistant sublines, A431/A5 and A431/A10, established by growing cells from surviving colonies after treatment of A431 cells with DOX. A greater number of EGF receptors (both high- and low-affinity binding sites) was found for resistant A431/A5 and A431/A10 cells than for parental cells. The enhanced drug responsiveness is not directly related to EGF effects on growth, as growth inhibition by EGF appears to be similar among the 3 sublines.