Effects of epidermal growth factor receptor concentration on tumorigenicity of A431 cells in nude mice.

To test the relationship between the concentration of epidermal growth factor (EGF) receptors and tumor growth in vivo, we measured the rate of growth of several independently isolated A431 cell lines in athymic mice. This series of A431 clonal variants with differing extents of EGF receptor gene amplification and protein expression were implanted into athymic mice and the time to solid tumor formation and rate of growth were measured. Results of these experiments indicate that the degree of gene amplification and concentration of EGF receptors are directly correlated with the growth of these cells as solid tumors in host animals. Complementary DNA hybridization analysis revealed no change in the extent of gene amplification and expression in implanted cells versus excised tumors nor any evidence of further gene rearrangement in vivo. A high concentration of EGF receptors appears to facilitate the growth of tumor cells in vivo and in vitro.