Divergent responses to epidermal growth factor in hormone sensitive and insensitive human prostate cancer cell lines

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Abstract
The present study was undertaken to compare the relationship between response to exogenous epidermal growth factor (EGF) and the expression of the EGF-receptor (EGF-R) in an androgen sensitive (LNCaP) and insensitive (DU145) prostate cancer cell line. Although both cell lines demonstrated a single EGF-R binding site of similar high affinities (mean dissociation constant (Kd) +/- S.D. for DU145 = 1.0 +/- 0.6 nmol l-1; LNCaP = 2.8 +/- 2.2 nmol l-1) the number of binding sites (RT) for the hormone insensitive DU145 cells (mean +/- S.D. = 2.5 +/- 1.0 x 10(5) sites/cell) and 10-fold greater than that expressed in the androgen responsive LNCaP cell line (mean +/- S.D. = 2.0 +/- 1 x 10(4) sites/cell). Additionally exogenous EGF only minimally affected the growth and DNA synthesis of DU145 cells whereas LNCaP cells showed a significant response which was dose dependent. The autologous production of EGF-like molecules by DU145 cells is believed to reduce the cells needs for exogenous mitogens, thereby rendering the cells autostimulatory. Treatment of LNCaP cells with Mibolerone--a synthetic androgen--did not affect either the expression of the EGF receptor or the proliferative response observed with EGF. Western blot analysis, using monoclonal antibodies directed against the EGF receptor revealed a band of approximately 170 kD with DU145 cell lysates but the LNCaP EGF receptor was not detected using this technique.