Background: Intermittent androgen ablation is a palliative treatment option for advanced prostate cancer which is associated with less side effects, improved quality of life of patients, and reduced costs. Regulation of growth and survival of prostate cancer cells during intermittent androgen withdrawal has not been studied in appropriate models yet.
Methods: Two cycles of androgen withdrawal and supplementation were performed in human prostate cancer cells LNCaP in vitro. Proliferation of prostate cancer cell sublines established after intermittent androgen withdrawal was assessed in the absence or presence of epidermal growth factor (EGF) by protein determination. Cell cycle was analyzed with a flow cytometer. EGF was measured in the supernatants of LNCaP sublines with a commercial ELISA. EGF receptor mRNA and protein were determined by real-time PCR and Western blot, respectively.
Results: Basal proliferation rate of all newly generated LNCaP sublines increased over that of the parental LNCaP cell line. The highest stimulation of proliferation by exogenous EGF was observed in parental LNCaP cells. In each LNCaP derivative established during intermittent androgen withdrawal, the percentage of cells in the S phase of cell cycle was higher than that in parental LNCaP cells. EGF levels did not increase during intermittent androgen ablation. The expression of EGF receptor protein decreased following each cycle of androgen ablation and increased subsequently after androgen supplementation. EGF receptor (EGFR) mRNA was regulated in a similar manner in LNCaP derivatives established during the second cycle of intermittent withdrawal.
Conclusions: Changes in the expression of the EGF receptor occur during intermittent androgen ablation but they cannot be solely responsible for increased basal proliferation. Alternatively, other ligands and receptors of the EGF system may become overexpressed during prolonged withdrawal and supplementation of androgenic hormones in prostate cancer therapy.
Copyright 2004 Wileey-Liss, Inc.