Effects of anti-EGFR antibody cetuximab on androgen-independent prostate cancer cells.

AIM Epidermal growth factor receptor (EGFR) is a novel molecular target for anticancer therapy. This study examined the effects of anti-EGFR antibody cetuximab on two human androgen-independent prostate carcinoma cell lines, Du145 and PC-3. MATERIALS AND METHODS Cell proliferation was monitored with a trypan blue viability assay. Cell apoptosis and cell cycle profile was evaluated by flow cytometry. The expression of various signaling molecules was examined by Western immunoblotting. RESULTS Cetuximab (100 microg/ml) caused a significant growth inhibition by inducing cell apoptosis in Du145 cells, but not in PC-3 cells. It caused EGFR down-regulation and inhibited EGFR Tyr-845 autophosphorylation in both Du145 and PC-3 cells. However, EGFR phosphorylation at Tyr-1173 and MAPK 44/42 phosphorylation were inhibited in Du145 cells, but not in PC-3 cells. Cetuximab was not able to inhibit Akt phosphorylation in either prostate cancer cell line. CONCLUSION Du145 cells only showed a very moderate response to cetuximab whereas PC-3 cells showed resistance. Persistent activation of EGFR downstream signaling likely contributes to cell resistance to cetuximab.