2.1. Cell line and cell culture

Human prostate cancer cell lines (LNCaP, VCaP and PC-3) were purchased from the American Type Culture Collection (ATCC, Rockville, MD, USA). The cells were propagated in Roswell Park Memorial Institute (RPMI) medium supplemented with 10% foetal bovine serum (FBS), penicillin (100 units/ml), streptomycin (100 mg/ml), and L-glutamine (300 µg/ml) (All from Gibco, Grand Island, NY, USA). The acidic cell culture medium (pH 6.5) was obtained by the addition of 1 M HCl solution. The cells were grown at 37 °C in a humidified atmosphere of 5% CO₂. ESOM, ROB and DOC were obtained from Sigma-Aldrich (St. Luis, MO, USA). The compounds were dissolved in DMSO to make stock solution, and the final concentration of DMSO in all experiments was 0.2%.