Attenuation of nucleoside and anti-cancer nucleoside analog drug uptake in prostate cancer cells by Cimicifuga racemosa extract BNO-1055

Abstract

This study aimed to investigate the mechanisms underlying the anti-proliferative effects of the ethanolic Cimicifuga racemosa extract BNO-1055 on prostate cells and evaluate its therapeutic potential. BNO-1055 dose-dependently attenuated cellular uptake and incorporation of thymidine and BrdU and significantly inhibited cell growth after long-time exposure. Similar results were obtained using saponin-enriched sub-fractions of BNO-1055. These inhibitory effects of BNO-1055 could be mimicked using pharmacological inhibitors and isoform-specific siRNAs targeting the equilibrative nucleoside transporters ENT1 and ENT2. Moreover, BNO-1055 attenuated the uptake of clinically relevant nucleoside analogs, e.g. the anti-cancer drugs gemcitabine and fludarabine. Consistent with inhibition of the salvage nucleoside uptake pathway BNO-1055 potentiated the cytotoxicity of the de novo nucleotide synthesis inhibitor 5-FU without significantly altering its uptake. Collectively, these data show for the first time that the anti-proliferative effects of BNO-1055 result from hindered nucleoside uptake due to impaired ENT activity and demonstrate the potential therapeutic use of BNO-1055 for modulation of nucleoside transport.

Keywords: 5-FU; 5-Fluorouracil; 5-bromo-2′-deoxyuridine; 5-fluorouracil; BCa; Black cohosh; BrdU; CNT; CR; Cimicifuga racemosa; ENT; Gemcitabine; HPLC; N-methyl-d-glucamine; NBTI; NMG; NT; Nucleoside transport; PCa; Saponin; breast cancer; cimicifuga racemosa; concentrative nucleoside transporter; equilibrative nucleoside transporter; high-pressure liquid chromatography; nitrobenzylthioinosine; nucleoside transporter; prostate cancer; qPCR; real-time quantitative polymerase chain reaction; short-interfering RNA; siRNA.