Synergistic antiproliferative activity of suramin and alpha 2A-interferon against human colorectal adenocarcinoma cell lines: in vitro studies

Suramin, a polysulphonated naphthylurea proven to be an effective anticancer agent against selected tumours, and alpha 2A-interferon (alpha 2A-IFN) were investigated for their combined effects on HCT-8, HCT-15, CL-D, SW-480 and SW-620 human colorectal adenocarcinoma cell lines. All lines were sensitive to clinically achievable concentrations of suramin in a dose-dependent manner, while alpha 2A-IFN alone induced only a modest reduction of cell growth. Concomitant treatment with suramin and alpha 2A-IFN resulted in a synergistic inhibition of cell viability in each cell line at all doses tested. However, when suramin and alpha 2A-IFN were administered sequentially, inhibition of cell viability was clearly dependent on the timing of treatment schedule, with maximum effect obtained when alpha 2A-IFN was administered prior to suramin. In contrast, pretreatment with suramin was markedly inferior to the former one. In conclusion, suramin and alpha 2A-IFN exert a synergistic effect on human colorectal cell proliferation in vitro at clinically achievable concentrations. This observation may have clinical relevance although the mechanisms of interaction remain to be elucidated.