Induction of apoptosis by hexaosmium carbonyl clusters

A number of tri- and hexaosmium carbonyl cluster derivatives were screened for cytotoxicity against five cancer cell lines, and the hexaosmium carbonyl clusters Os6(CO)18 and Os6(CO)16(NCCH3)2 were found to be active against four of these, viz., ER+ breast carcinoma (MCF-7), ER-breast carcinoma (MDA-MB-231), metastatic colorectal adenocarcinoma (SW620) and hepatocarcinoma (Hepg2), with IC50 values as low as 6 μM. Studies on their mode of action with the MDA-MB-231 cell line pointed to the induction of apoptosis, as has been found earlier for the trinuclear cluster Os3(CO)10(NCCH3)2.