In vitro cytotoxicity and induction of apoptosis by ruthenium(II) complexes in HL-60 and K-562

Mononuclear Ru complexes were evaluated for its cytotoxicity against two human leukemic cell lines such as acute myeloblastic leukemia (HL-60) and chronic myelogenic leukemia (K-562). Cytotoxicity was assayed by MTT assay. Fluorescent microscopic analysis, DNA fragmentation study by agarose gel electrophoresis, flow cytometric analysis, and caspase activity by spectrofluorimetry were carried out to evaluate the apoptosis-inducing property of Ru complexes. Ru complexes exhibited cytotoxicity against both the tested cell lines in a dose-dependent manner. Microscopic examination of ruthenium complex-treated cells showed characteristic morphological features of apoptosis, like cell shrinkage and formation of apoptotic bodies. Fluorescent staining with Hoechst 33342 revealed distinct chromatin condensation and nuclear fragmentation. DNA fragmentation pattern and flow cytometric analysis indicated that the cells treated with ruthenium complexes underwent apoptotic cell death. Thus from this investigation it may be concluded that Ru complexes act by the induction of apoptosis in tested human leukemic cell lines.