B1, a Novel Amonafide Analogue, Overcomes the Resistance Conferred by Bcl-2 in Human Promyelocytic Leukemia HL60 Cells

In the course of screening for novel anticancer compounds, B1 [N-(2-(dimethylamino) ethyl)-2-aminothiazonaphthalimide], a novel amonafide analogue, was generated as a new anticancer candidate. In the present study, B1 displayed stronger antitumor effects than amonafide in HL60 cells. We further examined whether B1 overcomes the resistance conferred by Bcl-2, as overcoming the resistance conferred by Bcl-2 represents an attractive therapeutic strategy against cancer. Our viability assay showed that B1 overcomes the resistance conferred by Bcl-2 in human promyelocytic leukemia HL60 cells. Various apoptosis assessment assays showed that B1 overcomes the resistance conferred by Bcl-2 in HL60 cells by inducing apoptosis. Noticeably, we elucidated the marked downregulation of 14-3-3 sigma protein by B1, indicating that B1 overcomes the resistance conferred by Bcl-2 in HL60 cells via 14-3-3 sigma. The analysis of chromatin immunoprecipitation assay indicated that MBD2 was associated with the methylated 14-3-3 sigma promoter-associated CpG island and thus interfered with transcriptional activity of the methylated promoter. Furthermore, knockdown of MBD2, using siRNA transfection, inhibited B1-induced apoptosis and overcame the resistance conferred by Bcl-2. Accordingly, these data showed the involvement of MBD2 in B1-induced apoptosis and overcoming the resistance conferred by Bcl-2, which suggested that MBD2 might guide the development of future anticancer agents. Mol Cancer Res; 8(12); 1619-32. (C) 2010 AACR.