Manganese(III)-salens induce tumor selective apoptosis in human cells

Histone methylase MLL1 has critical roles in tumor growth and angiogenesis and its knockdown suppresses tumor growth in vivo

Mixed lineage leukemias (MLL) are human histone H3 lysine-4 specific methyl transferases that play critical roles in gene expression, epigenetics, and cancer. Herein, we demonstrated that antisense-mediated knockdown of MLL1 induced cell cycle arrest and apoptosis in cultured cells. Intriguingly, application of MLL1-antisense specifically knocked down MLL1 in vivo and suppressed the growth of xenografted cervical tumor implanted in nude mouse. MLL1-knockdown downregulated various growth and angiogenic factors such as HIF1α, VEGF and CD31 in tumor tissue affecting tumor growth. MLL1 is overexpressed along the line of vascular network and localized adjacent to endothelial cell layer expressing CD31, indicating potential roles of MLL1 in vasculogenesis. MLL1 is also overexpressed in the hypoxic regions along with HIF1α. Overall, our studies demonstrated that MLL1 is a key player in hypoxia signaling, vasculogenesis, and tumor growth, and its depletion suppresses tumor growth in vivo, indicating its potential in novel cancer therapy.

Histone methylases MLL1 and MLL3 coordinate with estrogen receptors in estrogen-mediated HOXB9 expression

Homeobox gene HOXB9 is a critical player in development of mammary gland and sternum and in regulation of renin which is closely linked with blood pressure control. Our studies demonstrated that HOXB9 gene is transcriptionally regulated by estrogen (E2). HOXB9 promoter contains several estrogen-response elements (ERE). Reporter assay based experiments demonstrated that HOXB9 promoter EREs are estrogen responsive. Estrogen receptors ERα and ERβ are essential for E2-mediated transcriptional activation of HOXB9. Chromatin immunoprecipitation assay demonstrated that ERs bind to HOXB9 EREs as a function of E2. Similarly, histone methylases MLL1 and MLL3 also bind to HOXB9 EREs and play a critical role in E2-mediated transcriptional activation of HOXB9. Overall, our studies demonstrated that HOXB9 is an E2-responsive gene and ERs coordinate with MLL1 and MLL3 in E2-mediated transcriptional regulation of HOXB9.

Fe(III)-Salen and Salphen Complexes Induce Caspase Activation and Apoptosis in Human Cells

To explore the apoptotic and antitumor activities of metallo-salens, the authors have synthesized several Fe(III)-salen and salphen complexes and analyzed their effects on human cancer and noncancer cells. Their results demonstrated that Fe(III)-salen and salphen complexes affect cell viability and induce nuclear fragmentation and apoptosis in breast cancer (MCF7) cells. The IC50 values for the active metallo-salen complexes ranged between 0.3 and 22 µM in MCF7 cells. Biochemically active Fe(III)-salen and salphen complexes induced caspase-3/7 activation and release of cytochrome c from the mitochondria to cytosol, suggesting the involvement of the mitochondrial pathway of apoptosis. Comparison of IC50 values toward 3 different cell lines demonstrated that selected Fe(III)-salen complexes induce tumor cell-selective apoptosis in cultured cells. Overall, the studies demonstrated that Fe(III)-salen and salphen complexes induced efficient apoptosis in cultured human cells. The nature of the substituents and the bridging spacer between diamino groups play critical roles in determining the apoptotic activities of Fe(III)-salen and salphen complexes.