Inactivation of FoxM1 transcription factor contributes to curcumin-induced inhibition of survival, angiogenesis, and chemosensitivity in acute myeloid leukemia cells

Aberrant expression of forkhead box protein M1 (FoxM1) contributes to carcinogenesis in human cancers, including acute myeloid leukemia (AML), suggesting that the discovery of specific agents targeting FoxM1 would be extremely valuable for the treatment of AML. Curcumin, a naturally occurring phenolic compound, is suggested to possess anti-leukemic activity; however, the underlying mechanism has not been well elucidated. In this study, we found that curcumin inhibited cell survival accompanied by induction of G2/M cell cycle arrest and apoptosis in HL60, Kasumi, NB4, and KG1 cells. This was associated with concomitant attenuation of FoxM1 and its downstream genes, such as cyclin B1, cyclin-dependent kinase (CDK) 2, S-phase kinase-associated protein 2, Cdc25B, survivin, Bcl-2, matrix metalloproteinase (MMP)-2, MMP-9, and vascular endothelial growth factor (VEGF), as well as the reduction of the angiogenic effect of AML cells. We also found that specific downregulation of FoxM1 by siRNA prior to curcumin treatment resulted in enhanced cell survival inhibition and induction of apoptosis. Accordingly, FoxM1 siRNA increased the susceptibility of AML cells to doxorubicin-induced apoptosis. More importantly, curcumin suppressed FoxM1 expression, selectively inhibited cell survival as well as the combination of curcumin and doxorubicin exhibited a more inhibitory effect in primary CD34(+) AML cells, while showing limited lethality in normal CD34(+) hematopoietic progenitors. These results identify a novel role for FoxM1 in mediating the biological effects of curcumin in human AML cells. Our data provide the first evidence that curcumin together with chemotherapy or FoxM1 targeting agents may be effective strategies for the treatment of AML.