Abstract 2014: Modulation of DNA methyltransferases in leukemia cells by curcumin and its associated anti-leukemia activities

Abstract

Abstract Purpose: Curcumin, a natural product of curcuma longa and a safe and widely consumed spice, has been shown to exhibit strong in-vitro and in-vivo anti-tumor activity through the inhibition of NF-κB activity, increase of reactive oxygen species (ROS) levels and decrease of the global DNA methylation levels in leukemia cells. We investigated here the molecular mechanisms of down-regulation of DNA Methyltransferases in leukemia cells by curcumin and its associated anti-leukemia activities. Method: Leukemia cell lines MV4-11, Kasumi-1 and K562 cells and primary leukemia cells from patient with AML were treated with 1-30 μM of curcumin and MV4-11 xenografted nu/nu athymic mice was given i.p. curcumin at 100 mg/kg, and the transcription and protein levels of DNMT1, DNMT3a, DNMT3b, Sp1, p15INK4B and p21 were assessed by either RT-PCR or western blot. The inhibition of NF-κB was determined using Electrophoretic Mobility Shift Assays and the disruption of Sp1-NF-κB/DNMTs promoter complex was investigated by anti-body gel supershifts. The hypomethylating activity of curcumin on the promoter of p15INK4B in MV4-11 cells in-vitro was assessed by a LC-MS/MS method for regional DNA methylation. The anti-proliferative activity of curcumin and cell cycle distribution and apoptosis were evaluated using MTS assay and flow cytometry. Results: In addition to the pre-defined direct inhibition of the enzymatic activity of DNA methyltransferase 1 (DNMT1), curcumin disrupts Sp1/NF-κB complex on DNMT1, DNMT3a and DNMT3b promoter thereby decreasing the transactivation activity of these complexes and down-regulating their mRNA and protein expression levels in AML cells in vitro and in vivo. Consistent with these findings, we showed that promoter hypermethylation of silenced TSGs i.e., p15INK4B decreased while their expression was up-regulated. This results in the increase of protein function, as we showed that in association with p15INK4B re-expression, curcumin induced cell cycle arrest in the S-phase and increase in SubG1 cell fraction, thereby resulting in significant anti-leukemia activity. Conclusion: Different from nucleoside analogs (e.g., azanucleosides), curcumin is an effective S-phase independent DNA methylation inhibitor. Further evaluation of curcumin as a single agent and in combination with other epigenetic targeting compounds in human disease is warranted. Supported by NIH-NCI-R21 CA135478 [ZL], NIH-NCI-RO1 CA102031 [GM], and the BioMedical Mass Spectrometry Laboratory [KC & ZL]. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2014. doi:10.1158/1538-7445.AM2011-2014