(M0930-10-58) Modulation of the Activity of Histone Lysine Methylation Writers and Erasers in Leukemia Cells by a Curcumin Analog

Purpose: Dimethoxycurcumin (DMC) is a more stable and bioavailable analog of curcumin and both drugs demonstrated in-vitro and in-vivo antitumor effects. Several studies investigated the epigenetic changes induced by curcumin and its analogs, such as DNA methylation, histone acetylation, and miRNA modulation. Nonetheless, the impact of these compounds on histone methylation remains largely unknown. Accordingly, we tested the effect of curcumin and DMC on the methylation of different histone lysine residues by monitoring the activity of both the histone lysine methyltransferases (HKMT) writer enzymes and histone lysine demethylases (HKDM) eraser enzymes in leukemia cells.

Methods: Both U937 and HL60 leukemia cells were treated with different micromolar concentrations of DMC (5, 2, 1, 0.5, 0.2) or curcumin (20, 10, 5, 2, 1) for 48 hours, followed by quantification of the HKMT activity on the H3K4, H3K9 and H3K27 epigenetic marks and the activity of the lysine demethylases LSD1, JMJD2 and JARID using ELISA and fluorometric/colorimetric detection.

Results: Both drugs increased the activity of the demethylase erasers JARID (Fig. 1), JMJD2 (Fig. 2), and LSD1 (Fig. 3) in both HL-60 and U937 leukemia cells in a dose-dependent manner but to a different extent. On the other hand, both drugs decreased the HKMT activity on both the H3K4 and H3K9 marks, which is consistent with the observed increase in the activity of the demethylase enzymes. Moreover, both drugs decreased the HKMT activity on H3K27. The toxicity of curcumin and DMC was evaluated in both leukemia cell lines using apoptosis assay, none of the used concentrations induced significant apoptosis except for the highest concentration of DMC.

Conclusion: Curcumin and its structural analog DMC induced similar histone lysine methylation modifications in leukemia cells. Both compounds were non-toxic to leukemia cells except for high concentrations of DMC. The overall effect of both drugs on histone lysine methylation promotes demethylation through the activation of different demethylase enzymes and deactivation of HMKT enzymes. Our results highlight an important epigenetic modification that could contribute to the antitumor and chemopreventive effects of both drugs.

Acknowledgements: Research reported in this publication (or presentation) was supported by the National Institute Of General Medical Sciences of the National Institutes of Health under Award Number P20GM103434 to the West Virginia IDeA Network of Biomedical Research Excellence (WV-INBRE). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.


Figure 1: JARID activity in leukemia cells treated with curcumin and DMC. (A) HL60 Cells treated with Curcumin and DMC in different concentration for 48 hrs. (B) U937 Cells treated with Curcumin and DMC in different concentration for 48 hrs. Data represent the mean of three replicates ± SD.


Figure 2: JMJD2 activity in leukemia cells treated with curcumin and DMC. (A) HL60 Cells treated with Curcumin and DMC in different concentration for 48 hrs. (B) U937 Cells treated with Curcumin and DMC in different concentration for 48 hrs. Data represent the mean of three replicates ± SD.


Figure 3: LSD1 activity in leukemia cells treated with curcumin and DMC. (A) HL60 Cells treated with Curcumin and DMC in different concentration for 48 hrs. (B) U937 Cells treated with Curcumin and DMC in different concentration for 48 hrs. Data represent the mean of three replicates ± SD.