Therapeutic Potentials of Inhibition of Jumonji C Domain-containing Demethylases in Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is a complex disease affected by both genetic and epigenetic factors. Histone methylation and demethylation are types of epigenetic modification in chromatin remodeling and gene expression. Abnormal expression of histone demethylases is indicated in many types of cancer including AML. Although many commercial drugs are available to treat AML, an absolute cure has not been discovered yet. However, inhibition of demethylases could be a potential cure for AML. Methylstat is a chemical agent that inhibits the Jumonji C domain-containing demethylases.

The cytotoxic and apoptotic effects of methylstat and doxorubicin on HL-60 cells were detected by MTT cell viability assay, double staining of treated cells with annexin-V/propidium iodide, and caspase-3 activity assay. Mitochondrial activity was analyzed using JC-1 dye. The expression levels of the BCL2 and BCL2L1 anti-apoptotic genes in HL-60 cells were determined using real-time polymerase chain reaction (PCR). Lastly, the cytostatic effect was determined by cell cycle analysis.

In our research, cytotoxic, cytostatic, and apoptotic effects of methylstat on human HL-60 cells were investigated. Cytotoxic and cytostatic analyses revealed that methylstat decreased cell proliferation in a dose-dependent cytotoxic manner and arrested HL-60 cells in the G2/M and S phases. Methylstat also induced apoptosis through the loss of mitochondrial membrane potential and increases in caspase-3 enzyme activity. The expression levels of BCL2 and BCL2L1 were also decreased according to real-time PCR results. Finally, the combination of methylstat with doxorubicin resulted in synergistic cytotoxic effects on HL-60 cells.

Taken together, these results demonstrate that methylstat may be a powerful candidate as a drug component of AML treatment protocols.