Credit: Rhoda Baer
Researchers tested 5 anti-leukemia agents in combination with the methylation inhibitor decitabine and found that the sequential combination of decitabine and idarubicin worked synergistically to produce anti-leukemia effects.
The combination induced cell death in U937, HEL, and SKM-1 human cell lines and acute myeloid leukemia (AML) cells isolated from patients.
The researchers attributed the effects to demethylation of the Wnt/β-catenin pathway inhibitors and downregulation of the Wnt/β-catenin pathway nuclear targets.
The researchers noted that decitabine monotherapy has resulted in relatively low complete remission rates in AML and myelodysplastic syndromes (MDS). So they undertook to investigate combination therapies that would potentially improve efficacy.
Hongyan Tong, PhD, of Zhejiang University School of Medicine in Hangzhou, China, and colleagues reported their findings in the Journal of Translational Medicine.
The researchers chose 5 agents to combine, either simultaneously or sequentially, with decitabine—idarubicin, daunorubicin, aclarubicin, thalidomide, and homoharringtonine—and analyzed their effect on leukemia proliferation in the various AML cell lines mentioned above.
Using the U937 cell line first, the researchers found that when decitabine was combined simulataneously or sequentially with homharringtonine, aclarubicin, thalidomide, and daunorubicin, there was no synergistic effect. The confidence interval (CI) values of various doses were almost all over 0.8.
This was also true for the simultaneous combination of decitabine with idarubicin.
However, when they combined decitabine sequentially with idarubicin, the CI values on all 5 doses were under 0.8, indicating synergism.
In addition, when they administered decitabine twice in the sequence, the CI values were lower than a single administration.
They then confirmed the results in other AML cell lines (HEL and SKM-1) and in cells from AML patients.
Next, they confirmed the synergism of the sequential combination of decitabine and idarubicin in an AML mouse model and found that the combination inhibited tumor growth.
Tumor growth was inhibited significantly on days 4 (P<0.01), days 6 -16 (P<0.001), and started to wane by day 18 (P<0.05) after treatment.
The investigators determined that apoptosis was responsible for the combination’s decrease in leukemic cell viability. The apoptosis rates with the combination therapy were significantly increased in the U937, HEL, and SKM-1 cell lines compared with controls, (all P< 0.001).
In addition, the researchers observed that the tumor cells after treatment showed typical apoptosis characteristics, such as the absence of microvilli on cell membrane, nuclear and cell membrane blebbing, chromosome condensation, and the formation of apoptotic bodies.
The investigators used microarray expression to ascertain the differential gene expression profile of decitabine and idarubicin and found that the Wnt pathway was one of the major pathways disturbed.
Sequential treatment significantly upregulated the Wnt antagonist genes SFRP1, HDPR1, and DKK3. This in turn resulted in increased expression of these genes at the mRNA and protein levels.
In addition, treatment with idarubicin after decitabine caused significant down regulation of the expression of c-Myc, β-catenin, and cyclinD1 genes compared to treatment with decitabine or idarubicin alone.
The investigators concluded that the findings suggest clinical potential in sequential administration of decitabine and idarubicin in AML and high-risk MDS.
