The Hypomethylating Agent Decitabine Prior to Chemotherapy Improves the Therapy Efficacy in Refractory/Relapsed Acute Myeloid Leukemia Patients

Introduction. Most acute myeloid leukemia (AML) patients with adverse prognosis either fail to achieve complete remission (CR) or relapse after short-term remission, new strategies are needed to improve therapeutic effect in these patients. Gene silencing via DNA methylation are frequent and reversible in high-risk AML, it provides the possibility to treat AML patients with DNA-hypomethylating agent. Decitabine alone has limited anti-leukemia effect and minimal toxicity. Studies demonstrated that decitabine prior to chemotherapy was likely to increase efficacy in AML. In this study, we investigated the effect of decitabine on susceptibility to cytotoxic drugs in chemoresistant AML cells. Efficacy and safety of decitabine prior to HAA regimen was evaluated in refractory, relapsed and high-risk AML patients.

Methods. HL60, HL60/ADR, Kasumi-1, and primary AML cells were pre-treated with 1.0 μM decitabine for 72 hours, Sensitivities to harringtonine, adriamycin, cytarabine and the combination was determined by MTT, apoptosis was analyzed by flow cytometry. Protein expression was detected by western blotting. In clinic, Twenty-three patients were enrolled in decitabine prior to HAA regimen, and twenty-four patients in HAA alone. CR ratio was used to evaluate efficacy. Durations of neutrocytopenia or thrombcytopemia and infection incidence were observed to assess the safety. All of patients were followed up to 36 monthes, overall survival (OS) and disease-free survival (DFS) were calculated.

Result. Decitabine increased sensitivity and apoptosis induced by harringtonine in HL60/ADR, as well as adriamycin and cytarabine in HL60/ADR and Kasumi-1 cells. But no change in sensitivity to each drug was observed in HL60, and sensitivity to harringtonine in Kasumi-1. The similar changes in sensitivity to adriamycin and cytarabine were also observed in primary AML cells from refractory patients (n=6). Cytotoxic effect of HAA was alsoincreaed by decitabine in HL60/ADR and Kasumi-1 cells (p=0.004, 0.018). Western blotting showed that decitabine decreased expression of DNMT1, activation of p53 and inhibition of c-Myc, Survivin and Bcl-2. In clinic, 16 (69.6%) patients in decitabine plus HAA regimen responded to the first course of induction therapy: 14 CR (60.9%) and 2 PR (8.7%). 1 in 2 patients with PR achieved CR after second course induction. It brought the overall CR was 65.2%. Otherwise, 10 (45.8%) patients in HAA regimen alone responded to the first induction: 7 CR (29.2%) and 4 PR (16.7%), 3 in 4 patients with PR achieved CR after the second induction, and overall CR reached 41.7%. The first-cycle CR ratio in decitabine plus HAA was higher than that in HAA alone (p=0.041). Patients continued to receive chemotherapy alternatively combined with decitabine. The median OS was 14 months in chemotherapy plus decitabine, 6 months in chemotherapy alone, and median DFS were 18 and 5 months in the former and latter. No significant difference was observed in the time of neutrophil (p=0.832, 0.631) or platelet recovery (p=0.798, 0.544) after induction and intensification therapy. The incidences of infection were also similar (p=0.724, 0.697). The clinic data indicated that decitabine plus HAA regimenit was efficacy and well-tolerated to treat refractory AML patients.

Conclusion. Our results demonstrated that decitabine increased cytotoxic effect against chemoresistant AML cells. Combination of decitabine and HAA was safe and efficacy to treat refractory/relapsed AML. These findings support clinic protocols based on decitabine prior to chemotherapy to overcome resistance and improve therapeutic efficacy in AML patients.