Parbendazole as a promising drug for inducing differentiation of acute myeloid leukemia cells with various subtypes.

Acute myeloid leukemia (AML) is a malignancy characterized by differentiation arrest of hematopoietic precursor cells. Differentiation therapy is effective for patients with acute promyelocytic leukemia; however, only a few effective differentiation therapies have been established for patients with other AML subtypes. In this study, seven benzimidazole anthelmintics were examined to determine the effects of differentiation on AML cells. The expression of monocyte markers (CD11b and CD14) was elevated after treatment with most benzimidazole anthelmintics. Among these drugs, parbendazole (PBZ) induced AML cell differentiation at low concentration. PBZ induced the monocyte marker expression, KLF4/DPYSL2A gene expression, and apoptosis for 21 AML cell lines with various subtypes and a primary AML sample. Finally, an in vivo analysis using an AML patient-derived xenograft mouse model showed a significant decrease in the chimerism level and prolonged survival in PBZ-treated mice. These findings could lead to a more effective differentiation therapy for AML.

Efficacy of a combination therapy targeting CDK4/6 and autophagy in a mouse xenograft model of t(8;21) acute myeloid leukemia.

One of the most frequent cytogenetic abnormalities in acute myeloid leukemia (AML) is t(8;21). Although patients with t(8;21) AML have a more favorable prognosis than other cytogenetic subgroups, relapse is still common and novel therapeutic approaches are needed. A recent study showed that t(8;21) AML is characterized by CCND2 deregulation and that co-inhibition of CDK4/6 and autophagy induces apoptosis in t(8;21) AML cells. In this study, we examined the in vivo effects of co-inhibiting CDK4/6 and autophagy. We used a mouse model in which t(8;21)-positive Kasumi-1 cells were subcutaneously inoculated into NOD/Shi-scid IL2Rgnull mice. The mice were treated with the autophagy inhibitor chloroquine (CQ), a CDK4/6 inhibitor (either abemaciclib or palbociclib), or a CDK4/6 inhibitor plus CQ. After 20 days of treatment, tumor volume was measured, and immunostaining and transmission electron microscopy observations were performed. There was no change in tumor growth in CQ-treated mice. However, mice treated with a CDK4/6 inhibitor plus CQ had significantly less tumor growth than mice treated with a CDK4/6 inhibitor alone. CDK4/6 inhibitor treatment increased the formation of autophagosomes. The number of single-strand DNA-positive (apoptotic) cells was significantly higher in the tumors of mice treated with a CDK4/6 inhibitor plus CQ than in mice treated with either CQ or a CDK4/6 inhibitor. These results show that CDK4/6 inhibition induces autophagy, and that co-inhibition of CDK4/6 and autophagy induces apoptosis in t(8;21) AML cells in vivo. The results suggest that inhibiting CDK4/6 and autophagy could be a novel and promising therapeutic strategy in t(8;21) AML.

Inhibition of CDK4/6 and autophagy synergistically induces apoptosis in t(8;21) acute myeloid leukemia cells.

The t(8;21) translocation is the most common cytogenetic abnormality in acute myeloid leukemia (AML). Although t(8;21) AML patients have a relatively favorable prognosis, relapse is a frequent occurrence, underscoring the need to develop novel therapeutic approaches. Here, we showed that t(8;21) AML is characterized by frequent mutation and overexpression of CCND2. Analysis of 19 AML cell lines showed that t(8;21) AML cells had lower IC50 values for the selective CDK4/6 inhibitors palbociclib and abemaciclib than non-t(8;21) AML cells. CDK4/6 inhibitors caused cell cycle arrest at G1 phase and impaired cell proliferation in t(8;21) AML cells. CDK4/6 inhibition decreased MAP-ERK and PI3K-AKT-mTOR signaling pathway activity, induced LC3B-I to LC3B-II conversion, and enhanced autophagosome formation, suggesting autophagy induction. Treatment of t(8;21) AML cells with the autophagy inhibitors chloroquine (CQ) or LY294002 in combination with the CDK4/6 inhibitor abemaciclib significantly increased the percentage of apoptotic (Annexin V positive) cells, whereas CQ or LY294002 single treatment had no significant effects. The effectiveness of co-inhibiting CDK4/6 and autophagy was confirmed in primary t(8;21) AML cells. The results suggest that the combination of CDK4/6 and autophagy inhibitors had a synergistic effect on inducing apoptosis, suggesting a novel therapeutic approach for the treatment of t(8;21) AML.

Fusion partner-specific mutation profiles and KRAS mutations as adverse prognostic factors in MLL-rearranged AML.

Mixed-lineage leukemia (MLL) gene rearrangements are among the most frequent chromosomal abnormalities in acute myeloid leukemia (AML). MLL fusion patterns are associated with the patient's prognosis; however, their relationship with driver mutations is unclear. We conducted sequence analyses of 338 genes in pediatric patients with MLL-rearranged (MLL-r) AML (n = 56; JPLSG AML-05 study) alongside data from the TARGET study's pediatric cohorts with MLL-r AML (n = 104), non-MLL-r AML (n = 581), and adult MLL-r AML (n = 81). KRAS mutations were most frequent in pediatric patients with high-risk MLL fusions (MLL-MLLLT10, MLL-MLLT4, and MLL-MLLT1). Pediatric patients with MLL-r AML (n = 160) and a KRAS mutation (KRAS-MT) had a significantly worse prognosis than those without a KRAS mutation (KRAS-WT) (5-year event-free survival [EFS]: 51.8% vs 18.3%, P < .0001; 5-year overall survival [OS]: 67.3% vs 44.3%, P = .003). The adverse prognostic impact of KRAS mutations was confirmed in adult MLL-r AML. KRAS mutations were associated with adverse prognoses in pediatric patients with both high-risk (MLLT10+MLLT4+MLLT1; n = 60) and intermediate-to-low-risk (MLLT3+ELL+others; n = 100) MLL fusions. The prognosis did not differ significantly between patients with non-MLL-r AML with KRAS-WT or KRAS-MT. Multivariate analysis showed the presence of a KRAS mutation to be an independent prognostic factor for EFS (hazard ratio [HR], 2.21; 95% confidence interval [CI], 1.35-3.59; P = .002) and OS (HR, 1.85; 95% CI, 1.01-3.31; P = .045) in MLL-r AML. The mutation is a distinct adverse prognostic factor in MLL-r AML, regardless of risk subgroup, and is potentially useful for accurate treatment stratification. This trial was registered at the UMIN (University Hospital Medical Information Network) Clinical Trials Registry (UMIN-CTR; http://www.umin.ac.jp/ctr/index.htm) as #UMIN000000511.