Primaquine phosphate induces the apoptosis of ATRA-resistant acute promyelocytic leukemia cells by inhibition of the NF-κB pathway

Targeting DHODH reveals therapeutic opportunities in ATRA-resistant acute promyelocytic leukemia

Although all-trans retinoic acid (ATRA)-induced differentiation has transformed acute promyelocytic leukemia (APL) from the most fatal to the most curable hematological disease, resistance to ATRA in high-risk APL patients remains a clinical challenge. In this paper, we discovered that dihydroorotate dehydrogenase (DHODH) inhibition overcame ATRA resistance. 416, a potent DHODH inhibitor previously obtained in our group, inhibited the occurrence of APL in cells and model mice. Excitingly, 416 effectively overcame ATRA resistance in vitro and in vivo by inducing apoptosis and differentiation. Further mechanistic studies showed that PML/RARα lost the regulation of Bcl-2 and c-Myc in NB4-R1 cells, which probably contributed to ATRA resistance. Notably, 416 maintained its Bcl-2 and c-Myc down-regulation effect in NB4-R1 cells and overcome ATRA resistance by inhibiting DHODH. In conclusion, our study highlights the potential of 416 for APL therapy and overcoming ATRA resistance, supporting the further development of DHODH inhibitors for clinical use in refractory and relapsed APL.

Gab2 promotes acute myeloid leukemia growth and migration through the SHP2-Erk-CREB signaling pathway

Acute myeloid leukemia (AML) is a hematologic malignant disease largely affecting older adults with poor outcomes. Lack of effective targeted treatment is a major challenge in managing the disease in the clinic. Scaffolding adaptor Gab2 is amplified in a subset of AML. However, the causative role of Gab2 in AML remains to be explored. In this study, it was found that Gab2 was expressed at high levels in AML patient samples and AML cell lines. Experiments by knocking down Gab2 expression using shRNA showed that Gab2 promoted AML cell growth and migration in vitro and in vivo. Further studies using Gab2 mutants and pharmacological inhibitors revealed that Gab2 increased CREB phosphorylation via the SHP-2/Erk signaling pathway. CREB phosphorylation contributed to Gab2-induced cell migration by increasing MMP2 and MMP9 expression. This research indicates that high Gab2 expression promotes AML progression through the SHP2-Erk-CREB signaling pathway. CREB suppression may help treat AML with high Gab2 expression.