The Role and Mechanism of ALDH2 in Regulating Oxidative Phosphorylation and Promoting Chemotherapy Resistance of Leukemia Stem Cells

Backgroud and objective: In acute myeloid leukemia (AML), the presence of persistent leukemic stem cells (LSCs) can drive chemotherapy resistance and patient relapse. Traditional chemotherapy drugs include cytarabine usually target cancer cells in the proliferative phase, while fail to eradicate LSCs in the quiescent phase, resulting in minimal residual and even relapse after tumor treatment. Exploring the potential mechanism of chemotherapy resistance of LSCs can provide a new strategy for drug resistance in AML.

Methods:

First, endogenous ALDH2 expression and sensitivity to cytarabine in AML cell lines (including U937, THP-1, KG1, Kasumi-1, MV4-11, and KG1a) and samples from AML patients with remission and relapsed resistance were measured. The purity of CD34+ cell lines (KG1a and Kasumi-1) was limited to more than 95% by CD34+CD38- magnetic bead sorting. Recombinant lentiviral vectors overexpressing and silencing ALDH2 were constructed for transfection of cells in vitro, and a mouse tumor-bearing model was developed to study the regulatory effects of ALDH2 on the chemogenic effects of LSCs, oxidative phosphorylation and autophagy levels. The cytarabine treated cells were selected for transcriptome sequencing and proteomic sequencing, then the relevant molecular mechanisms and metabolomics analysis were analyzed after pathway enrichment analysis of differential genes and protein.

Results: In clinical sample study, we found that the high expression of ALDH2 in LSCs was an important factor in inducing chemotherapy resistance in AML. Also, depletion of ALDH2 reduces the growth of AML cell lines and patient-derived leukemia stem cells in vitro and in mouse models(p<0.05). High expression of ALDH2 in LSCs can significantly increase the proliferation level of leukemia cells in vitro and in vivo(p<0.01), increase the cytarabine resistance , and significantly reduce the survival time of mice(p<0.01),. Most functional LSCs are characterized by relatively low levels of reactive oxygen species. AML cells with ALDH2 overexpression can maintain a low oxidative stress level of tumor cells. ALDH2 inhibition increased oxidative stress levels and decreased oxidative phosphorylation, selectively scavenging quiescent LSCs. Similarly, we demonstrated that down-regulated ALDH2 selectively targets LSCs when treated in combination with cytarabine by using leukemic stem cells isolated from AML individuals(p<0.05). Silencing of the key targets of RNF41 attenuates the chemotherapy resistance of ALDH2 to LSCs.

Conclusion: ALDH2 inhibition increases the sensitivity of leukaemia stem cells to cytarabine therapy by glucose metabolism reprogramming and redox balance. Aldh2-mediated reduction of oxidative phosphorylation, loss of quiescence and differentiation of LSCs induced by oxidative stress, play an important role in cytarabine sensitization , suggesting an alternative strategy for the treatment of AML patients.

No relevant conflicts of interest to declare.