Mutant p53 reactivation and DNA demethylation in the treatment of AML/MDS.
Acute myeloid leukemia/myelodysplastic syndromes (AML/MDSs) carrying p53 mutations are refractory to various standard therapies. Arsenic trioxide (ATO) may be effective in restoring function to p53 structural mutants. Here, we report that mutant p53 rescued by ATO treatment strengthened interferon responses triggered by the DNA hypomethylating agent decitabine by transactivating interferon regulatory factor 7 (IRF7) directly. Decitabine also increased the transactivation activity of ATO-rescued mutant p53 by inducing p53-serine-20 phosphorylation and blocking p53-inhibitory mouse double minute 2 homolog (MDM2). ATO and decitabine together killed p53-mutant AML cells and suppressed tumor growth in cell line-derived xenografts. In a first-in-human pilot clinical trial for testing the combination of ATO and decitabine (PANDA-T0 trial, NCT03855371), which enrolled five patients with AML/MDS harboring p53 structural mutations, the ATO and decitabine regimen produced manageable adverse events, and four of the five treated patients achieved complete remission at the level of the bone marrow, associated with p53 activation and interferon response. In 103 p53-mutant patients whose samples were deposited in Ruijin AML/MDS sample repository, 48 distinct p53 missense mutants were identified, 21 of which were classified as ATO and decitabine regimen applicable because of their competencies in activating p53 and interferon responses upon cotreatment. This study establishes an alternative treatment regimen for patients with p53-mutant AML/MDS and provides a proof-of-concept framework for p53-targeted therapy that differentiates between p53 mutations.