摘要p53 is mutated in half of cancer cases.However,no p53-targeting drugs have been approved.Here,we reposition decitabine for triple-negative breast cancer(TNBC),a subtype with frequent p53 mutations and extremely poor prognosis.In a retrospective study on tissue microarrays with 132 TNBC cases,DNMT1 overexpression was associated with p53 mutations(P=0.037)and poor overall survival(OS)(P=0.010).In a prospective DEciTabinE and Carboplatin in TNBC(DETECT)trial(NCT03295552),decitabine with carboplatin produced an objective response rate(ORR)of 42％in 12 patients with stage Ⅳ TNBC.Among the 9 trialed patients with available TP53 sequencing results,the 6 patients with p53 mutations had higher ORR(3/6 vs.0/3)and better OS(16.0 vs.4.0 months)than the patients with wild-type p53.In a mechanistic study,isogenic TNBC cell lines harboring DETECT-derived p53 mutations exhibited higher DNMT1 expression and decitabine sensitivity than the cell line with wild-type p53.In the DETECT trial,decitabine induced strong immune responses featuring the striking upregulation of the innate immune player IRF7 in the p53-mutated TNBC cell line(upregulation by 16-fold)and the most responsive patient with TNBC.Our integrative studies reveal the potential of repurposing decitabine for the treatment of p53-mutated TNBC and suggest IRF7 as a potential biomarker for decitabine-based treatments.