Transcriptional consequences of wild-type and missense mutant p53 in isogenic human acute myeloid leukemia (AML) cell lines

TP53, encoding for the tumor suppressor p53, is the most frequently mutated gene in human cancer. The selective pressures shaping its mutational spectrum, dominated by missense mutations, have remained enigmatic, and neomorphic gain-of-function (GOF) activities have been implicated. We generated isogenic human leukemia cell lines of the most common TP53 missense mutations using CRISPR/Cas9. Functional, DNA binding, and transcriptional analyses revealed loss-of-function (LOF) without GOF effects of missense mutations. Comprehensive mutational scanning of p53 single amino acid variants demonstrated that DNA-binding domain missense variants exert dominant-negative effects (DNE). In mice, DNE of p53 missense variants confer a selective advantage on hematopoietic cells upon DNA damage in vivo. Clinical outcomes in acute myeloid leukemia patients showed no evidence of GOF for TP53 missense mutations. These findings establish dominant-negativity as the primary unit of selection for TP53 missense mutations in myeloid malignancies. Examination of transcriptional profiles in wild-type, null, and missense mutant (R175H, Y220C, M237I, R248Q, R273H, R282W) p53-expressing human AML cell lines (K562 and MOLM13) under steady-state conditions (DMSO) or after induction of DNA damage (daunorubicin)