Abstract IA018: Vulnerabilities of TP53-mutated AML and therapeutic implications

Acute myeloid leukemia (AML) is a complex and genetically diverse with an overall survival rate of less than 32%. Despite the remarkable success of targeted therapy in mediating remission, the emergence of acquired resistance remains a major clinical challenge to overcome. The prevailing understanding of acquired resistance identifies successive genetic changes as the primary cause.TP53 mutations are found in 70-80% of acute myeloid leukemia (AML) patients with complex karyotypes and associated with resistance towards both conventional chemotherapy and newly approved venetoclax plus azacytidine (VEN/AZA) combination. By using CRISPR-Cas9-edited isogenic AML cells harboring, mutation (6 missense mutations) or deletion (KO) of TP53, we found that TP53 mutant/KO cells are less sensitive to etoposide or VEN-AZA induced apoptosis compared to WT without defect in G1 arrest. Surprisingly, we found that TP53-mutant and TP53-wild-type (WT) isogenic AML cells and primary tumors (n=40) had comparable mitochondrial outer membrane permeabilization (MOMP) at baseline, despite the key role of TP53 in transcriptionally activating proapoptotic regulators of MOMP (such as BAX, PUMA, and NOXA). Based on these findings, we hypothesize that the targets downstream of mitochondrial permeabilization drive resistance to HMA/VEN combinations in TP53 mutant disease. By leveraging unbiased bulk RNA-seq and proteomics, and whole genome CRISPR-cas9 screen we identified IAPs as functional vulnerability. Collectively we reveal novel chemoresistance mechanisms in TP53 mutant/KO downstream of MOMP and provide a targeting strategy to improve existing therapy by targeting non-transcriptional function of TP53 in overcoming therapy resistance. Citation Format: Shruti Bhatt. Vulnerabilities of TP53-mutated AML and therapeutic implications [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Expanding and Translating Cancer Synthetic Vulnerabilities; 2024 Jun 10-13; Montreal, Quebec, Canada. Philadelphia (PA): AACR; Mol Cancer Ther 2024;23(6 Suppl):Abstract nr IA018.