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Genome-wide CRISPR screen of MOLM13 cells after Idasanutlin treatment

ABSTRACT: Targeting MDM2 is an attractive therapeutic approach for TP53 wild-type (WT) tumors, including the majority of de novo acute myeloid leukemia (AML) cases. However, patients with WT TP53 have shown variable responses to MDM2 inhibitors in clinical trials, highlighting the need to identify additional biomarkers to maximize the chances of clinical success. We performed CRISPR-Cas9 knockout screens to identify genes that confer resistance to an MDM2 inhibitor idasanutlin. We did not find recurrent sgRNA hits or mutations in p53 downstream targets, such as CDKN1A, BAX, PMIAP1, and BBC3, apart from TP53. This was consistent with the results of individual knockout validation experiments and exome sequencing data from idasanutlin resistant cell lines generated form long-term exposure to low doses of idasanutlin. RNA-seq differential expression analysis revealed that major p53 downstream targets were upregulated in both idasanutlin-sensitive MOLM13 and resistant OCIAML3 cell lines after idasanutlin treatment. These findings highlight the pleiotropic functions of TP53 and suggest that the loss of individual downstream targets of TP53 does not significantly contribute to MDM2 inhibitor resistance.

ORGANISM(S): synthetic construct Homo sapiens

PROVIDER: GSE240977 | GEO | 2024/08/15

REPOSITORIES: GEO

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Project description:Ventoclax-based combinations are a new standard of care for patients with acute myeloid leukemia (AML) who are not eligible for intensive chemotherapy, but not all patients respond to these treatments, and those who do may relapse. MDM2 inhibitors are promising therapeutics for treating TP53 wild-type tumors, including most de novo AML cases, but clinical trials have shown modest and variable clinical activity. Functional genomic data suggest that venetoclax and the MDM2 inhibitor, idasanutlin, may be ineffective against monocytic leukemia (FAB M4/M5) or leukemia cells with a high immune signature. We hypothesize upregulated myeloid transcription factors and enrichment of certain environmental cues that confer intrinsic and extrinsic drug resistance to these cells. We show that monocytic leukemia cells express a high level of CEBPB and CEBPB overexpression confers drug resistance to a broad range of BH3 mimetics, venetoclax combinations, and MDM2 inhibitors by downregulating CASP3, CASP6, BCL2, and p53 pathway targets, while upregulating MCL1, BCL2A1, and the NFKB/IL1/TNFA pathway. Moreover, leukemia monocytes can extrinsically protect leukemia blasts from venetoclax and MDM2 inhibition by secreting elevated IL1 and TNFA, which drive myelo/monocytic differentiation and upregulate inflammatory cytokines and receptors, including IL1/TNFA pathway in an autoregulatory loop. Remarkably, IL1A/IL1B and TNFA uniquely upregulate CEBPB expression in M4/M5 cells and protect them from apoptosis induced by venetoclax and MDM2 inhibitors. Conversely, TNFA treatment enhances extrinsic apoptosis in M0/M1 leukemia cells. Inhibitors of IRAK or MAPK14 (p38), which block IL1/TNFA signaling, showed synergistic cytotoxicity in M4/M5 AML when combined with venetoclax and idasanutlin. In summary, we described a targetable, positive feedback loop between CEBPB and IL1/TNFA in monocytic leukemia that drives intrinsic and extrinsic drug resistance to BCL2 and MDM2 inhibitors, offering promising therapeutic strategies to enhance treatment efficacy for monocytic leukemia.

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Genome-wide CRISPR screen of MOLM13 cells after Idasanutlin treatment

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