TP53 Mutant Human Acute Myeloid Leukemia Stem Cells Rely on the NFkB Pathway for Self-Renewal and Are Sensitive to Proteasome Inhibitors

Acute myeloid leukemia (AML) is an aggressive blood cancer. TP53 mutations (TP53Mut) confer the worst prognosis in AML. Leukemia stem cells (LSCs) are rare AML cells endowed with self-renewal capacity, allowing them to recapitulate leukemia after therapy and cause disease progression. The pathways that mediate self-renewal in human TP53Mut AML are not well-known. To define the signaling pathways that are activated in TP53Mut human LSCs, we used CyTOF to profile primary human AML samples. TP53Mut LSCs displayed significantly elevated levels of activated (phosphorylated) NF kappa B (pNFkB/p65-S529) and pSTAT1, demonstrating a unique signaling activation state in TP53Mut AML. Next, we sought to predict how these signaling molecules interact in TP53Mut LSCs. To model the signaling protein architecture, we used a machine learning algorithm that has been validated as a method to discover statistical correlations and dependencies between signaling molecules, called Bayesian networks modeling. In TP53Mut LSCs, NFkB displayed a strong influence on the levels of phosphorylated Histone H3 and Ki67, suggesting that proliferation depends on NFkB in TP53Mut LSCs. Next, we asked whether the elevated NFkB levels in TP53Mut LSCs depend on mutant p53. Indeed, we found that knockdown of TP53 reduced NFkB protein levels in Kasumi AML cells (which are TP53R248Q/-) but not in MOLM13 AML cells (which are TP53WT). RNA sequencing showed that TP53 knockdown led to loss of NFkB and LSC self-renewal signatures in Kasumi cells. Furthermore, TP53 knockdown in two primary human TP53Mut AML samples led to a loss of NFkB and LSC transcriptional signatures in these primary samples as well. Serial colony formation in Kasumi cells and TP53Mut primary human AML samples was also abrogated after TP53Mut knockdown. These data suggest that TP53Mut LSCs depend on mutant p53-driven activation of NFkB for self-renewal. Since clinical-grade, direct NFkB inhibitors are not available, we used proteasome inhibitors to test whether NFkB inhibition can kill TP53Mut AML. We treated six primary human TP53Mut AML samples with the proteasome inhibitors, carfilzomib and bortezomib (FDA approved for lymphoid malignancies). Each drug independently reduced NFkB levels and led to a significant reduction of serial colony formation. Next, we treated TP53 knocked-down and control Kasumi cells with bortezomib. In control cells (which harbor mutant p53), bortezomib reduced stem cell markers and activated signaling molecules. However, the effect of bortezomib was significantly attenuated in TP53 knockdown cells, suggesting that the effects of bortezomib in AML are enhanced by mutant p53. Together, these data suggest that TP53Mut AML may rely on the NFkB pathway for self-renewal and that inhibiting this pathway with proteasome inhibitors may target the LSCs of this treatment-refractory AML subtype. Daniel Chang, Marie Lue Antony, Klara E. Noble-Orcutt, Yoonkyu Lee, Vidhyalakshmi Ramesh, Karen Sachs, Chad Myers, Zohar Sachs. TP53 mutant human acute myeloid leukemia stem cells rely on the NFkB pathway for self-renewal and are sensitive to proteasome inhibitors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 3780.