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Exploitation of KAT6A for the treatment of PPP2R1A-mutated cancers

ABSTRACT: PPP2R1A, encoding a subunit of the protein phosphatase 2A (PP2A) enzyme, is mutated in >1% of cases across diverse human cancer types 1. Notably, PPP2R1A mutations are often observed in gynecological cancers 1. To date, clinically applicable therapy based on PPP2R1A mutational status with a durable outcome has not been described. Here we show that inhibition of the KAT6A acetyltransferase induces senescence of PPP2R1A-mutated cancer cells and that PPP2R1A mutational status correlated with response to the KAT6A inhibitors. Mechanistically, mutant PPP2R1A creates KAT6A dependence by regulating transcription of the ubiquitin E3 ligase SKP2 to suppress senescence via degrading p27. Notably, KAT6A inhibition in combination with senolytics such as ABT263 that trigger apoptosis of senescent cells regressed PPP2R1A-mutated tumors. In addition, KAT6A inhibition synergized with immune checkpoint blockade to eradicate PPP2R1A-mutated tumors in vivo. Our data indicate that pharmacological inhibition of KAT6A alone or in combination with senolytics or immune checkpoint blockades represents effective therapeutic strategies for cancers involving PPP2R1A mutations.

ORGANISM(S): Homo sapiens

PROVIDER: GSE302508 | GEO | 2026/07/12

REPOSITORIES: GEO

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Project description:Cellular senescence contributes to a variety of pathologies associated with aging and is implicated as a cellular state in which cancer cells can survive treatment. Reported senolytic drug treatments act through varying molecular mechanisms, but heterogeneous efficacy across the diverse contexts of cellular senescence indicates a need for predictive biomarkers of senolytic activity. Using multi-parametric analyses of commonly reported molecular features of the senescent phenotype, we assayed a variety of models, including malignant and nonmalignant cells, using several triggers of senescence induction and found no predictive power of these traditional senescence markers to identify senolytic drug sensitivity. We sought to identify novel drug targets in senescent cells that were insensitive to frequently implemented senolytic therapies, such as Navitoclax (ABT263), using quantitative mass spectrometry to measure changes in the senescent proteome, compared to cells which acquire an acute sensitivity to ABT263 with senescence induction. Inhibition of the antioxidant GPX4 or the Bcl-2 family member MCL-1 using small molecule compounds in combination with ABT263 significantly increased the induction of apoptosis in some, but not all, previously insensitive senescent cells. We then asked if we could use BH3 profiling to measure differences in mitochondrial apoptotic priming in these models of cellular senescence and predict sensitivity to the ABT263 or the combination of dasatinib and quercetin (D+Q). We found, despite being significantly less primed for apoptosis overall, the dependence of senescent mitochondria on BCL-xL was significantly correlated to senescent cell killing by both ABT263 and D+Q, despite no significant changes in the gene or protein expression of BCL-xL. However, our data caution against broad classification of drugs as globally senolytic and instead provide impetus for context-specific senolytic targets and propose BH3 profiling as an effective predictive biomarker.

Project description:Acetylation of histones by lysine acetyltransferases (KATs) is essential for chromatin organization and function. The MYST family of KATs (KAT5-8) includes the oncogenes KAT6A (MOZ) and KAT6B (MORF/QKF). KAT6A has essential roles in normal hematopoietic stem cells and is the target of recurrent chromosomal translocations, causing acute myeloid leukemia. Similarly, chromosomal translocations in KAT6B have been identified in diverse cancers. KAT6A suppresses cellular senescence via regulation of suppressors of the CDKN2A locus, a function that requires its KAT activity. Loss of one allele of KAT6A extends the median survival of mice with MYC-induced lymphoma from 105 to 413 days. These findings suggest that inhibition of KAT6A and KAT6B may provide a therapeutic benefit in cancer. We have produced a series of highly potent, selective inhibitors of KAT6A/B including WM-8014 and WM-1119. Biochemical and structural studies demonstrate that these compounds are reversible acetyl-CoA competitors and inhibit MYST-catalyzed histone acetylation. WM-8014 and WM-1119 induce cell cycle exit and cellular senescence without causing DNA damage. Senescence is INK4A/ARF dependent and accompanied by gene expression changes typical of loss of KAT6A function. We anticipate that this class of inhibitors will be useful in accelerating development of therapeutics targeting gene transcription regulated by histone acetylation. We show that WM-1119 arrests lymphoma progression in mice. The B cell lymphoma cell line, EMRK1184, was isolated from Eμ-Myc transgenic mice, which are mice with a tumor resulting from the expression of cMyc under the control of the IgH enhancer. EMRK1184 expresses the Cdnk2a locus-encoded ARF and wild type p53. Treatment with WM-1119 inhibited the proliferation of the EMRK1184 lymphoma cells in vitro. RNA-seq and Western blot analysis showed that WM-1119 treatment resulted in increased levels of Cdkn2a and Cdkn2b mRNA and P16INK4a and p19ARF protein, as well as a delayed increase in Cdkn1a mRNA. The data here present RNA-seq profiling of EMRK1184 lymphomas treated with either WM-1119 or a control.

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Exploitation of KAT6A for the treatment of PPP2R1A-mutated cancers

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