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Targeting KAT6A/KAT6B dependencies in breast cancer with a novel selective, orally bioavailable KAT6 inhibitor, CTx-648/PF-9363 [ChIP-Seq - CUT&RUN]

ABSTRACT: KAT6A, and its paralog KAT6B, are histone lysine acetyltransferases (HAT) that acetylate histone H3K23 and regulate diverse biological processes including transcription, cell-cycle progression, and stem cell development. KAT6A exerts an oncogenic role in several tumor types including breast cancer where it is amplified in 10-15% of patients. However, pharmacologic targeting of KAT6A to achieve therapeutic benefit has been a challenge. Here we describe identification of a highly potent, selective and orally bioavailable KAT6A/KAT6B inhibitor CTx-648 (PF-9363), derived from a novel benzisoxazole series, which demonstrates anti-tumor activity in correlation with H3K23Ac inhibition in KAT6A over-expressing breast cancer. Transcriptional and epigenetic profiling studies show reduced RNA Pol II binding and downregulation of genes involved in estrogen signaling, cell cycle and stem cell pathways associated with CTx-648 anti-tumor activity in ER-positive (ER+) breast cancer. CTx-648 treatment leads to potent tumor growth inhibition in ER+ breast cancer in vivo models, including models refractory to endocrine therapy, highlighting the potential for targeting KAT6A in ER+ breast cancer.

ORGANISM(S): Homo sapiens

PROVIDER: GSE233788 | GEO | 2023/06/05

REPOSITORIES: GEO

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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.

Project description:Limited knowledge of the changes in estrogen receptor (ER) signaling during the transformation of the normal mammary gland to breast cancer hinders the development of effective prevention and treatment strategies. Differences in estrogen signaling between normal human primary breast epithelial cells and primary breast tumors obtained immediately following surgical excision were explored. Transcriptional profiling of normal ER+ mature luminal mammary epithelial cells and ER+ breast tumors revealed significant difference in the response to estrogen stimulation. Consistent with these differences in gene expression, the normal and tumor ER cistromes were distinct and sufficient to segregate normal breast tissues from breast tumors. The selective enrichment of the DNA binding motif GRHL2 in the breast cancer-specific ER cistrome suggests that it may play a role in the differential function of ER in breast cancer. Depletion of GRHL2 resulted in altered ER binding and differential transcriptional responses to estrogen stimulation. Furthermore, GRHL2 was demonstrated to be essential for estrogen-stimulated proliferation of ER+ breast cancer cells. DLC1 was also identified as an estrogen-induced tumor suppressor in the normal mammary gland with decreased expression in breast cancer. In clinical cohorts, loss of DLC1 and gain of GRHL2 expression are associated with breast cancer and are independently predictive for worse survival. This study suggests that normal ER signaling is lost and tumor-specific ER signaling is gained during breast tumorigenesis. Unraveling these changes in ER signaling during breast cancer progression should aid the development of more effective prevention strategies and targeted therapeutics. SIGNIFICANCE STATEMENT: Abnormal estrogen receptor (ER) signaling drives the majority of breast cancers and is targeted by endocrine therapies. However, in normal breast tissue, ER signaling has been demonstrated to promote benign functions such as development and differentiation. Using genomic techniques to characterize ER function in normal breast and breast tumors, this study reveals differential patterns of ER signaling, suggesting that normal ER signaling is lost and tumorigenic ER signaling gained during breast tumor formation. Better understanding of this process can aid the development of improved breast cancer prevention strategies and therapies.

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Targeting KAT6A/KAT6B dependencies in breast cancer with a novel selective, orally bioavailable KAT6 inhibitor, CTx-648/PF-9363 [ChIP-Seq - CUT&RUN]

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