Search

The H3K4 demethylase KDM5B is amplified and overexpressed in luminal breast cancer, suggesting it might constitute a potential cancer therapy target. Here, we characterize, in breast cancer cells, the molecular effects of a recently developed small-molecule inhibitor of the KDM5 family of proteins (KDM5i), either alone or in combination with the DNA-demethylating agent 5-aza-2′-deoxycytidine (DAC). KDM5i treatment alone increased expression of a small number of genes, whereas combined treatment with DAC enhanced the effects of the latter for increasing expression of hundreds of DAC-responsive genes. ChIP-seq studies revealed that KDM5i resulted in the broadening of existing H3K4me3 peaks. Furthermore, cells treated with the drug combination exhibited increased promoter and gene body H3K4me3 occupancy at DAC-responsive genes compared with DAC alone. Importantly, treatment with either DAC or DAC+KDM5i induced a dramatic increase in H3K27ac at enhancers with an associated significant increase in target gene expression, suggesting a previously unappreciated effect of DAC on transcriptional regulation. KDM5i synergized with DAC to reduce the viability of luminal breast cancer cells in in vitro assays. Our study provides the first look into the molecular effects of a novel KDM5i compound and suggests that combinatorial inhibition along with DAC represents a new area to explore in translational epigenetics. Significance: This study offers a first look into the molecular effects of a novel KDM5 inhibitory compound, suggesting how its use in combination with DNA methylation inhibitors presents new opportunities to explore in translational cancer epigenetics. Cancer Res; 78(5); 1127–39. ©2017 AACR.

Mutations in the Adenomatous Polyposis Colt (APC) gene have been implicated both in familial as well as sporadic gastrointestinal (GI) cancers. APC mutations are associated with autosomal dominant inheritance of disease in humans. Similarly, mice that contain a single mutant APC gene encoding a protein truncated at aa 716 (Ape716) develop multiple polyps throughout the GI tract as early as 4 weeks after birth. Inactivation of another tumor suppressor gene, Hypermethylated in Cancer 1 (HIC1) often occurs in human cancers, including GI, via CpG island hypermethylation. Homozygous deletion of Hic1 in mice results in major developmental defects and embryonic lethality. Hic1 heterozygotes have previously been shown to develop age dependent tumors of a variety of tissue types. We now report that loss of a single Hic1 allele can promote crypt dysplasia of the small intestine and further potentiate polyp formation in Apc716 mice. Hic1+/−, Apc716 double heterozygous mice develop increased numbers of polyps throughout the GI tract by 60 days. Hic1 expression is lost in polyps with a selective increase in DNA hypermethylation of this gene only in polyps from double-heterozygous mice. Immunohistochemical analyses of polyps show increases in markers such as -catenin, SIRT1, and Sox9, indicating aberrant Wnt and Hic1 signaling. Together, our data suggest that loss of a gene frequently silenced via epigenetic mechanisms, Hic1, can cooperate with loss of a gene often mutated in GI cancer, Apc, to promote tumorigenesis in an in-vivo model of multiple intestinal neoplasia. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr LB-92.