Identification of 17-DMAG as a novel KDM4B inhibitor for combination therapy [ChIP-seq]

Histone demethylases such as KDM4B play critical roles in oncogenic pathophysiology and, therefore may be effective targets for anticancer therapy. Using a TR-FRET demethylation screen assay, in combination with multiple orthogonal validation approaches, we identified geldanamycin and its analog 17-DMAG as novel KDM4B inhibitors. In addition, we found that these Hsp90 inhibitors effect increased degradation of the alveolar rhabdomyosarcoma (aRMS) driver oncoprotein PAX3-FOXO1 and induce the H3K9me3 and H3K36me3 at genomic loci of PAX3-FOXO1 targets. We found that as monotherapy 17-DMAG significantly inhibits expression of PAX3-FOXO1 target genes and multiple oncogenic pathways, induces a muscle differentiation signature, delays tumor growth and extends survival in aRMS xenograft mouse models. The combination of 17-DMAG with conventional chemotherapy significantly enhances therapeutic efficacy, indicating that targeting KDM4B in combination with chemotherapy may serve as a novel therapy to PAX3-FOXO1-positive aRMS. Overall design: Examination of histone modification post geldanamycin treatment.