Poster Presentation Australian Epigenetics Alliance Conference 2022

Using epigenetic drugs for the treatment of DIPG by targeting p300 (#109)

Sarah L Fox 1 , Yolanda Colino Sanguino 1 , Padraic S Kearney 2 3 , Evangeline R Jackon 2 3 , Ryan J Duchatel 2 3 , Holly Holliday 4 5 , Maria Tsoli 4 5 , David Ziegler 4 5 , Matthew D Dun 2 3 , Fatima Valdes Mora 1 4
  1. Cancer Epigenetic Biology and Therapeutics, Children's Cancer Institute, Randwick, NSW, Australia
  2. Cancer Signalling Research Group, University of Newcastle, Callaghan, NSW, Australia
  3. Precision Medicine Program, Hunter Medical Research Institute, New Lambton Heights, NSW, Australia
  4. School of Women's and Children's Health, University of New South Wales, Sydney, NSW, Australia
  5. Molecular Targets and Cancer Therapeutics, Children's Cancer Institute, Sydney, NSW, Australia

Diffuse intrinsic pontine glioma (DIPG) is a lethal pediatric brain cancer with less than 10% of patients surviving beyond 2 years from diagnosis1. It is an epigenetically driven cancer with more than 80% of DIPG cases containing a somatic mutation at the lysine 27 to methionine (H3K27M) in histone H3, and often found in the variant histone, H3.32,3. Targeting the genetic mutation H3K27M directly is, to date, not possible. This study investigates an innovative approach to target H3K27M specifically but indirectly through our recently discovered chromatin partner, acetylated histone variant, H2A.Z (H2A.Zac). Our group has shown that the histone acetyltransferase (HAT) p300 acetylates H2A.Z4, so our approach is to use p300 inhibitors to inhibit H2A.Zac and indirectly impact H3K27M chromatin function. We have investigated the effects of various epigenetic drugs that target different p300 protein domains, either as single or combination treatments in three H3.3K27M cellular models, SF8628, DIPG13 and RA055. Preliminary data reveals that C646 (p300 HAT domain inhibitor) and GNE-049 (p300 bromodomain (BD) inhibitor) act synergistically to inhibit the growth of DIPG13. Unsurprisingly, drugs that both target the HAT domain or the BD domain, act synergistically to reduce cell growth. Our studies are currently investigating the effects of these different combinations in the additional DIPG cell lines and determining the ideal dose of each drug to achieve cell growth inhibition of at least 50%. In addition, the epigenetic and transcriptomic consequences of p300 inhibition will be studied to advance our understanding of the mechanism of action. The best therapeutic strategy will be validated in vivo using DIPG PDX models. This ongoing study provides preliminary evidence for the use of p300 inhibitors as a targeted epigenetic therapy for DIPG.

  1. 1. Warren, K., Diffuse intrinsic pontine glioma: poised for progress. Front Oncol. 2012; 2: 205. 2012, Epub 2013/01/08.
  2. 2. Chan, K.M., et al., The histone H3.3K27M mutation in pediatric glioma reprograms H3K27 methylation and gene expression. Genes Dev, 2013. 27(9): p. 985-90.
  3. 3. Khuong-Quang, D.A., et al., K27M mutation in histone H3.3 defines clinically and biologically distinct subgroups of pediatric diffuse intrinsic pontine gliomas. Acta Neuropathol, 2012. 124(3): p. 439-47.
  4. 4. Colino-Sanguino, Y., et al., A Read/Write Mechanism Connects p300 Bromodomain Function to H2A.Z Acetylation. iScience, 2019. 21: p. 773-788.
  5. 5. Calo, E. and J. Wysocka, Modification of Enhancer Chromatin: What, How, and Why? Molecular Cell, 2013. 49(5): p. 825-837.