title: CREBBP knockdown enhances RAS/RAF/MEK/ERK signaling in Ras pathway mutated acute lymphoblastic leukemia but does not modulate chemotherapeutic response.
abstract: Relapsed acute lymphoblastic leukemia is the most common cause of cancer-related mortality in young people and new therapeutic strategies are needed to improve outcome. Recent studies have shown that heterozygous inactivating mutations in the histone acetyl transferase,CREBBP, are particularly frequent in relapsed childhood acute lymphoblastic leukemia and associated with a hyperdiploid karyotype andKRASmutations. To study the functional impact ofCREBBPhaploinsufficiency in acute lymphoblastic leukemia, RNA interference was used to knock down expression of CREBBP in acute lymphoblastic leukemia cell lines and various primagraft acute lymphoblastic leukemia cells. We demonstrate that attenuation of CREBBP results in reduced acetylation of histone 3 lysine 18, but has no significant impact on cAMP-dependent target gene expression. Impaired induction of glucocorticoid receptor targets was only seen in 1 of 4 CREBBP knockdown models, and there was no significant difference in glucocorticoid-induced apoptosis, sensitivity to other acute lymphoblastic leukemia chemotherapeutics or histone deacetylase inhibitors. Importantly, we show that CREBBP directly acetylates KRAS and that CREBBP knockdown enhances signaling of the RAS/RAF/MEK/ERK pathway in Ras pathway mutated acute lymphoblastic leukemia cells, which are still sensitive to MEK inhibitors. Thus, CREBBP mutations might assist in enhancing oncogenic RAS signaling in acute lymphoblastic leukemia but do not alter response to MEK inhibitors.
authors.affiliation: Newcastle Cancer Centre at the Northern Institute for Cancer Research, Newcastle University, Newcastle upon Tyne, UK.
authors.forename: Zach A
authors.initials: ZA
authors.lastname: Dixon
authors.affiliation: Academic Haematology, Newcastle University, Newcastle upon Tyne, UK.
authors.forename: Lindsay
authors.initials: L
authors.lastname: Nicholson
authors.affiliation: Children's Cancer Research Institute (CCRI), Leukemia Biology Group, Vienna, Austria.
authors.forename: Martin
authors.initials: M
authors.lastname: Zeppetzauer
authors.affiliation: Newcastle Cancer Centre at the Northern Institute for Cancer Research, Newcastle University, Newcastle upon Tyne, UK.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Matheson
authors.affiliation: Newcastle Cancer Centre at the Northern Institute for Cancer Research, Newcastle University, Newcastle upon Tyne, UK.
authors.forename: Paul
authors.initials: P
authors.lastname: Sinclair
authors.affiliation: Newcastle Cancer Centre at the Northern Institute for Cancer Research, Newcastle University, Newcastle upon Tyne, UK.
authors.forename: Christine J
authors.initials: CJ
authors.lastname: Harrison
authors.affiliation: Newcastle Cancer Centre at the Northern Institute for Cancer Research, Newcastle University, Newcastle upon Tyne, UK julie.irving@newcastle.ac.uk.
authors.forename: Julie A E
authors.initials: JA
authors.lastname: Irving
mesh_terms: D000107:Acetylation; D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D050882:CREB-Binding Protein / Q000172:deficiency*; D045744:Cell Line, Tumor; D004195:Disease Models, Animal; D015973:Gene Expression Regulation, Leukemic / Q000187:drug effects; D055785:Gene Knockdown Techniques; D006657:Histones / Q000378:metabolism; D006801:Humans; D020935:MAP Kinase Signaling System; D051379:Mice; D018345:Mice, Knockout; D009154:Mutation; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism* / Q000401:mortality; D048493:Proto-Oncogene Proteins B-raf / Q000378:metabolism*; D011965:Receptors, Glucocorticoid / Q000378:metabolism; D013379:Substrate Specificity; D016896:Treatment Outcome; D018631:ras Proteins / Q000235:genetics*
chemical_list: D006657:Histones; D011965:Receptors, Glucocorticoid; D050882:CREB-Binding Protein; D048493:Proto-Oncogene Proteins B-raf; D018631:ras Proteins