CARM1 inhibition reduces histone acetyltransferase activity causing synthetic lethality in CREBBP/EP300 mutated lymphomas [ChIP-seq]. CARM1 inhibition reduces histone acetyltransferase activity causing synthetic lethality in CREBBP/EP300 mutated lymphomas [ChIP-seq]

Somatic mutations affecting CREBBP and EP300 are a hallmark of Diffuse Large B Cell Lymphoma (DLBCL). These mutations are frequently monoallelic, within the histone acetyltransferase (HAT) domain and usually mutually exclusive, suggesting that they might affect a common pathway and their residual WT expression is required for cell survival. Using in vitro and in vivo models, we found that inhibition of CARM1 activity (CARM1i) slows DLBCL growth and that the levels of sensitivity are positively correlated with the CREBBP/EP300 mutation load. Conversely, treatment of DLBCLs that do not have CREBBP/EP300 mutations with CARM1i and a CBP/p300 inhibitor revealed a strong synergistic effect. Our mechanistic data show that CARM1i further reduces the HAT activity of CBP genome wide and downregulates CBP target genes in DLBCL cells, resulting in a synthetic lethality that leverages the mutational status of CREBBP/EP300 as a biomarker for the use of small molecule inhibitors of CARM1 in DLBCL and other cancers. Overall design: 16 samples - 2 replicates CARM1 inhibitor-treated, 2 replicates DMSO-treated per 3 ChIP antibodies, plus input controls for each replicate

影响CREBBP与EP300的体细胞突变是弥漫性大B细胞淋巴瘤（Diffuse Large B Cell Lymphoma, DLBCL）的标志性特征。此类突变多为单等位基因突变，且位于组蛋白乙酰转移酶（histone acetyltransferase, HAT）结构域内，通常呈相互排斥状态，提示其可能调控共同通路，且细胞存活依赖于二者残留的野生型（wild type, WT）表达。
本研究通过体外与体内模型发现，抑制CARM1活性（CARM1i）可减缓DLBCL细胞增殖，且细胞对该抑制的敏感程度与CREBBP/EP300的突变负荷呈正相关。反之，对不含CREBBP/EP300突变的DLBCL细胞联合施用CARM1抑制剂与CBP/p300抑制剂，可观察到显著的协同效应。
机制研究数据显示，CARM1抑制剂可进一步在全基因组范围内降低CBP的HAT活性，并下调DLBCL细胞中CBP的靶基因表达，由此产生合成致死效应。该效应以CREBBP/EP300的突变状态作为生物标志物，可指导CARM1小分子抑制剂在DLBCL及其他癌症中的临床应用。
整体实验设计：共16份样本——针对3种染色质免疫沉淀（chromatin immunoprecipitation, ChIP）抗体，每种抗体设置2份CARM1抑制剂处理样本重复、2份二甲基亚砜（dimethyl sulfoxide, DMSO）处理样本重复，且每个重复均设置Input对照。