RB1 loss triggers dependence on ESRRG in retinoblastoma

Retinoblastoma (Rb) is a deadly childhood eye cancer that is classically initiated by inactivation of the RB1 tumor suppressor. Clinical management continues to rely on nonspecific chemotherapeutic agents that are associated with treatment resistance and toxicity. Here, we analyzed 103 whole exomes, 16 whole transcriptomes, 5 single-cell transcriptomes, and 4 whole genomes from primary Rb tumors to identify novel Rb dependencies. Several recurrent genomic aberrations implicate estrogen-related receptor gamma (ESRRG) in Rb pathogenesis. RB1 directly interacts with and inhibits ESRRG, and RB1 loss uncouples ESRRG from negative regulation. ESRRG regulates genes involved in retinogenesis and oxygen metabolism in Rb cells. ESRRG is preferentially expressed in hypoxic Rb cells in vivo. Depletion or inhibition of ESRRG causes marked Rb cell death which is exacerbated in hypoxia. These findings reveal a novel dependency of Rb cells on ESRRG, and they implicate ESRRG as a potential therapeutic vulnerability in Rb. Overall design: RNA-Sequencing of primary retinoblastoma tumors, RNA-Sequencing of low-passaged primary cultured retinoblastoma cell lines with and without knockdown of ESRRG, ChIP-Sequencing of low-passaged retinoblastoma cell lines with pulldown of ESRRG

视网膜母细胞瘤（Retinoblastoma, Rb）是一种致命的儿童眼部恶性肿瘤，其经典发病机制为RB1抑癌基因失活。目前临床治疗仍依赖非特异性化疗药物，但此类药物易引发治疗耐药与毒副作用。本研究对103例原发性视网膜母细胞瘤样本开展全外显子组测序、16例全转录组测序、5例单细胞转录组测序及4例全基因组测序，以鉴定视网膜母细胞瘤的新型依赖靶点。多项复发性基因组畸变提示雌激素相关受体γ（estrogen-related receptor gamma, ESRRG）参与视网膜母细胞瘤的发病进程。RB1可直接结合并抑制ESRRG，而RB1缺失会解除对ESRRG的负向调控。在视网膜母细胞瘤细胞中，ESRRG可调控参与视网膜发生与氧代谢的相关基因。体内实验显示，ESRRG在缺氧状态下的视网膜母细胞瘤细胞中优先表达。敲低或抑制ESRRG可显著诱导视网膜母细胞瘤细胞死亡，且该效应在缺氧环境下会进一步增强。上述研究结果揭示了视网膜母细胞瘤细胞对ESRRG的新型依赖关系，并提示ESRRG可作为视网膜母细胞瘤潜在的治疗靶点。整体实验设计：原发性视网膜母细胞瘤样本的RNA测序（RNA-Sequencing）、低传代原发性培养视网膜母细胞瘤细胞系（经ESRRG敲低与未敲低处理组）的RNA测序，以及低传代视网膜母细胞瘤细胞系的ESRRG染色质免疫沉淀测序（ChIP-Sequencing，通过免疫沉淀富集ESRRG）。