A druggable TCF4- and BRD4-dependent transcriptional network sustains malignancy in blastic plasmacytoid dendritic cell neoplasm. Homo sapiens

We combined loss-of-function RNA interference screening and a high-throughput drug toxicity screening to define novel therapeutic targets in blastic plasmacytoid dendritic cell neoplasm (BPDCN), an aggressive hematologic malignancy for which no curative therapy exists. The E-box transcription factor TCF4 emerged as the master transcriptional regulator of the BPDCN oncogenic program, a finding that can be exploited for the accurate molecular diagnosis of BPDCN. Genetic interference with the TCF4-dependent network induced a rewiring of BPDCN gene expression, resulting in apoptosis. Treatment of BPDCN lines with bromodomain and extra-terminal domain inhibitors (BETi's) down regulated TCF4 and its target gene network, inducing apoptosis both in vitro and retarding growth of BPDCN xenografts in vivo, supporting the clinical evaluation of BETi's in this lethal cancer. Overall design: For shRNA gene expression profiling, Cal-1 and Gen2.2 cells were infected with either Ctrl or TCF4 shRNAs. Following puromycin selection, shRNA expression was induced for 24 hours and 48 hours in Cal-1 cells (n=4), and for 12 hours and 24 hours in Gen2.2 cells (n=4). For JQ1 gene expression profiling, Cal-1 (n=4) and Gen2.2 (n=4) cells were treated with either DMSO or 100 nM JQ1 for 1 hour, 3 hours, 8 hours and 24 hours.

本研究联合功能缺失型RNA干扰筛选与高通量药物毒性筛选，以明确母细胞性浆细胞样树突状细胞肿瘤（blastic plasmacytoid dendritic cell neoplasm, BPDCN）的新型治疗靶点。BPDCN是一类侵袭性血液系统恶性肿瘤，目前尚无根治性治疗方案。研究发现，E-box转录因子TCF4是BPDCN致癌程序的核心转录调控因子，这一发现可应用于BPDCN的精准分子诊断。靶向TCF4依赖调控网络的遗传干扰可诱导BPDCN基因表达重编程，最终引发细胞凋亡。使用溴结构域和额外末端结构域抑制剂（bromodomain and extra-terminal domain inhibitors, BETi）处理BPDCN细胞系后，可下调TCF4及其靶基因网络，在体外诱导细胞凋亡，并在体内抑制BPDCN异种移植瘤的生长，该结果支持了BETi在该致死性癌症中的临床评估。实验整体设计如下：对于shRNA基因表达谱分析，将Cal-1与Gen2.2细胞分别感染对照（Ctrl）shRNA或TCF4 shRNA；经嘌呤霉素筛选后，在Cal-1细胞中诱导shRNA表达24小时与48小时（每组n=4），在Gen2.2细胞中诱导shRNA表达12小时与24小时（每组n=4）。对于JQ1基因表达谱分析，将Cal-1（n=4）与Gen2.2（n=4）细胞分别用二甲基亚砜（DMSO）或100 nM JQ1处理1小时、3小时、8小时及24小时。