Shi Conglin, Chen Liuting, Pi Hui, Cui Henglu, Fan Chenyang, Tan Fangzheng, Qu Xuanhao, Sun Rong, Zhao Fengbo, Song Yihua, Wu Yuanyuan, Chen Miaomiao, Ni Wenkai, Qu Lishuai, Mao Renfang, Fan Yihui
Department of Pathogenic Biology, School of Medicine, Nantong University, Nantong, 226001, China.
Laboratory of Medical Science, School of Medicine, Nantong University, Nantong, 226001, China.
Oncogenesis. 2023 Nov 20;12(1):56. doi: 10.1038/s41389-023-00500-3.
Although the transcriptional regulation of the programmed death ligand 1 (PD-L1) promoter has been extensively studied, the transcription factor residing in the PD-L1 super-enhancer has not been comprehensively explored. Through saturated CRISPR-Cas9 screening of the core region of the PD-L1 super-enhancer, we have identified a crucial genetic locus, referred to as locus 22, which is essential for PD-L1 expression. Locus 22 is a potential binding site for NFE2:MAF transcription factors. Although genetic silencing of NRF2 (NFE2L2) did not result in a reduction of PD-L1 expression, further analysis reveals that MAFG and NFE2L1 (NRF1) play a critical role in the expression of PD-L1. Importantly, lipopolysaccharides (LPS) as the major component of intratumoral bacteria could greatly induce PD-L1 expression, which is dependent on the PD-L1 super-enhancer, locus 22, and NFE2L1/MAFG. Mechanistically, genetic modification of locus 22 and silencing of MAFG greatly reduce BRD4 binding and loop formation but have minimal effects on H3K27Ac modification. Unlike control cells, cells with genetic modification of locus 22 and silencing of NFE2L1/MAFG failed to escape T cell-mediated killing. In breast cancer, the expression of MAFG is positively correlated with the expression of PD-L1. Taken together, our findings demonstrate the critical role of locus 22 and its associated transcription factor NFE2L1/MAFG in super-enhancer- and LPS-induced PD-L1 expression. Our findings provide new insight into understanding the regulation of PD-L1 transcription and intratumoral bacteria-mediated immune evasion.
尽管程序性死亡配体1（PD-L1）启动子的转录调控已得到广泛研究，但位于PD-L1超级增强子中的转录因子尚未得到全面探索。通过对PD-L1超级增强子核心区域进行饱和CRISPR-Cas9筛选，我们确定了一个关键的基因座，称为基因座22，它对PD-L1的表达至关重要。基因座22是NFE2:MAF转录因子的潜在结合位点。虽然NRF2（NFE2L2）的基因沉默并未导致PD-L1表达降低，但进一步分析表明MAFG和NFE2L1（NRF1）在PD-L1的表达中起关键作用。重要的是，作为肿瘤内细菌主要成分的脂多糖（LPS）可极大地诱导PD-L1表达，这依赖于PD-L1超级增强子、基因座22和NFE2L1/MAFG。从机制上讲，基因座22的基因修饰和MAFG的沉默可大大减少BRD4结合和环形成，但对H3K27Ac修饰的影响最小。与对照细胞不同，基因座22发生基因修饰且NFE2L1/MAFG沉默的细胞无法逃避T细胞介导的杀伤。在乳腺癌中，MAFG的表达与PD-L1的表达呈正相关。综上所述，我们的研究结果证明了基因座22及其相关转录因子NFE2L1/MAFG在超级增强子和LPS诱导的PD-L1表达中的关键作用。我们的研究结果为理解PD-L1转录调控和肿瘤内细菌介导的免疫逃逸提供了新的见解。
