Effects of PD-L1 silencing on global transcriptomic changes in tumor

Cancers evade anti-tumor immunity by up-regulation of immune checkpoint molecules, such as programmed cell death 1 ligand 1 (PD-L1), in response to stimuli, such as interferon-gamma (IFN?). Expression of PD-L1 within the tumor microenvironment inhibits the anti-tumor immune response by binding the immune checkpoint receptor PD-1 expressed on T cells. Immune checkpoint inhibitors that target the PD-1/PD-L1 pathway are less toxic than standard chemotherapy and produce durable tumor regression and overall survival benefits in several tumors. However, only a small group of patients respond to these therapies, and some of the responders develop acquired resistance. Understanding the effects of PD-L1 silencing on global gene expression is critical to identifying potential immune evasive mechanisms. In this study, we performed transcriptome analysis of PD-L1 knockdown cells and showed that silencing PD-L1 reduced the expression of only a few immunosuppressive genes. Our findings suggest that the identification of novel targets that can control a larger number of immunosuppressive molecules could lead to the development of more effective immunotherapies. Overall design: Tumor cell lines were transfected with an siRNA control or two different siRNAs targeting PD-L1. 48 hours after transfection, cells were stimulated with interferon gamma for 24 hours. RNA expression profiles were generated by RNA-seq, in duplicate, using Illumina NovaSeq6000.