Fibroblasts within the TME can express PD-L1/2 themselves (Pinchuk et al., 2008; Nazareth et al., 2007; Cho et al., 2011) as well as increase PD-L1/2 expression in tumor cells via CXCL5 signaling (Li et al., 2019)—as shown in melanoma and CRC—or miR-92 delivered via CAF-derived exosomes—as shown in breast cancer (Dou et al., 2020). The gene discussed is CD274; the disease is breast carcinoma.