STAT3 and cancer: Oncogenic pathways, including STAT3, ERK1/2, NF-κB, and AKT, have been shown to regulate PD-L1 expression in a variety of cancers (Chen et al. 2016; Fujita et al. 2015; Gowrishankar et al. 2015; Jiang et al. 2013; Lastwika et al. 2016).