PD-L1 levels can be affected by various stimuli, for instance, signaling through the MEK/ERK and the PI3K/AKT pathways has been shown to increase PD-L1 expression [30, 31] and Tsai et al. [32] have reported RAS/PI3K/ERK pathway activation by ADI-PEG 20 in some cancer cell lines. The gene discussed is CD274; the disease is cancer.