MTOR and neoplasm: Nuclear factor (NF)-κB [22], phosphoinositide 3-kinase (PI3K) [23,24], extracellular signal-regulated kinase-1 and -2 (ERK1/2) [23,24], Janus kinase/signal transducer and activator of transcription (JAK/STAT) [25,26], and mammalian targets of rapamycin (mTOR) are shown to be involved in PD-L1 expression in tumor cells.