JUN and neoplasm: Besides this, oncogenic pathways, including RAS/RAF/MEK/ERK and PI3K/Akt/mTOR, have been shown to induce the expression of PD-L1 through activation of c-JUN that, as a component of AP-1 transcription factor, binds to the enhancer element on the PD-L1 gene and augments the transcription signal in tumor cells [10].