Constitutive expression of PD-L1 in tumor cells is induced by dysregulation of oncogenic or tumor suppressor gene signaling pathways (i.e., through the RAS-MEK signaling pathway), by activation of abnormal transcription factors (i.e., the oncogenic transcription factor MYC), or by genomic aberrations or gene amplifications (i.e., KRAS mutation). The gene discussed is CD274; the disease is neoplasm.