CD274 and cancer: With all these complex functions and diverse interaction partners, MUC1-C is one of the key oncogenic receptors; it contributes to the loss of polarity in cancer cells, cancer stemness, epithelial-mesenchymal transition, epigenetic programming of cancer cells, and functions as an immune suppressor by induction of PD-L1 (programmed death-ligand 1) expression [17,18,19].