CD274 and neoplasm: In turn, MC-C tumor exhibited low constitutive expression of phosphorylated STAT3 (pSTAT3) – an activated molecule that is involved in the transcription of genes that induce tolerogenic and immunosuppressive signals [16]; (Fig. 2A and B ) – and low expression of surface PD-L1 in tumor cells and tumor infiltrating cells (Fig. 2C, D, and E).