CD274 and breast carcinoma: To investigate how ER stress modulates macrophage infiltration and PD‐L1 expression, we treated MCF‐7 and MDA‐MB‐231 breast cancer cells with tunicamycin to induce ER stress and then applied RT‐qPCR and Western blot assay (Figure 2A,B) to determine the expression of ER stressed related markers.