CD274 and oral cavity squamous cell carcinoma: Additionally, a previous study demonstrated that endoplasmic reticulum (ER) stress‐induced oral squamous cell carcinoma (OSCC) cells secreted exoPD‐L1 that resulted in upregulating PD‐L1 expression in macrophages and driving M2 macrophage polarization.[49] Furthermore, the co‐cultivation of macrophages with exosomes derived from HCC cells can upregulate the expression of PD‐L1 on macrophages.