CD274 and neoplasm: Furthermore, the conditioned medium from these M1-polarized macrophages significantly suppressed the expression of PD-L1, a key factor of immunosuppressive tumor microenvironment, which can be prevented by depleting IL-1β in macrophages (CM-THP1-shIL1β-CM-GC-EF1a-ALDH3A2) (Fig. 9E, F).