SIGMAR1 and neoplasm: Although few studies in the literature demonstrate other mechanisms by which SIGMAR1 can modulate PD-L1 expression, SIGMAR1 may influence PD-L1 expression indirectly through cross-talk with immune cells in the tumor microenvironment, such as tumor-associated macrophages or T cells, which can secrete cytokines or other factors that regulate PD-L1 expression in cancer cells.