Via the autocrine pathway, lactate increases the production of PD-L1 by activating HCAR1 in cancer cells, thereby facilitating immune evasion of the cells [13]; via the paracrine pathway, cancer cell-derived lactate activates HCAR1 in dendritic cells to suppress the presentation of MHCII on the cell surface, thus preventing the presentation of tumor-specific antigens to other immune cells [12]. Here, HCAR1 is linked to neoplasm.