CD274 and neoplasm: Experimental results demonstrate that eliminating 5‐HT or blocking 5‐HT signaling leads to a reduction in PD‐L1 levels on tumor cells, increased T‐cell infiltration, and slower tumor progression; these results suggest that antidepressants (e.g., SSRIs) in combination with PD‐1/PD‐L1 inhibitors may exert synergistic antitumor effects [212].