SLC6A4 and neoplasm: FLX treatment-enriched pathways were related to cell proliferation, mitochondrial function, ATP metabolism, serotonin signaling, and glycolysis, and these pathways had a substantially lower enrichment in anti-PD-1-treated CD8 T cells (Figure 2J), suggesting SERT may regulate reactivities of tumor-infiltrating CD8 T cells via mechanisms distinct to those associated with PD-1.