CD8A and cancer: These findings were consistent with the increased expression of genes associated with the serine biosynthesis pathway (PHGDH, PSAT1, and PSPH) and genes enabling serine entry into one-carbon metabolism (SHMT1 and SHMT2), which were observed exclusively in OT-1 CD8 + T cells after physical interaction with OVA-expressing cancer cells or SIINFEKL-pulsed antigen presenting cells (Fig. 4g, h; Supplementary Fig. 7a–d).