In contrast, the one-carbon metabolism-related gene SLC38A1 was significantly more downregulated in MSI tumors compared to MSS (MSI: FC = −1.59, 95% CI −1.91 to −1.33 vs. MSS: FC = −1.05, 95% CI −1.17 to −1.06; ANOVA interaction p = 2.2 × 10−4), independent of tumor location. This evidence concerns the gene SLC38A1 and neoplasm.