Mutation and Microsatellite Instability (MSI) Affect the Differential Gene Expression of Folic Acid and 5-Flourouracil Metabolism-Related Genes in Colorectal Carcinoma

In colorectal carcinoma (CRC), 5-fluorouracil (5-FU) remains the cornerstone of adjuvant systemic therapy, with folic acid (FA) serving as an essential adjunct. Expression of genes related to the metabolism and action of 5-FU and FA can be influenced by patient- and tumor-specific biological factors. In this study, we explore differential gene expression profiles of 180 genes representing 14 different gene sets associated with different 5-FU and FA metabolism processes, at both gene and pathway levels across clinical and molecular subgroups. In 71 patients with CRC, paired tumors and normal colonic tissues were analyzed. In CRC tissue, several gene sets (including Cell Cycle Checkpoint, Oxidative Stress Response, and Signaling Pathway, etc.) were upregulated, while three gene sets (Apoptotic, Tumor Suppressor, and Endoplasmic Reticulum Stress) were downregulated. Kirsten rat sarcoma virus (<i>KRAS</i>), tumor protein p53 (<i>TP53</i>), and microsatellite instability (MSI) status impacted gene expression across molecular subgroups. At the individual gene level, among cell cycle genes, the BUB3 mitotic checkpoint protein (<i>BUB3</i>) was upregulated in MSI tumors compared to MSS, whereas SMAD family member 4 (<i>SMAD4</i>) was downregulated in MSS tumors compared to MSI. DNA fragmentation factor alpha (<i>DFFA</i>) was downregulated in MSI and upregulated in MSS. Notably, thymidylate synthetase (<i>TYMS</i>) was more upregulated in MSI tumors (1.65-fold; 95% CI: 1.27-2.13) compared to MSS (1.19-fold; 95% CI: 1.02-1.39). Dysregulation of these genes across these factors will broaden our understanding of 5-FU-based treatment in CRC. Furthermore, targeting dysregulated pathways could form the basis for improved precision therapies tailored to CRC subtypes.