Background and Purpose: Dihydropyrimidine dehydrogenase (DPD) is a major determinant of 5-FU resistance in cancers. DPD catalyzes 5-FU into FBAL (α-fluoro-β-alanine) to lower intracellular 5-FU level. We aimed to investigate mechanism and clinical significance of FBAL-stimulated sphingosine 1-phosphate receptor 2 (S1PR2) in upregulation of DPD in colonic cancer. Experimental Approach: Cancer cells transfected or silenced S1PR2 were exposed to FBAL for analyzed S1PR2 and DPD levels. Luciferase reporter assay analyzed S1PR2-activated TWIST1 binding to DPYD promoter. Co-IP assay analyzed TWIST1 interaction with JMJD3-RNA Pol II complex binding to DPYD promoter. HT-29sh-S1PR2 or SW480TgS1PR2 cells xenografted nude mice were used to evaluate clinical significance of S1PR2-upregulated tumoral DPD. Key Results: Activation of S1PR2 upregulated DPD in colonic cancer cells and human fresh cancer specimens. FBAL was first time identified as an etiological stimulator of S1PR2 activation. The FBAL-stimulated S1PR2 increased TWIST1 binding to DPYD promoter and interacting with JMJD3-RNA Pol II complex, enhancing H3K27me3-enriched DPYD transcription elongation. Transfection of S1PR2 in SW480TgS1PR2 xenograft contributed 5-FU resistance by 45.14%, and silence of S1PR2 improved 5-FU sensitivity by 62.12% in HT-29sh-S1PR2 xenograft. S1PR2 inhibitor JTE013 prevented the FBAL-stimulated S1PR2’s effects in upregulating DPD. Cancer cells with high S1PR2 are more resistant to 5-FU, strongly suggesting clinical significance that combination use of S1PR2 inhibitors may be the appropriate 5-FU-based regimens of colonic cancers. Conclusions and Implications: The FBAL-stimulated S1PR2 increased TWIST1 binding to DPYD promoter and interacting with JMJD3-RNA Pol II, enhancing the H3K27me3-enriched DPYD transcription elongation.

Background: Intestinal Fusobacterium nucleatum (F. nucleatum) infection has been implicated into the progression of colorectal cancer (CRC). However, F. nucleatum as a biomarker in 5-fluorouracil (5-FU) resistance of CRC has not been fully analyzed by comparing with other types of gut microbiota. This meta‑analysis aimed to compare the diagnostic performance of intestinal Fusobacterium nucleatum, Bacteroides fragilis and Escherichia coli in 5-FU resistance to colorectal cancer and provide evidence‑based data to clinical practice. Methods: Comprehensive searches of PubMed, Embase, Cochrane Library and Web of Science databases were conducted by the following key words: “Fusobacterium nucleatum”, “5-Fluorouracil resistance”, “Bacteroides fragilis”, “Escherichia coli” and “colorectal cancer(s)”. A total of 11 studies were selected according to the preestablished inclusion and exclusion criteria and analyzed by Review Manager 5.4 software. The sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR) and their corresponding 95% confidence interval (CI) of each eligible study were summarized. Results: Overall sensitivity and specificity of F. nucleatum detection in 5-FU resistance of CRC were 0.65 (95% CI:0.60-0.69) and 0.70 (95% CI:0.59-0.87), respectively. Its PLR and NLR in detecting colorectal cancer were 2.57 (95% CI:1.47-3.21) and 0.52 (95% CI:0.43-0.63). DOR value was 4.92 (95% CI:2.23-7.33), which significantly exceeds the performance of B. fragilis (DOR: 0.53, 95% CI:0.31-0.82) and E. coli (DOR: 0.63, 95% CI: 0.57-0.76) for indicating 5-FU resistance of CRC. Conclusion: Compared with B. fragilis and E. coli, intestinal F. nucleatum is a valuable biomarker for 5-FU resistance to colorectal cancer.