Activation of sphingosine-1-phosphate receptor 2 (S1PR2) upregulates dihydropyrimidine dehydrogenase (DPD) expression in colon cancer cells.

Introduction: Dihydropyrimidine dehydrogenase (DPD) is a major determinant of cancer 5-fluorouracyl (5-FU) resistance via its direct degradation. However, the mechanisms of tumoral DPD upregulation have not been fully understood.

Objectives: This study aimed to explore the role of S1PR2 in the regulation of tumoral DPD expression, identifying S1PR2 as the potential target for reversing 5-FU resistance.

Methods: Western blot was used to analyze S1PR2 expression in cultured cancer cells and human colorectal cancer (CRC) tissues. 5-FU resistance was estimated in mouse xenografts of HT-29 and SW480 cells. HPLC-UV was used to measure 5-FU levels in the xenografts. Chromatin immunoprecipitation (ChIP) was used to analyze the binding of YAP1/TEAD1 to the TWIST1 promoter. A luciferase reporter was used to analyze the binding of TWIST1 to the DPYD promoter.

Results: S1PR2 was highly expressed in cancer cell lines and human CRC tissues. Activation of S1PR2 upregulated DPD expression, leading to 5-FU resistance. Mechanistically, activated S1PR2 upregulated nuclear TWIST1 by activating the Hippo/TEAD1-TWIST1 pathway. Nuclear TWIST1 interacted with the JMJD3-RNA Pol II complex, resulting in the interaction of TWIST1 with the DPYD promoter, thus increasing H3K27me3-enriched DPYD transcription. These findings were confirmed in xenografted human colon cancer cells in nude mice. Transfection with an S1PR2 expression vector led to the upregulation of DPD, blunting the sensitivity of SW480 cells to 5-FU by 45.14 %. Conversely, knockdown of S1PR2 resulted in a decrease of DPD, thus increasing the sensitivity of HT-29 cells to 5-FU by 62.12 %. Molecular analysis of these xenografts confirmed the role of S1PR2 in upregulating DPD expression by activating the Hippo/TEAD1-JMJD3 pathway.

Conclusions: Activation of S1PR2 upregulated DPD expression by activating the Hippo/TWIST1-JMJD3 pathway. S1PR2 is therefore a potential target for novel inhibitors that may reverse 5-FU resistance in cancer therapy.