DNA methylation-mediated silencing of MEOX1 promotes glycolysis and immune evasion in colorectal cancer cells through inhibition of GLP2R transcription.

[BACKGROUND] GLP2R has been identified as a downregulated gene in colorectal cancer (CRC) and is correlated with immunocyte infiltration. Herein, we aimed to define the molecular characteristics of GLP2R in CRC, focusing on glycolysis and immune evasion.

[METHODS] CRC cells were infected with lentiviruses to analyze the impact of the genetic intervention on the malignant activity of tumor cells in vitro. Three animal models were developed, including an orthotopic tumor model, an experimental liver metastasis model, and an AOM/DSS-induced primary model. ChIP-qPCR and dual-luciferase assays were carried out to analyze the transcriptional regulation of GLP2R by MEOX1. MeDIP and MSP were used to reveal the effects of DNA methylation on MEOX1 expression.

[RESULTS] GLP2R expression was reduced in CRC and correlated with dismal prognosis for patients. Overexpression of GLP2R delayed the growth and metastasis of CRC cells and enhanced the activation of toxic CD4 T cells and antigen-presenting DC cells. GLP2R knockout accelerated AOM/DSS-induced CRC in mice. GLP2R upregulation inhibited YAP1-mediated glycolysis in CRC cells by activating the Hippo signaling. Blocking Hippo signaling reversed the anti-tumor effects of GLP2R overexpression in vitro. MEOX1 promoted the GLP2R transcription by binding to its promoter, and MEOX1 inhibited the CRC growth and metastasis in a GLP2R-dependent manner. MEOX1 promoter DNA methylation was augmented in CRC tissues and cells, and MEOX1 expression was rescued by inhibiting DNA methylation.

[CONCLUSIONS] DNA hypermethylation blocked MEOX1-mediated GLP2R transcription, which activated glycolysis in CRC cells by inhibiting Hippo signaling, leading to CRC growth, metastasis, and immune evasion.