BDH2 promotes GLIPR1 promoter methylation and thus increases 5-FU sensitivity in colorectal cancer.

5-Fluorouracil (5-FU) is an effective drug in the treatment of colorectal cancer (CRC); however, the development of acquired resistance to 5-FU poses a great challenge in clinical practice. Through the analysis of public datasets, we found that reduced 3-Hydroxybutyrate Dehydrogenase 2 (BDH2) expression in CRC tissues predicted poor survival in CRC patients. Low expression of BDH2 in clinical CRC tissue samples predicted a higher degree of malignancy. In addition, public dataset analysis showed that GLI Pathogenesis Related 1 (GLIPR1) expression was elevated in CRC patients following 5-FU treatment, contrasting with the expression pattern of BDH2. We reported that in 5-FU-resistant CRC cell lines (LOVO/5-FU and HCT15/5-FU), BDH2 was downregulated, while the expression of GLIPR1 was increased. To explore the regulatory relationship between BDH2 and GLIPR1 in 5-FU resistance, BDH2 and GLIPR1 overexpression plasmid vectors were constructed to transfect 5-FU resistant CRC cell lines. BDH2 led to enhanced 5-FU sensitivity in 5-FU-resistant CRC cell lines and inhibited the malignant behavior of CRC-resistant cells in vitro. In nude mice with subcutaneous tumors and intraperitoneal injections of 5-FU, tumor tissues formed by BDH2-overexpressing cells exhibited slower growth and increased apoptosis. Mechanistically, the upregulation of BDH2 increases GLIPR1 promoter methylation, mediated by DNA methyltransferases, thereby inhibiting GLIPR1 expression. High expression of GLIPR1 reduces 5-FU sensitivity in 5-FU-resistant CRC cell lines, which abolished the impact of BDH2 expression. These results suggest that BDH2 inhibits GLIPR1 expression by increasing GLIPR1 promoter methylation, thereby enhancing 5-FU sensitivity of 5-FU-resistant CRC cell lines and inhibiting CRC progression.