Upregulation of CRABP2 by TET1-mediated DNA hydroxymethylation attenuates mitochondrial apoptosis and promotes oxaliplatin resistance in gastric cancer

Oxaliplatin is the main chemotherapy drug for gastric cancer (GC), but quite a few patients are resistant to oxaliplatin, which contributes to the poor prognosis of GC patients. There is therefore an urgent need to identify potential targets for reversing chemotherapy resistance in GC patients. In this study, we analyzed the tumor samples of GC patients who received neoadjuvant chemotherapy based on oxaliplatin through quantitative proteomics and identified the potential chemoresistance-related protein cellular retinoic acid binding protein 2 (CRABP2). CRABP2 was significantly upregulated in the tumor tissues of chemoresistant GC patients and was closely related to prognosis. The results of cell function experiments showed that CRABP2 can promote the oxaliplatin resistance of GC cells in vitro. Coimmunoprecipitation and GST pulldown assays showed that CRAPB2 expedited the binding of BAX and PARKIN in GC cells and facilitated the ubiquitination-mediated degradation of BAX. Furthermore, both the in vitro assay and cell-derived xenograft (CDX) in vivo model verified that CRABP2 promoted oxaliplatin resistance by inhibiting BAX-dependent cell apoptosis. Further experiments proved that the abnormally high expression of CRABP2 in oxaliplatin-resistant GC cells was affected by TET1-mediated DNA hydroxymethylation. The patient-derived xenograft (PDX) model suggested that interference with CRABP2 reversed oxaliplatin resistance in GC in vivo. In conclusion, the results of our study show that CRABP2 was a key molecule in oxaliplatin resistance regulation and could be a new target for reversing the chemoresistance of GC.