miR-5000-3p confers oxaliplatin resistance by targeting ubiquitin-specific peptidase 49 in colorectal cancer.

Colorectal cancer (CRC) is the most common form of gastrointestinal malignancies. A growing number of reports focusing on oxaliplatin (OXA) resistance in CRC treatment have revealed that drug resistance is an urgent issue in clinical applications, especially for finding effective therapeutic targets. Recently, microRNAs (miRNAs) are reported to play a critical role in tumor progressions and multi-drug resistance. The main aim of this study is to establish whether miR-5000-3p is an oncogene that is resistant to OXA and further confirm its underlying regulatory role in CRC. The OXA-associated gene expression dataset in CRC cells was downloaded from Gene Expression Omnibus (GEO) database. Statistical software R was used for significance analysis of differentially expressed genes (DEGs) between OXA-resistant (OR)-CRC cells and CRC cells, and results indicated ubiquitin-specific peptidase 49 (USP49) was upregulated in OR-CRC cells. Luciferase reporter assay showed that USP49 was verified to act as a downstream target gene of miR-5000-3p. From the results of TCGA database, miR-5000-3p expression was upregulated and USP49 was downregulated in patients with CRC. The function of miR-5000-3p was detected using MTT assay, wound healing, Transwell, and flow cytometry assays. Moreover, through in vitro and in vivo experiments, miR-5000-3p expression was confirmed to be upregulated in CRC cells or OR-CRC cells comparing to normal cell lines. Molecular mechanism assays revealed that USP49 binds to the miR-5000-3p promoter to increase the expression of miR-5000-3p, resulting in cancer cells sensitized to OXA. To sum up, these results suggest that miR-5000-3p may be a novel biomarker involved in drug-resistance progression of CRC. Moreover, the drug-resistance mechanism of miR-5000-3p/USP49 axis provides new treatment strategies for CRC in clinical trials.