Cytochrome b5 reductase 2 is a novel candidate tumor suppressor gene frequently inactivated by promoter hypermethylation in human nasopharyngeal carcinoma.

Cytochrome b5 reductase 2 (CYB5R2), a member of the flavoprotein pyridine nucleotide cytochrome reductase family, is associated with a number of physiological reactions. However, its role in cancer, especially nasopharyngeal carcinoma (NPC), has not been addressed. Here, we investigate the transcript levels and promoter methylation status of CYB5R2 in NPC derived cell lines and tumor biopsies and experimentally address its role as a tumor suppressor gene. We find that CYB5R2 transcript levels are decreased in NPC cell lines and tumor biopsies. Promoter hypermethylation of CYB5R2 was detected in all six tested NPC cell lines and in 84% of primary NPC tumor biopsies but not in normal nasopharyngeal epithelium. Clinically, CYB5R2 methylation was associated with lymph node metastasis in NPC patients (P < 0.05). The endogenous expression of CYB5R2 could be restored in vitro by the methyltransferase inhibitor 5-aza-2'-deoxycytidine in NPC cell lines. Ectopic expression of CYB5R2 had an inhibitory effect on proliferation, clonogenicity and migration of NPC cells. Moreover, in vivo tests in nude mice indicated that ectopic expression of CYB5R2 reduces the tumorigenicity of CYB5R2-negative NPC cells. Collectively, these findings suggest that CYB5R2 may be a functional tumor suppressor gene, frequently inactivated by hypermethylation of its promoter in NPC. We report here the first instance of epigenetic downregulation in NPC tumor biopsies of a key enzyme, CYB5R2, which is responsible for the detoxification of environmental carcinogens. We propose the possibility of utilizing CYB5R2 promoter methylation as a diagnostic biomarker of NPC in the future.

Differentially expressed miR-4310 functions as a tumor suppressor in colorectal cancer.

BACKGROUND: Colorectal cancer (CRC) is a digestive tract malignancy microRNAs (miRNAs) have attracted much attention as biomarkers in tumor studies. OBJECTIVE: This work focused on the predictive potential and mechanism of miR-4310 in CRC. METHODS: The miRNA expression profile sets were obtained from the Gene Expression Omnibus (GEO) database, and the appropriate miRNA was screened by GEO2R. The CRC tissues and control tissues of 88 patients with CRC were collected, and the expression of miR-4310 was detected by quantitative real-time PCR, and the efficacy of miR-4310 in diagnosing CRC was evaluated by the receiver operating characteristic curve (ROC). The effects of miR-4310 on the proliferation, migration, and invasion of CRC cells were explored by Cell Counting Kit-8 (CCK-8) and Transwell experiments. Predicting the potential binding sites of miR-4310 and Runt-related transcription factor 1 (RUNX1) by four predictive websites. The relationship between miR-4310 and RUNX1 was confirmed by a double luciferase reporter gene experiment. RESULTS: The bioinformatics analysis found that miR-4310 was differentially expressed in CRC tissues and this finding was certified by the expression of miR-4310 in CRC tissues of collected patients and cultured CRC cell lines. The expression of miR-4310 had a predictive possibility for CRC patients. MiR-4310/RUNX1 pathway had effects on CRC viability, migration, and invasion. CONCLUSION: MiR-4310 had the potential to be a biomarker for early screening of CRC. MiR-4310 and RUNX1 participated in the regulation of CRC cells.