Amplification and up-regulation of microRNA-30b in oral squamous cell cancers

MicroRNAs (miRNAs) are negative regulators of protein coding genes which are frequently deregulated in mammary cancers. Over-expression of microRNA-30b (hsa-miR-30b) is implicated in tumour invasion and immunosuppression during metastasis. The chromosome locus of MIR30B gene, 8q24, is frequently amplified in oral squamous cell cancers (OSCCs). In the present study, we aimed to investigate the copy number variations as well as expression levels of MIR30B gene in OSCCs and analyse their correlation with tumour stage. Quantitative real-time PCR was performed to examine the copy number of MIR-30B gene as well as hsa-miR-30b expression in 107 OSCC samples with matched adjacent normal tissues. Proportional odds regression and two-way repeated measurement ANOVA were used to analyse the association between copy number variations (CNVs) and hsa-miR-30b expression. Copy number gains of MIR-30B gene were detected in a relatively large percentage of the OSCC samples (27.1%, 29 out of 107) and were correlated with tumour stages (p < 0.001). MIR30B gene amplification also showed a close correlation with hsa-miR-30b over-expression in OSCCs (p < 0.001). On the other hand, enhanced miR-30b expression was also detected in a group of OSCC samples with unaltered copy number of MIR30B gene. Copy number increase of MIR30B is frequent in advanced OSCC and is correlated with hsa-miR-30b over-expression. Sporadic OSCCs can exhibit different mechanisms of MIR30B regulation.