Circular RNAs (circRNAs) represent a widespread class of non-coding RNAs generated from back-splicing, with a circular loop structure. Many circRNAs have been reported to play essential roles in cancer development and have the potential to serve as a novel class of biomarkers for clinical diagnosis. However, the role of circRNA in osteosarcoma (OS) remains largely unknown. In the current study, we examined the expression level of circular RNA PVT1 (circPVT1), previously screened and identified the oncogenic role in gastric cancer, in OS and found that circPVT1 was significantly up-regulated in the OS tissues, serums and chemoresistant cell lines, correlated with poor prognosis of OS patients. Besides, ROC curve demonstrated that circPVT1 may be a better diagnostic biomarker than alkaline phosphatase (ALP) in OS with more sensitivity and specificity. In addition, functional assays revealed that circPVT1 knockdown by siRNA could weaken the resistance to doxorubicin and cisplatin of OS cells through decreasing the expression of classical drug resistance-related gene ABCB1. These findings may provide a new insight into the role of circPVT1 as a biomarker for the diagnosis and treatment target of OS.

Chemo-resistance is a huge obstacle encountered in the osteosarcoma (OS) treatment. Protein-coding mRNAs, as well as non-coding RNAs (ncRNAs), including long ncRNA (lncRNA), circular RNA (circRNA), and microRNA (miRNA), have been demonstrated to play an essential role in the regulation of cancer biology. However, the comprehensive expression profile and competing endogenous RNA (ceRNA) regulatory network between mRNAs and ncRNAs in the OS chemo-resistance still remain unclear. In the current study, we developed whole-transcriptome sequencing (RNA sequencing [RNA-seq]) in the three paired multi-drug chemo-resistant and chemo-sensitive OS cell lines to comprehensively identify differentially expressed lncRNAs, circRNAs, miRNAs, and mRNAs. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were performed for mRNAs with significantly different expression. Then the ceRNA networks combining lncRNAs, circRNAs, miRNAs, and mRNAs were predicted and constructed on the basis of the authoritative miRanda and TargetScan databases combined with the widely accepted vital drug resistance-related genes and signal transduction pathways. In addition, two constructed ceRNA regulatory pathways, lncRNAMEG3/hsa-miR-200b-3p/AKT2 and hsa_circ_0001258/hsa-miR-744-3p/GSTM2, were randomly selected and validated by real-time qPCR, RNA immunoprecipitation (RIP), RNA pull-down assay, and dual luciferase reporter gene system. Taken together, our findings may provide new evidence for the underlying mechanism of OS chemo-resistance and uncover some novel targets for reversing it.

LncRNA FENDRR sensitizes doxorubicin-resistance of osteosarcoma cells through down-regulating ABCB1 and ABCC1 LncRNA FENDRR sensitizes doxorubicin-resistance of osteosarcoma cells through down-regulating ABCB1 and ABCC1

Aim: To identify circular RNAs (circRNAs) related to osteosarcoma (OS) chemoresistance. Materials & methods: CircRNA expression profile was performed in three paired human chemoresistant and chemosensitive OS cell lines by next-generation sequencing. Quantitative real-time-PCR (qRT-PCR) was used to confirm next-generation sequencing data. Bioinformatics analysis was conducted to predict their functions. Results: Eighty circRNAs were dysregulated in the chemoresistant OS cells compared with the control, after validated by qRT-PCR. Bioinformatics analysis showed that some pathways related to drug metabolism were significantly enriched. Additionally, hsa_circ_0004674 was distinctly increased in OS chemoresistant cells and tissues, related to poor prognosis. CircRNA-miRNA-mRNA pathways related to hsa_circ_0004674 were constructed by TargetScan and miRanda. Conclusion: CircRNAs may play a role in OS chemoresistance and hsa_circ_0004674 might be a candidate target.