CircPRDM2 Contributes to Doxorubicin Resistance of Osteosarcoma by Elevating EZH2 via Sponging miR-760

Abstract

Background Circular RNAs (circRNAs) are implicated in the chemoresistance of human cancers. However, the functions of circRNA PR/SET domain 2 (circPRDM2) in the resistance of osteosarcoma (OS) to doxorubicin (DXR) are unknown. Methods Quantitative real-time polymerase chain reaction (qRT-PCR) assay was conducted to determine the levels of circPRDM2, microRNA-760 (miR-760) and enhancer of zeste homolog 2 (EZH2). RNase R assay was used to analyze the characteristics of circPRDM2. IC50 of DXR was estimated by Cell Counting Kit-8 (CCK-8) assay. Colony formation assay was performed for cell colony formation ability. Wound-healing assay and transwell assay were utilized for cell migration and invasion. Flow cytometry analysis was conducted for cell apoptosis. Western blot assay was employed for protein levels. Dual-luciferase reporter assay, RNA immunoprecipitation (RIP) assay and RNA pull-down assay were adopted to analyze the relationships among circPRDM2, miR-760 and EZH2. Murine xenograft model assay was utilized to explore DXR resistance in vivo. Results CircPRDM2 level was enhanced in DXR-resistant OS tissues and cells. CircPRDM2 deficiency inhibited IC50 of DXR, colony formation, migration and invasion and facilitated apoptosis in DXR-resistant OS cells in vitro. CircPRDM2 was identified as the sponge for miR-760. MiR-760 inhibition reversed the inhibitory effects of circPRDM2 knockdown on DXR resistance and cell progression in DXR-resistant OS cells. Moreover, EZH2 was identified as the target gene of miR-760 and EZH2 overexpression abolished miR-760-mediated impacts on DXR sensitivity and malignant behaviors in DXR-resistant OS cells. Also, circPRDM2 silencing improved DXR sensitivity in vivo. Conclusion Our study demonstrated the role of circPRDM2/miR-760/EZH2 axis in enhancing DXR resistance.

CircDOCK1 promotes the tumorigenesis and cisplatin resistance of osteogenic sarcoma via the miR-339-3p/IGF1R axis

“…Our bioinformatics analysis and experimental verification showed high expression of circDOCK1 in OS tissues and cell lines, suggesting that circDOCK1 may be a regulator of OS progression. Moreover, circRNAs are involved in all pathophysiological processes involved in OS development and treatment, including proliferation, apoptosis and chemoresistance [ 39 – 41 ]. Our study revealed that overexpression of circDOCK1 promoted the proliferation, migration, invasion and chemoresistance of OS cells in vitro and inhibited apoptosis, as validated in xenograft and lung metastasis experiments in vivo.…”

The strategy and clinical relevance of in vitro models of MAP resistance in osteosarcoma: a systematic review

“…Whilst in DOX resistant models upregulation of OIP5-AS1 inhibited miR-200b-3p resulting in overexpression of fibronectin 1 ( FN1 ) [ 61 ]. In DOX resistant models circPRMD2 sponged miR-760 leading to overexpression of the transcriptional represser enhancer of zeste homologue 2 ( EZH2 ) [ 66 ] whilst LINC01116 interacted with EZH2 to inhibit miR-424-5p causing upregulation of non-histone chromosomal mobility group AT hook ( HMGA2 ) and the promotion of cell migration factors [ 55 ]. Autophagy was also regulated by ncRNAs with diminished levels of miR-30a in one model leading to the upregulation of autophagy markers beclin-1 ( BECN1 ) and microtubule associated protein LC3-II [ 65 ].…”

“…Six studies were discovery driven using techniques to validate resistance markers identified by microarray [43,44,46,50,51] or gene amplification and copy number studies [34], whilst 30 studies were candidate driven. Expression is reported for; 80 genes in 30 models using qPCR [34, 36, 37, 41-44, 46-50, 52-61], 25 proteins in 19 models by western blot or flow cytometry [35,36,47,53,55,57,58,[61][62][63][64][65][66], and 25 ncRNAs in 16 models using qPCR [44,51,55,59,61,62,[65][66][67][68][69][70][71][72][73]. Gene expression analysis was completed across all cell lines, strategies and MAP drugs whilst, protein and ncRNA analysis was not performed in the HOS, SOSP-9607 or 143b cell lines.…”

Advances in the Study of CircRNAs in Tumor Drug Resistance

“…Most of them continue to regulate the expression of downstream signaling pathways by affecting the stability or degradation of target proteins, and there is often more than one downstream pathway involved ( 30 , 124 ). Although the RBP pathway is different from pathways influenced by circRNA regulation of the target gene, in essence, it continues to play its biological function by regulating the expression (by targeting genes) or degradation (by targeting proteins) of related proteins.It is worth mentioning that there are also reports that circRNA directly binds to the DNA promoter to regulate transcription and thus affect the progression of liver cancer ( 84 , 187 ).…”