Circular RNA pyridoxal kinase (circPDXK) involves in the progression of ovarian cancer and glycolysis via regulating miR-654-3p and hexokinase II

Background: Circular RNA pyridoxal kinase (circPDXK; hsa_circ_0061893) is newly identified to be aberrantly expressed in ovarian cancer (OVCA); however, its functional role in OVCA cells remains to be expounded. Methods: Real-time quantitative polymerase chain reaction, western blotting, and immunohistochemistry quantified RNA and protein expression levels. MiRNA binding site prediction tools predicted direct interaction between two RNAs, and dual-luciferase reporter and RNA immunoprecipitation assays further confirmed that prediction. Cell-counting kit-8, colony formation, and 5-ethynyl-2MODIFIER LETTER PRIME-deoxyuridine assays measured cell growth; nude mice xenograft tumor experiment detected tumor growth. Transwell and Annexin V-fluorescein isothiocyanate/propidium iodide staining assays evaluated cell motility and apoptosis. Glycolysis process was determined by glucose uptake, lactate, and ATP assay kits. Results: CircPDXK is highly expressed in OVCA patients' tumor tissues and cells, concomitant with microRNA (miR)-654-3p downregulation and hexokinase II (HK2) upregulation. RNA interference of circPDXK could restrain cell viability, colony formation, DNA synthesis, migration, invasion, and glycolysis of OVCA cells, but also retard xenograft tumor growth. Allied with those are higher apoptosis rate, elevated Bax and E-cadherin levels, and depressed ki67 and HK2 levels. Compared to circPDXK inhibition, restoration of miR-654-3p functions analogical effects in OVCA cells in vitro. Mechanistically, there are direct interactions between miR-654-3p and circPDXK or HK2; moreover, miR-654-3p inhibition could weaken the functional roles of circPDXK interference in OVCA cells, and either HK2 ectopic expression abrogates the effects of miR-654-3p overexpression. Conclusion: CircPDXK/miR-654-3p/HK2 axis could be a novel molecular mechanism of OVCA progression and glycolysis, and targeting circPDXK might overcome OVCA.

Automated summary

The circular RNA pyridoxal kinase circPDXK is highly expressed in ovarian cancer, affecting cell viability, migration, invasion, and glycolysis processes by regulating miR-654-3p and HK2. MiR-654-3p functions analogically to circPDXK by inhibiting its expression.