Background: Long non-coding RNAs (lncRNAs) function as a class of significant mediators in prostate cancer (PCa), and this study mainly discussed the molecular mechanism of lncRNA growth arrest-specific 5 (GAS5) in PCa progression and radiosensitivity.
Materials and Methods: GAS5 and microRNA-320a (miR-320a) levels were determined by quantitative real-time polymerase chain reaction (qRT-PCR). Cell viability and migration were severally examined through 3-(4, 5-dimethylthiazol-2-y1)-2, 5-diphenyl tetrazolium bromide (MTT) and transwell assays. PCa cells were treated with X-ray irradiation. Cell survival and apoptosis rate were assayed using colony formation assay and flow cytometry, respectively. The apoptosis-related protein and Rab GTPase 21 (RAB21 ) protein levels were measured by Western blot. The relation between miR-320a and GAS5 or RAB21 was assessed via the dual-luciferase reporter assay. The effect of GAS5 on radiosensitivity of PCa in vivo was evaluated by xenotransplantation assay.
Results: GAS5 was down-regulated in PCa tissues and cells. GAS5 overexpression suppressed cell viability and migration while facilitated radiosensitivity of PCa cells. GAS5 was a molecular sponge of miR-320a. The effects of GAS5 up-regulation on PCa cells were accomplished by sponging miR-320a. MiR-320a targeted RAB21  and GAS5 up-regulated RAB21  expression via targeting miR-320a. RAB21  knockdown reversed the effects of miR-320a inhibition on PCa cells. GAS5 promoted the radiosensitivity of PCa by the miR-320a/RAB21  axis in vivo.
Conclusion: Collectively, GAS5 restrained tumor development and expedited the radiosensitivity in PCa by the miR-320a/RAB21  axis, which provided a molecular regulatory mechanism of GAS5/miR-320a/RAB21  in PCa development and radioresistance.
Keywords: GAS5, prostate cancer, radiosensitivity, miR-320a, RAB21