In their study, miR-483-3p, which may participate in apoptosis and cell proliferation regulation, was found up-regulated in 4 platinum resistant variants, particularly in the IGROV-1/Pt1 subline, versus parental cells. Transfection of a synthetic precursor of miR-483-3p in IGROV-1 parental cells elicited a marked up-regulation of the miRNA levels. Growth-inhibition and colony-forming assays indicated that miR-483-3p over-expression reduced cell growth and conferred mild levels of cisplatin resistance in IGROV-1 cells, by interference with their proliferative potential.
Using LC Sciences target prediction analysis, the targets of miR-483-3p included PRKCA (encoding PKC-alpha), previously reported to be associated to platinum-resistance in ovarian carcinoma. Researchers found that miR-483-3p directly targeted PRKCA in IGROV-1 cells. In keeping with this finding, cisplatin sensitivity of IGROV-1 cells decreased upon molecular/pharmacological inhibition of PKC-alpha.
Overall, these results suggest that overexpression of miR-483-3p by ovarian carcinoma platinum-resistant cells may interfere with their proliferation, thus protecting them from DNA damage induced by platinum compounds and ultimately representing a drug-resistance mechanism. The impairment of cell growth may account for low levels of drug resistance that could be relevant in the clinical setting.
Expression of miR-483-3p and cisplatin sensitivity after transfection with the miR-483-3p inhibitor in IGROV-1/Pt1 cells
(a) Bar graph showing expression levels of miR-483-3p at different time points (24, 48 and 72 h) after transfection with the miR-483-3p inhibitor. Data are reported as Relative Quantification (RQ). The small RNA SNORD48 was used as endogenous control to normalize qRT-PCR data. Untransfected cells were used as calibrator. P < 0.05 by two-side Student’s t-test of Negative Control versus miR-483-3p transfected cells (48 h). (b) Untrasfected cells (circle), Negative Control- (square) or miR-483-3p inhibitor- (triangle) transfected cells were treated with cisplatin for 1 h, and counted 72 h later. Values are the mean (± SD, standard deviation) of at least three independent experiments.