Cell proliferation and apoptosis assay in the cervical cancer cells. (A) MTS assay in SKG-II, HCS-2 and HeLa cells. Cell proliferation was suppressed by transient transfection of the miR-331-3p precursor. (pre: precursor, * p < 0.05 (24 h), + p < 0.05 (48 h), # p < 0.05 (72 h)); (B) TdT-mediated dUTP nick end labeling (TUNEL) assay for SKG-II, HCS-2 and HeLa cells. The Y-axis shows the number of positive cell counts per 10 or 20 high-power fields (10 or 20 HPFs). Positive cells were induced by transfection of the miR-331-3p precursor (* p < 0.05); (C) Expression of miR-331-3p was up-regulated in SKG-II, HCS-2 and HeLa cells by miR-331-3p precursor transfection compared to control cells (* p < 0.05).