Co‑inhibition of miRNA‑21 and miRNA‑221 induces apoptosis by enhancing the p53‑mediated expression of pro‑apoptotic miRNAs in laryngeal squamous cell carcinoma.

Dysregulation of a numerous microRNAs (miRNAs) has been implicated in laryngeal squamous cell carcinoma (LSCC). Among those miRNAs, miR-21 and miR-221 are co-overexpressed and commonly target the phosphatase and tensin homolog protein (PTEN) that is located in the PTEN-Akt signaling pathway. The present study investigated whether co-inhibition of miR-21 and miR-221 induced synergistic apoptosis of human LSCC cells. Methyl thiazolyl tetrazolium (MTT) and terminal deoxynucleotidyl-transferase-mediated deoxynucleotide triphosphate nick end labeling (TUNEL) assays were used to observe the potential effect of miR-21 and miR-221 on cell viability and apoptosis in cells co-transfected with anti-miRNA oligonucleotide (AMO)-21 and AMO-221. The protein expression levels of PTEN, Akt and p53 were determined by western blotting. The cellular abundance of 6 pro-apoptotic miRNAs transcribed by p53 mediation, consisting of miR-15a, miR-16-1, miR-26a, miR-34a, miR-143 and miR-203, was measured with using reverse transcription-quantitative polymerase chain reaction (RT-qPCR). MTT results indicate that in vitro co-transfection of AMO-21 and AMO-221 leads to a decline in cell viability, compared with the transfection of AMO alone. This result was verified by the detection of apoptosis using TUNEL assays. Co-transfection of AMO-21 and AMO-221 resulted in a marked reduction in Akt phosphorylation and enhanced expression of PTEN and p53 were observed; consequently, leading to an amplification of the transcription of 6 pro-apoptotic miRNAs. The present findings confirmed that co-inhibition of miR-21 and miR-221 synergistically triggers cell apoptosis in vitro. The altered PTEN-Akt signaling and p53-mediated amplification of the transcription of pro-apoptotic miRNAs may be involved in the observed synergistic effect. The present study provides novel insights into the mechanism underlying apoptosis-associated miRNA-miRNA mutual regulation in LSCC.