MicroRNA‐378‐3p/5p represses proliferation and induces apoptosis of oral squamous carcinoma cells via targeting KLK4

Abstract Oral squamous cell carcinoma (OSCC) is one of the most common types of head and neck neoplasm. Down‐regulation of hsa‐microRNA‐378 (miR‐378) has been proved in OSCC tissues, suggesting that miR‐378 might play crucial roles in the progression of OSCC. The present study aimed to evaluate the effect of miR‐378‐3p/5p on the proliferation and apoptosis of OSCC in vitro and in vivo. According to the results, lentivirus‐mediated overexpression of miR‐378 lowered the colony formation efficiency, blocked cell cycle progression, and decreased the percentage of Ki‐67 positive cells, whereas knockdown of miR‐378‐3p/5p led to the opposite results. Furthermore, the apoptosis of OSCC cells was induced by the overexpression of miR‐378 as evidenced by decreasing Bcl‐2/Bax ratio, increasing cleaved caspase‐9, cleaved caspase‐3, and cleaved PARP levels, and promoting the release of cytochrome c into the cytoplasm. However, the above results were reversed by miR‐378‐3p/5p silencing. In addition, the overexpression of miR‐378 inhibited the activation of PI3K/AKT signalling pathway. Conversely, miR‐378‐3p/5p knockdown resulted in the inactivation of PI3K/AKT signalling pathway. Mechanically, we validated that miR‐378‐3p/5p could target kallikrein‐related peptidase 4 (KLK4), and enforced overexpression of KLK4 counteracted miR‐378 overexpression‐induced apoptosis. Finally, tumourigenesis in nude mice was suppressed by the overexpression of miR‐378, which was promoted by miR‐378‐3p/5p silencing. Taken together, these results suggest that miR‐378 may be a potential target in the diagnoses and treatment of OSCC.