miR-375 exhibits a more effective tumor-suppressor function in laryngeal squamous carcinoma cells by regulating KLF4 expression compared with simple co-transfection of miR-375 and miR-206

MicroRNAs (miRNAs) are reported to be important regulators of cancer-related processes, and function either as oncogenes or as tumor-suppressor genes. It was found that miR-375 was downregulated in samples of laryngeal squamous cell carcinomas (LSCCs) as compared to the level noted in adjacent non-tumor tissues, and it was inversely correlated with T grade, lymph node metastases and clinical tumor stage. Overexpression of miR-375 led to a decreased protein level of Krüppel-like factor 4 (KLF4) and marked suppression of the proliferation and invasion, and induced apoptosis of LSCC cell line Hep-2 using Cell Counting Kit-8, Transwell chamber and cell cycle assays. In addition, we examined the influence of the upregulation of miR-206 alone and upregulation of both miR-375 and miR-206 on the expression of KLF4 and Hep-2 cell behavior. The results showed that compared with the function of miR-375 in tumor suppression by regulating KLF4, co-transfection of miR-375 and miR-206 exhibited a less effective inhibitory effect not only on tumor cell proliferation and invasion, but also on tumor cell apoptosis. Taken together, miR-375 is possibly a tumor suppressor in LSCC by regulating KLF4. In addition, simple overexpression of several miRNAs did not entail higher efficacy than a single miRNA, similar to co-transfecions of miR-375 and miR-206.