MicroRNA-21 expression is associated with the clinical features of patients with gastric carcinoma and affects the proliferation, invasion and migration of gastric cancer cells by regulating Noxa

The expression levels of microRNA-21 (miR-21) are increased in a number of types of solid tumors. However, the association between miR-21 expression and clinical features of patients with gastric carcinoma, and gastric cancer proliferation, invasion and migration remains to be elucidated. The present study investigated the effect of miR-21 on the clinical features, proliferation, invasion and migration of gastric cancer and the underlying mechanisms associated with Noxa. Reverse transcription quantitative polymerase chain reaction (RT-qPCR) was performed to detect the expression levels of miR-21 and Noxa in samples of gastric cancer tissue and matched, adjacent, non-tumor tissue. The association between miR-21 expression and the clinical features of patients with gastric carcinoma, as well as the correlation between the mRNA and protein expression levels of miR-21 and Noxa were analyzed. SGC-7901 gastric cancer cells were cultured in vitro and transfected with an miR-21 mimic. The effect of miR-21 upregulation on proliferation and the cell cycle was determined using the MTT assay and flow cytometry. In addition, migration and invasion of SGC-7901 cells were observed using the Transwell assay. The target gene of miR-21 was identified using bioinformatics software and a dual luciferase reporting system. The effect of miR-21 upregulation on Noxa expression levels in SGC-7901 cells was also analyzed by RT-qPCR and western blotting. Increased levels of miR-21 expression and decreased levels of Noxa expression were observed in gastric cancer tissue samples when compared with the adjacent non-tumor tissue samples. An increased miR-21 expression level was identified as a risk factor for advanced stage gastric cancer, lymph node metastasis and larger primary tumors. Furthermore, the overexpression of miR-21 inhibited Noxa expression levels in SGC-7901 cells. Therefore, high levels of miR-21 expression may induce gastric cancer migration and invasion via the downregulation of Noxa expression.