Inhibition of miRNA‑21 attenuates the proliferation and metastasis of human osteosarcoma by upregulating PTEN

Abstract

The present study aimed to investigate the expression of micro (mi)RNA‑21 in osteosarcoma cells, and its role in inhibiting the invasion and metastasis of osteosarcoma. Human osteosarcoma MG‑63 cells and osteoblast hFOB1.19 cells were used to compare the expression of miRNA‑21 using reverse transcription‑quantitative polymerase chain reaction analysis. A miRNA‑21 mimic or inhibitor were transfected into the MG‑63 cells to upregulate and downregulate the expression of miRNA‑21, respectively. The present study investigated the proliferation and invasion of transfected MG‑63 cells using MTT and Transwell assays. Western blot analyses were used to investigate the regulation of important proteins in the phosphatase and tensin homolog/phosphoinositide 3‑kinase/RAC‑α serine/threonine‑protein kinase (PTEN/PI3K/AKT) signaling pathway. Compared with hFOB1.19 cells, miRNA‑21 expression was significantly upregulated in the MG‑63 cells (P<0.01), which lead to increased proliferation. Downregulating miRNA‑21 expression reduced the proliferation of MG‑63 cells compared with hFOB1.19 cells. Invasion assays and western blot analyses revealed that the overexpression of miRNA‑21 significantly enhanced the invasion ability of MG‑63 cells and the expression of phosphorylated (p‑)AKT, while downregulation of miRNA‑21 expression reduced the protein level of AKT and p‑AKT. In the MG‑63 cells, miRNA‑21 upregulation significantly inhibited the protein level of PTEN, resulting in significantly increased AKT and PI3K protein levels (P<0.01). In conclusion, the results of the present study indicate that the expression of miRNA‑21, PI3K and AKT is increased in the osteosarcoma cell line MG‑63, which results in reduced expression of PTEN and increased expression of proteins in the PI3K/AKT signaling pathway, and thus increases the aggressiveness of osteosarcoma cells.