Tramadol regulates proliferation, migration and invasion via PTEN/PI3K/AKT signaling in lung adenocarcinoma cells

OBJECTIVE: Tramadol is used mainly for the treatment of moderate to severe chronic cancer pain. However, the effect of tramadol on lung cancer remains unclear. Therefore, it is important to explore the mechanism accounting for the function of tramadol on lung cancer. MATERIALS AND METHODS: We investigated the effects of tramadol on the proliferation, migration and invasion in human lung adenocarcinoma cells in vitro by CCK-8 assay, wound healing assay and Transwell assay, respectively. We also explored the potential mechanism of tramadol on lung cancer cells by Western blotting. RESULTS: A549 and PC-9 cells were incubated with 2 mu M tramadol for different time (0, 7, 14 and 28 d). The in vitro experiments showed that tramadol treatment significantly inhibited cell proliferation, migration and invasion in a time-dependent manner. Moreover, administration of tramadol suppressed tumor growth in vivo. The data also revealed that tramadol could up-regulate the protein expression level of PTEN and consistently inhibit the phosphorylation level of PI3K and Akt, whereas the total level of PI3K and Akt remain unchanged. CONCLUSIONS: These findings indicated that tramadol inhibited proliferation, migration and invasion of human lung adenocarcinoma cells through elevation of PTEN and inactivation of PI3K/Akt signaling.