Thymoquinone inhibits proliferation and invasion of human nonsmall-cell lung cancer cells via ERK pathway

Thymoquinone (TQ) is the primary bioactive component of Nigella sativa Linn seed oil and used as anti-inflammatory, anti-oxidant, and anti-neoplastic agent. Previous studies have shown that TQ exhibits inhibitory effects on multiple cancers. However, the detailed antineoplastic effects and its molecular mechanisms of TQ on lung cancer are not entirely elucidated yet. In the present study, we aimed to investigate the effects of TQ on cell proliferation, migration, and invasion as well as its underlying anti-metastatic mechanisms in A549 cells. Lung cancer cell line A549 cells were treated with different concentration of TQ for different period of time, and the growth-inhibitory effects of TQ was measured by MTT and cell count assays; cell cycle was determined by flow cytometry; wound healing and transwell assays were used to assess the cell migration and invasion activities; Western blot and real-time quantitative RT-PCR were used to determine the expression of proliferation and invasion associated genes as well as MAPKs pathway molecules; gelatinase activity was estimated using gelatin zymography assay. The results show that TQ played a role in inhibiting the proliferation, migration, and invasion of A549 lung cancer cells, it also inhibited the expression level of PCNA, cyclin D1, MMP2, and MMP9 mRNA and protein in a dose-and time-dependent manner especially at 10, 20, 40 mu mol/L concentrations. The cell cycle inhibitor P16 expression and the gelatinase activities of MMP2 and MMP9 were also inhibited by TQ dramatically. TQ reduced phosphorylation of ERK1/2; however, the proliferation and invasion inhibitory effects of TQ on A549 cells were neutralized by ERK1/2 inhibitor PD98059. In conclusion, our study confirmed that TQ could inhibit A549 cell proliferation, migration, and invasion through ERK1/2 pathway, as proposed the therapeutic potential of TQ as an anti-metastatic agent in human lung cancer treatment.