Growth inhibition of Saos-2 osteosarcoma cells by lactucopicrin is mediated via inhibition of cell migration and invasion, sub-G1 cell cycle disruption, apoptosis induction and Raf signalling pathway

Purpose: Lactucopicrin, a sesquiterpene lactone, has been reported to exhibit anticancer activity against different cancer types. In this study, the anticancer effect of Lactucopicrin was examined against human osteosarcoma cells along with its effects on cell migration and invasion, cell cycle phase distribution and Raf signalling pathway. Methods: The human osteosarcoma cells Sao-2 were treated with various concentrations of Lactucopicrin for 24 h. The anti-proliferative effects of Lactucopicrin were measured by CCK8 cell viability assay. Acridine orange (AO)/ ethidium bromide (EB) and annexin V/propidium iodide (PI) assays were employed to examine the induction of apoptosis. Transwell assay was performed to examine the cell migration and invasion. Protein expression analysis was performed by western blot analysis. Results: Lactucopicrin inhibited the proliferation of Saos-2 cells and exhibited an IC50 of 25 mu M. The antiproliferative effects were due to induction of apoptosis as indicated by AO/EB staining. Moreover, the annexin V/PI staining showed that the percentage of the apoptotic cells increased with increase in the concentration of Lactucopicrin. The induction of apoptosis was also related to upregulation of Bax and downregulation of Bcl-2. Lactopucrin also caused arrest of the osteosarcoma cells at the sub-G1 phase of the cell cycle. Transwell assay showed that Lactucopicrin inhibited the migration and invasion of the Saos-2 cells. Finally, Lactucopicrin also blocked the Raf signalling pathway in the Saos-2 cells in a concentration-dependent manner. Conclusions: Lactucopicrin exhibits significant antiproliferative effects on the osteosarcoma cells and may prove essential in the development of systemic therapy for this malignancy.