Abstract
Bufalin is the primary component of the traditional Chinese herb “Chan Su”. Evidence suggests that this compound possesses potent anti-tumor activities, although the exact molecular mechanism(s) is unknown. Our previous study showed that bufalin inhibited growth of human osteosarcoma cell lines U2OS and U2OS/MTX300 in culture. Therefore, this study aims to further clarify the in vitro and in vivo anti-osteosarcoma effects of bufalin and its molecular mechanism of action. We found bufalin inhibited both methotrexate (MTX) sensitive and resistant human osteosarcoma cell growth and induced G2/M arrest and apoptosis. Using a comparative proteomics approach, 24 differentially expressed proteins following bufalin treatment were identified. In particular, the level of an anti-apoptotic protein, heat shock protein 27 (Hsp27), decreased remarkably. The down-regulation of Hsp27 and alterations of its partner signaling molecules (the decrease in p-Akt, nuclear NF-κB p65, and co-immunoprecipitated cytochrome c/Hsp27) were validated. Hsp27 over-expression protected against bufalin-induced apoptosis, reversed the dephosphorylation of Akt and preserved the level of nuclear NF-κB p65 and co-immunoprecipitated Hsp27/cytochrome c. Moreover, bufalin inhibited MTX-resistant osteosarcoma xenograft growth, and a down-regulation of Hsp27 in vivo was observed. Taken together, bufalin exerted potent anti-osteosarcoma effects in vitro and in vivo, even in MTX resistant osteosarcoma cells. The down-regulation of Hsp27 played a critical role in bufalin-induced apoptosis in osteosarcoma cells. Bufalin may have merit to be a potential chemotherapeutic agent for osteosarcoma, particularly in MTX-resistant groups.
Highlights
Osteosarcoma is the most common primary malignant bone tumor in young people, with an annual incidence of 5.6 per million [1]
Bufalin exerted a timeand dose-dependent inhibition to all osteosarcoma cell lines (Figure 1A). These initial results suggested that bufalin inhibited the viability of various human osteosarcoma cells in vitro, which includes the MTX resistant cell line U2-OS/MTX300
The results revealed a decrease in the expression of heat shock protein 27 (Hsp27) in the bufalin treatment groups, while an increase was noted in the MTX group, as compared to the vehicle (Figure 6D)
Summary
Osteosarcoma is the most common primary malignant bone tumor in young people, with an annual incidence of 5.6 per million [1]. A considerable number of patients are either not sensitive to chemotherapy or develop drug resistance [3]. One strategy to overcome this problem is to find alternative anti-cancer agents that will increase drug-response rates, avoid chemo-resistance, and improve clinical outcomes [5,6,7]. We demonstrated that bufalin had significant in vitro anti-tumor activity on the U2OS and U2OS MTX300 cell lines [16]. The aim of the current study was to confirm the in vitro and in vivo anti-osteosarcoma effects of bufalin and to determine its mechanism of action to evaluate its potential as an alternative drug in the treatment of osteosarcoma patients
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
