Chimaphilin inhibits proliferation and induces apoptosis in multidrug resistant osteosarcoma cell lines through insulin-like growth factor-I receptor (IGF-IR) signaling

Chimaphilin, an active compound separated from pyrola, possesses the highly efficient antitumor activities. Insulin-like growth factor-I receptor (IGF-IR) plays an important role in tumor cell survival. To look for effective strategies for interrupting IGF-IR signaling pathway, we found that chimaphilin can inhibit the receptor tyrosine kinase activity of IGF-IR. Chimaphilin inhibited the growth of both drug-sensitive and drug-resistant osteosarcoma cell lines in a time and dose-dependent manner; however, it showed relatively little toxicity in normal osteoblast cell lines. Chimaphilin can increase the sensitivity of doxorubicin in doxorubicin-resistant osteosarcoma cell lines. Additionally, small interfering RNA downregulation of IGF-IR expression in drug-resistant cell lines also caused resensitization to doxorubicin. Above all, we conclude that chimaphilin represents a valuable natural source and may potentially be applicable for reversing the drug-resistant phenotype in osteosarcoma therapy.