Hypoxia-inducible factor-1 promotes cancer progression through activating AKT/Cyclin D1 signaling pathway in osteosarcoma

Objective: Osteosarcoma is an aggressive malignant neoplasm, which commonly afflicts patients of 20-30 years of age, and its morbidity has increased markedly in recent years. Certain genes and signal pathways have been identified to exert key roles in osteosarcoma progression. Here, we set out to characterize in more detail of the role of HIF-1/AKT/Cyclin D1 pathway in the progression of osteosarcoma. Methods: Immunohistochemistry, western blot and qPCR were used to test the protein or mRNA levels of HIF-1 in osteosarcoma tissues or adjacent nontumor tissues. MTT, clone formation, wound healing, Transwell, in vivo tumorigenesis, flow cytometry and western blot analysis were used to determine cell proliferation, clone formation ability, migration, invasion, tumorigenesis, and cell apoptosis in MG63 and U2OS cells, respectively. Immunoprecipitation and immunofluorescence assays were performed to investigate the protein-protein interaction between HIF-1 alpha and proteins related to signal pathways. Results: HIF-1 was overexpressed in osteosarcoma tissues and cell lines, which promoted cell proliferation, clone formation, migration, invasion and inhibited cell apoptosis. Results also demonstrated that HIF-1 combined with AKT, and there might be a positive loop between the two proteins of HIF-1 and AKT, then the protein-protein interaction up-regulated the expression of Cyclin Dl in protein level, but not mRNA level, made Cyclin Dl protein more stable, triggered cell proliferation, clone formation, tumorigenesis, but inhibited cell apoptosis. Conclusions: The present study showed that HIF-1 modulated Cyclin Dl expression might through shaping a positive loop with AKT proteins. Additionally, HIF-l alpha promoted the tumor cells growth, migration and invasion in osteosarcoma through the activation of the AKT/Cyclin D1 signal cascade. We proposed that HIF-1 could be served as a marker for distinguishing osteosarcoma and an effective therapeutic target for osteosarcoma.