The HIF-1α/Sema4D axis promotes hypoxia-induced metastasis of human osteosarcoma via PI3K/Akt/mTOR signaling pathway

Abstract Purpose Semaphorin 4D (Sema4D) plays a vital role in varied tumor biological processes. Hypoxia inducible factor-1α (HIF-1α), an essential regulatory factor in tumor microenvironment, mediates hypoxia-induced-oncogenes overexpression during cancer occurrence and development. However, the function of Sema4D and its connection with HIF-1α are not entirely validated in osteosarcoma.Methods RT-qPCR and immunohistochemistry were used to evaluate the differential expression of HIF-1α and Sema4D in human osteosarcoma. The biological function of Sema4D in osteosarcoma malignant phenotype was measured by RNA interference, Cell Counting Kit-8 (CCK-8) assay, Wound healing, Transwell and Tube formation assay. The stable transfected cells were established by lentivirus transfection to observe the biological significance of Sema4D in vivo. The relation between HIF-1α and Sema4D was explored through dual luciferase report assay.Results This study showed HIF-1α and Sema4D expression levels were upregulated in human osteosarcoma samples and cell lines. Sema4D knockdown in 143B and MG63 cells restrained cell growth, migration and invasiveness via suppressing PI3K/Akt/mTOR signaling pathway. The tube formation capability of HUVEC was inhibited after coculture with low tumor-derived Sema4D. Besides, knockdown of Sema4D suppressed tumor growth in the xenograft tumor models. Moreover, Sema4D participated in the hypoxia-induced metastasis of osteosarcoma cells and its expression level was upregulated by transactivation of HIF-1α in vitro. Conclusions Our results demonstrated that Sema4D knockdown had anti-osteosarcoma values and HIF-1α/Sema4D axis regulated the osteosarcoma metastatic cascade in hypoxia condition. They highlighted a therapeutic target which potentially offer an opportunity to improve the survival for osteosarcoma patients.