Glycogen synthase kinase 3β promotes osteosarcoma invasion and migration via regulating PTEN and phosphorylation of focal adhesion kinase

Aim: Typical features of human osteosarcoma are highly invasive and migratory capacities. Our study aimed to investigate the roles of glycogen synthase kinase 3 beta (GSK3 beta) in human osteosarcoma metastasis. Methods: GSK3 beta expressions in clinical osteosarcoma tissues with or without metastasis were examined by immunohistochemical staining. The expressions of GSK3 beta, p-GSK3 beta(Ser9), and p-GSK3 beta(Tyr216) in human osteoblast cells (hFOB1.19) and human osteosarcoma cells (MG63, SaOS-2, and U2-OS) were detected by Western blotting. The GSK3 beta activity was measured by non-radio isotopic in vitro kinase assay. Migration and invasion abilities of MG-63 cells treated with small-molecular GSK3 beta inhibitors were respectively examined by monolayer-based wound-healing assay and transwell assay. The mRNA expressions of GSK3 beta, matrix metalloproteinase-2 (MMP-2), MMP-9, phosphatase with tensin homology (PTEN), and focal adhesion kinase (FAK) were detected after siRNA transfection for 72 h. Meanwhile, protein expressions of GSK3 beta, FAK, p-FAK(Y397), PTEN, MMP-2, and MMP-9 were measured by Western blotting. Results: Clinical osteosarcoma tissues with metastasis showed higher GSK3 beta expres-sions. MG63 and U2-OS cells that were easy to occur metastasis showed significantly higher expressions and activities of GSK3 beta than SaOS-2 cells. Inhibition of GSK3 beta with small-molecular GSK3 beta inhibitors in MG63 cells significantly attenuated cell migration and invasion. These effects were associated with reduced expressions of MMP-2 and MMP-9. Moreover, increased PTEN and decreased p-FAK(Y397) expressions were observed following GSK3 beta knockdown by siRNA transfection. Conclusion: GSK3 beta might promote osteosar-coma invasion and migration via pathways associated with PTEN and phosphorylation of FAK.