Effect of CXCR4 on Apoptosis in Osteosarcoma Cells via the PI3K/Akt/NF-κβ Signaling Pathway

Abstract

Background/aims: Osteosarcoma, the most common primary bone malignancy, arises from primitive transformed cells of mesenchymal origin with the worldwide increasing morbidity and mortality. Previous studies found apoptosis of osteosarcoma cells was essential for an effective manner to improve the progress of osteosarcoma, and CXCR4 has been demonstrated to be relevant with various tumor progress and metastasis.

Methods: The proliferation of cells transfected with CXCR4 shRNA and control shRNA were measured by BrdU assay. Apoptosis was detected by flow cytometry. Apoptotic protein expression levels were detected by Western blot. Caspase activity was detected by Colorimetric Assay Kits using microplate reader. Activation of NF-κβ signaling after CXCR4 down-regulation in osteosarcoma cells was examined by constructing NF-κβ promoter luciferase reporter plasmid. The expression and activation of NF-κβ Signaling relevant protein were analyzed to investigate the relationship between Akt and NF-κβ signaling after the down-regulation of CXCR4 in osteosarcoma cells.

Results: Down-regulation of CXCR4 significantly reduced the cell proliferation, while remarkably increased the cell apoptosis and apoptotic protein expression levels in osteosarcoma cells. Furthermore, down-regulation of CXCR4 induced cell apoptosis was caspase dependent in osteosarcoma cells. This study also showed CXCR4 down-regulation induced apoptosis through inhibiting PI3K/Akt/NF-κβ signaling pathway. In addition, endoplasmic reticulum stress (ERS) activation was involved in cell apoptosis induced down-regulation of CXCR4. Knockdown of partial ERS relevant proteins followed down-regulation of CXCR4 significantly inhibited cell apoptosis and the apoptotic protein expression levels.

Conclusions: Taken together, the results demonstrated that down-regulation of CXCR4 could induce apoptosis of human osteosarcoma cells through inhibiting PI3K/Akt/NF-κβ signaling pathway, indicating that CXCR4 could be vital for the clinical therapy of osteosarcoma.

Keywords: Apoptosis; CXCR4; ERS; Osteosarcoma; PI3K/Akt/NF-κβ signaling.