Deletion of osteopontin in non-small cell lung cancer cells affects bone metabolism by regulating miR-34c/Notch1 axis: a clue to bone metastasis

Lung cancer is prone to bone metastasis, and osteopontin (OPN) has an important significance in maintaining bone homeostasis. The goal of this study was to explore the impact of OPN level on bone metabolism and the molecular mechanism of inhibiting bone metastasis in non-small cell lung cancer (NSCLC). The expression of OPN in NSCLC was ascertained by Western blot and immunohistochemistry, and the correlation between the expression level of OPN and survival of patients was analyzed. Then the shRNA technology was applied to reduce the expression of OPN in NSCLC cells, and CCK-8 assay was carried out to investigate the effect of low expression of OPN on the proliferation of NSCLC cells. In addition, the effects of low expression of OPN on osteoclast differentiation, osteoblast generation and mineralization were studied using osteoclast precursor RAW264.7 and human osteoblast SaOS-2 cells, and whether OPN could regulate miR-34c/ Notch pathway to affect bone metabolism was further explored. The findings showed that the high level of OPN in NSCLC was closely related to the poor prognosis of patients and the abnormal proliferation of NSCLC cell lines. The suppression of OPN was beneficial to inhibit the differentiation of osteoclasts and promote the mineralization of osteoblasts. Besides, this study confirmed that the deletion of OPN can regulate bone metabolism through the regulation of miR-34c/Notch1 pathway, which will contribute to inhibiting the occurrence of osteolytic bone metastasis in NSCLC.