Song Xu, Yi Wu, Renwang Liu, Haiyang Fan, Sen Wei, Gang Chen,Qinghua Zhou, Jun Chen

Department of Lung Cancer Surgery, Tianjin Medical University General Hospital

Objective:Lung cancer is the leading cause of cancer mortality worldwide. About 30–40% of patients with lung cancer developed bone metastasis during the course of their disease, with the median survival time of 7 months approximately. Bone lesion is characterized by the imbalance of osteoblastic and osteoclastic activity induced by the tumorcells. Mesenchymal stem cells (MSCs) are the progenitor cells of osteoblastcells, and therefore it is interesting to investigate whether and how MSCs have biological alterations in the tumor micro environment of lung cancer patients with bone lesion. Method:We tested miR-139-5p and Notch1 expression during MSC osteogenic differentiation, and validated the effect of miR-139-5p in MSC osteogenesis by transfection of miR-139-5pmimic and inhibitor. We also collected blood samples of healthy donors and lung cancer with bone metastasis, and tested serum miR-139-5p expression. Result: We demonstrated that during MSC osteogenic differentiation in vitro, the expression of miR-139-5 pincreased significantly while Notch1 and its downstream factors decreased. By gain and loss of function studies we showed that miR-139-5pcould positively regulate MSC osteogenic differentiation. And luciferase and western blot assays confirmed that miR-139-5p targeted Notch1 expression directly. Moreover, Notch1 knockdown by siRNA could no longer confer miR-139-5p induced MSC osteogenic differentiation. Lung cancer cell A549 and L9981 secreted factors upregulated miR-139-5p expression and mean while down regulated Notch1 expressionin MSC, as well as impaired ALP activity, the early osteogenic marker of MSCs. More importantly, we observed that serum miR-139-5p was significantly lower in lung cancer patients with lytic bone lesion compared to healthy donors. Conclusion:We demonstrate for the first time, that miR-139-5p could regulate osteogenic differentiation of MSC by targeting Notch1 mediated signaling pathway. Lung cancer cells could decrease miR-139-5p expression and inhibit MSC osteogenic potential. Importantly, serum miR-139-5p is significantly lower in lung cancer patients with lytic bone lesion compared to healthy donors. Therefore, miR-139-5p might be a biomarker of bone metastasis in lung cancer patients and treatment with miR-139-5p mimic might be an interesting strategy to restore the impaired MSC osteogenic differentiation and to control bone disease in lung cancer patients with bonelesion.

Key Words: miR-139-5p  Notch1  bone metastasis