GSK-3β regulates the endothelial-to-mesenchymal transition via reciprocal crosstalk between NSCLC cells and HUVECs in multicellular tumor spheroid models

BACKGROUND: Chemotherapy used for patients with unresectable lung tumors remains largely palliative due to chemoresistance, which may be due to tumor heterogeneity. Recently, multiple studies on the crosstalk between lung cancer cells and their tumor microenvironment (TME) have been conducted to understand and overcome chemoresistance in lung cancer. METHODS: In this study, we investigated the effect of reciprocal crosstalk between lung cancer cells and vascular endothelial cells using multicellular tumor spheroids (MCTSs) containing lung cancer cells and HUVECs. RESULTS: Secretomes from lung cancer spheroids significantly triggered the endothelial-to-mesenchymal transition (EndMT) process in HUVECs, compared to secretomes from monolayer-cultured lung cancer cells. Interestingly, expression of GSK-3β-targeted genes was altered in MCTSs and inhibition of this activity by a GSK-3β inhibitor induced reversion of EndMT in lung tumor microenvironments. Furthermore, we observed that HUVECs in MCTSs significantly increased the compactness of the spheroids and exhibited strong resistance against Gefitinib and Cisplatin, relative to fibroblasts, by facilitating the EndMT process in HUVECs. Subsequently, EndMT reversion contributed to control of chemoresistance, regardless of the levels of soluble transforming growth factor (TGF)-β. Using the MCTS xenograft mouse model, we demonstrated that inhibition of GSK-3β reduces lung cancer volume, and in combination with Gefitinib, has a synergistic effect on lung cancer therapy. CONCLUSION: In summary, these findings suggest that targeting EndMT through GSK-3β inhibition in HUVECs might represent a promising therapeutic strategy for lung cancer therapy. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s13046-019-1050-1) contains supplementary material, which is available to authorized users.