Sunitinib Induces NK-κB- dependent NKG2D Ligand Expression in Nasopharyngeal Carcinoma and Hepatoma Cells

Multitargeted tyrosine kinase inhibitors (MTKIs) have been shown to combine with natural killer (NK) cell adoptive transfer for the treatment in various cancers. MTKIs sensitize cancer cells to NK cell therapy through upregulation of nature killer group 2 member D ligands (NKG2DLs) on tumor cells. However, the molecular mechanism of MTKIs-mediated upregulation of NKG2DLs is still unknown. In this study, we confirmed sunitinib induced downregulation of its targets, such as vascular endothelial growth factor, platelet-derived growth factor, and c-kit in multiple-drug-resistant nasopharyngeal carcinoma cell line CNE2/DDP and hepatoma cell line HepG2. Then, we further showed sunitinib induced cell proliferation inhibition, apoptosis, and DNA damage in CNE2/DDP and HepG2 cells. Coculture experiments showed that sunitinib-treated CNE2/DDP and HepG2 cells were able to increase the activation and cytotoxicity of NK cells. Quantitative polymerase chain reaction results showed that sunitinib upregulated NKG2DLs, apoptotic genes, DNA damage repair genes, and nuclear factor (NF)-kappa beta family genes. Silencing of NF-kappa b1, NF-kappa beta 2, or RelB (NF-kappa beta pathway) inhibited sunitinib-induced upregulation of NKG2DLs. Taken together, we concluded that sunitinib upregulated NKG2DLs through NF-kb signaling noncanonical pathway which might mediate higher cytotoxic sensitivity of CNE2/DDP and HepG2 cells to NK cells.