Therapeutic Senolysis of Axitinib-Induced Senescent Human Lung Cancer Cells

Simple Summary Tyrosine kinase inhibitors (TKIs) inhibit receptor-mediated signals in cancer and vascular endothelial cells. Especially, axitinib inhibits signaling via vascular endothelial growth factor receptors (VEGFRs). In this study, we report an unforeknown effect of axitinib on human lung cancer cells. We show that axitinib increased the cell size and enhanced the expression of beta-galactosidase in a panel of human cancer cell lines, irrespective of their expression of VEGFRs. Especially, axitinib-treated human lung adenocarcinoma A549 cells showed typical senescence and subsequent treatment with the senolytic drug ABT-263 induced drastic cell death (senolysis). Senolysis of senescent A549 cells by ABT-263 was attributed to caspase-dependent apoptosis and Bcl-xL inhibition. Reactive oxygen species were involved in axitinib-induced senescence, but not in senolysis, of A549 cells. In an A549-xenografted mouse model, combination therapy with axitinib and ABT-263 significantly suppressed tumor growth.Abstract Background: Tyrosine kinase inhibitors (TKIs) inhibit receptor-mediated signals in cells. Axitinib is a TKI with high specificity for vascular endothelial growth factor receptors (VEGFRs). Aim: We determined whether axitinib could induce senescence in human cancer cells and be lysed by the senolytic drug ABT-263. Methods: Human lung and breast adenocarcinoma cell lines were used. These cells were cultured with axitinib or a multi-target TKI lenvatinib. The expression of beta-galactosidase, VEGFRs, Ki-67, reactive oxygen species (ROS) of cancer cells, and their BrdU uptake were evaluated by flow cytometry. The mRNA expression of p21 and IL-8 was examined by quantitative PCR. The effects of TKIs on phosphorylation of Akt and Erk1/2, as downstream molecules of VEGFR signaling, were examined by immunoblot. The in vivo anti-cancer effect was examined using a xenograft mice model. Results: Axitinib, but not lenvatinib, induced cellular senescence (increased cell size and enhanced expression of beta-galactosidase) in all adenocarcinoma cell lines. Axitinib-induced senescence was unrelated to the expression of VEGFRs on cancer cells. ROS were involved in axitinib-induced senescence. Axitinib-induced senescent lung adenocarcinoma A549 cells were drastically lysed by ABT-263. In A549-xenografted mice, combination therapy with axitinib and ABT-263 significantly suppressed tumor growth with the induction of apoptotic cancer cells.