ABSTRACT
The epithelial-to-mesenchymal transition (EMT) is involved in cancer metastasis; nevertheless, interferon (IFN)-γ induces anticancer activities by causing cell growth suppression, cytotoxicity, and migration inhibition. Regarding the poor response to exogenously administered IFN-γ as anticancer therapy, it was hypothesized that malignant cells may acquire a means of escaping from IFN-γ immunosurveillance, likely through an EMT-related process. A genomic analysis of human lung cancers revealed a negative link between the EMT and IFN-γ signaling, while compared to human lung adenocarcinoma A549 cells, IFN-γ-hyporesponsive AS2 cells exhibited mesenchymal characteristics. Chemically, physically, and genetically engineered EMT attenuated IFN-γ-induced IFN regulatory factor 1 transactivation. Poststimulation of transforming growth factor-ß induced the EMT and also selectively retarded IFN-γ-responsive gene expression as well as IFN-γ-induced signal transducer and activator of transcription 1 activation, major histocompatibility complex I, and CD54 expression, cell migration/invasion inhibition, and direct/indirect cytotoxicity. Without changes in IFN-γ receptors, excessive oxidative activation of Src homology-2 containing phosphatase 2 (SHP2) in cells undergoing the EMT primarily caused cellular hyporesponsiveness to IFN-γ signaling and cytotoxicity, while combining an SHP2 inhibitor or antioxidant sensitized EMT-associated AS2 and mesenchymal A549 cells to IFN-γ-induced priming effects on tumor necrosis factor-related apoptosis-inducing ligand cytotoxicity. In cell line-derived xenograft models, combined treatment with IFN-γ and an SHP2 inhibitor induced enhanced anticancer activities. These results imply that EMT-associated SHP2 activation inhibits IFN-γ signaling, facilitating lung cancer cell escape from IFN-γ immunosurveillance.
