title: IL-6, but not IFN-gamma, triggers apoptosis and inhibits in vivo growth of human malignant T cells on STAT3 silencing.
abstract: STAT1 and STAT3 are the main mediators of the signaling of interferons (IFNs) and of gp130 cytokines, respectively. Neoplastic T lymphocytes frequently become resistant to the IFN-gamma/STAT1 apoptotic pathway, often because of the downregulation of the IFN-gammaR2 receptor chain. Many studies suggest that cross-regulation between different STATs, in particular between STAT1 and STAT3, may profoundly affect cytokine/growth factor signaling. Here, the function of STAT3 in the negative regulation of STAT1 apoptotic pathway was investigated by RNA interference-mediated STAT3 silencing in human malignant T lymphocytes. In STAT3-depleted cells, interleukin (IL)-6 acquired the capacity to induce apoptosis, correlating with prolonged STAT1 activation and the induction of major histocompatibility complex (MHC) class I expression. In contrast, in the absence of STAT3, IFN-gamma could slightly enhance apoptosis but its ability to induce MHC class I expression was unchanged. Accordingly, IL-6, but not IFN-gamma, could significantly impair the in vivo growth of STAT3-depleted human neoplastic T lymphocytes transplanted into severe combined immunodeficient mice. Therefore, treatment with IL-6 and simultaneous STAT3 silencing may represent a potential therapeutic approach to control the expansion of IFN-gamma-unresponsive neoplastic T cells.
authors.affiliation: The Center for Experimental Research and Medical Studies (CERMS), San Giovanni Battista Hospital-Molinette, Turin, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Regis
authors.forename: L
authors.initials: L
authors.lastname: Icardi
authors.forename: L
authors.initials: L
authors.lastname: Conti
authors.forename: R
authors.initials: R
authors.lastname: Chiarle
authors.forename: R
authors.initials: R
authors.lastname: Piva
authors.forename: M
authors.initials: M
authors.lastname: Giovarelli
authors.forename: V
authors.initials: V
authors.lastname: Poli
authors.forename: F
authors.initials: F
authors.lastname: Novelli
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D005260:Female; D005805:Genes, MHC Class I / Q000502:physiology; D006801:Humans; D007371:Interferon-gamma / Q000378:metabolism* / Q000494:pharmacology; D015850:Interleukin-6 / Q000378:metabolism* / Q000494:pharmacology; D016399:Lymphoma, T-Cell / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D016513:Mice, SCID; D009368:Neoplasm Transplantation; D054218:Precursor T-Cell Lymphoblastic Leukemia-Lymphoma / Q000378:metabolism* / Q000473:pathology; D034741:RNA, Small Interfering; D050794:STAT1 Transcription Factor / Q000378:metabolism; D050796:STAT3 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D013601:T-Lymphocytes / Q000166:cytology / Q000378:metabolism*
chemical_list: C508600:IL6 protein, human; D015850:Interleukin-6; D034741:RNA, Small Interfering; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D007371:Interferon-gamma