STAT3 and the Immune System Maureen Sherry Lynes February 29, 2012
Overview • STAT family; STAT3 signaling and structure • Role of STAT3 revealed by tissue specific knockouts • STAT3 and the anti-tumor immune response • Therapeutic approaches for targeting STAT3 • Paper discussion
The STAT Family of Transcription Factors • 7 mammalian STAT proteins • latent cytoplasmic transcription factors • Important in a wide range of physiological processes Adapted from Darnell and Levy, 2002
How is the STAT3 pathway activated? • Cytokines, growth factors • Secreted by diverse cell types in response to diverse processes • Receptor specific Minegishi et al 2011
The STAT3 Signaling Pathway Negative Regulation of STAT3 signaling Cytoplasmic phosphatases SOCs proteins Pias Proteins STAT3ß
STAT3 Target Genes Growth (C-myc, cyclin D) Apoptosis (Survivin, bcl-xl) STAT3 Differentiation Angiogenesis (VEGF) Immortalization (hTERT)
Tissue Specific STAT3 Knockouts • Brain: obesity, inability to control temperature, diabetes • Skin: impaired wound healing, resistance to skin cancer • Mouse Embryonic Stem Cells: loss of pluripotency • Lung • Macrophages and Neutrophils • Liver • Th17 development Gao et al, 2004.
STAT3 and the Acute Phase Response • Liver: site of integration of signals from tissue, toxins and bacterial products in blood, etc • Macrophages in the periphery: cytokine release • Hepatocytes respond to cytokines (IL-6, IL-1 for example) and upregulate appropriate response proteins (clotting, innate responses to bacterial infection, toxins, etc) • Hepatocyte deletion of STAT3- polymicrobial sepsis LPS injection or cecal ligation and puncture: Similar bacterial load; decreased acute phase proteins, increased inflammatory cytokines such as IL-6 and TNFa Sakamori et al 2007
STAT3 in macrophages and neutrophils • STAT3 deleted in cells expressing lysozyme M • Mice were susceptible to LPS-induced endotoxic shock • Macrophages constitutively activated Takeda et al, 1999.
STAT3 in macrophages and neutrophils • STAT3 -/- macrophages are resistant to IL-10 • IL-10 normally dampens macrophage activation and response • LysmCre STAT3 mice develop chronic enterocholitis
STAT3 in the lung epithelium • House dustmite extract: induces allergic inflammation in the lung, as well as STAT3 activation • Lung specific STAT3 KO: appears normal • STAT3 lung KO: decreased airway hyperresponsiveness, immune infiltration upon HDM challenge Simeone et al, 2007.
STAT3 in Th17 Differentiation • CD4+, defense against extracellular bacteria, fungi • Pathogenic autoimmune responses • Celiac, IBD, etc Fischer 2008
DNA binding STAT3 in hyper IgE syndrome activation
STAT3 in hyper IgE syndrome Recurrent skin and lung infections (Th17, lung epithelial defects?)
Activation, Duration, and extent of STAT3 signaling is tightly regulated • Brain: obsesity, inability to control temperature, diabetes • Skin: impaired wound healing, resistance to skin cancer • Mouse Embryonic Stem Cells: loss of pluripotency • Lung- promotes allergic inflammation • Macrophages and Neutrophils- prevents constitutve activation, • Liver: actue phase response; integration of signals from tissues • Th17 differentiation Gao et al, 2004.
STAT3 and tumorigenesis • STAT3 is constitutively activated in many human cancers • Inappropriately activated or overexpressed • Prevents apoptosis, stimulates migration, stimulates proliferation, increases angiogenesis • Upregulates cytokines that perpetuate STAT3 activation in the tumor and surrounding tissue Wang, Rich et al. Stem Cells 2009
DN STAT3 induces melanoma regression in a mouse model • Transfection of B16 tumors with dominant negative STAT3 induces tumor regression • Bystander effect: regression disproportionate to transfection Niu et al Cancer Research 1999
STAT3 Suppresses Anti-Tumor Immunity • Cultured B16 cells transfected with DN STAT3: increased production of pro-inflammatory cytokines and chemokines (TNFa, RANTES, IP-10) • In vivo: enhances macrophage and neutrophil infiltration Wang et al Nature Med 2004
STAT3 Suppresses Anti-Tumor Immunity Yu et al Nature Reviews 2007
STAT3 as a therapeutic target • Activation • EGFR antibodies; small molecules • Jak inhibitors • Multi-receptor kinase inhibitors • Protein-protein interactions • Small molecules to prevent dimerization • phosphoTyr peptides • DNA binding • Double stranded oligonucleotides • Nuclear translocation, natural inhibitors
Summary • STAT3 is a cytokine and growth factor activated transcription factor • STAT3 has a wide range of functions, both anti and pro inflammatory depending on the tissue and physiological context • STAT3 is also involved in disease states, such as asthma, colitis, and cancer • STAT3 can suppress anti-tumor immunity • STAT3 directed therapeutics is an active area of research