IFN-γ Upregulates Survivin and Ifi202 Expression to Induce Survival and Proliferation of Tumor-Specific T Cells

Abstract

BackgroundA common procedure in human cytotoxic T lymphocyte (CTL) adoptive transfer immunotherapy is to expand tumor-specific CTLs ex vivo using CD3 mAb prior to transfer. One of the major obstacles of CTL adoptive immunotherapy is a lack of CTL persistence in the tumor-bearing host after transfer. The aim of this study is to elucidate the molecular mechanisms underlying the effects of stimulation conditions on proliferation and survival of tumor-specific CTLs.Methodology/Principal FindingsTumor-specific CTLs were stimulated with either CD3 mAb or cognate Ag and analyzed for their proliferation and survival ex vivo and persistence in tumor-bearing mice. Although both Ag and CD3 mAb effectively induced the cytotoxic effecter molecules of the CTLs, we observed that Ag stimulation is essential for sustained CTL proliferation and survival. Further analysis revealed that Ag stimulation leads to greater proliferation rates and less apoptosis than CD3 mAb stimulation. Re-stimulation of the CD3 mAb-stimulated CTLs with Ag resulted in restored CTL proliferative potential, suggesting that CD3 mAb-induced loss of proliferative potential is reversible. Using DNA microarray technology, we identified that survivin and ifi202, two genes with known functions in T cell apoptosis and proliferation, are differentially induced between Ag- and CD3 mAb-stimulated CTLs. Analysis of the IFN-γ signaling pathway activation revealed that Ag stimulation resulted in rapid phosphorylation of STAT1 (pSTAT1), whereas CD3 mAb stimulation failed to activate STAT1. Chromatin immunoprecipitation revealed that pSTAT1 is associated with the promoters of both survivin and ifi202 in T cells and electrophoresis mobility shift assay indicated that pSTAT1 directly binds to the gamma activation sequence element in the survivin and ifi202 promoters. Finally, silencing ifi202 expression significantly decreased T cell proliferation.Conclusions/SignificanceOur findings delineate a new role of the IFN-γ signaling pathway in regulating T cell proliferation and apoptosis through upregulating survivin and ifi202 expression.

Insulin Micro-secretionin Patients with Long Duration Type 1 Diabetes: Implications of Interferon-γ?

“…It is a critical intracellular machinery of cytokines involved in gene expression and cellular activation, proliferation and differentiation [12,13]. IFN-γ has been found to activate the expression of target genes through binding of activated STAT1 proteins on a consensus element termed the IFN-γ-activated site (GAS) [15,16]. It has been shown that upon stimulation of IFN-γ, JAKs are activated and phosphorylate STAT1that shapes a homodimer and moves into the nucleus binding to GASs within promoters of target gene [5,15,16].…”

“…IFN-γ has been found to activate the expression of target genes through binding of activated STAT1 proteins on a consensus element termed the IFN-γ-activated site (GAS) [15,16]. It has been shown that upon stimulation of IFN-γ, JAKs are activated and phosphorylate STAT1that shapes a homodimer and moves into the nucleus binding to GASs within promoters of target gene [5,15,16]. Intriguingly, it has been reported that IFN-γ is a transcriptional inducer of survivin gene in an autocrine manner through STAT1 pathway [16].…”

“…It has been shown that upon stimulation of IFN-γ, JAKs are activated and phosphorylate STAT1that shapes a homodimer and moves into the nucleus binding to GASs within promoters of target gene [5,15,16]. Intriguingly, it has been reported that IFN-γ is a transcriptional inducer of survivin gene in an autocrine manner through STAT1 pathway [16]. It has been detected that IFN-γ-activated STAT1 binds directly to a GAS element in the survivin promoter region to trigger survivin expression [16].…”

“…Intriguingly, it has been reported that IFN-γ is a transcriptional inducer of survivin gene in an autocrine manner through STAT1 pathway [16]. It has been detected that IFN-γ-activated STAT1 binds directly to a GAS element in the survivin promoter region to trigger survivin expression [16]. Survivin is the smallest member of the inhibitor of apoptosis protein gene family [15][16][17][18].…”

“…It has been detected that IFN-γ-activated STAT1 binds directly to a GAS element in the survivin promoter region to trigger survivin expression [16]. Survivin is the smallest member of the inhibitor of apoptosis protein gene family [15][16][17][18]. It is an established cancer gene that is over-expressed in almost all human tumors and during embryonic and fetal development, whereas it is hardly detectable or minimally expressed in normal mature tissues [15,17,18].…”