Mediation of Enhanced Transcription of the IL-10 Gene in T Cells, Upon Contact with Human Glioma Cells, by Fas Signaling Through a Protein Kinase A-Independent Pathway

Abstract

Elevated expression of IL-10 has been frequently observed in tumor tissues and tumor-infiltrating cells. We show herein that transcription of the IL-10 gene in primary peripheral T cells and T cell lines is up-regulated upon contact with glioma cells without an induction of apoptosis in those T cells. Glioma-associated IL-10 induction was suppressed by interrupting the engagement of Fas and its ligand (Fas-L) with the antagonistic Ab, ZB4, by reducing Fas-L expression of glioma cells using the Fas-L-specific ribozyme, or by preventing cell-to-cell contact in a Transwell culture setting. Cross-linking of Fas with the agonistic Ab, CH-11, triggered apoptosis and enhanced the expression of IL-10 in Jurkat cells at the transcriptional and translational levels. Inhibiting caspase activities by caspase inhibitors, Z-VAD (Z-Val-Ala-Asp(Ome)-fluoromethylketone) and Z-IETD (Z-Ile-Glu(Ome)-Thr(Ome)-Asp(Ome)-fluoromethylketone), abolished this IL-10 induction in Jurkat cells. Intracellular staining detected IL-10 proteins in Fas-cross-linked Jurkat cells and in PHA-activated T cells. However, few IL-10 proteins were detectable in Jurkat cells cocultured with glioma cells, indicating a requirement of other factors for IL-10 production. Direct activation of protein kinase A (PKA) by forskolin elevated the transcription of IL-10 in Jurkat cells. However, KT5720, a selective PKA inhibitor, reduced neither anti-Fas-triggered nor glioma-associated IL-10 expression. Phosphorylation of cAMP response element binding protein and activating transcription factor-1 in Jurkat cells was not affected by coculturing with glioma cells or by anti-Fas treatment, further suggesting a PKA-independent pathway. In summary, our results demonstrate nonlethal cross-talk between tumor and immune cells leading to IL-10 dysregulation in T cells, which might contribute to Fas-L+ tumor-associated immunosuppression.

Prostaglandin D2 Suppresses Human NK Cell Function via Signaling through D Prostanoid Receptor

“…This result is consistent with a PKA-independent pathway of inhibitory signaling through DP, which has previously been reported in DCs (25). In primary human T cells and macrophages, gene expression and phagocytosis can also be regulated by exchange protein activated by cAMP (Epac), a downstream element of the cAMP pathway that is independent of PKA activation (55)(56)(57). A similar mechanism may also be involved in PGD 2 -induced inhibition of NK cell functions, which will require further investigation.…”

EGFRvIII stimulates glioma growth and invasion through PKA-dependent serine phosphorylation of Dock180

“…To further determine whether PKA is the kinase that primarily mediates EGFRvIII stimulation of p-S of Dock180, we treated SNB19/parental, SNB19/EGFRvIII, LN444/parental and LN444/EGFRvIII cells with or without PKA inhibitors H-89 or KT5720. 19,20 Compared with the control, treatments with both PKA inhibitors markedly attenuated EGFRvIII stimulation of p-S of Dock180, p-Erk1/2, p-Akt, Rac1 activity and cell migration as well as cell proliferation (Fig. 2B to 2E, respectively).…”

Phosphatidylinositol 3-Kinase/Akt Activation by Integrin-Tumor Matrix Interaction Suppresses Fas-Mediated Apoptosis in T Cells

“…For example, tumor-infiltrating lymphocytes (TILs) 3 are able to express vascular endothelial growth factor, which enhances angiogenesis in tumor regions (2,3). Recently, we have demonstrated that coculture with glioma cells will induce transcription of the IL-10 gene in T cells through Fas signaling (4). These findings support the hypothesis that tumors may highjack accumulated TILs to create a tumor growth-promoting environment; this event occurs by the evasion of immune surveillance using elevated local IL-10 production and increased angiogenesis by vascular endothelial growth factor to bring in nutrition.…”

“…Glioma U118(R) expressing a low level of FasL was established from U-118MG by transfection of a plasmid coding a FasL-specific ribozyme (17). U118(V), which served as the nonribozyme control, carries the EGFP-N1 vector (4). Overexpression of Fas (oFas) in MCF-7 cells was achieved by transfection of the oFas plasmid-encoding Fas gene under the control of CMV promoter.…”