Search

The clinical outcomes of most immunotherapeutic strategies have been less effective than anticipated partially because of the tumor immune tolerance induced by many immune tolerance factors, which originate from the tumor and tumor microenvironment. Indoleamine 2, 3-dioxygenase (IDO) is an interferon-γ (IFN-γ)-inducible enzyme and is one of main immune tolerance factors during tumor development. Sodium butyrate (NaB) has received much attention as a potential chemopreventive agent for cancer treatment due to its protective action against intracellular events including IFN-γ-mediated signaling transduction. Therefore, the question remains whether IDO is a target of the anti-tumor action of NaB. In this study, we demonstrate for the first time that NaB down-regulated IDO via both transcriptional and post-transcriptional mechanisms. NaB repressed the activity of STAT1 to inhibit STAT1-driven transcriptional activity of IDO. These mechanisms included inhibiting STAT1 701 tyrosine phosphorylation, nuclear translocation, and repression of STAT1 binding to γ-activated sites (GAS). Moreover, immunoprecipitation and immunoblotting assays showed that treatment of cells with NaB caused dramatic ubiquitination of total intracellular proteins, including IDO. Blocking 26S proteasome activity by addition of its specific inhibitor, bortezomib, reversed the ubiquitination and down-regulation of IDO. These results suggest that NaB-induced STAT1 activity inhibition and ubiquitin/proteasome-dependent proteolysis are involved in the down-regulation of IDO. The discoveries in this study represent a new mechanism in the anti-tumor action of NaB and may have implications for development of clinical cancer immunotherapy.

Background Tumor-specific cytotoxic T cells and infiltrating lymphocytes are frequently found in tumor tissues in patients with nasopharyngeal carcinoma (NPC). Most patients with NPC, however, especially those with advanced stages, have a poor clinical prognosis despite conventional immunotherapy. The aim of this work was to examine the effect of indoleamine 2,3-dioxygenase (IDO), an immunosuppressive enzyme, on the lymphocyte function in NPC. Methods The NPC cell line CNE2 was treated by interferon-γ (IFNγ) and the levels of IDO expression was analyzed by Western blotting and reverse phase high-performance liquid chromatography (HPLC). Lymphocytes from health human exposed to the milieu created by IDO-positive CNE2 cells and the lymphocyte cytotoxicity to target tumor cells was analyzed by standard lactate dehydrogenase (LDH) release assay. Additionally, expression of IDO was determined by Immunohistochemical assay in the tumor tissues form clinically evaluated NPC. Results IDO expression was acutely induced in the NPC cell line CNE2 by low dose interferon-γ (IFNγ) or by co-incubation with activated lymphocytes. Exposure to the milieu created by IDO-positive CNE2 cells did not promote lymphocyte death, but lymphocyte cytotoxicity against target tumor cells was impaired. The suppression of lymphocyte cytotoxic function was fully restored when the conditioned medium was replaced by fresh medium for 24 h. In additionally, the IDO-positive cells were found scattered in the tumor tissues from patients with NPC. Conclusion Altogether, these findings suggest that IDO-mediated immunosuppression may be involved in the tumor immune evasion, and that blocking IDO activity in tumor cells may help to re-establish an effective anti-tumor T cell response in NPC.

To investigate NF-kappaB and IkappaBalpha activities in HL-60 induced by TNF-alpha in order to understand the molecular mechanism of GbE in asthma treatment.The amount of IkappaBalpha in HL-60 cells stimulated by TNF-alpha and GbE was measured by western blotting. Plasmid pNF-kappaB-LuC was transfected and NF-kappaB activity was analyzed by measuring the expression level of luciferase.It showed in the luciferase assay that the activity of NF-kappaB could significantly be suppressed in HL-60 cells after the pretreatment with CGbE. However, the phosphorylation and subsequent degradation of IKBalpha induced by TNF-alpha can not be inhibited in HL-60 cells even we prolonged the treatment time or increased the concentration of GhE.GhE can suppress the NF-kappaB gene expression actively on independent of NIK/ IKK/ IkappaBalpha pathway in HL-60 cells.

To investigate the effect of curcumin on indoleamine 2, 3 -dioxygenase (IDO) expression induced by IFN-gamma in cancer cells.A431, HeLa, HepG2, CNE2 cells were treated with curcumin for 24 hours, then the cell proliferation was detected by methyl thiazolyl tetrazolium (MTF) assay. The effects of curcumin on IDO expression induced by IFN-gamma in these cancer cells were demonstrated by Western blot. The transcription of interferon responsive factor-1 (IRF-1), which was a key transcription factor regulating IDO expression, was analyzed by reverse transcription polymerase chain reaction (RT-PCR) under the treatment of curcumin.Curcumin inhibited the expression of IDO in these cancer cells. However, curcumin did not inhibit the transcription of IRF-1 in cancer cells.Curcumin could inhibit the expression of IDO in cancer cells.