Histone deacetylase inhibitors suppress mutant p53 transcription via HDAC8/YY1 signals in triple negative breast cancer cells.

There is an urgent need to investigate the potential targeted therapy approach for triple-negative breast cancer (TNBC). Our present study reveals that histone deacetylase inhibitors (HDACIs) suberoyl anilide hydroxamic acid (SAHA) and sodium butyrate (NaB) significantly inhibit cell proliferation, arrest cell cycle at G0/G1 phase, and induce mitochondrial related apoptosis of TNBC cells. Further, SAHA and NaB decrease the phosphorylation, protein and mRNA levels of mutant p53 (mtp53) in TNBC cells. While SAHA or NaB has no similar inhibition effect on wild type p53 (wtp53). The inhibition apparently occurs at the level of transcription because the down regulation of precursor p53 transcription is much more rapid (less than 2h) and sharp than that of mature p53. The knockdown of HDAC8, while not HDAC6, inhibits the transcription of mtp53 in TNBC cells. The luciferase assay and ChIP analysis reveal that both SAHA and NaB can reduce the binding of transcription factor Yin Yang 1 (YY1) with the -102 to -96 position of human p53 promoter. Knockdown of YY1 also significantly inhibits the transcription of mtp53 in TNBC cells. Further, SAHA and NaB can inhibit the association of HDAC8 and YY1, increase acetylation of residues 170-200 of YY1, then decrease its transcription activities, and finally suppress YY1 induced p53 transcription. Together, our data establish that SAHA and NaB can be considered as drug candidates for TNBC patients, and HDAC8/YY1/mtp53 signals act as an important target for TNBC treatment.

A new tumor vaccine: FAPτ-MT elicits effective antitumor response by targeting indolamine2,3-dioxygenase in antigen presenting cells.

Indolamine2, 3-dioxygenase (IDO) is expressed in tumor antigen presenting cells (APCs) and plays an important role in tumor immune tolerance. Inhibiting its activity may break tumor immune tolerance and thus promote therapeutic effects. Thus, a specific inhibitor of IDO, 1-methyl-tryptophan (1-MT), is being used more and more frequently in anti-tumor studies. However, IDO also maintains systemic immune balance by suppressing abnormal immune responses. Therefore, targeting IDO in tumor-associated APCs in a way that does not disrupt immune balance warrants further investigation. In this study, we developed a new tumor vaccine, FAPτ-MT, which was produced by conjugating 1-MT to a tumor associated antigen, fibroblast activation protein α (FAPα). The results in vitro confirmed that 1-MT could be dissociated from the FAPτ-MT vaccine and inhibit intracellular IDO activity. In an FAPα-positive tumor model, the FAPτ-MT vaccine elicited an anti-tumor response which was similar to systemic treatment with the FAPτ vaccine plus 1-MT. Most importantly, administration of the FAPτ-MT vaccine did not lead to pregnancy failiure in mice carrying allogeneic fetuses. These findings that FAPτ-MT breaks tumor immune tolerance as a local IDO inhibitor, suggest that conjugation of 1-MT to a tumor antigen peptide is a potentially effective clinical cancer immunotherapy.

Sodium butyrate down-regulation of indoleamine 2, 3-dioxygenase at the transcriptional and post-transcriptional levels.

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.

Expression of indoleamine 2,3-dioxygenase in nasopharyngeal carcinoma impairs the cytolytic function of peripheral blood lymphocytes.

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-gamma (IFNgamma) 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-gamma (IFNgamma) 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.

[Curcumin inhibiting the expression of indoleamine 2,3-dioxygenase induced by IFN-gamma in cancer cells].

OBJECTIVE: To investigate the effect of curcumin on indoleamine 2, 3 -dioxygenase (IDO) expression induced by IFN-gamma in cancer cells. METHODS: 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. RESULTS: Curcumin inhibited the expression of IDO in these cancer cells. However, curcumin did not inhibit the transcription of IRF-1 in cancer cells. CONCLUSION: Curcumin could inhibit the expression of IDO in cancer cells.

[Studies on the effect of Ginkgo biloba extracts on NF-kappaB pathway].

OBJECTIVE: 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. METHODS: 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. RESULTS: 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. CONCLUSION: GhE can suppress the NF-kappaB gene expression actively on independent of NIK/ IKK/ IkappaBalpha pathway in HL-60 cells.