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Modulation of cell signaling networks after CTLA4 blockade in patients with metastatic melanoma.

ABSTRACT: The effects on cell signalling networks upon blockade of cytotoxic T lymphocyte-associated antigen-4 (CTLA4) using the monoclonal antibody tremelimumab were studied in peripheral blood mononuclear cell (PBMC) samples from patients with metastatic melanoma.Findings Intracellular flow cytometry was used to detect phosphorylated (p) signaling molecules downstream of the T cell receptor (TCR) and cytokine receptors. PBMC from tremelimumab-treated patients were characterized by increase in pp38, pSTAT1 and pSTAT3, and decrease in pLck, pERK1/2 and pSTAT5 levels. These changes were noted in CD4 and CD8 T lymphocytes but also in CD14 monocytes. A divergent pattern of phosphorylation of Zap70, LAT, Akt and STAT6 was noted in patients with or without an objective tumor response.The administration of the CTLA4-blocking antibody tremelimumab to patients with metastatic melanoma influences signaling networks downstream of the TCR and cytokine receptors both in T cells and monocytes. The strong modulation of signaling networks in monocytes suggests that this cell subset may be involved in clinical responses to CTLA4 blockade.clinicaltrials.gov; Registration numbers NCT00090896 and NCT00471887.

SUBMITTER: Comin-Anduix B

PROVIDER: S-EPMC2939876 | biostudies-literature | 2010 Sep

REPOSITORIES: biostudies-literature

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Modulation of cell signaling networks after CTLA4 blockade in patients with metastatic melanoma.

Comin-Anduix Begoña B Sazegar Hooman H Chodon Thinle T Matsunaga Douglas D Jalil Jason J von Euw Erika E Escuin-Ordinas Helena H Balderas Robert R Chmielowski Bartosz B Gomez-Navarro Jesus J Koya Richard C RC Ribas Antoni A

PloS one 20100915 9

<h4>Background</h4>The effects on cell signalling networks upon blockade of cytotoxic T lymphocyte-associated antigen-4 (CTLA4) using the monoclonal antibody tremelimumab were studied in peripheral blood mononuclear cell (PBMC) samples from patients with metastatic melanoma.<h4>Methodology/principal</h4>Findings Intracellular flow cytometry was used to detect phosphorylated (p) signaling molecules downstream of the T cell receptor (TCR) and cytokine receptors. PBMC from tremelimumab-treated pati ...[more]

PMID: 20856802

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Project description:BackgroundWe previously reported early on-treatment significant modulation in circulating regulatory T cell (Treg), myeloid derived suppressor cells (MDSC) and antigen-specific type I CD4+ and CD8+ T cells that correlated with clinical outcome in regionally advanced melanoma patients treated with neoadjuvant ipilimumab. Here, we investigated the long term immunologic impact of CTLA4 blockade.MethodsPatients were treated with ipilimumab given at 10 mg/kg IV every 3 weeks for 2 doses bracketing surgery. Blood specimens were collected at baseline and during treatment for up to 9 months. We tested immune responses at 3, 6, and 9 months utilizing multicolor flow cytometry. We compared frequencies of circulating Treg and MDSC on-study to baseline levels, as well as frequencies of CD4+ and CD8+ T cells specific to shared tumor-associated antigens (Gp-100, MART-1, NY-ESO-1).ResultsLevels of Treg significantly increased when measured at 6 weeks following ipilimumab but returned to baseline by 3 months, with no significant difference in Treg levels between relapsed and relapse-free groups at 3, 6 or 9 months. However, lower baseline levels of circulating Treg (CD4+CD25hi+CD39+) were significantly associated with better relapse free survival (RFS) (p = 0.04). Levels of circulating monocytic HLA-DR+/loCD14+ MDSC were lower at baseline in the relapse-free group and further decreased at 6 weeks, though the differences did not reach statistical significance including measurements at 3, 6 or 9 months. We detected evidence of type I (interferon-γ producing), activated (CD69+) CD4+ and CD8+ antigen-specific T cell immunity against cancer-testis (NY-ESO-1) as well as melanocytic lineage (MART-1, gp100) antigens in the absence of therapeutic vaccination. These responses were significantly boosted at 6 weeks and persisted at 3, 6 and 9 months following the initiation of ipilimumab.ConclusionsLower Treg levels at baseline are significantly associated with RFS and increased Treg frequency after CTLA4 blockade was only transient. Lower MDSC was also associated with RFS and MDSC levels were further decreased after ipilimumab. Tumor specific effector immune responses are boosted with CTLA4 blockade and tend to be durable. Trial registration ClinicalTrials.gov Identifier: NCT00972933.

Project description:Cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) is an immune checkpoint expressed in regulatory T (Treg) cells and activated T lymphocytes. Despite its potential as a treatment strategy for melanoma, CTLA-4 inhibition has limited efficacy. Using data from The Cancer Genome Atlas (TCGA) melanoma database and another dataset, we found that decreased CTLA4 mRNA was associated with a poorer prognosis in metastatic melanoma. To investigate further, we measured blood CTLA4 mRNA in 273 whole-blood samples from an Australian cohort and found that it was lower in metastatic melanoma than in healthy controls and associated with worse patient survival. We confirmed these findings using Cox proportional hazards model analysis and another cohort from the US. Fractionated blood analysis revealed that Treg cells were responsible for the downregulated CTLA4 in metastatic melanoma patients, which was confirmed by further analysis of published data showing downregulated CTLA-4 surface protein expression in Treg cells of metastatic melanoma compared to healthy donors. Mechanistically, we found that secretomes from human metastatic melanoma cells downregulate CTLA4 mRNA at the post-transcriptional level through miR-155 while upregulating FOXP3 expression in human Treg cells. Functionally, we demonstrated that CTLA4 expression inhibits the proliferation and suppressive function of human Treg cells. Finally, miR-155 was found to be upregulated in Treg cells from metastatic melanoma patients compared to healthy donors. Our study provides new insights into the underlying mechanisms of reduced CTLA4 expression observed in melanoma patients, demonstrating that post-transcriptional silencing of CTLA4 by miRNA-155 in Treg cells may play a critical role. Since CTLA-4 expression is downregulated in non-responder melanoma patients to anti-PD-1 immunotherapy, targeting miRNA-155 or other factors involved in regulating CTLA4 expression in Treg cells without affecting T cells could be a potential strategy to improve the efficacy of immunotherapy in melanoma. Further research is needed to understand the molecular mechanisms regulating CTLA4 expression in Treg cells and identify potential therapeutic targets for enhancing immune-based therapies.

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Modulation of cell signaling networks after CTLA4 blockade in patients with metastatic melanoma.

Publications

Modulation of cell signaling networks after CTLA4 blockade in patients with metastatic melanoma.

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