Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0025202 (melanoma)
 69,561 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The sensitivity and resistance of six human melanoma cell lines to gamma-interferon (gamma-IFN) and tumour necrosis factor-alpha (TNF-alpha) have been examined. Amelanotic cell lines were more sensitive to gamma-IFN and TNF-alpha than melanotic cells. The cytotoxicity of gamma-IFN and TNF-alpha could be reversed in all cells by the addition of L- or D-tryptophan to the culture medium. Melanoma cells resistant to gamma-IFN excrete calcium activated neutral protease (CANP) and as a consequence, make L-tryptophan available by the hydrolysis of serum proteins in the culture medium. Resistance to gamma-IFN could be reversed by the addition of specific CANP inhibitor, whereas gamma-IFN-sensitive strains became more resistant with the addition of CANP to the culture medium. It has been confirmed that gamma-IFN induces indoleamine 2,3-dioxygenase in melanoma cells. This enzyme utilizes the superoxide anion (O2-) as a substrate for the oxidation of either L- or D-tryptophan to N-formylkynurenic acid leading to cell death. The induction of this degradative pathway for L-tryptophan kills cells by starvation of this essential and relatively scarce amino acid. TNF-alpha induces manganese-containing superoxide dismutase (MnSOD) which also uses O2- to produce cytotoxic concentrations of hydrogen peroxide. Therefore, it can be concluded that the cytotoxicity of both gamma-IFN and TNF-alpha depends on the availability of L-tryptophan as the substrate for the removal of O2- via indoleamine 2,3-dioxygenase.
Melanoma Res
PMID:Tryptophan protects human melanoma cells against gamma-interferon and tumour necrosis factor-alpha: a unifying mechanism of action. 166 25

Production of indoleamine 2,3-dioxygenase (IDO) by tumor cells, leading to tryptophan depletion and production of immunosuppressive metabolites, may facilitate immune tolerance of cancer. IDO gene is also expressed in dendritic cells (DC) upon maturation induced by lipopolysaccarides or IFN. We investigated IDO gene expression in melanoma cell lines and clinical specimens as compared to mature DC (mDC). Furthermore, we explored effects of L-kynurenine (L-kyn) and 3-hydroxyanthranilic acid (3-HAA) on survival and antigen-dependent and independent proliferation of CD8(+) cells. We observed that IDO gene expression in cultured tumor cells and freshly excised samples is orders of magnitude lower than in mDC, providing highly efficient antigen presentation to CD8(+) T cells. Non toxic concentrations of L-kyn or 3-HAA did not significantly inhibit antigen-specific CTL responses. However, 3-HAA, but not L-kyn markedly inhibited antigen-independent proliferation of CD8(+) T cells induced by common receptor gamma-chain cytokines IL-2, -7 and -15. Our data suggest that CD8(+) T cell activation induced by antigenic stimulation, a function exquisitely fulfilled by mDC, is unaffected by tryptophan metabolites. Instead, in the absence of effective T cell receptor triggering, 3-HAA profoundly affects homeostatic proliferation of CD8(+) T cells.
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PMID:Differential effects of the tryptophan metabolite 3-hydroxyanthranilic acid on the proliferation of human CD8+ T cells induced by TCR triggering or homeostatic cytokines. 1638 30

The continually growing list of defined tumor antigens is broadening the potential applicability of tumor antigen-targeted cancer therapies. Although cancer vaccines and adoptive T-cell transfer have been shown to increase the frequency of circulating tumor antigen-specific T cells, these approaches cause clinical responses in a few patients. In melanoma, approximately one third of metastatic lesions contain activated T cells, including those specific for tumor antigens, arguing that the priming phase has occurred already in such individuals even without vaccination. These observations indicate that tumor resistance to immune destruction may dominate in many instances, arguing for a thorough analysis of the melanoma tumor microenvironment in individual patients. Recent work has suggested that T-cell anergy, the influence of CD4+ CD25+ regulatory T cells, the expression of inhibitory ligands, such as PD-L1, and the activity of nutrient-catabolizing enzymes, such as indoleamine 2,3-dioxygenase, may be involved. Preclinical murine models have shown that interfering with each of these processes can translate into T-cell-mediated tumor control. Importantly, each of these targets is amenable to clinical manipulation. Clinical translation of these approaches to counter negative regulation of antitumor immunity should receive high priority.
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PMID:Identifying and overcoming immune resistance mechanisms in the melanoma tumor microenvironment. 1660 53

The identification of tumor-expressed antigens that can be recognized by specific T lymphocytes has made it possible both to study the properties of T cells participating in anti-tumor immune responses in patients and also to develop antigen-specific immunotherapies as a treatment modality. Interestingly, moves toward intervention have proceeded at a faster pace than have investigations toward understanding. In melanoma in particular, many clinical trials of active immunization have been performed, and many of these have shown increases in tumor antigen-specific T cells circulating in the blood. However, clinical responses have been infrequent, arguing that mechanisms of resistance downstream from initial T cell priming may be dominant in many cases. In fact, may patients show spontaneous generation of immune effector cells and/or antibodies, implying that the priming phase has occurred already in such individuals even without vaccination. Recent attention has turned toward mechanisms of immune evasion at the effector phase of the anti-tumor immune response, predominantly within the tumor microenvironment. Evidence is accumulating that T cell-intrinsic hyporesponsiveness or anergy, extrinsic suppression by regulatory cell populations, inhibitory ligands such as PD-L1, soluble factors such as TGF-beta, and the activity of nutrient-catabolizing enzymes such as indoleamine 2,3-dioxygenase (IDO), may contribute to immune escape in different settings. Murine preclinical models have shown that interfering with each of these processes can translate into T cell-mediated tumor control. Clinical studies to estimate the frequency of specific immune evasion mechanisms in individual patients, to correlate specific events with clinical outcome, and to develop strategies to counter resistance mechanisms should receive a high priority.
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PMID:Immune suppression in the tumor microenvironment. 1669 66

Cutaneous melanoma is highly immunogenic, yet primary melanomas and metastases develop successfully in otherwise immunocompetent patients. To investigate the local immunosuppressive microenvironment, we examined the presence of suppressor T lymphocytes and tolerising dendritic cells (DCs), the expression of immunosuppressive cytokines (IL-10, TGFbeta1 and TGFbeta2) and the enzyme indoleamine 2,3-dioxygenase (IDO) using qRT-PCR and immunohistochemistry in primary skin melanomas, negative and positive sentinel lymph nodes (SLN), and lymph nodes with advanced metastases. Our results indicate that tolerogenic DCs and suppressor T lymphocytes are present in melanoma at all stages of disease progression. They express transforming growth factor beta receptor 1 (TGFbetaR1), and are therefore susceptible to TGFbeta1 and TGFbeta2 specifically expressed by primary melanoma. We found that expression of IDO and interleukin 10 (IL-10) increased with melanoma progression, with the highest concentration in positive SLN. We suggest that negative SLN contain immunosuppressive cells and cytokines, due to preconditioning by tolerogenic DCs migrating from the primary melanoma site to the SLN. In primary melanoma, TGFbeta2 is likely to render peripheral DCs tolerogenic, while in lymph nodes IDO and TGFbeta1 may have a major effect. This mechanism of tumour-associated immunosuppression may inhibit the immune response to the tumour and may explain the discrepancy between the induction of systemic immunity by anti-melanoma vaccines and their poor performance in the clinic.
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PMID:Mechanisms of local immunosuppression in cutaneous melanoma. 1756 41

Agents that interfere with tumoral immune tolerance may be useful to prevent or treat cancer. Brassinin is a phytoalexin, a class of natural products derived from plants that includes the widely known compound resveratrol. Brassinin has been demonstrated to have chemopreventive activity in preclinical models but the mechanisms underlying its anticancer properties are unknown. Here, we show that brassinin and a synthetic derivative 5-bromo-brassinin (5-Br-brassinin) are bioavailable inhibitors of indoleamine 2,3-dioxygenase (IDO), a pro-toleragenic enzyme that drives immune escape in cancer. Like other known IDO inhibitors, both of these compounds combined with chemotherapy to elicit regression of autochthonous mammary gland tumors in MMTV-Neu mice. Furthermore, growth of highly aggressive melanoma isograft tumors was suppressed by single agent treatment with 5-Br-brassinin. This response to treatment was lost in athymic mice, indicating a requirement for active host T-cell immunity, and in IDO-null knockout mice, providing direct genetic evidence that IDO inhibition is essential to the antitumor mechanism of action of 5-Br-brassinin. The natural product brassinin thus provides the structural basis for a new class of compounds with in vivo anticancer activity that is mediated through the inhibition of IDO.
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PMID:A key in vivo antitumor mechanism of action of natural product-based brassinins is inhibition of indoleamine 2,3-dioxygenase. 1802 37

Targeted delivery of IFNgamma to tumors has been achieved by fusing this cytokine with GCNGRC, a tumor neovasculature homing peptide. Although the therapeutic efficacy of this protein (called IFNgamma-NGR) in animal models is greater than that of IFNgamma, frequent administrations of IFNgamma-NGR may result in lower efficacy and tumor resistance. We investigated the role of indoleamine 2,3-dioxygenase (IDO), an IFNgamma-inducible enzyme that may down-regulate T cells by affecting local tryptophan catabolism in tumor resistance to repeated treatments with IFNgamma-NGR. The study was carried out in immunocompetent mice and in nu/nu mice bearing RMA lymphoma, B16F melanoma, or WEHI-164 fibrosarcoma and in vitro using cultured tumor cells. IDO activity was increased in lymphoma homogenates after multiple treatments with IFNgamma-NGR but not after a single treatment. Coadministration of 1-methyl-tryptophan, an inhibitor of IDO, increased tumor responses to multiple treatments in the lymphoma, melanoma, and fibrosarcoma models. No synergism between IFNgamma-NGR and 1-methyl-tryptophan was observed in vitro in tumor cell proliferation assays or in nu/nu tumor-bearing mice, suggesting that the antitumor effect was host mediated. We conclude that IDO is critically involved in tumor resistance to repeated treatments with IFNgamma-NGR, likely causing excessive stimulation of tryptophan catabolism and inhibiting antitumor immune mechanisms. Coadministration of IFNgamma-NGR with IDO inhibitors could represent a new strategy for increasing its antitumor activity.
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PMID:Critical role of indoleamine 2,3-dioxygenase in tumor resistance to repeated treatments with targeted IFNgamma. 1907 58

The immunoregulatory enzyme indoleamine 2,3-dioxygenase (IDO) is expressed by a subset of murine plasmacytoid DCs (pDCs) in tumor-draining lymph nodes (TDLNs), where it can potently activate Foxp3+ regulatory T cells (Tregs). We now show that IDO functions as a molecular switch in TDLNs, maintaining Tregs in their normal suppressive phenotype when IDO was active, but allowing inflammation-induced conversion of Tregs to a polyfunctional T-helper phenotype similar to proinflammatory T-helper-17 (TH17) cells when IDO was blocked. In vitro, conversion of Tregs to the TH17-like phenotype was driven by antigen-activated effector T cells and required interleukin-6 (IL-6) produced by activated pDCs. IDO regulated this conversion by dominantly suppressing production of IL-6 in pDCs, in a GCN2-kinase dependent fashion. In vivo, using a model of established B16 melanoma, the combination of an IDO-inhibitor drug plus antitumor vaccine caused up-regulation of IL-6 in pDCs and in situ conversion of a majority of Tregs to the TH17 phenotype, with marked enhancement of CD8+ T-cell activation and antitumor efficacy. Thus, Tregs in TDLNs can be actively reprogrammed in situ into T-helper cells, without the need for physical depletion, and IDO serves as a key regulator of this critical conversion.
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PMID:Indoleamine 2,3-dioxygenase controls conversion of Foxp3+ Tregs to TH17-like cells in tumor-draining lymph nodes. 1936 86

The mechanism by which malignant melanoma (MM) cells survive in lymph nodes is poorly understood. One possible mechanism by which MM cells can escape immune surveillance is through upregulation of immunomodulatory enzymes such as indoleamine 2,3-dioxygenase (IDO). In this study, 25 cases of MM lymph node metastases from patients with long and short survival were evaluated for expression of IDO and the number of Forkhead box p3 (FOXP3)-expressing regulatory T cells. Moderate to strong cytoplasmic IDO expression was present in all (15/15) MM lymph node metastases in patients with poor survival. Eight of 10 patients with metastatic MM and long survival were negative or only weakly positive for IDO. Upregulation of IDO in metastatic MM cells was associated with an increased number of regulatory T cells (Tregs). There was a statistically significant association between shorter survival and both a stronger IDO expression (p = 0.0019) and a higher number of FOXP3 expressing Tregs (p < 0.001). Using RT-PCR analysis, we showed that IDO expression in MM cells is induced by interferon-gamma. These data support the notion that metastatic MM cells select for expression of IDO to evade immunologic detection. Therefore, inhibition of IDO in MM patients may be a useful treatment strategy.
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PMID:Expression of indoleamine 2,3-dioxygenase in metastatic malignant melanoma recruits regulatory T cells to avoid immune detection and affects survival. 1947 Nov 23

A hydroxyamidine chemotype has been discovered as a key pharmacophore in novel inhibitors of indoleamine 2,3-dioxygenase (IDO). Optimization led to the identification of 5l, which is a potent (HeLa IC(50) = 19 nM) competitive inhibitor of IDO. Testing of 5l in mice demonstrated pharmacodynamic inhibition of IDO, as measured by decreased kynurenine levels (>50%) in plasma and dose dependent efficacy in mice bearing GM-CSF-secreting B16 melanoma tumors.
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PMID:Discovery of potent competitive inhibitors of indoleamine 2,3-dioxygenase with in vivo pharmacodynamic activity and efficacy in a mouse melanoma model. 1950 62


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