A Longitudinal Analysis of IDO and PDL1 Expression during Immune- or Targeted Therapy in Advanced Melanoma

Targeting Tryptophan Catabolism in Ovarian Cancer to Attenuate Macrophage Infiltration and PD-L1 Expression

High-grade serous carcinoma (HGSC) of the fallopian tube, ovary, and peritoneum is the most common type of ovarian cancer and is predicted to be immunogenic because the presence of tumor-infiltrating lymphocytes conveys a better prognosis. However, the efficacy of immunotherapies has been limited because of the immune-suppressed tumor microenvironment (TME). Tumor metabolism and immune-suppressive metabolites directly affect immune cell function through the depletion of nutrients and activation of immune-suppressive transcriptional programs. Tryptophan (TRP) catabolism is a contributor to HGSC disease progression. Two structurally distinct rate-limiting TRP catabolizing enzymes, indoleamine 2,3-dioxygenase 1 (IDO1) and tryptophan 2,3-dioxygenase 2 (TDO2), evolved separately to catabolize TRP. IDO1/TDO2 are aberrantly expressed in carcinomas and metabolize TRP into the immune-suppressive metabolite kynurenine (KYN), which can engage the aryl hydrocarbon receptor to drive immunosuppressive transcriptional programs. To date, IDO inhibitors tested in clinical trials have had limited efficacy, but those inhibitors did not target TDO2, and we find that HGSC cell lines and clinical outcomes are more dependent on TDO2 than IDO1. To identify inflammatory HGSC cancers with poor prognosis, we stratified patient ascites samples by IL6 status, which correlates with poor prognosis. Metabolomics revealed that IL6-high patient samples had enriched KYN. TDO2 knockdown significantly inhibited HGSC growth and TRP catabolism. The orally available dual IDO1/TDO2 inhibitor, AT-0174, significantly inhibited tumor progression, reduced tumor-associated macrophages, and reduced expression of immune-suppressive proteins on immune and tumor cells. These studies demonstrate the importance of TDO2 and the therapeutic potential of AT-0174 to overcome an immune-suppressed TME.

SIGNIFICANCE

Developing strategies to improve response to chemotherapy is essential to extending disease-free intervals for patients with HGSC of the fallopian tube, ovary, and peritoneum. In this article, we demonstrate that targeting TRP catabolism, particularly with dual inhibition of TDO2 and IDO1, attenuates the immune-suppressive microenvironment and, when combined with chemotherapy, extends survival compared with chemotherapy alone.

The Aryl Hydrocarbon Receptor: Impact on the Tumor Immune Microenvironment and Modulation as a Potential Therapy

The aryl hydrocarbon receptor (AhR) is a ubiquitous nuclear receptor with a broad range of functions, both in tumor cells and immune cells within the tumor microenvironment (TME). Activation of AhR has been shown to have a carcinogenic effect in a variety of organs, through induction of cellular proliferation and migration, promotion of epithelial-to-mesenchymal transition, and inhibition of apoptosis, among other functions. However, the impact on immune cell function is more complicated, with both pro- and anti-tumorigenic roles identified. Although targeting AhR in cancer has shown significant promise in pre-clinical studies, there has been limited efficacy in phase III clinical trials to date. With the contrasting roles of AhR activation on immune cell polarization, understanding the impact of AhR activation on the tumor immune microenvironment is necessary to guide therapies targeting the AhR. This review article summarizes the state of knowledge of AhR activation on the TME, limitations of current findings, and the potential for modulation of the AhR as a cancer therapy.

Indoleamine 2,3-dioxygenase 1 in circumventing checkpoint inhibitor responses: Updated

Metabolic alterations occur commonly in tumor cells as a way to adapt available energetic sources for their proliferation, survival and resistance. Indoleamine 2,3-dioxygenase 1 (IDO1) is an intracellular enzyme catalyzing tryptophan degradation into kynurenine. IDO1 expression shows a rise in the stroma of many types of human cancers, and it provides a negative feedback mechanism for cancer evasion from immunosurveillance. Upregulation of IDO1 correlates with cancer aggression, poor prognosis and shortened patient survival. The increased activity of this endogenous checkpoint impairs effector T cell function, increases regulatory T cell (Treg) population and induces immune tolerance, so its inhibition potentiates anti-tumor immune responses and reshapes immunogenic state of tumor microenvironment (TME) presumably through normalizing effector T cell activity. A point is that the expression of this immunoregulatory marker is upregulated after immune checkpoint inhibitor (ICI) therapy, and that it has inducible effect on expression of other checkpoints. These are indicative of the importance of IDO1 as an attractive immunotherapeutic target and rationalizing combination of IDO1 inhibitors with ICI drugs in patients with advanced solid cancers. In this review, we aimed to discuss about the impact of IDO1 on tumor immune ecosystem, and the IDO1-mediated bypass of ICI therapy. The efficacy of IDO1 inhibitor therapy in combination with ICIs in advanced/metastatic solid tumors is also a focus of this paper.

Phase 1/2 study of epacadostat in combination with durvalumab in patients with metastatic solid tumors

BACKGROUND

Targeting programmed cell death protein 1 (PD-1) and indoleamine 2,3-dioxygenase (IDO1) pathways is an appealing option for cancer treatment.

METHODS

The open-label, phase 1/2 ECHO-203 study evaluated the safety, tolerability, and efficacy of the IDO1 inhibitor epacadostat in combination with durvalumab, a human anti-PD-L1 monoclonal antibody in adult patients with advanced solid tumors.

RESULTS

The most common treatment-related adverse events were fatigue (30.7%), nausea (21.0%), decreased appetite (13.1%), pruritus (12.5%), maculopapular rash (10.8%), and diarrhea (10.2%). Objective response rate (ORR) in the overall phase 2 population was 12.0%. Higher ORR was observed in immune checkpoint inhibitor (CPI)-naïve patients (16.1%) compared with patients who had received previous CPI (4.1%). Epacadostat pharmacodynamics were evaluated by comparing baseline kynurenine levels with those on therapy at various time points. Only the 300-mg epacadostat dose showed evidence of kynurenine modulation, albeit unsustained.

CONCLUSIONS

Epacadostat plus durvalumab was generally well tolerated in patients with advanced solid tumors. ORR was low, and evaluation of kynurenine concentration from baseline to cycle 2, day 1, and cycle 5, day 1, suggested >300 mg epacadostat twice daily is needed to ensure sufficient drug effect.

CLINICAL TRIAL INFORMATION

A study of epacadostat (INCB024360) in combination with durvalumab (MEDI4736) in subjects with selected advanced solid tumors (ECHO-203) (NCT02318277).

Triple blockade of Ido-1, PD-L1 and MEK as a potential therapeutic strategy in NSCLC

BACKGROUND

Despite the recent progress in the treatment and outcome of Non Small Cell Lung Cancer (NSCLC), immunotherapy has still significant limitations reporting a significant proportion of patients not benefiting from therapy, even in patients with high PD-L1 expression. We have previously demonstrated that the combined inhibition of MEK and PD-L1 in NSCLC patients derived three dimensional cultures exerted significant synergistic effect in terms of immune-dependent cancer cell death. However, subsequent experiments analyzing the expression of Indoleamine 2,3-dioxygenase-1 (Ido-1) gene expression demonstrated that Ido-1 resulted unaffected by the MEK inhibition and even increased after the combined inhibition of MEK and PD-L1 thus representing a potential escape mechanism to this combination.

METHODS

We analyzed transcriptomic profile of NSCLC lung adenocarcinoma cohort of TCGA (The Cancer Genome Atlas), stratifying tumors based on EMT (Epithelial mesenchymal Transition) score; in parallel, we investigated the activation of Ido-1 pathway and modulation of immune cytokines productions both in NSCLC cells lines, in peripheral blood mononuclear cells (PBMCs) and in ex-vivo NSCLC spheroids induced by triple inhibition with an anti-PD-L1 monoclonal antibody, the MEK inhibitor and the Ido-1 inhibitor.

RESULTS

In NSCLC lung adenocarcinoma patient cohort (from TCGA) Ido-1 gene expression was significantly higher in samples classified as mesenchymal according EMT score. Similarly, on a selected panel of NSCLC cell lines higher expression of MEK and Ido-1 related genes was detected in cells with mesenchymal phenotype according EMT score, thus suggesting a potential correlation of co-activation of these two pathways in the context of EMT, with cancer cells sustaining an immune-suppressive microenvironment. While exerting an antitumor activity, the dual blockade of MEK and PD-L1 enhances the secretion of pro-inflammatory cytokines (IFNγ, TNFα, IL-12 and IL-6) and, consequently, the expression of new immune checkpoints such as Ido-1. The triple inhibition with an anti-PD-L1 monoclonal antibody, the MEK inhibitor and the Ido-1 inhibitor demonstrated significant antiproliferative and proapoptotic activity on ex-vivo NSCLC samples; at the same time the triple combination kept increased the levels of pro-inflammatory cytokines produced by both PBMCs and tumor spheroids in order to sustain the immune response and simultaneously decreased the expression of other checkpoint (such as CTLA-4, Ido-1 and TIM-3) thus promoting an immune-reactive and inflamed micro-environment.

CONCLUSIONS

We show that Ido-1 activation is a possible escape mechanism to immune-mediated cell death induced by combination of PD-L1 and MEK inhibitors: also, we show that triple combination of anti-PD-L1, anti-MEK and anti-Ido-1 drugs may overcome this negative feedback and restore anti-tumor immune response in NSCLC patients' derived three dimensional cultures.

Enhancing immunotherapy in cancer by targeting emerging immunomodulatory pathways

The discovery and clinical implementation of immune-checkpoint inhibitors (ICIs) targeting CTLA4, PD-1 and PD-L1 has revolutionized the treatment of cancer, as recognized by the 2018 Nobel Prize for Medicine and Physiology. This groundbreaking new approach has improved the outcomes of patients with various forms of advanced-stage cancer; however, the majority of patients receiving these therapies, even in combination, do not derive clinical benefit. Further development of agents targeting additional immune checkpoints, co-stimulatory receptors and/or co-inhibitory receptors that control T cell function is therefore critical. In this Review, we discuss the translational potential and clinical development of agents targeting both co-stimulatory and co-inhibitory T cell receptors. Specifically, we describe their mechanisms of action, and provide an overview of ongoing clinical trials involving novel ICIs including those targeting LAG3, TIM3, TIGIT and BTLA as well as agonists of the co-stimulatory receptors GITR, OX40, 41BB and ICOS. We also discuss several additional approaches, such as harnessing T cell metabolism, in particular via adenosine signalling, inhibition of IDO1, and targeting changes in glucose and fatty acid metabolism. We conclude that further efforts are needed to optimize the timing of combination ICI approaches and, most importantly, to individualize immunotherapy based on both patient-specific and tumour-specific characteristics.

Prognostic Biomarkers in Melanoma: Tailoring Treatments to the Patient

BACKGROUND

It is often difficult to accurately predict how a melanoma will progress because melanomas can be so diverse in their genetic and histological makeup.

OBJECTIVE

We sought to characterize the current state and progression of biomedical markers towards their utilization as prognostic indicators for patients with melanoma.

METHODS

A literature search of the research repository databases PubMed and GoogleScholar was conducted using the following inclusion criteria: (1) published within the last 10 years, and (2) use of overall survival, disease progression, or clinical outcome as primary endpoints. Search terms included various permutations of "biomarkers," "prognostic," "immunologic," "serologic," "visual," and "melanoma." Results were evaluated for statistical power, results significance, and experimental design integrity.

RESULTS

The prognostic capabilities of clinical tests for malignant melanoma have made great strides in the last few years, with several serologic and immunohistochemical biomarkers being preliminarily linked to various measures of clinical prognosis. While clinical feasibility of a single sensitive and specific biomarker remains unfeasible, use of select combinations of tested biomarkers remain viable.

CONCLUSION

Diagnostic and prognostic genetic assays have begun to cross over from research to commercial application, giving physicians additional tools during the early stages of diagnosis to optimize and individualize treatments.

Guiding immunotherapy combinations: Who gets what?

Although PD-1 and CTLA-4 inhibitors have proven successful in a range of malignancies, there are subsets of patients that do not respond to these agents due to upregulation of adaptive and innate resistance mechanisms by the tumor and its surrounding microenvironment. As new immunotherapeutic strategies are developed, there is a need for rational implementation of novel immunotherapy combinations that target complementary mechanisms of immunotherapy resistance intrinsic to each patient and tumor type. In this short review, we cover mechanisms by which tumors evade the immune system, as well as summarize available clinical data on emerging therapeutic agents that target these defense mechanisms. Rational implementation of combination immunotherapy targeting patient- and malignancy-specific immune evasion mechanisms may thus lead to enhanced response rates and allow immunotherapy to be effective even in tumors that are historically considered poorly responsive to immunotherapy.

PD-L1/PD-1 and CTLA-4 Expression in Equine Penile Squamous Cell Carcinomas

In horses, penile squamous cell carcinomas (epSCCs) are among the most common cutaneous neoplastic lesions. These tumors usually arise in benign lesions such as viral plaques and papillomas frequently induced by Equus caballus papillomavirus type 2 (EcPV2) infection. In the last decade, the introduction of immune checkpoint inhibitors (ICI) for the treatment of human cancers has demonstrated promising results. Among the most commonly targeted pathways, there is PD-1/PD-L1 and CTLA-4. The aim of this study is to investigate the expression of the PD-1/PD-L1 pathway and CTLA-4 in the tumor microenvironment of epSCCs to assess the feasibility of an immunotherapeutic approach. Twenty equine epithelial tumors were retrospectively selected and submitted to RT-qPCR for PD-1 and PD-L1 genes. After testing antibodies cross-reactivity by western blotting, immunohistochemistry for PD-L1 and CTLA-4 was performed. Results from RT-qPCR demonstrated that 3/20 cases expressed the PD-L1 gene, whereas the PD-1 gene was not detected. Immunohistochemical positivity for PD-L1 was found only in one case. CTLA-4-positive cells were observe in all cases but were few (Mdn = 4.8; IQR = 2.3-7.1 cells/HPF). In this study group, PD-1/PD-L1 and CTLA-4 do not appear to be highly expressed and therefore the use of ICI in epSCCs may not have promising rates of response.

Kynurenines as a Novel Target for the Treatment of Malignancies

Malignancies are unquestionably a significant public health problem. Their effective treatment is still a big challenge for modern medicine. Tumors have developed a wide range of mechanisms to evade an immune and therapeutic response. As a result, there is an unmet clinical need for research on solutions aimed at overcoming this problem. An accumulation of tryptophan metabolites belonging to the kynurenine pathway can enhance neoplastic progression because it causes the suppression of immune system response against cancer cells. They are also involved in the development of the mechanisms responsible for the resistance to antitumor therapy. Kynurenine belongs to the most potent immunosuppressive metabolites of this pathway and has a significant impact on the development of malignancies. This fact prompted researchers to assess whether targeting the enzymes responsible for its synthesis could be an effective therapeutic strategy for various cancers. To date, numerous studies, both preclinical and clinical, have been conducted on this topic, especially regarding the inhibition of indoleamine 2,3-dioxygenase activity and their results can be considered noteworthy. This review gathers and systematizes the knowledge about the role of the kynurenine pathway in neoplastic progression and the findings regarding the usefulness of modulating its activity in anticancer therapy.

Value of PD-L1, PD-1, and CTLA-4 Expression in the Clinical Practice as Predictors of Response to Nivolumab and Ipilimumab in Monotherapy in Patients With Advanced Stage Melanoma

BACKGROUND

The introduction of immune checkpoint inhibitors (ICI) has improved the survival outcomes of patients with advanced melanoma. To date, only a few studies have evaluated the immunohistochemical (IHC) expression of PD-1 and CTLA-4 in tumor-infiltrating lymphocytes (TILs) as predictive markers of response to ICI, most of them in the context of clinical trials. Moreover, the predictive value of PD-L1 in melanoma cells in the response to immunotherapy is unclear. The aim of our study was to assess the IHC expression of PD-L1, PD-1, and CTLA-4 in samples of patients with advanced melanoma and to establish their prognostic value as predictors of ICI response in a university hospital.

METHODS

The expression of PD-L1, PD-1, and CTLA-4 was evaluated in pretreatment tumor samples in a series of 35 patients, 21 patients treated with nivolumab and 14 patients with ipilimumab in monotherapy.

RESULTS

In the nivolumab group, 4 tumors (19%) were positive for PD-L1 and all of them showed a partial response to the treatment. However, 4 patients whose tumors did not express PD-L1 also responded to nivolumab. PD-1 expression was not associated with better progression-free survival (PFS). In the ipilimumab group, 5 patients (35.7%) showed expression of CTLA-4. Positive cases showed a better PFS; however, one negative case responded to ipilimumab.

CONCLUSIONS

Nivolumab produces a better response compared with ipilimumab in patients with melanoma. The IHC expression of PD-L1 and CTLA-4 are associated with a higher response rate to nivolumab and ipilimumab, respectively, and better PFS, but the existence of responder patients with negative expression suggests that they are not adequate biomarkers to select candidate patients for ICI in the clinical practice.

The Influence of Tumor Microenvironment on Immune Escape of Melanoma

The low efficiency of currently-used anti-cancer therapies poses a serious challenge, especially in the case of malignant melanoma, a cancer characterized by elevated invasiveness and relatively high mortality rate. The role of the tumor microenvironment in the progression of melanoma and its acquisition of resistance to treatment seems to be the main focus of recent studies. One of the factors that, in normal conditions, aids the organism in its fight against the cancer and, following the malignant transformation, adapts to facilitate the development of the tumor is the immune system. A variety of cell types, i.e., T and B lymphocytes, macrophages, and dendritic and natural killer cells, as well as neutrophils, support the growth and invasiveness of melanoma cells, utilizing a plethora of mechanisms, including secretion of pro-inflammatory molecules, induction of inhibitory receptors expression, or depletion of essential nutrients. This review provides a comprehensive summary of the processes regulated by tumor-associated cells that promote the immune escape of melanoma cells. The described mechanisms offer potential new targets for anti-cancer treatment and should be further studied to improve currently-employed therapies.

Tumor Genotype Is Shaping Immunophenotype and Responses to Immune Checkpoint Inhibitors in Solid Tumors

A major breakthrough in cancer treatment was ushered in by the development of immune checkpoint blockade therapy such as anti-CTLA4 antibody and anti-PD-1 and anti-programmed cell death-ligand 1 antibodies that are now approved for use in an increasing number of malignancies. Despite the relative success of immune checkpoint inhibitors with certain tumor types, many patients still fail to respond to such therapies, and the field is actively trying to understand the mechanisms of resistance, intrinsic or acquired, to immune checkpoint blockade. Herein, we discuss the roles that somatic genomic mutations in oncogenic pathways play in immune editing, as well as some of the current approaches toward improving response to immunotherapy.

Immunotherapy in the Treatment of Metastatic Melanoma: Current Knowledge and Future Directions

Melanoma is one of the most immunologic malignancies based on its higher prevalence in immune-compromised patients, the evidence of brisk lymphocytic infiltrates in both primary tumors and metastases, the documented recognition of melanoma antigens by tumor-infiltrating T lymphocytes and, most important, evidence that melanoma responds to immunotherapy. The use of immunotherapy in the treatment of metastatic melanoma is a relatively late discovery for this malignancy. Recent studies have shown a significantly higher success rate with combination of immunotherapy and chemotherapy, radiotherapy, or targeted molecular therapy. Immunotherapy is associated to a panel of dysimmune toxicities called immune-related adverse events that can affect one or more organs and may limit its use. Future directions in the treatment of metastatic melanoma include immunotherapy with anti-PD1 antibodies or targeted therapy with BRAF and MEK inhibitors.

Indoleamine 2,3-dioxygenase in melanoma progression and BRAF inhibitor resistance

Indoleamine 2,3-dioxygenase (IDO) is associated with the progression of many types of tumors, including melanoma. However, there is limited information about IDO modulation on tumor cell itself and the effect of BRAF inhibitor (BRAFi) treatment and resistance. Herein, IDO expression was analyzed in different stages of melanoma development and progression linked to BRAFi resistance. IDO expression was increased in primary and metastatic melanomas from patients' biopsies, especially in the immune cells infiltrate. Using a bioinformatics approach, we also identified an increase in the IDO mRNA in the vertical growth and metastatic phases of melanoma. Using in silico analyses, we found that IDO mRNA was increased in BRAFi resistance. In an in vitro model, IDO expression and activity induced by interferon-gamma (IFNγ) in sensitive melanoma cells was decreased by BRAFi treatment. However, cells that became resistant to BRAFi presented random IDO expression levels. Also, we identified that treatment with the IDO inhibitor, 1-methyltryptophan (1-MT), was able to reduce clonogenicity for parental and BRAFi-resistant cells. In conclusion, our results support the hypothesis that the decreased IDO expression in tumor cells is one of the many additional outcomes contributing to the therapeutic effects of BRAFi. Still, the IDO production changeability by the BRAFi-resistant cells reiterates the complexity of the response arising from resistance, making it not possible, at this stage, to associate IDO expression in tumor cells with resistance. On the other hand, the maintenance of 1-MT off-target effect endorses its use as an adjuvant treatment of melanoma that has become BRAFi-resistant.

Improving cancer immunotherapy using nanomedicines: progress, opportunities and challenges

Multiple nanotherapeutics have been approved for patients with cancer, but their effects on survival have been modest and, in some examples, less than those of other approved therapies. At the same time, the clinical successes achieved with immunotherapy have revolutionized the treatment of multiple advanced-stage malignancies. However, the majority of patients do not benefit from the currently available immunotherapies and many develop immune-related adverse events. By contrast, nanomedicines can reduce - but do not eliminate - the risk of certain life-threatening toxicities. Thus, the combination of these therapeutic classes is of intense research interest. The tumour microenvironment (TME) is a major cause of the failure of both nanomedicines and immunotherapies that not only limits delivery, but also can compromise efficacy, even when agents accumulate in the TME. Coincidentally, the same TME features that impair nanomedicine delivery can also cause immunosuppression. In this Perspective, we describe TME normalization strategies that have the potential to simultaneously promote the delivery of nanomedicines and reduce immunosuppression in the TME. Then, we discuss the potential of a combined nanomedicine-based TME normalization and immunotherapeutic strategy designed to overcome each step of the cancer-immunity cycle and propose a broadly applicable 'minimal combination' of therapies designed to increase the number of patients with cancer who are able to benefit from immunotherapy.

Macrophages/Microglia Represent the Major Source of Indolamine 2,3-Dioxygenase Expression in Melanoma Metastases of the Brain

The manifestation of brain metastases in patients with advanced melanoma is a common event that limits patient's survival and quality of life. The immunosuppressive properties of the brain parenchyma are very different compared to the rest of the body, making it plausible that the current success of cancer immunotherapies is specifically limited here. In melanoma brain metastases, the reciprocal interplay between immunosuppressive mediators such as indoleamine 2, 3-dioxygenase (IDO) or programmed cell death-ligand 1 (PD-L1) in the context of neoplastic transformation are far from being understood. Therefore, we analyzed the immunoreactive infiltrate (CD45, CD3, CD8, Forkhead box P3 [FoxP3], CD11c, CD23, CD123, CD68, Allograft Inflammatory factor 1[AIF-1]) and PD-L1 with respect to IDO expression and localization in melanoma brain metastases but also in matched metastases at extracranial sites to correlate intra- and interpatient data with therapy response and survival. Comparative tissue analysis identified macrophages/microglia as the major source of IDO expression in melanoma brain metastases. In contrast to the tumor infiltrating lymphocytes, melanoma cells per se exhibited low IDO expression levels paralleled by cell surface presentation of PD-L1 in intracranial metastases. Absolute numbers and pattern of IDO-expressing cells in metastases of the brain correlated with recruitment and localization of CD8⁺ T cells, implicating dynamic impact on the regulation of T cell function in the brain parenchyma. However, paired analysis of matched intra- and extracranial metastases identified significantly lower fractions of cytotoxic CD8⁺ T cells in intracranial metastases while all other immune cell populations remain unchanged. In line with the already established clinical benefit for PD-L1 expression in extracranial melanoma metastases, Kaplan-Meier analyses correlated PD-L1 expression in brain metastases with favorable outcome in advanced melanoma patients undergoing immune checkpoint therapy. In summary, our data provide new insights into the landscape of immunosuppressive factors in melanoma brain metastases that may be useful in the implication of novel therapeutic strategies for patients undergoing cancer immunotherapy.

DNA methylation of indoleamine 2,3-dioxygenase 1 (IDO1) in head and neck squamous cell carcinomas correlates with IDO1 expression, HPV status, patients' survival, immune cell infiltrates, mutational load, and interferon γ signature

Background

The immune checkpoint, indoleamine 2,3-dioxygenase 1, is under investigation as target of novel immunotherapies for cancers, including head and neck squamous cell carcinomas (HNSCC). The aim of our study was to analyze DNA methylation of the encoding gene (IDO1) in HNSCC.

Methods

Methylation of three CpG sites within the promoter, promoter flank, and gene body was investigated and correlated with mRNA expression, immune cell infiltration, mutational burden, human papillomavirus (HPV)-status, and overall survival in a cohort of N = 528 HNSCC patients obtained from The Cancer Genome Atlas. In addition, IDO1 immunohistochemistry and DNA methylation analysis was performed in an independent cohort of N = 138 HNSCC samples.

Findings

Significant inverse correlations of IDO1 methylation and IDO1 mRNA expression were found in the promoter and promoter flank region (Spearman's ρ = −0.163 and ρ = −0.377, respectively) while a positive correlation was present in the gene body (ρ = 0.502; all P < 0.001). IDO1 DNA methylation significantly correlated with IDO1 protein expressing immune cells as well as tumor cells. IDO1 promoter flank hypermethylation was significantly associated with poor overall survival (P < 0.001). In addition, we discovered significant correlations between IDO1 methylation and expression with RNA signatures of immune cell infiltrates and with HPV-status, mutational load (methylation only), and interferon γ signature.

Interpretation

Our results suggest IDO1 expression levels are epigenetically regulated by DNA methylation. This study provides rationale to test IDO1 methylation as potential biomarker for prediction of response to IDO1 immune checkpoint inhibitors in HNSCC.

Unraveling the crosstalk between melanoma and immune cells in the tumor microenvironment

Cutaneous melanoma is the most common skin cancer with an incidence that has been rapidly increasing in the past decades. Melanomas are among the most immunogenic tumors and, as such, have the greatest potential to respond favorably to immunotherapy. However, like many cancers, melanomas acquire various suppressive mechanisms, which generally act in concert, to escape innate and adaptive immune detection and destruction. Intense research into the cellular and molecular events associated with melanomagenesis, which ultimately lead to immune suppression, has resulted in the discovery of new therapeutic targets and synergistic combinations of immunotherapy, targeted therapy and chemotherapy. Tremendous effort to determine efficacy of single and combination therapies in pre-clinical and clinical phase I-III trials has led to FDA-approval of several immunotherapeutic agents that could potentially be beneficial for aggressive, highly refractory, advanced and metastatic melanomas. The increasing availability of approved combination therapies for melanoma and more rapid assessment of patient tumors has increased the feasibility of personalized treatment to overcome patient and tumor heterogeneity and to achieve greater clinical benefit. Here, we review the evolution of the immune system during melanomagenesis, mechanisms exploited by melanoma to suppress anti-tumor immunity and methods that have been developed to restore immunity. We emphasize that an effective therapeutic strategy will require coordinate activation of tumor-specific immunity as well as increased recognition and accessibility of melanoma cells in primary tumors and distal metastases. This review integrates available knowledge on melanoma-specific immunity, molecular signaling pathways and molecular targeting strategies that could be utilized to envision therapeutics with broader application and greater efficacy for early stage and advanced metastatic melanoma.

Limitations and Off-Target Effects of Tryptophan-Related IDO Inhibitors in Cancer Treatment

Immunooncology is still a growing area in cancer therapy. Drugs within this therapeutic approach do not directly target/attack the tumor but interfere with immune checkpoints and target or reprogram key metabolic pathways critical for anti-cancer immune defense. Indolamine 2,3-dioxygenase 1 (IDO1) and the tryptophan (TRP)-kynurenine pathway were identified as critical mechanisms in cancer immune escape and their inhibition as an approach with promising therapeutic potential. Particularly, a multitude of IDO1 inhibiting tryptophan analogs are widely applied in several clinical trials. However, this therapy results in a variety of implications for the patient's physiology. This is not only due to the inhibition of an enzyme important in almost every organ and tissue in the body but also because of the general nature of the inhibitor as an analog of a proteinogenic amino acid as well as the initiation of cellular detoxification known to affect inflammatory pathways. In this review we provide a deeper insight into the physiological consequences of an IDO1 inhibiting therapy based on TRP related molecules. We discuss potential side and off-target effects that contribute to the interpretation of unexpected positive as well as negative results of ongoing or discontinued clinical studies while we also highlight the potential of these inhibitors independent of the IDO1 signaling pathway.

Epacadostat plus pembrolizumab versus placebo plus pembrolizumab in patients with unresectable or metastatic melanoma (ECHO-301/KEYNOTE-252): a phase 3, randomised, double-blind study

BACKGROUND

Immunotherapy combination treatments can improve patient outcomes. Epacadostat, an IDO1 selective inhibitor, and pembrolizumab, a PD-1 inhibitor, showed promising antitumour activity in the phase 1-2 ECHO-202/KEYNOTE-037 study in advanced melanoma. In this trial, we aimed to compare progression-free survival and overall survival in patients with unresectable stage III or IV melanoma receiving epacadostat plus pembrolizumab versus placebo plus pembrolizumab.

METHODS

In this international, randomised, placebo-controlled, double-blind, parallel-group, phase 3 trial, eligible participants were aged 18 years or older, with unresectable stage III or IV melanoma previously untreated with PD-1 or PD-L1 checkpoint inhibitors, an ECOG performance status of 0 or 1, and had a known BRAF^V600 mutant status or consented to BRAF^V600 mutation testing during screening. Patients were stratified by PD-L1 expression and BRAF^V600 mutation status and randomly assigned (1:1) through a central interactive voice and integrated web response system to receive epacadostat 100 mg orally twice daily plus pembrolizumab 200 mg intravenously every 3 weeks or placebo plus pembrolizumab for up to 2 years. We used block randomisation with a block size of four in each stratum. Primary endpoints were progression-free survival and overall survival in the intention-to-treat population. The safety analysis population included randomly assigned patients who received at least one dose of study treatment. The study was stopped after the second interim analysis; follow-up for safety is ongoing. This study is registered with ClinicalTrials.gov, number NCT02752074.

FINDINGS

Between June 21, 2016, and Aug 7, 2017, 928 patients were screened and 706 patients were randomly assigned to receive epacadostat plus pembrolizumab (n=354) or placebo plus pembrolizumab (n=352). Median follow-up was 12·4 months (IQR 10·3-14·5). No significant differences were found between the treatment groups for progression-free survival (median 4·7 months, 95% CI 2·9-6·8, for epacadostat plus pembrolizumab vs 4·9 months, 2·9-6·8, for placebo plus pembrolizumab; hazard ratio [HR] 1·00, 95% CI 0·83-1·21; one-sided p=0·52) or overall survival (median not reached in either group; epacadostat plus pembrolizumab vs placebo plus pembrolizumab: HR 1·13, 0·86-1·49; one-sided p=0·81). The most common grade 3 or worse treatment-related adverse event was lipase increase, which occurred in 14 (4%) of 353 patients receiving epacadostat plus pembrolizumab and 11 (3%) of 352 patients receiving placebo plus pembrolizumab. Treatment-related serious adverse events were reported in 37 (10%) of 353 patients receiving epacadostat plus pembrolizumab and 32 (9%) of 352 patients receiving placebo plus pembrolizumab. There were no treatment-related deaths in either treatment group.

INTERPRETATION

Epacadostat 100 mg twice daily plus pembrolizumab did not improve progression-free survival or overall survival compared with placebo plus pembrolizumab in patients with unresectable or metastatic melanoma. The usefulness of IDO1 inhibition as a strategy to enhance anti-PD-1 therapy activity in cancer remains uncertain.

FUNDING

Incyte Corporation, in collaboration with Merck Sharp & Dohme.

Inter- and intrapatient heterogeneity of indoleamine 2,3-dioxygenase expression in primary and metastatic melanoma cells and the tumour microenvironment

AIMS

Indoleamine 2,3-dioxygenase (IDO), an immunomodulatory enzyme, facilitates immune escape by tumours and promotes tumour progression. IDO inhibitors with and without additional anti-PD-1 therapy have been evaluated in recent and ongoing melanoma clinical trials, but IDO expression in melanoma tumours, and therefore its potential role as a predictive biomarker remains unknown. This study sought to evaluate IDO expression in immunotherapy-naive metastatic melanoma patients in order to determine patterns of expression in corresponding primary melanomas, locoregional metastases and distant metastases.

METHODS AND RESULTS

Here, we evaluated IDO expression using immunohistochemistry in 99 melanoma tumour samples from 43 immunotherapy-naive patients with metastatic melanoma to determine patterns of expression in primary melanomas (n = 29), locoregional metastases (n = 36) and distant metastases (n = 34). Thirty-seven per cent of patients demonstrated tumour IDO expression in at least one specimen. Twelve of 35 patients (34%) with longitudinal specimens (i.e. two or more separate specimens from different disease stages in the same patient) displayed heterogeneous IDO staining between samples. Tumour IDO expression positively correlated with tumour-infiltrating lymphocyte (TIL) score as well as the number of IDO-expressing mononuclear cells in the primary melanoma (P < 0.0001 and P = 0.0011, respectively) and nodal metastases (P = 0.049 and P = 0.037, respectively), but not in distant metastases. Furthermore, tumour IDO expression correlated positively with PD-L1 expression by melanoma cells among all specimens (P = 0.0073).

CONCLUSIONS

Therefore, while assessment of tumour IDO expression warrants evaluation in melanoma patient cohorts treated with IDO inhibitors dosed at levels proven to inhibit the target by pharmacodynamic assessment, its utility as a biomarker may be limited by intertumoral heterogeneity.

The Tumor Vascular Endothelium as Decision Maker in Cancer Therapy

Genetic and pathophysiologic criteria prearrange the uncontrolled growth of neoplastic cells that in turn initiates new vessel formation, which is prerequisite for further tumor growth and progression. This first endothelial lining is patchy, disordered in structure and thus, angiogenic tumor vessels were proven to be functionally inferior. As a result, tumors were characterized by areas with an apparent oversupply in addition to areas with an undersupply of vessels, which complicates an efficient administration of intravenous drugs in cancer therapy and might even lower the response e.g. of radiotherapy (RT) because of the inefficient oxygen supply. In addition to the vascular dysfunction, tumor blood vessels contribute to the tumor escape from immunity by the lack of response to inflammatory activation (endothelial anergy) and by repression of leukocyte adhesion molecule expression. However, tumor vessels can remodel by the association with and integration of pericytes and smooth muscle cells which stabilize these immature vessels resulting in normalization of the vascular structures. This normalization of the tumor vascular bed could improve the efficiency of previously established therapeutic approaches, such as chemo- or radiotherapy by a more homogenous drug and oxygen distribution, and/or by overcoming endothelial anergy. This review highlights the current investigations that take advantage of a proper vascular function for improving cancer therapy with a special focus on the endothelial-immune system interplay.

Proteomics-based insights into mitogen-activated protein kinase inhibitor resistance of cerebral melanoma metastases

Background

MAP kinase inhibitor (MAPKi) therapy for BRAF mutated melanoma is characterized by high response rates but development of drug resistance within a median progression-free survival (PFS) of 9-12 months. Understanding mechanisms of resistance and identifying effective therapeutic alternatives is one of the most important scientific challenges in melanoma. Using proteomics, we want to specifically gain insight into the pathophysiological process of cerebral metastases.

Methods

Cerebral metastases from melanoma patients were initially analyzed by a LC-MS shotgun approach performed on a QExactive HF hybrid quadrupole-orbitrap mass spectrometer. For further validation steps after bioinformatics analysis, a targeted LC-QQQ-MS approach, as well as Western blot, immunohistochemistry and immunocytochemistry was performed.

Results

In this pilot study, we were able to identify 5977 proteins by LC-MS analysis (data are available via ProteomeXchange with identifier PXD007592). Based on PFS, samples were classified into good responders (PFS ≥ 6 months) and poor responders (PFS [Formula: see text] 3 months). By evaluating these proteomic profiles according to gene ontology (GO) terms, KEGG pathways and gene set enrichment analysis (GSEA), we could characterize differences between the two distinct groups. We detected an EMT feature (up-regulation of N-cadherin) as classifier between the two groups, V-type proton ATPases, cell adhesion proteins and several transporter and exchanger proteins to be significantly up-regulated in poor responding patients, whereas good responders showed an immune activation, among other features. We identified class-discriminating proteins based on nearest shrunken centroids, validated and quantified this signature by a targeted approach and could correlate parts of this signature with resistance using the CPL/MUW proteome database and survival of patients by TCGA analysis. We further validated an EMT-like signature as a major discriminator between good and poor responders on primary melanoma cells derived from cerebral metastases. Higher immune activity is demonstrated in patients with good response to MAPKi by immunohistochemical staining of biopsy samples of cerebral melanoma metastases.

Conclusions

Employing proteomic analysis, we confirmed known extra-cerebral resistance mechanisms in the cerebral metastases and further discovered possible brain specific mechanisms of drug efflux, which might serve as treatment targets or as predictive markers for these kinds of metastasis.