IDO is highly expressed in breast cancer and breast cancer-derived circulating microvesicles and associated to aggressive types of tumors by in silico analysis

Experimental and clinical evidence in favour of an effective immune stimulation in ER-positive, endocrine-dependent metastatic breast cancer

In ER+ breast cancer, usually seen as the low immunogenic type, the main mechanisms favouring the immune response or tumour growth and immune evasion in the tumour microenvironment (TME) have been examined. The principal implications of targeting the oestrogen-mediated pathways were also considered. Recent experimental findings point out that anti-oestrogens contribute to the reversion of the immunosuppressive TME. Moreover, some preliminary clinical data with the hormone-immunotherapy association in a metastatic setting support the notion that the reversion of immune suppression in TME is likely favoured by the G0-G1 state induced by anti-oestrogens. Following immune stimulation, the reverted immune suppression allows the boosting of the effector cells of the innate and adaptive immune response. This suggests that ER+ breast cancer is a molecular subtype where a successful active immune manipulation can be attained. If this is confirmed by a prospective multicentre trial, which is expected in light of the provided evidence, the proposed hormone immunotherapy can also be tested in the adjuvant setting. Furthermore, the different rationale suggests a synergistic activity of our proposed immunotherapy with the currently recommended regimen consisting of antioestrogens combined with cyclin kinase inhibitors. Overall, this lays the foundation for a shift in clinical practice within this most prevalent molecular subtype of breast cancer.

Involvement of the kynurenine pathway in breast cancer: updates on clinical research and trials

Breast cancer (BrCa) is the leading cause of cancer incidence and mortality in women worldwide. While BrCa treatment has been shown to be highly successful if detected at an early stage, there are few effective strategies to treat metastatic tumours. Hence, metastasis remains the main cause in most of BrCa deaths, highlighting the need for new approaches in this group of patients. Immunotherapy has been gaining attention as a new treatment for BrCa metastasis and the kynurenine pathway (KP) has been suggested as one of the potential targets. The KP is the major biochemical pathway in tryptophan (TRP) metabolism, catabolising TRP to nicotinamide adenine dinucleotide (NAD+). The KP has been reported to be elevated under inflammatory conditions such as cancers and that its activity suppresses immune surveillance. Dysregulation of the KP has previously been reported implicated in BrCa. This review aims to discuss and provide an update on the current mechanisms involved in KP-mediated immune suppression and cancer growth. Furthermore, we also provide a summary on 58 studies about the involvement of the KP and BrCa and five clinical trials targeting KP enzymes and their outcome.

Managing the immune microenvironment of osteosarcoma: the outlook for osteosarcoma treatment

Osteosarcoma, with poor survival after metastasis, is considered the most common primary bone cancer in adolescents. Notwithstanding the efforts of researchers, its five-year survival rate has only shown limited improvement, suggesting that existing therapeutic strategies are insufficient to meet clinical needs. Notably, immunotherapy has shown certain advantages over traditional tumor treatments in inhibiting metastasis. Therefore, managing the immune microenvironment in osteosarcoma can provide novel and valuable insight into the multifaceted mechanisms underlying the heterogeneity and progression of the disease. Additionally, given the advances in nanomedicine, there exist many advanced nanoplatforms for enhanced osteosarcoma immunotherapy with satisfactory physiochemical characteristics. Here, we review the classification, characteristics, and functions of the key components of the immune microenvironment in osteosarcoma. This review also emphasizes the application, progress, and prospects of osteosarcoma immunotherapy and discusses several nanomedicine-based options to enhance the efficiency of osteosarcoma treatment. Furthermore, we examine the disadvantages of standard treatments and present future perspectives for osteosarcoma immunotherapy.

In Vitro Evidence of Differential Immunoregulatory Response between MDA-MB-231 and BT-474 Breast Cancer Cells Induced by Bone Marrow-Derived Mesenchymal Stromal Cells Conditioned Medium

Inside tumors, cancer cells display several mechanisms to create an immunosuppressive environment. On the other hand, by migration processes, mesenchymal stromal cells (MSCs) can be recruited by different cancer tumor types from tissues as distant as bone marrow and contribute to tumor pathogenesis. However, the impact of the immunoregulatory role of MSCs associated with the aggressiveness of breast cancer cells by soluble molecules has not been fully elucidated. Therefore, this in vitro work aimed to study the effect of the conditioned medium of human bone marrow-derived-MSCs (hBM-MSC-cm) on the immunoregulatory capability of MDA-MB-231 and BT-474 breast cancer cells. The hBM-MSC-cm on MDA-MB-231 cells induced the overexpression of TGF-β, IDO, and IL-10 genes. Additionally, immunoregulation assays of mononuclear cells (MNCs) in co-culture with MDA-MB-231 and hBM-MSC-cm decreased lymphocyte proliferation, and increased proteins IL-10, TGF-β, and IDO while also reducing TNF levels, shooting the proportion of regulatory T cells. Conversely, the hBM-MSC-cm did not affect the immunomodulatory capacity of BT-474 cells. Thus, a differential immunoregulatory effect was observed between both representative breast cancer cell lines from different origins. Thus, understanding the immune response in a broader tumor context could help to design therapeutic strategies based on the aggressive behavior of tumor cells.

Expression of immune checkpoints (PD-L1 and IDO) and tumour-infiltrating lymphocytes in breast cancer

Background

Breast cancer (BC) has become the most common cancer globally in 2020 as well as in the United Arab Emirates. The breast tumor microenvironment is composed of various immune cell types, including lymphocytes. Tumour-infiltrating lymphocytes (TILs) play a crucial role in tumor eradication and progression. Further, immune checkpoint markers such as programmed death receptor ligand 1 (PD-L1) and indoleamine-2,3-dioxygenase (IDO) have been associated with tumor evasion from the immune system. In this study, we aimed to explore the status of TILs, PD-L1 and IDO as well as to investigate their association with the clinicopathological parameters.

Materials and methods

A total of 59 patients diagnosed with primary infiltrating BC were selected, after which tissue sections were stained to identify TILs along with immunohistochemical staining of PD-L1 and IDO. Moreover, in-silico tools were used to assess the expression of PD-L1, IDO and CD3ε in various molecular subtypes of BC.

Results

It was found that the percentage of TILs correlated with estrogen receptor (ER) and progesterone receptor (PR) expression. This was supported by the finding that most of the triple-negative breast cancer (TNBC) cases belonged to the group with a high percentage of TILs (h-TILs). Similarly, the expression of PD-L1 and IDO was correlated with the ER and PR, whereas TNBC cases showed a high expression of PD-L1 and IDO. This goes in line with the in-silico findings where the TNBC group showed the highest expression of PD-L1 and IDO as well as the T cell marker CD3ε.

Conclusion

This study highlighted a possible link between the immunosuppressive markers PD-L1 and IDO with TILs density in the BC microenvironment.

Potential role of tryptophan catabolism in cancer-related cognitive impairment

Oncology may be the most rapidly expanding field in medicine, with several innovative diagnostic and therapeutic procedures appearing daily. Advances in oncology have improved the survival rate for patients with cancer and promoting quality of life is now one of the goals in the care of these patients. Patients face a variety of disease- and treatment-related side effects, including anorexia, nausea, vomiting, recurring infections, and sleep difficulties. Cancer-related cognitive impairment (CRCI) is an overlooked clinical condition found in oncologic practice, particularly in patients with breast cancer. Although several potential mechanisms for CRCI have been hypothesized, to our knowledge, the exact mechanism is still unknown. Alterations in the tryptophan kynurenine pathway have been shown to impair cognitive skills in several mental illnesses. However, its possible function in CRCI has yet to be investigated. The aim of this was to examine the possible interactions between tryptophan catabolism and CRCI.

Extracellular vesicle-mediated transport: Reprogramming a tumor microenvironment conducive with breast cancer progression and metastasis

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Extracellular vesicles’ (EVs) role in breast tumor microenvironment and pre-metastatic niche development.

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Breast cancer EV-mediated transmission of pro-metastatic and drug-resistant phenotypes.

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Precision medicine with EVs as biomarkers and delivery vehicles for drug and anticancer genetic material.

Breast cancer metastatic progression to critical secondary sites is the second leading cause of cancer-related mortality in women. While existing therapies are highly effective in combating primary tumors, metastatic disease is generally deemed incurable with a median survival of only 2, 3 years. Extensive efforts have focused on identifying metastatic contributory targets for therapeutic antagonism and prevention to improve patient survivability. Excessive breast cancer release of extracellular vesicles (EVs), whose contents stimulate a metastatic phenotype, represents a promising target. Complex breast cancer intercellular communication networks are based on EV transport and transference of molecular information is in bulk resulting in complete reprogramming events within recipient cells. Other breast cancer cells can acquire aggressive phenotypes, endothelial cells can be induced to undergo tubule formation, and immune cells can be neutralized. Recent advancements continue to implicate the critical role EVs play in cultivating a tumor microenvironment tailored to cancer proliferation, metastasis, immune evasion, and conference of drug resistance. This literature review serves to frame the role of EV transport in breast cancer progression and metastasis. The following five sections will be addressed: (1) Intercellular communication in developing a tumor microenvironment & pre-metastatic niche. (2) Induction of the epithelial-to-mesenchymal transition (EMT). (3). Immune suppression & evasion. (4) Transmission of drug resistance mechanisms. (5) Precision medicine: clinical applications of EVs.

Folate receptor-mediated delivery of 1-MDT-loaded mesoporous silica magnetic nanoparticles to target breast cancer cells

Aims: The efficiency of mesoporous silica magnetic nanoparticles (MSMNP) as a targeted drug-delivery system was investigated. Methods: The superparamagnetic iron oxide nanoparticles (NP) were synthesized, coated with mesoporous silica and conjugated with polyethylene glycol and methotrexate. Next, 1-methyl-D-tryptophan was loaded into the prepared nanosystems (NS). They were characterized using transmission electron microscopy, scanning electron microscopy, dynamic light scattering, vibrating sample magnetometer, x-ray powder diffraction, Fourier transform-infrared spectroscopy and the Brunauer-Emmett-Teller method and their biological impacts on breast cancer cells were evaluated. Results: The prepared NSs displayed suitable properties and showed enhanced internalization by folate-receptor-expressing cells, exerting efficient cytotoxicity, which was further enhanced by the near-infrared radiation irradiation. Conclusion: On the basis of our findings, the engineered NS is a promising multifunctional nanomedicine/theranostic for solid tumors.

Review of 10 years of research on breast cancer patients: Focus on indoleamine 2,3-dioxygenase

Therapeutic manipulation of the immune system in cancer has been an extensive area of research in the field of oncoimmunology. Immunosuppression regulates antitumour immune responses. An immunosuppressive enzyme, indoleamine 2,3-dioxygenase (IDO) mediates tumour immune escape in various malignancies including breast cancer. IDO upregulation in breast cancer cells may lead to the recruitment of regulatory T (T-regs) cells into the tumour microenvironment, thus inhibiting local immune responses and promoting metastasis. Immunosuppression induced by myeloid derived suppressor cells activated in an IDO-dependent manner may enhance the possibility of immune evasion in breast cancer. IDO overexpression has independent prognostic significance in a subtype of breast cancer of emerging interest, basal-like breast carcinoma. IDO inhibitors as adjuvant therapeutic agents may have clinical implications in breast cancer. This review proposes future prospects of IDO not only as a therapeutic target but also as a valuable prognostic marker for breast cancer.

Reliable chromatographic assay for measuring of indoleamine 2,3-dioxygenase 1 (IDO1) activity in human cancer cells

The kynurenine pathway is the major tryptophan degradation routes generating bioactive compounds important in physiology and diseases. Depending on cell type it is initiated enzymatically by tryptophan-2,3-dioxygenase (TDO) or indoleamine-2,3-dioxygenase 1 and 2 (IDO1 and IDO2) to yield N-formylkynurenine as the precursor of further metabolites. Herein, we describe an accurate high-pressure liquid chromatography coupled with a diode array detector (HPLC-DAD) method to serve for IDO1 activity determination in human cancer cells cultured in vitro. Enzymatic activity was expressed as the rate of ʟ-kynurenine generation by 1 mg of proteins obtained from cancer cells. Our approach shows the limit of detection and limit of quantification at 12.9 and 43.0 nM Kyn, respectively. Applicability of this method was demonstrated in different cells (ovarian and breast cancer)exposed to various conditions and has successfully passed the validation process. This approach presents a useful model to study the role of kynurenine pathway in cancer biology.

The roles of tumor-derived exosomes in altered differentiation, maturation and function of dendritic cells

Tumor-derived exosomes (TDEs) have been shown to impede anti-tumor immune responses via their immunosuppressive cargo. Since dendritic cells (DCs) are the key mediators of priming and maintenance of T cell-mediated responses; thus it is logical that the exosomes released by tumor cells can exert a dominant influence on DCs biology. This paper intends to provide a mechanistic insight into the TDEs-mediated DCs abnormalities in the tumor context. More importantly, we discuss extensively how tumor exosomes induce subversion of DCs differentiation, maturation and function in separate sections. We also briefly describe the importance of TDEs at therapeutic level to help guide future treatment options, in particular DC-based vaccination strategy, and review advances in the design and discovery of exosome inhibitors. Understanding the exosomal content and the pathways by which TDEs are responsible for immune evasion may help to revise treatment rationales and devise novel therapeutic approaches to overcome the hurdles in cancer treatment.

Metabolic Rewiring in Radiation Oncology Toward Improving the Therapeutic Ratio

To meet the anabolic demands of the proliferative potential of tumor cells, malignant cells tend to rewire their metabolic pathways. Although different types of malignant cells share this phenomenon, there is a large intracellular variability how these metabolic patterns are altered. Fortunately, differences in metabolic patterns between normal tissue and malignant cells can be exploited to increase the therapeutic ratio. Modulation of cellular metabolism to improve treatment outcome is an emerging field proposing a variety of promising strategies in primary tumor and metastatic lesion treatment. These strategies, capable of either sensitizing or protecting tissues, target either tumor or normal tissue and are often focused on modulating of tissue oxygenation, hypoxia-inducible factor (HIF) stabilization, glucose metabolism, mitochondrial function and the redox balance. Several compounds or therapies are still in under (pre-)clinical development, while others are already used in clinical practice. Here, we describe different strategies from bench to bedside to optimize the therapeutic ratio through modulation of the cellular metabolism. This review gives an overview of the current state on development and the mechanism of action of modulators affecting cellular metabolism with the aim to improve the radiotherapy response on tumors or to protect the normal tissue and therefore contribute to an improved therapeutic ratio.

High PD-L1/IDO-2 and PD-L2/IDO-1 Co-Expression Levels Are Associated with Worse Overall Survival in Resected Non-Small Cell Lung Cancer Patients

Programmed death ligand 1 (PD-L1) expression is a predictive biomarker of the success of PD-1/PD-L1 inhibitor therapy for patients with advanced non-small cell lung cancer (NSCLC) but its role as a prognostic marker for early-stage resectable NSCLC remains unclear. We studied gene expression levels of immune-related genes PD-1, PD-L1, PD-L2, IDO-1, IDO-2 and INFγ in tumor tissue of surgically resected NSCLC and correlated the finding with clinicopathological features and patient outcomes. A total of 191 consecutive early-stage NSCLC patients who underwent curative pulmonary resection were studied. The mRNA expression levels of immune-related genes were evaluated by quantitative reverse transcription polymerase chain reaction (qRT-PCR) using RT² Profiler PCR Arrays (Qiagen). PD-1, PD-L2 and IDO-2 gene expression levels were significantly higher in patients with squamous histology (p = 0.001, p = 0.021 and p < 0.001; respectively). PD-1, PD-L1 and IDO-2 gene expression levels were significantly higher in patients with higher stage (p = 0.005, p = 0.048 and p = 0.002, respectively). The univariate analysis for recurrence-free survival (RFS) and overall survival (OS) showed that patients with higher levels of three-genes (PD-L1/PD-L2/INFγ) (hazard ratio (HR)) 1.90 (95% confidence interval (CI), 1.13–3.21), p = 0.015) were associated with a worse RFS, while patients with higher levels of both genes (PD-L1/IDO-2) or (PD-L2/IDO-1) were associated with a worse OS (HR 1.63 95% CI, 1.06–2.51, p = 0.024; HR 1.54 95% CI, 1.02–2.33, p = 0.04; respectively). The multivariate interaction model adjusted for histology and stage confirmed that higher levels of three genes (PD-L1/PD-L2/INFγ) were significantly associated with worse RFS (HR 1.98, p = 0.031) and higher levels of both genes (PD-L1/IDO-2) and (PD-L2/IDO-1) with worse OS (HR 1.98, p = 0.042, HR 1.92, p = 0.022). PD-L1/IDO-2 and PD-L2/IDO-1 co-expression high levels are independent negative prognostic factors for survival in early NSCLC. These features may have important implications for future immune-checkpoint therapeutic approaches.

The footprint of kynurenine pathway in every cancer: a new target for chemotherapy

Treatment of cancers has always been a challenge for physicians. Typically, several groups of anti-cancer medications are needed for effective management of an invasive and metastatic cancer. Recently, therapeutic potentiation of immune system markedly improved treatment of cancers. Kynurenine pathway has an interwoven correlation with immune system. Kynurenine promotes T Reg (regulatory) differentiation, which leads to increased production of anti-inflammatory cytokines and suppression of cytotoxic activity of T cells. Overactivation of kynurenine pathway in cancers provides an immunologically susceptible microenvironment for mutant cells to survive and invade surrounding tissues. Interestingly, kynurenine pathway vigorously interacts with other molecular pathways involved in tumorigenesis. For instance, kynurenine pathway interacts with phospoinosisitide-3 kinase (PI3K), extracellular signal-regulated kinase (ERK), Wnt/β-catenin, P53, bridging integrator 1 (BIN-1), cyclooxygenase 2 (COX-2), cyclin-dependent kinase (CDK) and collagen type XII α1 chain (COL12A1). Overactivation of kynurenine pathway, particularly overactivation of indoleamine 2,3-dioxygenase (IDO) predicts poor prognosis of several cancers such as gastrointestinal cancers, gynecological cancers, hematologic malignancies, breast cancer, lung cancer, glioma, melanoma, prostate cancer and pancreatic cancer. Furthermore, kynurenine increases the invasion, metastasis and chemoresistance of cancer cells. Recently, IDO inhibitors entered clinical trials and successfully passed their safety tests and showed promising therapeutic efficacy for cancers such as melanoma, brain cancer, renal cell carcinoma, prostate cancer and pancreatic cancer. However, a phase III trial of epacadostat, an IDO inhibitor, could not increase the efficacy of treatment with pembrolizumab for melanoma. In this review the expanding knowledge towards kynurenine pathway and its application in each cancer is discussed separately.

Immunotherapy for osteosarcoma: Fundamental mechanism, rationale, and recent breakthroughs

Osteosarcoma (OS) is the most common primary malignancy of the bone and has a high propensity for local invasion and metastasis. Although combining surgery with chemotherapy has immensely improved the outcomes of osteosarcoma patients, the prognosis of metastatic or recurrent osteosarcomas is still unsatisfactory. Immunotherapy has proven to be a promising therapeutic strategy against human malignancies and improved understanding of the immune response to OS, and biomarker development has increased the number of patients who benefit from immunotherapies in recent years. Here, we review recent advances in immunotherapy in osteosarcoma and discuss the mechanisms and status of immunotherapies in both preclinical and clinical trials as well as future therapies on the horizon. These advances may pave the way for novel treatments requisite for patients with osteosarcoma in need of new therapies.

Large Extracellular Vesicles-A New Frontier of Liquid Biopsy in Oncology

Extracellular Vesicles (EVs) are emerging as pivotal elements in cancer. Many studies have focused on the role of Small- (S)-EVs but in recent years Large-(L)-EVs have progressively gained increasing interest due to their peculiar content and functions. Tumor-derived L-EVs carry a lot of oncogenic proteins, nucleic acids and lipids to recipient cells and are involved in the reshaping of the tumor microenvironment as well as in the metabolic rewiring and the promotion of the pro-metastatic attitude of cancer cells. Several techniques have been developed for the isolation of L-EVs and commercial kits are also available for efficient and easy recovery of these vesicles. Also, the improvement in DNA sequencing and “omics sciences” profoundly changed the way to analyze and explore the molecular content of L-EVs, thus providing novel and potentially useful cancer biomarkers. Herein, we review the most recent findings concerning the role of L-EVs in cancer and discuss their possible use in oncology as “liquid biopsy” tools as compared to the other classes of EVs.

Role of natural products in breast cancer related symptomology: Targeting chronic inflammation

Breast cancer is the most common cancer in women worldwide. There have been many advancements in the treatment of breast cancer leading to an increased population of patients living with this disease. Accumulating evidence suggests that cancer diagnosis and aftermath experienced stress could not only affect the quality of life of cancer patients, but it could also influence their disease outcome. The magnitude of stress experienced by breast cancer patients is often compared to the post-traumatic stress disorder-like symptoms suggested to be mediated by the chronic inflammation including NF-κB, AKt, p53 and other inflammatory pathways. Here, we describe the symptomology of PTSD-like symptoms in breast cancer patients and argue that they may in fact be caused by or maintained through aspects of chronic inflammation mediated by the pro-inflammatory markers. Evidence exists that natural products that might attenuate or lessen the effects of chronic inflammation abound in the diet. We summarize some possible agents that might abate the genesis of symptoms experienced by breast cancer patients while mitigating the effect of inflammation.

Indoleamine 2,3-Dioxygenase-1 Expression in Adrenocortical Carcinoma

BACKGROUND

Indoleamine 2,3-dioxygenase 1 (IDO-1) is overexpressed in many human carcinomas and a successful target for therapy in mouse models. Prognosis of patients with advanced adrenocortical carcinoma (ACC) is poor due to the lack of effective treatments, and new therapies are therefore needed. Herein, we investigate whether IDO-1 is expressed in human ACC tissues.

METHODS

53 tissue samples from patients with ACC, adrenal adenoma (AA), adrenocortical tumors (ACTs), and normal adrenal were identified. Immunohistochemistry was performed on formalin-fixed, paraffin-embedded slides for IDO-1. Samples were scored for cytoplasmic staining as per intensity and the percent of positive cells and for stromal staining by percent of positive cells. Tumor characteristics, PD-L1, PDL-2, and CD-8+ T-lymphocyte expression were also determined.

RESULTS

Samples from 32 ACC, 3 ACT, 15 AA, and 3 normal adrenal were analyzed. IDO-1 was expressed in tumor tissue in 22 of 32 ACC samples, compared with 8 of 15 AA sample (P = 0.344). IDO-1 expression was significantly increased in stromal tissue of ACC samples (16 of 33), compared with AA samples (0 of 15) (P = 0.001). IDO-1 expression in ACC and AA samples was associated with PD-L2 expression (P = 0.034). IDO-1 expression in ACC stromal tissue was associated with CD8+ T-lymphocyte infiltration (P = 0.028).

CONCLUSIONS

IDO-1 is expressed in a majority of ACC samples. Its expression in tumor tissue is associated with PD-L2 expression, and expression in stroma is associated with CD8+ cell infiltration. IDO-1 inhibition, alone or in combination with PD-1 inhibition, could therefore be an interesting target in treatment of ACC.

The Tumor Microenvironment: A Milieu Hindering and Obstructing Antitumor Immune Responses

The success of cancer immunotherapy relies on the knowledge of the tumor microenvironment and the immune evasion mechanisms in which the tumor, stroma, and infiltrating immune cells function in a complex network. The potential barriers that profoundly challenge the overall clinical outcome of promising therapies need to be fully identified and counteracted. Although cancer immunotherapy has increasingly been applied, we are far from understanding how to utilize different strategies in the best way and how to combine therapeutic options to optimize clinical benefit. This review intends to give a contemporary and detailed overview of the different roles of immune cells, exosomes, and molecules acting in the tumor microenvironment and how they relate to immune activation and escape. Further, current and novel immunotherapeutic options will be discussed.

Mechanism of tumor cells escaping from immune surveillance of NK cells

Natural killer (NK) cells play an important role in anti-tumor and anti-infection, and perform their immune surveillance function in various ways. However, no matter what kind of cancer, the functional activity of NK cells in the tumor microenvironment (TME) is suppressed. Understanding the relationship between tumor cells and NK cells is very critical for tumor immunotherapy. This review discusses the mechanism of tumor cells escaping the immune surveillance of NK cells. These include a variety of factors that inhibit the activity of NK cells, an imbalance of activating receptors and inhibiting receptors on NK cells, abnormal binding of receptors and ligands, cross-talk of surrounding cell groups and NK cells in the TME, and other factors that affect NK cell activity. An understanding of these factors is necessary to provide new treatment strategies for tumor immunotherapy.

Inflammation-Induced Tryptophan Breakdown is Related With Anemia, Fatigue, and Depression in Cancer

Many patients with cancer suffer from anemia, depression, and an impaired quality of life (QoL). These patients often also show decreased plasma tryptophan levels and increased kynurenine concentrations in parallel with elevated concentrations of Th1 type immune activation marker neopterin. In the course of anti-tumor immune response, the pro-inflammatory cytokine interferon gamma (IFN-γ) induces both, the enzyme indoleamine 2,3-dioxygenase (IDO) to degrade tryptophan and the enzyme GTP-cyclohydrolase I to form neopterin. High neopterin concentrations as well as an increased kynurenine to tryptophan ratio (Kyn/Trp) in the blood of cancer patients are predictive for a worse outcome. Inflammation-mediated tryptophan catabolism along the kynurenine pathway is related to fatigue and anemia as well as to depression and a decreased QoL in patients with solid tumors. In fact, enhanced tryptophan breakdown might greatly contribute to the development of anemia, fatigue, and depression in cancer patients. IDO activation and stimulation of the kynurenine pathway exert immune regulatory mechanisms, which may impair anti-tumor immune responses. In addition, tumor cells can degrade tryptophan to weaken immune responses directed against them. High IDO expression in the tumor tissue is associated with a poor prognosis of patients. The efficiency of IDO-inhibitors to inhibit cancer progression is currently tested in combination with established chemotherapies and with immune checkpoint inhibitors. Inflammation-mediated tryptophan catabolism and its possible influence on the development and persistence of anemia, fatigue, and depression in cancer patients are discussed.

Inflammation in cancer and depression: a starring role for the kynurenine pathway

Depression is a common comorbidity in cancer cases, but this is not only due to the emotional distress of having a life-threatening disease. A common biological mechanism, involving a dysregulated immune system, seems to underpin this comorbidity. In particular, the activation of the kynurenine pathway of tryptophan degradation due to inflammation may play a key role in the development and persistence of both diseases. As a consequence, targeting enzymes involved in this pathway offers a unique opportunity to develop new strategies to treat cancer and depression at once. In this work, we provide a systematic review of the evidence up to date on the kynurenine pathway role in linking depression and cancer and on clinical implications of this evidence. In particular, complications due to chemotherapy are discussed, as well as the potential antidepressant efficacy of novel immunotherapies for cancer.

The Complex Interaction between the Tumor Micro-Environment and Immune Checkpoints in Breast Cancer

The progression of breast cancer and its association with clinical outcome and treatment remain largely unexplored. Accumulating data has highlighted the interaction between cells of the immune system and the tumor microenvironment in cancer progression, and although studies have identified multiple facets of cancer progression within the development of the tumor microenvironment (TME) and its constituents, there is lack of research into the associations between breast cancer subtype and staging. Current literature has provided insight into the cells and pathways associated with breast cancer progression through expression analysis. However, there is lack of co-expression studies between immune pathways and cells of the TME that form pro-tumorigenic relationships contributing to immune-evasion. We focus on the immune checkpoint and TME elements that influence cancer progression, particularly studies in molecular subtypes of breast cancer.

Beyond PD-1/PD-L1 Inhibition: What the Future Holds for Breast Cancer Immunotherapy

Cancer immunotherapy has altered the management of human malignancies, improving outcomes in an expanding list of diseases. Breast cancer - presumably due to its perceived low immunogenicity - is a late addition to this list. Furthermore, most of the focus has been on the triple negative subtype because of its higher tumor mutational load and lymphocyte-enriched stroma, although emerging data show promise on the other breast cancer subtypes as well. To this point the clinical use of immunotherapy is limited to the inhibition of two immune checkpoints, Programmed Cell Death Protein 1 (PD-1) and Cytotoxic T-lymphocyte-associated Protein 4 (CTLA-4). Consistent with the complexity of the regulation of the tumor - host interactions and their lack of reliance on a single regulatory pathway, combinatory approaches have shown improved efficacy albeit at the cost of increased toxicity. Beyond those two checkpoints though, a large number of co-stimulatory or co-inhibitory molecules play major roles on tumor evasion from immunosurveillance. These molecules likely represent future targets of immunotherapy provided that the promise shown in early data is translated into improved patient survival in randomized trials. The biological role, prognostic and predictive implications regarding breast cancer and early clinical efforts on exploiting these immune-related therapeutic targets are herein reviewed.

Immunotherapy in breast cancer: Current status and future directions

Breast cancer, one of the leading causes of death in women in the United States, challenges therapeutic success in patients due to tumor heterogeneity, treatment resistance, metastasis and disease recurrence. Knowledge of immune system involvement in normal breast development and breast cancer has led to extensive research into the immune landscape of breast cancer and multiple immunotherapy clinical trials in breast cancer patients. However, poor immunogenicity and T-cell infiltration along with heightened immunosuppression in the tumor microenvironment have been identified as potential challenges to the success of immunotherapy in breast cancer. Oncodrivers, owing to their enhanced expression and stimulation of tumor cell proliferation and survival, present an excellent choice for targeted immunotherapy development in breast cancer. Loss of anti-tumor immune response specific to oncodrivers has been reported in breast cancer patients as well. Dendritic cell vaccines have been tested for their efficacy in generating anti-tumor T-cell response against specific tumor-associated antigens and oncodrivers and have shown improved survival outcome in patients. Here, we review the current status of immunotherapy in breast cancer, focusing on dendritic cell vaccines and their therapeutic application in breast cancer. We further discuss future directions of breast cancer immunotherapy and potential combination strategies involving dendritic cell vaccines and existing chemotherapeutics for improved efficacy and better survival outcome in breast cancer.

IDO expression in breast cancer: an assessment of 281 primary and metastatic cases with comparison to PD-L1

The immune inhibitory enzyme indoleamine 2,3-dioxygenase (IDO) has been associated with immune evasion in numerous malignancies and may mark these cancers as susceptible to anti-IDO therapies. We herein address IDO expression in breast cancers, examine the relationship between IDO and PD-L1, and investigate IDO fidelity across breast cancer primaries and metastases. IDO and PD-L1 expression was assessed in tissue microarrays containing 242 invasive primary breast cancers, 20 nodal metastases, and 19 distant metastases. IDO and PD-L1 were scored by extent in the tumor cells and immune infiltrate. Tumor IDO staining was seen in 14% of primaries including 38% of triple-negative cancers. IDO immune cell staining was seen in 14% of primaries and 29% of triple-negative cancers. Tumoral IDO and PD-L1 co-expression was seen in 8% of primaries, including 70% of tumoral PD-L1-positive cases. Immune IDO and PD-L1 co-expression was identified in 14% of primaries, including 48% of immune PD-L1-positive cases. Tumoral and immune cell IDO was conserved in 94% of matched primary/metastasis. In summary, IDO expression is common among high-grade, triple-negative breast cancers and is frequently associated with PD-L1 co-expression, suggesting that IDO might be a mechanism of anti-PD-1/PD-L1 immunotherapy resistance and that dual therapy may be of utility. Tumoral and immune cell IDO expression shows fidelity between primary and metastatic sites in treatment-naïve cancers, arguing against IDO as an independent driver for metastatic spread. Clinical trials are needed to assess the efficacy of IDO inhibition relative to IDO expression, as well as its possible role in combination with anti-PD-1/PD-L1 immunotherapy.

Study of the tumor microenvironment during breast cancer progression

Background

Different cells and mediators in the tumor microenvironment play important roles in the progression of breast cancer. The aim of this study was to determine the composition of the microenvironment during tumor progression in order to discover new related biomarkers and potentials for targeted therapy.

Methods

In this study, breast cancer biopsies from four different stages, and control breast biopsies were collected. Then, the mRNA expression of several markers related to different CD4⁺ T cell subsets including regulatory T cells (Treg), T helper (Th) type 1, 2 and 17 were determined. In addition, we investigated the expression of two inflammatory cytokines (TNF-α and IL-6) and inflammatory mediators including FASL, IDO, SOCS1, VEGF, and CCR7.

Results

The results showed that the expression of Th1 and Th17 genes was decreased in tumor tissues compared to control tissues. In addition, we found that the gene expression related to these two cell subsets decreased during cancer progression. Moreover, the expression level of TNF-α increased with tumor progression.

Conclusion

We conclude that the expression of genes related to immune response and inflammation is different between tumor tissues and control tissues. In addition, this difference was perpetuated through the different stages of cancer.

Immunotherapy for breast cancer: past, present, and future

Immunotherapy has shown promise in many solid tumors including melanoma and non-small cell lung cancer with an evolving role in breast cancer. Immunotherapy encompasses a wide range of therapies including immune checkpoint inhibition, monoclonal antibodies, bispecific antibodies, vaccinations, antibody-drug conjugates, and identifying other emerging interventions targeting the tumor microenvironment. Increasing efficacy of these treatments in breast cancer patients requires identification of better biomarkers to guide patient selection; recognizing when to initiate these therapies in multi-modality treatment plans; establishing novel assays to monitor immune-mediated responses; and creating combined systemic therapy options incorporating conventional treatments such as chemotherapy and endocrine therapy. This review will focus on the current role and future directions of many of these immunotherapies in breast cancer, as well as highlighting clinical trials that are investigating several of these active issues.

Objective measurement and clinical significance of IDO1 protein in hormone receptor-positive breast cancer

Background

Immunostimulatory therapies targeting immune-suppressive pathways produce durable responses in advanced solid tumors. Indoleamine 2,3-dioxygenase (IDO) is the rate-limiting oxidoreductase that catalyzes the degradation of tryptophan to kynurenine. IDO induces immune tolerance by downregulating CD8+ and effector CD4+ T cell responses. IDO1, the most active isoform, is expressed in diverse tumor types and can be targeted using small molecule inhibitors. We used an objective, in situ assay to measure IDO1 in a collection of hormone receptor-positive breast cancers (HR+ BC).

Methods

IDO1 protein was measured using quantitative immunofluorescence in 362 stage I-III HR+ BC represented in tissue microarrays. IDO1 levels were determined in the tumor and stroma, and stratified using median cut-point. Associations between IDO1, clinico-pathological features and CD3+, CD8+, CD20+ and FOXP3 tumor-infiltrating lymphocytes were examined using χ² and Mann-Whitney tests. Survival was studied using Kaplan-Meier estimator and a proportional hazards model. All tests were two-sided.

Results

IDO1 protein was observed in 76.2% of HR+ BC. There was no association between IDO1 and major clinico-pathological characteristics. Increased IDO1 correlated with decreased CD20+ infiltration (P = 0.0004) but not with CD3+, CD8+ or FOXP3 levels. Elevated IDO1 expression was associated with worse 20-year overall survival (log-rank P = 0.02, HR = 1.39, 95% C.I.: 1.05-1.82). IDO1 scores were independently associated with outcome in multivariable analysis.

Conclusions

IDO1 protein is expressed in the majority of HR+ BC and is an independent negative prognostic marker. Additionally, IDO1 expression is negatively associated with tumor B-cell infiltration. Measurement of IDO1 has the potential to identify a population that might derive benefit from IDO1 blockade.

Electronic supplementary material

The online version of this article (10.1186/s40425-017-0285-7) contains supplementary material, which is available to authorized users.

A novel immunohistochemical score to predict early mortality in acute myeloid leukemia patients based on indoleamine 2,3 dioxygenase expression

Indoleamine 2,3 dioxygenase-1 (IDO-1) is an enzyme in the kynurenine pathway which augments tumor-induced immune tolerance. Previous studies in childhood acute myeloid leukemia (AML) have shown a negative correlation of IDO-1 mRNA expression with outcomes. The aim of our study was to develop a practical and objective immunohistochemical technique to quantify IDO-1 expression on diagnostic bone marrow biopsies of AML patients in order to facilitate its use in routine clinical practice. IDO-1 mRNA was extracted from diagnostic bone marrow specimens from 29 AML patients. IDO-1 protein expression was assessed in 40 cases via immunohistochemistry and quantified by a novel ‘composite IDO-1 score’. In a univariate analysis, higher age (p = 0.0018), male gender (p = 0.019), high risk cytogenetics (p = 0.002), higher IDO-1 mRNA (p = 0.005), higher composite IDO-1 score (p < 0.0001) and not undergoing allogeneic stem cell transplant (SCT, p = 0.0005) predicted poor overall survival. In a multivariate model that included the aforementioned variables, higher composite IDO-1 score (p = 0.007) and not undergoing allogeneic SCT (p = 0.007) was found to significantly predict poor outcomes. Further, patients who failed induction had higher composite IDO-1 score (p = 0.01). In conclusion, ‘composite IDO-1 score’ is a prognostic tool that can help identify a certain subset of AML patients with ‘early mortality’. This unique subset of patients can potentially benefit from specific IDO-1 inhibitor therapy, currently in clinical trials.

Major Developments in the Design of Inhibitors along the Kynurenine Pathway

Disrupted kynurenine pathway (KP) metabolism has been implicated in the progression of neurodegenerative disease, psychiatric disorders and cancer. Modulation of enzyme activity along this pathway may therefore offer potential new therapeutic strategies for these conditions. Considering their prominent positions in the KP, the enzymes indoleamine 2,3-dioxygenase, kynurenine 3-monooxygenase and kynurenine aminotransferase, appear the most attractive targets. Already, increasing interest in this pathway has led to the identification of a number of potent and selective enzyme inhibitors with promising pre-clinical data and the elucidation of several enzyme crystal structures provides scope to rationalize the molecular mechanisms of inhibitor activity. The field seems poised to yield one or more inhibitors that should find clinical utility.

Expression and Prognostic Value of Indoleamine 2,3-dioxygenase in Pancreatic Cancer

Background:

Indoleamine 2,3-dioxygenase (IDO), an enzyme for tryptophan metabolism through the kynurenine pathway, exhibits an immunosuppressive effect and induces immune tolerance in tumor cells. The effects of IDO on pancreatic cancer are poorly understood. This study aimed to investigate the expression and prognostic significance of IDO in pancreatic cancer.

Methods:

We evaluated the protein expression of IDO in PANC-1, CFPAC-1, and BxPC-3 cell lines with or without 48 h treatment by 500 U/ml interferon-γ (IFN-γ). We performed immunohistochemical staining and Western blot analysis for IDO expression in both pancreatic cancer and normal pancreas tissues obtained from Chinese PLA General Hospital from July 2012 to December 2013. Survival analysis was performed to correlate IDO expression and histopathologic parameters with overall survival. The Kaplan-Meier method and Cox proportional hazards regression model were conducted.

Results:

PANC-1, CFPAC-1, and BxPC-3 cell lines expressed IDO at the protein level, and the relative expression amount increased after stimulation with 500 U/ml IFN-γ. Immunohistochemical analysis results revealed that high IDO expression was observed in 59% of pancreatic adenocarcinoma tissues. Compared with normal pancreatic tissues, pancreatic adenocarcinoma showed significantly higher IDO expression levels, especially among patients with high tumor node metastasis (TNM) stages (χ² = 4.550, P = 0.030), poor histological differentiation (χ² = 5.690, P = 0.017), and lymph node metastasis (χ² = 4.340 P = 0.037). Kaplan-Meier survival curves showed that high IDO expression was correlated with low survival rates (hazard ratio [HR] = 0.49 P = 0.009). Multivariate analysis using Cox proportional hazards model indicated that lymph node metastasis (HR = 0.35 P = 0.010) and IDO expression (HR = 0.42 P = 0.020) were two independent prognostic predictors of pancreatic adenocarcinoma.

Conclusions:

The study confirmed that high IDO expression in pancreatic adenocarcinoma was related to poor prognosis of patients. These findings provided evidence that IDO was involved in pancreatic adenocarcinoma progression and might serve as a relevant therapeutic target.

P53 prevent tumor invasion and metastasis by down-regulating IDO in lung cancer

In present study, we are to clear demonstrate the genetic evidence of IDO signaling's impact on invasion and metastasis in lung cancer. Here we examined IDO1 expression levels in non-small cell lung cancer (NSCLC) patients (64) tumor/normal pairs underwent RT-PCR and comprehensive histological, immunohistochemica and clinical analysis. The NSCLC cells stably expressing IDO1 was analyzed for migration and invasion assays and the regulatory mechanism in vitro and metastasis assays in vivo. As results, we reported that IDO1 expression increased by more than 3.2-fold in lung cancer compared with their corresponding non-tumor tissues, and the up-regulation of IDO1 is significantly correlated to TNM stage and lymph node-metastasis. The over-expression of IDO1 significantly encouraged the metastasis and invasion of lung cancer cells, and IDO1 could promote metastasis formation in vivo. Furthermore, we further found that p53 could attenuate IDO signaling in lung cancer cell migration partly. In conclusion, these results demonstrate that the IDO signaling's impact on invasion and metastasis and the suppressive effect of p53 on IDO1 in lung cancer, present one novel therapeutic strategy for early metastatic lung cancer in clinical.

Mechanisms governing metastatic dormancy in breast cancer

Breast cancer is a systemic disease characterized by early dissemination of tumor cells to distant organs. In this foreign environment, tumor cells may stay in a dormant state as single cells or as micrometastases for many years before growing out into a macrometastatic lesion. As metastasis is the primary cause for breast cancer-related death, it is important to understand the mechanisms underlying the maintenance of dormancy and dormancy escape to find druggable targets to eradicate metastatic tumor cells. Metastatic dormancy is regulated by complex interactions between tumor cells and the local microenvironment. In addition, cancer-directed immunity and systemic instigation play a crucial role.

Suppression of indoleamine-2,3-dioxygenase 1 expression by promoter hypermethylation in ER-positive breast cancer

Kynurenine formation by tryptophan-catabolic indoleamine-2,3-dioxygenase 1 (IDO1) plays a key role in tumor immune evasion and inhibition of IDO1 is efficacious in preclinical models of breast cancer. As the response of breast cancer to immune checkpoint inhibitors may be limited, a better understanding of the expression of additional targetable immunomodulatory pathways is of importance. We therefore investigated the regulation of IDO1 expression in different breast cancer subtypes. We identified estrogen receptor α (ER) as a negative regulator of IDO1 expression. Serum kynurenine levels as well as tumoral IDO1 expression were lower in patients with ER-positive than ER-negative tumors and an inverse relationship between IDO1 and estrogen receptor mRNA was observed across 14 breast cancer data sets. Analysis of whole genome bisulfite sequencing, 450k, MassARRAY and pyrosequencing data revealed that the IDO1 promoter is hypermethylated in ER-positive compared with ER-negative breast cancer. Reduced induction of IDO1 was also observed in human ER-positive breast cancer cell lines. IDO1 induction was enhanced upon DNA demethylation in ER-positive but not in ER-negative cells and methylation of an IDO1 promoter construct reduced IDO1 expression, suggesting that enhanced methylation of the IDO1 promoter suppresses IDO1 in ER-positive breast cancer. The association of ER overexpression with epigenetic downregulation of IDO1 appears to be a particular feature of breast cancer as IDO1 was not suppressed by IDO1 promoter hypermethylation in the presence of high ER expression in cervical or endometrial cancer.

Prognostic value of tumor infiltrating lymphocyte subsets in breast cancer depends on hormone receptor status

PURPOSE

Interaction between immune-regulatory proteins and tumor infiltrating lymphocytes (TILs) is complex, and their associations may have significant clinical implications. This study was designed to evaluate the relationships between immunomodulatory proteins and TIL subsets and their impact on prognosis in breast cancer.

METHODS

377 invasive breast cancer cases were selected, and immunohistochemistry was performed for HLA-A, HLA-ABC, and indoleamine 2,3-dioxygenase (IDO); CD4+, CD8+, and FOXP3+ T cells were counted in intratumoral and stromal areas for both absolute numbers as well as their ratios.

RESULTS

While HLA-ABC and HLA-A expressions showed a positive correlation with CD8+ and FOXP3+ TIL infiltration, IDO expression showed a negative correlation with FOXP3+/CD4+ and FOXP3+/CD8+ T cell ratios. Expressions of HLA-ABC, HLA-A, and IDO shared an association with negative estrogen receptor status. Infiltration of CD4+, CD8+, and FOXP3+ TILs was significantly higher in tumors with high histologic grade, negative hormone receptor status, HER2 amplification, high Ki-67 index, and p53 overexpression. In survival analyses, increased CD4+ TIL infiltration was associated with better prognosis of the patients while other TIL subset infiltration and expression of immunomodulatory proteins had no prognostic significance. In subgroup analyses, high CD4+ TIL infiltration was revealed as an independent good prognostic factor in hormone receptor-negative subgroup while high FOXP3+/CD8+ T cell ratio was found to be an independent adverse prognostic factor in hormone receptor-positive subgroup, especially in luminal A subtype.

CONCLUSION

CD4+ TIL subset and FOXP3+/CD8+ T cell ratio have different prognostic significance in breast cancer according to hormone receptor status.

Biology and biogenesis of shed microvesicles

The ability of cells to transmit bioactive molecules to recipient cells and the extracellular environment is a fundamental requirement for both normal physiology and disease pathogenesis. It has traditionally been thought that soluble factors released from cells were responsible for this cellular signaling but recent research has revealed a fundamental role for microvesicles in this process. Microvesicles are heterogeneous membrane-bound sacs that are shed from the surface of cells into the extracellular environment in a highly regulated process. They are shed following the selective incorporation of a host of molecular cargo including multiple types of proteins and nucleic acids. In addition to providing new insight into the etiology of complex human diseases, microvesicles also show great promise as a tool for advanced diagnosis and therapy as we move forward into a new age of personalized medicine. Here we review current status of the rapidly evolving field of microvesicle biology, highlighting critical regulatory roles for several small GTPases in the biology and biogenesis of shed microvesicles.

Breast Cancer-Derived Extracellular Vesicles: Characterization and Contribution to the Metastatic Phenotype

The study of extracellular vesicles (EVs) in cancer progression is a complex and rapidly evolving field. Whole categories of cellular interactions in cancer which were originally presumed to be due solely to soluble secreted molecules have now evolved to include membrane-enclosed extracellular vesicles (EVs), which include both exosomes and shed microvesicles (MVs), and can contain many of the same molecules as those secreted in soluble form but many different molecules as well. EVs released by cancer cells can transfer mRNA, miRNA, and proteins to different recipient cells within the tumor microenvironment, in both an autocrine and paracrine manner, causing a significant impact on signaling pathways, mRNA transcription, and protein expression. The transfer of EVs to target cells, in turn, supports cancer growth, immunosuppression, and metastasis formation. This review focuses exclusively on breast cancer EVs with an emphasis on breast cancer-derived exosomes, keeping in mind that breast cancer-derived EVs share some common physical properties with EVs of other cancers.