Phase I Study of the Indoleamine 2,3-Dioxygenase 1 (IDO1) Inhibitor Navoximod (GDC-0919) Administered with PD-L1 Inhibitor (Atezolizumab) in Advanced Solid Tumors

Strategies to overcome myeloid cell induced immune suppression in the tumor microenvironment

Cancer progression and metastasis due to tumor immune evasion and drug resistance is strongly associated with immune suppressive cellular responses, particularly in the case of metastatic tumors. The myeloid cell component plays a key role within the tumor microenvironment (TME) and disrupts both adaptive and innate immune cell responses leading to loss of tumor control. Therefore, strategies to eliminate or modulate the myeloid cell compartment of the TME are increasingly attractive to non-specifically increase anti-tumoral immunity and enhance existing immunotherapies. This review covers current strategies targeting myeloid suppressor cells in the TME to enhance anti-tumoral immunity, including strategies that target chemokine receptors to deplete selected immune suppressive myeloid cells and relieve the inhibition imposed on the effector arms of adaptive immunity. Remodeling the TME can in turn improve the activity of other immunotherapies such as checkpoint blockade and adoptive T cell therapies in immunologically "cold" tumors. When possible, in this review, we have provided evidence and outcomes from recent or current clinical trials evaluating the effectiveness of the specific strategies used to target myeloid cells in the TME. The review seeks to provide a broad overview of how myeloid cell targeting can become a key foundational approach to an overall strategy for improving tumor responses to immunotherapy.

Tryptophan and its metabolites in normal physiology and cancer etiology

Within the growing field of amino acid metabolism, tryptophan (Trp) catabolism is an area of increasing interest. Trp is essential for protein synthesis, and its metabolism gives rise to biologically active catabolites including serotonin and numerous metabolites in the kynurenine (Kyn) pathway. In normal tissues, the production of Trp metabolites is directly regulated by the tissue-specific expression of Trp-metabolizing enzymes. Alterations of these enzymes in cancers can shift the balance and lead to an increased production of specific byproducts that can function as oncometabolites. For example, increased expression of the enzyme indoleamine 2,3-dioxygenase, which converts Trp into Kyn, leads to an increase in Kyn levels in numerous cancers. Kyn functions as an oncometabolite in cancer cells by promoting the activity of the transcription factor aryl hydrocarbon receptor, which regulates progrowth genes. Moreover, Kyn also inhibits T-cell activity and thus allows cancer cells to evade clearance by the immune system. Therefore, targeting the Kyn pathway has become a therapeutic focus as a novel means to abrogate tumor growth and immune resistance. This review summarizes the biological role and regulation of Trp metabolism and its catabolites with an emphasis on tumor cell growth and immune evasion and outlines areas for future research focus.

IDO1 Promotes the Progression of NSCLC by Regulating the Polarization of M2 Macrophages

Purpose

Non-small cell lung cancer (NSCLC) is currently a problem in the clinic and in society. Tumor-related macrophages (TAMs) in the tumor microenvironment (TME) play a vital role in the development of NSCLC.

Patients and Methods

Bioinformatics was used to analyze the role of Indoleamine 2,3-dioxygenase 1 (IDO1) in NSCLC and the correlation of its expression with CD163 expression. The expression of CD163 and IDO1 was measured by immunohistochemistry, and their colocalization was assessed by immunofluorescence. M2 macrophage polarization was induced, and a coculture model of NSCLC cells and macrophages was established.

Results

Bioinformatics analysis showed that IDO1 promoted the metastasis and differentiation of NSCLC and inhibited DNA repair. Moreover, the expression of IDO1 was positively correlated with CD163 expression. We discovered that IDO1 expression was related to M2 macrophage differentiation. In vitro, we showed that increased IDO1 expression promoted the invasion, proliferation, and metastasis of NSCLC cells.

Conclusion

In conclusion, we determined that IDO1 can regulate the M2 polarization of TAMs and promote the progression of NSCLC, which provides partial theoretical evidence for the use of IDO1 inhibitors in the treatment of NSCLC.

Mechanisms and Strategies to Overcome PD-1/PD-L1 Blockade Resistance in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is characterized by a high rate of systemic metastasis, insensitivity to conventional treatment and susceptibility to drug resistance, resulting in a poor patient prognosis. The immune checkpoint inhibitors (ICIs) represented by antibodies of programmed death receptor 1 (PD-1) and programmed death receptor ligand 1 (PD-L1) have provided new therapeutic options for TNBC. However, the efficacy of PD-1/PD-L1 blockade monotherapy is suboptimal immune response, which may be caused by reduced antigen presentation, immunosuppressive tumor microenvironment, interplay with other immune checkpoints and aberrant activation of oncological signaling in tumor cells. Therefore, to improve the sensitivity of TNBC to ICIs, suitable patients are selected based on reliable predictive markers and treated with a combination of ICIs with other therapies such as chemotherapy, radiotherapy, targeted therapy, oncologic virus and neoantigen-based therapies. This review discusses the current mechanisms underlying the resistance of TNBC to PD-1/PD-L1 inhibitors, the potential biomarkers for predicting the efficacy of anti-PD-1/PD-L1 immunotherapy and recent advances in the combination therapies to increase response rates, the depth of remission and the durability of the benefit of TNBC to ICIs.

Immune checkpoint blockade for locally advanced or recurrent/metastatic cervical cancer: An update on clinical data

Immunotherapy has shown great promise in the field of oncology, and recent clinical trials have illustrated that immune checkpoint blockade (ICB) is safe and effective at treating a range of tumor types. Cervical cancer (CC) is the fourth most common malignancy in women. However, first-line treatments for locally advanced cervical cancer (LACC) and recurrent/metastatic (R/M) CC have limited efficacy. Thus, it is necessary to explore new treatment approaches. The National Comprehensive Cancer Network (NCCN) currently recommends pembrolizumab, a programmed cell death protein 1 (PD-1) monoclonal antibody, as a first line therapy for individuals with R/M CC. This study reviews the progress of ICB therapy for LACC and R/M CC and describes the current status of the combination of ICB therapy and other therapeutic modalities, including radiotherapy, chemotherapy, targeted therapy, and other immunotherapies. The focus is placed on studies published since 2018 with the aim of highlighting novel CC-specific immunotherapeutic approaches and treatment targets.

Construction of a metabolism-related gene prognostic model to predict survival of pancreatic cancer patients

Pancreatic cancer (PC) is one of the most fatal malignant tumors, and is commonly diagnosed at an advanced stage with no effective therapy. Metabolism-related genes (MRGs) and immune-related genes (IRGs) play considerable roles in the tumor microenvironment. Therefore, an effective prediction model based on MRGs and IRGs could aid in the prognosis of PC. In this study, differential expression analysis was performed to gain 25 intersectional genes from 857 differentially expressed MRGs (DEMRGs), and 1353 differentially expressed IRGs, from The Cancer Genome Atlas database of PC. Cox and Lasso regression were applied and a five-DEMRGs prognostic model constructed. Survival analysis, ROC values, risk curve and validation analysis showed that the model could independently predict PC prognosis. In addition, the correlation analysis suggested that the five-DEMRGs prognostic model could reflect the status of the immune microenvironment, including Tregs, M1 macrophages and Mast cell resting. Therefore, our study provides new underlying predictive biomarkers and associated immunotherapy targets.

Lung Cancer Immunotherapy: Beyond Common Immune Checkpoints Inhibitors

Immunotherapy is an ever-expanding field in lung cancer treatment research. Over the past two decades, there has been significant progress in identifying immunotherapy targets and creating specific therapeutic agents, leading to a major paradigm shift in lung cancer treatment. However, despite the great success achieved with programmed death protein 1/ligand 1 (PD-1/PD-L1) monoclonal antibodies and with anti-PD-1/PD-L1 plus anti-cytotoxic T-lymphocyte antigen 4 (CTLA-4), only a minority of lung cancer patients respond to treatment, and of these many subsequently experience disease progression. In addition, immune-related adverse events sometimes can be life-threatening, especially when anti-CTLA-4 and anti-PD-1 are used in combination. All of this prompted researchers to identify novel immune checkpoints targets to overcome these limitations. Lymphocyte activation gene-3 (LAG-3), T cell immunoglobulin (Ig) and Immunoreceptor Tyrosine-Based Inhibitory Motif (ITIM) domain (TIGIT), T cell immunoglobulin and mucin-domain containing-3 (TIM-3) are promising molecules now under investigation. This review aims to outline the current role of immunotherapy in lung cancer and to examine efficacy and future applications of the new immune regulating molecules.

Clinical potential of PD-1/PD-L1 blockade therapy for renal cell carcinoma (RCC): a rapidly evolving strategy

Programmed death-1 (PD-1)/programmed death-ligand 1 (PD-L1) blockade therapy has become a game-changing therapeutic approach revolutionizing the treatment setting of human malignancies, such as renal cell carcinoma (RCC). Despite the remarkable clinical activity of anti-PD-1 or anti-PD-L1 monoclonal antibodies, only a small portion of patients exhibit a positive response to PD-1/PD-L1 blockade therapy, and the primary or acquired resistance might ultimately favor cancer development in patients with clinical responses. In light of this, recent reports have signified that the addition of other therapeutic modalities to PD-1/PD-L1 blockade therapy might improve clinical responses in advanced RCC patients. Until, combination therapy with PD-1/PD-L1 blockade therapy plus cytotoxic T lymphocyte antigen 4 (CTLA-4) inhibitor (ipilimumab) or various vascular endothelial growth factor receptors (VEGFRs) inhibitors axitinib, such as axitinib and cabozantinib, has been approved by the United States Food and Drug Administration (FDA) as first-line treatment for metastatic RCC. In the present review, we have focused on the therapeutic benefits of the PD-1/PD-L1 blockade therapy as a single agent or in combination with other conventional or innovative targeted therapies in RCC patients. We also offer a glimpse into the well-determined prognostic factor associated with the clinical response of RCC patients to PD-1/PD-L1 blockade therapy.

YH29407 with anti-PD-1 ameliorates anti-tumor effects via increased T cell functionality and antigen presenting machinery in the tumor microenvironment

Among cancer cells, indoleamine 2, 3-dioxygenase1 (IDO1) activity has been implicated in improving the proliferation and growth of cancer cells and suppressing immune cell activity. IDO1 is also responsible for the catabolism of tryptophan to kynurenine. Depletion of tryptophan and an increase in kynurenine exert important immunosuppressive functions by activating regulatory T cells and suppressing CD8⁺ T and natural killer (NK) cells. In this study, we compared the anti-tumor effects of YH29407, the best-in-class IDO1 inhibitor with improved pharmacodynamics and pharmacokinetics, with first and second-generation IDO1 inhibitors (epacadostat and BMS-986205, respectively). YH29407 treatment alone and anti-PD-1 (aPD-1) combination treatment induced significant tumor suppression compared with competing drugs. In particular, combination treatment showed the best anti-tumor effects, with most tumors reduced and complete responses. Our observations suggest that improved anti-tumor effects were caused by an increase in T cell infiltration and activity after YH29407 treatment. Notably, an immune depletion assay confirmed that YH29407 is closely related to CD8⁺ T cells. RNA-seq results showed that treatment with YH29407 increased the expression of genes involved in T cell function and antigen presentation in tumors expressing ZAP70, LCK, NFATC2, B2M, and MYD88 genes. Our results suggest that an IDO1 inhibitor, YH29407, has enhanced PK/PD compared to previous IDO1 inhibitors by causing a change in the population of CD8⁺ T cells including infiltrating T cells into the tumor. Ultimately, YH29407 overcame the limitations of the competing drugs and displayed potential as an immunotherapy strategy in combination with aPD-1.

Metabolic Regulation of CD8+ T Cells: From Mechanism to Therapy

Significance: Cancer immunotherapy has yielded striking antitumor effects in many cancers, yet the proportion of benefited patients is still limited. As key mediators of tumor suppression, CD8⁺ T cells are crucial for cancer immunotherapy. It has been widely appreciated that the modulation of CD8⁺ T cell immunity could be an effective way to further improve the therapeutic benefit of immunotherapy. Recent Advances: Emerging evidence has underlined a close link between metabolism and immune functions, providing a metabolism-immune axis that is increasingly investigated for understanding CD8⁺ T cell regulation. On the other hand, growing findings have reported that tumors adopt multiple approaches to induce metabolic reprogramming of CD8⁺ T cells, leading to compromised immunotherapy. Critical Issues: CD8⁺ T cell metabolism in the tumor microenvironment (TME) is often adapted to diminish antitumor immune responses and thereby evade from immune surveillance. A better understanding of metabolic regulation of CD8⁺ T cells in the TME is believed to hold promise for opening a new therapeutic window to further improve the benefit of immunotherapy. We herein review the mechanistic understanding of how CD8⁺ T cell metabolism is reprogrammed in the TME, mainly focusing on the impact of nutrient availability and bioactive molecules secreted by surrounding cells. Future Directions: Future research should pay attention to tumor heterogeneity in the metabolic microenvironment and associated immune responses. It is also important to include the trending opinion of "precision medicine" in cancer immunotherapies to tailor metabolic interventions for individual patients in combination with immunotherapy treatments. Antioxid. Redox Signal. 37, 1234-1253.

Immune checkpoint inhibitors in cervical cancer: Current status and research progress

Cervical cancer is the second most common gynecological malignant tumor endangering the health of women worldwide. Despite advances in the therapeutic strategies available to treat cervical cancer, the long-term prognosis of patients with recurrent and metastatic cervical cancer remains unsatisfactory. In recent years, immune checkpoint inhibitors (ICIs) have shown encouraging efficacy in the treatment of cervical cancer. ICIs have been approved for use in both first- and second-line cervical cancer therapies. This review summarizes the current knowledge of ICIs and the application of ICIs in clinical trials for the treatment of cervical cancer.

Metabolic reprogramming of the tumor immune microenvironment in ovarian cancer: A novel orientation for immunotherapy

Ovarian cancer is the most lethal gynecologic tumor, with the highest mortality rate. Numerous studies have been conducted on the treatment of ovarian cancer in the hopes of improving therapeutic outcomes. Immune cells have been revealed to play a dual function in the development of ovarian cancer, acting as both tumor promoters and tumor suppressors. Increasingly, the tumor immune microenvironment (TIME) has been proposed and confirmed to play a unique role in tumor development and treatment by altering immunosuppressive and cytotoxic responses in the vicinity of tumor cells through metabolic reprogramming. Furthermore, studies of immunometabolism have provided new insights into the understanding of the TIME. Targeting or activating metabolic processes of the TIME has the potential to be an antitumor therapy modality. In this review, we summarize the composition of the TIME of ovarian cancer and its metabolic reprogramming, its relationship with drug resistance in ovarian cancer, and recent research advances in immunotherapy.

Combination immunotherapy for pancreatic cancer: challenges and future considerations

INTRODUCTION

: Immune checkpoint inhibitors (ICI) have not yielded significant efficacy in pancreatic ductal adenocarcinoma (PDA), despite the role of the innate and adaptive immune systems on progression and survival. However, recently identified pathways have identified new targets and generated promising clinical investigations into promoting an effective immune-mediated antitumor response in PDA.

AREAS COVERED

: We review biological mechanisms associated with immunotherapy resistance and outline strategies for therapeutic combinations with established and novel therapies in PDA.

EXPERT OPINION

: Pancreatic cancers rarely benefits from treatment with ICI due to an immunosuppressive tumor microenvironment (TME). New understandings of factors associated with the suppressive TME, include low and poor quality neoantigens, constrained effector T cells infiltration, and the presence of a dense, suppressive myeloid cell population. These findings have been translated into new clinical investigations evaluating novel therapies in combination with ICI and/or standard systemic chemotherapy and radiotherapy. The epithelial, immune, and stromal compartments are intricately related in PDA, and the framework for successful targeting of this disease requires a comprehensive and personalized approach.

Current status and perspective of tumor immunotherapy for head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) have a high incidence and mortality rate, and investigating the pathogenesis and potential therapeutic strategies of HNSCC is required for further progress. Immunotherapy is a considerable therapeutic strategy for HNSCC due to its potential to produce a broad and long-lasting antitumor response. However, immune escape, which involves mechanisms including dyregulation of cytokines, perturbation of immune checkpoints, and recruitment of inhibitory cell populations, limit the efficacy of immunotherapy. Currently, multiple immunotherapy strategies for HNSCC have been exploited, including immune checkpoint inhibitors, costimulatory agonists, antigenic vaccines, oncolytic virus therapy, adoptive T cell transfer (ACT), and epidermal growth factor receptor (EGFR)-targeted therapy. Each of these strategies has unique advantages, and the appropriate application of these immunotherapies in HNSCC treatment has significant value for patients. Therefore, this review comprehensively summarizes the mechanisms of immune escape and the characteristics of different immunotherapy strategies in HNSCC to provide a foundation and consideration for the clinical treatment of HNSCC.

Immune checkpoint inhibitors for PD-1/PD-L1 axis in combination with other immunotherapies and targeted therapies for non-small cell lung cancer

It has been widely acknowledged that the use of immune checkpoint inhibitors (ICI) is an effective therapeutic treatment in many late-stage cancers. However, not all patients could benefit from ICI therapy. Several biomarkers, such as high expression of PD-L1, high mutational burden, and higher number of tumor infiltration lymphocytes have shown to predict clinical benefit from immune checkpoint therapies. One approach using ICI in combination with other immunotherapies and targeted therapies is now being investigated to enhance the efficacy of ICI alone. In this review, we summarized the use of other promising immunotherapies and targeted therapies in combination with ICI in treatment of lung cancers. The results from multiple animals and clinical trials were reviewed. We also briefly discussed the possible outlooks for future treatment.

Targeting Indoleamine Dioxygenase and Tryptophan Dioxygenase in Cancer Immunotherapy: Clinical Progress and Challenges

Indoleamine 2.3-dioxygenases (IDO1/2) and tryptophan 2.3-dioxygenase (TDO) are the initial and rate-limiting enzymes in tryptophan metabolism, which play an essential role in mediating immunosuppression in tumor microenvironment. Accumulating evidence has indicated that both IDO1 and TDO are highly expressed in many malignant tumors, and their expression is generally associated with reduced tumor-infiltrating immune cells, increased regulatory T-cell infiltration, as well as cancer progression and poor prognosis for malignancies. A large number of IDO1 and TDO inhibitors have been screened or synthesized in the last two decades. Thus far, at least 12 antagonists targeting IDO1 and TDO have advanced to clinical trials. In this account, we conducted a comprehensive review of the development of IDO1 and TDO inhibitors in cancer immunotherapy, particularly their clinical research progress, and presented the current challenges and corresponding solutions.

Immunotherapeutic Strategies for Head and Neck Squamous Cell Carcinoma (HNSCC): Current Perspectives and Future Prospects

Neoantigens are abnormal proteins produced by genetic mutations in somatic cells. Because tumour neoantigens are expressed only in tumour cells and have immunogenicity, they may represent specific targets for precision immunotherapy. With the reduction in sequencing cost, continuous advances in artificial intelligence technology and an increased understanding of tumour immunity, neoantigen vaccines and adoptive cell therapy (ACT) targeting neoantigens have become research hotspots. Approximately 900,000 patients worldwide are diagnosed with head and neck squamous cell carcinoma (HNSCC) each year. Due to its high mutagenicity and abundant lymphocyte infiltration, HNSCC naturally generates a variety of potential new antigen targets that may be used for HNSCC immunotherapies. Currently, the main immunotherapy for HNSCC is use of immune checkpoint inhibitors(ICIs). Neoantigen vaccines and adoptive cell therapy targeting neoantigens are extensions of immunotherapy for HNSCC, and a large number of early clinical trials are underway in combination with immune checkpoint inhibitors for the treatment of recurrent or metastatic head and neck squamous cell carcinoma (R/M HNSCC). In this paper, we review recent neoantigen vaccine trials related to the treatment of HNSCC, introduce adoptive cell therapy targeting neoantigens, and propose a potential treatment for HNSCC. The clinical application of immune checkpoint inhibitor therapy and its combination with neoantigen vaccines in the treatment of HNSCC are summarized, and the prospect of using neoantigen to treat HNSCC is discussed and proposed.

Immune checkpoint inhibitor-based therapy for advanced clear cell renal cell carcinoma: A narrative review

The prognosis for advanced clear cell renal cell carcinoma (ccRCC) is not satisfactory, even though its treatment has evolved rapidly over the past 20 years. Systemic ccRCC treatment options mainly involve antiangiogenic therapy, immune checkpoint blockade, or a combination of these therapies, and as more clinical evidence becomes available, immune checkpoint inhibitors (ICIs) are increasingly dominant. Conventional ICIs lead to the restoration of T-cell activation and a reduction in T-cell depletion by specifically blocking programmed cell death 1 (PD-1), programmed cell death 1 ligand 1 (PD-L1) or cytotoxic T lymphocyte antigen 4 (CTLA-4), ultimately enhancing the antitumor immune response. There is no doubt that these therapies have achieved some clinical efficacy in the overall ccRCC population, but response rates and durability remain a great challenge. Therefore, novel immune checkpoints or new combination therapeutic strategies based on ICIs continue to be sought and developed. This review will provide a comprehensive overview of ICI-based therapeutic strategies in advanced ccRCC, including their mechanisms of action and the latest clinical evidence.

Novel 1,2,3-Triazole Erlotinib Derivatives as Potent IDO1 Inhibitors: Design, Drug-Target Interactions Prediction, Synthesis, Biological Evaluation, Molecular Docking and ADME Properties Studies

Indoleamine 2,3-dioxygenase 1 (IDO1) plays a predominant role in cancer immunotherapy which catalyzes the initial and rate limiting steps of the kynurenine pathway as a key enzyme. To explore novel IDO1 inhibitors, five derivatives of erlotinib-linked 1,2,3-triazole compounds were designed by using a structure-based drug design strategy. Drug-target interactions (DTI) were predicted by DeePurpose, an easy-to-use deep learning library that contains more than 50 algorithms. The DTI prediction results suggested that the designed molecules have potential inhibitory activities for IDO1. Chemical syntheses and bioassays showed that the compounds exhibited remarkable inhibitory activities against IDO1, among them, compound e was the most potent with an IC₅₀ value of 0.32 ± 0.07 μM in the Hela cell assay. The docking model and ADME analysis exhibited that the effective interactions of these compounds with heme iron and better drug-likeness ensured the IDO1 inhibitory activities. The studies suggested that compound e was a novel and interesting IDO1 inhibitor for further development.

The Treatment of Advanced Melanoma: Therapeutic Update

Cutaneous melanoma is the main cause of death for skin cancer. The majority of patients with a diagnosis of melanoma have localized disease, which can be successfully treated with surgical treatment. However, the surgical approach is not curative for advanced melanoma (AM). Indeed, the management of AM is still challenging, since melanoma is the solid tumor with the highest number of mutations and cancer cells have the capacity to evade the immune system. In the past, the treatment of AM relied on chemotherapeutic agents, without showing efficacy data. Recent knowledge on melanoma pathogenesis as well as the introduction of immunotherapies, targeted therapies vaccines, small molecules, and combination therapies has revolutionized AM management, showing promising results in terms of effectiveness and safety. The aim of this review is to assess and to discuss the role of emerging therapies for AM management in order to obtain a complete overview of the currently available treatment options and future perspectives.

The Role of Indoleamine 2, 3-Dioxygenase 1 in Regulating Tumor Microenvironment

Indoleamine 2, 3-dioxygenase 1 (IDO1) is a rate-limiting enzyme that metabolizes an essential amino acid tryptophan (Trp) into kynurenine (Kyn), and it promotes the occurrence of immunosuppressive effects by regulating the consumption of Trp and the accumulation of Kyn in the tumor microenvironment (TME). Recent studies have shown that the main cellular components of TME interact with each other through this pathway to promote the formation of tumor immunosuppressive microenvironment. Here, we review the role of the immunosuppression mechanisms mediated by the IDO1 pathway in tumor growth. We discuss obstacles encountered in using IDO1 as a new tumor immunotherapy target, as well as the current clinical research progress.

Sodium Tanshinone IIA Sulfonate as a Potent IDO1/TDO2 Dual Inhibitor Enhances Anti-PD1 Therapy for Colorectal Cancer in Mice

Although the antitumor efficacy of immune checkpoint blockade (ICB) has been proved in colorectal cancer (CRC), the results are unsatisfactory, presumably owing to the presence of tryptophan metabolism enzymes indoleamine 2,3-dioxygenase 1 (IDO1) and tryptophan 2,3-dioxygenase 2 (TDO2). However, only a few dual inhibitors for IDO1 and TDO2 have been reported. Here, we discovered that sodium tanshinone IIA sulfonate (STS), a sulfonate derived from tanshinone IIA (TSN), reduced the enzymatic activities of IDO1 and TDO2 with a half inhibitory concentration (IC₅₀) of less than 10 μM using enzymatic assays for natural product screening. In IDO1- or TDO2- overexpressing cell lines, STS decreased kynurenine (kyn) synthesis. STS also reduced the percentage of forkhead box P3 (FOXP3) T cells in lymphocytes from the mouse spleen cocultured with CT26. In vivo, STS suppressed tumor growth and enhanced the antitumor effect of the programmed cell death 1 (PD1) antibody. Compared with anti-PD1 (α-PD1) monotherapy, combined with STS had lower level of plasma kynurenine. Immunofluorescence assay suggested that STS decreased the number of FOXP3+ T cells and increased the number of CD8+ T cells in tumors. Flow cytometry analysis of immune cells in tumor tissues demonstrated an increase in the percentage of tumor-infiltrating CD8+ T cells. According to our findings, STS acts as an immunotherapy agent in CRC by inhibiting both IDO1 and TDO2.

Therapeutic approaches for the treatment of head and neck squamous cell carcinoma-An update on clinical trials

Head and neck squamous cell carcinoma (HNSCC) is the sixth most common non-skin cancer with a tobacco consumption and infection with high-risk human papillomavirus (HPV) being major risk factors. Despite advances in numerous therapy modalities, survival rates for HNSCC have not improved considerably; a vast number of clinical outcomes have demonstrated that a combination strategy (the most well-known docetaxel, cisplatin, and 5-fluorouracil) is the most effective treatment choice. Immunotherapy that targets immunological checkpoints is being tested in a number of clinical trials, either alone or in conjunction with chemotherapeutic or targeted therapeutic drugs. Various monoclonal antibodies, such as cetuximab and bevacizumab, which target the EGFR and VEGFR, respectively, as well as other signaling pathway inhibitors, such as temsirolimus and rapamycin, are also being studied for the treatment of HNSCC. We have reviewed the primary targets in active clinical studies in this study, with a particular focus on the medications and drug targets used.

The STING pathway: Therapeutic vulnerabilities in ovarian cancer

Ovarian cancer is the leading cause of mortality due to gynecologic malignancy. The majority of women diagnosed with the most common subtype, high-grade serous ovarian carcinoma (HGSC), develop resistance to conventional therapies despite initial response to treatment. HGSC tumors displaying DNA damage repair (DDR) gene deficiency and high chromosomal instability mainly associate with higher cytotoxic immune cell infiltration and expression of genes associated with these immune pathways. Despite the high level of immune infiltration observed, the majority of patients with HGSC have not benefited from immunomodulatory treatments as the mechanistic basis of this infiltration is unclear. This lack of response can be primarily attributed to heterogeneity at the levels of both cancer cell genetic alterations and the tumour immune microenvironment. Strategies to enhance anti-tumour immunity have been investigated in ovarian cancer, of which interferon activating therapies present as an attractive option. Of the several type I interferon (IFN-1) stimulating therapies, exogenously activating the cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway is emerging as a promising avenue. Herein, we highlight our current understanding of how constitutive and induced cGAS-STING pathway activation influences the ovarian tumour microenvironment. We further elaborate on the links between the genomic alterations prevalent in ovarian tumours and how the resultant immune phenotypes can make them more susceptible to exogenous STING pathway activation and potentiate immune-mediated killing of cancer cells. The therapeutic potential of cGAS-STING pathway activation in ovarian cancer and factors implicating treatment outcomes are discussed, providing a rationale for future combinatorial treatment approaches on the backbone of chemotherapy.

Multi-target combinatory strategy to overcome tumor immune escape

Immune therapy has become the fourth approach after surgery, chemotherapy, and radiotherapy in cancer treatment. Many immune checkpoints were identified in the last decade since ipilimumab, which is the first immune checkpoint inhibitor to cytotoxic T-lymphocyte associated protein 4, had been approved by the US Food and Drug Administration (FDA) for the treatment of unresectable or metastatic melanoma in 2011. The use of several antibody drugs that target PD1/PD-L1 for various cancer treatments has been approved by the FDA. However, fewer people are benefitting from immune checkpoint inhibitor treatment in solid cancers. Approximately 80% of patients do not respond appropriately because of primary or acquired therapeutic resistance. Along with the characterization of more immune checkpoints, the combinatory treatment of multiimmune checkpoint inhibitors becomes a new option when monotherapy could not receive a good response. In this work, the author focuses on the combination therapy of multiple immune checkpoints (does not include targeted therapy of oncogenes or chemotherapy), introduces the current progression of multiple immune checkpoints and their related inhibitors, and discusses the advantages of combination therapy, as well as the risk of immune-related adverse events.

Ginseng polysaccharides alter the gut microbiota and kynurenine/tryptophan ratio, potentiating the antitumour effect of antiprogrammed cell death 1/programmed cell death ligand 1 (anti-PD-1/PD-L1) immunotherapy

OBJECTIVE

Programmed death 1 and its ligand 1 (PD-1/PD-L1) immunotherapy is promising for late-stage lung cancer treatment, however, the response rate needs to be improved. Gut microbiota plays a crucial role in immunotherapy sensitisation and Panax ginseng has been shown to possess immunomodulatory potential. In this study, we aimed to investigate whether the combination treatment of ginseng polysaccharides (GPs) and αPD-1 monoclonal antibody (mAb) could sensitise the response by modulating gut microbiota.

DESIGN

Syngeneic mouse models were administered GPs and αPD-1 mAb, the sensitising antitumour effects of the combination therapy on gut microbiota were assessed by faecal microbiota transplantation (FMT) and 16S PacBio single-molecule real-time (SMRT) sequencing. To assess the immune-related metabolites, metabolomics analysis of the plasma samples was performed.

RESULTS

We found GPs increased the antitumour response to αPD-1 mAb by increasing the microbial metabolites valeric acid and decreasing L-kynurenine, as well as the ratio of Kyn/Trp, which contributed to the suppression of regulatory T cells and induction of T_eff cells after combination treatment. Besides, the microbial analysis indicated that the abundance of Parabacteroides distasonis and Bacteroides vulgatus was higher in responders to anti-PD-1 blockade than non-responders in the clinic. Furthermore, the combination therapy sensitised the response to PD-1 inhibitor in the mice receiving microbes by FMT from six non-responders by reshaping the gut microbiota from non-responders towards that of responders.

CONCLUSION

Our results demonstrate that GPs combined with αPD-1 mAb may be a new strategy to sensitise non-small cell lung cancer patients to anti-PD-1 immunotherapy. The gut microbiota can be used as a novel biomarker to predict the response to anti-PD-1 immunotherapy.

Stereoselective Synthesis of the IDO Inhibitor Navoximod

A highly efficient asymmetric synthesis of the IDO inhibitor navoximod, featuring the stereoselective installation of two relative and two absolute stereocenters from an advanced racemic intermediate, is described. The stereocenters were set via a crystallization-induced dynamic resolution along with two selective ketone reductions: one via a biocatalytic ketoreductase transformation and one via substrate-controlled hydride delivery from LiAlH(Ot-Bu)₃. Following this strategy, navoximod was synthesized in 10 steps from 2-fluorobenzaldehyde and isolated in 23% overall yield with 99.7% ee and high purity.

Combination therapy for pancreatic cancer: anti-PD-(L)1-based strategy

Mortality associated with pancreatic cancer is among the highest of all malignancies, with a 5-year overall survival of 5-10%. Immunotherapy, represented by the blocking antibodies against programmed cell death protein 1 or its ligand 1 (anti-PD-(L)1), has achieved remarkable success in a number of malignancies. However, due to the immune-suppressive tumor microenvironment, the therapeutic efficacy of anti-PD-(L)1 in pancreatic cancer is far from expectation. To address such a fundamental issue, chemotherapy, radiotherapy, targeted therapy and even immunotherapy itself, have individually been attempted to combine with anti-PD-(L)1 in preclinical and clinical investigation. This review, with a particular focus on pancreatic cancer therapy, collects current anti-PD-(L)1-based combination strategy, highlights potential adverse effects of accumulative combination, and further points out future direction in optimization of combination, including targeting post-translational modification of PD-(L)1 and improving precision of treatment.

Medical Therapy for Craniopharyngiomas

Craniopharyngiomas are rare benign neoplasms presenting in two different types, adamantinomatous (ACP) or papillary (PCP), which are molecularly and clinically distinct. Traditional treatment includes surgical resection and radiotherapy, which are accompanied by a number of debilitating complications because of the tumours' proximity to important brain structures. Recent advances in the understanding of molecular pathogenesis of craniopharyngiomas have opened horizons to medical therapeutic options. ACPs are mainly characterized by mutations of β-catenin, which activate Wingless/Int (Wnt), and alter the mitogen extracellular kinase (MEK)/extracellular signal-regulated kinase (ERK) pathway, as well as inflammatory, cellular senescence, programmed cell death and sonic hedgehog (SHH) pathways. PCPs are mainly characterized by Ras/Raf/MEK/ERK pathway activation secondary to BRAF-V600E mutations. MEK inhibitors, such as binimetinib, or anti-inflammatory mediators, such as tocilizumab or interferon, have been administered to patients with ACP and the efficacy is mostly favourable. On the other hand, BRAF inhibitors, such as dabrafenib or vemurafenib, either alone or in combination with the MEK inhibitors trametinib and cobimetinib, have been administered to patients with PCP resulting in favourable responses. A number of ongoing trials will shed light on schemes, doses, combined treatments and safety issues of the new molecular-targeted treatments, changing the management of patients with craniopharyngiomas by launching the era of personalized medicine in these rare neoplasms. We conducted a systematic review to identify case series or case reports with patients currently treated with systemic medical therapy.

Targeting Tryptophan Catabolism in Cancer Immunotherapy Era: Challenges and Perspectives

Metabolism of tryptophan (Trp), an essential amino acid, represent a major metabolic pathway that both promotes tumor cell intrinsic malignant properties as well as restricts antitumour immunity, thus emerging as a drug development target for cancer immunotherapy. Three cytosolic enzymes, namely indoleamine 2,3-dioxygenase 1 (IDO1), IDO2 and tryptophan 2,3-dioxygenase (TDO2), catalyzes the first-rate limiting step of the degradation of Trp to kynurenine (Kyn) and modulates immunity toward immunosuppression mainly through the aryl hydrocarbon receptor (AhR) activation in numerous types of cancer. By restoring antitumor immune responses and synergizing with other immunotherapies, the encouraging preclinical data of IDO1 inhibitors has dramatically failed to translate into clinical success when combined with immune checkpoints inhibitors, reigniting the debate of combinatorial approach. In this review, we i) provide comprehensive evidences on immunomodulatory role of the Trp catabolism metabolites that highlight this pathway as relevant target in immuno-oncology, ii)ii) discuss underwhelming results from clinical trials investigating efficacy of IDO1 inhibitors and underlying mechanisms that might have contributed to this failure, and finally, iii) discuss the current state-of-art surrounding alternative approaches of innovative antitumor immunotherapies that target molecules of Trp catabolism as well as challenges and perspectives in the era of immunotherapy.

What Do We Have to Know about PD-L1 Expression in Prostate Cancer? A Systematic Literature Review (Part 6): Correlation of PD-L1 Expression with the Status of Mismatch Repair System, BRCA, PTEN, and Other Genes

Pembrolizumab (anti-PD-1) is allowed in selected metastatic castration-resistant prostate cancer (PC) patients showing microsatellite instability/mismatch repair system deficiency (MSI-H/dMMR). BRCA1/2 loss-of-function is linked to hereditary PCs and homologous recombination DNA-repair system deficiency: poly-ADP-ribose-polymerase inhibitors can be administered to BRCA-mutated PC patients. Recently, docetaxel-refractory metastatic castration-resistant PC patients with BRCA1/2 or ATM somatic mutations had higher response rates to pembrolizumab. PTEN regulates cell cycle/proliferation/apoptosis through pathways including the AKT/mTOR, which upregulates PD-L1 expression in PC. Our systematic literature review (PRISMA guidelines) investigated the potential correlations between PD-L1 and MMR/MSI/BRCA/PTEN statuses in PC, discussing few other relevant genes. Excluding selection biases, 74/677 (11%) PCs showed dMMR/MSI; 8/67 (12%) of dMMR/MSI cases were PD-L1+. dMMR-PCs included ductal (3%) and acinar (14%) PCs (all cases tested for MSI were acinar-PCs). In total, 15/39 (39%) PCs harbored BRCA1/2 aberrations: limited data are available for PD-L1 expression in these patients. 13/137 (10%) PTEN- PCs were PD-L1+; 10/29 (35%) PD-L1+ PCs showed PTEN negativity. SPOP mutations may increase PD-L1 levels, while the potential correlation between PD-L1 and ERG expression in PC should be clarified. Further research should verify how the efficacy of PD-1 inhibitors in metastatic castration-resistant PCs is related to dMMR/MSI, DNA-damage repair genes defects, or PD-L1 expression.

Efficacy and Safety of Immunotherapy for Cervical Cancer—A Systematic Review of Clinical Trials

Purpose: To systematically review the current body of evidence on the efficacy and safety of immunotherapy for cervical cancer (CC). Material and Methods: Medline, the Cochrane Central Register of Controlled Trials and Web of Science were searched for prospective trials assessing immunotherapy in CC patients in compliance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Full-text articles in English and German reporting outcomes of survival, response rates or safety were eligible. Results: Of 4655 screened studies, 51 were included (immune checkpoint inhibitors (ICI) n=20; therapeutic vaccines n = 25; adoptive cell transfer therapy n=9). Of these, one qualified as a phase III randomized controlled trial and demonstrated increased overall survival following treatment with pembrolizumab, chemotherapy and bevacizumab. A minority of studies included a control group (n = 7) or more than 50 patients (n = 15). Overall, response rates were low to moderate. No response to ICIs was seen in PD-L1 negative patients. However, few remarkable results were achieved in heavily pretreated patients. There were no safety concerns in any of the included studies. Conclusion: Strong evidence on the efficacy of strategies to treat recurrent or metastatic cervical cancer is currently limited to pembrolizumab in combination with chemotherapy and bevacizumab, which substantiates an urgent need for large confirmatory trials on alternative immunotherapies. Overall, there is sound evidence on the safety of immunotherapy in CC.

Small Molecule Regulators Targeting NAD+ Biosynthetic Enzymes

Nicotinamide adenine dinucleotide (NAD+) is a key player in many metabolic pathways as an activated carrier of electrons. In addition to being the cofactor for redox reactions, NAD+ also serves as the substrate for various enzymatic transformations such as adenylation and ADP-ribosylation. Maintaining cellular NAD+ homeostasis has been suggested as an effective anti-aging strategy. Given the importance of NAD+ in regulating a broad spectrum of cellular events, small molecules targeting NAD+ metabolism have been pursued as therapeutic interventions for the treatment of mitochondrial disorders and agerelated diseases. In this article, small molecule regulators of NAD+ biosynthetic enzymes will be reviewed. The focus will be given to the discovery and development of these molecules, the mechanism of action as well as their therapeutic potentials.

B7-H4 is increased in lung adenocarcinoma harboring EGFR-activating mutations and contributes to immunosuppression

PD-1/PD-L1 inhibitors have shown clinical benefit in lung adenocarcinoma (LUAD). However, the immunotherapy strategy is less effective in patients with EGFR-activating mutations (EGFR MT). Studies showed that besides low expression of PD-L1, the absence of TILs and distinct expression profile of immune checkpoint molecules might be associated with low response of the patient subset. In this study, we first compared CD8A, GZMB and PRF1 mRNA levels in different LUAD subtypes harboring different driver mutations by dataset analyses and investigated the association between 15 well-defined B7-CD28 family members and driver mutations. The results showed that the decreases in the density and function of CD8+ TILs, CD274 (PD-L1 gene), and CD86 and increases in VTCN1 (B7-H4 gene) and HHLA2 were associated with LUAD with EGFR-activating mutations. Immunohistochemical staining studies further supported that PD-L1 was downregulated and B7-H4 was upregulated in the subtype. Furthermore, PD-L1 expression was positively associated with levels of CD8A and granzyme B, while B7-H4 expression was negatively associated with granzyme B levels. In lung cancer cell lines, EGFR-activating mutations effectively upregulated B7-H4 and downregulated PD-L1. MEK/ERK-pathway activation upregulated B7-H4, and PI3K/Akt activation upregulated PD-L1. EGFR 19Del mutation was associated with inhibition of CD8+ T-cell function, while knocking down B7-H4 could reverse the inhibition, and further showed tumor-growth inhibition and longer survival in vivo. Taken together, this study shed light on that B7-H4 might be an alternative immune-checkpoint molecule and a potential therapeutic target for LUAD with EGFR MT.

New Strategies and Combinations to Improve Outcomes in Immunotherapy in Metastatic Non-Small-Cell Lung Cancer

Immune checkpoint inhibitors have transformed the treatment of metastatic non-small-cell lung cancer, yielding marked improvements in survival and the potential for durable clinical responses. Primary and acquired resistance to current immune checkpoint inhibitors constitute a key challenge despite the remarkable responses observed in a subset of patients. Multiple novel combination immunotherapy and adoptive cell therapy strategies are presently being developed to address treatment resistance. The success of these strategies hinges upon rational clinical trial design as well as careful consideration of the immunologic mechanisms within the variable tumor immune microenvironment (TIME) which underpin resistance to immunotherapy. Further research is needed to facilitate a deeper understanding of these complex mechanisms within the TIME, which may ultimately provide the key to restoring and enhancing an effective anti-tumor immune response. This review aims to provide an introduction to some of the recent and notable combination immunotherapy and cell therapy strategies used in advanced non-small-cell lung cancer (NSCLC), and the rationale for their use based on current understanding of the anti-tumor immune response and mechanisms of resistance within the TIME.

Signal pathways of melanoma and targeted therapy

Melanoma is the most lethal skin cancer that originates from the malignant transformation of melanocytes. Although melanoma has long been regarded as a cancerous malignancy with few therapeutic options, increased biological understanding and unprecedented innovations in therapies targeting mutated driver genes and immune checkpoints have substantially improved the prognosis of patients. However, the low response rate and inevitable occurrence of resistance to currently available targeted therapies have posed the obstacle in the path of melanoma management to obtain further amelioration. Therefore, it is necessary to understand the mechanisms underlying melanoma pathogenesis more comprehensively, which might lead to more substantial progress in therapeutic approaches and expand clinical options for melanoma therapy. In this review, we firstly make a brief introduction to melanoma epidemiology, clinical subtypes, risk factors, and current therapies. Then, the signal pathways orchestrating melanoma pathogenesis, including genetic mutations, key transcriptional regulators, epigenetic dysregulations, metabolic reprogramming, crucial metastasis-related signals, tumor-promoting inflammatory pathways, and pro-angiogenic factors, have been systemically reviewed and discussed. Subsequently, we outline current progresses in therapies targeting mutated driver genes and immune checkpoints, as well as the mechanisms underlying the treatment resistance. Finally, the prospects and challenges in the development of melanoma therapy, especially immunotherapy and related ongoing clinical trials, are summarized and discussed.

Recent advances in clinical trials targeting the kynurenine pathway

The kynurenine pathway (KP) is the major catabolic pathway for the essential amino acid tryptophan leading to the production of nicotinamide adenine dinucleotide. In inflammatory conditions, the activation of the KP leads to the production of several bioactive metabolites including kynurenine, 3-hydroxykynurenine, 3-hydroxyanthranilic acid, kynurenic acid and quinolinic acid. These metabolites can have redox and immune suppressive activity, be neurotoxic or neuroprotective. While the activity of the pathway is tightly regulated under normal physiological condition, it can be upregulated by immunological activation and inflammation. The dysregulation of the KP has been implicated in wide range of neurological diseases and psychiatric disorders. In this review, we discuss the mechanisms involved in KP-mediated neurotoxicity and immune suppression, and its role in diseases of our expertise including cancer, chronic pain and multiple sclerosis. We also provide updates on the clinical trials evaluating the efficacy of KP inhibitors and/or analogues in each respective disease.

A Novel Assessment Model Based on Molecular Subtypes of Hypoxia-Related LncRNAs for Prognosis of Bladder Cancer

Hypoxia is a common feature in various tumors that regulates aggressiveness. Previous studies have demonstrated that some dysregulated long non-coding RNAs (lncRNAs) are correlated with tumor progression, including bladder cancer (BCa). However, the prognostic effect of hypoxia-related lncRNAs (HRLs) and their clinical relevance, as well as their regulatory effect on the tumor immune microenvironment, are largely unknown in BCa. A co-expression analysis between hypoxia genes and lncRNA expression, which was downloaded from the TCGA database, was performed to identify HRLs. Univariate Cox regression analysis was performed to select the most desirable lncRNAs for molecular subtype, and further LASSO analysis was performed to develop a prognostic model. This molecular subtype based on four HRLs (AC104653, AL136084, AL139393, and LINC00892) showed good performance in the tumor microenvironment and tumor mutation burden. The prognostic risk model suggested better performance in predicting BCa patients' prognosis and obtained a close correlation with clinicopathologic features. Furthermore, four of five first-line clinical chemotherapies showed different sensitivities to this model, and nine immune checkpoints showed different expression in the molecular subtypes or the risk model. In conclusion, this study indicates that this molecular subtype and risk model based on HRLs may be useful in improving the prognostic prediction of BCa patients with different clinical situations and may help to find a useful target for tumor therapy.

Various Uses of PD1/PD-L1 Inhibitor in Oncology: Opportunities and Challenges

The occurrence and development of cancer are closely related to the immune escape of tumor cells and immune tolerance. Unlike previous surgical, chemotherapy, radiotherapy and targeted therapy, tumor immunotherapy is a therapeutic strategy that uses various means to stimulate and enhance the immune function of the body, and ultimately achieves the goal of controlling tumor cells.With the in-depth understanding of tumor immune escape mechanism and tumor microenvironment, and the in-depth study of tumor immunotherapy, immune checkpoint inhibitors represented by Programmed Death 1/Programmed cell Death-Ligand 1(PD-1/PD-L1) inhibitors are becoming increasingly significant in cancer medication treatment. employ a variety of ways to avoid detection by the immune system, a single strategy is not more effective in overcoming tumor immune evasion and metastasis. Combining different immune agents or other drugs can effectively address situations where immunotherapy is not efficacious, thereby increasing the chances of success and alternative access to alternative immunotherapy. Immune combination therapies for cancer have become a hot topic in cancer treatment today. In this paper, several combination therapeutic modalities of PD1/PD-L1 inhibitors are systematically reviewed. Finally, an analysis and outlook are provided in the context of the recent advances in combination therapy with PD1/PD-L1 inhibitors and the pressing issues in this field.

What Do We Have to Know about PD-L1 Expression in Prostate Cancer? A Systematic Literature Review. Part 7: PD-L1 Expression in Liquid Biopsy

Liquid biopsy is an accessible, non-invasive diagnostic tool for advanced prostate cancer (PC) patients, potentially representing a real-time monitoring test for tumor evolution and response to treatment through the analysis of circulating tumor cells (CTCs) and exosomes. We performed a systematic literature review (PRISMA guidelines) to describe the current knowledge about PD-L1 expression in liquid biopsies of PC patients: 101/159 (64%) cases revealed a variable number of PD-L1+ CTCs. Outcome correlations should be investigated in larger series. Nuclear PD-L1 expression by CTCs was occasionally associated with worse prognosis. Treatment (abiraterone, enzalutamide, radiotherapy, checkpoint-inhibitors) influenced PD-L1+ CTC levels. Discordance in PD-L1 status was detected between primary vs. metastatic PC tissue biopsies and CTCs vs. corresponding tumor tissues. PD-L1 is also released by PC cells through soluble exosomes, which could inhibit the T cell function, causing immune evasion. PD-L1+ PC-CTC monitoring and genomic profiling may better characterize the ongoing aggressive PC forms compared to PD-L1 evaluation on primary tumor biopsies/prostatectomy specimens (sometimes sampled a long time before recurrence/progression). Myeloid-derived suppressor cells and dendritic cells (DCs), which may have immune-suppressive effects in tumor microenvironment, have been found in PC patients circulation, sometimes expressing PD-L1. Occasionally, their levels correlated to clinical outcome. Enzalutamide-progressing castration-resistant PC patients revealed increased PD-1+ T cells and circulating PD-L1/2+ DCs.

Emerging immunological strategies: recent advances and future directions

Immunotherapy plays a compelling role in cancer treatment and has already made remarkable progress. However, many patients receiving immune checkpoint inhibitors fail to achieve clinical benefits, and the response rates vary among tumor types. New approaches that promote anti-tumor immunity have recently been developed, such as small molecules, bispecific antibodies, chimeric antigen receptor T cell products, and cancer vaccines. Small molecule drugs include agonists and inhibitors that can reach the intracellular or extracellular targets of immune cells participating in innate or adaptive immune pathways. Bispecific antibodies, which bind two different antigens or one antigen with two different epitopes, are of great interest. Chimeric antigen receptor T cell products and cancer vaccines have also been investigated. This review explores the recent progress and challenges of different forms of immunotherapy agents and provides an insight into future immunotherapeutic strategies.

Identification and Validation of Immune- and Stemness-Related Prognostic Signature of Melanoma

Purpose: Our aim was to construct a signature that accurately predicted the prognostic and immune response of melanoma. Methods: First, the weighted co-expression network analysis (WGCNA) algorithm was used to identify the hub genes related to clinical phenotypes of melanoma in the cancer genome atlas (TCGA) database. Nest, the least absolute shrinkage and selection operator (LASSO) analysis was used to dimensionality reduction of these hub genes and constructed a prognostic signature to predict the prognosis and immunosuppressive response of melanoma. Result: Through in-depth analysis, we constructed a 5-mRNA prognostic signature and verified its prognostic value in internal (TCGA-SKCM, n = 452) and external independent datasets (GSE53118, n = 79). Based on this signature, the tumor immune microenvironment (TME) of melanoma was characterized, and the result was found that patients in the high-risk group had lower CD8 T cell infiltration and immune checkpoint expression (PD-1, PD-L1, CTLA4), as well as higher M0/M2 macrophage infiltration. Our results also found the risk score based on a 5-mRNA signature was significantly associated with tumor mutational burden (TMB) and tumor stem cell markers (CD20, CD38, ABCB5, CD44, etc.). Lastly, we built a nomogram for clinician prediction for the prognosis of patients with melanoma. Conclusion: Our findings indicated that the 5-mRNA signature has an important predictive value for the overall survival of melanoma. By analyzing the tumor immune microenvironment and tumor stem cell marker between different groups, a new method is provided for the stratified diagnosis and treatment of melanoma.

Tumor-Infiltrating CD8+ T Cells Driven by the Immune Checkpoint-Associated Gene IDO1 Are Associated With Cervical Cancer Prognosis

Tumor-infiltrating immune cells, associated with tumor progression, are promising prognostic biomarkers. However, the relationship between levels of gene expression and that of immune cell infiltration in cervical cancer prognosis is unknown. In this study, three cervical cancer gene expression microarrays (GSE6791, GSE63678 and GSE55940) were obtained from the GEO database. The IDO1 gene was identified by differentially expressed gene screening. The gene expression profiles of TCGA and GTEx databases along with comprehensive bioinformatics analysis identified that the IDO1 gene was upregulated in cervical cancer with significant difference in expression at different N stages. In addition, it was also upregulated in HPV16 positive sample. The pan-cancer analysis identified that IDO1 was highly expressed in most cancers. TIMER analysis revealed that the expression of IDO1 in CESC shows positive correlation with CD8⁺ T cells, CD4⁺ T cells, neutrophils, dendritic cells. IDO1 expression showed remarkable positive correlation with all immune cell markers except M1 macrophages. CD8⁺ T cell infiltration GSEA results showed that IDO1 was mainly associated with tumor immune-related signaling pathways.

What Do We Have to Know about PD-L1 Expression in Prostate Cancer? A Systematic Literature Review. Part 5: Epigenetic Regulation of PD-L1

Epigenetic alterations (including DNA methylation or miRNAs) influence oncogene/oncosuppressor gene expression without changing the DNA sequence. Prostate cancer (PC) displays a complex genetic and epigenetic regulation of cell-growth pathways and tumor progression. We performed a systematic literature review (following PRISMA guidelines) focused on the epigenetic regulation of PD-L1 expression in PC. In PC cell lines, CpG island methylation of the CD274 promoter negatively regulated PD-L1 expression. Histone modifiers also influence the PD-L1 transcription rate: the deletion or silencing of the histone modifiers MLL3/MML1 can positively regulate PD-L1 expression. Epigenetic drugs (EDs) may be promising in reprogramming tumor cells, reversing epigenetic modifications, and cancer immune evasion. EDs promoting a chromatin-inactive transcriptional state (such as bromodomain or p300/CBP inhibitors) downregulated PD-L1, while EDs favoring a chromatin-active state (i.e., histone deacetylase inhibitors) increased PD-L1 expression. miRNAs can regulate PD-L1 at a post-transcriptional level. miR-195/miR-16 were negatively associated with PD-L1 expression and positively correlated to longer biochemical recurrence-free survival; they also enhanced the radiotherapy efficacy in PC cell lines. miR-197 and miR-200a-c positively correlated to PD-L1 mRNA levels and inversely correlated to the methylation of PD-L1 promoter in a large series. miR-570, miR-34a and miR-513 may also be involved in epigenetic regulation.

What Do We Have to Know about PD-L1 Expression in Prostate Cancer? A Systematic Literature Review. Part 3: PD-L1, Intracellular Signaling Pathways and Tumor Microenvironment

The tumor microenvironment (TME) includes immune (T, B, NK, dendritic), stromal, mesenchymal, endothelial, adipocytic cells, extracellular matrix, and cytokines/chemokines/soluble factors regulating various intracellular signaling pathways (ISP) in tumor cells. TME influences the survival/progression of prostate cancer (PC), enabling tumor cell immune-evasion also through the activation of the PD-1/PD-L1 axis. We have performed a systematic literature review according to the PRISMA guidelines, to investigate how the PD-1/PD-L1 pathway is influenced by TME and ISPs. Tumor immune-escape mechanisms include suppression/exhaustion of tumor infiltrating cytotoxic T lymphocytes, inhibition of tumor suppressive NK cells, increase in immune-suppressive immune cells (regulatory T, M2 macrophagic, myeloid-derived suppressor, dendritic, stromal, and adipocytic cells). IFN-γ (the most investigated factor), TGF-β, TNF-α, IL-6, IL-17, IL-15, IL-27, complement factor C5a, and other soluble molecules secreted by TME components (and sometimes increased in patients' serum), as well as and hypoxia, influenced the regulation of PD-L1. Experimental studies using human and mouse PC cell lines (derived from either androgen-sensitive or androgen-resistant tumors) revealed that the intracellular ERK/MEK, Akt-mTOR, NF-kB, WNT and JAK/STAT pathways were involved in PD-L1 upregulation in PC. Blocking the PD-1/PD-L1 signaling by using immunotherapy drugs can prevent tumor immune-escape, increasing the anti-tumor activity of immune cells.

What Do We Have to Know about PD-L1 Expression in Prostate Cancer? A Systematic Literature Review. Part 1: Focus on Immunohistochemical Results with Discussion of Pre-Analytical and Interpretation Variables

Immunotherapy targeting the PD-1-PD-L1 axis yielded good results in treating different immunologically ''hot'' tumors. A phase II study revealed good therapeutic activity of pembrolizumab in selected prostatic carcinoma (PC)-patients. We performed a systematic literature review (PRISMA guidelines), which analyzes the immunohistochemical expression of PD-L1 in human PC samples and highlights the pre-analytical and interpretation variables. Interestingly, 29% acinar PCs, 7% ductal PCs, and 46% neuroendocrine carcinomas/tumors were PD-L1+ on immunohistochemistry. Different scoring methods or cut-off criteria were applied on variable specimen-types, evaluating tumors showing different clinic-pathologic features. The positivity rate of different PD-L1 antibody clones in tumor cells ranged from 3% (SP142) to 50% (ABM4E54), excluding the single case tested for RM-320. The most tested clone was E1L3N, followed by 22C3 (most used for pembrolizumab eligibility), SP263, SP142, and 28-8, which gave the positivity rates of 35%, 11-41% (depending on different scoring systems), 6%, 3%, and 15%, respectively. Other clones were tested in <200 cases. The PD-L1 positivity rate was usually higher in tumors than benign tissues. It was higher in non-tissue microarray specimens (41-50% vs. 15%), as PC cells frequently showed heterogenous or focal PD-L1-staining. PD-L1 was expressed by immune or stromal cells in 12% and 69% cases, respectively. Tumor heterogeneity, inter-institutional preanalytics, and inter-observer interpretation variability may account for result biases.