PD-1 Blunts the Function of Ovarian Tumor-Infiltrating Dendritic Cells by Inactivating NF-κB

Recent advances in the mechanisms of PD-L1 expression in gastric cancer: a review

In the progression of gastric cancer (GC), various cell types in the tumor microenvironment (TME) exhibit upregulated expression of programmed death ligand 1 (PD-L1), leading to impaired T-cell function and evasion of immune surveillance. Infection with H. pylori and EBV leads to increased PD-L1 expression in various cell types within TME, resulting in immune suppression and facilitating immune escape of GC cells. In the TME, mesenchymal stem cells (MSCs), M1-like tumor-associated macrophages (MI-like TAM), and myeloid-derived suppressor cells (MDSCs) contribute to the upregulation of PD-L1 expression in GC cells. Conversely, mast cells, M2-like tumor-associated macrophages (M2-like TAM), and tumor-associated neutrophils (TANs) exhibit elevated levels of PD-L1 expression in response to the influence of GC cells. Together, these factors collectively contribute to the upregulation of PD-L1 expression in GC. This review aims to provide a comprehensive summary of the cellular expression patterns of PD-L1 in GC and the underlying molecular mechanisms. Understanding the complex regulatory pathways governing PD-L1 expression may offer novel insights for the development of effective immunotherapeutic interventions.

Overcoming chimeric antigen receptor-T (CAR-T) resistance with checkpoint inhibitors: Existing methods, challenges, clinical success, and future prospects : A comprehensive review

Immune checkpoint blockade is, as of today, the most successful form of cancer immunotherapy, with more than 43 % of cancer patients in the US eligible to receive it; however, only up to 12.5 % of patients respond to it. Similarly, adoptive cell therapy using bioengineered chimeric antigen receptorT (CAR-T) cells and T-cell receptor (TCR) cells has provided excellent responses against liquid tumours, but both forms of immunotherapy have encountered challenges within a tumour microenvironment that is both lacking in tumour-specific T-cells and is strongly immunosuppressive toward externally administered CAR-T and TCR cells. This review focuses on understanding approved checkpoint blockade and adoptive cell therapy at both biological and clinical levels before delving into how and why their combination holds significant promise in overcoming their individual shortcomings. The advent of next-generation checkpoint inhibitors has further strengthened the immune checkpoint field, and a special section explores how these inhibitors can address existing hurdles in combining checkpoint blockade with adoptive cell therapy and homing in on our cancer target for long-term immunity.

NF-κB signaling and the tumor microenvironment in osteosarcoma: implications for immune evasion and therapeutic resistance

Osteosarcoma, a highly aggressive malignancy with a generally poor prognosis, is characterized by tumor cells' ability to evade immune responses and resist treatment. The nuclear transcription factor NF-κB signaling pathway is crucial in regulating inflammatory and immune reactions. It occupies a central position in the development of the osteosarcoma tumor microenvironment. This research aimed to explore how NF-κB influences the recruitment and polarization of tumor-associated macrophages and myeloid-derived suppressor cells, both of which contribute to immunosuppression. Furthermore, NF-κB facilitates immune surveillance evasion in osteosarcoma cells by altering the expression of immune checkpoint molecules, such as PD-L1. It also enhances tumor cell resistance to chemotherapy and radiotherapy by activating anti-apoptotic signaling pathways and exacerbating treatment-induced inflammation. Potential therapeutic approaches include using NF-κB inhibitors, possibly in combination with immune checkpoint inhibitors, to overcome tumor cell resistance mechanisms and reshape antitumor immune responses. A thorough examination of NF-κB's role in osteosarcoma development is expected to yield novel clinical treatment strategies, and significantly improve patient prognosis by targeting this key signaling pathway.

Amelioration of experimental autoimmune encephalomyelitis by exogenous soluble PD-L1 is associated with restraining dendritic cell maturation and CCR7-mediated migration

Dendritic cells (DCs) orchestrate both immune activation and immune tolerance in multiple sclerosis (MS). Manipulating the phenotypes and functions of DCs to boost their tolerogenic potential is an appealing strategy for treating MS and its animal model experimental autoimmune encephalomyelitis (EAE). Programmed cell death 1 (PD-1) delivers the immunoinhibitory signals by interacting with PD-1 ligand 1 (PD-L1), which plays a critical role in maintaining immune tolerance. So far, the effects of PD-1/PD-L1 signalling activation on DCs in EAE are poorly understood. Here, the administration of soluble PD-L1 (sPD-L1) protein significantly alleviated the clinical symptoms of myelin oligodendrocyte glycoprotein (MOG)-induced EAE, and inhibited the expression of cluster of differentiation (CD)86, C-C motif chemokine receptor 7 (CCR7) as well as CCR7-mediated trafficking of splenic DCs, accompanied by enhancing their phagocytosis. The impact of sPD-L1 on the surface morphology and mechanical properties of DCs was investigated at the nanoscale, using scanning electron microscope and atomic force microscope. The treatment of sPD-L1 was found to mitigate morphological maturation and biomechanical alterations, specifically in terms of adhesion and elasticity, in bone marrow-derived DCs from EAE. Taken together, our findings suggest that application of exogenous sPD-L1 has a marked suppressive effect on the maturation and migration of DCs in EAE. PD-L1 administration may be a promising therapy for EAE and for MS in the future.

NF-κB role on tumor proliferation, migration, invasion and immune escape

Nuclear factor kappa-B (NF-κB) is a nuclear transcription factor that plays a key factor in promoting inflammation, which can lead to the development of cancer in a long-lasting inflammatory environment. The activation of NF-κB is essential in the initial phases of tumor development and progression, occurring in both pre-malignant cells and cells in the microenvironment such as phagocytes, T cells, and B cells. In addition to stimulating angiogenesis, inhibiting apoptosis, and promoting the growth of tumor cells, NF-κB activation also causes the epithelial-mesenchymal transition, and tumor immune evasion. Therapeutic strategies that focus on immune checkpoint molecules have revolutionized cancer treatment by enabling the immune system to activate immunological responses against tumor cells. This review focused on understanding the NF-κB signaling pathway in the context of cancer.

Cell Identity and Spatial Distribution of PD-1/PD-L1 Blockade Responders

The programmed death 1 (PD-1)/programmed death ligand 1 (PD-L1) axis inhibits T cell activity, impairing anti-tumor immunity. Blocking this axis with therapeutic antibodies is one of the most promising anti-tumor immunotherapies. It has long been recognized that PD-1/PD-L1 blockade reinvigorates exhausted T (TEX) cells already present in the tumor microenvironment (TME). However, recent advancements in high-throughput gene sequencing and bioinformatic tools have provided researchers with a more granular and dynamic insight into PD-1/PD-L1 blockade-responding cells, extending beyond the TME and TEX populations. This review provides an update on the cell identity, spatial distribution, and treatment-induced spatiotemporal dynamics of PD-1/PD-L1 blockade responders. It also provides a synopsis of preliminary reports of potential PD-1/PD-L1 blockade responders other than T cells to depict a panoramic picture. Important questions to answer in further studies and the translational and clinical potential of the evolving understandings are also discussed.

NF-κB signaling pathway in tumor microenvironment

The genesis and progression of tumors are multifaceted processes influenced by genetic mutations within the tumor cells and the dynamic interplay with their surrounding milieu, which incessantly impacts the course of cancer. The tumor microenvironment (TME) is a complex and dynamic entity that encompasses not only the tumor cells but also an array of non-cancerous cells, signaling molecules, and the extracellular matrix. This intricate network is crucial in tumor progression, metastasis, and response to treatments. The TME is populated by diverse cell types, including immune cells, fibroblasts, endothelial cells, alongside cytokines and growth factors, all of which play roles in either suppressing or fostering tumor growth. Grasping the nuances of the interactions within the TME is vital for the advancement of targeted cancer therapies. Consequently, a thorough understanding of the alterations of TME and the identification of upstream regulatory targets have emerged as a research priority. NF-κB transcription factors, central to inflammation and innate immunity, are increasingly recognized for their significant role in cancer onset and progression. This review emphasizes the crucial influence of the NF-κB signaling pathway within the TME, underscoring its roles in the development and advancement of cancer. By examining the interactions between NF-κB and various components of the TME, targeting the NF-κB pathway appears as a promising cancer treatment approach.

High-dimensional mapping of human CEACAM1 expression on immune cells and association with melanoma drug resistance

BACKGROUND

Human carcinoembryonic antigen cell adhesion molecule 1 (CEACAM1) is an inhibitory cell surface protein that functions through homophilic and heterophilic ligand binding. Its expression on immune cells in human tumors is poorly understood.

METHODS

An antibody that distinguishes human CEACAM1 from other highly related CEACAM family members was labeled with 159Tb and inserted into a panel of antibodies that included specificity for programmed cell death protein 1 (PD1) and PD-L1, which are targets of immunotherapy, to gain a data-driven immune cell atlas using cytometry by time-of-flight (CyTOF). A detailed inventory of CEACAM1, PD1, and PD-L1 expression on immune cells in metastatic lesions to lymph node or soft tissues and peripheral blood samples from patients with treatment-naive and -resistant melanoma as well as peripheral blood samples from healthy controls was performed.

RESULTS

CEACAM1 is absent or at low levels on healthy circulating immune cells but is increased on immune cells in peripheral blood and tumors of melanoma patients. The majority of circulating PD1-positive NK cells, innate T cells, B cells, monocytic cells, dendritic cells, and CD4+ T cells in the peripheral circulation of treatment-resistant disease co-express CEACAM1 and are demonstrable as discrete populations. CEACAM1 is present on distinct types of cells that are unique to the tumor microenvironment and exhibit expression levels that are highest in treatment resistance; this includes tumor-infiltrating CD8+ T cells.

CONCLUSIONS

To the best of our knowledge, this work represents the first comprehensive atlas of CEACAM1 expression on immune cells in a human tumor and reveals an important correlation with treatment-resistant disease. These studies suggest that agents targeting CEACAM1 may represent appropriate partners for PD1-related pathway therapies.

PD-1: A critical player and target for immune normalization

Immune system imbalances contribute to the pathogenesis of several different diseases, and immunotherapy shows great therapeutic efficacy against tumours and infectious diseases with immune-mediated derivations. In recent years, molecules targeting the programmed cell death protein 1 (PD-1) immune checkpoint have attracted much attention, and related signalling pathways have been studied clearly. At present, several inhibitors and antibodies targeting PD-1 have been utilized as anti-tumour therapies. However, increasing evidence indicates that PD-1 blockade also has different degrees of adverse side effects, and these new explorations into the therapeutic safety of PD-1 inhibitors contribute to the emerging concept that immune normalization, rather than immune enhancement, is the ultimate goal of disease treatment. In this review, we summarize recent advancements in PD-1 research with regard to immune normalization and targeted therapy.

Regulation of Tumor Dendritic Cells by Programmed Cell Death 1 Pathways

The advent of immune checkpoint blockade therapy has revolutionized cancer treatments and is partly responsible for the significant decline in cancer-related mortality observed during the last decade. Immune checkpoint inhibitors, such as anti-programmed cell death 1 (PD-1)/programmed cell death ligand 1 (PD-L1), have demonstrated remarkable clinical successes in a subset of cancer patients. However, a considerable proportion of patients remain refractory to immune checkpoint blockade, prompting the exploration of mechanisms of treatment resistance. Whereas much emphasis has been placed on the role of PD-L1 and PD-1 in regulating the activity of tumor-infiltrating T cells, recent studies have now shown that this immunoregulatory axis also directly regulates myeloid cell activity in the tumor microenvironment including tumor-infiltrating dendritic cells. In this review, I discuss the most recent advances in the understanding of how PD-1, PD-L1, and programmed cell death ligand 2 regulate the function of tumor-infiltrating dendritic cells, emphasizing the need for further mechanistic studies that could facilitate the development of novel combination immunotherapies for improved cancer patient benefit.

Tyrosine phosphatase PTPN11/SHP2 in solid tumors - bull's eye for targeted therapy?

Encoded by PTPN11, the Src-homology 2 domain-containing phosphatase 2 (SHP2) integrates signals from various membrane-bound receptors such as receptor tyrosine kinases (RTKs), cytokine and integrin receptors and thereby promotes cell survival and proliferation. Activating mutations in the PTPN11 gene may trigger signaling pathways leading to the development of hematological malignancies, but are rarely found in solid tumors. Yet, aberrant SHP2 expression or activation has implications in the development, progression and metastasis of many solid tumor entities. SHP2 is involved in multiple signaling cascades, including the RAS-RAF-MEK-ERK-, PI3K-AKT-, JAK-STAT- and PD-L1/PD-1- pathways. Although not mutated, activation or functional requirement of SHP2 appears to play a relevant and context-dependent dichotomous role. This mostly tumor-promoting and infrequently tumor-suppressive role exists in many cancers such as gastrointestinal tumors, pancreatic, liver and lung cancer, gynecological entities, head and neck cancers, prostate cancer, glioblastoma and melanoma. Recent studies have identified SHP2 as a potential biomarker for the prognosis of some solid tumors. Based on promising preclinical work and the advent of orally available allosteric SHP2-inhibitors early clinical trials are currently investigating SHP2-directed approaches in various solid tumors, either as a single agent or in combination regimes. We here provide a brief overview of the molecular functions of SHP2 and collate current knowledge with regard to the significance of SHP2 expression and function in different solid tumor entities, including cells in their microenvironment, immune escape and therapy resistance. In the context of the present landscape of clinical trials with allosteric SHP2-inhibitors we discuss the multitude of opportunities but also limitations of a strategy targeting this non-receptor protein tyrosine phosphatase for treatment of solid tumors.

Alpha-fetoprotein upregulates hepatocellular carcinoma cell-intrinsic PD-1 expression through the LATS2/YAP/TEAD1 pathway

BACKGROUND

Hepatocellular carcinoma (HCC) cell-intrinsic programmed death 1 (PD-1) promotes tumor progression. However, the mechanisms that regulate its expression are unclear. This study investigated the impact of alpha-fetoprotein (AFP) on HCC cell-intrinsic PD-1 expression.

METHODS

The expression of PD-1 and AFP at the gene and protein levels was detected using real-time fluorescence quantitative polymerase chain reaction (RT-qPCR) and western blotting (WB). Proteins interacting with AFP were examined by co-immunoprecipitation (CO-IP). Chromatin immunoprecipitation (ChIP) and dual luciferase reporter assays were used to identify transcription-enhanced association domain 1 (TEAD1) binding to the promoter of PD-1.

RESULTS

The expression of HCC cell-intrinsic PD-1 was positively correlated with AFP. Mechanistically, AFP inhibited the phosphorylation of large tumor suppressor 2 (LATS2) and yes-associated protein (YAP). As a result, YAP is transferred to the nucleus and forms a transcriptional complex with TEAD1, promoting PD-1 transcription by binding to its promoter.

CONCLUSION

AFP is an upstream regulator of the HCC cell-intrinsic PD-1 and increases PD-1 expression via the LATS2/YAP/TEAD1 axis.

GENERAL

Our findings provide insight into the mechanisms of HCC development and offer new ideas for further in-depth studies of HCC.

AXL receptor tyrosine kinase inhibition improves the anti-tumor effects of CD8+ T cells by inducing CD103+ dendritic cell-mediated T cell priming

AXL is a member of TAM receptor family and has been highlighted as a potential target for cancer treatment. Accumulating evidence has uncovered the critical role of the AXL signaling pathway in tumor growth, metastasis, and resistance against anti-cancer drugs, as well as its association with cancer immune escape. However, the function of AXL as a manipulator of the immune system in the tumor microenvironment (TME) remains unclear. Therefore, in this study, we investigated the impact of AXL on immune cells in the TME of a syngeneic tumor model using AXL knockout (AXL-/-) mice. Compared to AXL wild-type (AXL+/+) mice, tumor growth was significantly suppressed in AXL-/- mice, and an induced population of tumor-infiltrated CD8+ T cells and CD103+ dendritic cells (DCs) was observed. The change of CD8+ T cells and CD103+ DCs was also confirmed in tumor-draining lymph nodes (TdLN). In addition, the clonal expansion of OVA-specific CD8+ T cells was dominant in AXL-/- mice. Finally, anti-PD-1 treatment evidenced synergistic anti-cancer effects in AXL-/- mice. Overall, our data indicate that AXL signaling may inhibit the clonal expansion of tumor-specific CD8+ T cells through the regulation of the migration of CD8+ T cells and DCs in TME. Thus, AXL may be a powerful molecular target to improve anti-cancer effects through single or combined therapy with immune checkpoint inhibitors (ICI).

A novel bivalent anti-c-MET/PD-1 bispecific antibody exhibits potent cytotoxicity against c-MET/PD-L1-positive colorectal cancer

Previously, we generated a novel bispecific antibody (BsAb) simultaneously targeting both c-MET and PD-1 (PDCD1), which can bridge T cells and c-MET positive tumor cells. However, the specific mechanisms and antitumor activities of the BsAb against c-MET/PD-L1 (CD274) positive colorectal cancer (CRC) is not completely understood. In this study, in addition to the tumor intrinsic mechanism investigation with molecular biology assay in vitro, a humanized mouse model was used to evaluate antitumor activity of the BsAb in vivo. The BsAb could inhibit c-MET/PD-L1+ CRC cell migration and show strong antitumor activity against HCT116 tumors in mice, potentially by inducing the degradation of c-MET protein in a dose and time-dependent manner. The BsAb could suppress the phosphorylation of c-MET downstream proteins GRB2-associated-binding protein 1 (Gab1) and focal adhesion kinase (FAK). Considering the tumor extrinsic mechanism, the BsAb may promote phagocytosis of macrophage. Furthermore, the level of plasma exosomal-c-MET/PD-L1 is able to distinguish CRC patients from healthy controls. In summary, the BsAb exhibited potent anti-tumor activities by two distinguished mechanisms: inhibition of c-MET signal transduction and promotion of macrophage-mediated phagocytosis. Our BsAb may provide a novel therapeutic agent for patients with c-MET/PD-L1+ CRC, and the status of exosomal-c-MET/PD-L1 can serve as a biomarker to predict responsiveness to treatment of our BsAb.

NF-κB: a mediator that promotes or inhibits angiogenesis in human diseases?

The nuclear factor of κ-light chain of enhancer-activated B cells (NF-κB) signaling pathway, which is conserved in invertebrates, plays a significant role in human diseases such as inflammation-related diseases and carcinogenesis. Angiogenesis refers to the growth of new capillary vessels derived from already existing capillaries and postcapillary venules. Maintaining normal angiogenesis and effective vascular function is a prerequisite for the stability of organ tissue function, and abnormal angiogenesis often leads to a variety of diseases. It has been suggested that NK-κB signalling molecules under pathological conditions play an important role in vascular differentiation, proliferation, apoptosis and tumourigenesis by regulating the transcription of multiple target genes. Many NF-κB inhibitors are being tested in clinical trials for cancer treatment and their effect on angiogenesis is summarised. In this review, we will summarise the role of NF-κB signalling in various neovascular diseases, especially in tumours, and explore whether NF-κB can be used as an attack target or activation medium to inhibit tumour angiogenesis.

Advances in PD-1 signaling inhibition-based nano-delivery systems for tumor therapy

In recent years, cancer immunotherapy has emerged as an exciting cancer treatment. Immune checkpoint blockade brings new opportunities for more researchers and clinicians. Programmed cell death receptor-1 (PD-1) is a widely studied immune checkpoint, and PD-1 blockade therapy has shown promising results in a variety of tumors, including melanoma, non-small cell lung cancer and renal cell carcinoma, which greatly improves patient overall survival and becomes a promising tool for the eradication of metastatic or inoperable tumors. However, low responsiveness and immune-related adverse effects currently limit its clinical application. Overcoming these difficulties is a major challenge to improve PD-1 blockade therapies. Nanomaterials have unique properties that enable targeted drug delivery, combination therapy through multidrug co-delivery strategies, and controlled drug release through sensitive bonds construction. In recent years, combining nanomaterials with PD-1 blockade therapy to construct novel single-drug-based or combination therapy-based nano-delivery systems has become an effective mean to address the limitations of PD-1 blockade therapy. In this study, the application of nanomaterial carriers in individual delivery of PD-1 inhibitors, combined delivery of PD-1 inhibitors and other immunomodulators, chemotherapeutic drugs, photothermal reagents were reviewed, which provides effective references for designing new PD-1 blockade therapeutic strategies.

Emerging phagocytosis checkpoints in cancer immunotherapy

Cancer immunotherapy, mainly including immune checkpoints-targeted therapy and the adoptive transfer of engineered immune cells, has revolutionized the oncology landscape as it utilizes patients' own immune systems in combating the cancer cells. Cancer cells escape immune surveillance by hijacking the corresponding inhibitory pathways via overexpressing checkpoint genes. Phagocytosis checkpoints, such as CD47, CD24, MHC-I, PD-L1, STC-1 and GD2, have emerged as essential checkpoints for cancer immunotherapy by functioning as "don't eat me" signals or interacting with "eat me" signals to suppress immune responses. Phagocytosis checkpoints link innate immunity and adaptive immunity in cancer immunotherapy. Genetic ablation of these phagocytosis checkpoints, as well as blockade of their signaling pathways, robustly augments phagocytosis and reduces tumor size. Among all phagocytosis checkpoints, CD47 is the most thoroughly studied and has emerged as a rising star among targets for cancer treatment. CD47-targeting antibodies and inhibitors have been investigated in various preclinical and clinical trials. However, anemia and thrombocytopenia appear to be formidable challenges since CD47 is ubiquitously expressed on erythrocytes. Here, we review the reported phagocytosis checkpoints by discussing their mechanisms and functions in cancer immunotherapy, highlight clinical progress in targeting these checkpoints and discuss challenges and potential solutions to smooth the way for combination immunotherapeutic strategies that involve both innate and adaptive immune responses.

Expression and T cell regulatory action of the PD-1 immune checkpoint in the ovary and fallopian tube

PROBLEM

Immune cell trafficking and surveillance within the ovary and fallopian tube are thought to impact fertility and also tumorigenesis in those organs. However, little is known of how native cells of the ovary and fallopian tube interact with resident immune cells. Interaction of the Programmed Cell Death Protein-1 (PD-1/PDCD-1/CD279) checkpoint with PD-L1 is associated with downregulated immune response. We have begun to address the question of whether PD-1 ligand or its receptors (PD-L1/-L2) can regulate immune cell function in these tissues of the female reproductive tract.

METHOD OF STUDY

PD-1 and ligand protein expression was evaluated in human ovary and fallopian tube specimens, the latter of which included stages of tubal cell transformation and early tumorigenesis. Ovarian expression analysis included the determination of the proteins in human follicular fluid (HFF) specimens collected during in vitro fertilization procedures. Finally, checkpoint bioactivity of HFF was determined by treatment of separately-isolated human T cells and the measurement of interferon gamma (IFNγ).

RESULTS

We show that membrane bound and soluble variants of PD-1 and ligands are expressed by permanent constituent cell types of the human ovary and fallopian tube, including granulosa cells and oocytes. PD-1 and soluble ligands were present in HFF at bioactive levels that control T cell PD-1 activation and IFNγ production; full-length checkpoint proteins were found to be highly enriched in HFF exosome fractions.

CONCLUSION

The detection of PD-1 checkpoint proteins in the human ovary and fallopian tube suggests that the pathway is involved in immunomodulation during folliculogenesis, the window of ovulation, and subsequent egg and embryo immune-privilege. Immunomodulatory action of receptor and ligands in HFF exosomes is suggestive of an acute checkpoint role during ovulation. This is the first study in the role of PD-1 checkpoint proteins in human tubo-ovarian specimens and the first examination of its potential regulatory action in the contexts of normal and assisted reproduction.

Inflammatory cytokine-enriched microenvironment plays key roles in the development of breast cancers

As the incidence of breast cancer continues to increase, it is critical to develop prevention strategies for this disease. Inflammation underlies the onset of the disease, and NF-κB is a master transcription factor for inflammation. Nuclear factor-κB (NF-κB) is activated in a variety of cell types, including normal epithelial cells, cancer cells, cancer-associated fibroblasts (CAFs), and immune cells. Ductal carcinoma in situ (DCIS) is the earliest stage of breast cancer, and not all DCIS lesions develop into invasive breast cancers (IBC). Currently, most patients with DCIS undergo surgery with postoperative therapy, although there is a risk of overtreatment. In BRCA mutants, receptor activator of NF-κB (RANK)-positive progenitors serve as the cell of origin, and treatment using the RANK monoclonal antibody reduces the risk of IBC. There is still an unmet need to diagnose malignant DCIS, which has the potential to progress to IBC, and to establish appropriate prevention strategies. We recently demonstrated novel molecular mechanisms for NF-κB activation in premalignant mammary tissues, which include DCIS, and the resultant cytokine-enriched microenvironment is essential for breast cancer development. On the early endosomes in a few epithelial cells, the adaptor protein FRS2β, forming a complex with ErbB2, carries the IκB kinase (IKK) complex and leads to the activation of NF-κB, thereby inducing a variety of cytokines. Therefore, the FRS2β-NFκB axis in the inflammatory premalignant environment could be targetable to prevent IBC. Further analysis of the molecular mechanisms of inflammation in the premalignant microenvironment is necessary to prevent the risk of IBC.

Protein kinase Cι mediates immunosuppression in lung adenocarcinoma

Lung adenocarcinoma (LUAD) is the most prevalent form of non-small cell lung cancer (NSCLC) and a leading cause of cancer death. Immune checkpoint inhibitors (ICIs) of programmed death-1/programmed death-ligand 1 (PD-1/PD-L1) signaling induce tumor regressions in a subset of LUAD, but many LUAD tumors exhibit resistance to ICI therapy. Here, we identified Prkci as a major determinant of response to ICI in a syngeneic mouse model of oncogenic mutant Kras/Trp53 loss (KP)-driven LUAD. Protein kinase Cι (PKCι)-dependent KP tumors exhibited resistance to anti-PD-1 antibody therapy (α-PD-1), whereas KP tumors in which Prkci was genetically deleted (KPI tumors) were highly responsive. Prkci-dependent resistance to α-PD-1 was characterized by enhanced infiltration of myeloid-derived suppressor cells (MDSCs) and decreased infiltration of CD8+ T cells in response to α-PD-1. Mechanistically, Prkci regulated YAP1-dependent expression of Cxcl5, which served to attract MDSCs to KP tumors. The PKCι inhibitor auranofin inhibited KP tumor growth and sensitized these tumors to α-PD-1, whereas expression of either Prkci or its downstream effector Cxcl5 in KPI tumors induced intratumoral infiltration of MDSCs and resistance to α-PD-1. PRKCI expression in tumors of patients with LUAD correlated with genomic signatures indicative of high YAP1-mediated transcription, elevated MDSC infiltration and low CD8+ T cell infiltration, and with elevated CXCL5/6 expression. Last, PKCι-YAP1 signaling was a biomarker associated with poor response to ICI in patients with LUAD. Our data indicate that immunosuppressive PKCι-YAP1-CXCL5 signaling is a key determinant of response to ICI, and pharmacologic inhibition of PKCι may improve therapeutic response to ICI in patients with LUAD.

The depths of PD-1 function within the tumor microenvironment beyond CD8+ T cells

Programmed cell death-1 (PD-1; CD279) is a cell surface receptor that is expressed in both innate and adaptive immune cells. The role of PD-1 in adaptive immune cells, specifically in CD8+ T cells, has been thoroughly investigated but its significance in other immune cells is yet to be well established. This review will address the role of PD-1 based therapies in enhancing non-CD8+ T cell immune responses within cancer. Specifically, the expression and function of PD-1 in non-CD8+ immune cell compartments such as CD4+ T helper cell subsets, myeloid cells and innate lymphoid cells (ILCs) will be discussed. By understanding the immune cell specific function of PD-1 within tissue resident innate and adaptive immune cells, it will be possible to stratify patients for PD-1 based therapies for both immunogeneic and non-immunogeneic neoplastic disorders. With this knowledge from fundamental and translational studies, PD-1 based therapies can be utilized to enhance T cell independent immune responses in cancers.

Immune cellular components and signaling pathways in the tumor microenvironment

During the past decade there has been a revolution in cancer therapeutics by the emergence of antibody-based and cell-based immunotherapies that modulate immune responses against tumors. These new therapies have extended and improved the therapeutic efficacy of chemo-radiotherapy and have offered treatment options to patients who are no longer responding to these classic anti-cancer treatments. Unfortunately, tumor eradication and long-lasting responses are observed in a small fraction of patients, whereas the majority of patients respond only transiently. These outcomes indicate that the maximum potential of immunotherapy has not been reached due to incomplete knowledge of the cellular and molecular mechanisms that guide the development of successful anti-tumor immunity and its failure. In this review, we discuss recent discoveries about the immune cellular composition of the tumor microenvironment (TME) and the role of key signaling mechanisms that compromise the function of immune cells leading to cancer immune escape.

MAPK Signaling Pathway in Oral Squamous Cell Carcinoma: Biological Function and Targeted Therapy

Oral squamous cell carcinoma accounts for 95% of human head and neck squamous cell carcinoma cases. It is highly malignant and aggressive, with a poor prognosis and a 5-year survival rate of <50%. In recent years, basic and clinical studies have been performed on the role of the mitogen-activated protein kinase (MAPK) signaling pathway in oral cancer. The MAPK signaling pathway is activated in over 50% of human oral cancer cases. Herein, we review research progress on the MAPK signaling pathway and its potential therapeutic mechanisms and discuss its molecular targeting to explore its potential as a therapeutic strategy for oral squamous cell carcinoma.

A comprehensive review of SHP2 and its role in cancer

Src homology 2-containing protein tyrosine phosphatase 2 (SHP2) is a non-receptor protein tyrosine phosphatase ubiquitously expressed mainly in the cytoplasm of several tissues. SHP2 modulates diverse cell signaling events that control metabolism, cell growth, differentiation, cell migration, transcription and oncogenic transformation. It interacts with diverse molecules in the cell, and regulates key signaling events including RAS/ERK, PI3K/AKT, JAK/STAT and PD-1 pathways downstream of several receptor tyrosine kinases (RTKs) upon stimulation by growth factors and cytokines. SHP2 acts as both a phosphatase and a scaffold, and plays prominently oncogenic functions but can be tumor suppressor in a context-dependent manner. It typically acts as a positive regulator of RTKs signaling with some inhibitory functions reported as well. SHP2 expression and activity is regulated by such factors as allosteric autoinhibition, microRNAs, ubiquitination and SUMOylation. Dysregulation of SHP2 expression or activity causes many developmental diseases, and hematological and solid tumors. Moreover, upregulated SHP2 expression or activity also decreases sensitivity of cancer cells to anticancer drugs. SHP2 is now considered as a compelling anticancer drug target and several classes of SHP2 inhibitors with different mode of action are developed with some already in clinical trial phases. Moreover, novel SHP2 substrates and functions are rapidly growing both in cell and cancer. In view of this, we comprehensively and thoroughly reviewed literatures about SHP2 regulatory mechanisms, substrates and binding partners, biological functions, roles in human cancers, and different classes of small molecule inhibitors target this oncoprotein in cancer.

Therapeutic Targeting of Macrophage Plasticity Remodels the Tumor-Immune Microenvironment

SIGNIFICANCE

Comprehensive single-cell proteomics analyses of lung adenocarcinoma progression reveal the role of tumor-associated macrophages in resistance to PD-1 blockade therapy. See related commentary by Lee et al., p. 2515.

Noncanonical PD-1/PD-L1 Axis in Relation to the Efficacy of Anti-PD Therapy

With programmed death 1/ligand 1 (PD-1/PD-L1) as the cornerstone, anti-PD antibodies have pioneered revolutionary immunotherapies for malignancies. But most patients struggled to respond to anti-PD owing to primary or acquired resistance or even hyperprogression, pointing to more efforts needed to explore this axis. PD-1 constrains T-cell immunoreactivity via engaging with PD-L1 of tumor/myeloid cells is the canonical PD-1/PD-L1 axis function mode. Studies are increasingly aware of the impact of noncanonical PD-1/PD-L1 expression in various cancers. PD-L1 induced on activated T-cells ligates to PD-1 to mediate self-tolerance or acts on intratumoral myeloid cells and other T-cells, affecting their survival, differentiation and immunophenotyping, leading to tumor immunosuppression. Myeloid PD-1 interferes with their proliferation, differentiation, cytokine secretion and phagocytosis, mediating remarkable pro-tumor effects. Tumor cell intrinsic PD-1 signaling has diverse functions in different tumors, resulting in pro-proliferation or proliferation inhibition. These nonclassical PD-1/PD-L1 functions may be novel anti-PD mechanisms or causes of treatment resistance. This review highlights the nonnegligible role of T-cell-intrinsic PD-L1 and tumor/myeloid PD-1 in the cell interplay network and the complex impact on the efficacy of anti-PD antibodies. Reconsidering and rational utilization of the comprehensive PD-1/PD-L1 axis could cumulate breakthroughs in precision treatment and combination for anti-PD therapies.

Harnessing anti-tumor and tumor-tropism functions of macrophages via nanotechnology for tumor immunotherapy

Reprogramming the immunosuppressive tumor microenvironment by modulating macrophages holds great promise in tumor immunotherapy. As a class of professional phagocytes and antigen-presenting cells in the innate immune system, macrophages can not only directly engulf and clear tumor cells, but also play roles in presenting tumor-specific antigen to initiate adaptive immunity. However, the tumor-associated macrophages (TAMs) usually display tumor-supportive M2 phenotype rather than anti-tumor M1 phenotype. They can support tumor cells to escape immunological surveillance, aggravate tumor progression, and impede tumor-specific T cell immunity. Although many TAMs-modulating agents have shown great success in therapy of multiple tumors, they face enormous challenges including poor tumor accumulation and off-target side effects. An alternative solution is the use of advanced nanostructures, which not only can deliver TAMs-modulating agents to augment therapeutic efficacy, but also can directly serve as modulators of TAMs. Another important strategy is the exploitation of macrophages and macrophage-derived components as tumor-targeting delivery vehicles. Herein, we summarize the recent advances in targeting and engineering macrophages for tumor immunotherapy, including (1) direct and indirect effects of macrophages on the augmentation of immunotherapy and (2) strategies for engineering macrophage-based drug carriers. The existing perspectives and challenges of macrophage-based tumor immunotherapies are also highlighted.

Immune Cells in Hyperprogressive Disease under Immune Checkpoint-Based Immunotherapy

Immunotherapy, an antitumor therapy designed to activate antitumor immune responses to eliminate tumor cells, has been deeply studied and widely applied in recent years. Immune checkpoint inhibitors (ICIs) are capable of preventing the immune responses from being turned off before tumor cells are eliminated. ICIs have been demonstrated to be one of the most effective and promising tumor treatments and significantly improve the survival of patients with multiple tumor types. However, low effective rates and frequent atypical responses observed in clinical practice limit their clinical applications. Hyperprogressive disease (HPD) is an unexpected phenomenon observed in immune checkpoint-based immunotherapy and is a challenge facing clinicians and patients alike. Patients who experience HPD not only cannot benefit from immunotherapy, but also experience rapid tumor progression. However, the mechanisms of HPD remain unclear and controversial. This review summarized current findings from cell experiments, animal studies, retrospective studies, and case reports, focusing on the relationships between various immune cells and HPD and providing important insights for understanding the pathogenesis of HPD.

Immunomodulatory Properties of Immune Checkpoint Inhibitors-More than Boosting T-Cell Responses?

The approval of immune checkpoint inhibitors (ICI) that serve to enhance effector T-cell anti-tumor responses has strongly improved success rates in the treatment of metastatic melanoma and other tumor types. The currently approved ICI constitute monoclonal antibodies blocking cytotoxic T-lymphocyte-associated protein (CTLA)-4 and anti-programmed cell death (PD)-1. By this, the T-cell-inhibitory CTLA-4/CD80/86 and PD-1/PD-1L/2L signaling axes are inhibited. This leads to sustained effector T-cell activity and circumvents the immune evasion of tumor cells, which frequently upregulate PD-L1 expression and modulate immune checkpoint molecule expression on leukocytes. As a result, profound clinical responses are observed in 40-60% of metastatic melanoma patients. Despite the pivotal role of T effector cells for triggering anti-tumor immunity, mounting evidence indicates that ICI efficacy may also be attributable to other cell types than T effector cells. In particular, emerging research has shown that ICI also impacts innate immune cells, such as myeloid cells, natural killer cells and innate lymphoid cells, which may amplify tumoricidal functions beyond triggering T effector cells, and thus improves clinical efficacy. Effects of ICI on non-T cells may additionally explain, in part, the character and extent of adverse effects associated with treatment. Deeper knowledge of these effects is required to further develop ICI treatment in terms of responsiveness of patients to treatment, to overcome resistance to ICI and to alleviate adverse effects. In this review we give an overview into the currently known immunomodulatory effects of ICI treatment in immune cell types other than the T cell compartment.

Control of Dendritic Cell Function Within the Tumour Microenvironment

The tumour microenvironment (TME) presents a major block to anti-tumour immune responses and to effective cancer immunotherapy. The inflammatory mediators such as cytokines, chemokines, growth factors and prostaglandins generated in the TME alter the phenotype and function of dendritic cells (DCs) that are critical for a successful adaptive immune response against the growing tumour. In this mini review we discuss how tumour cells and the surrounding stroma modulate DC maturation and trafficking to impact T cell function. Fibroblastic stroma and the associated extracellular matrix around tumours can also provide physical restrictions to infiltrating DCs and other leukocytes. We discuss interactions between the inflammatory TME and infiltrating immune cell function, exploring how the inflammatory TME affects generation of T cell-driven anti-tumour immunity. We discuss the open question of the relative importance of antigen-presentation site; locally within the TME versus tumour-draining lymph nodes. Addressing these questions will potentially increase immune surveillance and enhance anti-tumour immunity.

Immunological control of ovarian carcinoma by chemotherapy and targeted anticancer agents

At odds with other solid tumors, epithelial ovarian cancer (EOC) is poorly sensitive to immune checkpoint inhibitors (ICIs), largely reflecting active immunosuppression despite CD8⁺ T cell infiltration at baseline. Accumulating evidence indicates that both conventional chemotherapeutics and targeted anticancer agents commonly used in the clinical management of EOC not only mediate a cytostatic and cytotoxic activity against malignant cells, but also drive therapeutically relevant immunostimulatory or immunosuppressive effects. Here, we discuss such an immunomodulatory activity, with a specific focus on molecular and cellular pathways that can be harnessed to develop superior combinatorial regimens for clinical EOC care.

Accumulation of dysfunctional tumor-infiltrating PD-1+ DCs links PD-1/PD-L1 blockade immunotherapeutic response in cervical cancer

Various predictive biomarkers are needed to select candidates for optimal and individualized treatments. Tumor‐infiltrating immune cells have gained increasing interest in cancer research for the prediction of therapeutic response and survival. However, the role of dendritic cells (DCs) in PD-1 blockade immunotherapy remains unclear. In this study, we identified a population of PD-1+ DCs in the tumor microenvironment (TME) of cervical cancer (CC). The accumulation of PD-1+ DCs in cervical tumors was correlated with advanced stages, elevated preoperative squamous cell carcinoma antigen levels and lymph-vascular space invasion. PD-1 expression was induced on activated tumor-associated DCs (TADCs) in vitro compared with their resting counterparts. This PD-1+ DC population was characterized by reduced secretion of cytokines (IL-12, TNF-α, and IL-1β) and dysfunctional induction of T cell proliferation and cytotoxic reaction. PD-1 blockade significantly reinvigorated PD-1+ DCs to release IL-12, TNF-α, and IL-1β compared with PD-1- DCs. TILs from samples with higher PD-1+ DC infiltration could be induced to achieve a greater killing effect of PD-1 blockade treatment. Our findings suggested a role for PD-1+ DCs in immune surveillance dysfunction and CC progression. PD-1+ DC density in the TME may serve as a diagnostic factor for predicting the optimal beneficiaries of PD-1/PD-L1 blockade immunotherapy in CC.

What Happens to the Immune Microenvironment After PD-1 Inhibitor Therapy?

The fruitful results of tumor immunotherapy establish its indispensable status in the regulation of the tumorous immune context. It seems that the treatment of programmed cell death receptor 1 (PD-1) blockade is one of the most promising approaches for cancer control. The significant efficacy of PD-1 inhibitor therapy has been made in several cancer types, such as breast cancer, lung cancer, and multiple myeloma. Even so, the mechanisms of how anti-PD-1 therapy takes effect by impacting the immune microenvironment and how partial patients acquire the resistance to PD-1 blockade have yet to be studied. In this review, we discuss the cross talk between immune cells and how they promote PD-1 blockade efficacy. In addition, we also depict factors that may underlie tumor resistance to PD-1 blockade and feasible solutions in combination with it.

Differential Role of PD-1 Expressed by Various Immune and Tumor Cells in the Tumor Immune Microenvironment: Expression, Function, Therapeutic Efficacy, and Resistance to Cancer Immunotherapy

In the tumor immune microenvironment (TIME), tumor cells interact with various cells and operate various strategies to avoid antitumor immune responses. These immune escape strategies often make the TIME resistant to cancer immunotherapy. Neutralizing immune escape strategies is necessary to overcome resistance to cancer immunotherapy. Immune checkpoint receptors (ICRs) expressed in effector immune cells inhibit their effector function via direct interaction with immune checkpoint ligands (ICLs) expressed in tumor cells. Therefore, blocking ICRs or ICLs has been developed as a promising cancer immunotherapy by reinvigorating the function of effector immune cells. Among the ICRs, programmed cell death 1 (PD-1) has mainly been antagonized to enhance the survival of human patients with cancer by restoring the function of tumor-infiltrating (TI) CD8⁺ T cells. It has been demonstrated that PD-1 is expressed not only in TI CD8⁺ T cells, but also in other TI immune cells and even tumor cells. While PD-1 suppresses the function of TI CD8⁺ T cells, it is controversial whether PD-1 suppresses or amplifies the suppressive function of TI-suppressive immune cells (e.g., regulatory T cells, tumor-associated macrophages, and myeloid cells). There is also controversy regarding the role of tumor-expressing PD-1. Therefore, a precise understanding of the expression pattern and function of PD-1 in each cell subset is important for improving the efficacy of cancer immunotherapy. Here, we review the differential role of PD-1 expressed by various TI immune cells and tumor cells. We focused on how cell-type-specific ablation or blockade of PD-1 affects tumor growth in a murine tumor model. Furthermore, we will also describe how the blockade of PD-1 acts on TI immune cells in human patients with cancer.

NF-κB signaling in inflammation and cancer

Since nuclear factor of κ-light chain of enhancer-activated B cells (NF-κB) was discovered in 1986, extraordinary efforts have been made to understand the function and regulating mechanism of NF-κB for 35 years, which lead to significant progress. Meanwhile, the molecular mechanisms regulating NF-κB activation have also been illuminated, the cascades of signaling events leading to NF-κB activity and key components of the NF-κB pathway are also identified. It has been suggested NF-κB plays an important role in human diseases, especially inflammation-related diseases. These studies make the NF-κB an attractive target for disease treatment. This review aims to summarize the knowledge of the family members of NF-κB, as well as the basic mechanisms of NF-κB signaling pathway activation. We will also review the effects of dysregulated NF-κB on inflammation, tumorigenesis, and tumor microenvironment. The progression of the translational study and drug development targeting NF-κB for inflammatory diseases and cancer treatment and the potential obstacles will be discussed. Further investigations on the precise functions of NF-κB in the physiological and pathological settings and underlying mechanisms are in the urgent need to develop drugs targeting NF-κB for inflammatory diseases and cancer treatment, with minimal side effects.

Parameters of Tumor Microenvironment Determine Effectiveness of Anti-PD-1/PD-L1 Therapy

Undoubtedly, one of the most promising approaches to the treatment of cancer is creation of the pathogenetically based therapeutic drugs. Researchers from all over the world are trying to answer the question on how to select a target that would be effective and, in general, they are quite successful at that. The Nobel Prize-winning discovery of mechanisms for regulating activity of the immune system cells through checkpoint molecules, as well as discovery of the ability of tumor cells to use these mechanisms to suppress immune responses was an impetus for the development of modern immunotherapy, and now such inhibitors of the immune checkpoints as PD-1/PD-L1 are included in the routine chemotherapy. Use of such drugs can prolong the patient's life, but, unfortunately, not cure the disease. This is partially due to heterogeneity of tumor cells and microenvironment, but the main reasons may be in the complex relationships between the tumor and microenvironment, which, at times, are so plastic that they can change, adjusting to newly emerging conditions. Main characteristic of the tumor microenvironment is the type of the ongoing immune-inflammatory response (IIR), and since inhibitors of the immune checkpoints act on the cells involved in IIR, it is obvious that the outcomes of cancer therapy, including outcomes of hyperprogressive disease, can be associated with this parameter. The presented review reveals the essence of interactions between the tumor and its microenvironment during therapy with PD-L1 inhibitors.

The PD-1 Interactome

T cell activation is a fine-tuned process that involves T cell receptor and costimulation signals. To prevent undue activation of T cells, inhibitory molecules including PD-1 (programmed death 1) are induced and function as brakes for T cell signaling. In a steady state, the interaction of PD-1 with its ligands PD-L1 (B7-H1, CD274) and PD-L2 (B7-DC, CD273) maintains peripheral immune tolerance. However, the expression of PD-L1 on tumor cells and interaction with PD-1 on T cells dampen anti-tumor immunity. Therapeutic inhibitors of the PD-1 pathway have revolutionized tumor immunotherapy. Unfortunately, the majority of patients do not develop sustained anti-tumor responses. However, the knowledge about unique PD-1 interactions and their role in mediating PD-1 inhibitory signals is currently limited. Advances in the mechanistic understanding of the molecular and signaling integration of the PD-1 pathway could unleash the great potential in tumor immunotherapy by allowing the development of combinatorial approaches that target not only PD-1 and its ligands but also its unique downstream signal mediators. In this review, the current advances in understanding the mechanisms of extracellular and intracellular PD-1 interactions and their significance in potential future therapeutic approaches are discussed.

Gut microbiota-mediated immunomodulation in tumor

Tumor immunity consists of various types of cells, which serve an important role in antitumor therapy. The gastrointestinal tract is colonized by trillions of microorganisms, which form the gut microbiota. In addition to pathogen defense and maintaining the intestinal ecosystem, gut microbiota also plays a pivotal role in various physiological processes. Recently, the association between these symbionts and cancer, ranging from oncogenesis and cancer progression to resistance or sensitivity to antitumor therapies, has attracted much attention. Metagenome analysis revealed a significant difference between the gut microbial composition of cancer patients and healthy individuals. Moreover, modulation of microbiome could improve therapeutic response to immune checkpoint inhibitors (ICIs). These findings suggest that microbiome is involved in cancer pathogenesis and progression through regulation of tumor immunosurveillance, although the exact mechanisms remain largely unknown. This review focuses on the interaction between the microbiome and tumor immunity, with in-depth discussion regarding the therapeutic potential of modulating gut microbiota in ICIs. Further investigations are warranted before gut microbiota can be introduced into clinical practice.

Putting the brakes on phagocytosis: "don't-eat-me" signaling in physiology and disease

Timely removal of dying or pathogenic cells by phagocytes is essential to maintaining host homeostasis. Phagocytes execute the clearance process with high fidelity while sparing healthy neighboring cells, and this process is at least partially regulated by the balance of "eat-me" and "don't-eat-me" signals expressed on the surface of host cells. Upon contact, eat-me signals activate "pro-phagocytic" receptors expressed on the phagocyte membrane and signal to promote phagocytosis. Conversely, don't-eat-me signals engage "anti-phagocytic" receptors to suppress phagocytosis. We review the current knowledge of don't-eat-me signaling in normal physiology and disease contexts where aberrant don't-eat-me signaling contributes to pathology.

PD-1 Immune Checkpoint Inhibitor Therapy Malignant Tumor Based on Monotherapy and Combined Treatment Research

Recently, immunotherapy has become the fourth pillar of cancer treatment in addition to surgery therapy, chemotherapy, and radiation therapy. The inhibitors of programed cell death protein 1 (PD-1) and its ligand PD-L1 are the new stars in immunotherapy, as they can overcome tumor immunosuppression. However, the efficacy of PD-1 inhibitors still needs to be further developed for clinical treatment. Therefore, research into treatment with anti-PD-1 drugs has emerged as a new development field. This review provides novel insights into the role and mechanism of PD-1 combination anti-tumor therapy, thereby promoting its clinical application in anti-tumor immunotherapy.

PKD3 promotes metastasis and growth of oral squamous cell carcinoma through positive feedback regulation with PD-L1 and activation of ERK-STAT1/3-EMT signalling

Oral squamous cell carcinoma (OSCC) has a high incidence of metastasis. Tumour immunotherapy targeting PD-L1 or PD-1 has been revolutionary; however, only a few patients with OSCC respond to this treatment. Therefore, it is essential to gain insights into the molecular mechanisms underlying the growth and metastasis of OSCC. In this study, we analysed the expression levels of protein kinase D3 (PKD3) and PD-L1 and their correlation with the expression of mesenchymal and epithelial markers. We found that the expression of PKD3 and PD-L1 in OSCC cells and tissues was significantly increased, which correlated positively with that of mesenchymal markers but negatively with that of epithelial markers. Silencing PKD3 significantly inhibited the growth, metastasis and invasion of OSCC cells, while its overexpression promoted these processes. Our further analyses revealed that there was positive feedback regulation between PKD3 and PD-L1, which could drive EMT of OSCC cells via the ERK/STAT1/3 pathway, thereby promoting tumour growth and metastasis. Furthermore, silencing PKD3 significantly inhibited the expression of PD-L1, and lymph node metastasis of OSCC was investigated with a mouse footpad xenograft model. Thus, our findings provide a theoretical basis for targeting PKD3 as an alternative method to block EMT for regulating PD-L1 expression and inhibiting OSCC growth and metastasis.

LAG-3 is expressed on a majority of tumor infiltrating lymphocytes in pediatric Hodgkin lymphoma

LAG-3, through interaction with a variety of ligands, regulates T cell function via inhibition of T cell proliferation and activation. It has been demonstrated to be overexpressed on tumor infiltrating lymphocytes (TILs) of a variety of cancers with associated poor outcomes. The purpose of this study is to characterize the expression pattern and clinical significance of LAG-3 in pediatric Hodgkin lymphoma (HL). Patient tumor samples from Children's Oncology Group clinical trial AHOD0031 with matched patient outcome data were analyzed for the expression of LAG-3 and PD-L1 using immunohistochemistry. 73/115 patients (63%) demonstrated positive LAG-3 staining. No demographic or survival outcome data were significantly associated with LAG-3 expression. Interestingly, patients with the lowest density of expression were found to have the worst EFS, and those with highest density of expression demonstrated the best EFS. There was a positive statistically significant relationship between presence of LAG-3 and PD-L1 expression. This project is innovative in its characterization of LAG-3 as an immune checkpoint target in pediatric HL.

Non-canonical PD-1 signaling in cancer and its potential implications in clinic

Programmed cell death 1 (PD-1)-based immunotherapy has revolutionized the treatment of various cancers. However, only a certain group of patients benefit from PD-1 blockade therapy and many patients succumb to hyperprogressive disease. Although, CD8 T cells and conventional T cells are generally considered to be the primary source of PD-1 in cancer, accumulating evidence suggests that other distinct cell types, including B cells, regulatory T cells, natural killer cells, dendritic cells, tumor-associated macrophages and cancer cells, also express PD-1. Hence, the response of patients with cancer to PD-1 blockade therapy is a cumulative effect of anti-PD-1 antibodies acting on a myriad of cell types. Although, the contribution of CD8 T cells to PD-1 blockade therapy has been well-established, recent studies also suggest the involvement of non-canonical PD-1 signaling in blockade therapy. This review discusses the role of non-canonical PD-1 signaling in distinct cell types and explores how the available knowledge can improve PD-1 blockade immunotherapy, particularly in identifying novel biomarkers and combination treatment strategies.

NF-κB in Cancer Immunity: Friend or Foe?

The emergence of immunotherapies has definitely proven the tight relationship between malignant and immune cells, its impact on cancer outcome and its therapeutic potential. In this context, it is undoubtedly critical to decipher the transcriptional regulation of these complex interactions. Following early observations demonstrating the roles of NF-κB in cancer initiation and progression, a series of studies converge to establish NF-κB as a master regulator of immune responses to cancer. Importantly, NF-κB is a family of transcriptional activators and repressors that can act at different stages of cancer immunity. In this review, we provide an overview of the selective cell-intrinsic contributions of NF-κB to the distinct cell types that compose the tumor immune environment. We also propose a new view of NF-κB targeting drugs as a new class of immunotherapies for cancer.

Inactivation of the PD-1-Dependent Immunoregulation in Mice Exacerbates Contact Hypersensitivity Resembling Immune-Related Adverse Events

Blockade of PD-1, an indispensable physiological immunoregulatory mechanism, enhances immune activities and is widely used in the immunotherapy of cancer. This treatment often accompanies inflammatory complication called immune-related adverse events (irAE), most frequently in the skin. To analyze how skin inflammation develops by the blockade of PD-1-dependent immunoregulation, we studied the exacerbation of oxazolone-induced contact hypersensitivity by PD-L1 blockade. The inactivation of PD-1 signaling enhanced swelling of the skin with massive CD8⁺ T cell infiltration. Among PD-1-expressing cells, T cells were the predominant targets of anti-PD-L1 mAb treatment since PD-L1 blockade did not affect skin inflammation in RAG2^-/- mice. PD-L1 blockade during immunization with oxazolone significantly promoted the development of hapten-reactive T cells in the draining lymph nodes. The enhancement of local CD8⁺ T cell-dominant immune responses by PD-L1 blockade was correlated with the upregulation of CXCL9 and CXCL10. Challenges with a low dose of oxazolone did not demonstrate any significant dermatitis; however, the influence of PD-L1 blockade on T cell immunity was strong enough to cause the emergence of notable dermatitis in this suboptimal dosing, suggesting its relevance to dermal irAE development. In the low-dose setting, the blockade of CXCR3, receptor of CXCL9/10, prevented the induction of T cell-dominant inflammation by anti-PD-L1 mAb. This experimental approach reproduced CD8⁺ T cell-dominant form of cutaneous inflammation by the blockade of PD-L1 that has been observed in dermal irAE in human patients.

Cancer Cells Resistance Shaping by Tumor Infiltrating Myeloid Cells

Interactions between malignant cells and neighboring stromal and immune cells profoundly shape cancer progression. New forms of therapies targeting these cells have revolutionized the treatment of cancer. However, in order to specifically address each population, it was essential to identify and understand their individual roles in interaction between malignant cells, and the formation of the tumor microenvironment (TME). In this review, we focus on the myeloid cell compartment, a prominent, and heterogeneous group populating TME, which can initially exert an anti-tumoral effect, but with time actively participate in disease progression. Macrophages, dendritic cells, neutrophils, myeloid-derived suppressor cells, mast cells, eosinophils, and basophils act alone or in concert to shape tumor cells resistance through cellular interaction and/or release of soluble factors favoring survival, proliferation, and migration of tumor cells, but also immune-escape and therapy resistance.

CXCL9 secreted by tumor-associated dendritic cells up-regulates PD-L1 expression in bladder cancer cells by activating the CXCR3 signaling

Background

Tumor-associated dendritic cells (TADCs) can interact with tumor cells to suppress anti-tumor T cell immunity. However, there is no information on whether and how TADCs can modulate programmed death-ligand 1 (PD-L1) expression by cancer cells.

Methods

Human peripheral blood monocytes were induced for DCs and immature DCs were cultured alone, or co-cultured with bladder cancer T24 or control SV-HUC-1 cells, followed by stimulating with LPS for DC activation. The activation status of DCs was characterized by flow cytometry and allogenic T cell proliferation. The levels of chemokines in the supernatants of co-cultured DCs were measured by CBA-based flow cytometry. The impacts of CXCL9 on PD-L1, STAT3 and Akt expression and STAT3 and Akt phosphorylation in T24 cells were determined by flow cytometry and Western blot.

Results

Compared with the control DCs, TADCs exhibited immature phenotype and had significantly lower capacity to stimulate allogenic T cell proliferation, particularly in the presence of recombinant CXCL9. TADCs produced significantly higher levels of CXCL9, which enhanced PD-L1 expression in T24 cells. Pre-treatment with AMG487 abrogated the CXCL9-increased PD-L1 expression in T24 cells. Treatment with CXCL9 significantly enhanced STAT3 and Akt activation in T24 cells.

Conclusions

TADCs produced high levels of CXCL9 that increased PD-L1 expression in bladder cancer T24 cells by activating the CXCR3-related signaling. Our findings may shed new lights in understanding the regulatory roles of TADCs in inhibiting antitumor T cell responses and promoting tumor growth.

Rethinking immune checkpoint blockade: 'Beyond the T cell'

The clinical success of immune checkpoint inhibitors has highlighted the central role of the immune system in cancer control. Immune checkpoint inhibitors can reinvigorate anti-cancer immunity and are now the standard of care in a number of malignancies. However, research on immune checkpoint blockade has largely been framed with the central dogma that checkpoint therapies intrinsically target the T cell, triggering the tumoricidal potential of the adaptive immune system. Although T cells undoubtedly remain a critical piece of the story, mounting evidence, reviewed herein, indicates that much of the efficacy of checkpoint therapies may be attributable to the innate immune system. Emerging research suggests that T cell-directed checkpoint antibodies such as anti-programmed cell death protein-1 (PD-1) or programmed death-ligand-1 (PD-L1) can impact innate immunity by both direct and indirect pathways, which may ultimately shape clinical efficacy. However, the mechanisms and impacts of these activities have yet to be fully elucidated, and checkpoint therapies have potentially beneficial and detrimental effects on innate antitumor immunity. Further research into the role of innate subsets during checkpoint blockade may be critical for developing combination therapies to help overcome checkpoint resistance. The potential of checkpoint therapies to amplify innate antitumor immunity represents a promising new field that can be translated into innovative immunotherapies for patients fighting refractory malignancies.

Comprehensive Phenotyping of Dendritic Cells in Cancer Patients by Flow Cytometry

Dendritic cells (DCs) play a crucial role in the complex interplay between tumor cells and the immune system. During the elimination phase of cancer immunoediting, immunostimulatory DCs are critical for the control of tumor growth. During the escape phase, regulatory DCs sustain tumor tolerance and contribute to the development of the immunosuppressive tumor microenvironment that characterizes this phase. Moreover, increasing evidence indicates that DCs are also critical for the success of cancer immunotherapy. Hence, there is increasing need to fully characterize DC subsets and their activatory/inhibitory profile in cancer patients. In this review, we describe the role played by different DC subsets in the different phases of cancer immunoediting, the function exerted by different activatory and inhibitory molecules expressed on DC surface, and the cytokines produced by distinct DC subsets, in order to provide an overview on the DC features that may be useful to be assessed when dealing with the flow cytometric characterization of DCs in cancer patients. © 2020 International Society for Advancement of Cytometry.

Mechanisms of hyperprogressive disease after immune checkpoint inhibitor therapy: what we (don't) know

Immune checkpoint inhibitors (ICIs) have made a breakthrough in the treatment of different types of tumors, leading to improvement in survival, even in patients with advanced cancers. Despite the good clinical results, a certain percentage of patients do not respond to this kind of immunotherapy. In addition, in a fraction of nonresponder patients, which can vary from 4 to 29% according to different studies, a paradoxical boost in tumor growth after ICI administration was observed: a completely unpredictable novel pattern of cancer progression defined as hyperprogressive disease. Since this clinical phenomenon has only been recently described, a universally accepted clinical definition is lacking, and major efforts have been made to uncover the biological bases underlying hyperprogressive disease. The lines of research pursued so far have focused their attention on the study of the immune tumor microenvironment or on the analysis of intrinsic genomic characteristics of cancer cells producing data that allowed us to formulate several hypotheses to explain this detrimental effect related to ICI therapy. The aim of this review is to summarize the most important works that, to date, provide important insights that are useful in understanding the mechanistic causes of hyperprogressive disease.