Tumor-Associated Neutrophils Dampen Adaptive Immunity and Promote Cutaneous Squamous Cell Carcinoma Development

Evidence of Neutrophils and Neutrophil Extracellular Traps in Human NMSC with Regard to Clinical Risk Factors, Ulceration and CD8+ T Cell Infiltrate

Non-melanoma skin cancers (NMSC), including basal cell carcinoma (BCC), cutaneous squamous cell carcinoma (cSCC), and Merkel cell carcinoma (MCC), are increasingly common and present significant healthcare challenges. Neutrophil extracellular traps (NETs), chromatin fibers expulsed by neutrophil granulocytes, can promote immunotherapy resistance via an impairment of CD8+ T cell-mediated cytotoxicity. Here, to identify a potential therapeutic target, we investigate the expulsion of NETs and their relation to CD8+ T cell infiltration in NMSC. Immunofluorescence staining for neutrophils (CD15) and NETs (H3cit), as well as immunohistochemistry for cytotoxic T cells (CD8+) on human cSCCs (n = 24), BCCs (n = 17) and MCCs (n = 12), revealed a correlation between neutrophil infiltration and ulceration diameter in BCC and MCC, but not in cSCC. In BCC and cSCC, neutrophil infiltration also correlated with the cross-sectional area (CSA). NETs were not associated with established risk factors but with the presence of an ulceration, and, in cSCC, with abscess-like structures. CD8+ T cell infiltration was not reduced in tumors that were NET-positive nor in those with a denser neutrophil infiltration. This study is the first to report and characterize NETs in NMSC. Thus, it gives an incentive for further research in this relevant yet understudied topic.

Cutaneous Squamous Cell Carcinoma in Patients with Solid-Organ-Transplant-Associated Immunosuppression

The management of advanced cutaneous squamous cell carcinoma (CSCC) has been revolutionized by the introduction of immunotherapy. Yet, successful treatment with immunotherapy relies on an adequate antitumor immune response. Patients who are solid-organ transplant recipients (SOTRs) have a higher incidence of CSCC compared to the general population. This review discusses the current knowledge of epidemiology, pathophysiology, and management of patients with CSCC who are immunocompromised because of their chronic exposure to immunosuppressive medications to prevent allograft rejection. First, we discuss the prognostic impact of immunosuppression in patients with CSCC. Next, we review the risk of CSCC development in immunosuppressed patients due to SOT. In addition, we provide an overview of the biological immune disruption present in transplanted immunosuppressed CSCC patients. We discuss the available evidence on the use of immunotherapy and provide a framework for the management approach with SOTRs with CSCC. Finally, we discuss potential novel approaches that are being investigated for the management of immunosuppressed patients with CSCC.

The Mutational and Microenvironmental Landscape of Cutaneous Squamous Cell Carcinoma: A Review

Cutaneous squamous cell carcinoma (cSCC) manifests through the complex interactions of UV-induced DNA damage, genetic mutations, and alterations in the tumor microenvironment. A high mutational burden is present in cSCC, as well as both cSCC precursors and normal skin, making driver genes difficult to differentiate. Despite this, several key driver genes have been identified, including TP53, the NOTCH family, CDKN2A, PIK3CA, and EGFR. In addition to mutations, the tumor microenvironment and the manipulation and evasion of the immune system play a critical role in cSCC progression. Novel therapeutic approaches, such as immunotherapy and EGFR inhibitors, have been used to target these dysregulations, and have shown promise in treating advanced cSCC cases, emphasizing the need for targeted interventions considering both genetic and microenvironmental factors for improved patient outcomes.

Repeated stress to the skin amplifies neutrophil infiltration in a keratin 17- and PKCα-dependent manner

Neutrophils are the first immune cells to reach inflamed sites and contribute to the pathogenesis of chronic inflammatory skin diseases. Yet, little is known about the pattern of neutrophil infiltration in inflamed skin in vivo and the mechanisms mediating their recruitment. Here, we provide insight into the dynamics of neutrophil infiltration in skin in response to acute or repeated inflammatory stress, highlighting a novel keratinocyte- and keratin 17 (K17)-dependent mechanism that regulates neutrophil recruitment to inflamed skin. We used the phorbol ester TPA and UVB, alone or in combination, to induce sterile inflammation in mouse skin. A single TPA treatment results in a neutrophil influx in the dermis that peaks at 12 h and resolves within 24 h. A subsequent TPA treatment or a UVB challenge, when applied 24 h but not 48 h later, accelerates, amplifies, and prolongs neutrophil infiltration. This transient amplification response (TAR) is mediated by local signals in inflamed skin, can be recapitulated in ex vivo culture, and involves the K17-dependent sustainment of protein kinase Cα (PKCα) activity and release of chemoattractants by stressed keratinocytes. K17 binds RACK1, a scaffold protein essential for PKCα activity. The N-terminal head domain of K17 is crucial for its association with RACK1 and regulation of PKCα activity. Analysis of RNAseq data reveals a signature consistent with TAR and PKCα activation in inflammatory skin diseases. These findings uncover a novel, keratin-dependent mechanism that amplifies neutrophil recruitment in skin under stress, with direct implications for inflammatory skin disorders.

Prostaglandin E2 in the Tumor Microenvironment, a Convoluted Affair Mediated by EP Receptors 2 and 4

The involvement of the prostaglandin E2 (PGE2) system in cancer progression has long been recognized. PGE2 functions as an autocrine and paracrine signaling molecule with pleiotropic effects in the human body. High levels of intratumoral PGE2 and overexpression of the key metabolic enzymes of PGE2 have been observed and suggested to contribute to tumor progression. This has been claimed for different types of solid tumors, including, but not limited to, lung, breast, and colon cancer. PGE2 has direct effects on tumor cells and angiogenesis that are known to promote tumor development. However, one of the main mechanisms behind PGE2 driving cancerogenesis is currently thought to be anchored in suppressed antitumor immunity, thus providing possible therapeutic targets to be used in cancer immunotherapies. EP2 and EP4, two receptors for PGE2, are emerging as being the most relevant for this purpose. This review aims to summarize the known roles of PGE2 in the immune system and its functions within the tumor microenvironment. SIGNIFICANCE STATEMENT: Prostaglandin E2 (PGE2) has long been known to be a signaling molecule in cancer. Its presence in tumors has been repeatedly associated with disease progression. Elucidation of its effects on immunological components of the tumor microenvironment has highlighted the potential of PGE2 receptor antagonists in cancer treatment, particularly in combination with immune checkpoint inhibitor therapeutics. Adjuvant treatment could increase the response rates and the efficacy of immune-based therapies.

A mixture-like model for tumor-immune system interactions

We introduce a mathematical model based on mixture theory intended to describe the tumor-immune system interactions within the tumor microenvironment. The equations account for the geometry of the tumor expansion, and the displacement of the immune cells, driven by diffusion and chemotactic mechanisms. They also take into account the constraints in terms of nutrient and oxygen supply. The numerical investigations analyze the impact of the different modeling assumptions and parameters. Depending on the parameters, the model can reproduce elimination, equilibrium or escape phases and it identifies a critical role of oxygen/nutrient supply in shaping the tumor growth. In addition, antitumor immune cells are key factors in controlling tumor growth, maintaining an equilibrium while protumor cells favor escape and tumor expansion.

Photodynamic Therapy and Adaptive Immunity Induced by Reactive Oxygen Species: Recent Reports

Cancer is one of the most significant causes of death worldwide. Despite the rapid development of modern forms of therapy, results are still unsatisfactory. The prognosis is further worsened by the ability of cancer cells to metastasize. Thus, more effective forms of therapy, such as photodynamic therapy, are constantly being developed. The photodynamic therapeutic regimen involves administering a photosensitizer that selectively accumulates in tumor cells or is present in tumor vasculature prior to irradiation with light at a wavelength corresponding to the photosensitizer absorbance, leading to the generation of reactive oxygen species. Reactive oxygen species are responsible for the direct and indirect destruction of cancer cells. Photodynamically induced local inflammation has been shown to have the ability to activate an adaptive immune system response resulting in the destruction of tumor lesions and the creation of an immune memory. This paper focuses on presenting the latest scientific reports on the specific immune response activated by photodynamic therapy. We present newly discovered mechanisms for the induction of the adaptive response by analyzing its various stages, and the possible difficulties in generating it. We also present the results of research over the past 10 years that have focused on improving the immunological efficacy of photodynamic therapy for improved cancer therapy.

Distinguishing Keratoacanthoma from Well-Differentiated Cutaneous Squamous Cell Carcinoma Using Single-Cell Spatial Pathology

Keratoacanthoma (KA) is a common keratinocyte neoplasm that is regularly classified as a type of cutaneous squamous cell carcinoma (cSCC) despite demonstrating benign behavior. Differentiating KA from well-differentiated cSCC is difficult in many cases due to the substantial overlap of clinical and histological features. Currently, no reliable discriminating markers have been defined, and consequently, KAs are often treated similarly to cSCC, creating unnecessary surgical morbidity and healthcare costs. In this study, we used RNA sequencing to identify key differences in transcriptomes between KA and cSCC, which suggested divergent keratinocyte populations between each tumor. Imaging mass cytometry was then used to identify single-cell tissue characteristics, including cellular phenotype, frequency, topography, functional status, and interactions between KA and well-differentiated cSCC. We found that cSCC had significantly increased proportions of Ki67+ keratinocytes among tumor keratinocytes, which were dispersed significantly throughout non-basal keratinocyte communities. In cSCC, regulatory T-cells were more prevalent and held greater suppressive capacity. Furthermore, cSCC regulatory T-cells, tumor-associated macrophages, and fibroblasts had significant associations with Ki67+ keratinocytes as opposed to avoidances with KA, indicating a more immunosuppressive environment. Our data suggest that multicellular spatial features can serve as a foundation to enhance the histological discrimination of ambiguous KA and cSCC lesions.

Keratin 17- and PKCα-dependent transient amplification of neutrophil influx after repeated stress to the skin

Neutrophils contribute to the pathogenesis of chronic inflammatory skin diseases. Little is known about the source and identity of the signals mediating their recruitment in inflamed skin. We used the phorbol ester TPA and UVB, alone or in combination, to induce sterile inflammation in mouse skin and assess whether keratinocyte-derived signals impact neutrophil recruitment. A single TPA treatment results in a neutrophil influx in the dermis that peaks at 12h and resolves within 24h. A second TPA treatment or a UVB challenge, when applied at 24h but not 48h later, accelerates, amplifies, and prolongs neutrophil infiltration. This transient amplification response (TAR) is mediated by local signals in inflamed skin, can be recapitulated in ex vivo culture, and involves the K17-dependent sustainment of protein kinase Cα (PKCα) activity and release of neutrophil chemoattractants by stressed keratinocytes. We show that K17 binds RACK1, a scaffold essential for PKCα activity. Finally, analyses of RNAseq data reveal the presence of a transcriptomic signature consistent with TAR and PKCα activation in chronic inflammatory skin diseases. These findings uncover a novel, transient, and keratin-dependent mechanism that amplifies neutrophil recruitment to the skin under stress, with direct implications for inflammatory skin disorders.

Immunity against Non-Melanoma Skin Cancer and the Effect of Immunosuppressive Medication on Non-Melanoma Skin Cancer Risk in Solid Organ Transplant Recipients

Non-melanoma skin cancers (NMSCs) occur frequently in the Caucasian population and are considered a burden for health care. Risk factors include ultraviolet (UV) radiation, ethnicity and immunosuppression. The incidence of NMSC is significantly higher in solid organ transplant recipients (SOTRs) than in immunocompetent individuals, due to immunosuppressive medication use by SOTRs. While the immunosuppressive agents, calcineurin inhibitors and purine analogues increase the incidence of NMSC in transplant recipients, mTOR inhibitors do not. This is most likely due to the different immunological pathways that are inhibited by each class of drug. This review will focus on what is currently known about the immune response against cutaneous squamous cell carcinoma (cSCC) and basal cell carcinoma (BCC), two of the main types of NMSC. Furthermore, we will describe the different classes of immunosuppressants given to SOTRs, which part of the immune system they target and how they can contribute to NMSC development. The risk of developing NMSC in SOTRs is the result of a combination of inhibiting immunological pathways involved in immunosurveillance against NMSC and the direct (pro/anti) tumor effects of immunosuppressants.

Review of the Tumor Microenvironment in Basal and Squamous Cell Carcinoma

It is widely known that tumor cells of basal and squamous cell carcinoma interact with the cellular and acellular components of the tumor microenvironment to promote tumor growth and progression. While this environment differs for basal and squamous cell carcinoma, the cellular players within both create an immunosuppressed environment by downregulating effector CD4+ and CD8+ T cells and promoting the release of pro-oncogenic Th2 cytokines. Understanding the crosstalk that occurs within the tumor microenvironment has led to the development of immunotherapeutic agents, including vismodegib and cemiplimab to treat BCC and SCC, respectively. However, further investigation of the TME will provide the opportunity to discover novel treatment options.

Molecular Alterations in Cutaneous Squamous Cell Carcinoma in Immunocompetent and Immunosuppressed Hosts-A Systematic Review

The characterization of cutaneous squamous cell carcinoma (cSCC) at the molecular level is lacking in the current literature due to the high mutational burden of this disease. Immunosuppressed patients afflicted with cSCC experience considerable morbidity and mortality. In this article, we review the molecular profile of cSCC among the immunosuppressed and immunocompetent populations at the genetic, epigenetic, transcriptomic, and proteometabolomic levels, as well as describing key differences in the tumor immune microenvironment between these two populations. We feature novel biomarkers from the recent literature which may serve as potential targets for therapy.

Neutrophil-T cell crosstalk and the control of the host inflammatory response

While fundamental in their innate role in combating infection and responding to injury, neutrophils are emerging as key modulators of adaptive immune responses. Such functions are attained via both soluble and nonsoluble effectors that enable at least two major downstream outcomes: first, to mediate and control acute inflammatory responses and second, to regulate adaptive immunity and ultimately promoting the development and maintenance of immune tolerance either by releasing immuno-modulatory factors, including cytokines, or by directly interacting with cells of the adaptive immune system. Herein, we review these novel properties of neutrophils and redefine the pathophysiological functions of these fascinating multi-tasking cells, exploring the different mechanisms through which neutrophils are able to either enhance and orchestrate T cell pro-inflammatory responses or inhibit T cell activity to maintain immune tolerance.

Targeting M2 Macrophages with a Novel NADPH Oxidase Inhibitor

ROS in cancer cells play a key role in pathways regulating cell death, stemness maintenance, and metabolic reprogramming, all of which have been implicated in resistance to chemo/ immunotherapy. Adjusting ROS levels to reverse the resistance of cancer cells without impairing normal cell functions is a new therapeutic avenue. In this paper, we describe new inhibitors of NADPH oxidase (NOX), a key enzyme in many cells of the tumor microenvironment. The first inhibitor, called Nanoshutter-1, NS1, decreased the level of tumor-promoting "M2" macrophages differentiated from human blood monocytes. NS1 disrupted the active NADPH oxidase-2 (NOX2) complex at the membrane and in the mitochondria of the macrophages, as shown by confocal microscopy. As one of the characteristics of tumor invasion is hypoxia, we tested whether NS1 would affect vascular reactivity by reducing ROS or NO levels in wire and pressure myograph experiments on isolated blood vessels. The results show that NS1 vasodilated blood vessels and would likely reduce hypoxia. Finally, as both NOX2 and NOX4 are key proteins in tumors and their microenvironment, we investigated whether NS1 would probe these proteins differently. Models of NOX2 and NOX4 were generated by homology modeling, showing structural differences at their C-terminal NADPH site, in particular in their last Phe. Thus, the NADPH site presents an unexploited chemical space for addressing ligand specificity, which we exploited to design a novel NOX2-specific inhibitor targeting variable NOX2 residues. With the proper smart vehicle to target specific cells of the microenvironment as TAMs, NOX2-specific inhibitors could open the way to new precision therapies.

A cis-regulatory lexicon of DNA motif combinations mediating cell-type-specific gene regulation

Gene expression is controlled by transcription factors (TFs) that bind cognate DNA motif sequences in cis-regulatory elements (CREs). The combinations of DNA motifs acting within homeostasis and disease, however, are unclear. Gene expression, chromatin accessibility, TF footprinting, and H3K27ac-dependent DNA looping data were generated and a random-forest-based model was applied to identify 7,531 cell-type-specific cis-regulatory modules (CRMs) across 15 diploid human cell types. A co-enrichment framework within CRMs nominated 838 cell-type-specific, recurrent heterotypic DNA motif combinations (DMCs), which were functionally validated using massively parallel reporter assays. Cancer cells engaged DMCs linked to neoplasia-enabling processes operative in normal cells while also activating new DMCs only seen in the neoplastic state. This integrative approach identifies cell-type-specific cis-regulatory combinatorial DNA motifs in diverse normal and diseased human cells and represents a general framework for deciphering cis-regulatory sequence logic in gene regulation.

Autofluorescence identifies highly phagocytic tissue-resident macrophages in mouse and human skin and cutaneous squamous cell carcinoma

Macrophages from human and mouse skin share phenotypic and functional features, but remain to be characterized in pathological skin conditions. Skin-resident macrophages are known to derive from embryonic precursors or from adult hematopoiesis. In this report, we investigated the origins, phenotypes and functions of macrophage subsets in mouse and human skin and in cutaneous squamous cell carcinoma (cSCC) using the spectral flow cytometry technology that enables cell autofluorescence to be considered as a full-fledged parameter. Autofluorescence identifies macrophage subsets expressing the CD206 mannose receptor in human peri-tumoral skin and cSCC. In mouse, all AF+ macrophages express the CD206 marker, a subset of which also displaying the TIM-4 marker. While TIM-4-CD206+ AF+ macrophages can differentiate from bone-marrow monocytes and infiltrate skin and tumor, TIM-4 identifies exclusively a skin-resident AF+ macrophage subset that can derive from prenatal hematopoiesis which is absent in tumor core. In mouse and human, AF+ macrophages from perilesional skin and cSCC are highly phagocytic cells contrary to their AF- counterpart, thus identifying autofluorescence as a bona fide marker for phagocytosis. Our data bring to light autofluorescence as a functional marker characterizing subsets of phagocytic macrophages in skin and cSCC. Autofluorescence can thus be considered as an attractive marker of function of macrophage subsets in pathological context.

Tumor-associated neutrophils and neutrophil-targeted cancer therapies

Neutrophils are the frontline cells in response to microbial infections and are involved in a range of inflammatory disorders in the body. In recent years, neutrophils have gained considerable attention in their involvement of complex roles in tumor development and progression. Tumor-associated neutrophils (TANs) that accumulate in local region could be triggered by external stimuli from tumor microenvironment (TME) and switch between anti- and pro-tumor phenotypes. The anti-tumor neutrophils kill tumor cells through direct cytotoxic effects as well as indirect effects by activating adaptive immune responses. In contrast, the pro-tumor phenotype of neutrophils might be associated with cell proliferation, angiogenesis, and immunosuppression in TME. More recently, neutrophils have been proposed as a potential target in cancer therapy for their ability to diminish the pro-tumor pathways, such as by immune checkpoint blockade. This review discusses the complex roles of neutrophils in TME and highlights the strategies in neutrophil targeting in cancer treatment with a particular focus on the progresses of ongoing clinical trials involving neutrophil-targeted therapies.

Analysis of the Equilibrium Phase in Immune-Controlled Tumors Provides Hints for Designing Better Strategies for Cancer Treatment

When it comes to improving cancer therapies, one challenge is to identify key biological parameters that prevent immune escape and maintain an equilibrium state characterized by a stable subclinical tumor mass, controlled by the immune cells. Based on a space and size structured partial differential equation model, we developed numerical methods that allow us to predict the shape of the equilibrium at low cost, without running simulations of the initial-boundary value problem. In turn, the computation of the equilibrium state allowed us to apply global sensitivity analysis methods that assess which and how parameters influence the residual tumor mass. This analysis reveals that the elimination rate of tumor cells by immune cells far exceeds the influence of the other parameters on the equilibrium size of the tumor. Moreover, combining parameters that sustain and strengthen the antitumor immune response also proves more efficient at maintaining the tumor in a long-lasting equilibrium state. Applied to the biological parameters that define each type of cancer, such numerical investigations can provide hints for the design and optimization of cancer treatments.

Lactobacillus Suppresses Tumorigenesis of Oropharyngeal Cancer via Enhancing Anti-Tumor Immune Response

Deficiency in T cell-mediated adaptive immunity, such as low CD8⁺ T cell infiltration, inhibits the immune surveillance, promotes malignant transformation, and facilitates tumor growth. Microbiota dysbiosis diminishes the immune system and contributes to the occurrence of cancer. However, the impact of oral dysbiosis on the occurrence and molecular mechanisms of oropharyngeal cancer (OPC) remains largely unknown. In the current study, we used 4-nitroquinoline-1-oxide (4NQO) to mimic tobacco-related carcinogenesis to generate a murine OPC model and determine the role of microbiota changes in OPC tumorigenesis. Our results showed that the oral flora composition of mice was deregulated during the tumorigenesis of OPC. The abundance of Streptococcus, Veillonella, Muribacter, Rodentibacter, and Gemella was increased, whereas the dominant genus Lactobacillus was gradually decreased with disease progression. We further demonstrated that infiltration of CD8⁺ T lymphocytes was markedly reduced due to the reduction of Lactobacillus. Supplementation of Lactobacillus increased the infiltration of CD8⁺ T cells, promoted the expression of IFN-γ and granzyme B, and lessened the OPC progression. Analyzing the metabolites of the Lactobacillus, we demonstrated that Lactobacillus enhanced the anti-tumor immune response by producing acetate in OPC development. Administration of acetate to mice could increase the expression of IFN-γ and IFN-γ-inducible chemokines in tumor tissues by activating GPR43 to promote the infiltration of CD8⁺ T lymphocytes and substantially delay the development of OPC. Together, our data suggest that dysbiosis of oral microbiota promotes the tumorigenesis of OPC through downregulation of cytotoxic T lymphocytes. Lactobacillus and its metabolite acetate improve the tumor microenvironment, which could be applied in the treatment of OPC.

Multi-faced roles of reactive oxygen species in anti-tumor T cell immune responses and combination immunotherapy

T cells play a central role in anti-tumor immunity, and reactive oxygen species (ROS) lie at the crossroad on the anti-tumor T cell responses. To activate efficient T cell immunity, a moderate level of ROS is needed, however, excessive ROS would cause toxicity to the T cells, because the improper level leads to the formation and maintenance of an immunosuppressive tumor microenvironment. Up to date, strategies that modulate ROS, either increasing or decreasing, have been widely investigated. Some of them are utilized in anti-tumor therapies, showing inevitable impacts on the anti-tumor T cell immunity with both obverse and reverse sides. Herein, the impacts of ROS-increasing and ROS-decreasing treatments on the T cell responses in the tumor microenvironment are reviewed and discussed. At the same time, outcomes of combination immunotherapies are introduced to put forward inspirations to unleash the potential of immunotherapies.

Pathophysiological Integration of Metabolic Reprogramming in Breast Cancer

Simple Summary

Tumors exhibit metabolic changes that differentiate them from the normal tissues from which they derive. These metabolic changes favor tumor growth, are primarily induced by cancer cells, and produce metabolic and functional changes in the surrounding stromal cells. There is a close functional connection between the metabolic changes in tumor cells and those that appear in the surrounding stroma. A better understanding of intratumoral metabolic interactions may help identify new vulnerabilities that will facilitate new, more individualized treatment strategies against cancer. We review the metabolic changes described in tumor and stromal cells and their functional changes and then consider, in depth, the metabolic interactions between the cells of the two compartments. Although these changes are generic, we illustrate them mainly with reference to examples in breast cancer.

Abstract

Metabolic changes that facilitate tumor growth are one of the hallmarks of cancer. The triggers of these metabolic changes are located in the tumor parenchymal cells, where oncogenic mutations induce an imperative need to proliferate and cause tumor initiation and progression. Cancer cells undergo significant metabolic reorganization during disease progression that is tailored to their energy demands and fluctuating environmental conditions. Oxidative stress plays an essential role as a trigger under such conditions. These metabolic changes are the consequence of the interaction between tumor cells and stromal myofibroblasts. The metabolic changes in tumor cells include protein anabolism and the synthesis of cell membranes and nucleic acids, which all facilitate cell proliferation. They are linked to catabolism and autophagy in stromal myofibroblasts, causing the release of nutrients for the cells of the tumor parenchyma. Metabolic changes lead to an interstitium deficient in nutrients, such as glucose and amino acids, and acidification by lactic acid. Together with hypoxia, they produce functional changes in other cells of the tumor stroma, such as many immune subpopulations and endothelial cells, which lead to tumor growth. Thus, immune cells favor tissue growth through changes in immunosuppression. This review considers some of the metabolic changes described in breast cancer.

Oh, the Mutations You'll Acquire! A Systematic Overview of Cutaneous Squamous Cell Carcinoma

Nearly two million cases of cutaneous squamous cell carcinoma (cSCC) are diagnosed every year in the United States alone. cSCC is notable for both its prevalence and its propensity for invasion and metastasis. For many patients, surgery is curative. However, patients experiencing immunosuppression or recurrent, advanced, and metastatic disease still face limited therapeutic options and significant mortality. cSCC forms after decades of sun exposure and possesses the highest known mutation rate of all cancers. This mutational burden complicates efforts to identify the primary factors driving cSCC initiation and progression, which in turn hinders the development of targeted therapeutics. In this review, we summarize the mutations and alterations that have been observed in patients’ cSCC tumors, affecting signaling pathways, transcriptional regulators, and the microenvironment. We also highlight novel therapeutic opportunities in development and clinical trials.

Leveling Up the Controversial Role of Neutrophils in Cancer: When the Complexity Becomes Entangled

Neutrophils are the most abundant immune cell in the circulation of human and act as gatekeepers to discard foreign elements that have entered the body. They are essential in initiating immune responses for eliminating invaders, such as microorganisms and alien particles, as well as to act as immune surveyors of cancer cells, especially during the initial stages of carcinogenesis and for eliminating single metastatic cells in the circulation and in the premetastatic organs. Since neutrophils can secrete a whole range of factors stored in their many granules as well as produce reactive oxygen and nitrogen species upon stimulation, neutrophils may directly or indirectly affect carcinogenesis in both the positive and negative directions. An intricate crosstalk between tumor cells, neutrophils, other immune cells and stromal cells in the microenvironment modulates neutrophil function resulting in both anti- and pro-tumor activities. Both the anti-tumor and pro-tumor activities require chemoattraction towards the tumor cells, neutrophil activation and ROS production. Divergence is seen in other neutrophil properties, including differential secretory repertoire and membrane receptor display. Many of the direct effects of neutrophils on tumor growth and metastases are dependent on tight neutrophil–tumor cell interactions. Among them, the neutrophil Mac-1 interaction with tumor ICAM-1 and the neutrophil L-selectin interaction with tumor-cell sialomucins were found to be involved in the neutrophil-mediated capturing of circulating tumor cells resulting in increased metastatic seeding. On the other hand, the anti-tumor function of neutrophils was found to rely on the interaction between tumor-surface-expressed receptor for advanced glycation end products (RAGE) and Cathepsin G expressed on the neutrophil surface. Intriguingly, these two molecules are also involved in the promotion of tumor growth and metastases. RAGE is upregulated during early inflammation-induced carcinogenesis and was found to be important for sustaining tumor growth and homing at metastatic sites. Cathepsin G was found to be essential for neutrophil-supported lung colonization of cancer cells. These data level up the complexity of the dual role of neutrophils in cancer.

The Role of Oncogenes and Redox Signaling in the Regulation of PD-L1 in Cancer

Tumor cells can evade the immune system via multiple mechanisms, including the dysregulation of the immune checkpoint signaling. These signaling molecules are important factors that can either stimulate or inhibit tumor immune response. Under normal physiological conditions, the interaction between programmed cell death ligand 1 (PD-L1) and its receptor, programmed cell death 1 (PD-1), negatively regulates T cell function. In cancer cells, high expression of PD-L1 plays a key role in cancer evasion of the immune surveillance and seems to be correlated with clinical response to immunotherapy. As such, it is important to understand various mechanisms by which PD-L1 is regulated. In this review article, we provide an up-to-date review of the different mechanisms that regulate PD-L1 expression in cancer. We will focus on the roles of oncogenic signals (c-Myc, EML4-ALK, K-ras and p53 mutants), growth factor receptors (EGFR and FGFR), and redox signaling in the regulation of PD-L1 expression and discuss their clinical relevance and therapeutic implications. These oncogenic signalings have common and distinct regulatory mechanisms and can also cooperatively control tumor PD-L1 expression. Finally, strategies to target PD-L1 expression in tumor microenvironment including combination therapies will be also discussed.

IFN-γ Critically Enables the Intratumoural Infiltration of CXCR3+ CD8+ T Cells to Drive Squamous Cell Carcinoma Regression

Simple Summary

Cutaneous squamous cell carcinoma (SCC) is prevalent in aged individuals and individuals with compromised or weakened immune systems, indicating a close association between immune function and SCC control. The aim of our study was to uncover the identity of key immune subsets that mediate SCC control, and to elucidate the mechanistic role of the proinflammatory cytokine Interferon-gamma in this process. We established a SCC regressor model, which we used to determine that: (1) CD8⁺ T cells, not CD4⁺ T cells or NK cells, are essential for SCC regression; (2) the neutralisation of Interferon-gamma prevents CD8⁺ T cell infiltration and SCC regression; (3) CD8⁺ T cell migration into SCC critically depends upon Interferon-gamma-induced chemokine expression. Thus, our model can be used to understand the key immune mechanisms involved in SCC regression, which will support targeted investigations into the integrity of these mechanisms in patients with progressive disease.

Abstract

Ultraviolet (UV) radiation-induced tumours carry a high mutational load, are highly immunogenic, and often fail to grow when transplanted into normal, syngeneic mice. The aim of this study was to investigate factors critical for the immune-mediated rejection of cutaneous squamous cell carcinoma (SCC). In our rejection model, transplanted SCC establish and grow in mice immunosuppressed with tacrolimus. When tacrolimus is withdrawn, established SCC tumours subsequently undergo immune-mediated tumour rejection. Through the depletion of individual immune subsets at the time of tacrolimus withdrawal, we established a critical role for CD8⁺ T cells, but not CD4⁺ T cells, γδ T cells, or NK cells, in driving the regression of SCC. Regression was critically dependent on IFN-γ, although IFN-γ was not directly cytotoxic to SCC cells. IFN-γ-neutralisation abrogated SCC regression, significantly reduced CD8⁺ T cell-infiltration into SCC, and significantly impaired the secretion of CXCL9, CXCL10 and CCL5 within the tumour microenvironment. A strong positive correlation was revealed between CXCL10 expression and CD8⁺ T cell abundance in tumours. Indeed, blockade of the CXCL10 receptor CXCR3 at the time of tacrolimus withdrawal prevented CD8⁺ T cell infiltration and the regression of SCC. Chimeric models revealed an important role for immune cells as producers of IFN-γ, but not as recipients of IFN-γ signals via the IFN-γ receptor. Together, these findings suggest a key role for IFN-γ in driving the expression of chemokines within the tumour environment essential for the destruction of established SCC by CD8⁺ T cells.

Cutaneous Squamous Cell Carcinoma Development Is Associated with a Temporal Infiltration of ILC1 and NK Cells with Immune Dysfunctions

NK cells and tissue-resident innate lymphoid cells (ILCs) are innate effectors found in the skin. To investigate their temporal dynamics and specific functions throughout the development of cutaneous squamous cell carcinoma (cSCC), we combined transcriptomic and immunophenotyping analyses in mouse and human cSCCs. We identified an infiltration of NK cells and ILC1s as well as the presence of a few ILC3s. Adoptive transfer of NK cells in NK cell‒ and ILC-deficient Nfil3^-/- mice revealed a role for NK cells in early control of cSCC. During tumor progression, we identified a population skewing with the infiltration of atypical ILC1 secreting inflammatory cytokines but reduced levels of IFN-γ at the papilloma stage. NK cells and ILC1s were functionally impaired, with reduced cytotoxicity and IFN-γ secretion associated with the downregulation of activating receptors. They also showed a high degree of heterogeneity in mouse and human cSCCs with the expression of several markers of exhaustion, including TIGIT on NK cells and PD-1 and TIM-3 on ILC1s. Our data show an enrichment in inflammatory ILC1 at the precancerous stage together with impaired antitumor functions in NK cells and ILC1 that could contribute to the development of cSCC and thus suggest that future immunotherapies should take both ILC populations into account.

The Tumor Microenvironment in SCC: Mechanisms and Therapeutic Opportunities

Squamous cell carcinoma (SCC) is the second most common skin cancer worldwide and, despite the relatively easy visualization of the tumor in the clinic, a sizeable number of SCC patients are diagnosed at advanced stages with local invasion and distant metastatic lesions. In the last decade, immunotherapy has emerged as the fourth pillar in cancer therapy via the targeting of immune checkpoint molecules such as programmed cell-death protein-1 (PD-1), programmed cell death ligand-1 (PD-L1), and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4). FDA-approved monoclonal antibodies directed against these immune targets have provide survival benefit in a growing list of cancer types. Currently, there are two immunotherapy drugs available for cutaneous SCC: cemiplimab and pembrolizumab; both monoclonal antibodies (mAb) that block PD-1 thereby promoting T-cell activation and/or function. However, the success rate of these checkpoint inhibitors currently remains around 50%, which means that half of the patients with advanced SCC experience no benefit from this treatment. This review will highlight the mechanisms by which the immune checkpoint molecules regulate the tumor microenvironment (TME), as well as the ongoing clinical trials that are employing single or combinatory therapeutic approaches for SCC immunotherapy. We also discuss the regulation of additional pathways that might promote superior therapeutic efficacy, and consequently provide increased survival for those patients that do not benefit from the current checkpoint inhibitor therapies.

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.

A20 regulates the therapeutic effect of anti-PD-1 immunotherapy in melanoma

Background

The therapeutic effect of immune checkpoint blockers, especially the neutralizing antibodies of programmed cell death (PD-1) and its ligand programmed death ligand 1 (PD-L1), has been well verified in melanoma. Nevertheless, the dissatisfactory response rate and the occurrence of resistance significantly hinder the treatment effect. Inflammation-related molecules like A20 are greatly implicated in cancer immune response, but the role of tumorous A20 in antitumor immunity and immunotherapy efficacy remains elusive.

Methods

The association between tumorous A20 expression and the effect of anti-PD-1 immunotherapy was determined by immunoblotting, immunofluorescence staining and flow cytometry analysis of primary tumor specimens from melanoma patients. Preclinical mouse model, in vitro coculture system, immunohistochemical staining and flow cytometry analysis were employed to investigate the role of A20 in regulating the effect of anti-PD-1 immunotherapy. Bioinformatics, mass spectrum analysis and a set of biochemical analyzes were used to figure out the underlying mechanism.

Results

We first discovered that upregulated A20 was associated with impaired antitumor capacity of CD8⁺T cells and poor response to anti-PD-1 immunotherapy in melanoma patients. Subsequent functional studies in preclinical mouse model and in vitro coculture system proved that targeting tumorous A20 prominently improved the effect of immunotherapy through the invigoration of infiltrating CD8⁺T cells via the regulation of PD-L1. Mechanistically, A20 facilitated the ubiquitination and degradation of prohibitin to potentiate STAT3 activation and PD-L1 expression. Moreover, tumorous A20 expression was highly associated with the ratio of Ki-67 percentage in circulating PD-1⁺CD8⁺T cells to tumor burden.

Conclusions

Together, our findings uncover a novel crosstalk between inflammatory molecules and antitumor immunity in melanoma, and highlight that A20 can be exploited as a promising target to bring clinical benefit to melanomas refractory to immune checkpoint blockade.