The emerging role of the gut microbiome in cancer cell plasticity and therapeutic resistance

Resistance to therapeutic agents is one of the major challenges in cancer therapy. Generally, the focus is given to the genetic driver, especially the genetic mutation behind the therapeutic resistance. However, non-mutational mechanisms, such as epigenetic modifications, and TME alteration, which is mainly driven by cancer cell plasticity, are also involved in therapeutic resistance. The concept of plasticity mainly relies on the conversion of non-cancer stem cells (CSCs) to CSCs or epithelial-to-mesenchymal transition via different mechanisms and various signaling pathways. Cancer plasticity plays a crucial role in therapeutic resistance as cancer cells are able to escape from therapeutics by shifting the phenotype and thereby enhancing tumor progression. New evidence suggests that gut microbiota can change cancer cell characteristics by impacting the mechanisms involved in cancer plasticity. Interestingly, gut microbiota can also influence the therapeutic efficacy of anticancer drugs by modulating the mechanisms involved in cancer cell plasticity. The gut microbiota has been shown to reduce the toxicity of certain clinical drugs. Here, we have documented the critical role of the gut microbiota on the therapeutic efficacy of existing anticancer drugs by altering the cancer plasticity. Hence, the extended knowledge of the emerging role of gut microbiota in cancer cell plasticity can help to develop gut microbiota-based novel therapeutics to overcome the resistance or reduce the toxicity of existing drugs. Furthermore, to improve the effectiveness of therapy, it is necessary to conduct more clinical and preclinical research to fully comprehend the mechanisms of gut microbiota.

UCA1 Inhibits NKG2D-mediated Cytotoxicity of NK Cells to Breast Cancer

BACKGROUND

Natural killer cells play important roles in tumor immune surveillance, and cancer cells must resist this surveillance in order to progress and metastasise.

INTRODUCTION

The study aimed to explore the mechanism of how breast cancer cells become resistant to the cytotoxicity of NK cells.

METHODS

We established NK-resistant breast cancer cells by exposing MDA-MB-231 cells and MCF-7 cells to NK92 cells. Profiles of lncRNA were compared between the NK-resistant and parental cell lines. Primary NK cells were isolated by MACS, and the NK attacking effect was tested by non-radioactive cytotoxicity. The change in lncRNAs was analyzed by Gene-chip. The interaction between lncRNA and miRNA was displayed by Luciferase assay. The regulation of the gene was verified by QRT-PCR and WB. The clinical indicators were detected by ISH, IH, and ELISA, respectively.

RESULTS

UCA1 was found to be significantly up-regulated in both NK-resistant cell lines, and we confirmed such up-regulation on its own to be sufficient to render parental cell lines resistant to NK92 cells. We found that UCA1 up-regulated ULBP2 via the transcription factor CREB1, while it up-regulated ADAM17 by "sponging" the miR-26b-5p. ADAM17 facilitated the shedding of soluble ULBP2 from the surface of breast cancer cells, rendering them resistant to killing by NK cells. UCA1, ADAM17, and ULBP2 were found to be expressed at higher levels in bone metastases of breast cancer than in primary tumors.

CONCLUSION

Our data strongly suggest that UCA1 up-regulates ULBP2 expression and shedding, rendering breast cancer cells resistant to killing by NK cells.

Tumor immunology meets oncology (TIMO) XVII, April 20-22 2023 in Halle/Saale, Germany

During the TIMO meeting 2023, national and international scientists as well as clinicians gave novel insights as well as perspectives into basic and translational tumor immunology. https://dgfi.org/arbeitskreise/ak-tumorimmunologie/meeting/.

Exosomes as a modulator of immune resistance in human cancers

In the tumor microenvironment (TME), exosomes secreted by cells form interactive networks between the tumor cells and immune cells, thereby regulating immune signaling cascades in the TME. As key messengers of cell-to-cell communication in the TME, exosomes not only take charge of tumor cell antigen presentation to the immune cells, but also regulate the activities of immune cells, inhibit immune function, and, especially, promote immune resistance, all of which affects the therapeutic outcomes of tumors. Exosomes, which are small-sized vesicles, possess some remarkable advantages, including strong biological activity, a lack of immunogenicity and toxicity, and a strong targeting ability. Based on these characteristics, research on exosomes as biomarkers or carriers of tumor therapeutic drugs has become a research hotspot in related fields. This review describes the role of exosomes in cell communications in the TME, summarizes the effectiveness of exosome-based immunotherapy in overcoming immune resistance in cancer treatment, and systematically summarizes and discusses the characteristics of exosomes from different cell sources. Furthermore, the prospects and challenges of exosome-related therapies are discussed.

Tumor immunology meets oncology (TIMO) XVI, July 07-09 2022 in Halle/Saale, Germany

During the TIMO meeting 2022, national and international scientists as well as clinicians gave novel insights as well as perspectives into basic and translational tumor immunology.

Immune checkpoint inhibitor resistance in hepatocellular carcinoma

The application of immune checkpoint inhibitors (ICIs) has markedly enhanced the treatment of hepatocellular carcinoma (HCC), and HCC patients who respond to ICIs have shown prolonged survival. However, only a subset of HCC patients benefit from ICIs, and those who initially respond to ICIs may develop resistance. ICI resistance is likely related to various factors, including the immunosuppressive tumor microenvironment (TME), the absence of antigen expression and impaired antigen presentation, tumor heterogeneity, and gut microbiota. Therefore, exploring the possible mechanisms of ICI resistance is crucial to improve the clinical benefit of ICIs further. Various combination therapies for HCC immunotherapy have prevented and reversed ICI resistance to a certain extent. In addition, many new combination therapies that can overcome resistance are being explored. This review seeks to characterize the complex TME in HCC, explore the possible mechanisms of immune resistance to ICIs in different resistance categories, and review the combination therapies currently being applied and those under investigation for immunotherapy.

Genetic dysregulation of immunologic and oncogenic signaling pathways associated with tumor-intrinsic immune resistance: a molecular basis for combination targeted therapy-immunotherapy for cancer

Since the turn of the century, advances in targeted therapy and immunotherapy have revolutionized the treatment of cancer. Although these approaches have far outperformed traditional therapies in various clinical settings, both remain plagued by mechanisms of innate and acquired resistance that limit therapeutic efficacy in many patients. With a focus on tumor-intrinsic resistance to immunotherapy, this review highlights our current understanding of the immunologic and oncogenic pathways whose genetic dysregulation in cancer cells enables immune escape. Emphasis is placed on genomic, epigenomic, transcriptomic, and proteomic aberrations that influence the activity of these pathways in the context of immune resistance. Specifically, the role of pathways that govern interferon signaling, antigen processing and presentation, and immunologic cell death as determinants of tumor immune susceptibility are discussed. Likewise, mechanisms of tumor immune resistance mediated by dysregulated RAS-MAPK, WNT, PI3K-AKT-mTOR, and cell cycle pathways are described. Finally, this review highlights the ways in which recent insight into genetic dysregulation of these immunologic and oncogenic signaling pathways is informing the design of combination targeted therapy-immunotherapy regimens that aim to restore immune susceptibility of cancer cells by overcoming resistance mechanisms that often limit the success of monotherapies.

The thin red line between the immune system and cancer evolution

The cancer immunoediting theory describes the dual ability of endogenous antitumor immunity to inhibit or promote progressing cancers. Tumor-specific neoantigens arising from somatic mutations serve as targets for the endogenous T-cell-mediated antitumor immunity and therefore possess a crucial role for tumor development. Additionally, targeting these molecules is conceptually appealing because neoantigens are not expressed in healthy tissue and therefore confer less toxicity and greater specificity when used in therapeutic interventions. Moreover, intratumor neo-antigenic heterogeneity is believed to play a pivotal role in the activation of adaptive immunity and in the efficacy of immunotherapies that are based on immune checkpoint inhibition. In this respect, mutual interactions between tumor cells and immune lymphocytes regulate the levels of antitumor immunity, but also shape tumor heterogeneity through the selective outgrowth of tumor subclones. Therefore, the exploration of the mechanistic pathways and the identification of the genomic aberrations underlying the clonal evolution of tumors is considered mandatory for improving the clinical outcomes of therapies, as it will assist in the selection of the appropriate therapeutic decisions so as to delay, avoid, or overcome resistance through the identification of the most effective therapeutic strategies.

Fibrinogen-like protein 1 (FGL1): the next immune checkpoint target

Immune checkpoint therapy has achieved significant efficacy by blocking inhibitory pathways to release the function of T lymphocytes. In the clinic, anti-programmed cell death protein 1/programmed cell death ligand 1 (PD-1/PD-L1) monoclonal antibodies (mAbs) have progressed to first-line monotherapies in certain tumor types. However, the efficacy of anti-PD-1/PD-L1 mAbs is still limited due to toxic side effects and de novo or adaptive resistance. Moreover, other immune checkpoint target and biomarkers for therapeutic response prediction are still lacking; as a biomarker, the PD-L1 (CD274, B7-H1) expression level is not as accurate as required. Hence, it is necessary to seek more representative predictive molecules and potential target molecules for immune checkpoint therapy. Fibrinogen-like protein 1 (FGL1) is a proliferation- and metabolism-related protein secreted by the liver. Multiple studies have confirmed that FGL1 is a newly emerging checkpoint ligand of lymphocyte activation gene 3 (LAG3), emphasizing the potential of targeting FGL1/LAG3 as the next generation of immune checkpoint therapy. In this review, we summarize the substantial regulation mechanisms of FGL1 in physiological and pathological conditions, especially tumor epithelial to mesenchymal transition, immune escape and immune checkpoint blockade resistance, to provide insights for targeting FGL1 in cancer treatment.

NK cells-directed therapies target circulating tumor cells and metastasis

Metastasis is the major cause of cancer-related deaths. Invasive primary cancers often metastasize after circulating tumor cells (CTCs) enter the bloodstream or lymph node to colonize adjacent tissue or distant anatomical locations. CTCs interact with immune cells and metastatic microenvironments, survival signaling, and chemotherapeutic resistance. Among immune cells, natural killer (NK) cells can, directly and indirectly, interact with CTCs to control cancer metastasis. Understanding the molecular mechanisms that drive NK cells mediated recognition and elimination of CTCs may pave the way for a new generation of anti-CTC molecularly targeted immunotherapies. In this review, we will discuss i) the role of CTCs in metastases, ii) CTCs in the context of the tumor microenvironment, iii) CTCs immune escape, and finally, iv) the potentials of NK cell-based therapies alone, or in combination with nanomedicine for targeted-immunotherapies of metastatic diseases.

Human ovarian cancer intrinsic mechanisms regulate lymphocyte activation in response to immune checkpoint blockade

Immune checkpoint blocking antibodies are currently being tested in ovarian cancer (OC) patients and have shown some responses in early clinical trials. However, it remains unclear how human OC cancer cells regulate lymphocyte activation in response to therapy. In this study, we have established and optimised an in vitro tumour-immune co-culture system (TICS), which is specifically designed to quantify the activation of multiple primary human lymphocyte subsets and human cancer cell killing in response to PD-1/L1 blockade. Human OC cell lines and treatment naïve patient ascites show differential effects on lymphocyte activation and respond differently to PD-1 blocking antibody nivolumab in TICS. Using paired OC cell lines established prior to and after chemotherapy relapse, our data reveal that the resistant cells express low levels of HLA and respond poorly to nivolumab, relative to the treatment naïve cells. In accordance, knockdown of IFNγ receptor expression compromises response to nivolumab in the treatment naïve OC cell line, while enhanced HLA expression induced by a DNA methyltransferase inhibitor promotes lymphocyte activation in TICS. Altogether, our results suggest a ‘cross resistance’ model, where the acquired chemotherapy resistance in cancer cells may confer resistance to immune checkpoint blockade therapy through down-regulation of antigen presentation machinery. As such, agents that can restore HLA expression may be a suitable combination partner for immunotherapy in chemotherapy-relapsed human ovarian cancer patients.

The Role of ERO1α in Modulating Cancer Progression and Immune Escape

Endoplasmic reticulum oxidoreductin-1 alpha (ERO1α) was originally shown to be an endoplasmic reticulum (ER) resident protein undergoing oxidative cycles in concert with protein disulfide isomerase (PDI) to promote proper protein folding and to maintain homeostasis within the ER. ERO1α belongs to the flavoprotein family containing a flavin adenine dinucleotide utilized in transferring of electrons during oxidation-reduction cycles. This family is used to maintain redox potentials and protein homeostasis within the ER. ERO1α's location and function has since been shown to exist beyond the ER. Originally thought to exist solely in the ER, it has since been found to exist in the golgi apparatus, as well as in exosomes purified from patient samples. Besides aiding in protein folding of transmembrane and secretory proteins in conjunction with PDI, ERO1α is also known for formation of de novo disulfide bridges. Public databases, such as the Cancer Genome Atlas (TCGA) and The Protein Atlas, reveal ERO1α as a poor prognostic marker in multiple disease settings. Recent evidence indicates that ERO1α expression in tumor cells is a critical determinant of metastasis. However, the impact of increased ERO1α expression in tumor cells extends into the tumor microenvironment. Secretory proteins requiring ERO1α expression for proper folding have been implicated as being involved in immune escape through promotion of upregulation of programmed death ligand-1 (PD-L1) and stimulation of polymorphonuclear myeloid derived suppressor cells (PMN-MDSC's) via secretion of granulocytic colony stimulating factor (G-CSF). Hereby, ERO1α plays a pivotal role in cancer progression and potentially immune escape; making ERO1α an emerging attractive putative target for the treatment of cancer.

The intracellular signaling pathway of octopamine upregulating immune resistance functions in Penaeus monodon

Octopamine (OA), a biogenic monoamine, is known to mediate several immune responses. This study analyzed the effects of OA on immunological regulation in the tiger shrimp Penaeus monodon. The immune parameters including total haemocyte count, differential haemocyte count, phenoloxidase activity, respiratory bursts, superoxide dismutase activity, and phagocytic activity and clearance efficiency in response to the pathogen, Photobacterium damselae, were determined when shrimp were individually injected with saline or OA at 100 or 1000 pmol shrimp^-1. In addition, the intracellular second messengers in haemocyte such as Ca²⁺ and adenosine 3',5'-cyclic monophosphate (cAMP) were examined in shrimp receiving saline or OA at 1 or 10 nmol shrimp^-1. Results showed that all of the immune parameters significantly increased at 2-4 h in OA-injected shrimp except hyaline cells in 100 pmol shrimp^-1-injected shrimp at 4 h, but phenoloxidase activity per granulocyte significantly decreased at 2-4 h. However, these had returned to saline control levels after receiving OA for 8 h except differential haemocyte count and phenoloxidase activity per granulocyte for 16 h. An injection of OA also significantly increased the survival rate of shrimp challenged with Pho. damselae. Shrimp receiving OA at 1 and 10 nmol shrimp^-1 significantly increased the intracellular Ca²⁺ concentration ([Ca²⁺]i) at 30-60 min and 30 min, and cAMP concentration [cAMP]i) at 5-15 min and 15 min, respectively. However, [Ca²⁺]i at 50-60 min, and [cAMP]i at 30-60 min returned to saline control when the shrimp received OA at 10 nmol shrimp^-1, and at 1 and 10 nmol shrimp^-1, respectively. These results suggest that OA administration by injection at ≤1000 pmol shrimp^-1 mediates transient upregulation of immunity together with the increased resistance of P. monodon to Pho. damselae, which are modulated through intracellular Ca²⁺ and cAMP second messenger pathways.

Recent advances in the clinical development of immune checkpoint blockade therapy

BACKGROUND

The discovery of immune checkpoint proteins and the mechanisms by which cancer cells utilize them to evade the immune system has transformed our approach to cancer immunotherapy. Checkpoint blockade antibodies targeting cytotoxic T lymphocyte antigen 4 (CTLA-4), programmed cell death 1 (PD-1) and its ligands such as programmed cell death ligand 1 (PD-L1) have already revolutionized the treatment of multiple types of cancer and have significantly improved treatment and survival outcomes of patients affected by these malignancies.

CONCLUSIONS

Herein, we summarize current knowledge about the role of, and the mechanisms underlying PD-1/PD-L1 signaling pathways in antitumor immune responses, with particular emphasis on clinical studies evaluating the efficacy of anti-PD-1/PD-L1 blockade in various tumor types. Preliminary clinical investigations with immune-checkpoint blockers highlight broad opportunities with a high potential to enhance antitumor immunity and, as such, to generate significant clinical responses. These preliminary successes open up new avenues towards efficient therapeutics offered to patients.

The relationship between autophagy and the immune system and its applications for tumor immunotherapy

Autophagy is a genetically well-controlled cellular process that is tightly controlled by a set of core genes, including the family of autophagy-related genes (ATG). Autophagy is a “double-edged sword” in tumors. It can promote or suppress tumor development, which depends on the cell and tissue types and the stages of tumor. At present, tumor immunotherapy is a promising treatment strategy against tumors. Recent studies have shown that autophagy significantly controls immune responses by modulating the functions of immune cells and the production of cytokines. Conversely, some cytokines and immune cells have a great effect on the function of autophagy. Therapies aiming at autophagy to enhance the immune responses and anti-tumor effects of immunotherapy have become the prospective strategy, with enhanced antigen presentation and higher sensitivity to CTLs. However, the induction of autophagy may also benefit tumor cells escape from immune surveillance and result in intrinsic resistance against anti-tumor immunotherapy. Increasing studies have proven the optimal use of either ATG inducers or inhibitors can restrain tumor growth and progression by enhancing anti-tumor immune responses and overcoming the anti-tumor immune resistance in combination with several immunotherapeutic strategies, indicating that induction or inhibition of autophagy might show us a prospective therapeutic strategy when combined with immunotherapy. In this article, the possible mechanisms of autophagy regulating immune system, and the potential applications of autophagy in tumor immunotherapy will be discussed.

JAK/Stat5-mediated subtype-specific lymphocyte antigen 6 complex, locus G6D (LY6G6D) expression drives mismatch repair proficient colorectal cancer

BACKGROUND

Human microsatellite-stable (MSS) colorectal cancers (CRCs) are immunologically "cold" tumour subtypes characterized by reduced immune cytotoxicity. The molecular linkages between immune-resistance and human MSS CRC is not clear.

METHODS

We used transcriptome profiling, in silico analysis, immunohistochemistry, western blot, RT-qPCR and immunofluorescence staining to characterize novel CRC immune biomarkers. The effects of selective antagonists were tested by in vitro assays of long term viability and analysis of kinase active forms using anti-phospho antibodies.

RESULTS

We identified the lymphocyte antigen 6 complex, locus G6D (LY6G6D) as significantly overexpressed (around 15-fold) in CRC when compared with its relatively low expression in other human solid tumours. LY6G6D up-regulation was predominant in MSS CRCs characterized by an enrichment of immune suppressive regulatory T-cells and a limited repertoire of PD-1/PD-L1 immune checkpoint receptors. Coexpression of LY6G6D and CD15 increases the risk of metastatic relapse in response to therapy. Both JAK-STAT5 and RAS-MEK-ERK cascades act in concert as key regulators of LY6G6D and Fucosyltransferase 4 (FUT4), which direct CD15-mediated immune-resistance. Momelotinib, an inhibitor of JAK1/JAK2, consistently abrogated the STAT5/LY6G6D axis in vitro, sensitizing MSS cancer cells with an intact JAK-STAT signaling, to efficiently respond to trametinib, a MEK inhibitor used in clinical setting. Notably, colon cancer cells can evade JAK2/JAK1-targeted therapy by a reversible shift of the RAS-MEK-ERK pathway activity, which explains the treatment failure of JAK1/2 inhibitors in refractory CRC.

CONCLUSIONS

Combined targeting of STAT5 and MAPK pathways has superior therapeutic effects on immune resistance. In addition, the new identified LY6G6D antigen is a promising molecular target for human MSS CRC.

Molecular cloning and functional characterization of a homolog of the transcriptional regulator CSL in Litopenaeus vannamei

The Notch signaling pathway transcriptional regulator, CSL (also called as CBF1, Suppressor of Hairless or Lag-1 in different species, generally designated as CSL1), is not only associated with cell proliferation and differentiation but also involved in tumorigenesis, inflammation and immune regulation in vertebrates. We recently showed that Notch signaling was involved in the immune response of Litopenaeus vannamei shrimp. However, as an important transcriptional regulator of this pathway, whether or not shrimp CSL was also involved in immune response had not been explored. Here, we cloned and characterized the CSL gene in L. vannamei (LvCSL), which has a 2271 bp open reading frame (ORF) encoding a putative protein of 756 amino acids, and contains two conserved Lag1-DNA bind as well as beta trefoil domains (BTD). LvCSL clustered with invertebrates in the phylogenetic tree and closely related to the RBP Jk X1 of Parasteatoda tepidariorum. The transcript level of LvCSL analyzed by quantitative polymerase chain reaction (qPCR) showed that LvCSL was widely expressed in all tissues tested, with induced levels observed in the hepatopancreas and hemocytes following immune challenge with Vibrio parahaemolyticus, Streptoccocus iniae, lipopolysaccharide (LPS), and white spot syndrome virus (WSSV), therefore, suggesting LvCSL involvement in shrimp immune response to pathogens. Besides, LvCSL knockdown decreased the expression of proliferation-related genes (LvHey2 and LvAstakine), and attenuated the expression of immune-related genes L. vannamei hypoxia inducible factor alpha (LvHIF-α), LvLectin and L. vannamei small subunit hemocyanin (LvHMCS) in shrimp hemocytes, as well as significantly decreased total hemocyte count. Moreover, high cumulative mortality was observed in LvCSL depleted shrimp challenged with V. parahaemoliticus. In conclusion, our present data strongly suggest that LvCSL is an important factor in shrimp, vital for shrimp survival and contributing to immune resistance to pathogens.

Immune oncology, immune responsiveness and the theory of everything

Anti-cancer immunotherapy is encountering its own checkpoint. Responses are dramatic and long lasting but occur in a subset of tumors and are largely dependent upon the pre-existing immune contexture of individual cancers. Available data suggest that three landscapes best define the cancer microenvironment: immune-active, immune-deserted and immune-excluded. This trichotomy is observable across most solid tumors (although the frequency of each landscape varies depending on tumor tissue of origin) and is associated with cancer prognosis and response to checkpoint inhibitor therapy (CIT). Various gene signatures (e.g. Immunological Constant of Rejection - ICR and Tumor Inflammation Signature - TIS) that delineate these landscapes have been described by different groups. In an effort to explain the mechanisms of cancer immune responsiveness or resistance to CIT, several models have been proposed that are loosely associated with the three landscapes. Here, we propose a strategy to integrate compelling data from various paradigms into a “Theory of Everything”. Founded upon this unified theory, we also propose the creation of a task force led by the Society for Immunotherapy of Cancer (SITC) aimed at systematically addressing salient questions relevant to cancer immune responsiveness and immune evasion. This multidisciplinary effort will encompass aspects of genetics, tumor cell biology, and immunology that are pertinent to the understanding of this multifaceted problem.

Nanotechnology Approaches to Improving Cancer Immunotherapy

Cancer immunotherapy is a powerful, growing treatment approach to cancer that can be combined with chemotherapy, radiotherapy, and oncosurgery. Modulating the immune system to enhance anticancer response by several strategies has yielded improved cancer survival. Despite this progress, the success rate for immunotherapy has been below expectations due to unpredictable efficacy and off-target side effects from systemic dosing. Nanotechnology offers numerous different materials and targeting properties to overcome many of these challenges in immunotherapy. In this chapter, we review current immunotherapy and its challenges as well as the latest nanotechnology applications in cancer immunotherapy.

PD-1/PD-L1 and immunotherapy for pancreatic cancer

Therapy that targets programmed death 1 or programmed death 1 ligand 1 (PD-1/PD-L1), which are known as immune checkpoints, has been recently rapidly developing as oncotherapy for various carcinomas. However, this therapy has a poor effect on the treatment of pancreatic cancer with PD-1/PD-L1 blockade monotherapy. In this review, the development and limitations of anti-PD-1/PD-L1 monotherapy in pancreatic cancer are discussed. We then consider the underlying mechanism of anti-PD-1/PD-L1 monotherapy failure, combination strategies overcoming resistance to anti-PD-1/PD-L1 immunotherapy and the prospect of targeting PD-1/PD-L1 for the immunotherapy of pancreatic cancer.

The upregulation of immune responses in tyrosine hydroxylase (TH) silenced Litopenaeus vannamei

Catecholamines (CAs) play a crucial role in maintaining physiological and immune homeostasis in invertebrates and vertebrates under stressful conditions. Tyrosine hydroxylase (TH) is the first and rate-limiting enzyme in CA synthesis. To develop an effective CA-related immunological defense system against stress and pathogen infection, various criteria, were evaluated in TH double-stranded (ds) RNA-injected white shrimp, Litopenaeus vannamei. Specifically, the relative transcript quantification of TH, dopamine β-hydroxylase (DBH), crustacean hyperglycemic hormone (CHH), and other immune-related genes; TH activity in the haemolymph; and the estimation of l-dihydroxyphenylalanine (l-DOPA), glucose, and lactate levels in the haemolymph were examined. TH depletion revealed a significant increase in the total haemocyte count; granular cells; semigranular cells; respiratory bursts (RBs, release of superoxide anion); superoxide dismutase (SOD) activity; phagocytic activity and clearance efficiency; and the expression of lipopolysaccharide and β-1,3-glucan-binding protein and peroxinectin, SOD, crustin, and lysozyme genes. In addition, the reduction of TH gene expression and activity was accompanied by a decline of phenoloxidase (PO) activity per granulocyte, lower glucose and lactate levels, and significantly low expression of DBH and CHH genes. However, the number of hyaline cells, activity of PO, RBs per haemocyte, and expression of POI and POII genes were not significantly different in the LvTH-silenced shrimp. Notably, the survival ratio of LvTH-silenced shrimp was significantly higher than that of shrimp injected with diethyl pyrocarbonate-water and nontargeting dsRNA when challenged with Vibrio alginolyticus. Therefore, the depletion of TH can enhance disease resistance in shrimp by upregulating specific immune parameters but downregulating the levels of carbohydrate metabolites.

Potential biomarker for checkpoint blockade immunotherapy and treatment strategy

Programmed cell death protein-1 (PD-1) and ligand (PD-L1) provide an important escape mechanism from immune attack, and blockade therapy of these proteins show promising clinical benefits in many types of cancer. PD-L1 can be induced by interferon-gamma (IFN-γ), hypoxia, or toll-like receptor (TLR)-mediated pathways that confer adaptive immune resistance, or upregulated by oncogenic signals leading to constitutive expression and resulting in intrinsic immune resistance. The PD-1/PD-L1 checkpoint blockade, which targets regulatory pathways in T cells to overcome immune resistance, is correlated to PD-L1 expression pattern and the presence of tumor-infiltrating lymphocytes (TILs). Meanwhile, immunogenic mutation loads show significant response to checkpoint blockade, which is probably due to PD-1/L1 status and TIL content. Finally, the clinical strategies to design effective checkpoint-targeting immunotherapies are based on the classification of inducible/constitutive expression of PD-L1 and the presence of TILs.

Acquired and intrinsic resistance in cancer immunotherapy

A number of immunotherapies, in particular immune checkpoint targeting antibodies and adoptive T-cell therapies, are starting to transform the treatment of advanced cancers. The likelihood to respond to these immunotherapies differs strongly across tumor types, with response rates for checkpoint targeting being the highest in advanced melanoma, renal cell cancer and non-small cell lung cancer. However, also non-responsiveness is observed, indicating the presence of intrinsic resistance or naturally acquired resistance. In addition, a subgroup of patients that do initially respond to immunotherapy will later recur, thereby also pointing towards a role of therapy-induced acquired resistance. Here, we review our current understanding of both intrinsic and acquired resistance mechanisms in cancer immunotherapy, and discuss potential strategies to overcome them.