Recruitment and activation of type 3 innate lymphoid cells promote antitumor immune responses.

Tumors poorly infiltrated by T cells are more resistant to immunogenic chemotherapies and checkpoint inhibition than highly infiltrated tumors. Using murine models, we found that CCR6+ type 3 innate lymphoid cells (ILC3s) can trigger an increase in the number of T cells infiltrating a tumor. Shortly after administration of cisplatin chemotherapy, production of the chemokine CCL20 and proinflammatory cytokine IL-1ß at the tumor site led to the recruitment and activation of ILC3s. Within the tumor, ILC3 production of the chemokine CXCL10 was responsible for the recruitment of CD4+ and CD8+ T lymphocytes to the tumor. ILC3-dependent infiltration of T cells was essential for antitumor immune responses and increased the efficacy of checkpoint inhibition. Thus, we reveal an essential role of CCL20 and IL-1ß, which promote ILC3-dependent antitumor immunity and enhance tumor sensitivity to immunotherapy.

Using immunogenic cell death to improve anticancer efficacy of immune checkpoint inhibitors: From basic science to clinical application.

Even though the discovery of immune checkpoint inhibitors (ICIs) has revolutionized cancer treatment, a high proportion of patients do not respond. Moreover, some types of cancers are refractory to these treatments. Thus, the need to find predictive biomarkers of efficacy and to evaluate the association with other treatments, such as chemotherapy or radiotherapy, appears to be essential. Because ICIs reactivate or maintain an active status of T cells, one possibility is to combine these treatments with therapies that engage an immune response against tumor cells. Thus, by inducing immunogenic cell death (ICD) of cancer cells, some conventional anticancer treatments induce such immune response and may have an interest to be combined with ICIs. In this review, we explore preclinical studies and clinical trials that evaluate the combination of ICIs with ICD inducers. More than inducing ICD, some of these treatments appear to modulate the tumor microenvironment and more particularly to inhibit immunosuppression, thus improving treatment efficacy.

The receptor NLRP3 is a transcriptional regulator of TH2 differentiation.

The receptor NLRP3 is involved in the formation of the NLRP3 inflammasome that activates caspase-1 and mediates the release of interleukin 1ß (IL-1ß) and IL-18. Whether NLRP3 can shape immunological function independently of inflammasomes is unclear. We found that NLRP3 expression in CD4(+) T cells specifically supported a T helper type 2 (TH2) transcriptional program in a cell-intrinsic manner. NLRP3, but not the inflammasome adaptor ASC or caspase-1, positively regulated a TH2 program. In TH2 cells, NLRP3 bound the Il4 promoter and transactivated it in conjunction with the transcription factor IRF4. Nlrp3-deficient TH2 cells supported melanoma tumor growth in an IL-4-dependent manner and also promoted asthma-like symptoms. Our results demonstrate the ability of NLRP3 to act as a key transcription factor in TH2 differentiation.

The transcription factor IRF1 dictates the IL-21-dependent anticancer functions of TH9 cells.

The TH9 subset of helper T cells was initially shown to contribute to the induction of autoimmune and allergic diseases, but subsequent evidence has suggested that these cells also exert antitumor activities. However, the molecular events that account for their effector properties are elusive. Here we found that the transcription factor IRF1 enhanced the effector function of TH9 cells and dictated their anticancer properties. Under TH9-skewing conditions, interleukin 1ß (IL-1ß) induced phosphorylation of the transcription factor STAT1 and subsequent expression of IRF1, which bound to the promoters of Il9 and Il21 and enhanced secretion of the cytokines IL-9 and IL-21 from TH9 cells. Furthermore, IL-1ß-induced TH9 cells exerted potent anticancer functions in an IRF1- and IL-21-dependent manner. Our findings thus identify IRF1 as a target for controlling the function of TH9 cells.

Stat3 and Gfi-1 transcription factors control Th17 cell immunosuppressive activity via the regulation of ectonucleotidase expression.

Although Th17 cells are known to promote tissue inflammation and autoimmunity, their role during cancer progression remains elusive. Here, we showed that in vitro Th17 cells generated with the cytokines IL-6 and TGF-ß expressed CD39 and CD73 ectonucleotidases, leading to adenosine release and the subsequent suppression of CD4(+) and CD8(+) T cell effector functions. The IL-6-mediated activation of the transcription factor Stat3 and the TGF-ß-driven downregulation of Gfi-1 transcription factor were both essential for the expression of ectonucleotidases during Th17 cell differentiation. Stat3 supported whereas Gfi-1 repressed CD39 and CD73 expression by binding to their promoters. Accordingly, Th17 cells differentiated with IL-1ß, IL-6, and IL-23 but without TGF-ß did not express ectonucleotidases and were not immunosuppressive. Finally, adoptive transfer of Th17 cells induced by TGF-ß and IL-6 promoted tumor growth in a CD39-dependent manner. Thus, ectonucleotidase expression supports the immunosuppressive fate of Th17 cells in cancer.

Hypotonic stress enhances colon cancer cell death induced by platinum derivatives and immunologically improves antitumor efficacy of intraperitoneal chemotherapy.

Colorectal cancer is a highly metastatic disease that could invade various distal organs and also the peritoneal cavity leading to peritoneal carcinomatosis. This is a terminal condition with poor prognosis and only palliative treatments such as cytoreductive surgery and intraperitoneal chemotherapy are proposed to some patients. However, clinicians use different parameters of treatments without any consensus. Here we decided to evaluate the effect of osmolarity in the efficacy of this procedure to kill colon cancer cells. We first show that a short exposure of platinum derivatives in hypotonic conditions is more efficient to decrease cell viability of human and murine colon cancer cells in vitro as compared to isotonic conditions. This is related to more important incorporation of platinum and the capacity of hypotonic stress to induce the copper transporter CTR1 oligomerization. Oxaliplatin in hypotonic conditions induces caspase-dependent cell death of colon cancer cells. Moreover, hypotonic conditions also modulate the capacity of oxaliplatin and cisplatin (but not carboplatin) to induce immunogenic cell death (ICD). In vivo, oxaliplatin in hypotonic conditions increases CD8+ T cell tumor infiltration and activation. Finally, in a murine peritoneal carcinomatosis model, oxaliplatin in hypotonic conditions is the only tested protocol which is able to slow down the appearance of tumor nodules and increase mice survival, while showing no effect in CD8+ T cells depleted mice or in immunodeficient mice. Altogether, our study provides new information both in vitro and in a preclinical model of peritoneal carcinomatosis, which highlights the importance of hypoosmolarity in intraperitoneal chemotherapy.

Heat Shock Proteins and Inflammasomes.

Heat shock proteins (HSP) regulate inflammation in many physiological contexts. However, inflammation is a broad process, involving numerous cytokines produced by different molecular pathways with multiple functions. In this review, we focused on the particular role of HSP on the inflammasomes intracellular platforms activated by danger signals and that enable activation of inflammatory caspases, mainly caspase-1, leading to the production of the pro-inflammatory cytokine IL-1ß. Interestingly, some members of the HSP family favor inflammasomes activation whereas others inhibit it, suggesting that HSP modulators for therapeutic purposes, must be carefully chosen.

Cytotoxic effects of chemotherapy on cancer and immune cells: how can it be modulated to generate novel therapeutic strategies?

The first objective to use chemotherapy is to kill cancer cells. However, it is common knowledge that these drugs can also damage healthy host cells, especially immune cells, and thus impair the endogenous antitumor response. Here, we focus on the cytotoxic effects of chemotherapy on tumor cells and immune cells. It is not enough to simply kill cancer cells, and causing immunogenic cell death will impair the adaptive immune system's ability to fight the remaining cancer cells. On the other hand, the killing of immune cells can also enhance tumor growth. A study of the repercussions of the cytotoxic effects of chemotherapy is of great importance to evaluate the antitumor response. Strategies can be proposed to promote the 'good way' for cancer cells to die and to avoid the adverse side effects of chemotherapy on immune cells in order to strengthen the role of the immune system in the antitumor response.

Associating Immunotherapy and Targeted Therapies: Facts and Hopes.

Immune-checkpoint inhibitors (ICI), particularly inhibitors of the PD-1/PD-L1 (Programmed Death 1/Programmed Death-Ligand 1) axis, have modified the management of many types of cancer over the last 10 years. However, both intrinsic and acquired resistance are major clinical issues with these therapies, and only a few patients are cured by ICI monotherapy. To overcome resistance, the concept of combining ICIs with other therapies is emerging and supported by many preclinical trials. Besides associations of ICIs with chemotherapy or radiotherapy, now used in clinical practice, some targeted therapies have also been reported to influence immune response of patients against cancer cells, thus showing potential synergy with ICIs. In this review, we describe the preclinical and clinical advances to date in the use of these combination strategies.

Production of adenosine by ectonucleotidases: a key factor in tumor immunoescape.

It is now well known that tumor immunosurveillance contributes to the control of cancer growth. Many mechanisms can be used by cancer cells to avoid the antitumor immune response. One such mechanism relies on the capacity of cancer cells or more generally of the tumor microenvironment to generate adenosine, a major molecule involved in antitumor T cell response suppression. Adenosine is generated by the dephosphorylation of extracellular ATP released by dying tumor cells. The conversion of ATP into adenosine is mediated by ectonucleotidase molecules, namely, CD73 and CD39. These molecules are frequently expressed in the tumor bed by a wide range of cells including tumor cells, regulatory T cells, Th17 cells, myeloid cells, and stromal cells. Recent evidence suggests that targeting adenosine by inhibiting ectonucleotidases may restore the resident antitumor immune response or enhance the efficacy of antitumor therapies. This paper will underline the impact of adenosine and ectonucleotidases on the antitumor response.

In situ immune response after neoadjuvant chemotherapy for breast cancer predicts survival.

Accumulating preclinical evidence suggests that anticancer immune responses contribute to the success of chemotherapy. However, the predictive value of tumour-infiltrating lymphocytes after neoadjuvant chemotherapy for breast cancer remains unknown. We hypothesized that the nature of the immune infiltrate following neoadjuvant chemotherapy would predict patient survival. In a series of 111 consecutive HER2- and a series of 51 non-HER2-overexpressing breast cancer patients treated by neoadjuvant chemotherapy, we studied by immunohistochemistry tumour infiltration by FOXP3 and CD8 T lymphocytes before and after chemotherapy. Kaplan-Meier analysis and Cox modelling were used to assess relapse-free survival (RFS) and overall survival (OS). A predictive scoring system using American Joint Committee on Cancer (AJCC) pathological staging and immunological markers was created. Association of high CD8 and low FOXP3 cell infiltrates after chemotherapy was significantly associated with improved RFS (p = 0.02) and OS (p = 0.002), and outperformed classical predictive factors in multivariate analysis. A combined score associating CD8/FOXP3 ratio and pathological AJCC staging isolated a subgroup of patients with a long-term overall survival of 100%. Importantly, this score also identified patients with a favourable prognosis in an independent cohort of HER2-negative breast cancer patients. These results suggest that immunological CD8 and FOXP3 cell infiltrate after treatment is an independent predictive factor of survival in breast cancer patients treated with neoadjuvant chemotherapy and provides new insights into the role of the immune milieu and cancer.

Can the hyperthermia-mediated heat shock factor/heat shock protein 70 pathway dampen the cytokine storm during SARS-CoV-2 infection?

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a major global public health problem. Infection by this virus involves many pathophysiological processes, such as a "cytokine storm," that is, very aggressive inflammatory response that offers new perspectives for the management and treatment of patients. Here, we analyse relevant mechanism involved in the hyperthermia-mediated heat shock factors (HSFs)/heat shock proteins (HSP)70 pathway which may provide a possible treatment tool. LINKED ARTICLES: This article is part of a themed issue on The Pharmacology of COVID-19. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.21/issuetoc.

Tumor Immunogenic Cell Death as a Mediator of Intratumor CD8 T-Cell Recruitment.

The success of anticancer treatments relies on a long-term response which can be mediated by the immune system. Thus, the concept of immunogenic cell death (ICD) describes the capacity of dying cancer cells, under chemotherapy or physical stress, to express or release danger-associated molecular patterns (DAMPs). These DAMPs are essential to activate dendritic cells (DCs) and to stimulate an antigen presentation to CD8 cytotoxic cells. Then, activated CD8 T cells exert their antitumor effects through cytotoxic molecules, an effect which is transitory due to the establishment of a feedback loop leading to T-cell exhaustion. This phenomenon can be reversed using immune checkpoint blockers (ICBs), such as anti-PD-1, PD-L1 or CTLA-4 Abs. However, the blockade of these checkpoints is efficient only if the CD8 T cells are recruited within the tumor. The CD8 T-cell chemoattraction is mediated by chemokines. Hence, an important question is whether the ICD can not only influence the DC activation and resulting CD8 T-cell activation but can also favor the chemokine production at the tumor site, thus triggering their recruitment. This is the aim of this review, in which we will decipher the role of some chemokines (and their specific receptors), shown to be released during ICD, on the CD8 T-cell recruitment and antitumor response. We will also analyze the clinical applications of these chemokines as predictive or prognostic markers or as new targets which should be used to improve patients' response.

Downregulation of Elovl5 promotes breast cancer metastasis through a lipid-droplet accumulation-mediated induction of TGF-ß receptors.

Metastatic breast cancer cannot be cured, and alteration of fatty acid metabolism contributes to tumor progression and metastasis. Here, we were interested in the elongation of very long-chain fatty acids protein 5 (Elovl5) in breast cancer. We observed that breast cancer tumors had a lower expression of Elovl5 than normal breast tissues. Furthermore, low expression of Elovl5 is associated with a worse prognosis in ER+ breast cancer patients. In accordance with this finding, decrease of Elovl5 expression was more pronounced in ER+ breast tumors from patients with metastases in lymph nodes. Although downregulation of Elovl5 expression limited breast cancer cell proliferation and cancer progression, suppression of Elovl5 promoted EMT, cell invasion and lung metastases in murine breast cancer models. The loss of Elovl5 expression induced upregulation of TGF-ß receptors mediated by a lipid-droplet accumulation-dependent Smad2 acetylation. As expected, inhibition of TGF-ß receptors restored proliferation and dampened invasion in low Elovl5 expressing cancer cells. Interestingly, the abolition of lipid-droplet formation by inhibition of diacylglycerol acyltransferase activity reversed induction of TGF-ß receptors, cell invasion, and lung metastasis triggered by Elovl5 knockdown. Altogether, we showed that Elovl5 is involved in metastasis through lipid droplets-regulated TGF-ß receptor expression and is a predictive biomarker of metastatic ER+ breast cancer.

MEK inhibition overcomes chemoimmunotherapy resistance by inducing CXCL10 in cancer cells.

Chemotherapy with anti PD-1/PD-L1 antibodies has become the standard of care for patients with metastatic non-small cell lung cancer (mNSCLC). Using lung tumor models, where pemetrexed and cisplatin (PEM/CDDP) chemotherapy remains unable to synergize with immune checkpoint inhibitors (ICIs), we linked the failure of this treatment with its inability to induce CXCL10 expression and CD8+ T cell recruitment. Using drug screening, we showed that combining a MEK inhibitor (MEKi) with PEM/CDDP triggers CXCL10 secretion by cancer cells and CD8+ T cell recruitment, sensitizing it to ICIs. PEM/CDDP plus a MEKi promotes optineurin (OPTN)-dependent mitophagy, resulting in CXCL10 production in a mitochondrial DNA- and TLR9-dependent manner. TLR9 or autophagy/mitophagy inhibition abolishes the anti-tumor efficacy of PEM/CDDP plus MEKi/anti-PD-L1 therapy. In human NSCLCs, high OPTN, TLR9, and CXCL10 expression is associated with a better response to ICIs. Our results underline the role of TLR9- and OPTN-dependent mitophagy in enhancing chemoimmunotherapy efficacy.

Presence of Foxp3 expression in tumor cells predicts better survival in HER2-overexpressing breast cancer patients treated with neoadjuvant chemotherapy.

The Forkhead Box Protein 3 is highly expressed not only in regulatory T cells, but also in tumor cells, acting as a transcriptional repressor of breast oncogenes including HER2. We investigated the prognostic significance of Foxp3 expression in cancer cells in a large cohort of patients with HER2-overexpressing breast carcinoma treated with neoadjuvant chemotherapy. Foxp3-positive tumor cells were detected by immunohistochemistry in 103 patients with primary invasive HER2-overexpressing breast carcinoma, and treated with neoadjuvant chemotherapy, with or without trastuzumab. Kaplan-Meier analysis and Cox regression model were used to assess relapse-free and overall survival, respectively, and according to the presence or the absence of Foxp3 expression in tumor cells. Breast cancer cells were Foxp3+ in 57% of tumors. Foxp3 expression in breast cancer cells was associated with better relapse-free (P = 0.005) and overall survival (P = 0.03). By multivariate analysis, the presence of Foxp3+ tumor cells produced an independent prognostic factor for both better relapse-free (P = 0.006) and overall survival (P = 0.03). These findings indicate that the presence of Foxp3+ tumor cells represents a new independent prognostic factor of improved outcome in HER2-overexpressing breast carcinoma, which could help identify high-risk patients for additional therapies after neoadjuvant chemotherapy.

Induction of transglutaminase 2 by a liver X receptor/retinoic acid receptor alpha pathway increases the clearance of apoptotic cells by human macrophages.

RATIONALE: Liver X receptors (LXRs) are oxysterol-activated nuclear receptors that are involved in the control of cholesterol homeostasis and inflammatory response. Human monocytes and macrophages express high levels of these receptors and are appropriate cells to study the response to LXR agonists. OBJECTIVE: The purpose of this study was to identify new LXR targets in human primary monocytes and macrophages and the consequences of their activation. METHODS AND RESULTS: We show that LXR agonists significantly increase the mRNA and protein levels of the retinoic acid receptor (RAR)alpha in primary monocytes and macrophages. LXR agonists promote RARalpha gene transcription through binding to a specific LXR response element on RARalpha gene promoter. Preincubation of monocytes or macrophages with LXR agonists before RARalpha agonist treatment enhances synergistically the expression of several RARalpha target genes. One of these genes encodes transglutaminase (TGM)2, a key factor required for macrophage phagocytosis. Accordingly, the combination of LXR and RARalpha agonists at concentrations found in human atherosclerotic plaques markedly enhances the capabilities of macrophages to engulf apoptotic cells in a TGM2-dependent manner. CONCLUSIONS: These results indicate an important role for LXRs in the control of phagocytosis through an RARalpha-TGM2-dependent mechanism. A combination of LXR/RARalpha agonists that may operate in atherosclerosis could also constitute a promising strategy to improve the clearance of apoptotic cells by macrophages in other pathological situations.

Follicular helper-T cells restore CD8+-dependent antitumor immunity and anti-PD-L1/PD-1 efficacy.

BACKGROUND: T follicular helper cells (Tfh) are essential to shape B cell response during germinal center formation. Tfh accumulation has been reported in various human cancers, with positive or negative prognostic roles. However, the mechanisms explaining the accumulation of Tfh and their role in cancer remain obscure. METHODS: In vitro differentiated and mouse cell sorted Tfh phenotype was evaluated by flow cytometry and quantitative PCR (qPCR). Antitumor effect of Tfh was evaluated by adoptive transfer in different tumor-bearing mice models. The involvement of immune cells, cytokines and chemokines was evaluated, using depleting antibodies. Chemokines and cytokines expression and production were evaluated by qPCR and ELISA. In human, the impact of immune cells and chemokines on survival was evaluated by analyzing transcriptomic data from public databases and from our own patient cohorts. RESULTS: In this study, we show that Tfh exert an antitumor immune effect in a CD8+-dependent manner. Tfh produce interleukin-21, which sustains proliferation, viability, cytokine production and cytotoxic functions of exhausted T cells. The presence of Tfh is required for efficacy of antiprogrammed cell death ligand-1 therapy. Tfh accumulate in the tumor bed and draining lymph nodes in different mouse cancer models. This recruitment is due to the capacity of transforming growth factor ß to drive Chemokine (C-X-C motif) Ligand 13 expression, a chemoattractant of Tfh, by intratumor CD8+ T cells. Accumulation of Tfh and exhausted CD8+ T cells predicts cancer outcome in various cancer types. In patients treated with anti-programmed cell death-1 mAb, accumulation of Tfh and CD8+ at the tumor site is associated with outcome. CONCLUSION: This study provides evidence that CD8+/Tfh crosstalk is important in shaping antitumor immune response generated by immunotherapy.

Liver X receptor-mediated induction of cholesteryl ester transfer protein expression is selectively impaired in inflammatory macrophages.

OBJECTIVE: Cholesteryl ester transfer protein (CETP) is a target gene for the liver X receptor (LXR). The aim of this study was to further explore this regulation in the monocyte-macrophage lineage and its modulation by lipid loading and inflammation, which are key steps in the process of atherogenesis. METHODS AND RESULTS: Exposure of bone marrow-derived macrophages from human CETP transgenic mice to the T0901317 LXR agonist increased CETP, PLTP, and ABCA1 mRNA levels. T0901317 also markedly increased CETP mRNA levels and CETP production in human differentiated macrophages, whereas it had no effect on CETP expression in human peripheral blood monocytes. In inflammatory mouse and human macrophages, LXR-mediated CETP gene upregulation was inhibited, even though ABCA1, ABCG1, and SREBP1c inductions were maintained. The inhibition of CETP gene response to LXR agonists in inflammatory cells was independent of lipid loading (ie, oxidized LDL increased CETP production in noninflammatory macrophages with a synergistic effect of synthetic LXR agonists). CONCLUSIONS: LXR-mediated induction of human CETP expression is switched on during monocyte-to-macrophage differentiation, is magnified by lipid loading, and is selectively lost in inflammatory macrophages, which suggests that inflammatory cells may not increase the circulating CETP pool on LXR agonist treatment.