Blocking Antibodies Targeting the CD39/CD73 Immunosuppressive Pathway Unleash Immune Responses in Combination Cancer Therapies

Immune checkpoint inhibitors have revolutionized cancer treatment. However, many cancers are resistant to ICIs, and the targeting of additional inhibitory signals is crucial for limiting tumor evasion. The production of adenosine via the sequential activity of CD39 and CD73 ectoenzymes participates to the generation of an immunosuppressive tumor microenvironment. In order to disrupt the adenosine pathway, we generated two antibodies, IPH5201 and IPH5301, targeting human membrane-associated and soluble forms of CD39 and CD73, respectively, and efficiently blocking the hydrolysis of immunogenic ATP into immunosuppressive adenosine. These antibodies promoted antitumor immunity by stimulating dendritic cells and macrophages and by restoring the activation of T cells isolated from cancer patients. In a human CD39 knockin mouse preclinical model, IPH5201 increased the anti-tumor activity of the ATP-inducing chemotherapeutic drug oxaliplatin. These results support the use of anti-CD39 and anti-CD73 monoclonal antibodies and their combination with immune checkpoint inhibitors and chemotherapies in cancer.

The Emerging Role of the IL-17B/IL-17RB Pathway in Cancer

Among inflammatory mediators, a growing body of evidence emphasizes the contribution of the interleukin 17 (IL-17) cytokine family in malignant diseases. Besides IL-17A, the prototypic member of the IL-17 family, several experimental findings strongly support the role of the IL-17B/IL-17 receptor B (IL-17RB) pathway in tumorigenesis and resistance to anticancer therapies. In mouse models, IL-17B signaling through IL-17RB directly promotes cancer cell survival, proliferation, and migration, and induces resistance to conventional chemotherapeutic agents. Importantly, recent work by our and other laboratories showed that IL-17B signaling dramatically alters the tumor microenvironment by promoting chemokine and cytokine secretion which foster tumor progression. Moreover, the finding that elevated IL-17B is associated with poor prognosis in patients with pancreatic, gastric, lung, and breast cancer strengthens the results obtained in pre-clinical studies and highlights its clinical relevance. Here, we review the current understanding on the IL-17B/IL-17RB expression patterns and biological activities in cancer and highlight issues that remain to be addressed to better characterize IL-17B and its receptor as potential targets for enhancing the effectiveness of the existing cancer therapies.

Glucocorticoid-dependent REDD1 expression reduces muscle metabolism to enable adaptation under energetic stress

Background

Skeletal muscle atrophy is a common feature of numerous chronic pathologies and is correlated with patient mortality. The REDD1 protein is currently recognized as a negative regulator of muscle mass through inhibition of the Akt/mTORC1 signaling pathway. REDD1 expression is notably induced following glucocorticoid secretion, which is a component of energy stress responses.

Results

Unexpectedly, we show here that REDD1 instead limits muscle loss during energetic stresses such as hypoxia and fasting by reducing glycogen depletion and AMPK activation. Indeed, we demonstrate that REDD1 is required to decrease O₂ and ATP consumption in skeletal muscle via reduction of the extent of mitochondrial-associated endoplasmic reticulum membranes (MAMs), a central hub connecting energy production by mitochondria and anabolic processes. In fact, REDD1 inhibits ATP-demanding processes such as glycogen storage and protein synthesis through disruption of the Akt/Hexokinase II and PRAS40/mTORC1 signaling pathways in MAMs. Our results uncover a new REDD1-dependent mechanism coupling mitochondrial respiration and anabolic processes during hypoxia, fasting, and exercise.

Conclusions

Therefore, REDD1 is a crucial negative regulator of energy expenditure that is necessary for muscle adaptation during energetic stresses. This present study could shed new light on the role of REDD1 in several pathologies associated with energetic metabolism alteration, such as cancer, diabetes, and Parkinson’s disease.

Electronic supplementary material

The online version of this article (10.1186/s12915-018-0525-4) contains supplementary material, which is available to authorized users.

Abstract 1602: Generation of anti-IL-17B antibodies neutralizing IL-17B-mediated alterations of the immune microenvironment, promotion of tumor cell initiating capacity and chemoresistance

Interleukin 17B (IL-17B) is a pro-inflammatory cytokine that belongs to a family encompassing 6 interleukins (IL-17A to F) and binds to the IL-17 receptor B (IL-17RB). Recently, amplified IL-17B/IL-17RB signaling was found critical for breast and pancreatic tumorigenesis and elevated expression of IL-17RB has been associated with the shortest survival rates in patients with breast or pancreatic cancer. Using IL-17B knock-out (IL-17B KO) mice we demonstrate here that melanoma, fibrosarcoma and breast cancer cell tumorigenicity is strongly impaired in immunocompetent IL-17B KO mice compared to WT littermates, including a large number of tumor free mice. Reduced tumor incidence in IL-17B KO mice is associated with alterations of the immune tumor microenvironment especially within innate lymphocyte and myeloid sub-populations. We further demonstrate that IL-17B is a key cytokine shaping the tumor initiating cancer cell niche. Indeed, MDA-MB-468 human breast cancer cells overexpressing IL-17B exhibit 10 times higher frequency of tumor initiating cells when xenografted at a serial limiting dilution in nude mice. Tumor progression is, again, associated with alterations of NK cells within the tumor microenvironment and with increased percentages of CD44hi/CD24lo tumor cells, a phenotype associated with breast cancer stem cells (CSC). This is associated with resistance to conventional chemotherapeutic agents such as taxol, an effect that is totally abrogated by disrupting IL-17B-IL-17RB signaling with a neutralizing antibody. Altogether our results point out the key role of IL-17B in regulating the immune microenvironment as well as cardinal features of CSC, one of the alleged causes of resistance to therapy and tumor relapse. Thereby, IL-17B and its receptor appear as potential therapeutic targets for cancer immunotherapy. Collectively, these data support the ongoing development of IL-17B neutralizing antibodies.

Citation Format: Emilie Laprevotte, Aurélie Docquier, Jeremy Bastid, Cécile Déjou, Marion Lapierre, Gilles Alberici, Armand Bensussan, Jean-François Eliaou, Nathalie Bonnefoy. Generation of anti-IL-17B antibodies neutralizing IL-17B-mediated alterations of the immune microenvironment, promotion of tumor cell initiating capacity and chemoresistance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1602. doi:10.1158/1538-7445.AM2017-1602

REDD1 deletion prevents dexamethasone-induced skeletal muscle atrophy

REDD1 (regulated in development and DNA damage response 1) has been proposed to inhibit the mechanistic target of rapamycin complex 1 (mTORC1) during in vitro hypoxia. REDD1 expression is low under basal conditions but is highly increased in response to several catabolic stresses, like hypoxia and glucocorticoids. However, REDD1 function seems to be tissue and stress dependent, and its role in skeletal muscle in vivo has been poorly characterized. Here, we investigated the effect of REDD1 deletion on skeletal muscle mass, protein synthesis, proteolysis, and mTORC1 signaling pathway under basal conditions and after glucocorticoid administration. Whereas skeletal muscle mass and typology were unchanged between wild-type (WT) and REDD1-null mice, oral gavage with dexamethasone (DEX) for 7 days reduced tibialis anterior and gastrocnemius muscle weights as well as tibialis anterior fiber size only in WT. Similarly, REDD1 deletion prevented the inhibition of protein synthesis and mTORC1 activity (assessed by S6, 4E-BP1, and ULK1 phosphorylation) observed in gastrocnemius muscle of WT mice following single DEX administration for 5 h. However, our results suggest that REDD1-mediated inhibition of mTORC1 in skeletal muscle is not related to the modulation of the binding between TSC2 and 14-3-3. In contrast, our data highlight a new mechanism involved in mTORC1 inhibition linking REDD1, Akt, and PRAS40. Altogether, these results demonstrated in vivo that REDD1 is required for glucocorticoid-induced inhibition of protein synthesis via mTORC1 downregulation. Inhibition of REDD1 may thus be a strategy to limit muscle loss in glucocorticoid-mediated atrophy.

Negative regulation of estrogen signaling by ERβ and RIP140 in ovarian cancer cells

In hormone-dependent tissues such as breast and ovary, tumorigenesis is associated with an altered expression ratio between the two estrogen receptor (ER) subtypes. In this study, we investigated the effects of ERβ ectopic expression on 17β-estradiol (E2)-induced transactivation and cell proliferation in ERα-positive BG1 ovarian cancer cells. As expected, ERβ expression strongly decreased the mitogenic effect of E2, significantly reduced E2-dependent transcriptional responses (both on a stably integrated estrogen response element [ERE] reporter gene and on E2-induced mRNAs), and strongly enhanced the formation of ER heterodimers as evidenced by chromatin immunoprecipitation analysis. Inhibition by the ERα-selective ligand propyl pyrazole triol was less marked than with the pan-agonist (E2) or the ERβ-selective (8β-vinyl-estradiol) ligands, indicating that ERβ activation reinforced the inhibitory effects of ERβ. Interestingly, in E2-stimulated BG1 cells, ERβ was more efficient than ERα to regulate the expression of receptor-interacting protein 140 (RIP140), a major ERα transcriptional corepressor. In addition, we found that the RIP140 protein interacted better with ERβ than with ERα (both in vitro and in intact cells by fluorescence cross-correlation spectroscopy). Moreover, RIP140 recruitment on the stably integrated reporter ERE was increased upon ERβ overexpression, and ERβ activity was more sensitive to repression by RIP140. Finally, small interfering RNA-mediated knockdown of RIP140 expression abolished the repressive effect exerted by activated ERβ on the regulation of ERE-controlled transcription by estrogens. Altogether, these data demonstrate the inhibitory effects of ERβ on estrogen signaling in ovarian cancer cells and the key role that RIP140 plays in this phenomenon.

eIF3f: a central regulator of the antagonism atrophy/hypertrophy in skeletal muscle

The eukaryotic initiation factor 3 subunit f (eIF3f) is one of the 13 subunits of the translation initiation factor complex eIF3 required for several steps in the initiation of mRNA translation. In skeletal muscle, recent studies have demonstrated that eIF3f plays a central role in skeletal muscle size maintenance. Accordingly, eIF3f overexpression results in hypertrophy through modulation of protein synthesis via the mTORC1 pathway. Importantly, eIF3f was described as a target of the E3 ubiquitin ligase MAFbx/atrogin-1 for proteasome-mediated breakdown under atrophic conditions. The biological importance of the MAFbx/atrogin-1-dependent targeting of eFI3f is highlighted by the finding that expression of an eIF3f mutant insensitive to MAFbx/atrogin-1 polyubiquitination is associated with enhanced protection against starvation-induced muscle atrophy. A better understanding of the precise role of this subunit should lead to the development of new therapeutic approaches to prevent or limit muscle wasting that prevails in numerous physiological and pathological states such as immobilization, aging, denervated conditions, neuromuscular diseases, AIDS, cancer, diabetes.

This article is part of a Directed Issue entitled: Molecular basis of muscle wasting.

Long-term treatment with the pure anti-estrogen fulvestrant durably remodels estrogen signaling in BG-1 ovarian cancer cells

Most ovarian cancers are estrogen-positive and hormonal treatments using anti-estrogens or aromatase inhibitors are under investigation for treating the tumors that are resistant to conventional therapies. In this study, the long-term effects of two anti-estrogens, namely 4-hydroxytamoxifen and fulvestrant (or ICI182,780), were investigated in ERα-positive BG1 epithelial ovarian cancer cells. To this aim, cells were grown in the presence of anti-estrogen concentrations that were sufficient to saturate the estrogen receptors, but were neither cytotoxic nor cytostatic as indicated by the absence of inhibition of cell proliferation. In these conditions and despite the lack of cytostatic effect of the drugs, long-term treatment (3 months) with the pure anti-estrogen fulvestrant induced a specific, reproducible and irreversible inhibition of ERα expression. This inhibition was accompanied by loss of estrogen-induced cell proliferation and gene expression as indicated by the analysis of several estrogen-responsive genes. ERα down-regulation was not linked to deregulated expression of transcription factors which drive ERα transcription and did not involve DNA methylation or histone deacetylation. Altogether, these results demonstrate that non-cytotoxic concentrations of pure anti-estrogens affect estrogen signaling and might be relevant for the treatment for ovarian cancers.

The RIP140 gene is a transcriptional target of E2F1

RIP140 is a transcriptional coregulator involved in energy homeostasis and ovulation which is controlled at the transcriptional level by several nuclear receptors. We demonstrate here that RIP140 is a novel target gene of the E2F1 transcription factor. Bioinformatics analysis, gel shift assay, and chromatin immunoprecipitation demonstrate that the RIP140 promoter contains bona fide E2F response elements. In transiently transfected MCF-7 breast cancer cells, the RIP140 promoter is transactivated by overexpression of E2F1/DP1. Interestingly, RIP140 mRNA is finely regulated during cell cycle progression (5-fold increase at the G1/S and G2/M transitions). The positive regulation by E2F1 requires sequences located in the proximal region of the promoter (-73/+167), involves Sp1 transcription factors, and undergoes a negative feedback control by RIP140. Finally, we show that E2F1 participates in the induction of RIP140 expression during adipocyte differentiation. Altogether, this work identifies the RIP140 gene as a new transcriptional target of E2F1 which may explain some of the effect of E2F1 in both cancer and metabolic diseases.

The transcriptional coregulator RIP140 represses E2F1 activity and discriminates breast cancer subtypes

PURPOSE

Receptor-interacting protein of 140 kDa (RIP140) is a transcriptional cofactor for nuclear receptors involved in reproduction and energy homeostasis. Our aim was to investigate its role in the regulation of E2F1 activity and target genes both in breast cancer cell lines and in tumor biopsies.

EXPERIMENTAL DESIGN

Glutathione S-transferase pull-down assays, coimmunoprecipitation experiments, and chromatin immunoprecipitation analysis were used to evidence interaction between RIP140 and E2F1. The effects of RIP140 expression on E2F1 activity were determined using transient transfection and quantification of E2F target mRNAs by quantitative real-time PCR. The effect on cell cycle was assessed by fluorescence-activated cell sorting analysis on cells overexpressing green fluorescent protein-tagged RIP140. A tumor microarray data set was used to investigate the expression of RIP140 and E2F1 target genes in 170 breast cancer patients.

RESULTS

We first evidenced the complex interaction between RIP140 and E2F1 and showed that RIP140 represses E2F1 transactivation on various transiently transfected E2F target promoters and inhibits the expression of several E2F1 target genes (such as CCNE1 and CCNB2). In agreement with a role for RIP140 in the control of E2F activity, we show that increasing RIP140 levels results in a reduction in the proportion of cells in S phase in various human cell lines. Finally, analysis of human breast cancers shows that low RIP140 mRNA expression was associated with high E2F1 target gene levels and basal-like tumors.

CONCLUSION

This study shows that RIP140 is a regulator of the E2F pathway, which discriminates luminal- and basal-like tumors, emphasizing the importance of these regulations for a clinical cancer phenotype.