Activation of endogenous glucocorticoids by HSD11B1 inhibits the antitumor immune response in renal cancer.

Although immune-based therapies have revolutionized the management of cancer, novel approaches are urgently needed to improve their outcome. We investigated the role of endogenous steroids in the resistance to cancer immunotherapy, as these have strong immunomodulatory functions. Using a publicly available database, we found that the intratumoral expression of 11 beta-hydroxysteroid dehydrogenase type 1 (HSD11B1), which regenerates inactive glucocorticoids into active glucocorticoids, was associated with poor clinical outcome and correlated with immunosuppressive gene signatures in patients with renal cell carcinoma (RCC). HSD11B1 was mainly expressed in tumor-infiltrating immune myeloid cells as seen by immunohistochemistry in RCC patient samples. Using peripheral blood mononuclear cells from healthy donors or immune cells isolated from the tumor of RCC patients, we showed that the pharmacological inhibition of HSD11B1 improved the response to the immune checkpoint inhibitor anti-PD-1. In a subcutaneous mouse model of renal cancer, the combination of an HSD11B1 inhibitor with anti-PD-1 treatment increased the proportion of tumor-infiltrating dendritic cells. In an intrarenal mouse tumor model, HSD11B1 inhibition increased the survival of mice treated with anti-PD-1. In addition, inhibition of HSD11B1 sensitized renal tumors in mice to immunotherapy with resiquimod, a Toll-like receptor 7 agonist. Mechanistically, we demonstrated that HSD11B1 inhibition combined with resiquimod increased T cell-mediated cytotoxicity to tumor cells by stimulating the antigen-presenting capacity of dendritic cells. In conclusion, these results support the use of HSD11B1 inhibitors to improve the outcome of immunotherapy in renal cancer and highlight the role of the endogenous glucocorticoid metabolism in the efficacy of immunotherapy.

Harnessing the immune system to fight cancer with Toll-like receptor and RIG-I-like receptor agonists.

Cancer immunotherapy has come of age with the advent of immune checkpoint inhibitors. In this article we review how agonists for receptors of the innate immune system, the Toll-like receptors and the RIG-I-like receptors, impact anticancer immune responses. Treatment with these agonists enhances the activity of anticancer effector cells, such as cytotoxic T cells and NK cells, and at the same time blocks the activity of immunosuppressive cell types such as regulatory T cells and myeloid-derived suppressor cells. These compounds also impact the recruitment of immune cells to the tumor. The phenomena of pattern-recognition receptor tolerance and reprogramming and their implications for immunotherapy are discussed. Finally, novel delivery systems that target the immune-stimulating drugs to the tumor or the tumor-draining lymph nodes to enhance their efficacy and safety are presented.

Leptin, BMI, and a Metabolic Gene Expression Signature Associated with Clinical Outcome to VEGF Inhibition in Colorectal Cancer.

VEGF (vascular endothelial growth factor) signaling inhibitors are widely used in different cancer types; however, patient selection remains a challenge. Analyses of samples from a phase III clinical trial in metastatic colorectal cancer testing chemotherapy versus chemotherapy with the small molecule VEGF receptors inhibitor cediranib identified circulating leptin levels, BMI, and a tumor metabolic and angiogenic gene expression signature associated with improved clinical outcome in patients treated with cediranib. Patients with a glycolytic and hypoxic/angiogenic profile were associated with increased benefit from cediranib, whereas patients with a high lipogenic, oxidative phosphorylation and serine biosynthesis signature did not gain benefit. These findings translated to pre-clinical tumor xenograft models where the same metabolic gene expression profiles were associated with in vivo sensitivity to cediranib as monotherapy. These findings suggest a link between patient physiology, tumor biology, and response to antiangiogenics, which may guide patient selection for VEGF therapy in the future.

Mechanisms that influence tumour response to VEGF-pathway inhibitors.

There has been significant investment in developing novel therapies to target solid tumour vasculature. Different technical approaches have been utilized with the aim of inhibiting tumour angiogenesis or compromising the function or stability of pre-existing tumour blood vessels. The vascular endothelial growth factor (VEGF) signalling axis remains the most widely studied, with biological and small-molecule therapeutics now registered for clinical use. However, despite these successes, the activity of these agents is not as widespread as was first postulated. The present review discusses the clinical successes of the VEGF inhibitors, the factors that may limit their utility, and the potential opportunities to maximize benefit from treatment with these agents in the future.

Bile acids alter male fertility through G-protein-coupled bile acid receptor 1 signaling pathways in mice.

UNLABELLED: Bile acids (BAs) are signaling molecules that are involved in many physiological functions, such as glucose and energy metabolism. These effects are mediated through activation of the nuclear and membrane receptors, farnesoid X receptor (FXR-α) and TGR5 (G-protein-coupled bile acid receptor 1; GPBAR1). Although both receptors are expressed within the testes, the potential effect of BAs on testis physiology and male fertility has not been explored thus far. Here, we demonstrate that mice fed a diet supplemented with cholic acid have reduced fertility subsequent to testicular defects. Initially, germ cell sloughing and rupture of the blood-testis barrier occur and are correlated with decreased protein accumulation of connexin-43 (Cx43) and N-cadherin, whereas at later stages, apoptosis of spermatids is observed. These abnormalities are associated with increased intratesticular BA levels in general and deoxycholic acid, a TGR5 agonist, in particular. We demonstrate here that Tgr5 is expressed within the germ cell lineage, where it represses Cx43 expression through regulation of the transcriptional repressor, T-box transcription factor 2 gene. Consistent with this finding, mice deficient for Tgr5 are protected against the deleterious testicular effects of BA exposure. CONCLUSIONS: These data identify the testis as a new target of BAs and emphasize TGR5 as a critical element in testicular pathophysiology. This work may open new perspectives on the potential effect of BAs on testis physiology during liver dysfunction.

Tumor stromal architecture can define the intrinsic tumor response to VEGF-targeted therapy.

PURPOSE: The aim of the study was to investigate the vascular and stromal architecture of preclinical tumor models and patient tumor specimens from malignancies with known clinical outcomes to VEGFi treatment, to gain insight into potential determinants of intrinsic sensitivity and resistance. EXPERIMENTAL DESIGN: The tumor stroma architecture of preclinical and clinical tumor samples were analyzed by staining for CD31 and α-smooth muscle actin (α-SMA). Tumor models representative of each phenotype were then tested for sensitivity to the VEGFR2-blocking antibody DC101. RESULTS: Human tumor types with high response rates to VEGF inhibitors (e.g., renal cell carcinoma) have vessels distributed amongst the tumor cells (a "tumor vessel" phenotype, TV). In contrast, those malignancies where single-agent responses are lower, such as non-small cell lung cancer (NSCLC), display a complex morphology involving the encapsulation of tumor cells within stroma that also supports the majority of vessels (a "stromal vessel" phenotype). Only 1 of 31 tumor xenograft models displayed the stromal vessel phenotype. Tumor vessel models were sensitive to VEGFR2-blocking antibody DC101, whereas the stromal vessel models were exclusively refractory. The tumor vessel phenotype was also associated with a better Response Evaluation Criteria in Solid Tumors (RECIST) response to bevacizumab + chemotherapy in metastatic colorectal cancer (CRC). CONCLUSION: The tumor stromal architecture can differentiate between human tumor types that respond to a VEGF signaling inhibitor as single-agent therapy. In addition to reconciling the clinical experience with these agents versus their broad activity in preclinical models, these findings may help to select solid tumor types with intrinsic sensitivity to a VEGFi or other vascular-directed therapies.

Liver x receptors protect from development of prostatic intra-epithelial neoplasia in mice.

LXR (Liver X Receptors) act as "sensor" proteins that regulate cholesterol uptake, storage, and efflux. LXR signaling is known to influence proliferation of different cell types including human prostatic carcinoma (PCa) cell lines. This study shows that deletion of LXR in mouse fed a high-cholesterol diet recapitulates initial steps of PCa development. Elevation of circulating cholesterol in Lxrαß-/- double knockout mice results in aberrant cholesterol ester accumulation and prostatic intra-epithelial neoplasia. This phenotype is linked to increased expression of the histone methyl transferase EZH2 (Enhancer of Zeste Homolog 2), which results in the down-regulation of the tumor suppressors Msmb and Nkx3.1 through increased methylation of lysine 27 of histone H3 (H3K27) on their promoter regions. Altogether, our data provide a novel link between LXR, cholesterol homeostasis, and epigenetic control of tumor suppressor gene expression.

Lack of liver X receptors leads to cell proliferation in a model of mouse dorsal prostate epithelial cell.

Recent studies underline the implication of Liver X Receptors (LXRs) in several prostate diseases such as benign prostatic hyperplasia (BPH) and prostate cancer. In order to understand the molecular mechanisms involved, we derived epithelial cells from dorsal prostate (MPECs) of wild type (WT) or Lxrαß-/- mice. In the WT MPECs, our results show that LXR activation reduces proliferation and correlates with the modification of the AKT-survival pathway. Moreover, LXRs regulate lipid homeostasis with the regulation of Abca1, Abcg1 and Idol, and, in a lesser extent, Srebp1, Fas and Acc. Conversely cells derived from Lxrαß-/- mice show a higher basal phosphorylation and consequently activation of the survival/proliferation transduction pathways AKT and MAPK. Altogether, our data point out that the cell model we developed allows deciphering the molecular mechanisms inducing the cell cycle arrest. Besides, we show that activated LXRs regulate AKT and MAPK transduction pathways and demonstrate that LXRs could be good pharmacological targets in prostate disease such as cancer.

LXR, prostate cancer and cholesterol: the Good, the Bad and the Ugly.

Cholesterol is a fundamental molecule for life. Located in the cell membrane, this sterol participates to the cell signaling of growth factors. Inside the cell it can be converted in hormones such as androgens or modulate the immune response. Such important functions could not be solely dependent of external supply by diet hence de novo synthesis could occur from acetate in almost all mammalian cells. If a deficiency in cholesterol sourcing leads to development troubles, overstocking has been associated to various diseases such as atherosclerosis and cancers. Cholesterol homeostasis should thus be tightly regulated at the uptake, de novo synthesis, storage and export processes. Various transcription factors have been described these last years as important to regulate cholesterol levels. Besides, synthetic molecules have been developed for many years to modulate cholesterol synthesis, such as statins. Many articles have associated prostate cancer, whose incidence is constantly increasing, to cholesterol disequilibrium. Targeting cholesterol could thus be a new pharmacological hit to counteract the initiation, development and/or progression of prostate cancer. Among the transcription factors regulating cholesterol homeostasis, the nuclear receptors Liver X Receptors (LXRs) control cholesterol uptake and export. Targeting the LXRs offers a new field of investigation to treat cancer. This review highlights the molecular relationships among LXRs, prostate cancer and cholesterol and why LXRs have good chance to be targeted one day in this tumor. LXRs, prostate cancer and cholesterol, more than a "Ménage à trois", The Good, the Bad and the Ugly.

A systems biology approach to the hepatic role of the oxysterol receptor LXR in the regulation of lipogenesis highlights a cross-talk with PPARα.

The Liver X Receptors (LXRs) α and ß and the Peroxisome Proliferator-Activated Receptor α (PPARα) are transcription factors that belong to class II nuclear receptors. They drive the expression of genes involved in hepatic lipid homeostasis and therefore are important targets for the prevention and treatment of nonalcoholic fatty liver disease (NAFLD). LXRs and PPARα are regulated by endogenous ligands, oxysterols and fatty acid derived molecules, respectively. In the liver, pharmacological activation of LXRs leads to the over-expression of genes involved in de novo lipogenesis, while PPARα is critical for fatty acid catabolism in nutrient deprivation. Even if these two nuclear receptors seemed to play opposite parts, recent studies have highlighted that PPARα also influence the expression of genes involved in fatty acids synthesis. In this study, we used pharmacological approaches and genetically engineered mice to investigate the cross-talk between LXRs and PPARα in the regulation of genes responsible for lipogenesis. We first investigated the effect of T0901317 and fenofibrate, two synthetic agonists of LXRs and PPARα, respectively. As expected, T0901317 and fenofibrate induce expression of genes involved LXR-dependent and PPARα-dependent lipogenic responses. Considering such overlapping effect, we then tested whether LXR agonist may influence PPARα driven response and vice versa. We show that the lack of PPARα does not influence the effects of T0901317 on lipogenic genes expression. However, PPARα deficiency prevents the up-regulation of genes involved in ω-hydroxylation that are induced by the LXR agonist. In addition, over-expression of lipogenic genes in response to fenofibrate is decreased in LXR knockout mice as well as the expression of PPARα target genes involved in fatty acid oxidation. Altogether, our work provides in vivo evidence for a central interconnection between nuclear receptors that drive hepatic lipid metabolism in response to oxysterol and fatty acids.

Lxrα regulates the androgen response in prostate epithelium.

Benign prostatic hyperplasia is a nonmalignant enlargement of the prostate that commonly occurs in older men. We show that liver X receptor (Lxr)-α knockout mice (lxrα(-/-)) develop ventral prostate hypertrophy, correlating with an overaccumulation of secreted proteins in prostatic ducts and an alteration of vesicular trafficking in epithelial cells. In the fluid of the lxrα(-/-) prostates, spermine binding protein is highly accumulated and shows a 3000-fold increase of its mRNA. This overexpression is mediated by androgen hypersensitivity in lxrα(-/-) mice, restricted to the ventral prostate. Generation of chimeric recombinant prostates demonstrates that Lxrα is involved in the establishment of the epithelial-mesenchymal interactions in the mouse prostate. Altogether these results point out the crucial role of Lxrα in the homeostasis of the ventral prostate and suggest lxrα(-/-) mice may be a good model to investigate the molecular mechanisms of benign prostatic hyperplasia.

Dietary cholesterol-induced post-testicular infertility.

This work shows that an overload of dietary cholesterol causes complete infertility in dyslipidemic male mice (the Liver X Receptor-deficient mouse model). Infertility resulted from post-testicular defects affecting the fertilizing potential of spermatozoa. Spermatozoa of cholesterol-fed lxr-/- animals were found to be dramatically less viable and motile, and highly susceptible to undergo a premature acrosome reaction. We also provide evidence, that this lipid-induced infertility is associated with the accelerated appearance of a highly regionalized epididymal phenotype in segments 1 and 2 of the caput epididymidis that was otherwise only observed in aged LXR-deficient males. The epididymal epithelial phenotype is characterized by peritubular accumulation of cholesteryl ester lipid droplets in smooth muscle cells lining the epididymal duct, leading to their transdifferentiation into foam cells that eventually migrate through the duct wall, a situation that resembles the inflammatory atherosclerotic process. These findings establish the high level of susceptibility of epididymal sperm maturation to dietary cholesterol overload and could partly explain reproductive failures encountered by young dyslipidemic men as well as ageing males wishing to reproduce.

Liver X receptors, lipids and their reproductive secrets in the male.

Liver X receptor (LXR) α and LXRß belong to the nuclear receptor superfamily. For many years, they have been called orphan receptors, as no natural ligand was identified. In the last decade, the LXR natural ligands have been shown to be oxysterols, molecules derived from cholesterol. While these nuclear receptors have been abundantly studied for their roles in the regulation of lipid metabolism, it appears that they also present crucial activities in reproductive organs such as testis and epididymis, as well as prostate. Phenotypic analyses of mice lacking LXRs (lxr-/-) pointed out their physiological activities in the various cells and organs regulating reproductive functions. This review summarizes the impact of LXR-deficiency in male reproduction, highlighting the novel information coming from the phenotypic analyses of lxrα-/-, lxrß-/- and lxrα;ß-/- mice. This article is part of a Special Issue entitled: Translating nuclear receptor from health to disease.

Targeting liver X receptors in human health: deadlock or promising trail?

INTRODUCTION: Liver X receptors (LXR) are transcription factors that belong to the nuclear receptor superfamily. Natural derivatives of cholesterol, known as oxysterols, have been identified as agonistic ligands of LXR. They are thus mainly considered to be intracellular cholesterol 'sensors' whose activation leads to decreased plasma cholesterol. Their implication in other physiologic processes currently prevents their use as therapeutic targets, because of potentially deleterious side effects. AREAS COVERED: The various LXR agonists and antagonists, along with the physiological functions of LXR. Putative clinical targets including atherosclerosis, diabetes, Alzheimer's disease, skin disorders, reproductive disorders and cancer. EXPERT OPINION: LXR are promising pharmacological targets because of the high potential to develop ligands owing to the variety of natural or synthetic agonists. Three aspects should be developed to select a LXR-ligand for treatment of human disease: bio-availability; isoform specificity; tissue specificity. This will allow the development of selective liver X modulators (SLiMs). The challenge is to overcome deleterious side effects to establish LXR as new pharmacological targets.

Absence of nuclear receptors for oxysterols liver X receptor induces ovarian hyperstimulation syndrome in mice.

Ovarian hyperstimulation syndrome is a frequent complication occurring during in vitro fertilization cycles. It is characterized by a massive ovarian enlargement associated with an accumulation of extra vascular fluid. Here we show that liver X receptor (LXR)-alpha and LXR-beta deficient mice present many clinical and biological signs of ovarian hyperstimulation syndrome: ovarian enlargement, hemorrhagic corpora lutea, increased ovarian vascular permeability, and elevated estradiol. Ovulation stimulation resulted in excessive ovarian response to exogenous gonadotropins because follicle number and estradiol production were higher in transgenic mice. LXR deficiency also leads to perturbations in general inflammatory status, associated with ovarian il-6 deregulation. Upon treatment with the synthetic LXR agonist T09101317, serum estradiol and expression of star and cyp11a1 genes were markedly increased in wild-type mice, showing that LXRs are key regulators of ovarian steroidogenesis. These results suggest that LXRs control the ovulation by regulating endocrine and vascular processes.