Therapeutic Targeting of LIF Overcomes Macrophage-mediated Immunosuppression of the Local Tumor Microenvironment

PURPOSE

Leukemia inhibitory factor (LIF) is a multifunctional cytokine with numerous reported roles in cancer and is thought to drive tumor development and progression. Characterization of LIF and clinical-stage LIF inhibitors would increase our understanding of LIF as a therapeutic target.

EXPERIMENTAL DESIGN

We first tested the association of LIF expression with transcript signatures representing multiple processes regulating tumor development and progression. Next, we developed MSC-1, a high-affinity therapeutic antibody that potently inhibits LIF signaling and tested it in immune competent animal models of cancer.

RESULTS

LIF was associated with signatures of tumor-associated macrophages (TAM) across 7,769 tumor samples spanning 22 solid tumor indications. In human tumors, LIF receptor was highly expressed within the macrophage compartment and LIF treatment drove macrophages to acquire immunosuppressive capacity. MSC-1 potently inhibited LIF signaling by binding an epitope that overlaps with the gp130 receptor binding site on LIF. MSC-1 showed monotherapy efficacy in vivo and drove TAMs to acquire antitumor and proinflammatory function in syngeneic colon cancer mouse models. Combining MSC-1 with anti-PD1 leads to strong antitumor response and a long-term tumor-free survival in a significant proportion of treated mice.

CONCLUSIONS

Overall, our findings highlight LIF as a therapeutic target for cancer immunotherapy.

Orally administered Odoribacter laneus improves glucose control and inflammatory profile in obese mice by depleting circulating succinate

BACKGROUND

Succinate is produced by both human cells and by gut bacteria and couples metabolism to inflammation as an extracellular signaling transducer. Circulating succinate is elevated in patients with obesity and type 2 diabetes and is linked to numerous complications, yet no studies have specifically addressed the contribution of gut microbiota to systemic succinate or explored the consequences of reducing intestinal succinate levels in this setting.

RESULTS

Using germ-free and microbiota-depleted mouse models, we show that the gut microbiota is a significant source of circulating succinate, which is elevated in obesity. We also show in vivo that therapeutic treatments with selected bacteria diminish the levels of circulating succinate in obese mice. Specifically, we demonstrate that Odoribacter laneus is a promising probiotic based on its ability to deplete succinate and improve glucose tolerance and the inflammatory profile in two independent models of obesity (db/db mice and diet-induced obese mice). Mechanistically, this is partly mediated by the succinate receptor 1. Supporting these preclinical findings, we demonstrate an inverse correlation between plasma and fecal levels of succinate in a cohort of patients with severe obesity. We also show that plasma succinate, which is associated with several components of metabolic syndrome including waist circumference, triglycerides, and uric acid, among others, is a primary determinant of insulin sensitivity evaluated by the euglycemic-hyperinsulinemic clamp.

CONCLUSIONS

Overall, our work uncovers O. laneus as a promising next-generation probiotic to deplete succinate and improve glucose tolerance and obesity-related inflammation. Video Abstract.

Glycogen accumulation in adipocyte precursors from elderly and obese subjects triggers inflammation via SIRT1/6 signaling

Dysfunctional adipocyte precursors have emerged as key determinants for obesity- and aging-related inflammation, but the mechanistic basis remains poorly understood. Here, we explored the dysfunctional adipose tissue of elderly and obese individuals focusing on the metabolic and inflammatory state of human adipose-derived mesenchymal stromal cells (hASCs), and on sirtuins, which link metabolism and inflammation. Both obesity and aging impaired the differentiation potential of hASCs but had a different impact on their proliferative capacity. hASCs from elderly individuals (≥65 years) showed an upregulation of glycolysis-related genes, which was accompanied by increased lactate secretion and glycogen storage, a phenotype that was exaggerated by obesity. Multiplex protein profiling revealed that the metabolic switch to glycogenesis was associated with a pro-inflammatory secretome concomitant with a decrease in the protein expression of SIRT1 and SIRT6. siRNA-mediated knockdown of SIRT1 and SIRT6 in hASCs from lean adults increased the expression of pro-inflammatory and glycolysis-related markers, and enforced glycogen deposition by overexpression of protein targeting to glycogen (PTG) led to a downregulation of SIRT1/6 protein levels, mimicking the inflammatory state of hASCs from elderly subjects. Overall, our data point to a glycogen-SIRT1/6 signaling axis as a driver of age-related inflammation in adipocyte precursors.

Survivin drives tumor-associated macrophage reprogramming: a novel mechanism with potential impact for obesity

PURPOSE

Recent studies point to adipose-derived stem cells (ASCs) as a link between obesity and cancer. We aimed to determine whether survivin, which is highly secreted by ASCs from subjects with obesity, might drive a pro-tumoral phenotype in macrophages.

METHODS

The effect of ASC conditioned medium on the macrophage phenotype was assessed by expression studies. Survivin intracellular localization and internalization were examined by subcellular fractionation and immunofluorescence, respectively. Loss- and gain-of-function studies were performed using adenoviral vectors, and gene expression patterns, migration and invasion capacities of cancer cells were examined. Heterotypic cultures of ASCs, macrophages and cancer cells were established to mimic the tumor microenvironment. Survivin-blocking experiments were used to determine the impact of survivin on both macrophages and cancer cells. Immunohistochemical analysis of survivin was performed in macrophages from ascitic fluids of cancer patients and healthy controls.

RESULTS

We found that obese-derived ASCs induced a phenotypic switch in macrophages characterized by the expression of both pro- and anti-inflammatory markers. Macrophages were found to internalize extracellular survivin, generating hybrid macrophages with a tumor-associated phenotype that included secretion of survivin. Exogenous expression of survivin in macrophages generated a similar phenotype and enhanced the malignant characteristics of cancer cells by a mechanism dependent on survivin phosphorylation at threonine 34. Survivin secreted by both ASCs from subjects with obesity and tumor-associated macrophages synergistically boosted the malignancy of cancer cells. Importantly, survivin was mainly detected in ascites-associated macrophages from patients with a malignant diagnosis.

CONCLUSION

Our data indicate that survivin may serve as a molecular link between obesity and cancer and as a novel marker for tumor-associated macrophages.

Abstract 1751: MSC-1 is a first-in-class humanized monoclonal antibody that modulates the tumor microenvironment by inhibiting a novel cancer immunotherapy target, LIF

Leukemia Inhibitory Factor (LIF) is a member of the IL-6 family of cytokines and is involved in many physiological and pathological processes including the promotion of an immunosuppressive environment to support embryo implantation, down-regulation of autoimmune processes and the regulation of stem cell homeostasis and differentiation. In cancer, LIF is hypothesized to have a complex role tumor development and progression, creating an immunosuppressive tumor microenvironment as well as promoting the activity of cancer initiating cells (CICs). LIF is highly expressed in a subset of tumors across multiple tumor types, e.g. glioblastoma multiforme (GBM), non-small cell lung cancer (NSCLC), colon, ovarian, prostate, and pancreatic cancer, and correlates with poor prognosis. Given the pleiotropic role LIF is hypothesized to play in cancer, inhibition of LIF represents an exciting new therapeutic concept sitting at the intersection of two key therapeutic approaches in oncology: blockade of tumor evasion of the immune system and blockade of tumor growth via inhibition of CICs. We have identified and developed MSC-1, a first-in-class humanized IgG1 monoclonal antibody that is a potent and selective inhibitor of LIF. MSC-1 cross reacts with mouse and non-human primate LIF and inhibits LIF signaling by blocking the recruitment of gp130 to the LIF-LIFR-gp130 signaling complex. The efficacy of MSC-1 was evaluated in multiple mouse tumor models and the mechanism of action investigated. LIF inhibition with MSC-1 or shRNAs reduced tumor growth in multiple syngeneic tumor models (NSCLC, ovarian and colon), and clear target engagement was shown for MSC-1. Investigations into the mechanism of action identified that inhibition of LIF with MSC-1 reprogrammed the tumor microenvironment by decreasing immunosuppressive M2 macrophages and increasing the number of intratumoral NK cells and total/activated T cells. MSC-1 also decreased immunosuppressive M2 macrophages in an orthotopic GBM xenograft model and human GBM organotypic tumor slices in an ex vivo model. Similarly, immunosuppressive macrophage genes were decreased when monocytes were co-cultured with supernatants from a GBM cell line in which LIF expression had been knocked-down. Given the effects of MSC-1 on intratumoral immune cells, we hypothesized that MSC-1 could be effectively combined with checkpoint inhibitors and we are currently evaluating MSC-1/checkpoint inhibitor combination therapy. Taken together, these findings form the basis of a robust therapeutic hypothesis, whereby MSC-1 treatment will lead to clinical activity in multiple cancer indications. A Phase I dose-escalation and expansion study of MSC-1 is planned to initiate early 2018 in patients with advanced solid tumors that will incorporate target engagement and PD biomarkers, as well as safety and efficacy endpoints.

Citation Format: Angus Sinclair, Robin Hallett, Patricia Giblin, Isabel Huber-Ruano, Judit Anido, Naimish Pandya, Kimberly Hoffman, Ada Sala, Monica Pascual, Vanessa Chigancas, Swetha Raman, Johan Fransson, Jean-Philippe Julien, Robert Wasserman, Jeanne Magram, Joan Seoane. MSC-1 is a first-in-class humanized monoclonal antibody that modulates the tumor microenvironment by inhibiting a novel cancer immunotherapy target, LIF [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1751.

An antisense oligonucleotide targeting TGF-β2 inhibits lung metastasis and induces CD86 expression in tumor-associated macrophages

Background

The transforming growth factor (TGF)-β pathway is a well-described inducer of immunosuppression and can act as an oncogenic factor in advanced tumors. Several preclinical and clinical studies show that the TGF-β pathway can be considered a promising molecular target for cancer therapy. The human genome has three TGF-β isoforms and not much is known about the oncogenic response to each of the isoforms. Here, we studied the antitumor response to ISTH0047, a recently developed locked nucleic acid-modified antisense oligonucleotide targeting TGF-β2.

Materials and methods

We have studied the anticancer response to ISTH0047 using gymnotic delivery in tumor cell cultures and in in vivo preclinical orthotopic mouse models for primary tumors (breast and kidney tumors) and lung metastasis.

Results

We observed that ISTH0047 is able to significantly reduce TGF-β2 mRNA and protein levels without altering the levels of TGF-β1 and TGF-β3. ISTH0047 prevented lung metastasis in syngeneic orthotopic renal cell carcinoma (RENCA) and breast cancer (4T1) tumor models. In addition, using an orthotopic xenograft model of a lung cancer cell line (CRL5807) that mainly expresses TGF-β2, we observed that ISTH0047 had an important effect on the lung microenvironment inhibiting the growth of lung lesions. ISTH0047 treatment re-educated macrophages in the lung parenchyma to express the tumor-suppressive factor, CD86.

Conclusion

Overall, our data point to TGF-β2 as a therapeutic target and ISTH0047 as a novel anticancer drug to prevent lung metastasis by impacting on the tumor niche, in part, through the induction of CD86 in tumor-associated macrophages.

Link between high-affinity adenosine concentrative nucleoside transporter-2 (CNT2) and energy metabolism in intestinal and liver parenchymal cells

Concentrative nucleoside transporter 2 (CNT2) is a high-affinity adenosine transporter that may play physiological roles beyond nucleoside salvage. Previous reports relate CNT2 function to modulation of purinergic signaling and energy metabolism in intestinal and liver parenchymal cells (Duflot et al., 2004, Mol Cell Biol 24:2710-2719; Aymerich et al., 2006, J Cell Sci 119:1612-1621). In the present study, to further examine the link between CNT2 and energy metabolism, CNT2 protein partners were identified using the bacterial two-hybrid and GST pull-down approaches. The N-terminal segment of CNT2 was used as bait, since proteins lacking this domain display impaired plasma membrane insertion and intracellular retention. Glucose-regulated protein 58 (GRP58) was identified as a potential rCNT2 partner in pull-down experiments. Two-hybrid screening performed against a liver human cDNA library led to the identification of aldolase B as another hCNT2 partner. Aldolase B-RFP and endogenous GRP58 separately co-localized with CNT2 in HeLa cells transfected with YFPrCNT2. CNT2 interaction with GRP58 was validated using co-immunoprecipitation experiments. In HeLa cells, fluorescence resonance energy transfer (FRET) efficiency increased upon fructose addition, consistent with a transient interaction between aldolase B and the transporter. The physiological basis for in vivo interactions was derived from experiments in which GRP58 was inhibited or overexpressed and aldolase B activity stimulated towards glycolysis. GRP58 appeared to be a negative effector of CNT2 function, whereas aldolase B flux modulated CNT2 activity via a mechanism involving acquisition of higher affinity for its substrates. These findings support the theory that CNT2 plays roles other than salvage and establishes links with energy metabolism.

Transport of nucleoside analogs across the plasma membrane: a clue to understanding drug-induced cytotoxicity

Nucleoside analogs are widely used in the treatment of cancer and viral-induced diseases. Efficacy of treatments relies upon a variety of events, including transport across tissue and target barriers, which determine drug pharmacokinetics and target cell bioavailability. To exert their action, nucleosides have to be chemically modified, thus compromising cellular uptake by those routes which are responsible for the uptake of natural nucleosides and nucleobases. In this review we will focus on established knowledge and recent advances in the understanding of nucleoside- and nucleobase-derived drug uptake mechanisms. Basically, these drug uptake processes involve the gene families SLC22, SLC28 and SLC29. These gene families encode Organic Anion Transporter (OAT)/Organic Cation Transporter (OCT), Concentrative Nucleoside Transporter (CNT) and Equilibrative Nucleoside Transporter (ENT) proteins, respectively. The pharmacological profiles of these plasma membrane carriers as well as their basic physiological and regulatory properties, including their tissue and subcellular distribution will be reviewed. This knowledge is crucial for the understanding of nucleoside- and nucleobase-derived drug bioavailability and therapeutic action. Moreover, changes in both transporter expression and/or transporter function (for instance as a consequence of gene variability) might also modulate response to treatment, thereby anticipating a putative diagnostic and predictive added value to the analysis of transporter expression and their corresponding genetic variants.

Bile acids alter the subcellular localization of CNT2 (concentrative nucleoside cotransporter) and increase CNT2-related transport activity in liver parenchymal cells

CNT2 (concentrative nucleoside cotransporter) is a plasma membrane high-affinity Na+-coupled adenosine transporter, also localized in intracellular structures. This transporter protein may play additional roles other than nucleoside salvage, since it has recently been shown to be under purinergic control via K(ATP) channels, by a mechanism that does not seem to involve changes in its subcellular localization. In an attempt to identify the agents that promote CNT2 trafficking, bile acids were found to increase CNT2-related transport activity in a K(ATP) channel-independent manner in both Fao hepatoma and rat liver parenchymal cells. A maximum effect was recorded after treatment with hydrophilic anions such as TCA (taurocholate). However, this effect did not involve changes in the amount of CNT2 protein, it was instead associated with a subcellular redistribution of CNT2, resulting in an accumulation of the transporter at the plasma membrane. This was deduced from subcellular fractionation studies, biotinylation of plasma membrane proteins and subsequent CNT2 detection in streptavidin precipitates and in vivo confocal microscopic analysis of the distribution of a YFP (yellow fluorescent protein)-CNT2 construct. The induction of CNT2 translocation, triggered by TCA, was inhibited by wortmannin, dibutyryl-AMPc, PD98059 and colchicine, thus suggesting the involvement of the PI3K/ERK (phosphoinositide 3-kinase/extracellular-signal related kinase) pathway in microtubule-dependent activation of recombinant CNT2. These are novel effects of bile-acid physiology and provide the first evidence for short-term regulation of CNT2 translocation into and from the plasma membrane.

The concentrative nucleoside transporter family (SLC28): new roles beyond salvage?

The concentrative nucleoside transporter (CNT) family (SLC28) has three members: SLC28A1 (CNT1), SLC28A2 (CNT2) and SLC28A3 (CNT3). The CNT1 and CNT2 transporters are co-expressed in liver parenchymal cells and macrophages, two suitable models in which to study cell cycle progression. Despite initial observations suggesting that these transporter proteins might contribute to nucleoside salvage during proliferation, their subcellular localization and regulatory properties suggest alternative roles in cell physiology. In particular, CNT2 is a suitable candidate for modulation of purinergic responses, since it is under the control of the adenosine 1 receptor. Increasing evidence also suggests a role for CNT2 in energy metabolism, since its activation relies on the opening of ATP-sensitive K+ channels. Animal and cell models genetically modified to alter nucleoside transporter expression levels may help to elucidate the particular roles of CNT proteins in cell physiology.

Equilibrative nucleoside transporter-2 (hENT2) protein expression correlates with ex vivo sensitivity to fludarabine in chronic lymphocytic leukemia (CLL) cells

Fludarabine is considered the treatment of choice for most patients with chronic lymphocytic leukemia (CLL). We have analyzed the role of plasma membrane transporters in nucleoside-derived drug bioavailability and action in CLL cells. Among the known plasma membrane transporters, we have previously observed a significant correlation between fludarabine uptake via ENT carriers and ex vivo sensitivity of CLL cells to fludarabine, although mRNA amounts of the equilibrative nucleoside transporters hENT1 and hENT2 do not show any predictive response to treatment. In this study, using polyclonal monospecific antibodies we have observed a significant correlation between the expression of hENT2 by Western blot and fludarabine uptake via hENT carriers and also with ex vivo sensitivity of CLL cells to fludarabine. These results suggest that the equilibrative nucleoside transporter hENT2 plays a role in fludarabine responsiveness in CLL patients.