Therapeutic harnessing of adaptive immunity via checkpoint inhibition has transformed the treatment of many cancers. Despite unprecedented long-term responses, most patients do not respond to these ...therapies. Immunotherapy non-responders often harbor high levels of circulating myeloid-derived suppressor cells (MDSCs)—an immunosuppressive innate cell population. Through genetic and pharmacological approaches, we uncovered a pathway governing MDSC abundance in multiple cancer types. Therapeutic liver-X nuclear receptor (LXR) agonism reduced MDSC abundance in murine models and in patients treated in a first-in-human dose escalation phase 1 trial. MDSC depletion was associated with activation of cytotoxic T lymphocyte (CTL) responses in mice and patients. The LXR transcriptional target ApoE mediated these effects in mice, where LXR/ApoE activation therapy elicited robust anti-tumor responses and also enhanced T cell activation during various immune-based therapies. We implicate the LXR/ApoE axis in the regulation of innate immune suppression and as a target for enhancing the efficacy of cancer immunotherapy in patients.
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•LXR agonism reduces immunosuppressive MDSC levels in mice and cancer patients•LXR transcriptional target ApoE impairs MDSC survival•LXR-induced MDSC depletion enhances activation of cytotoxic T lymphocytes (CTLs)•CTL activation occurs in mice and patients, enhancing tumor immunotherapy in mice
Therapeutic agonism of the LXR/ApoE axis promotes anti-tumor immunity by targeting immunosuppressive innate immune cells.
Blood vessels support tumours by providing nutrients and oxygen, while also acting as conduits for the dissemination of cancer
. Here we use mouse models of breast and lung cancer to investigate ...whether endothelial cells also have active 'instructive' roles in the dissemination of cancer. We purified genetically tagged endothelial ribosomes and their associated transcripts from highly and poorly metastatic tumours. Deep sequencing revealed that metastatic tumours induced expression of the axon-guidance gene Slit2 in endothelium, establishing differential expression between the endothelial (high Slit2 expression) and tumoural (low Slit2 expression) compartments. Endothelial-derived SLIT2 protein and its receptor ROBO1 promoted the migration of cancer cells towards endothelial cells and intravasation. Deleting endothelial Slit2 suppressed metastatic dissemination in mouse models of breast and lung cancer. Conversely, deletion of tumoural Slit2 enhanced metastatic progression. We identified double-stranded RNA derived from tumour cells as an upstream signal that induces expression of endothelial SLIT2 by acting on the RNA-sensing receptor TLR3. Accordingly, a set of endogenous retroviral element RNAs were upregulated in metastatic cells and detected extracellularly. Thus, cancer cells co-opt innate RNA sensing to induce a chemotactic signalling pathway in endothelium that drives intravasation and metastasis. These findings reveal that endothelial cells have a direct instructive role in driving metastatic dissemination, and demonstrate that a single gene (Slit2) can promote or suppress cancer progression depending on its cellular source.
Clinical outcomes of severe acute respiratory syndrome 2 (SARS-CoV-2) infection are highly heterogeneous, ranging from asymptomatic infection to lethal coronavirus disease 2019 (COVID-19). The ...factors underlying this heterogeneity remain insufficiently understood. Genetic association studies have suggested that genetic variants contribute to the heterogeneity of COVID-19 outcomes, but the underlying potential causal mechanisms are insufficiently understood. Here we show that common variants of the apolipoprotein E (APOE) gene, homozygous in approximately 3% of the world's population
and associated with Alzheimer's disease, atherosclerosis and anti-tumour immunity
, affect COVID-19 outcome in a mouse model that recapitulates increased susceptibility conferred by male sex and advanced age. Mice bearing the APOE2 or APOE4 variant exhibited rapid disease progression and poor survival outcomes relative to mice bearing the most prevalent APOE3 allele. APOE2 and APOE4 mice exhibited increased viral loads as well as suppressed adaptive immune responses early after infection. In vitro assays demonstrated increased infection in the presence of APOE2 and APOE4 relative to APOE3, indicating that differential outcomes are mediated by differential effects of APOE variants on both viral infection and antiviral immunity. Consistent with these in vivo findings in mice, our results also show that APOE genotype is associated with survival in patients infected with SARS-CoV-2 in the UK Biobank (candidate variant analysis, P = 2.6 × 10
). Our findings suggest APOE genotype to partially explain the heterogeneity of COVID-19 outcomes and warrant prospective studies to assess APOE genotyping as a means of identifying patients at high risk for adverse outcomes.
The secreted lipid transporter apolipoprotein E (APOE) plays important roles in atherosclerosis and Alzheimer's disease and has been implicated as a suppressor of melanoma progression. The APOE ...germline genotype predicts human melanoma outcomes, with APOE4 and APOE2 allele carriers exhibiting prolonged and reduced survival, respectively, relative to APOE3 homozygotes. While the APOE4 variant was recently shown to suppress melanoma progression by enhancing antitumor immunity, further work is needed to fully characterize the melanoma cell-intrinsic effects of APOE variants on cancer progression. Using a genetically engineered mouse model, we showed that human germline APOE genetic variants differentially modulate melanoma growth and metastasis in an APOE2>APOE3>APOE4 manner. The low-density lipoprotein receptor-related protein 1 (LRP1) receptor mediated the cell-intrinsic effects of APOE variants on melanoma progression. Protein synthesis was a tumor cell-intrinsic process differentially modulated by APOE variants, with APOE2 promoting translation via LRP1. These findings reveal a gain-of-function role for the APOE2 variant in melanoma progression, which may aid in predicting melanoma patient outcomes and understanding the protective effect of APOE2 in Alzheimer's disease.
APOE germline variants impact melanoma progression through disparate mechanisms, such as the protein synthesis-promoting function of the APOE2 variant, indicating that germline genetic variants are causal contributors to metastatic outcomes.
The tumor microenvironment harbors a variety of different cell types that differentially impact tumor biology. In this issue of Cell Reports Methods, Raffo-Romero et al. standardized and optimized 3D ...tumor organoids to model the interactions between tumor-associated macrophages and tumor cells in vitro.
The tumor microenvironment harbors a variety of different cell types that differentially impact tumor biology. In this issue of Cell Reports Methods, Raffo-Romero et al. standardized and optimized 3D tumor organoids to model the interactions between tumor-associated macrophages and tumor cells in vitro.
Recent reports have revealed myelodysplastic syndromes (MDS) to arise from cancer stem cells phenotypically similar to physiological hematopoietic stem cells. Myelodysplastic hematopoiesis maintains ...a hierarchical organization, but the proportion of several hematopoietic compartments is skewed and multiple surface markers are aberrantly expressed. These aberrant antigen expression patterns hold diagnostic and therapeutic promise. However, eradication of MDS requires targeting of early myelodysplasia propagating stem cells. This warrants an exact assessment of the differentiation stage at which aberrant expression occurs in transformed hematopoiesis. Here, we report results on the prospective and extensive dissection of the hematopoietic hierarchy in 20 patients with either low-risk MDS or MDS with excess blasts and compare it to hematopoiesis in patients with non-malignancy-associated cytopenia or B cell lymphoma without bone marrow infiltration. We found patients with MDS with excess blasts to exhibit characteristic expansions of specific immature progenitor compartments. We also identified the aberrant expression of several markers including ALDH, CLL-1, CD44, and CD47 to be specific features of hematopoiesis in MDS with excess blasts. We show that amongst these, aberrant CLL-1 expression manifested at the early uncommitted hematopoietic stem cell level, suggesting a potential role as a therapeutic target.
Common germline variants of the APOE gene are major risk modifiers of neurodegenerative and atherosclerotic diseases
, but their effect on cancer outcome is poorly defined. Here we report that, in a ...reversal of their effect on Alzheimer's disease, the APOE4 and APOE2 variants confer favorable and poor outcomes in melanoma, respectively. Mice expressing the human APOE4 allele exhibited reduced melanoma progression and metastasis relative to APOE2 mice. APOE4 mice exhibited enhanced anti-tumor immune activation relative to APOE2 mice, and T cell depletion experiments showed that the effect of APOE genotype on melanoma progression was mediated by altered anti-tumor immunity. Consistently, patients with melanoma carrying the APOE4 variant experienced improved survival in comparison to carriers of APOE2. Notably, APOE4 mice also showed improved outcomes under PD1 immune checkpoint blockade relative to APOE2 mice, and patients carrying APOE4 experienced improved anti-PD1 immunotherapy survival after progression on frontline regimens. Finally, enhancing APOE expression via pharmacologic activation of liver X receptors, previously shown to boost anti-tumor immunity
, exhibited therapeutic efficacy in APOE4 mice but not in APOE2 mice. These findings demonstrate that pre-existing hereditary genetics can impact progression and survival outcomes of a future malignancy and warrant prospective investigation of APOE genotype as a biomarker for melanoma outcome and therapeutic response.
Pancreatic ductal adenocarcinoma (PDAC) cells require substantial metabolic rewiring to overcome nutrient limitations and immune surveillance. However, the metabolic pathways necessary for pancreatic ...tumor growth in vivo are poorly understood. To address this, we performed metabolism-focused CRISPR screens in PDAC cells grown in culture or engrafted in immunocompetent mice. While most metabolic gene essentialities are unexpectedly similar under these conditions, a small fraction of metabolic genes are differentially required for tumor progression. Among these, loss of heme synthesis reduces tumor growth due to a limiting role of heme in vivo, an effect independent of tissue origin or immune system. Our screens also identify autophagy as a metabolic requirement for pancreatic tumor immune evasion. Mechanistically, autophagy protects cancer cells from CD8+ T cell killing through TNFα-induced cell death in vitro. Altogether, this resource provides metabolic dependencies arising from microenvironmental limitations and the immune system, nominating potential anti-cancer targets.
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•CRISPR screens identify metabolic genes essential for pancreatic tumor growth•Most metabolic essentialities are similar in cells grown in culture and as tumors•Heme synthesis is limiting due to increased heme degradation in the tumor environment•Autophagy enables cancer cells to evade CD8+ T cell killing
Using in vivo CRISPR screens, Zhu et al. map metabolic genes essential for pancreatic cancer cells to grow in culture and as tumors. While most essentialities are similar under these conditions, genetic screens identify heme synthesis and autophagy as metabolic requirements specific to the tumor environment.
Cancer cells need to acquire specific molecular traits in order to spread to distant organs. In this issue of Developmental Cell, Marsh et al. show that autophagy restricts the outgrowth of breast ...cancer metastases in contrast to its impact on primary tumor progression.
Cancer cells need to acquire specific molecular traits in order to spread to distant organs. In this issue of Developmental Cell, Marsh et al. show that autophagy restricts the outgrowth of breast cancer metastases in contrast to its impact on primary tumor progression.
Metastatic colonization is the primary cause of death from colorectal cancer (CRC). We employed genome-scale in vivo short hairpin RNA (shRNA) screening and validation to identify 26 promoters of CRC ...liver colonization. Among these genes, we identified a cluster that contains multiple targetable genes, including ITPR3, which promoted liver-metastatic colonization and elicited similar downstream gene expression programs. ITPR3 is a caffeine-sensitive inositol 1,4,5-triphosphate (IP3) receptor that releases calcium from the endoplasmic reticulum and enhanced metastatic colonization by inducing expression of RELB, a transcription factor that is associated with non-canonical NF-κB signaling. Genetic, cell biological, pharmacologic, and clinical association studies revealed that ITPR3 and RELB drive CRC colony formation by promoting cell survival upon substratum detachment or hypoxic exposure. RELB was sufficient to drive colonization downstream of ITPR3. Our findings implicate the ITPR3/calcium/RELB axis in CRC metastatic colony formation and uncover multiple clinico-pathologically associated targetable proteins as drivers of CRC metastatic colonization.
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•Loss of ITPR3 in colorectal cancer cells inhibits metastatic liver colonization•RELB acts downstream of ITPR3/calcium to promote colorectal cancer liver metastasis•ITPR3 and RELB regulate survival in response to hypoxia and substratum detachment•Exposure of colorectal cancer cells to ITPR3 inhibitor caffeine reduces liver metastasis
Moy et al. define a clinically relevant pathway that promotes colorectal cancer cell survival and liver metastasis via the type 3 inositol 1,4,5-triphosphate receptor ITPR3, a calcium channel that controls calcium release from the endoplasmic reticulum, and RELB, a transcription factor that is associated with non-canonical NF-κB signaling.
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