Lectin-type oxidized LDL receptor 1 defines population of polymorphonuclear myeloid-derived suppressor cells in cancer patients
ABSTRACT: Polymorphonuclear myeloid-derived suppressor cells (PMN-MDSC) are important regulators of immune responses and promoters of tumor progression in cancer1,2. The heterogeneity of these cells as well as their distinction from neutrophils hampers the progress in understanding of the biology and clinical significance of these cells. PMN-MDSC had a distinct gene signature from neutrophils isolated from the same patients with most prominent changes in genes associated with endoplasmic reticulum (ER) stress response. Surprisingly, low-density lipoprotein (LDL) was one of the most enriched gene regulators and oxidized LDL receptor 1 (OLR1) was one of the most overexpressed genes in PMN-MDSC. Lectin-type oxidized LDL receptor 1 (LOX-1) encoded by OLR1 was expressed in only 0.7% of neutrophils in peripheral blood of healthy donors, whereas 5-15% of neutrophils in cancer patients and 15-50% of neutrophils in tumor tissues were LOX-1+. In contrast to their LOX-1- counterparts, LOX-1+ neutrophils had gene signature, biochemical and functional characteristics of PMN-MDSC. Induction of ER stress in neutrophils from healthy donors up-regulated LOX-1 expression and converted these cells to suppressive PMN-MDSC. Thus, PMN-MDSC have distinct gene signature and LOX-1 can define this population of cells, which may provide new insight to the biology and clinical evaluation of these cells. Examination of LOX1+/LOX1- and PMN/MDSC cells in cancer patient samples
Project description:Polymorphonuclear myeloid-derived suppressor cells (PMN-MDSC) are important regulators of immune responses in cancer and have been directly implicated in promotion of tumor progression. However, the heterogeneity of these cells and lack of distinct markers hampers the progress in understanding of the biology and clinical importance of these cells. Using partial enrichment of PMN-MDSC with gradient centrifugation we determined that low density PMN-MDSC and high density neutrophils from the same cancer patients had a distinct gene profile. Most prominent changes were observed in the expression of genes associated with endoplasmic reticulum (ER) stress. Surprisingly, low-density lipoprotein (LDL) was one of the most increased regulators and its receptor oxidized LDL receptor 1 OLR1 was one of the most overexpressed genes in PMN-MDSC. Lectin-type oxidized LDL receptor 1 (LOX-1) encoded by OLR1 was practically undetectable in neutrophils in peripheral blood of healthy donors, whereas 5-15% of total neutrophils in cancer patients and 15-50% of neutrophils in tumor tissues were LOX-1+. In contrast to their LOX-1- counterparts, LOX-1+ neutrophils had gene signature, potent immune suppressive activity, up-regulation of ER stress, and other biochemical characteristics of PMN-MDSC. Moreover, induction of ER stress in neutrophils from healthy donors up-regulated LOX-1 expression and converted these cells to suppressive PMN-MDSC. Thus, we identified a specific marker of human PMN-MDSC associated with ER stress and lipid metabolism, which provides new insight to the biology and potential therapeutic targeting of these cells.
Project description:The OLR1 gene encodes the oxidized low-density lipoprotein receptor (LOX-1), which is responsible for the cellular uptake of oxidized LDL (Ox-LDL), foam cell formation in atheroma plaques and atherosclerotic plaque rupture. Alternative splicing (AS) of OLR1 exon 5 generates two protein isoforms with antagonistic functions in Ox-LDL uptake. Previous work identified six single nucleotide polymorphisms (SNPs) in linkage disequilibrium that influence the inclusion levels of OLR1 exon 5 and correlate with the risk of cardiovascular disease. Here we use minigenes to recapitulate the effects of two allelic series (Low- and High-Risk) on OLR1 AS and identify one SNP in intron 4 (rs3736234) as the main contributor to the differences in exon 5 inclusion, while the other SNPs in the allelic series attenuate the drastic effects of this key SNP. Bioinformatic, proteomic, mutational and functional high-throughput analyses allowed us to define regulatory sequence motifs and identify SR protein family members (SRSF1, SRSF2) and HMGA1 as factors involved in the regulation of OLR1 AS. Our results suggest that antagonism between SRSF1 and SRSF2/HMGA1, and differential recognition of their regulatory motifs depending on the identity of the rs3736234 polymorphism, influence OLR1 exon 5 inclusion and the efficiency of Ox-LDL uptake, with potential implications for atherosclerosis and coronary disease.
Project description:Polymorphonuclear myeloid derived suppressor cells (PMN-MDSC) are pathologically activated neutrophils that accumulate in cancer and many other pathologic conditions. PMN-MDSC are critically important for the regulation of immune responses in cancer, promotion of tumor progression, and metastases. Despite the recent advances in understanding of the PMN-MDSC biology, the mechanisms responsible for pathological activation of neutrophils are not well defined, which limit selective targeting of PMN-MDSC. Here, we report that mouse and human PMN-MDSC exclusively up-regulate fatty acid transporter protein 2 (FATP2). Over-expression of FATP2 in PMN-MDSC was controlled by GM-CSF, through the activation of STAT5 transcription factor. Genetic ablation of FATP2 abrogated the suppressive activity of PMN-MDSC in spleens and tumors. FATP2 in neutrophils promoted accumulation of oxidized lipids. However, the main mechanism of FATP2 mediated suppressive activity of PMN-MDSC involved uptake of arachidonic acid and synthesis of prostaglandin E2. The selective pharmacological inhibition of FATP2 abrogated activity of PMN-MSC and substantially delayed tumor progression. In combination with check-point inhibitors it blocked tumor progression in mice. Thus, FATP2 mediates acquisition of immune suppressive activity by PMN-MDSC and represents a new target to inhibit the functions of PMN-MDSC and improve the effect of immunotherapy of cancer. Overall design: RNA-seq for WT and FATP2 KO PMN-MDSC cells
Project description:DCs are a critical component of immune responses in cancer primarily due to their ability to cross-present tumor-associated antigens. Cross-presentation by DCs in cancer is impaired, which may represent one of the obstacles for the success of cancer immunotherapies. Here, we report that polymorphonuclear myeloid-derived suppressor cells (PMN-MDSC) blocked cross-presentation by DCs without affecting direct presentation of antigens by these cells. This effect did not require direct cell-cell contact and was associated with transfer of lipids. Neutrophils (PMN) and PMN-MDSC transferred lipid to DCs equally well; however, PMN did not affect DC cross-presentation. PMN-MDSC generate oxidatively truncated lipids previously shown to be involved in impaired cross-presentation by DCs. Accumulation of oxidized lipids in PMN-MDSC was dependent on myeloperoxidase (MPO). MPO-deficient PMN-MDSC did not affect cross-presentation by DCs. Cross-presentation of tumor-associated antigens in vivo by DCs was improved in MDSC-depleted or tumor-bearing MPO-KO mice. Pharmacological inhibition of MPO in combination with checkpoint blockade reduced tumor progression in different tumor models. These data suggest MPO-driven lipid peroxidation in PMN-MDSC as a possible non-cell autonomous mechanism of inhibition of antigen cross-presentation by DCs and propose MPO as potential therapeutic target to enhance the efficacy of current immunotherapies for patients with cancer.
Project description:Objective:Metabolic syndrome (MetS) is associated with abnormal lipid profile and high cardiovascular risk. There is an increased prevalence of coronary artery disease and Type 2 Diabetes Mellitus in India. Oxidized Low Density Lipoprotein Receptor 1(OLR1), a cell surface endocytosis receptor recognize, internalize and degrade oxidized LDL (oxLDL) in vascular endothelium and plays a role in the pathogenesis of atherosclerosis. The aim was to explore the association of OLR1 gene polymorphism and measure the serum levels of ox-LDL in patients with MetS in Indian population. Materials and Methods:Forty cases fulfilling the IDF diagnostic criteria for MetS and 40 healthy controls having similar age and sex ratio were genotyped for OLR1 gene (SNP: IVS4-73C>T , rs3736234) by RFLP-PCR. Serum ox-LDL was estimated by ELISA.Their BP, BMI and waist circumference were measured. Fasting Plasma glucose, Serum Triglyceride and HDL-C were measured. Results:Serum oxLDL was significantly higher in MetS cases as compared to controls (p < 0.0001). Odds ratio of T allele of above OLR1 SNP among subjects with MetS was 14.79 (95%CI: 1.80-121.2, p < 0.05). But no association was found between the SNP and serum ox-LDL levels. People having TT allele had higher BMI compared to those having CC allele. Conclusion:Ox LDL, being more atherogenic might contribute in the pathogenesis of MetS. The intronic SNP: IVS4-73 C>T of OLR1 gene increases the risk of developing MetS by a yet unknown mechanism that is independent of rise in ox-LDL. This OLR1 SNP probably influences BMI.
Project description:The lectin-like oxidized LDL receptor LOX-1 (encoded by OLR1) is believed to play a key role in atherogenesis and some reports suggest an association of OLR1 polymorphisms with myocardial infarction (MI). We tested whether single nucleotide polymorphisms (SNPs) in OLR1 are associated with clinically significant CAD in the Atherosclerotic Disease, VAscular FuNction, & Geneti C Epidemiology (ADVANCE) study.ADVANCE is a population-based case-control study of subjects receiving care within Kaiser Permanente of Northern California including a subset of participants of the Coronary Artery Risk Development in Young Adults (CARDIA) study. We first resequenced the promoter, exonic, and splice site regions of OLR1 and then genotyped four single nucleotide polymorphisms (SNPs), including a non-synonymous SNP (rs11053646, Lys167Asn) as well as an intronic SNP (rs3736232) previously associated with CAD.In 1,809 cases with clinical CAD and 1,734 controls, the minor allele of the coding SNP was nominally associated with a lower odds ratio (OR) of CAD across all ethnic groups studied (minimally adjusted OR 0.8, P = 0.007; fully adjusted OR 0.8, P = 0.01). The intronic SNP was nominally associated with an increased risk of CAD (minimally adjusted OR 1.12, p = 0.03; fully adjusted OR 1.13, P = 0.03). However, these associations were not replicated in over 13,200 individuals (including 1,470 cases) in the Atherosclerosis Risk in Communities (ARIC) study.Our results do not support the presence of an association between selected common SNPs in OLR1 and the risk of clinical CAD.
Project description:Inhibition of immune checkpoint proteins like programmed death 1 (PD-1) is a promising therapeutic approach for several cancers, including non-small cell lung cancer (NSCLC). Although PD-1 ligand (PD-L1) expression is used to predict anti-PD-1 therapy responses in NSCLC, its accuracy is relatively less. Therefore, we sought to identify a more accurate predictive blood biomarker for evaluating anti-PD-1 response. We evaluated the frequencies of T cells, B cells, natural killer (NK) cells, polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs), mononuclear myeloid-derived suppressor cells (M-MDSCs), and Lox-1+ PMN-MDSCs in peripheral blood samples of 62 NSCLC patients before and after nivolumab treatment. Correlation of immune-cell population frequencies with treatment response, progression-free survival, and overall survival was also determined. After the first treatment, the median NK cell percentage was significantly higher in responders than in non-responders, while the median Lox-1+ PMN-MDSC percentage showed the opposite trend. NK cell frequencies significantly increased in responders but not in non-responders. NK cell frequency inversely correlated with that of Lox-1+ PMN-MDSCs after the first treatment cycle. The NK cell-to-Lox-1+ PMN-MDSC ratio (NMR) was significantly higher in responders than in non-responders. Patients with NMRs ? 5.75 after the first cycle had significantly higher objective response rates and longer progression-free and overall survival than those with NMRs <5.75. NMR shows promise as an early predictor of response to further anti-PD-1 therapy.
Project description:Alternative splicing (AS) is a process in which precursor messenger RNA (pre-mRNA) splicing sites are differentially selected to diversify the protein isoform population. Changes in AS patterns have an essential role in normal development, differentiation and response to physiological stimuli. It is documented that AS can generate both "risk" and "protective" splice variants that can contribute to the pathogenesis of several diseases including atherosclerosis. The main endothelial receptor for oxidized low-density lipoprotein (ox-LDLs) is LOX-1 receptor protein encoded by the OLR1 gene. When OLR1 undergoes AS events, it generates three variants: OLR1, OLR1D4 and LOXIN. The latter lacks exon 5 and two-thirds of the functional domain. Literature data demonstrate a protective role of LOXIN in pathologies correlated with LOX-1 overexpression such as atherosclerosis and tumors. In this review, we summarize recent developments in understanding of OLR1 AS while also highlighting data warranting further investigation of this process as a novel therapeutic target.
Project description:The up-regulation of lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1), encoded by the OLR1 gene, plays a fundamental role in the pathogenesis of atherosclerosis. Moreover, OLR1 polymorphisms were associated with increased susceptibility to acute myocardial infarction (AMI) and coronary artery diseases (CAD). In these pathologies, the identification of therapeutic approaches that can inhibit or reduce LOX-1 overexpression is crucial. Predictive analysis showed a putative hsa-miR-24 binding site in the 3'UTR of OLR1, 'naturally' mutated by the presence of the rs1050286 single nucleotide polymorphism (SNP). Luciferase assays revealed that miR-24 targets OLR1 3'UTR-G, but not 3'UTR-A (P < 0.0005). The functional relevance of miR-24 in regulating the expression of OLR1 was established by overexpressing miR-24 in human cell lines heterozygous (A/G, HeLa) and homozygous (A/A, HepG2) for rs1050286 SNP. Accordingly, HeLa (A/G), but not HepG2 (A/A), showed a significant down-regulation of OLR1 both at RNA and protein level. Our results indicate that rs1050286 SNP significantly affects miR-24 binding affinity to the 3'UTR of OLR1, causing a more efficient post-transcriptional gene repression in the presence of the G allele. On this basis, we considered that OLR1 rs1050286 SNP may contribute to modify OLR1 susceptibility to AMI and CAD, so ORL1 SNPs screening could help to stratify patients risk.
Project description:To explore the impact of oxidized low density lipoprotein receptor 1 (Olr1 aka LOX-1) gene on stroke, we newly generate a LOX-1 deficient strain of the genetic background of stroke-prone spontaneously hypertensive rat (SHRSP). We explored circulatory miRNAs as diagnostic biomarkers for cerebral ischemic injury by microarray analysis in related rat strains.