Levels Of Myeloid-derived Suppressor Cells Research Articles

Early systemic immune biomarkers predict bone regeneration after trauma

Severe traumatic injuries are a widespread and challenging clinical problem, and yet the factors that drive successful healing and restoration of function are still not well understood. One recently identified risk factor for poor healing outcomes is a dysregulated immune response following injury. In a preclinical model of orthopedic trauma, we demonstrate that distinct systemic immune profiles are correlated with impaired bone regeneration. Most notably, elevated blood levels of myeloid-derived suppressor cells (MDSCs) and the immunosuppressive cytokine interleukin-10 (IL-10) are negatively correlated with functional bone regeneration as early as 1 wk posttreatment. Nonlinear multivariate regression also implicated these two factors as the most influential in predictive computational models. These results support a significant relationship between early systemic immune responses to trauma and subsequent local bone regeneration and indicate that elevated circulating levels of MDSCs and IL-10 may be predictive of poor functional healing outcomes and represent novel targets for immunotherapeutic intervention.

Expansion of Monocytic Myeloid-Derived Suppressor Cells in Patients Under Hemodialysis Might Lead to Cardiovascular and Cerebrovascular Events

BackgroundThe specific mechanism of cardiovascular and cerebrovascular vasculopathy in the context of end-stage renal disease has not been elucidated. In the present study, we investigated the clinical impact of myeloid-derived suppressor cells (MDSCs) on hemodialysis patients and their mechanism of action.MethodsMDSCs were tested among 104 patients undergoing hemodialysis and their association with overall survival (OS) and cardiovascular and cerebrovascular events was determined.ResultsHemodialysis patients presented a significantly higher level of monocytic MDSCs (M-MDSCs) compared to healthy controls. M-MDSC were tested 3 months after first testing among 103 hemodialysis patients, with one patient not retested due to early death. The repeated results of M-MDSC levels were consistent with the initial results. Patients with persistent high level of M-MDSCs presented decreased OS, as well as increased stroke and acute heart failure events. As illustrated by multivariate Cox regression, M-MDSC was an independent predictor for OS and stroke events of hemodialysis patients. T cell proliferations were significantly abrogated by hemodialysis-related M-MDSCs in a dose-dependent manner. Besides, M-MDSCs presented higher levels of CXCR4 and VLA-4 compared to monocytes, which indicated their enhanced capability to be recruited to atherosclerotic lesions. The expression of arginase I and activity of arginase was also significantly raised in hemodialysis-related M-MDSCs. Human coronary arterial endothelial cells (HCAECs) presented increased capability to migration by coculture with M-MDSCs, compared with monocyte group. Arginase inhibitor and L-arginine abrogated the immune suppressive function and induction of HCAECs migration of hemodialysis related M-MDSC. Plasma IFN-γ, TNF-α and IL-6 were elevated in hemodialysis patients compared with healthy control. M-MDSC level was positively related to IL-6 level among hemodialysis patients. The plasma of hemodialysis patients induced M-MDSCs significantly compared with plasma from health donors. Besides, IL-6 neutralizing antibody significantly abrogated the induction. Neutralizing antibody of IFN-γ and TNF-α partially decreased the generation of arginase of the induced M-MDSC.ConclusionsM-MDSCs were elevated in ESRD patients under hemodialysis, and they exhibited a strong association with the risk of cardiovascular and cerebrovascular diseases. Hemodialysis related M-MDSC presented enhanced recruitment to atherosclerotic lesions, promoted the migration of endothelial cells through exhaustion of local L-arginine.

Role of circulating myeloid-derived suppressor cells in pathogenesis of immune thrombocytopenia in children and adolescents

Context Regulatory T cells have an immunosuppressive function on T-cell activation. They are involved in pathophysiology and treatment of immune thrombocytopenia (ITP). Circulating myeloid-derived suppressor cells (MDSCs) are involved in immune dysregulation in ITP. Aim To determine the mean level of MDSCs in acute, persistent, and chronic ITP and its effect on treatment modalities and prognosis. Patients and methods A total of 41 patients with ITP were recruited from the pediatric hematology clinic of Ain Shams University. They were classified into acute, persistent, and chronic and were compared with 20 age-matched and sex-matched healthy controls. All patients were subjected to history taking with emphasis on age of presentation, disease duration, and treatment modalities, as well as thorough clinical examination. Mean values of C-reactive protein, alanine aminotransferase, and serum creatinine were collected from the patients’ files. All study participants underwent complete blood count (Coulter) and MDSCs by flow cytometry. Secondary thrombocytopenia was excluded. Results Acute ITP was detected in 29%, 24% had persistent, and 46% had chronic ITP. Their age ranged from 1 to 16 years at the study entry, and 51.2% were male. Active disease was found in 58.5%, whereas 41.4% in remission. No treatment was offered to 53%, whereas 24% of patients were on steroids. MDSCs decreased significantly in patients with ITP compared with the control group (P<0.001), whereas there was no significant difference among the patient groups regarding MDSCs level (P=0.325) or with different treatment modalities. Conclusion Reduced numbers of MDSCs play a role in pathogenesis of ITP. Yet, MDSCs did not differ according to disease duration or treatment modalities.

Myeloid-derived suppressor cells level and MUC1 expression in de novo acute myeloid leukemia

AbstractBackgroundAcute myeloid leukemia (AML) is the most common acute leukemia occurring in adults. It is an aggressive myeloid neoplasm with maturation arrest of myelopoiesis, leading to an accumulation of myeloblasts in the bone marrow and peripheral blood.ObjectiveTo evaluate alterations in myeloid-derived suppressor cells level and MUC1 gene expression in patients with de novo acute myeloid leukemia concerning disease characteristics and response to induction chemotherapy.Patients and methodsThe study was performed on 50 AML patients and 50 healthy controls. Detection of myeloid-derived suppressor cells (MDSCs) in peripheral blood was performed by mononuclear separation and flow cytometry. MUC1 gene expression was performed by RNA extraction, reverse transcription, and real-time PCR at Hematology Department Medical Research Institute, Alexandria University.ResultsWe have demonstrated that AML patients had both increased presence of MDSCs in peripheral blood as well as MUC1 overexpression in comparison to normal controls. MDSCs showed a significant correlation regarding response to induction chemotherapy on day 28. While MDSCs and not MUC1 are associated with inferior response to induction chemotherapy on day 28.ConclusionThe current data suggested that AML patients exhibit an increased presence of MDSCs as well as MUC1 gene overexpression in comparison with normal controls. While MDSCs showed a significant correlation regarding response to induction chemotherapy on day 28, MDSCs and not MUC1 are associated with inferior response to induction chemotherapy on the same day.

RNA-Seq Analysis of Colorectal Tumor-Infiltrating Myeloid-Derived Suppressor Cell Subsets Revealed Gene Signatures of Poor Prognosis.

Elevated levels of myeloid-derived suppressor cells (MDSCs), including polymorphonuclear MDSCs (PMN-MDSCs) and immature MDSCs (I-MDSCs), are usually associated with disease progression in cancer patients, including colorectal cancer (CRC). However, biological mechanisms and molecular pathways regulated by MDSC subpopulations in the CRC tumor microenvironment (TME) have not been fully investigated. In this study, we performed transcriptomic analysis of tumor-infiltrating I-MDSCs and PMN-MDSCs isolated from tumor tissues of six CRC patients, compared to antigen-presenting cells (APCs). We also compared the transcriptomic profiles of tumor-infiltrating PMN-MDSCs to I-MDSCs. Our results showed different molecular pathways regulated by each MDSC subset, potentially reflecting their phenotypical/molecular/functional characteristics in the CRC TME. Moreover, we identified gene signatures in PMN-MDSC and I-MDSC of poor overall survival (OS) and disease-free survival (DFS) using the Cancer Genome Atlas (TCGA) dataset from patients with colon adenocarcinoma (COAD). However, functional studies are required to validate these findings.

DDRE-10. IMMUNE PROFILES ASSOCIATE WITH OUTCOMES IN HLA-A*02:01+, H3.3K27M+ PATIENTS WITH DIFFUSE MIDLINE GLIOMAS TREATED WITH H3.3K27M PEPTIDE VACCINE COMBINED WITH POLY-ICLC: A PNOC REPORT

Abstract BACKGROUND Patients with diffuse midline gliomas (DMG), including diffuse intrinsic pontine glioma (DIPG), have dismal outcomes. We previously described the H3.3K27M mutation as a shared neoantigen in HLA-A*02.01+ H3.3K27M+ DMGs. Within the Pacific Pediatric Neuro-Oncology Consortium, we assessed the safety and efficacy of an H3.3K27M-targeted peptide vaccine. PATIENTS AND METHODS Newly diagnosed patients aged 3–21 years with positive HLA-A*02.01+ and H3.3K27M+ status were enrolled into two strata after completion of radiation therapy: Stratum A for DIPG (n=19); Stratum B for non-pontine DMG (n=10). Vaccine was administered in combination with poly-ICLC every three weeks for eight cycles, followed by once every six weeks. Immunological responses were assessed in peripheral blood mononuclear cells using mass cytometry. RESULTS 19 patients enrolled in Stratum A (median age=11 years) and 10 in Stratum B (median age=13 years). There were no grade 4 treatment-related adverse events (TRAE). Injection site reaction was the most commonly reported TRAE. Overall survival (OS) at 12 months was 40% (95% CI, 22% to 73%) for Stratum A and 39% (95% CI, 16% to 93%) for Stratum B. The median OS was 16.1 months in patients exhibiting an expansion of H3.3K27M-reactive CD8+ T-cells compared to 9.8 months for their counterparts (p=0.05). DIPG patients with below-median baseline levels of myeloid-derived suppressor cells had prolonged OS compared to their counterparts (p< 0.1). Immediate pre-treatment dexamethasone administration inversely associated with H3.3K27M-reactive CD8+ T-cell responses. However, neither tumor size or bulk CD8+ T-cell status was significantly associated with OS. CONCLUSION Administration of the H3.3K27M-specific vaccine is well tolerated. Patients with H3.3K27M-specific CD8+ immunological responses demonstrated prolonged OS compared to non-responders.

Role of Circulating Myeloid-Derived Suppressor Cell (MDSC) in Hodgkin Lymphoma (HL) Progression: Updated Prospective Study

Introduction.Patients with HL normally undergo a risk-adapted treatment based on PET scans. Regardless of HL treatment high efficiency, (80-90% remission), the search of new prognostic markers has been a continued process in recent years. This is related to the disease recurrence in 25-35% of patients in the first 5 years. The studies show that MDSC expands dramatically with tumor growth and causes a tumor immunosuppressed environment. The aim of this study is to investigate the number of MDSC in HL patients' peripheral blood and its correlation with clinical variables when the diagnosis and outcome first set. Methods .43 primary HL patients, (median age: 30, range: 19-78 years; male: 18, female: 25), were included in the study since April, 2018. 58.2% and 41.8% of patients have been diagnosed with early and advanced stages of HL, respectively, and received the ABVD or BEACOPP (14/esc) as a 1st-line treatment regimen. Peripheral blood mononuclear cells (PBMC) were isolated by ficoll density gradient centrifugation treatment, after 2-3 chemotherapy cycles (interim), and at the end of treatment (EOT). We assessed the E-MDSC count (CD33+CD11b+CD14-HLA-DR-) using the anti-human antibodies purchased from Beckman Coulter (Brea, CA, USA). We have also used a routine protocol of metabolic PET assessed according to Deauville criteria of response. Results.83.7% of patients achieved remission (CR/PR) during the follow-up period (median timeline: 18.9 months). We recorded a disease progression in 5 (11.6%) patients during and after the 1st line therapy, (time to relapse - 8 months). In addition, those patients had a high level of MDSC before treatment, which also remained high after interim and EOT-PET. Median of EFS has not been reached and we continue monitoring all patients. The HL patients who achieved remission had an increased E-MDSC percent (median 12.5%) compared to the age and gender control group, (median 2.03%), and the non-responders' one (median 20%). The number of NK-T (CD3+CD16+CD56+) cells increased by 15 % after EOT compared to pretreatment number, 9.2%, p=0.05. PBMC Evaluation at baseline.The E-MSDC count increases significantly with age: 3.1% vs 12.9% in HL patients under 25 years of age vs over 40, respectively p=0.014. Pretreatment MDSC levels were potentially associated with the disease stage: early stages (1A-2A and 2B) vs advanced stages (12% vs 3.9% vs 15%, respectively p=0.07). Our PET imaging tentatively correlated to the above levels. With that, patients with PET 5DS had a higher number of E-MDSC compared to a healthy control group, while the count is reduced in responders during and after treatment (p=0.06). Theoretically, this means that immunosuppression would be reduced and the antitumor immune response of the body would improve. PBMC Evaluation at interim response assessment.At this step, the age was also confirmed as an independent predicting factor in patients under 25 vs > 40, according to the MDSC level (6% vs 11.5%, respectively p=0.008). The level of E-MDSC was higher in patients who failed to achieve CR/PR (p=0.08). PBMC Evaluation at the EOT:90.6% (39/43) and 9.4% (4/43) of patients had a PET-negative and PET-positivestatus at the EOT, respectively (p < 0.05). We found a strong correlation between the EOT-PET and E-MDSC level. With this, patients with EOT-PET-ve had a lower E-MDSC expression vs EOT-PET+ve (12% vs 42% respectively, p=0.0007), which may potentially become a prognostic factor of response prediction. IPS is an important independent prognostic factor positively correlated to the MDSC count at EOT. In our study, patients in the high-risk group (3-4 IPS) had a significantly higher level of MDSC number than the low-risk group (1-2 IPS) and are more likely not to achieve a positive response to treatment (25% vs 18%, respectively p=0.02). Conclusion.The obtained results suggest that the higher level of MDSC number is associated with unfavorable prognosis of HL, reduce response rate. The challenge of strictly prognostic factor application leads to the research of biomarkers in the HL field. The discovery of new prognostic factors will improve an individualized approach to patient treatment and decrease the disease relapse risk. Disclosures No relevant conflicts of interest to declare.

Explicating the Pivotal Pathogenic, Diagnostic, and Therapeutic Biomarker Potentials of Myeloid-Derived Suppressor Cells in Glioblastoma.

Glioblastoma (GBM) is a malignant and aggressive central nervous tumor that originates from astrocytes. These pathogenic astrocytes divide rapidly and are sustained by enormous network of blood vessels via which they receive requisite nutrients. It well proven that GBM microenvironment is extremely infiltrated by myeloid-derived suppressor cells (MDSCs). MDSCs are a heterogeneous cluster of immature myeloid progenitors. They are key mediates in immune suppression as well as sustenance glioma growth, invasion, vascularization, and upsurge of regulatory T cells via different molecules. MDSCs are often elevated in the peripheral blood of patients with GBM. MDSCs in the peripheral blood as well as those infiltrating the GBM microenvironment correlated with poor prognosis. Also, an upsurge in circulating MDSCs in the peripheral blood of patients with GBM was observed compared to benign and grade I/II glioma patients. GBM patients with good prognosis presented with reduced MDSCs as well as augmented dendritic cells. Almost all chemotherapeutic medication for GBM has shown no obvious improvement in overall survival in patients. Nevertheless, low-dose chemotherapies were capable of suppressing the levels of MDSCs in GBM as well as multiple tumor models with metastatic to the brain. Thus, MDSCs are potential diagnostic as well as therapeutic biomarkers for GBM patients.

Development of systemic immune dysregulation in a rat trauma model of biomaterial-associated infection

Orthopedic biomaterial-associated infections remain a major clinical challenge, with Staphylococcus aureus being the most common pathogen. S. aureus biofilm formation enhances immune evasion and antibiotic resistance, resulting in a local, indolent infection that can persist long-term without symptoms before eventual hardware failure, bone non-union, or sepsis. Immune modulation is an emerging strategy to combat host immune evasion by S. aureus. However, most immune modulation strategies are focused on local immune responses at the site of infection, with little emphasis on understanding the infection-induced and orthopedic-related systemic immune responses of the host, and their role in local infection clearance and tissue regeneration. This study utilized a rat bone defect model to investigate how implant-associated infection affects the systemic immune response. Long-term systemic immune dysregulation was observed with a significant systemic decrease in T cells and a concomitant increase in immunosuppressive myeloid-derived suppressor cells (MDSCs) compared to non-infected controls. Further, the control group exhibited a regulated and coordinated systemic cytokine response, which was absent in the infection group. Multivariate analysis revealed high levels of MDSCs to be most correlated with the infection group, while high levels of T cells were most correlated with the control group. Locally, the infection group had attenuated macrophage infiltration and increased levels of MDSCs in the local soft tissue compared to non-infected controls. These data reveal the widespread impacts of an orthopedic infection on both the local and the systemic immune responses, uncovering promising targets for diagnostics and immunotherapies that could optimize treatment strategies and ultimately improve patient outcomes.

The association between monocytic myeloid-derived suppressor cells levels and the anti-tumor efficacy of anti-PD-1 therapy in NSCLC patients.

Monocytic myeloid-derived suppressor cells (M-MDSCs), granulocytic MDSC (G-MDSCs) and regulatory T cells (Tregs) inhibit adaptive anti-tumor immunity and undermine the efficacy of anti-PD-1 therapy. However, the impact of anti-PD-1 treatment on these immunosuppressive cells has not been clearly defined in non-small cell lung cancer (NSCLC). In this retrospective study, 27 advanced NSCLC patients were divided into partial response (PR), stable disease (SD), and progressive disease (PD) groups. The impact of anti-PD-1 therapy on circulating Tregs, G-MDSCs, and M-MDSCs was assessed by flow cytometer. Here, we found that anti-PD-1 treatment boosted circulating Tregs levels, which presented the most remarkable augment during the first two therapeutic cycles, in NSCLC patients. In contrast, anti-PD-1 therapy did not overall change G-MDSCs and M-MDSCs levels. However, the PR group had a higher baseline level of M-MDSCs, which exhibited a significant decrease after the first cycle of anti-PD-1 treatment. Besides, M-MDSCs levels in the PR group were maintained at a low level in the following therapeutic cycles. Consistently, Tregs levels robustly increased in the syngeneic tumor model after anti-mouse PD-1 Ab treatment. Accordingly, M-MDSCs neutralization by anti-mouse ly6c Ab enhanced the anti-tumor efficacy of anti-PD-1 therapy in mice. Finally, the decreased M-MDSCs levels were associated with the enhanced effector CD8+ T cells expansion in the PR group and mice. In conclusion, anti-PD-1 therapy upregulates Tregs levels in NSCLC patients, and the M-MDSC levels are associated with the anti-tumor efficacy of anti-PD-1 treatment. Neutralization of M-MDSCs may be a promising option to augment anti-PD-1 therapy efficacy in NSCLC.

THE FEATURE OF MDSCS IN THE LONG-TERM STABLE KIDNEY TRANSPLANT RECIPIENTS AFTER DIFFERENT IMMUNOSUPPRESSION THERAPY

Objective: Myeloid-derived suppressor cells (MDSCs) play an important role in immune tolerance. The aim of this study is to investigate different feature of MDSCs in the long-term survival with kidney transplant recipients. Methods: From January 1989 to November 2008, a total number of 35 Recipients operated in kidney transplantation department of the first affiliated hospital of Xi’an Jiaotong university, were selected. They all had stable kidney function now. Recipients were divided into 4 Four three groups: Aza +Pred (n=5; Tacrolimus inhibitors group (FK506 + MMF + Pred) (n=10; Cyclosporine inhibitors group (CsA + MMF + Pred) (n=10); rapamycin group (RAPA + MMF + Pred) (n=10). The expression of MDSCs in peripheral blood was determined by flow cytometry. The expression of serum HLA-G5 and sCD30 was detected by ELLISA. MDSCs of mice were also induced in vitro, which were also treated with different immunosuppression as above. Results: The percentage of MDSCs was significantly higher in calcineurin inhibitors group than rapamycin inhibitors group. The level of MDSCs between Cyclosporine group and tacrolimus group was no significant difference. Rapamycin significantly reduces the immunosuppressive function of MDSCs on T cells compared with CNI group and reduces the number of MDSCs induced in vitro. No significant difference was observed between Cyclosporine group and tacrolimus group. Conclusions: 1. Rapamycin inhibits the differentiation and function of MDSCs in vitro and in vivo, which maybe bad for immune tolerance. When select rapamycin as immunosuppression, should be careful in Long-term survival with kidney transplant recipients. 2. MDSCs, HLA-G5, CD30 may act an effective method to evaluate immune status of kidney recipients.

Abstract 4481: Effect of immune checkpoint blockade on myeloid derived suppressor cell populations in patients with melanoma

Abstract Introduction: Myeloid derived suppressor cells (MDSC) are a subset of immature myeloid cells that inhibit innate anti-tumor immunity and promote an immunosuppressive tumor microenvironment. MDSC quantity has been correlated with tumor burden and survival in cancer patients. These cells have the potential to contribute to immune therapy resistance. The purpose of this study was to elucidate the ongoing changes to MDSC populations in patients with advanced melanoma as they receive immune checkpoint therapy. Methods: Patients with melanoma (n=125) were consented to participate in an IRB-approved prospective clinical registry (OSU-13114), and provided blood samples. Samples were drawn at the time of initiation of immune checkpoint therapy (cycle 1), and prior to the beginning of cycles 2 and 3. Samples were then processed using Ficoll and analyzed for MDSC (CD33+/CD11b+/HLA-DRlo/−) and MDSC subsets, monocyte (CD14+, M-MDSC) and granulocytic (CD15+, PMN-MDSC) via flow cytometry. Patient demographics were compiled into a comprehensive database and correlated to the flow cytometry data. Statistical analysis was performed using unpaired and paired t-tests across and within patient cohorts. Results: Total MDSC percentages increased following initiation of immune checkpoint blockade (10 to 25%, p<0.0001). MDSC levels in patients who had complete or partial response began to taper (10% to 26% to 25%), whereas MDSC levels in those who had progressive disease on immunotherapy continued to increase (11% to 16% to 19%). PMN-MDSC significantly decreased after immunotherapy (19% to 10%, p=0.0423). Specifically, patients who received Pembrolizumab had a significant decrease in PMN-MDSC proportion (11% to 2%, p=0.04). A decrease in PMN-MDSC proportion was also noted with Nivolumab (21% to 16%, p=0.097). Patients who had received immune therapy prior to this trial had less PMN-MDSC at baseline (21% vs 12%, p=0.09), and significantly less PMN-MDSC following immune checkpoint blockade (14% vs 2%, p=0.009). Conclusions: MDSC levels initially increase following immune checkpoint blockade, but stabilize in responders and continue to rise in non-responders. The proportion of PMN-MDSC decreases with immune checkpoint blockade, most significantly seen with pembrolizumab. Patients who have been previously treated with immune therapy have a more significant decrease in PMN-MDSC. Citation Format: Steven Hao Sun, Brooke Benner, Himanshu Savardekar, Mallory DiVincenzo, David Abood, Andrew Stiff, Megan Duggan, Erin Nagle, John H. Howard, Manisha H. Shah, Kari Kendra, William E. Carson. Effect of immune checkpoint blockade on myeloid derived suppressor cell populations in patients with melanoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4481.

Abstract LB-133: Correlative analysis of pharmacokinetics and pharmacodynamics of RGX-104, a first-in-class Liver-X-Receptor (LXR) agonist, and clinical outcomes in patients with advanced solid tumors

Abstract RGX-104, a first-in-class small-molecule LXR agonist modulates innate immunity and cancer progression via transcriptional activation of ApoE. ApoE protein suppresses tumor cell invasion and angiogenesis, and also depletes circulating and tumoral myeloid derived suppressor cells (MDSC), leading to T cell activation.A multivariate approach was used to address pharmacokinetic (PK) and pharmacodynamic relationships of RGX-104 in a phase 1 dose escalation study in patients with relapsed/refractory solid tumors. The study entailed multiple escalation arms with RGX-104 as monotherapy and in combination with nivolumab, ipilimumab, or docetaxel. Various markers including intratumoral ApoE and its receptor LRP1 in biopsy specimens, gene expression of LXR-targets in whole blood, serum markers including cytokines and lipids, as well as immune cell types such as MDSC, CD8 T-cells, and neutrophils in peripheral blood from patients were monitored at several time points. PK metrics were tracked to assess dose response relationships. Clinical outcomes such as objective response, time to disease progression, and duration on therapy were used for exploratory correlative analyses. A generally dose dependent increase in steady state exposure to RGX-104 was observed among all cohorts; the lowest efficacious exposure among patients with partial response was ~14,000 ng*h/mL. Treatment with RGX-104 at doses ranging from 120 mg BID to 240 mg BID induced expression of LXR targets, ApoE [2.7X (p=0.008) to 7.1X (p=0.007)] and ABCA1 [ 6.3X (p=1.20E-03) to 7X (p=8.1E-04] over baseline in a generally dose-dependent manner as assessed in whole blood. Similarly, MDSC depletion, ranging from 70%-90% relative to baseline, was observed in patients treated with RGX-104 along with concomitant CD8 T-cell activation; similar effects were noted in patients in combination cohorts. A model to explore dose dependency of change in immune cell types suggested that baseline levels of MDSC were most predictive of the magnitude of MDSC reduction after treatment, and that favorable clinical outcomes correlate with the extent of MDSC reduction and T cell activation. Low baseline levels of tumoral ApoE were associated with greater clinical benefit, with almost all patients with stable disease or partial response exhibiting ApoE tumor positive score of ≤20%; these patients also exhibited low/negative PD-L1 (<1%) staining, revealing a target specific tumor biomarker and PD-L1 subset that could support prospective patient selection. These and additional markers will be tracked in expansion cohorts of RGX-104 in combination with pembrolizumab and carboplatin/pemetrexed for 1st line treatment of patients with metastatic non-small cell lung cancer (PD-L1 <1%) and in combination with docetaxel for 2nd line treatment of patients with small cell lung cancer. Citation Format: Monica Mita, Alan Mita, Erika Hamilton, Gerald S. Falchook, Michael Postow, Bartosz Chmielowski, Russell J. Schilder, James Strauss, Emerson Lim, Shubham Pant, Angela Jain, Oliver Rixe, Rebecca Redman, Kevin B. Kim, Tomislav Dragovich, R. Donald Harvey, Igor Puzanov, Nimisha Schneider, Renee Deehan, Tobi Guennel, Joe Lin, Sohail Tavazoie, Roger Waltzman, Eric Rowinsky, Michael Szarek, Subhasree Sridhar, Robert Busby, Narayan Lebaka, Celia Andreu, Isabel Kurth, David Darst, Masoud Tavazoie, Syed Raza, Robert Wasserman, Foster C. Gonsalves. Correlative analysis of pharmacokinetics and pharmacodynamics of RGX-104, a first-in-class Liver-X-Receptor (LXR) agonist, and clinical outcomes in patients with advanced solid tumors [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr LB-133.

Intratumoral HLA-DR-/CD33+/CD11b+ Myeloid-Derived Suppressor Cells Predict Response to Neoadjuvant Chemoradiotherapy in Locally Advanced Rectal Cancer.

Capecitabine-based neoadjuvant chemoradiation therapy (nCRT) is currently the mainstay of treatment for locally advanced rectal cancer (LARC), prior to surgical tumor removal. While response to this treatment is partial, it carries significant risk of side effects. As of today, there is no accepted model to predict tumor response, and allow for patient stratification. The level of circulating Myeloid-derived suppressor cells (MDSCs), a subpopulation of early myeloid cells (EMCs), has been shown to correlate with prognosis and response to therapy in advanced colon cancer, but their role in LARC is not clear. We sought to study the effect of intratumoral and circulating levels of different EMCs subpopulations including MDSCs on response to nCRT. We analyzed tumor, normal mucosa, and peripheral blood samples from 25 LARC patients for their different EMCs subpopulation before and after nCRT, and correlated them with degree of pathologic response, as determined postoperatively. In addition, we compared LARC patient to 10 healthy donors and 6 metastatic patients. CD33+HLA-DR−CD16−CD11b+EMCs in the circulation of LARC patients were found to inhibit T-cell activation. Furthermore, elevated levels of CD33+HLA-DR− myeloid cells were found in the tumor relative to normal mucosa, but not in the circulation when compared to healthy subjects. Moreover, intratumoral, but not circulating levels of MDSCs correlated with clinical stage and response to therapy in patients treated with nCRT, with high levels of MDSCs significantly predicting poor response to nCRT. Importantly, therapy by itself, had significant differential effects on MDSC levels, leading to increased circulating MDSCs, concomitantly with decreasing intratumoral MDSCs. Our results suggest that high levels of intratumoral, but not circulating MDSCs may confer drug resistance due to immunomodulatory effects, and serve as a biomarker for patient stratification and decision-making prior to nCRT.

Clinical significance of peripheral blood CD11b+/CD33+/HLA-DR- myeloid cells in infants and children with infectious diseases and increased CRP.

Background: At early ages, recurrent or persistent infections are associated with increased serum C-reactive protein (CRP). Inflammatory mediators release inhibitory cells named myeloid-derived suppressor cell (MDSC) into circulating and tumor tissues. In the present study, we assayed the percentage and count of whole blood CD11b+/CD33+/HLA-DR- MDSCs or myeloid cells at early ages with infectious diseases and increased CRP. Methods: In this study, the clinical significance of CD11b+/CD33+/HLA-DR- MDSCs or myeloid cells was evaluated in whole blood samples from 40 patients with infectious disease and 20 healthy controls by flow cytometry analysis. Subsequently, the Pearson correlation between the percentage and absolute count of MDSCs with clinical parameters were obtained by SPSS analysis. A p value of < 0.05 was considered statistically significant. Results: We found a significantly higher level of MDSCs in infants and children with infectious diseases and increased CRP as compared to healthy controls (P=0.003). However, the results of analysis showed no correlation between MDSC percentage and count with grouped age and sex in patient groups. Conclusion: Our findings showed a significant correlation between the high level of serum CRP and peripheral blood CD11b+/CD33+/HLA-DR- MDSCs at early ages. This study could be a roadmap for future studies to use increased CRP as a potential prognostic biomarker to target MDSCs in children with recurrent or persistent infections.

The New Era of Cancer Immunotherapy: Targeting Myeloid-Derived Suppressor Cells to Overcome Immune Evasion.

Suppression of antitumor immune responses is one of the main mechanisms by which tumor cells escape from destruction by the immune system. Myeloid-derived suppressor cells (MDSCs) represent the main immunosuppressive cells present in the tumor microenvironment (TME) that sustain cancer progression. MDSCs are a heterogeneous group of immature myeloid cells with a potent activity against T-cell. Studies in mice have demonstrated that MDSCs accumulate in several types of cancer where they promote invasion, angiogenesis, and metastasis formation and inhibit antitumor immunity. In addition, different clinical studies have shown that MDSCs levels in the peripheral blood of cancer patients correlates with tumor burden, stage and with poor prognosis in multiple malignancies. Thus, MDSCs are the major obstacle to many cancer immunotherapies and their targeting may be a beneficial strategy for improvement the efficiency of immunotherapeutic interventions. However, the great heterogeneity of these cells makes their identification in human cancer very challenging. Since both the phenotype and mechanisms of action of MDSCs appear to be tumor-dependent, it is important to accurately characterized the precise MDSC subsets that have clinical relevance in each tumor environment to more efficiently target them. In this review we summarize the phenotype and the suppressive mechanisms of MDSCs populations expanded within different tumor contexts. Further, we discuss about their clinical relevance for cancer diagnosis and therapy.

Early Activation of Myeloid-Derived Suppressor Cells Participate in Sepsis-Induced Immune Suppression via PD-L1/PD-1 Axis.

Background: Myeloid derived suppressor cells (MDSCs) have been reported to keep elevating during sepsis. The current study was performed to investigate the immunosuppressive effect of MDSCs and their subsets with the underlying mechanisms.Methods: The immunosuppressive status was manifested by the apoptosis of splenocytes, quantity of T cells and PD-1 expression. The dynamics of quantity and PD-L1 level of MDSCs and the subsets were determined over time. The subset of MDSCs with high PD-L1 level was co-cultured with T cells to observe the suppressive effect.Results: Abdominal abscess was observed after 7 days post-sepsis. Five biomarkers related to organ functions were all significantly higher in the CLP group. The survival rate was consistent with the middle grade severity of sepsis model. Apoptosis of splenocytes increased over time during sepsis; CD4 + T cell decreased from day 1 post-sepsis; CD8+ T cells significantly reduced at day 7. The PD-1 expression in spleen was upregulated from an early stage of sepsis, and negatively related with the quantity of T cells. MDSCs were low at day 1 post-sepsis, but increased to a high level later; the dynamics of PMN-MDSC was similar to MDSCs. PD-L1 on MDSCs was highest at day 1 post-sepsis; PMN-MDSC was the main subset expressing PD-L1. The PMN-MDSC with high PD-L1 expression level extracted on day 1 after surgery from CLP mice significantly inhibited the proliferation of T cells.Conclusions: Sepsis-induced immunosuppression is initiated from a very early stage, a high expression level of PD-L1 on MDSCs and the main subset, PMN-MDSC might play a critical role suppressive role on T cells through PD-L1/PD-1 axis.

Abstract PR12: Genetic aberrations dictate distinct tumor immune landscape and chemosensitivity in HGSOC

Abstract High-grade serous ovarian cancer (HGSOC) is the most common and deadly subtype of ovarian epithelial cancer and is known for its aggressiveness, high recurrence rate, metastasis to other sites, development of resistance to conventional chemotherapy, and general lack of response to immune checkpoint inhibitors. The absence of genomically relevant, immune-competent HGSOC models represents a major barrier to developing new therapies. Taking advantage of a mouse fallopian tube organoid system that we developed, along with lentiviral gene transduction and/or CRISPR/Cas9 technology, we generated multiple new HGSOC models containing combinations of mutations seen in human HGSOC, including homologous recombination (HR)-proficient (Tp53-/-;Ccne1amp;Akt2ampand Tp53-/-;Ccne1amp;Krasamp) and -deficient (Tp53-/-;Brca1-/-;Pten-/-and Tp53-/-;Brca1-/-;Mycamp), and poorly characterized (Tp53-/-;Pten-/-;Nf1-/-) models. These models differ in proliferation, differentiation, and polarity/organoid structure in vitro, as well as tumorigenic capacity and behavior upon orthotopic injection into syngeneic mice. Organoids bearing different mutational spectra show differential sensitivity to conventional HGSOC chemotherapies, signal transduction inhibitors and DDR inhibitors, and evoke distinctly different immune microenvironment in vivo. In particular, the immune microenvironment induced by HR-deficient tumors shows more T-cell infiltration/Treg cells, whereas HR-proficient lines show lower T-cell infiltration but higher levels of myeloid-derived suppressor cells and macrophages. The results of these studies suggest novel, genotype-informed combination therapies for this devastating disease. This abstract is also being presented as Poster B19. Citation Format: Shuang Zhang, Sonia Iyer, Hao Ran, Wei Wei, Robert A. Weinberg, Benjamin G. Neel. Genetic aberrations dictate distinct tumor immune landscape and chemosensitivity in HGSOC [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research; 2019 Sep 13-16, 2019; Atlanta, GA. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(13_Suppl):Abstract nr PR12.

Physical activity delays accumulation of immunosuppressive myeloid-derived suppressor cells.

BackgroundMyeloid-derived suppressor cells (MDSCs) are potent suppressors of immune function and may play a key role in the development and progression of metastatic cancers. Aerobic exercise has been shown to have anticancer effects, yet the mechanisms behind this protection are largely unknown. Therefore, we examined the effects of physical activity on MDSC accumulation and function.MethodsFemale BALB/c mice were assigned to one of two primary groups: sedentary tumor (SED+TUM) or wheel run tumor (WR+TUM). After 6 weeks of voluntary wheel running, all animals were randomly subdivided into 4 different timepoint groups; 16, 20, 24, and 28 days post-tumor injection. All mice were inoculated with 4T1 mammary carcinoma cells in the mammary fat pad and WR groups continued to run for the specified time post-injection. Spleen, blood, and tumor samples were analyzed using flow cytometry to assess proportions of MDSCs.ResultsCells expressing MDSC biomarkers were detected in the spleen, blood, and tumor beginning at d16. However, since there was no evidence of immunosuppressive function until d28, we refer to them as immature myeloid cells (IMCs). Compared to SED+TUM, levels of IMCs in the spleen were significantly lower (p < 0.05) in WR+TUM at day 16 (33.0 ± 5.2%; 23.1 ± 10.2% of total cells, respectively) and day 20 (33.9 ± 8.1%; 24.3 ± 5.1% of total cells, respectively). Additionally, there were fewer circulating IMCs in WR+TUM at day 16 and MDSC levels were significantly lower (p < 0.05) in the tumor at day 28 in WR+TUM. Additionally, a non-significant 62% and 26% reduction in metastatic lung nodules was observed at days 24 and 28, respectively. At day 28, MDSCs harvested from SED+TUM significantly suppressed CD3+CD4+ T cell proliferation (3.2 ± 1.3 proliferation index) while proliferation in WR+TUM MDSC co-cultures (5.1 ± 1.7 proliferation index) was not different from controls.ConclusionsThese findings suggest that physical activity may delay the accumulation of immunosuppressive MDSCs providing a broader window of opportunity for interventions with immunotherapies.

Myeloid-derived suppressor cells in obstetrical and gynecological diseases.

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous group of myeloid-origin cells which have immunosuppressive activities in several conditions, such as cancer and inflammation. Recent research has also associated MDSCs with numerous obstetrical and gynecological diseases. During pregnancy, MDSCs accumulate to ensure maternal-fetal immune tolerance, whereas they are decreased in patients who suffer from early miscarriage or pre-eclampsia. While the etiology of endometriosis is still unknown, abnormal accumulation of MDSCs in the peripheral blood and peritoneal fluid, alongside an increased level of reactive oxygen species (ROS), has been observed in these patients, which is central to the cellular immune regulations by MDSCs. Additionally, the regulation of MDSCs observed in tumours is also applicable to gynecologic neoplasms, including ovarian cancer and cervical cancer. More recently, emerging evidence has shown that there are high levels of MDSCs in premature ovarian failure (POF) and in vitro fertilization (IVF), but the underlying mechanisms are unknown. In this review, the generation and mechanisms of MDSCs are summarized. In particular, the modulation of these cells in immune-related obstetrical and gynecological diseases is discussed, including potential treatment options targeting MDSCs.