Baseline circulating myeloid-derived suppressor cells and response to PD-1 inhibitor in non-small cell lung cancer patients

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Background: Inhibitors of immune checkpoint PD-1/PD-L1 (ICI) have become a care standard in non-small cell lung cancer (NSCLC). Despite promising results, some patients cannot take advantage of immunotherapy effects. Nowadays, neither predictive nor prognostic circulating biomarkers have been found in order to select patients or to predict response to ICI. Myeloid-derived suppressor cells (MDSC) are potent immunity suppressors and may represent both a potential prognostic and a predictive biomarker. Methods: Peripheral blood samples regarding 54NSCLC patients treated with nivolumab and 5 healthy donors were prospectively included. Early-MDSC: e-MDSC (LIN-/CD14-/CD15-/HLA-DR-/CD33+), monocytic-MDSC: M-MDSC (HLA-DR low/-/CD14+/CD15-/CD11b+), polymorphonuclear-MDSC: PMN-MDSC (HLA-DR low/-/CD14-/CD15+/CD11b+) were analyzed through flow cytometry. MDSC percentage was calculated from viable peripheral blood mononuclear cells. We assessed if e-MDSC,M-MDSC and PMN-MDSC levels detected before anti-PD-1 therapy correlate with both progression-free survival (PFS) and overall survival (OS). Results: 54 patients were prospectively included: 41 with adenocarcinoma and 13 with squamous NSCLC. When compared to healthy donors, patients had significantly higher levels of circulating e-MDSC(median (range): 0.13% (0-10.9) vs0.02%(0.01-0.14), p = 0.04) and M-MDSC (median (range): 4.55% (0.08-24.18) vs1.36% (0.77-3.76), p = 0.01). Cox proportional hazard regression analysis showed that high level of M-MDSC before anti-PD-1 therapy was associated with OS (HR [CI95%]: 1.08 [1.01; 1.15],p = 0.02) and PFS (HR [CI95%]: 1.07 [1.01;1.14], p = 0.02). No prognostic impact was observed regarding e-MDSC and PMN-MDSC. Conclusions: Our study suggests that a baseline circulating high level of M-MDSC is associated with poor survival. M-MDSC may be a predictive and prognostic biomarker in NSCLC patients treated with anti-PD1. Further studies have been scheduled, including MDSC monitoring during anti-PD1 treatment, in order to confirm our findings. These data would be interesting for the development of combined therapy, targeting the suppressive environment, with ICI.

Monitoring PD-L1 expression on circulating tumor cells (CTCs) in patients with NSCLC treated with PD1 inhibitors

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Background: Inhibitors of the immune checkpoint PD-1/PD-L1 have become a standard of care in NSCLC. Patient selection, currently based on PD-L1 expression in tumor tissue, is limited by its temporal and spatial heterogeneity. We hypothesized that monitoring PD-L1 staining of circulating tumor cells (CTCs) could represent a valuable non-invasive biomarker. Methods: Up to 3 blood samples were prospectively collected from patients with advanced NSCLC: i) pretreatment (nivolumab), ii) first follow-up, iii) progression. CTCs were isolated from 10 mL of blood using cell size-based technology (ISET, Rarecells). PD-L1 expression was assessed by immunofluorescence on CTCs and immunohistochemistry on tissue. Results: 162 samples from 96 patients were collected. PD-L1 expression could be assessed pretreatment on tissue and CTCs in 72% and 93%, respectively; and was ≥1% in 37% and 83%; ≥5% in 35% and 79%, respectively. No correlation between tissue and CTCs PD-L1 expressions was observed (Spearman coefficient correlation = 0.04, p = 0.77). At baseline, each 10/7.5 ml increase in CTCs count was associated with increased risk of death and progression (HR[95%CI]: 1.06 [1.005;1.117] p = 0.03 for OS and HR[95%CI]: 1.05 [1.01;1.10] p = 0.02 for PFS). The presence of PD-L1(+)CTC (≥1%) had no prognostic impact (OS: p = 0.89 and PFS: p = 0.55), but pretreatment PD-L1(+)CTCs were more frequent in the “non-responders” group (PFS < 6 months) (p = 0.04). Median CTC count was 30 (n = 96), 68.3 (n = 44) and 50.3 (n = 22) pretreatment, at the first follow-up and at progression, respectively. The changes in CTC count at the first follow-up had no impact on PFS (p = 0.45) or OS (p = 0.68). 96% of patients had PD-L1(+)CTCs at progression. Further analyses are ongoing to assess the prognostic value of the persistence of CTCs and PD-L1(+)CTCs at the first follow up and at progression. Conclusions: Analysis of PD-L1 expression on CTCs is highly feasible. PD-L1 expressions on tissue and CTCs are discordant, CTCs being more likely positives, suggesting false negatives occurring in small biopsies. Further analyses of the kinetics of this biomarker throughout ICI treatment, along with other circulating biomarkers, are ongoing. Clinical trial information: NCT02827344.

P2Y13 receptor regulates HDL metabolism and atherosclerosis in vivo

High-density lipoprotein (HDL) is known to protect against atherosclerosis by promoting the reverse cholesterol transport. A new pathway for the regulation of HDL-cholesterol (HDL-c) removal involving F1-ATPase and P2Y13 receptor (P2Y13R) was described in vitro, and recently in mice. However, the physiological role of F1-ATPase/P2Y13R pathway in the modulation of vascular pathology i.e. in the development of atherosclerotic plaques is still unknown. We designed a specific novel agonist (CT1007900) of the P2Y13R that caused stimulation of bile acid secretion associated with an increased uptake of HDL-c in the liver after single dosing in mice. Repeated dose administration in mice, for 2 weeks, stimulated the apoA-I synthesis and formation of small HDL particles. Plasma samples from the agonist-treated mice had high efflux capacity for mobilization of cholesterol in vitro compared to placebo group. In apoE^−/− mice this agonist induced a decrease of atherosclerotic plaques in aortas and carotids. The specificity of P2Y13R pathway in those mice was assessed using adenovirus encoding P2Y13R-shRNA. These results demonstrate that P2Y13R plays a pivotal role in the HDL metabolism and could also be a useful therapeutic agent to decrease atherosclerosis. In this study, the up-regulation of HDL-c metabolism via activation of the P2Y13R using agonists could promote reverse cholesterol transport and promote inhibition of atherosclerosis progression in mice.

Abstract 493: Antiatherosclerotic Activity of a New P2y13 Receptor Agonist (ct1007900) in Animal Models

The F1-ATPase/P2Y13 receptor pathway has been involved in the regulation of the HDL uptake liver and disposition via the reverse cholesterol transport. CT1007900 is a novel selective P2Y13 receptor agonist that has been shown to enhance the HDL uptake that results in the increased secretion of the bile acid, bile cholesterol and bile phospholipid into the gallbladder in mice.

In the present study, CT1007900 has been evaluated in three different animal models of atherosclerosis. In ApoE -/- flow cessation model, the administration of the drug decreased the cholesterol concentration in atherosclerotic plaques. In a high fat diet fed ApoE -/- mouse model, the prevention of the progression of the plaque in aorta was further evaluated after 4-week treatment with CT1007900. The treated animals had significant decreases in plaque area, cholesterol content, VCAM1 expression and macrophage content.

In the high fat diet fed rabbits, 4-week treatment reduced the cholesterol content by about 30% and also decreased the thickness of the plaques. The ApoA1 mRNA levels in the liver and ApoA1 protein concentration in the plasma increased in the drug-treated animals. The HDL content of the treated animals showed a very consistent pattern with a specific decrease in large HDL and an increase of the “intermediate” size HDL particles as compared to control animals. These intermediate HDL particles seem to be more efficient particles for the removal of cholesterol from atherosclerotic plaques by increasing efflux of cholesterol from the macrophages present in the lesions. The plasma samples from drug treated rabbits showed a dose-dependent increase in the cholesterol efflux in an in vitro assay using J774 cells.

These results clearly demonstrate that improving functionality of HDL rather than the levels of HDL could have a positive impact on the atherosclerotic pathology. These data also support that P2Y13 receptor agonists could be useful pharmacological therapeutics for the treatment of complications due to atherosclerotic disease.

Microsomal antiestrogen-binding site ligands induce growth control and differentiation of human breast cancer cells through the modulation of cholesterol metabolism

The microsomal antiestrogen-binding site (AEBS) is a high-affinity membranous binding site for the antitumor drug tamoxifen that selectively binds diphenylmethane derivatives of tamoxifen such as PBPE and mediates their antiproliferative properties. The AEBS is a hetero-oligomeric complex consisting of 3beta-hydroxysterol-Delta8-Delta7-isomerase and 3beta-hydroxysterol-Delta7-reductase. High-affinity AEBS ligands inhibit these enzymes leading to the massive intracellular accumulation of zymostenol or 7-dehydrocholesterol (DHC), thus linking AEBS binding to the modulation of cholesterol metabolism and growth control. The aim of the present study was to gain more insight into the control of breast cancer cell growth by AEBS ligands. We report that PBPE and tamoxifen treatment induced differentiation in human breast adenocarcinoma cells MCF-7 as indicated by the arrest of cells in the G0-G1 phase of the cell cycle, the increase in the cell volume, the accumulation and secretion of lipids, and a milk fat globule protein found in milk. These effects were observed with other AEBS ligands and with zymostenol and DHC. Vitamin E abrogates the induction of differentiation and reverses the control of cell growth produced by AEBS ligands, zymostenol, and DHC, showing the importance of the oxidative processes in this effect. AEBS ligands induced differentiation in estrogen receptor-negative mammary tumor cell lines SKBr-3 and MDA-MB-468 but with a lower efficiency than observed with MCF-7. Together, these data show that AEBS ligands exert an antiproliferative effect on mammary cancer cells by inducing cell differentiation and growth arrest and highlight the importance of cholesterol metabolism in these effects.

The prototypical inhibitor of cholesterol esterification, Sah 58-035 [3-[decyldimethylsilyl]-n-[2-(4-methylphenyl)-1-phenylethyl]propanamide], is an agonist of estrogen receptors

We have shown recently that estrogen receptor (ER) ligands share a diphenyl ethane pharmacophore with Sah 58-035 [3-[decyldimethylsilyl]-N-[2-(4-methylphenyl)-1-phenylethyl]-propanamide], a prototypical inhibitor of the acyl-cholesterolacyl-transferase (ACAT), which enabled us to establish that ER ligands were potent inhibitors of ACAT and blocked the formation of foam cells. In the present study, we have tested whether this structural similarity means that Sah 58-035 is an ER modulator. We report that Sah 58-035 bound to ERalpha and ERbeta with an IC(50) of 2.9 and 3.1 microM, respectively. Docking studies using molecular modeling of Sah 58-035 with the X-ray structure of the ER showed that Sah 58-035 fits well into the ligand binding site known for 4-hydroxy-tamoxifen. Despite having high three-dimensional structural similarities with the pure antiestrogen ICI 164,384 [(N-n-butyl-N-methyl-11-[3,17beta-di-hydroxyestra-1,3, 5(10)-trien-7alpha-yl]-undecanamide], we showed that Sah 58-035 is an agonist of ER for transcription and cellular proliferation. These data showed that Sah 58-035 was an estrogen receptor agonist and that the size and the chemical nature of the side chain were critical for agonist versus antagonist activity on ER. This new molecular mechanism of action for Sah 58-035 has to be taken into account in understanding better its pharmacological activities. Moreover, these data give new structural insights into the understanding of agonist versus antagonist activities of ER ligands and also for the conception of new drugs with a dual ACAT inhibition and ER modulation potential and their evaluation in different pathologies where both targets are involved, such as atherosclerosis, Alzheimer's disease, and cancer.