Toxic vascular effects of polystyrene microplastic exposure

Polystyrene microplastics (PSMPs) are some of the most common microplastic components, and the resulting pollution has become a global problem. Extensive studies have been conducted on the toxic effects of PSMPs on the heart, lungs, liver, kidneys, nerves, intestines and other tissues. However, the impact of PSMPs on vascular toxicity is poorly understood at present. The aim of this study was to reveal the vascular toxicity of microplastics (MPs). Patients were assigned to a calcification group (25 patients) or a non-calcification group (22 patients) based on the presence or absence of calcification in the thoracic aorta wall. We detected 7 polymer types in human feces. Patients with vascular calcification (VC) had higher levels of total MPs, polypropylene (PP) and polystyrene (PS) in feces than patients without VC. The thoracic aortic calcification score was significantly positively correlated with the total MP abundance (Spearman r = 0.8109, p < 0.0001), PP (Spearman r = 0.7211, p = 0.0160) and PS (Spearman r = 0.6523, p = 0.0471) in feces. We then explored the effects of PSMP exposure on normal and vitamin D3 + nicotine (VDN)-treated rats. PSMP exposure induced mild VC in normal rats and aggravated VC in VDN-treated rats. PSMP exposure disturbed the gut microbiota, causing Proteobacteria and Escherichia_Shigella to be the dominant phylum and genus, respectively. It also induced intestinal inflammatory responses in normal rats, aggravated intestinal inflammation in VDN-treated rats, impaired the intestinal mucosal barrier, and increased intestinal permeability. This study provides a theoretical basis for the risk assessment of MP-induced cardiovascular disease.

Meteorin-like protein elevation post-exercise improved vascular inflammation among coronary artery disease patients by downregulating NLRP3 inflammasome activity

BACKGROUND

Coronary artery disease (CAD) has become the most common cause of death worldwide. However, the negative effects of CAD are able to be alleviated via exercises, possibly via increased production of meteorin-like protein (Metrnl). In this study, we aim to evaluate the connection between Metrnl production during exercise with lowered CAD risk and severity.

METHODS

Two age and gender-matched groups of 60 human patients, one with CAD, and one without were randomly recruited. The CAD group were subjected to continuous training exercises. Mice were exercised by using a treadmill, establishing an animal exercise model. ELISA was used to measure plasma Metrnl and inflammatory factors. To determine the impact of Metrnl on glucose metabolism, oxygen consumption and extracellular acid rates were taken for untreated, palmitic acid (PA)-treated, and PA+Metrnl co-treated human umbilical vein endothelial cells. Western blot was used to measure expression levels for the NLR family pyrin domain containing 3 inflammasome.

RESULTS

CAD patients had lower Metrnl levels compared to non-CAD controls. Furthermore, higher Metrnl levels post-exercise were inversely associated with LDL, inflammatory cytokines, and CAD severity, as well as being positively associated with HDL. Metrnl was able to counteract against PA-induced HUVEC glucose metabolic dysfunction via reducing ROS production, which in turn lowered NLRP3 inflammasome expression, thereby serving as the basis behind the inverse correlation between Metrnl and inflammatory cytokines.

CONCLUSIONS

Exercise was able to increase Metrnl production from skeletal muscle among CAD patients, and subsequently improve patient atherosclerosis via counteracting against endothelial metabolic dysfunction and pro-inflammatory activities.

Effect of pharmacological treatment on outcomes of heart failure with preserved ejection fraction: an updated systematic review and network meta-analysis of randomized controlled trials

Background

Optimal treatment strategies for patients with heart failure with preserved ejection fraction (HFpEF) remain uncertain. The goal of this study was to compare the treatment effects of different therapeutic agents for patients with HFpEF.

Methods

Randomized controlled trials (RCTs) published before June 2022 were searched from PubMed, Clinical Trials gov, and the Cochrane Central Register databases. Combined odds ratios (ORs) with 95% confidence intervals (CI) were calculated for the primary and secondary outcomes. All-cause death was the primary endpoint and cardiac death, hospitalization for HF, and worsening HF (WHF) events were secondary endpoints in this meta-analysis.

Results

Fifteen RCTs including 31,608 patients were included in this meta-analysis. All-cause and cardiac death were not significantly correlated between drug treatments and placebo. Compared with placebo, angiotensin-converting enzyme inhibitors (ACEIs), angiotensin receptor neprilysin inhibitors (ARNIs), and sodium-glucose cotransporter-2 (SGLT2) inhibitors significantly reduced HF hospitalizations [odds ratio (OR) = 0.64, (95% confidence interval (95%CI 0.43 − 0.96), OR = 0.73, (95%CI 0.61 − 0.86), and OR = 0.74, (95%CI 0.66 − 0.83), respectively] without heterogeneity among studies. Only SGLT2 inhibitors significantly reduced WHF events [OR = 0.75, (95%CI 0.67 − 0.83)].

Conclusions

No treatments were effective in reducing mortality, but ARNIs, ACEIs or SGLT2 inhibitors reduced HF hospitalizations and only SGLT2 inhibitors reduced WHF events for patients with HFpEF.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12933-022-01679-2.

Iron metabolism-related genes reveal predictive value of acute coronary syndrome

Iron deficiency has detrimental effects in patients with acute coronary syndrome (ACS), which is a common nutritional disorder and inflammation-related disease affects up to one-third people worldwide. However, the specific role of iron metabolism in ACS progression is opaque. In this study, we construct an iron metabolism-related genes (IMRGs) based molecular signature of ACS and to identify novel iron metabolism gene markers for early stage of ACS. The IMRGs were mainly collected from Molecular Signatures Database (mSigDB) and two relevant studies. Two blood transcriptome datasets GSE61144 and GSE60993 were used for constructing the prediction model of ACS. After differential analysis, 22 IMRGs were differentially expressed and defined as DEIGs in the training set. Then, the 22 DEIGs were trained by the Elastic Net to build the prediction model. Five genes, PADI4, HLA-DQA1, LCN2, CD7, and VNN1, were determined using multiple Elastic Net calculations and retained to obtain the optimal performance. Finally, the generated model iron metabolism-related gene signature (imSig) was assessed by the validation set GSE60993 using a series of evaluation measurements. Compared with other machine learning methods, the performance of imSig using Elastic Net was superior in the validation set. Elastic Net consistently scores the higher than Lasso and Logistic regression in the validation set in terms of ROC, PRC, Sensitivity, and Specificity. The prediction model based on iron metabolism-related genes may assist in ACS early diagnosis.

Comparative efficacy and safety of antiplatelet or anticoagulant therapy in patients with chronic coronary syndromes after percutaneous coronary intervention: A network meta-analysis of randomized controlled trials

Aimed to evaluate and compare the interactive effects of different antiplatelet or anticoagulation strategies in patients with chronic coronary syndromes (CCS) after percutaneous coronary intervention (PCI). Randomized controlled trials comparing different antiplatelet or anticoagulant strategies in patients with CCS after PCI were included. The primary outcomes were major adverse cardiovascular event (MACE), mortality, ischemic and bleeding events. Compared to aspirin alone, addition of prasugrel or ticagrelor to aspirin resulted in lower risk of myocardial infarction (MI) [odds ratio (OR): 0.38 (95% confidence interval 0.38–0.62); 0.810–0.84 (0.69–0.98)] and any stroke [0.56 (0.42–0.75)] at the expense of increased risk of major bleeding [1.79 (1.34–2.39); 2.08–2.38 (1.56–3.28)], whereas, clopidogrel monotherapy reduced the risk of any stroke, major bleeding, and intracranial bleeding. On subgroup analysis, compared with aspirin alone, addition of prasugrel resulted in lower MACE [0.72 (0.60–0.86)], MI [0.48 (0.38–0.62)], and stent thrombosis [0.29 (0.09–0.91)], whereas, addition of rivaroxaban 2.5 mg resulted in lower risk of MACE [0.72 (0.60–0.87)], cardiac death [0.71 (0.52–0.98)] and any stroke [0.65 (0.45–0.95)], but not reduced MI. Both prasugrel and rivaroxaban 2.5 mg increased major bleeding [1.79 (1.34–2.39); 1.72 (1.33–2.22)]. Clopidogrel monotherapy was associated with lower MACE [0.72 (0.58–0.90)], any stroke [0.42 (0.24–0.73)], and major bleeding [0.62 (0.40–0.96)]. Adding prasugrel or ticagrelor led to a reduced incidence of MI and prasugrel was also found to reduce the risk of MACE and stent thrombosis in CCS patients with low risk of bleeding after PCI. Clopidogrel monotherapy has advantage in reducing MACE, stroke, and major bleeding events in CCS patients at high risk of bleeding after PCI.

Systematic Review Registration:https://clinicaltrials.gov/, PROSPERO Identifier: CRD 42021291050.

Evolocumab enables rapid LDL-C reduction and inflammatory modulation during in-hospital stage of acute coronary syndrome: A pilot study on Chinese patients

Background and aims

Proprotein convertase subtilisin/kexin type 9 (PCSK9) has long been considered a key regulator in lipid metabolism. Its role as a potential player in immune response has recently earned much attention. However, the effects of evolocumab, an approved PCSK9 monoclonal antibody, on lipid reduction and inflammation regulation in Chinese patients with acute coronary syndrome (ACS) during their in-hospital stage after an index event are not well known.

Methods

We conducted a case-crossover pilot study (http://www.clinicaltrials.gov/, NCT04730648) involving 31 patients hospitalized for ACS with elevated low-density lipoprotein cholesterol (LDL-C) level (≥70 mg/dL despite high-intensity statin) and 8 age- and gender-matched patients without coronary heart disease (CHD) as the baseline control. The patients with ACS received one dose of subcutaneous evolocumab (140 mg) on top of 10 mg/day rosuvastatin during hospitalization. Blood samples at baseline and 72 h post-evolocumab administration were collected for lipid and cytokine assessments.

Results

The patients without CHD shared similar risk factors and LDL-C levels with the patients with ACS but exhibited a more activated inflammatory status. After single-dose in-hospital evolocumab, the median LDL-C level of patients with ACS decreased from 109.0 to 41.4 mg/dL as early as 72 h, accompanied with reductions in other atherogenic lipids. Systemic inflammatory pattern was also altered, rendering a decrease in pro-inflammatory and anti-inflammatory cytokines.

Conclusion

In this case-crossover study of the effect of PCSK9 antibody among Chinese patients, evolocumab on top of high-intensity statin during hospitalization led to a remarkable and rapid reduction in atherogenic lipids and an alteration in inflammatory status at early-stage post-ACS.

Comparison of Pharmacological Treatment Effects on Long-Time Outcomes in Heart Failure With Preserved Ejection Fraction: A Network Meta-analysis of Randomized Controlled Trials

Beneficial effects of therapeutic drugs are controversial for heart failure with preserved ejection fraction (HFpEF). This meta-analysis aimed to evaluate and compare the interactive effects of different therapeutic drugs and placebo in patients with HFpEF. A comprehensive search was conducted using PubMed, Google Scholar, and Cochrane Central Register to identify related articles published before March 2021. The primary outcome was all-cause mortality. Secondary outcomes were cardiovascular mortality, heart failure (HF) hospitalization, and worsening HF events. A total of 14 randomized controlled trials, comprising 19,573 patients (intervention group, n = 9,954; control group, n = 9,619) were included in this network meta-analysis. All-cause mortality, cardiovascular mortality, and worsening HF events among therapeutic drugs and placebo with follow-up of 0.5–4 years were not found to be significantly correlated. The angiotensin receptor neprilysin inhibitor (ARNI) and angiotensin-converting enzyme inhibitor (ACEI) significantly reduced the HF hospitalizations compared with placebo (hazard ratio [HR] 0.73, 95% confidence interval [CI] 0.60–0.87 and HR 0.64, 95% CI 0.43–0.96, respectively), without heterogeneity among studies. The ARNI was superior to angiotensin receptor blocker (ARB) in reducing HF hospitalizations (HR 0.80, 95% CI 0.71–0.91), and vericiguat 10 mg ranked worse than beta-blockers for reducing all-cause mortality in patients with HFpEF (HR 3.76, 95% CI 1.06–13.32). No therapeutic drugs can significantly reduce mortality, but the ARNI or ACEI is associated with the low risk of HF hospitalizations for patients with HFpEF.

Systematic Review Registration:https://www.crd.york.ac.uk/prospero/, identifier CRD42021247034

Intravenous morphine use in acute heart failure increases adverse outcomes: a meta-analysis

Intravenous morphine is a controversial treatment for acute heart failure (AHF). This study aimed to evaluate and compare the efficacy of intravenous morphine treatment vs. no morphine treatment in AHF patients. Relevant research conducted before June 2020 was retrieved from electronic databases. One unpublished study of our own was also included. Studies were eligible for inclusion if they compared AHF patients treated with intravenous morphine and patients who did not receive morphine. This meta-analysis included three propensity-matched cohorts and two retrospective analyses, involving a total of 149,967 patients (intravenous-morphine group, n = 22,072; no-morphine group, n = 127,895). There was a non-significant increase in the in-hospital mortality in the morphine group (combined odds ratio [OR] = 2.14, 95% confidence interval [CI]: 0.88-5.23, p = 0.095, I² = 97.1%). However, subgroup analyse showed that the rate of in-hospital mortality with odds of 1.41 times more likely (95% CI: 1.11-1.80, p = 0.005, I² = 0%) in those receiving vs. not receiving intravenous morphine. No significant correlation was found between intravenous morphine and invasive mechanical ventilation (OR = 2.19, 95% CI: 0.84-5.73, p = 0.10, I² = 94.2%; subgroup analysis: OR = 2.24, 95% CI: 0.70-7.21, p = 0.176, I² = 95.1%) or long-term mortality (hazard ratio = 1.15, 95% CI: 0.96-1.34, p = 0.335; I² = 8.6%). The administration of intravenous morphine to patients with AHF may be related to in-hospital mortality, but not to invasive mechanical ventilation and long-term mortality.

Optimal reference genes for real-time quantitative PCR and the expression of sigma factors in Acidithiobacillus caldus under various conditions

AIMS

Acidithiobacillus caldus is an important sulphur-oxidizing bacterium that plays crucial roles in the bioleaching industry. This study aims to analyse the optimal reference gene for real-time quantitative PCR (RT-qPCR) under different conditions and investigate the transcription levels of the sigma factor genes in the stress response.

METHODS AND RESULTS

We selected six housekeeping genes and analysed them via RT-qPCR using two energy resources, under four stress conditions. Three statistical approaches BestKeeper, geNorm, and NormFinder were utilized to determine transcription stability of these reference genes. The gapdH gene was the best internal control gene using elemental sulphur as an energy resource and under heat stress, map was the best internal control gene under pH and osmotic stress, era was the best internal control gene for the K₂ S₄ O₆ energy resource, and rpoC was the best internal control gene under Cu²⁺ stress. Furthermore, the expressional levels of 11 sigma factors were analysed by RT-qPCR in the stress response.

CONCLUSIONS

Stable internal control genes for RT-qPCR analysis of A. caldus were determined, and the expression patterns of sigma factor genes of A. caldus were investigated.

SIGNIFICANCE AND IMPACT OF THE STUDY

The identification of the optimal reference gene and analysis of transcription levels of sigma factors in A. caldus can provide clues for reference gene selection and the study of sigma factor function.

Satisfactory Long-term Outcomes of Thoracic Endovascular Aortic Repair With a Bare Stent for Acute Complicated Type B Aortic Dissections

PURPOSE

To compare the clinical outcomes after thoracic endovascular aortic repair (TEVAR) with a bare stent to those after TEVAR alone in patients with complicated acute type B aortic dissection (cATBAD).

MATERIALS AND METHODS

A prospective, randomized trial was conducted at 2 medical centers in China between 2010 and 2013. Patients with cATBAD were randomly assigned to receive TEVAR with a bare stent (n=42) or TEVAR only (n=42). Patients were scheduled to undergo computed tomography angiography at 3, 6, and 12 months and then annually to 5 years. The primary endpoint was all-cause mortality at 5 years; secondary outcomes were a composite of complications (endoleak, stent-graft-induced new entry, aortic rupture, and secondary intervention) and aortic remodeling at 1 and 5 years.

RESULTS

All-cause death occurred in 1 (2.4%) patient in the TEVAR with bare stent group (lung cancer) and 5 patients (11.9%) in the TEVAR group (4 aorta-related) during the 5-year follow-up (log-rank p=0.025). The 1- and 5-year rates of complications and secondary interventions did not differ between the groups. Patients in the TEVAR with bare stent group had higher increases in the thoracic true lumen diameter (19.7±3.6 vs 17.0±6.2 mm, p=0.018) and abdominal true lumen diameter (13.7±4.8 vs 7.2±6.1 mm, p<0.001) and a higher incidence of complete false lumen thrombosis (80.9% vs 47.6%, p=0.005) at the 1-year follow-up. However, no between-group differences in the changes of aortic remodeling parameters were observed between the 1- and 5-year follow-up periods.

CONCLUSION

The addition of a distal bare stent to a thoracic stent-graft during TEVAR was associated with significantly improved long-term survival in cATBAD patients vs TEVAR only, likely due to the prevention of true lumen collapse and improvement of complete false lumen thrombosis of the dissected aorta.

Optical rogue waves in coupled fiber Raman lasers

For coupled linear cavity-random fiber Raman lasers, for the first time, to the best of our knowledge, we demonstrate a new mechanism of emergence of the random pulses, with the anomalous statistics satisfying optical rogue waves' criteria experimentally. The rogue waves appear as a result of the coupling of two Raman cascades, namely, a linear cavity laser with a wavelength of 1.55 µm and a random laser with a wavelength nearly 1.67 µm, along with coupling of the orthogonal states of polarization (SOPs). The coherent coupling of SOPs causes localization of the trajectories in the vicinity of these states, whereas polarization instability drives escape taking the form of chaotic oscillations. Antiphase dynamics in two cascades result in the suppression of low amplitude chaotic oscillations and enable the anomalous spikes, satisfying rogue waves criteria.

Combination of pegylated interferon-alpha and nucleos(t)ide analogue treatment enhances the activity of natural killer cells in nucleos(t)ide analogue experienced chronic hepatitis B patients

A combination of pegylated interferon-alpha (peg-IFN-α) and nucleos(t)ides analogue (NA) therapy can effectively reduce hepatitis B surface antigen (HBsAg), especially in NA-experienced chronic hepatitis B (CHB) patients. However, the immune mechanism of this therapy is unclear. Forty NA-experienced CHB patients were enrolled into this study. The frequencies of peripheral blood natural killer (NK) cells, dendritic cells (DCs), CD4⁺ T cells, CD8⁺ T cells, T helper (Th) cells, regulatory T cells (T_reg ), B cells and follicular T helper (Tfh) cells were evaluated by flow cytometry. Seven of the 40 patients converted to peg-IFN-α combined with NA treatment, while the other 33 continued to NA therapy. The decrease in HBsAg was more pronounced in the combination treatment group, and only patients receiving combination treatment achieved HBsAg loss. The frequency and absolute number of CD56^bright NK cells in the combination treatment group increased significantly compared with the NA treatment group, whereas the CD56^dim NK cells were decreased. In the NA treatment group, the proportions of CD4⁺ T_N , CD8⁺ T_N , CD19⁺ B and cytotoxic T lymphocyte antigen-4 (CTLA-4)⁺ CD4⁺ T cells were increased, while the proportions of CD4⁺ T_EM , CD8⁺ T_EM , CD25⁺ CD4⁺ T_reg , CD25^high CD4⁺ T_reg , CD127^low CD25⁺ T_reg , programmed cell death 1 (PD-1)⁺ CD4⁺ T, PD-1⁺ CD8⁺ T, CTLA-4⁺ CD8⁺ T, CCR4⁺ CD25⁺ T_reg and CCR4⁺ CD25^high T_reg cells were decreased after therapy. For NA-experienced CHB patients who achieved low HBsAg levels, combination treatment is more likely to result in HBsAg decline and HBsAg clearance by increasing the activity of CD56^bright NK cells.

Drug-coated balloon versus drug-eluting stent for treating de novo coronary lesions in large vessels: a meta-analysis of clinical trials

BACKGROUND

Studies examining the efficiency of drug-coated balloon (DCB) compared to drug-eluting stents (DES) for de novo lesions in large vessels have reported inconsistent results.

OBJECTIVE

This comprehensive meta-analysis of clinical trials compared the efficacy and safety of DCB and DES for the treatment of de novo coronary lesions.

METHODS

The authors formally searched electronic databases before October 2019 to identify randomized and non-randomized clinical trials (RCTs and non-RCTs, respectively). Clinical trials were eligible for inclusion if they compared DCB with DES in patients with coronary lumen diameters >2.5 mm.

RESULTS

Three RCTs and one non-RCT with a total of 321 patients were included in our meta-analysis (DCB group = 152, DES group = 169). The primary endpoint was in-segment late lumen loss (LLL) with a standardized mean difference (SMD) of -0.07 (95% confidence interval [CI]: -0.31, 0.316; P = 0.548) and the secondary endpoint was target lesion revascularization (TLR) with a risk ratio (RR) of 1.17 (95% CI: 0.46, 2.95; P = 0.746).

CONCLUSION

This meta-analysis indicated that DCB might be non-inferior to DES as evidenced by quantitative coronary angiography (QCA) assessed at 6-9 months after percutaneous coronary intervention in patients presenting with coronary artery disease.

Combined therapy of infusion of DC from rats with higher expression of IDO and CD40L on rejection post heart transplantation

OBJECTIVE

Indoleamine 2, 3-dioxygenase (IDO) can inhibit rejection of graft via inducing T cell apoptosis. CD40L monoclonal antibody (mAb) inhibits T cell activation. However, the effects of the combination of infusion of dendritic cell (DC) from IDO over-expressed donor mice and CD40L mAb on the treatment of graft rejection after heart transplantation have not been reported.

MATERIALS AND METHODS

Allogeneic heart transplantation mouse model was established. Recipient mice were divided into three groups, including control group, IDO group (in which DC donors received adenoviral vector of IDO) and combined therapy group (which received both IDO over-expressed DC infusion and CD40L mAb injection post transplantation). Survival time and cardiac function were observed, with IDO expression being quantified. Flow cytometry (FCM) was used to analyze T cell apoptosis, while enzyme linked immunosorbent assay (ELISA) was adopted to test the levels of interferon-γ (IFN-γ), interleukin-2 (IL-2), interleukin-10 (IL-10) and interleukin-6 (IL-6).

RESULTS

IDO expression was significantly elevated in both IDO and combined therapy groups, with enhanced T cell apoptosis compared to control group (p < 0.05). Both groups had better survival time and cardiac functions compared to control group, along with increased IL-10/IL-6 expression and suppressed INF-γ and IL-2 expression (p < 0.05). However, combined therapy had a better efficiency compared to IDO group (p < 0.05).

CONCLUSIONS

Combined therapy of high IDO expressed mouse DC perfusion with CD40L mAb can elongate the survival time of recipient heart and inhibit rejection reaction via facilitating T cell apoptosis. Meanwhile, combined therapy could also regulate the expression of some immune suppressant factors and mediate the Th1/Th2 cytokine balance.

Decreased A20 expression on circulating CD56bright NK cells contributes to a worse disease status in patients with ankylosing spondylitis

A20, a pivotal anti-inflammatory protein, preserves immune homeostasis and regulates prolonged inflammation. A previous study has shown that A20 expression levels are down-regulated in peripheral blood mononuclear cells (PBMCs) from patients with ankylosing spondylitis (AS). However, the precise role of A20 in reducing autoimmune disorders needs to be further elucidated. In this study, A20 expression was found to be preferentially reduced on circulating CD56^bright natural killer (NK) cells in patients with AS, and its level was negatively correlated with that of proinflammatory cytokines. Further investigation demonstrated that A20 reduces interferon (IFN)-γ and tumour necrosis factor (TNF)-α production in CD56^bright NK cells after stimulation with monokines or phorbol myristate acetate (PMA)/ionomycin(P/I). Furthermore, CD56^bright NK cells isolated from AS patients promote TNF-α secretion by autologous monocytes, and increasing the A20 expression level partially attenuates this process. More importantly, decreased A20 expression on circulating CD56^bright NK cells is associated with worse disease status in patients with AS. Our findings reveal that A20 participates in the pathogenesis of AS by negatively regulating CD56^bright NK cells and that its reduced expression contributes to a worsened disease status in patients with AS.

Abstract 2709: TTI-622 (SIRPα-IgG4 Fc), a CD47-blocking innate immune checkpoint inhibitor, suppresses tumor growth and demonstrates enhanced efficacy in combination with antitumor antibodies in both hematologic and solid tumor models

Tumor cells frequently evade macrophage-mediated destruction by increasing cell surface expression of CD47, which delivers an anti-phagocytic (“do-not-eat”) signal by binding the inhibitory signal regulatory protein α (SIRPα) receptor on macrophages. Previous studies have shown that blockade of the CD47-SIRPα pathway using TTI-621, a soluble SIRPα-IgG1 Fc fusion protein, triggers macrophage phagocytosis of tumor cells in vitro, and potently inhibits tumor growth in vivo. In the current study, the in vitro and in vivo efficacy of TTI-622, a soluble SIRPα-Fc variant protein containing an IgG4 Fc tail, was evaluated in multiple model systems.

Unlike CD47-blocking antibodies, TTI-622 binds minimally to human erythrocytes, and does not induce hemagglutination in vitro. Therefore, it avoids a large circulating antigen sink, and is less likely to cause anemia in patients. Additionally, TTI-622 potently induces phagocytosis of a broad panel of tumor cells derived from patients with both hematological and solid tumors. Although in vitro phagocytosis of human platelets is also observed, TTI-622 preferentially induces phagocytosis of tumor cells over platelets in a competitive phagocytosis assay.

The in vivo efficacy of TTI-622 monotherapy and/or combination therapy was evaluated in different tumor models. In a DLBCL (Toledo) xenograft tumor model, both early and delayed treatments resulted in statistically significant decreases in tumor growth, and improved survival relative to treatment with control Fc. In the Burkitt lymphoma (Daudi) and multiple myeloma (MM.1S) xenograft tumor models, the potential of combining TTI-622 with daratumumab (anti-CD38 antibody) was also explored. In both models, TTI-622 monotherapy demonstrated partial tumor growth inhibition. However, the therapeutic efficacy was further enhanced when TTI-622 was combined with daratumumab. Intriguingly, a TTI-622 non-responsive head and neck cancer (FaDu) xenograft tumor model became responsive by combining TTI-622 with suboptimal doses of cetuximab (anti-EGFR antibody). The combination of TTI-622 with cetuximab resulted in a statistically significant decrease in tumor growth, and improved survival relative to monotherapy treatments.

Collectively, these results demonstrate that TTI-622 induces potent, tumor-specific macrophage phagocytosis across a range of hematological and solid tumors, and is efficacious as a monotherapy agent in a DLBCL xenograft tumor model. Furthermore, TTI-622 potentiates the efficacy of daratumumab and cetuximab in hematological and solid xenograft tumor models, respectively. These data support the clinical evaluation of TTI-622 in combination with anti-tumor antibodies in cancer patients with both solid and hematological malignancies.

Citation Format: Gloria H. Y. Lin, Natasja N. Viller, Marilyse Chabonneau, Laura Brinen, Tapfuma Mutukura, Karen Dodge, Simone Helke, Vien Chai, Violetta House, Vivian Lee, Hui Chen, Alison O'Connor, Debbie Jin, Rene Figueredo, Saman Maleki Vareki, Mark Wong, Emma Linderoth, Lisa D. Johnson, Xinli Pang, James Koropatnick, Jeff Winston, Penka S. Petrova, Robert A. Uger. TTI-622 (SIRPα-IgG4 Fc), a CD47-blocking innate immune checkpoint inhibitor, suppresses tumor growth and demonstrates enhanced efficacy in combination with antitumor antibodies in both hematologic and solid tumor models [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 2709.

Abstract 2720: The CD47-blocking innate immune checkpoint inhibitor, TTI-621, triggers CD47-mediated tumor cell apoptosis

CD47 is a cell surface glycoprotein of the immunoglobulin superfamily that is utilized by tumor cells to avoid immune destruction. Overexpression of the CD47 ligand on tumor cells provides a “do-not-eat” signal when bound to its receptor, signal regulatory protein α (SIRPα), on macrophages, resulting in inhibition of phagocytosis and tumor survival. TTI-621 is a soluble SIRPα recombinant fusion protein with an IgG1 Fc tail that triggers macrophage phagocytosis of tumor cells in vitro, and potently inhibits tumor growth in vivo. It is currently being evaluated in two clinical studies in patients with hematologic and solid cancers (NCT02663518 and NCT02890368). TTI-621's pro-phagocytic effect has been shown to be a result of blockade of the CD47-SIRPα pathway as well as activation of Fc gamma receptors (FcγR) on macrophages. However, engagement of CD47 has also been shown to directly induce apoptosis in tumor cells. Therefore, the objective of this study was to further examine the pro-apoptotic potential of TTI-621.

The induction of apoptosis in tumor cells by TTI-621 was evaluated using flow cytometry and protein expression assays. Ligating CD47 with immobilized TTI-621 efficiently induced apoptosis in malignant T-ALL and DLBCL cells but had no effect on apoptosis in normal peripheral blood mononuclear cells. Immobilized TTI-621 or anti-CD47 mAb promoted caspase-independent but PLCγ-1-dependent apoptosis. Under conditions of cellular stress, both soluble and immobilized TTI-621 induced apoptosis in T-ALL cells. In contrast to immobilized TTI-621, treatment of stressed tumor cells with soluble TTI-621 triggered caspase-dependent but PLCγ-1-independent apoptosis. In addition, anchoring the IgG1 Fc tail of TTI-621 to FcγR-expressing cells enhanced tumor cell apoptosis in a dose-dependent and CD47-dependent manner.

These results suggest that in addition to blocking the anti-phagocytic “do-not-eat” signal on tumor cells and activating FcγR on macrophages, binding of TTI-621 to FcγRs on tumor-infiltrating immune cells may provide a cross-linking scaffold to enhance TTI-621-mediated apoptosis via CD47 on cancer cells. Additionally, under conditions of cellular stress, TTI-621 may induce tumor cell death directly via binding to CD47 on malignant cells, in a cell-autonomous, cytotoxic mechanism. Thus, TTI-621 may employ multiple mechanisms to elicit its anti-tumor effects.

Citation Format: Julia Bershadsky Izrailit, Natasja Nielsen Viller, Xinli Pang, Penka S. Petrova, Robert A. Uger, Jeff Winston, Emma Linderoth. The CD47-blocking innate immune checkpoint inhibitor, TTI-621, triggers CD47-mediated tumor cell apoptosis [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 2720.

Targeted next-generation sequencing and parental genotyping in sporadic Chinese Han deaf patients

The interpretation of the targeted next-generation sequencing (NGS) results can be challenging for variants identified in the sporadic deaf patients. In this study, we performed targeted NGS of 143 deafness-associated genes in 44 sporadic deaf patients and use parental genotyping to test whether the candidate pathogenic variants complied with recessive or de novo pattern. Of 29 recessive candidate variants with minor allele frequencies (MAFs) less than 0.005, 3 pairs of apparent compound heterozygous variants were inherited from the same parental allele, ruling out their pathogenic roles. In addition, non-segregation of an OTOA p.Gln293Arg variant led to the discovery of a genomic microdeletion of OTOA on the opposite allele by copy number variation analysis. Overall, 13 pairs of recessive candidate variants were deemed causative in 13 patients. Of the 28 dominant candidate variants with MAFs less than 0.0005, none occurred de novo, suggesting that they were not disease causing. Our results revealed that targeted NGS in sporadic deaf patients may generate a significant false-positive rate. Parental genotyping is a simple but effective step toward minimizing the false-positive results. Our study also showed that de novo variants in dominant deafness genes may not be a common cause for sporadic deafness.

The effectiveness of anterior cervical decompression and fusion for the relief of dizziness in patients with cervical spondylosis: a multicentre prospective cohort study

AIMS

Cervical spondylosis is often accompanied by dizziness. It has recently been shown that the ingrowth of Ruffini corpuscles into diseased cervical discs may be related to cervicogenic dizziness. In order to evaluate whether cervicogenic dizziness stems from the diseased cervical disc, we performed a prospective cohort study to assess the effectiveness of anterior cervical discectomy and fusion on the relief of dizziness.

PATIENTS AND METHODS

Of 145 patients with cervical spondylosis and dizziness, 116 underwent anterior cervical decompression and fusion and 29 underwent conservative treatment. All were followed up for one year. The primary outcomes were measures of the intensity and frequency of dizziness. Secondary outcomes were changes in the modified Japanese Orthopaedic Association (mJOA) score and a visual analogue scale score for neck pain.

RESULTS

There were significantly lower scores for the intensity and frequency of dizziness in the surgical group compared with the conservative group at different time points during the one-year follow-up period (p = 0.001). There was a significant improvement in mJOA scores in the surgical group.

CONCLUSION

This study indicates that anterior cervical surgery can relieve dizziness in patients with cervical spondylosis and that dizziness is an accompanying manifestation of cervical spondylosis. Cite this article: Bone Joint J 2018;100-B:81-7.

Abstract 2653: The anti-myeloma activity of TTI-621 (SIRPαFc), a CD47-blocking immunotherapeutic, is enhanced when combined with a proteasome inhibitor

CD47 is transmembrane glycoprotein that delivers an anti-phagocytic (“do not eat”) signal by binding to its receptor, signal-regulatory protein α (SIRPα), on the surface of macrophages. Many tumors, including multiple myeloma (MM), express high levels of CD47 as a means to exploit the CD47-SIRPα pathway and escape macrophage-mediated immune surveillance. TTI-621 (SIRPαFc) is a soluble recombinant fusion protein consisting of the CD47-binding domain of human SIRPα linked to the Fc region of human IgG1. It is designed to promote anti-tumor responses by blocking the CD47 “do not eat” signal and engaging activating Fcγ receptors on macrophages. We have previously shown that TTI-621 enhances phagocytosis of malignant cells in vitro and exhibits anti-tumor activity in acute myeloid leukemia and B lymphoma xenograft models. In this study we investigated the anti-myeloma activity of TTI-621 as both a single agent and in combination with bortezomib or carfilzomib, two proteasome inhibitors that are approved for use in MM patients. The ability of TTI-621 to trigger macrophage phagocytosis of MM cells was assessed using a flow cytometry-based phagocytosis assay. Blockade of CD47 using TTI-621 effectively triggered macrophage-mediated phagocytosis of MM cells, and this anti-tumor effect was significantly enhanced by pre-treatment of MM cells with bortezomib or carfilzomib. In order to understand the molecular mechanism behind this enhanced phagocytic effect, we performed immunophenotyping of the tumor cells and observed an upregulation of pro-phagocytic “eat” signals on the tumor cell surface that potentially augment the phagocytic response. To investigate whether CD47 blockade in the context of proteasome inhibition translates to enhanced anti-tumor activity in vivo, we employed a MM xenograft model. NOD.SCID mice were subcutaneously engrafted with human MM cells followed by treatment with TTI-621, in the absence or presence of concurrent administration of a proteasome inhibitor. As monotherapies, both TTI-621 and the proteasome inhibitor reduced tumor burden relative to vehicle controls. Moreover, the combination of CD47 blockade and proteasome inhibition resulted in a greater reduction in tumor growth as compared to the two drugs alone. In conclusion, these data demonstrate that TTI-621 exhibits anti-myeloma activity that is further enhanced by combination with bortezomib or carfilzomib. TTI-621 monotherapy is currently being evaluated in a Phase 1b study in patients with MM and other hematological malignancies (NCT02663518). These data provide a rationale to evaluate a combination study of TTI-621 and a proteasome inhibitor in MM patients.

Citation Format: Emma Linderoth, Simone Helke, Vivian Lee, Tapfuma Mutukura, Mark Wong, Gloria H. Lin, Lisa D. Johnson, Xinli Pang, Jeff Winston, Penka S. Petrova, Robert A. Uger, Natasja N. Viller. The anti-myeloma activity of TTI-621 (SIRPαFc), a CD47-blocking immunotherapeutic, is enhanced when combined with a proteasome inhibitor [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2653. doi:10.1158/1538-7445.AM2017-2653

Abstract 2646: Intratumoral delivery of TTI-621 (SIRPαFc), a CD47-blocking immunotherapeutic, inhibits tumor growth and prolongs animal survival in a subcutaneous B cell lymphoma model

Tumor cells often evade macrophage-mediated destruction by increasing cell surface expression of CD47, which delivers an anti-phagocytic (“do-not-eat”) signal by binding the inhibitory signal-regulatory protein α (SIRPα) receptor on macrophages. We have previously shown that blockade of the CD47-SIRPα pathway using TTI-621, a soluble SIRPα-IgG1 Fc fusion protein, triggers macrophage phagocytosis of tumor cells in vitro as well as inhibits tumor growth in vivo when delivered systemically. In the current study, the efficacy of intratumoral delivery of TTI-621 was evaluated in a subcutaneous diffuse large B-cell lymphoma (Toledo) xenograft model.

Tumor bearing mice were randomized into treatment groups when tumor volumes reached approximately 120 mm3. Weekly intratumoral administration of TTI-621 at 10, 1 and 0.1 mg/kg dose levels resulted in statistically significant decreases in tumor growth and improved survival relative to vehicle control treatment. Notably, at day 50 post-tumor implantation 100% survival was achieved at the highest dose level (vs. 0% survival with vehicle control treatment). Moreover, weekly intratumoral administration of TTI-621 was efficacious even at a high tumor load setting in which the pre-dose volumes were approximately 300 mm3. Flow cytometry analysis of the dissociated tumor samples demonstrated no significant change in the numbers of M1 and M2 tumor-associated macrophages (TAMs) following intratumoral administration of TTI-621. Nevertheless, TTI-621 dramatically increased the phagocytosis of Toledo cells by both M1 and M2 TAMs to a similar extent ex vivo, suggesting that TTI-621 is efficacious in increasing the phagocytosis of tumor cells by a heterogeneous population of TAMs.

Collectively, these results demonstrate that TTI-621 is efficacious when delivered intratumorally and can increase the phagocytosis of tumor cells by both M1 and M2 TAM populations. These data support the evaluation of intratumoral administration of TTI-621 in cancer patients, and a Phase I study of intratumorally delivered TTI-621 in patients with percutaneously accessible solid tumors and mycosis fungoides is ongoing (NCT02890368).

Citation Format: Gloria H. Lin, Marilyse Charbonneau, Vien Chai, Alison M. O'Connor, Bolette Bossen, Hui Chen, Mark Wong, Natasja N. Viller, Emma Linderoth, Lisa D. Johnson, Xinli Pang, Jeffery Winston, Penka S. Petrova, Robert A. Uger. Intratumoral delivery of TTI-621 (SIRPαFc), a CD47-blocking immunotherapeutic, inhibits tumor growth and prolongs animal survival in a subcutaneous B cell lymphoma model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2646. doi:10.1158/1538-7445.AM2017-2646

TTI-621 (SIRPαFc): A CD47-Blocking Innate Immune Checkpoint Inhibitor with Broad Antitumor Activity and Minimal Erythrocyte Binding

Purpose: The ubiquitously expressed transmembrane glycoprotein CD47 delivers an anti-phagocytic (do not eat) signal by binding signal-regulatory protein α (SIRPα) on macrophages. CD47 is overexpressed in cancer cells and its expression is associated with poor clinical outcomes. TTI-621 (SIRPαFc) is a fully human recombinant fusion protein that blocks the CD47-SIRPα axis by binding to human CD47 and enhancing phagocytosis of malignant cells. Blockade of this inhibitory axis using TTI-621 has emerged as a promising therapeutic strategy to promote tumor cell eradication.Experimental Design: The ability of TTI-621 to promote macrophage-mediated phagocytosis of human tumor cells was assessed using both confocal microscopy and flow cytometry. In vivo antitumor efficacy was evaluated in xenograft and syngeneic models and the role of the Fc region in antitumor activity was evaluated using SIRPαFc constructs with different Fc tails.Results: TTI-621 enhanced macrophage-mediated phagocytosis of both hematologic and solid tumor cells, while sparing normal cells. In vivo, TTI-621 effectively controlled the growth of aggressive AML and B lymphoma xenografts and was efficacious in a syngeneic B lymphoma model. The IgG1 Fc tail of TTI-621 plays a critical role in its antitumor activity, presumably by engaging activating Fcγ receptors on macrophages. Finally, TTI-621 exhibits minimal binding to human erythrocytes, thereby differentiating it from CD47 blocking antibodies.Conclusions: These data indicate that TTI-621 is active across a broad range of human tumors. These results further establish CD47 as a critical regulator of innate immune surveillance and form the basis for clinical development of TTI-621 in multiple oncology indications. Clin Cancer Res; 23(4); 1068-79. ©2016 AACR.

Abstract B028: Blockade of the CD47 “Do not eat” signal by TTI-621 (SIRPαFc) leads to enhanced antitumor CD8+ T cell responses in vitro

High expression of the CD47 “do-not-eat” signal is a mechanism commonly used by tumor cells to escape phagocytosis by macrophages. CD47 transmits an inhibitory signal upon binding to its receptor signal-regulatory protein α (SIRPα) on the surface of macrophages. We have previously shown that TTI-621, a soluble SIRPαFc fusion protein, neutralizes the suppressive effects of CD47 and triggers macrophage-mediated phagocytosis of tumor cells in vitro, and effectively controls tumor growth in vivo. Using a human culture system, we investigated whether this increase in macrophage-mediated phagocytosis results in augmented T cell responses.

To evaluate the T cell response to a model tumor antigen, Jurkat, a human leukemia cell line, was stably transfected with a construct containing the human cytomegalovirus phosphoprotein pp65 (CMV-Jurkat). Consistent with our previous studies, blockade of CD47 on CMV-Jurkat cells using TTI-621 led to a dramatic increase in tumor cell phagocytosis by primary macrophages derived from peripheral blood monocytes of healthy, HLA-A2+ donors. Using a high-affinity soluble TCR multimer that specifically recognizes an immunodominant epitope from pp65 complexed with HLA-A2, we found that TTI-621-mediated phagocytosis of CMV-Jurkat resulted in increased pp65 antigen presentation on the surface of macrophages. In cultures treated with a control Fc fragment, where macrophages only exhibited a low level of phagocytosis, no presentation of pp65 peptide could be detected. Moreover, mock-transfected tumor cells were efficiently phagocytosed in the presence of TTI-621, yet did not result in presentation of CMV pp65 peptide.

To assess whether this increase in antigen presentation results in augmented T cell responses, macrophages from the phagocytosis assay were co-cultured with autologous CD8+ T cells for five days. We observed robust proliferation of CMV pp65-specific CD8+ T cells following co-culture with macrophages that had phagocytosed CMV-Jurkat in the presence of TTI-621 compared to control Fc treatment. In contrast, no proliferation of CMV pp65-specific CD8+ T cells occurred when macrophages had phagocytosed mock-transfected tumor cells, suggesting that the proliferation of CMV-specific CD8+ T cells is a tumor antigen-specific response. In addition, preliminary data indicate that primed CMV-specific CD8+ T cells are fully functional and are capable of exhibiting cytotoxicity against CMV-Jurkat.

Collectively, our study demonstrates for the first time that in a human culture system, blockade of the CD47 “do not eat” signal results in increased phagocytosis, augmented tumor antigen presentation and enhanced anti-tumor CD8+ T cell responses. These results provide further support for the concept that CD47 lies at the intersection of the innate and adaptive immune systems. TTI-621, which is currently in a Phase I trial in patients with advanced hematological malignancies (NCT02663518), may thus be able to harness the anti-tumor activity of both macrophages and T cells.

Citation Format: Natasja Nielsen Viller, Tran Truong, Emma Linderoth, Lisa D. Johnson, Stephane Viau, Gloria H. Y. Lin, Mark Wong, Xinli Pang, Penka S. Petrova, Robert A. Uger. Blockade of the CD47 “Do not eat” signal by TTI-621 (SIRPαFc) leads to enhanced antitumor CD8+ T cell responses in vitro [abstract]. In: Proceedings of the Second CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; 2016 Sept 25-28; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(11 Suppl):Abstract nr B028.

Abstract 2345: SIRPαFc, a CD47-blocking cancer immunotherapeutic, triggers phagocytosis of lymphoma cells by both classically (M1) and alternatively (M2) activated macrophages

Macrophages are characterized by their heterogeneity and plasticity in response to the microenvironment. Although macrophages have the capacity to phagocytose cancer cells that express pro-phagocytic signals, tumor cells often evade macrophage-mediated destruction by increased cell surface expression of CD47, which delivers an anti-phagocytic (“do not eat”) signal by binding the inhibitory signal-regulatory protein α (SIRPα) receptor on the surface of macrophages. We have previously shown that soluble SIRPα-Fc fusion protein (SIRPαFc) neutralizes the suppressive effects of CD47 and promotes macrophage-mediated phagocytosis of tumor cells both in vitro and in vivo. In an attempt to recapitulate the functional and phenotypic heterogeneity of tumor infiltrating macrophages, we have examined the ability of SIRPαFc to trigger phagocytosis of lymphoma cells by six distinctly polarized macrophage populations.

We generated human monocyte-derived macrophages (MDMs) and polarized them into M0, M1, M2a, M2b and M2c subsets. These MDMs varied greatly in their expression of myeloid surface markers including CD14, CD11b, CD80, CD86, HLA-DR, CD206, CD200R and CD163; as well as in expression of the Fc gamma receptors (FcγRs) CD16, CD32 and CD64. Next, the ability of SIRPαFc to trigger MDM phagocytosis of lymphoma cells was examined using a flow cytometry-based assay. Blockade of CD47 on the tumor cells using SIRPαFc dramatically increased phagocytosis of tumor cells by all subsets, with M1 and M2c MDMs being superior at phagocytosis. Moreover, we found that M0, M2a and M2b MDMs, which exhibited slightly lower phagocytic capabilities, were remarkably plastic in nature and could readily be re-polarized into highly phagocytic MDMs using a variety of agents. This suggests that SIRPαFc will be efficacious in triggering the destruction of cancer cells by the diverse population of MDMs found in vivo.

To further understand what drives the phagocytic capacity of polarized MDMs, we analyzed FcγR expression and observed a positive correlation between MDM expression of the high-affinity FcγRI (CD64) and phagocytic activity following SIRPαFc treatment. Moreover, re-polarization of M0, M2a and M2b MDMs resulted in upregulation of FcγRs and enhanced tumor cell phagocytosis. Finally, by individually blocking CD16, CD32 and CD64 on MDMs prior to the phagocytosis assay, we found that the low-affinity FcγRs CD16 and CD32 also contribute to SIRPαFc-mediated phagocytosis of lymphoma cells.

In conclusion, SIRPαFc triggered phagocytosis of lymphoma cells by a diverse panel of polarized MDMs, which required MDM expression of FcγRs. These data support the evaluation of SIRPαFc in cancer patients and a clinical study of SIRPαFc in patients with lymphoma and other hematological malignancies is currently in progress.

Citation Format: Gloria H. Y. Lin, Vien Chai, Vivian Lee, Karen Dodge, Tran Truong, Mark Wong, Lisa D. S. Johnson, Xinli Pang, Penka S. Petrova, Robert A. Uger, Natasja N. Viller. SIRPαFc, a CD47-blocking cancer immunotherapeutic, triggers phagocytosis of lymphoma cells by both classically (M1) and alternatively (M2) activated macrophages. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2345.

Bax/Bak activation in the absence of Bid, Bim, Puma, and p53

How BH3-only proteins activate Bax/Bak, the two gateway proteins of the mitochondria-dependent apoptotic pathway, remains incompletely understood. Although all pro-apoptotic BH3-only proteins are known to bind/neutralize the anti-apoptotic Bcl-2 proteins, the three most potent ones, Bid (tBid), Bim, and Puma, possess an additional activity of directly activating Bax/Bak in vitro. This latter activity has been proposed to be responsible for triggering Bax/Bak activation following apoptotic stimulation. To test this hypothesis, we generated Bid^−/−Bim^−/−Puma^−/− (TKO), TKO/Bax^−/−/Bak^−/− (PentaKO), and PentaKO/Mcl-1^−/− (HexaKO) HCT116 cells through gene editing. Surprisingly, although the TKO cells were resistant to several apoptotic stimuli, robust apoptosis was induced upon the simultaneous inactivation of Bcl-xL and Mcl-1, two anti-apoptotic Bcl-2 proteins known to suppress Bax/Bak activation and activity. Importantly, such apoptotic activity was completely abolished in the PentaKO cells. In addition, ABT-737, a BH3 mimetic that inhibits Bcl-xL/Bcl-w/Bcl-2, induced Bax activation in HexaKO cells reconstituted with endogenous level of GFP-Bax. Further, by generating TKO/p53^−/− (QKO) cells, we demonstrated that p53, a tumor suppressor postulated to directly activate Bax, is not required for Bid/Bim/Puma-independent Bax/Bak activation. Together, these results strongly suggest that the direct activation activities of Bid (tBid), Bim, Puma, and p53 are not essential for activating Bax/Bak once the anti-apoptotic Bcl-2 proteins are neutralized.

Strategy of STAT3β cell-specific expression in macrophages exhibits antitumor effects on mouse breast cancer

Recent studies underscore the importance of crosstalk between tumor-associated macrophages (TAMs) and tumor cells in cancer progression and metastasis. In our study, AdCD68STAT3β, a recombinant adenovirus containing a STAT3β gene driven by CD68 macrophage-specific promoter, was used to suppress STAT3 and the downstream signaling pathways in TAMs. The results showed that STAT3β gene under the control of CD68 macrophage-specific promoter was only expressed in macrophages, which significantly inhibited the motility and invasion of breast cancer cells when co-cultured with 4T1 cells. Moreover, cell-specific STAT3β expression in TAMs extended survival of tumor-bearing mice and suppressed breast tumor growth, angiogenesis and metastasis, by regulating the crosstalk between tumor cells and TAMs. Therefore, our study provided a novel strategy for the antitumor effects of STAT3β.

Abstract 4271: Lack of CD47 membrane mobility contributes to the poor erythrocyte binding of SIRPαFc, a novel CD47-blocking cancer immunotherapeutic

CD47 binds to SIRPα on the surface of macrophages and delivers a “do not eat” signal that suppresses phagocytosis. There is strong evidence that many liquid and solid tumors exploit the CD47-SIRPα pathway to escape macrophage-mediated destruction. Blockade of CD47 using a soluble SIRPα-Fc fusion protein (SIRPαFc) has emerged as a promising strategy to neutralize the suppressive effects of CD47 and promote the eradication of tumor cells. We have previously reported data demonstrating that human SIRPαFc binds strongly to tumor cells but very poorly to human red blood cells (RBCs), despite abundant surface expression of CD47 on RBCs and strong reactivity with CD47-specific antibodies. Here we expand upon these early findings and assess inter-species differences in RBC binding.

Our results, based on a panel of 43 human donors, clearly show that SIRPαFc binds very poorly to human RBCs regardless of gender, ABO blood group or Rh antigen status. Consistent with this finding, SIRPαFc was unable to induce agglutination of RBCs in vitro, although hemagglutination was triggered by CD47-blocking antibodies. Curiously, although the binding affinity of human SIRPαFc to cynomolgus macaque CD47 is approximately 10-fold lower than the binding to the human target, it binds strongly to cyno RBCs. This indicates that affinity alone does not predict the ability to bind erythrocytes. Instead, we hypothesized that the mobility of CD47 in the RBC membrane is a key determinant of SIRPαFc binding and thus compared the detergent solubilization profile of CD47 in human and cyno RBCs. CD47 was observed to segregate largely into the detergent-soluble fraction in monkey erythrocytes but was localized primarily to the insoluble pellet fraction in human RBCs, suggesting greater membrane mobility in cyno compared to human RBCs. This finding is consistent with a model in which CD47 mobility is required to form high affinity clusters with SIRPαFc, and indeed we have previously observed that pre-clustering CD47 with a non-blocking antibody converts human RBCs into strong SIRPαFc binders. Finally, the consequences of cyno RBC binding were assessed in vivo. Significant depletion of RBCs was evident following intravenous infusions of SIRPαFc in cyno monkeys. We speculate that similar anemia is likely to occur in humans treated with CD47-blocking antibodies that bind to human erythrocytes, but not with a low RBC-binding SIRPαFc therapeutic.

In conclusion, human SIRPαFc binds very poorly to human RBCs but is highly reactive with cyno erythrocytes. This unusual pattern of species cross-reactivity may result from species-specific differences in CD47 membrane mobility and is consistent with a model in which SIRPαFc binding requires mobile CD47 to form high affinity clusters. We predict that anemia, which occurs in monkeys following SIRPαFc administration, is not likely to occur in human patients where significant RBC binding is absent.

Citation Format: Penka S. Petrova, Karen Dodge, Tanya Prasolava, Vien Chai, Xinli Pang, Robert A. Uger. Lack of CD47 membrane mobility contributes to the poor erythrocyte binding of SIRPαFc, a novel CD47-blocking cancer immunotherapeutic. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4271. doi:10.1158/1538-7445.AM2015-4271

Advances in non-peptidomimetic HIV protease inhibitors

HIV protease plays a crucial role in the viral life cycle. It can cleave a series of heptamers in the viral Gag and GagPol precursor proteins to generate mature infectious virus particles. Successful inhibition of the protease will prevent this maturation step and hence block the spreading of HIV. However, the rapid emergence of drug resistance makes it urgent to develop new HIV protease inhibitors to combat the global disease. Besides, poor oral bioavailability, unacceptable side effects, high treatment cost and pill burden also trouble the application of HIV protease inhibitors. In such situations, non-peptidomimetic HIV protease inhibitors have drawn an increasing interest as a potential therapeutic option due to their small molecular weight, favorable bioavailability, high stability in vivo, low resistance and cost of production. In this review, we present the recent advances in non-peptidomimetic HIV protease inhibitors. Their design strategies, biological activities, resistance profiles, as well as clinical application will also be discussed.

Abstract 5011: Cancer immunotherapy targeting CD47: Wild type SIRPαFc is the ideal CD47-blocking agent to minimize unwanted erythrocyte binding

Background: CD47 binds to SIRPα on the surface of macrophages and delivers a “do not eat” signal that suppresses phagocytosis. There is strong evidence that many hematopoietic and solid tumors exploit the CD47-SIRPα pathway to escape macrophage-mediated destruction, and blocking CD47 has emerged as a promising cancer immunotherapy. There are several approaches available to achieve CD47 blockade, including wild type SIRPαFc fusion proteins, engineered high affinity SIRPαFcs and monoclonal antibodies. One concern with CD47-based therapies is the expression of the target on the surface of red blood cells (RBCs), which has the potential to act as a large antigen sink and cause hematological toxicity. Indeed, anemia has been reported in animals treated with high affinity SIRPαFcs variants and CD47-specific antibodies.

Methods: Various CD47-specific biologics, including SIRPαFc fusion proteins containing wild type or mutant SIRPα sequences and CD47-specific antibodies were evaluated for binding to erythrocytes and other cell types by flow cytometry.

Results: SIRPαFc fusion proteins containing wild type SIRPα sequences, which bind to CD47 with nanomolar affinity, bound very poorly to human RBCs compared to both blocking and non-blocking CD47 antibodies. This striking difference was highly reproducible and occurred across different blood types, but was not seen with other cells (e.g., tumor cell lines), indicating an erythrocyte-specific phenomenon. The presence of wild type SIRPα sequences was critical to achieving a low RBC binding profile, as mutated SIRPαFc with enhanced CD47 affinity bound strongly to human erythrocytes. Interestingly, wild type SIRPαFc binding to human RBCs was dramatically increased when CD47 was first clustered with a non-blocking antibody, suggesting that wild type SIRPαFc normally lacks the ability to aggregate CD47 on the erythrocyte surface. Finally, the lack of appreciable SIRPαFc binding to erythrocytes is unique to humans, as non-mutated mouse SIRPαFc could bind mouse RBCs and wild type human SIRPαFc cross reacts with CD47 on the surface of non-human primate and porcine RBCs.

Conclusions: Wild type SIRPαFc, unlike other CD47 blocking agents, exhibits very low binding to human erythrocytes. This predicts that wild type SIRPαFc will have superior pharmacokinetic properties and less toxicity in cancer patients. Furthermore, the strong binding of wild type SIRPαFc to monkey RBCs suggests that preclinical studies in non-human primates may overestimate the risk of hematological toxicity in humans.

Citation Format: Robert A. Uger, Karen Dodge, Xinli Pang, Penka S. Petrova. Cancer immunotherapy targeting CD47: Wild type SIRPαFc is the ideal CD47-blocking agent to minimize unwanted erythrocyte binding. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5011. doi:10.1158/1538-7445.AM2014-5011