Abstract 3295: The Nanoprimer: A nanoparticle designed to the efficacy of nucleic acid-based therapeutics in oncology

Nucleic acid drugs have shown promise in oncology, however their use is limited by hepatic clearance. Due to the mononuclear phagocytic system (MPS), a large part of the intravenously-administered dose does not reach the therapeutic target. Our approach aims to address this issue using biocompatible nanoparticles—the Nanoprimer—that is administered prior to the therapeutic. Due to its physico-chemical properties, the Nanoprimer is transiently internalized by Kupffer cells (KC), and endothelial cells of the MPS, enabling temporary reduction of hepatic clearance. These data further explore the Nanoprimer’s mechanism of action and demonstrate that scavenger receptor-A (SR) is the main receptor involved in Nanoprimer binding and uptake by KC. Efficacy studies in mouse model show that the Nanoprimer dramatically increases the anti-tumor efficacy of nucleic acid-based treatment without introducing additional toxicities. An in vitro toxicity evaluation was performed investigating the Nanoprimer’s hemolytic properties and its potential ability to activate the complement system, platelet aggregation and pro-inflammatory cytokines*. SR-mediated binding and uptake of Nanoprimer by KC were assessed using a competitive binding assay with SR inhibitor polyinosinic acid. The impact of the Nanoprimer on anti-tumor efficacy was evaluated on orthotopic triple negative breast cancer (TNBC) model in combination with siRNA-loaded lipid nanoparticles (LNPs) targeting a novel cancer-specific gene transcript of a master regulator of invadopodia formation and Wnt, Hedgehog and Notch oncogenic pathways. Results showed that the Nanoprimer is safe at the effective dose. The Nanoprimer does not activate the complement components, induce hemolysis, platelet aggregation, or cytokine storm syndrome elements. The competitive inhibition of SR-A decreases Nanoprimer binding and KC-uptake by 70%, indicating SR-A selective uptake of the Nanoprimer by macrophages. The efficacy study shows that combining the Nanoprimer with siRNA LNP therapy significantly increased treatment efficiency, with a mean tumor growth inhibition ratio of 36.3% for LNPs alone versus 84.6% for the combination. Moreover, the combination therapy more efficiently prevents the development of pulmonary metastatic tumors, with a metastasis-inhibition rate of 98%. These data demonstrate the safety of the Nanoprimer, along with its ability to maximize the inhibition of primary tumor growth and pulmonary metastasis by systemic siRNA LNP therapy in a TNBC mouse model. They also highlight the capacity of Nanoprimer technology to unlock the potential of nucleic acid-based treatments. The ubiquitous nature of its mode of action allows its application to a broad spectrum of anti-cancer therapeutics. *we acknowledge NCL, Frederick National Laboratory for Cancer Research sponsored by the NCI for the help with conducting these experiments

Citation Format: Julie Devallière, Laurence Poul, Maxime Bergère, Audrey Darmon, Océane Jibault, Francis Mpambani, Kelvin Tsai, Matthieu Germain. The Nanoprimer: A nanoparticle designed to the efficacy of nucleic acid-based therapeutics in oncology [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3295.

Radiotherapy-activated NBTXR3 nanoparticles modulate cancer cell immunogenicity and TCR repertoire

Background

Radiotherapy is a powerful and widely used technique for the treatment of solid tumors. Beyond its ability to destroy tumor cells, it has been demonstrated that radiotherapy can stimulate the anti-tumor immune response. Unfortunately, this effect is mainly restricted to the irradiated lesion, as tumor control outside the treated field (called the ‘abscopal effect’) is rarely obtained. In addition, many pro-tumoral factors prevent this anti-tumor immune response from being sustained and efficient. We previously reported that radiotherapy-activated NBTXR3 produced a significant CD8-dependent abscopal effect in immunocompetent mice bearing CT26.WT tumors, while radiotherapy failed to generate such a response.

Methods

To identify the mechanisms that may explain this response, we evaluated the capacity of radiotherapy-activated NBTXR3 to modulate the immunogenicity of tumor cells by analysis of immunogenic cell death biomarkers and immunopeptidome sequencing. In vivo, we analyzed treated tumors for CD4+, CD8 + and CD68 + cell infiltrates by immunohistochemistry and digital pathology and sequenced the T cell receptor (TCR) repertoire in both treated and untreated distant tumors.

Results

We showed that NBTXR3 activated by radiotherapy both increased immunogenic cell death biomarkers and modulated the immunopeptidome profile of CT26.WT cells. Immunohistochemistry analysis of treated tumors revealed a significant increase in CD4+, CD8 + and CD68 + cell infiltrates for NBTXR3 activated by radiotherapy group, compared to radiotherapy. We also measured significant modifications in TCR repertoire diversity in the radiotherapy-activated NBTXR3 group, both in treated and distant untreated tumors, compared to radiotherapy alone.

Conclusions

These results indicate that radiotherapy-activated NBTXR3 can act as an effective immunomodulator, modifying tumor cell immunogenicity and impacting the lymphocyte population.

Graphical Abstract

740 Radiotherapy-activated NBTXR3 nanoparticles Increase CD8+ T cell infiltration and diversity in tumors, and modulate the immunopeptidome of cancer cells

Background

When exposed to radiotherapy (RT), NBTXR3 nanoparticles increase radiation dose deposition from within the cancer cells. NBTXR3 is intended for a single intratumor injection. Results from a phase II/III clinical trial in patients with locally advanced Soft Tissue Sarcoma demonstrated significant superiority and clinical benefits of NBTXR3 activated by RT compared to RT alone, and was well tolerated. NBTXR3 is currently being evaluated in several other tumors including head and neck, liver, and pancreatic cancer as a single agent or in combination with anti-PD1. Moreover, preclinical studies have demonstrated that NBTXR3 can produce a significant abscopal effect, whereas RT alone cannot. Here, we explored the impact of NBTXR3 activated by RT on CD8+ infiltrates and TcR repertoire diversity change, and the effect on the immunopeptidome of cancer cells.

Methods

CT26 (murine colorectal cancer cells) were subcutaneously injected in BALB/c mice in one flank. Then, tumors were intratumorally injected with NBTXR3 (or vehicle) and irradiated 24 hours later with 4Gy per fraction for 3 consecutive days. Tumors were collected 3 days after the last RT fraction and immune cell infiltrates were measured using immunohistochemistry (IHC) and digital pathology. For TcR repertoire sequencing, the same workflow was followed, except cells were injected in both flanks. Only right tumors received treatment, while left tumors remained untreated. For immunopeptidome analysis, in vitro cells were irradiated by 4Gy. After one day, cells were collected for isolation and sequencing of MHC I-loaded peptides.

Results

IHC analyses showed a significant increase of CD8+ T cell infiltrates in tumors of mice treated with NBTXR3+RT, while RT alone had no significant effect. In addition, NBTXR3+RT treatment was able to increase TcR repertoire diversity, both in treated and untreated tumors, compared to RT alone. Finally, analysis of immunopeptidome showed that NBTXR3+RT changed the profile of MHC-I-loaded peptides.

Conclusions

Our in vivo data indicate that NBTXR3+RT can modulate the microenvironment of treated tumors, leading to enhanced CD8+ T cell infiltration as well as modification of the TcR repertoire, both in treated and distant untreated tumors. These NBTXR3+RT-induced responses may be related to changes in the immunopeptidome of cancer cells triggered by this treatment.

NBTXR3 Radiotherapy-Activated Functionalized Hafnium Oxide Nanoparticles Show Efficient Antitumor Effects Across a Large Panel of Human Cancer Models

PURPOSE

The side effects of radiotherapy induced on healthy tissue limit its use. To overcome this issue and fully exploit the potential of radiotherapy to treat cancers, the first-in-class radioenhancer NBTXR3 (functionalized hafnium oxide nanoparticles) has been designed to amplify the effects of radiotherapy.

PATIENTS AND METHODS

Thanks to its physical mode of action, NBTXR3 has the potential to be used to treat any type of solid tumor. Here we demonstrate that NBTXR3 can be used to treat a wide variety of solid cancers. For this, we evaluated different parameters on a large panel of human cancer models, such as nanoparticle endocytosis, in vitro cell death induction, dispersion, and retention of NBTXR3 in the tumor tissue and tumor growth control.

RESULTS

Whatever the model considered, we show that NBTXR3 was internalized by cancer cells and persisted within the tumors throughout radiotherapy treatment. NBTXR3 activated by radiotherapy was also more effective in destroying cancer cells and in controlling tumor growth than radiotherapy alone. Beyond the effects of NBTXR3 as single agent, we show that the antitumor efficacy of cisplatin-based chemoradiotherapy treatment was improved when combined with NBTXR3.

CONCLUSION

These data support that NBTXR3 could be universally used to treat solid cancers when radiotherapy is indicated, opening promising new therapeutic perspectives of treatment for the benefit of many patients.

Abstract 2871: The Nanoprimer: a nanoparticle designed to transiently occupy the mononuclear phagocytic system in order to increase nanomedicine-based treatments efficacy

Introduction: Most nanomedicines are currently limited in their efficacy due to a sub-optimal biodistribution/accumulation in the target tissues. A large part of the administered dose remains useless due to the high rate of clearance by the mononuclear phagocytic system (mainly by Kupffer cells in liver). We designed a new approach based on the use of an engineered, biocompatible nanoparticle–the Nanoprimer–that is administered before the nanomedicine in order to transiently and specifically occupy the liver clearance pathways responsible for sub-optimal therapeutic bioavailability. The Nanoprimer's effect is only based on its specific physico-chemical properties, there is no active principal ingredient encapsulated in it. Here we demonstrate the ability of the Nanoprimer to redefine the bioavailability and efficacy of nanomedicines loaded with small molecules or nucleic acid. We evaluated the biodistribution and the safety of the Nanoprimer alone and of an irinotecan loaded liposome combined with the Nanoprimer.

Methods: Quantitative evaluation of the Nanoprimer's biodistribution was performed by mass spectrometry. Safety profile of the Nanoprimer was evaluated in vitro (cell viability, cytokines/interleukins expression profile, complement activation, phagoburst and phagotest on different cell lines) and in vivo, in mice, by a follow up of body weight and clinical signs, histological observations of liver, spleen and lungs and blood parameters titration, after the injection of a maximized dose of Nanoprimer. The impact of the Nanoprimer on the bioavailability and biodistribution of nanomedicines loaded with irinotecan or nucleic acids (mRNA / SiRNA) was evaluated by HPLC and fluorescence quantification, respectively. Finally, the impact of the Nanoprimer on treatment was evaluated using nanomedicines encapsulating human erythropoietin (hEPO) mRNA, Factor VII (FVII) siRNA or irinotecan.

Results: The Nanoprimer presents a rapid accumulation within liver and spleen. The Nanoprimer was well tolerated with no sign of toxicity observed using therapeutic dosage. The administration of the Nanoprimer increases systemic bioavailability of different type of nanomedicines and enhances their accumulation in target tissues. This improved bioavailability is correlated with an increased secretion of hEPO by 30%, for mRNA-loaded nanomedicines, an increased silencing of FVII by 50%, for siRNA-loaded nanomedicines, and an increased anti-tumor efficacy by 50%, for irinotecan-loaded nanomedicines.

Here, we showed the safe profile of the Nanoprimer and its ability to increase the treatment outcomes for different nature of nanomedicines. The separation of the functions ensuring the efficacy of a treatment into two distinct objects opens perspectives for designing future nanomedicines and a shift in the therapeutic paradigm.

Citation Format: Julie Devalliere, Laurence Poul, Audrey Darmon, Oceane Jibault, Maxime Bergere, Francis Mpambani, Nell Saunders, Marion Paolini, Robert Langer, Matthieu Germain. The Nanoprimer: a nanoparticle designed to transiently occupy the mononuclear phagocytic system in order to increase nanomedicine-based treatments efficacy [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 2871.

Clinical characteristics and outcomes of COMPASS eligible patients in France. An analysis from the REACH Registry

BACKGROUND

Following the publication of the COMPASS trial, the European Medicines Agency has approved a regimen of combination of rivaroxaban 2.5mg twice daily and a daily dose of 75-100mg acetylsalicylic acid (ASA) for patients with coronary artery disease (CAD) or symptomatic peripheral artery disease (PAD) at high risk of ischemic events. However, the applicability of such a therapeutic strategy in France is currently unknown.

AIMS

To describe the proportion of patients eligible to COMPASS in France, their baseline clinical characteristics and the rate of major adverse cardiovascular events, using the REACH registry.

METHODS

From the the REduction of Atherothrombosis for Continued Health (REACH) registry database, a large international registry of patients with, or at risk, of atherothrombosis, we analyzed patients included in France with either established CAD and/or PAD and fulfilling the inclusion and exclusion criteria of the COMPASS trial. The ischemic outcome was a composite of cardiovascular (CV) death, myocardial infarction (MI), or stroke, and serious bleeding were defined as haemorrhagic stroke or bleeding leading to hospitalization or transfusion.

RESULTS

Among more than 65000 patients enrolled in REACH, 2.012 patients were evaluable and enrolled in France. Among them, 1194 patients (59.3%) were eligible to COMPASS. The main reasons for exclusion of the COMPASS trial, were high bleeding risk (59.1%), anticoagulant use (43.4%), requirement for dual antiplatelet therapy within 1 year of an ACS or PCI (24.7%). In the "COMPASS eligible population", the rate of MACE (CV, MI and stroke) at 4 years follow-up was 13.4% [11.3-15.8], and serious bleeding was 2.5% at 4 years [1.6-3.4]. Patients with polyvascular disease (n=219) had the highest rate of MACE, compared with patients with CAD only and PAD only (19.1% [13.9-26.1] vs. 11.6% [9.1-14.8] vs 13.2% [9.2-18.8], P<0.0001, respectively).

CONCLUSION

The COMPASS therapeutic strategy in France appears to be applicable to more than half of CAD or PAD patients. This population appears at high residual risk of atherothrombotic events, and patients with polyvascular disease experienced the highest rate of events.

A Nanoprimer To Improve the Systemic Delivery of siRNA and mRNA

Despite tremendous interest in gene therapies, the systemic delivery of nucleic acids still faces substantial challenges. To successfully administer nucleic acids, one approach is to encapsulate them in lipid nanoparticles (LNPs). However, LNPs administered intravenously substantially accumulate in the liver where they are taken up by the reticuloendothelial system (RES). Here, we administer prior to the LNPs a liposome designed to transiently occupy liver cells, the Nanoprimer. This study demonstrates that the pretreatment of mice with the Nanoprimer decreases the LNPs' uptake by the RES. By accumulating rapidly in the liver cells, the Nanoprimer improves the bioavailability of the LNPs encapsulating human erythropoietin (hEPO) mRNA or factor VII (FVII) siRNA, leading respectively to more hEPO production (by 32%) or FVII silencing (by 49%). The use of the Nanoprimer offers a new strategy to improve the systemic delivery of RNA-based therapeutics.

Radiotherapy-Activated Hafnium Oxide Nanoparticles Produce Abscopal Effect in a Mouse Colorectal Cancer Model

Purpose

Despite tremendous results achieved by immune checkpoint inhibitors, most patients are not responders, mainly because of the lack of a pre-existing anti-tumor immune response. Thus, solutions to efficiently prime this immune response are currently under intensive investigations. Radiotherapy elicits cancer cell death, generating an antitumor-specific T cell response, turning tumors in personalized in situ vaccines, with potentially systemic effects (abscopal effect). Nonetheless, clinical evidence of sustained anti-tumor immunity as abscopal effect are rare.

Methods

Hafnium oxide nanoparticles (NBTXR3) have been designed to increase energy dose deposit within cancer cells. We examined the effect of radiotherapy-activated NBTXR3 on anti-tumor immune response activation and abscopal effect production using a mouse colorectal cancer model.

Results

We demonstrate that radiotherapy-activated NBTXR3 kill more cancer cells than radiotherapy alone, significantly increase immune cell infiltrates both in treated and in untreated distant tumors, generating an abscopal effect dependent on CD8+ lymphocyte T cells.

Conclusion

These data show that radiotherapy-activated NBTXR3 could increase local and distant tumor control through immune system priming. Our results may have important implications for immunotherapeutic agent combination with radiotherapy.

3294Frequency, management and outcomes of patients with stable coronary artery disease eligible for COMPASS. An analysis of the CLARIFY registry

Background

The COMPASS trial demonstrated that a combination of rivaroxaban and aspirin improved cardiovascular (CV) outcomes in high-risk patients with either peripheral artery disease (PAD) or stable coronary artery disease (CAD) compared with aspirin alone, at the price of increased bleeding. A previous analysis of the REACH Registry reported an eligibility rate of 52.9% within a population with stable vascular disease. However, most of cardiologists actually treat patients with stable CAD, rather than PAD. Data regarding eligibility to COMPASS in CAD patients from real life practice are scarce.

Purpose

We aimed to describe the proportion of patients eligible to COMPASS within the CLARIFY Registry. Additionally, we aimed to describe their management and outcomes, comparing patients excluded from the trial (COMPASS Excluded), patients eligible for the trial (COMPASS Eligible), and patients who did not meet the “enrichment criteria” for enrolment (COMPASS Not Included).

Methods

We used the CLARIFY Registry, an international observational registry of more than 30.000 patients with stable CAD. In accordance with COMPASS exclusion criteria, patients with a REACH bleeding risk score >10, heart failure (HF), severe renal insufficiency, need for dual antiplatelet therapy (DAPT), or anticoagulant (AC) therapy were excluded. Then, COMPASS inclusion criteria were applied: CAD patients had to be 65 years or more, or, if younger, have documented atherosclerosis (PAD or revascularization involving at least two vascular beds) or at least two enrichment criteria (current smoker, diabetes mellitus, GFR <60 mL/min, or non lacunar ischemic stroke).The ischemic outcome was a composite of CV death, MI, or stroke and bleeding outcome was a composite of bleeding leading to either admission or transfusion, or haemorrhagic stroke.

Results

Among 15.185 patients with comprehensive data allowing precise assessment of eligibility, 43.1% (n=6.540) had at least one exclusion criteria (COMPASS-Excluded), 23.1% (n=3.503) did not have enrichment criteria (COMPASS-Not Included) and 33.9% (n=5.142) were eligible. The vast majority of excluded patients were excluded due to high bleeding risk (62.7% needing DAPT, and 52.7% for high REACH bleeding risk score). The rates (100 patients/year) of ischemic and bleeding outcome were 2.3 [2.1–2.5] and 0.5 [0.4–0.6] respectively for COMPASS-Eligible, 3.0 [2.8–3.2] and 0.6 [0.5–0.7] for COMPASS-Excluded and 1.2 [1.0–1.4] and 0.2 [0.2–0.3] for COMPASS-Not Included.

Ischemic and bleeding events

Conclusion

In a large contemporary registry of stable CAD patients, approximately one of three patients was potentially eligible for adjunction of low-dose rivaroxaban to aspirin. This group is at particularly high risk of ischemic outcome. Patients with exclusion criteria for COMPASS had the worse ischemic and bleeding outcomes and represent a group in need of improved therapy.

Acknowledgement/Funding

None

P5010Use of risk score to identify lower and higher risk subsets among COMPASS-Eligible patients with stable CAD. Insights from the CLARIFY Registry

Background

The COMPASS trial showed that a combination of rivaroxaban and aspirin improved cardiovascular (CV) outcomes in patients with stable coronary artery disease (CAD) compared with aspirin alone, at the expense of increased bleeding. An important issue is to identify in this broad population, patients who are likely to derive the greatest benefit without too great a bleeding risk.

Purpose

To evaluate the performance of the CHA2DS2VaSc (range from 0 to 9), the REACH Recurrent Ischemic Score (RIS) (range from 0 to ≥29) and the REACH Bleeding Risk Score (BRS) (range from 0 to 22) to identify patients with the most favourable trade-off between ischemic and bleeding events, among CAD patients eligible to COMPASS

Methods

We used the CLARIFY Registry, an international registry of >30.000 patients with stable CAD. COMPASS inclusion and exclusion criteria were applied to the CLARIFY population with complete data (n=15.185) to define the “COMPASS eligible population”. Patients at high bleeding risk (REACH BRS >10), were excluded in accordance to COMPASS exclusion criteria. Patients were categorized as low-intermediate (0–1) or high (≥2) CHA2DS2VaSc; low (0–12) or intermediate (13–19) REACH RIS, and low (0–6) or intermediate (7–10) REACH BRS. The ischemic outcome was a composite of CV death, MI or stroke, and the bleeding outcome was a composite of bleeding leading to either admission or transfusion, or haemorrhagic stroke.

Results

The COMPASS-eligible population comprised 5.142 patients (33.9%). Ischemic and bleeding outcome for this group were 2.3 [2.1–2.5] and 0.5 [0.4–0.6] events/100 patient-years, respectively. Patients with high CHA2DS2VaSc score, intermediate REACH BRS and RIS represented 95.5% (n=4.913), 83.8% (n=4.309) and 37.6% (n=1.934) of the population. Regarding ischemic risk, patients with intermediate REACH RIS had the higher ischemic risk (3.0 [2.6–3.4] vs 1.9 [1.7–2.1] for patients with low REACH RIS, p<0.001), followed by intermediate REACH BRS (2.5 [2.2–2.7] vs 1.5 [1.2–2.0] for patients with low REACH BRS, p=0.0003) and high CHA2DS2VaSc score (2.4 [2.2–2.6]), compared to the overall population. Patients with low CHA2DS2VaSc had the lowest ischemic risk (0.6 [0.3–1.3]) compared to the overall population. Regarding bleeding risk, there were no differences between patients categorized according to CHA2DS2VaSc (0.5 [0.2–1.15] vs 0.5 [0.4–0.6], p=0.95) REACH BRS (0.4 [0.3–0.7] vs 0.5 [0.4–0.6], p=0.80) or REACH RIS (0.4 [0.3–0.5] vs 0.5 [0.4–0.7], p=0.26).

Ischemic (blue) and bleeding (red) event

Conclusions

Among a broad population of CAD patients eligible to COMPASS, low CHA2DS2VaSc score identify a small subset of patients with very low ischemic risk which is unlikely to benefit from the adjunction of low dose rivaroxaban to standard therapy. Patients with intermediate REACH Recurrent Ischemic Score had higher ischemic risk, without increased bleeding risk and may be optimal candidates from adjunction of low dose rivaroxaban.

Acknowledgement/Funding

None

2211Prevalence, incidence and prognostic implications of left bundle branch block in patients with stable coronary artery disease. an analysis from the CLARIFY registry

Background

The prevalence, and prognostic implication of left bundle branch block (LBBB) in general population and patients admitted for acute myocardial infarction (MI) as been extensively studied. However, data are scarce about patients with stable coronary artery disease (CAD) and it remains unclear whether LBBB is only a marker of a severe cardiomyopathy or an independent predictor of events in these patients.

Purpose

We aimed to describe the prevalence, incidence and prognostic implications of LBBB in patients with stable CAD. Additionally, we aimed to describe the incidence of newly diagnosed LBBB that occurred without recent myocardial infarction.

Methods

CLARIFY is an international registry of more than 30.000 patients with stable CAD. LBBB was collected at baseline and at each follow-up visit, and patients were considered to have LBBB if the length of the QRS complex was of more than 120 milliseconds. Patients with previous pacemaker implantation of internal cardiac defibrillator were excluded. The primary outcome was a composite of cardiovascular (CV) Death, MI or stroke, and secondary outcomes included hospitalization for heart failure (HF) or the need for pacemaker implantation.

Results

From the 23.457 patients with available data regarding LBBB status, 1.041 (4.4%) had LBBB at baseline and 1.237 (5.3%) had at least one LBBB assessed during 5-year follow-up. Only 21 patients with newly diagnosed LBBB overtime, had a documented MI the same year. Compared to patients without LBBB, patients with LBBB had a higher risk profile regarding age (67.2±10.1 versus 63.6±10.4 years, p<0.0001), history of coronary artery bypass grafting (29.2% vs 23.7%, p<0.0001), diabetes (35.1% vs 28.4%, p<0.0001), and HF (25.2% vs 16.8%, p<0.0001) (Table). In unadjusted analysis, patients with LBBB had a higher risk of primary outcome (13.4% vs 8.7%, p<0.0001) and each secondary outcome. In multivariate analysis taking into account several possible confounders, there was no difference in the rate of CV death, MI or stroke between LBBB or no-LBBB patients (adjusted HR 1.04, 95% CI 0.85–1.29). However, patients with LBBB had a higher rate of pacemaker implantation (adjusted HR 2.21, 95% CI 1.55–3.15, p<0.0001) and hospitalization for HF (adjusted HR 1.53, 95% CI 1.25–1.88, p<0.0001) (Figure).

Outcomes according to LBBB status

Conclusion

The prevalence of LBBB in patients with stable CAD was 4.4% and 5.3% with 5-year follow-up. The overwhelming majority of newly diagnosed LBBB were not contemporary of documented myocardial infarction. LBBB was not associated with a higher rate of major adverse cardiovascular events, including all cause mortality but with a higher risk of pacemaker implantation and hospitalization for heart failure. To our knowledge this is the first study reporting such results in a broad population of stable CAD patients.

Acknowledgement/Funding

None

P996Early experience of transnasal micro-transesophageal echocardiography to guide left atrium appendage closure under conscious sedation

Introduction

Percutaneous left atrial appendage closure (LAAC) is typically performed utilizing transesophageal echocardiography (TEE) and fluoroscopy under general anesthesia (GA) or intracardiac echocardiography (ICE) under conscious sedation. Transnasal microtransesophageal echocardiography (micro-TEE) is a recently described technique to guide structural heart interventions eliminating the need for GA, which is beneficial for all, especially older patients. In this series, we report our initial experience with this novel technique to guide LAAC.

Methods and results

Between June 2018 and January 2019, we performed 30 consecutives LAAC (mean age 80,2 years old) with the Amplatzer AMULET in whom we considered using transnasal micro-TEE under conscious sedation instead of TEE under GA. All patients had a CT prior to the procedure to assess anatomy suitability and to rule out thrombus as well as a follow-up CT performed at 3 months post-LAAC to confirm complete sealing. Three patients had TEE instead of micro-TEE for various reasons (patient preference, cognitive impairment, INR >2). We observed one cross-over to TEE+GA because of a failed esophageal intubation under conscious sedation. Device implantation success rate was 100%. Imaging quality was quoted either good or excellent in 25 of the 26 patients with the remaining being quoted as suboptimal. Patient tolerance was either good or excellent in 24 of the 26 cases. There were five epistaxis noticed, one requiring nasal packing. No device embolization, no significant peri-device leak, no tamponade occurred in any patient during this period. At 3 months, there was no prosthesis thrombosis observed and 23% (6/26) had partial opacification of the LAA behind the prosthesis.

Conclusion

In this series, transnasal micro-TEE was feasible, safe, well tolerated and provided sufficient imaging quality to guide LAAC with the Amplatzer AMULET under conscious sedation. The cheaper cost and the wider field of view of micro-TEE over ICE are potential advantages that could impact the organization of LAAC programs especially when these interventions are planned in the elderly in whom GA carries a significant risk.

Abstract 3225: Enhancement of anti-PD1 and anti-CTLA4 efficacy by NBTXR3 nanoparticles exposed to radiotherapy

The use of checkpoints inhibitors (CPI) has radically changed the medical practices for cancer treatment. Unfortunately, the activity of CPI depends on a preexisting anti-tumor immune response, limiting their use to a small percentage of patients. It is crucial to propose solutions to prime an effective anti-tumor immune response and convert CPI non-responder patients to responders. Recent preclinical/clinical studies have reported that radiotherapy (RT) acts as an efficient modulator of tumor immunogenicity. RT can set in motion processes facilitating tumor recognition by the immune system. Unfortunately, RT rarely generates a sustained anti-tumor immunity and reduction of metastases burden outside the irradiated area - a phenomenon called ‘abscopal effect’ - is hardly obtained after RT and the toxicity to healthy tissues limits the maximum dose of irradiation delivered to patients. NBTXR3 is composed hafnium oxide nanoparticles (HfO2-NP) designed to increase energy dose deposition from inside the cancer cells. The size, shape and surface charge of HfO2-NP allow strong interactions with cancer cells and persistence within the tumor mass after a single intra-tumor administration during the whole RT treatment. The high electron density of HfO2-NP increases interaction probability with ionizing radiations (when compared to tumor tissues with low electron density), resulting in the enhancement of tumor destruction, compared to RT alone. The recent results of phase III in locally advanced Soft Tissue Sarcoma patients demonstrated the significant superiority and clinical benefits of intratumorally injected HfO2-NP activated by RT to treat cancer compared to RT alone, validating the first-in-class mode of action of NBTXR3. In addition, preclinical studies have reported that HfO2-NP activated by RT can induce an anti-tumor immune-response and an abscopal effect. Here, we explored the ability of RT-activated NBTXR3 to increase the efficacy of anti-PD1 or anti-CTLA4 using abscopal assay in immunocompetent mice. In a first assay, mice were subcutaneously injected with 344SQP (mouse lung cancer) cells on both flanks. Then, right tumors were injected with HfO2-NP (or vehicle) and irradiated (or not), while left tumors remain untreated. Some groups of mice received injections of anti-PD1. The same approach was used with CT26 (mouse colorectal cancer) cells, except that mice received anti-CTLA4. For the 344SQP model, tumor growth analysis revealed that NBTXR3+RT and anti-PD1 treatment allows a better tumor control on both sides, compared to other conditions. For CT26 model, NBTXR3+RT and anti-CTLA4 treatment led to a better tumor growth control on both sides, compared to other conditions. These results suggest that NBTXR3 activated by RT could potentiate the anti-PD1 and anti-CTLA4 efficacy, opening new opportunities for the treatment of patients by combination of NBTXR3+RT+CPI.

Citation Format: Yun Hu, Ping Zhang, Audrey Darmon, Maria Angelica Cortez, Sébastien Paris, James Welsh. Enhancement of anti-PD1 and anti-CTLA4 efficacy by NBTXR3 nanoparticles exposed to radiotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3225.

Abstract 536: NBTXR3 potentiate cancer-cell intrinsic interferon beta response to radiotherapy

NBTXR3 represent first in class functionalized radioenhancer optimized for efficient tumor binding and sustained local permanence after intratumoral injection. Recent results of phase III in locally advanced Soft Tissue Sarcoma patients established the significant clinical benefits of NBTXR3 activated by radiation therapy compared to radiotherapy alone. Moreover, preclinical studies using CT26 cells have demonstrated that NBTXR3 activated by RT can induce an anti-tumor immune-response and the abscopal effect. Radiotherapy (RT) can induce T cell-mediated anti-tumor immune responses by multiple mechanisms which include enhancing the recruitment of Batf3-dependent cross-priming dendritic cells (DCs). The latter is contingent on tumor-intrinsic IFN-I induction by cytosolic dsDNA via cGAS/STING pathway, a process that is regulated by the upregulation of Trex1 in a RT dose-dependent fashion (Nat Commun 2017; 8:15618). Here, we utilized the murine TSA breast cancer cell line to test the hypothesis that NBTXR3 strengthens the pro-immunogenic effect of local RT by potentiating tumor cells IFN-I response. For in vitro experiments, TSA cells were exposed to NBTXR3 (800uM) 16 hours prior to RT delivered by a 220-kV source (SARRP) at a dose rate of 283.2 cGy/min. Secreted IFNb in the supernatants was measured by ELISA. Pre-treatment with NBTXR3 enhanced TSA cell radiosensitivity as determined in clonogenic assays. Cell death, as measured by loss of plasma membrane integrity was accelerated by NBTX3 after irradiation of TSA cells with 6 and 8Gy after 24 hours of treatment. NBTXR3 enhanced the secretion of IFNb by irradiated cells. Data suggest that NBTXR3 may enhance the effectiveness of radiation and improve tumor immunogenicity, likely via the induction of IFN-I. The role of the cGAS/STING pathway in the effects of NBTX3 are under investigation in vitro and in vivo.

Citation Format: Maria E Rodriguez-Ruiz, Karsten Pilones, Camille Daviaud, Jeffrey Kraynak, Audrey Darmon, Sebastien Paris, Sandra Demaria. NBTXR3 potentiate cancer-cell intrinsic interferon beta response to radiotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 536.

Abstract 4571: Activation of the cGAS-STING pathway by NBTXR3 nanoparticles exposed to radiotherapy

Radiation therapy (RT) is one of the most used local treatment for many cancer types. In addition to DNA breaks and free radicals production leading to numerous cell damages and cancer cell destruction, many preclinical and clinical studies have demonstrated that RT acts as an efficient modulator of tumor immunogenicity. RT can set in motion a series of processes facilitating tumor recognition by the immune system, such as induction of the immunogenic cell death (ICD). Recent studies reported that RT could also activate the cGAS-STING pathway, which plays a fundamental role in the immune response to cytoplasmic DNA, by activation of the transcriptional factor IRF3, leading to expression of interferon β. Moreover, cGAS-STING activation appears to be an important component for tumor resident Antigen-Presenting Cells (APC) activation, a crucial step for induction of CD8+ T cell response against tumor derived antigens. Interestingly, recent preclinical data showed that STING agonist and RT could synergize to control local and distant tumors. NBTXR3 is composed hafnium oxide nanoparticles used for a single intra-tumor administration and activated by radiation therapy. The size, shape and surface of these nanoparticles have been designed to develop strong interactions with cancer cells - effective cell binding and uptake - and to persist within the tumor mass during the whole RT treatment. The high electron density of NBTXR3 is responsible for an increased probability of interaction with incoming ionizing radiations when compared to tumor tissues with low electron density. NBTXR3 increases energy dose deposition within the cancer cells which results in an enhanced tumor destruction when compared to RT alone. NBTXR3 is currently evaluated in clinical trials including soft tissue sarcoma (phase II/III), head and neck, prostate, liver and rectum cancers (phase I). Here, we explored the ability of RT-activated NBTXR3 to increase cGAS-STING pathway response, compared to RT alone. To achieve this goal, we used human colorectal cancer HCT116-Dual cells, which stably express a secreted luciferase under the control of a minimal promoter containing five IFN-stimulated response elements. This system allows the study of IRF3 transcriptional activity, by monitoring the chemiluminescence. A significant increase of luciferase activity (from 30% to &gt;50% (n=5, p&lt;0.05)) was observed for cells treated with NBTXR3 and irradiated (2Gy to 8Gy), when compared to RT alone. At equivalent dose of RT, NBTXR3 showed a significant increase of cGAS-STING pathway induction that could prime a more effective antitumor immune response.

Citation Format: Julie Marill, Naeemunnisa Mohamed Anesary, Audrey Darmon, Ping Zhang, Sébastien Paris. Activation of the cGAS-STING pathway by NBTXR3 nanoparticles exposed to radiotherapy [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 4571.

Abstract LB-A30: Hafnium oxide nanoparticles with radiotherapy induce immunogenic cell death

Background - Between 70 to 90% of patient have "cold" tumors, i.e. devoid or poorly infiltrated by immune cells, rendering inoperative their treatment by immune checkpoint inhibitors. To allow these patients to benefit from these therapies, it is fundamental to prime an antitumor immune response. Radiotherapy (RT) has demonstrated its ability to induce the immunogenic cell death (ICD), a crucial event allowing the priming of the antitumor immune response. Meanwhile, a new class of material with high electron density, hafnium oxide, was designed at the nanoscale (HfO2-NP) to efficiently absorb ionizing radiation and increase the radiation dose deposition from within the tumor cells and increase killing of cancer cells. Here, we compared the ability of HfO2-NP and RT to RT alone to kill cancer cells and induce immunogenic cell death. Methods - A panel of human and mouse cancer cell lines (mesenchymal and epithelial origin, radiosensitive and radioresistant) were treated or not with HfO2-NP, then irradiated by X-rays. Impact of the treatments on apoptosis and necrosis was assessed by FACS analysis (Annexin V/Propidium iodide). In addition, the production of the DAMPs characteristic of the ICD (secreted adenosine triphosphate (ATP), ecto-calreticulin (ecto-CALR), and extracellular High Mobility Group Box 1 (HMGB1)) and of two additional DAMPs (ecto-heat shock protein 70 (ecto-HSP70) and 90 (ecto-HSP90)) were determined. The ENLITEN ATP Assay system was used to measure the secreted-ATP. Ecto-(CRT, HSP70 and HSP90) were assessed by FACS analysis and HMGB1 by ELISA assay. Results - For all the tested cell lines treated with HfO2-NP and RT, a marked increase of apoptosis and necrosis was demonstrated, compared to cells treated with RT alone. In addition, higher levels of DAMPs (ecto-CRT, ecto-HSP70, ecto-HSP90, secreted ATP and extracellular HMGB1) were measured in the cancer cells treated with HfO2-NP and RT when compared to cancer cells exposed to RT. Conclusion - HfO2-NP has demonstrated its capacity to kill cancer cells more efficiently than radiotherapy alone. HfO2-NP, administered via a single intratumor injection, is currently evaluated in clinical trials including soft tissue sarcoma (phase II/III), head and neck, prostate, liver and rectum cancers (phase I) and would permit to improve the local control of tumors, a crucial parameter for the cure and survival of patients. Here, we further show that the superior ability of HfO2-NP and RT treatment to generate ICD would prime an antitumor immune response with more effectiveness than RT alone can do, converting the tumor into an actual in situ vaccine. Thus, this transformation by HfO2-NP of immunologically “cold” tumors into “hot” tumors would open a new avenue for the use of immune checkpoint inhibitors across oncology, particularly for non- and poor-responder patients.

Citation Format: Julie Marill, Naeemunnisa Mohamed, Audrey Darmon, Laurent Levy, Elsa Borghi, Agnès Pottier, Sébastien Paris. Hafnium oxide nanoparticles with radiotherapy induce immunogenic cell death [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr LB-A30.

Nano-sized cytochrome P450 3A4 inhibitors to block hepatic metabolism of docetaxel

Most drugs are metabolized by hepatic cytochrome P450 3A4 (CYP3A4), resulting in their reduced bioavailability. In this study, we present the design and evaluation of bio-compatible nanocarriers trapping a natural CYP3A4-inhibiting compound. Our aim in using nanocarriers was to target the natural CYP3A4-inhibiting agent to hepatic CYP3A4 and leave drug-metabolizing enzymes in other organs undisturbed. In the design of such nanocarriers, we took advantage of the nonspecific accumulation of small nanoparticles in the liver. Specific targeting functionalization was added to direct nanocarriers toward hepatocytes. Nanocarriers were evaluated in vitro for their CYP3A4 inhibition capacity and in vivo for their biodistribution, and finally injected 24 hours prior to the drug docetaxel, for their ability to improve the efficiency of the drug docetaxel. Nanoparticles of poly(lactic-co-glycolic) acid (PLGA) with a hydrodynamic diameter of 63 nm, functionalized with galactosamine, showed efficient in vitro CYP3A4 inhibition and the highest accumulation in hepatocytes. When compared to docetaxel alone, in nude mice bearing the human breast cancer, MDA-MB-231 model, they significantly improved the delay in tumor growth (treated group versus docetaxel alone, percent treated versus control ratio [%T/C] of 32%) and demonstrated a major improvement in overall survival (survival rate of 67% versus 0% at day 55).

A specific prediction equation is necessary to estimate peak oxygen uptake in obese patients with metabolic syndrome

PURPOSE

The aims were to: (1) compare peak oxygen uptake ([Formula: see text]peak) predicted from four standard equations to actual [Formula: see text]peak measured from a cardiopulmonary exercise test (CPET) in obese patients with metabolic syndrome (MetS), and (2) develop a new equation to accurately estimate [Formula: see text]peak in obese women with MetS.

METHODS

Seventy-five obese patients with MetS performed a CPET. Anthropometric data were also collected for each participant. [Formula: see text]peak was predicted from four prediction equations (from Riddle et al., Hansen et al., Wasserman et al. or Gläser et al.) and then compared with the actual [Formula: see text]peak measured during the CPET. The accuracy of the predictions was determined with the Bland-Altman method. When accuracy was low, a new prediction equation including anthropometric variables was proposed.

RESULTS

[Formula: see text]peak predicted from the equation of Wasserman et al. was not significantly different from actual [Formula: see text]peak in women. Moreover, a significant correlation was found between the predicted and actual values (p < 0.001, r = 0.69). In men, no significant difference was noted between actual [Formula: see text]peak and [Formula: see text]peak predicted from the prediction equation of Gläser et al., and these two values were also correlated (p = 0.03, r = 0.44). However, the LoA95% was wide, whatever the prediction equation or gender. Regression analysis suggested a new prediction equation derived from age and height for obese women with MetS.

CONCLUSIONS

The methods of Wasserman et al. and Gläser et al. are valid to predict [Formula: see text]peak in obese women and men with MetS, respectively. However, the accuracy of the predictions was low for both methods. Consequently, a new prediction equation including age and height was developed for obese women with MetS. However, new prediction equation remains to develop in obese men with MetS.

[An atypical presentation of atherosclerosis in psoriasis: "Porcelain aorta"]

BACKGROUND

Several recent epidemiological studies have shown an increase in cardiovascular morbidity and mortality in patients with psoriasis; such increase is greater in the event of severe and early psoriasis.

PATIENTS AND METHODS

We report the case of a 42-year-old patient with severe skin psoriasis ongoing since childhood and presenting with porcelain aorta, a little-known sign of atherosclerosis. This is the first publication reporting this association.

DISCUSSION

Porcelain aorta results from atherosclerotic calcification of the aortic arch. For long asymptomatic, it can manifest itself in various complications. This observation highlights the importance of cardiovascular risk assessment and of screening for complications thereof in patients presenting psoriasis.

Abstract 2665: NBTXR3 hafnium oxide nanoparticle activated by ionizing radiation demonstrates marked radio-enhancement and antitumor effect via high energy deposit in human soft tissue sarcoma

Local and systemic control of Soft Tissue Sarcoma (STS) remains a clinical challenge. Radiation therapy is part of the standard of care of STS. The narrowness of its therapeutic window represents the main concern for different clinical settings. Thus, local delivery of radiation doses is critical to ensure optimal benefit-risk ratio. NBTXR3, biocompatible hafnium oxide nanoparticles were designed as therapeutics to be activated by ionizing radiation to achieve tumor control by enhancement of local energy deposition.

A global non clinical program was implemented in mesenchymal tumor models. In vitro clonogenic survival assays were performed in two human fibrosarcoma cell lines (HT1080 and Hs913t) and a human liposarcoma cell line (SW872) to evaluate the cellular response to radiation-activated NBTXR3 at increasing concentrations. A marked radio-enhancement was observed in human STS cell lines with dose enhancement factors estimated at 4 Gy ranging from 1.48 up to 5.36 according to NBTXR3 concentrations. Further, in human immortalized MRC5V1 fibroblasts, no significant decrease in clonogenic surviving fraction was observed upon activation of NBTXR3 under similar conditions suggesting a differential radiation response between fibroblasts and fibrosarcoma, liposarcoma cell lines. This differential radiation response was further confirmed between HT1080 fibrosarcoma cell line and MRC5V1 fibroblasts upon activation of NBTXR3 at increasing concentration using high energy gamma-rays.

Mechanistic studies have demonstrated in HT1080 cells that NBTXR3 activation induces an increase of 53BP1 foci associated with more “complex” DNA damages than ionizing radiation alone. The level of unrepaired DNA damages was also estimated by flow cytometry analysis showing a higher level of gamma-H2AX at 48h following NBTXR3 activation than after radiotherapy alone. DNA fragmentation and Annexin V staining have demonstrated that these unrepaired DNA damages upon NBTXR3 activation induces apoptosis in HT1080 fibrosarcoma cells.

In vivo, tolerance and tumor growth delay were investigated in two human xenografted tumor models, HT1080 fibrosarcoma and a patient derived liposarcoma LPS80T3 (poorly differentiated grade 3). No toxicity related to NBTXR3 was reported. In both models, a significant advantage was demonstrated in terms of tumor growth inhibition and survival when compared to radiation therapy alone.

These findings establish a novel approach of treatment, which may be applied to a broad range of tumors. Therefore, incrementing the amount of energy deposited within the tumor through the activation of NBTXR3 crystalline nanoparticles constitutes a revolutionary approach for future clinical investigation.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2665. doi:10.1158/1538-7445.AM2011-2665

One pot synthesis of new hybrid versatile nanocarrier exhibiting efficient stability in biological environment for use in photodynamic therapy

A new versatile hybrid nanocarrier has been designed using a "soft chemistry" synthesis, to efficiently encapsulate a photosensitizer - the protoporphyrin IX (Pp IX) - while preserving its activity intact in biological environment for advantageous use in photodynamic therapy (PDT). The synthesized Pp IX silica-based nanocarriers show to be spherical in shape and highly monodisperse with size extending from 10 nm up to 200 nm according to the synthesis procedure. Upon laser irradiation, the entrapped Pp IX shows to efficiently deliver reactive oxygen species (ROS) which are responsible for damaging tumor tissues. The ability of Pp IX silica-based nanocarriers to induce tumor cell death has been tested successfully in vitro. The stability of the Pp IX silica-based nanocarriers has been followed by UV-vis absorption and fluorescence emission in aqueous media and in 100% mouse serum media. The flexibility of the nanocarrier silica core has been examined as the key parameter to tune the Pp IX stability in biological environment. Indeed, an additional biocompatible inorganic surface coating performed on the Pp IX silica-based nanocarriers to produce an optimized bilayer coating demonstrates to significantly enhance the Pp IX stabilization in biological environments. Such versatile hybrid nanocarriers open new perspectives for PDT.

Novel human-derived cell-penetrating peptides for specific subcellular delivery of therapeutic biomolecules

Short peptide sequences that are able to transport molecules across the cell membrane have been developed as tools for intracellular delivery of therapeutic molecules. This work describes a novel family of cell-penetrating peptides named Vectocell peptides [also termed DPVs (Diatos peptide vectors)]. These peptides, originating from human heparin binding proteins and/or anti-DNA antibodies, once conjugated to a therapeutic molecule, can deliver the molecule to either the cytoplasm or the nucleus of mammalian cells. Vectocell peptides can drive intracellular delivery of molecules of varying molecular mass, including full-length active immunoglobulins, with efficiency often greater than that of the well-characterized cell-penetrating peptide Tat. The internalization of Vectocell peptides has been demonstrated to occur in both adherent and suspension cell lines as well as in primary cells through an energy-dependent endocytosis process, involving cell-membrane lipid rafts. This endocytosis occurs after binding of the cell-penetrating peptides to extracellular heparan sulphate proteoglycans, except for one particular peptide (DPV1047) that partially originates from an anti-DNA antibody and is internalized in a caveolar independent manner. These new therapeutic tools are currently being developed for intracellular delivery of a number of active molecules and their potentiality for in vivo transduction investigated.

[Posture and gait modulation using sensory or attentional cues in Parkinson's disease. A possible approach to the mechanism of episodic freezing]

Parkinsonian patients have difficulties for walking as well as for adapting their posture following a voluntary or automatic movement that will disturb their equilibrium. Furthermore, in Parkinson's disease, the patients can suffer for motor blockades (or freezing) in which the movement is like frozen during its execution. These motor blockades can occur during gait initiation, turning round, as well as during the walking through apertures or small passages, but with a high variability as inter-individual as intra-individual. Cognitive, attentional or sensory stimulation--especially visual information--can interact directly on these motor blockades, either positively inhibiting them or negatively inducing them. The different modulation factors of locomotion as well as posture, in Parkinsonian patient and in healthy elderly, and the special case of the motor blockades in Parkinsonian patients are reviewed here. We also examine the effects of L-DOPA with respect to each of these factors. In the conclusion, the modulation of gait, posture, and freezing are discussed in term of mechanisms involved or hypothesis recently proposed.

Brain and testis selective expression of the glutathione S-transferase Yb3 subunit is governed by tandem direct repeat octamer motifs in the 5'-flanking region of its gene

To gain insight into mechanisms of cell type-specific transcription of class mu-glutathione S-transferase genes, the gene encoding the Yb3 subunit was cloned. Yb3 subunits are selectively expressed at high levels in rat brain and testis but not in liver or kidney. The Yb3 subunit gene spans over 6 kb and consists of 8 exons and 7 introns and a sequence consisting of tandem direct repeat consensus octamer DNA binding motifs separated by a 6 base pair (bp) spacer was identified in its 5'-flanking region. Gel shift assays with a 40 bp segment of DNA containing the two consensus octamer sequences, revealed the presence of specific binding proteins in nuclear extracts of rat brain, testis and C6 glioma cells. DNA binding activity was greatly reduced in liver, kidney and HTC cells. Reporter vectors carrying segments of the 5'-flanking region of the Yb3 subunit gene fused to a luciferase gene were introduced into C6 glioma cells which express high levels of Yb3 subunits, and into HTC cells which do not. The plasmids consisting of the Yb3 gene promoter up to, but not including, the octamer motifs did not support luciferase transcription in the C6 glioma cells, but larger fragments that included the octamer repeat sequences, effectively directed transcription in the C6 glioma cells. With mutated octameric sequences transcriptional activity was greatly reduced, and none of the same Yb3 constructs directed substantial luciferase transcription in the HTC cells. The results show that octamer motifs in the 5'-flanking region of the Yb3 subunit gene are functional and are the principal cis-acting elements that account for its discrete cell type-selective expression. This gene is one of the few known targets for octamer DNA binding transcription factors in brain.

Determination of betaxolol enantiomers by high-performance liquid chromatography. Application to pharmacokinetic studies

A high-performance liquid chromatographic (HPLC) method is described for the determination of (R)- and (S)-enantiomers of betaxolol in blood and other biological fluids. Separation of the enantiomers is performed after preparation of diastereomeric derivatives with the chiral reagent R(-)-naphthylethylisocyanate by reversed-phase HPLC. Fluorimetric detection allows the quantification of betaxolol enantiomers down to 0.5 ng/ml. This method was used to evaluate the pharmacokinetic profile of the betaxolol enantiomers in three subjects following one single oral dose (20 mg) of racemic betaxolol. No significant difference was observed in blood levels of the isomers.

Oriented reconstitution of red cell membrane proteins and assessment of their transmembrane disposition by immunoquenching of fluorescence

The two major membrane glycoproteins of human red cells, glycophorin and band 3, the anion exchange protein, were isolated from cells exofacially labeled with fluorescein and reconstituted into vesicles with defined transmembrane disposition. Uniform orientation of polypeptides was accomplished by two procedures: Vesicles with single protein units were obtained by a one-step dilution of a protein/detergent suspension with a vast excess of phospholipid. Vesicles with uniform orientation of protein were selected by affinity chromatography on derivatized Sepharoses (organomercurial, wheat germ agglutinin, aminoethyl or diethylaminoethyl). Vesicles with multiple protein units with uniform orientation were generated by vectorial immobilization of detergent solubilized proteins on the above affinity matrices and in situ formation of proteoliposomes by detergent substitution for phospholipid. The proteoliposomes were released from the column by addition of excess free ligand. The orientation of band 3 and glycophorin in the reconstituted vesicles was first assessed by immunofluorescence quenching, using anti-fluorescein antibodies, to quantitatively quench fluorescein residues exposed on the outer surface of vesicles. Further assessment was achieved by chromatographing the vesicles through various affinity and ionic matrices. Vesicle populations of higher than 90% homogeneity in protein orientation (right-side-out or inside-out) were obtained with both procedures. The above methods provide a convenient experimental tool for the oriented reconstitution of proteins and the evaluation of their transmembrane disposition.

Orientation of transmembrane polypeptides as revealed by antibody quenching of fluorescence

We describe here a new method, based on fluorescent techniques, for the determination of the orientation of membrane protein molecules present in vesicles. The method consists of: (a) attachment of a fluorescein derivative to sugar residues of glycoproteins and glycolipids in the cell membrane, and (b) the use of anti-fluorescein antibody, a highly efficient quencher of fluorescein fluorescence, for the quantitative evaluation of sidedness of transmembrane orientation of protein molecules in vesicles. Since antibody molecules do not permeate membranes, quenching is limited exclusively to sites exposed at the external surface of the vesicles. Addition of antibody to a fluorescently-labeled cell suspension results in a full and immediate quenching of the fluorescent signal. The method is highly sensitive (pM protein concentration), rapid and readily applicable to various vesicle preparations. With this method we assessed the orientation of vesicles derived from red blood cell membranes (ghosts) in isotonic medium and followed their inversion from right-side-out to inside-out orientation upon incubation in alkaline, low ionic strength medium.

New approaches for the reconstitution and functional assay of membrane transport proteins. Application to the anion transporter of human erythrocytes

The human red blood cell anion transport protein, band 3, was isolated and reconstituted into lipid vesicles. The main feature of the new reconstitution is the replacement of native lipids and of solubilizing detergent by externally added lipids, while band 3 protein is immobilized on a gel matrix. The vesicles formed upon detergent removal and sonication are unilamellar and sealed, and band 3 protein is the major polypeptide detectable in them. The method consists of: (a) solubilization of alkali-treated red blood cell membranes by Triton X-100; (b) binding of glycophorin and band 3 protein to diethylaminoethyl (DEAE)-cellulose in Triton X-100 solution, followed by high ionic strength elution; (c) band 3 protein complexation to organomercurial Sepharose; (d) exchange of the Triton X-100 with the dialyzable detergent octylglucopyranoside, while band 3 protein is complexed to the column; (e) elution of band 3 by cysteine (5 mM) in the presence of octylglucopyranoside; (f) addition of lipids (asolectin or egg phosphatidylcholine) to the protein-detergent suspension; and (g) dialysis of the mixture against 1% bovine serum albumin to remove the detergent completely. The vesicles were assayed for anion transport capacity by a novel procedure which is based on the fluorescent substrate N-(2-aminoethylsulfonate)7-nitrobenz-2-oxa-1,3-diazole (NBD-taurine) and on anti-NBD-antibodies as quenchers of extravesicular NBD-taurine fluorescence. Efflux of NBD-taurine from vesicles was monitored in a continuous mode as a decrease in intravesicular fluorescence. The band 3-mediated flux was approx. 50% inhibitable by externally added disulfonic stilbenes, indicating the random distribution of band 3 protein in reconstituted vesicles. Both the specific transfer rate (i.e., nmol substrate/mg protein per min) of band 3 and its energy of activation (Ea) in the artificial lipid milieu were similar to those obtained with the native system. Glycophorin incorporation into this milieu had no significant effect on the associated anion transport properties.