Preclinical development of a docetaxel nanocarrier to enhance prostate cancer radiosensitivity

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Background: From 30% to 50% of high risk prostate cancer patients who undergo radiation therapy (RT) will have a biochemical failure. Combining chemotherapy, such as Docetaxel (DXL), with RT can enhance its efficiency. Multidrug resistance mechanisms often limit drug efficacy by decreasing tumor cell intracellular concentration of drugs. There is interest to develop nanocarrier of DXL to maintain drug inside cancer cells by improving its efficacy. The purpose of this study was to develop a titanate-nanotube (TiONt)-DXL nanocarrier (nanohybrid) and to evaluate its in vivobiodistribution as well as its radiosensitizing efficacy in association with RT on a hormone-independent prostate cancer model. Methods: DXL molecules were grafted on TiONts using PEG-3000 molecules to generate the nanohybrid. In vitrocytotoxic activity of the nanohybrid was evaluated on PC-3 cell line using MTS assay. After intratumoral injection, biodistribution analysis was performed by SPEC-CT imaging of mice bearing subcutaneous PC-3 human prostate tumors. To evaluate the benefit of nanohybrid and RT association, tumors were irradiated using 3 fractions of 4Gy administrated after the injection of nanohybrids. Nine groups of 7 mice were used to evaluate nanohybrid and RT association efficacy : untreated, control with buffer IT injection, +/- RT, free DXL, +/- RT, TiONt +/- RT and TiONt-DXL +/- RT. Mice behavior, health status and tumor volume were monitored twice a week until tumor growth recovery. Results: Biodistribution kinetics showed that more than 70% of nanohybrids were localized into the tumor 96 hours after injection. Mice receiving nanohybrid-RT exhibited a significant tumor growth delay to reach a volume of 1,000mm3compared to mice receiving free DXL-RT: 73.7 days (median, [58.9-89]) vs 56 days (median, [31.5-74]) (p=0.0127). Conclusions: TiONt-DXL improves RT efficacy compared to free DXL. These results suggest that local control might be enhanced by TiONt-DXL. TiONt-DXL can be injected as a radiosensitizer in men harboring high risk localized prostate cancer with needles during prostate brachytherapy procedure.

Abstract 5442: Biodistribution and antitumor efficacy study of novel Her2 targeting DARPins

Introduction:

DARPins are genetically engineered small-sized proteins exhibiting high affinity for target proteins. The epithelial growth factor receptor 2 (Her2/neu) is a target of interest for targeted therapies as it is overexpressed in epithelial tumors such as breast and gastric cancers. Antitumor activity and biodistribution of novel Her2-targeting DARPins were evaluated in mice bearing Her2-positive human breast tumors.

Materials and methods:

Antitumor activity and biodistribution studies were performed in female Balb/c Nude mice bearing subcutaneous BT-474 human breast tumors. Mice were treated intravenously (IV) every 3 days with five different DARPins at 20 or 35 mg/kg and antitumor activity was evaluated by measuring tumor growth twice weekly. For the biodistribution study, DARPins were radiolabelled with technetium-99m (99mTc) using the IsoLink procedure. Quality control of the radiolabelled DARPins was performed by size exclusion chromatography, ELISA assay, and binding to tumor cells. 99mTc-radiolabelled DARPins were injected IV to mice at 23-25 MBq/mouse. 4 and 24 hours post-injection, animals were euthanized for blood, tumor and organ collection. Radioactivity in each sample was measured and normalized to sample weight and injected dose (% ID/g). The depth of tumor penetration of 99mTc-radiolabelled DARPins was also assessed by planar autoradiography imaging.

Results:

All five DARPins displayed a significant antitumor activity. Four DARPins induced BT-474 tumor regression while the fifth led to BT-474 tumor stasis. All DARPins were efficiently radiolabelled with 99mTc to radiochemical purities within 50% to 90%, and they all retained the ability to fully bind Her2. The five DARPins displayed a comparable distribution pattern. Radioactivity uptake in blood ranged from 25-30% and 8-10 % ID/g at 4 and 24 hours post-injection, respectively. Accumulation in tumors increased from 6-10% ID/g at 4 hours to 12-20% ID/g at 24 hours. All 99mTc-radiolabelled DARPins were excreted through the liver and kidneys and radioactivity uptake in both organs, respectively, ranged from 7-14% ID/g and 4-8% ID/g at 24 hours post-injection. Planar autoradiography imaging revealed that the depth of penetration of DARPinsinto the tumor was > 2 mm as soon as 4 hours post-injection.

Conclusions:The five anti-Her2 DARPins investigated efficiently targeted BT-474 tumors and significantly inhibited their growth, making them attractive as new therapeutic agents for the treatment of Her2-positive cancers. Their easy radiolabelling with 99mTc also makes them attractive tools for imaging with diagnostic and predictive purposes, for instance to follow the modulation of Her2 expression during therapy.

Citation Format: Olivier Raguin, Marie Leblanc, Bertrand Collin, Alexandra Oudot, Jean-François Mirjolet, Ulrike Fiedler, Ignacio Dolado. Biodistribution and antitumor efficacy study of novel Her2 targeting DARPins. [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 5442. doi:10.1158/1538-7445.AM2014-5442

Abstract 2757: Pharmaco imaging study of the effects of Debio 1143, a new orally available IAP inhibitor, in a triple negative breast cancer model

Introduction: Inhibitors of apoptosis proteins (IAPs) are key negative regulators of programmed cell death. Their frequent deregulation in most cancer types contributes to tumor cell survival and resistance to cancer therapy, making IAPs attractive therapeutic targets. Debio 1143 (formerly named AT-406), a new potent orally-available monovalent SMAC mimetic, targets multiple IAP members and is currently in clinical trials for cancer treatment. In this study, pharmaco-imaging was used to evaluate the effects of Debio 1143 on tumor cell death and metabolism in the triple negative breast cancer (TNBC) cell line MDA-MB-231.

Material and Methods: The effects of Debio 1143 on caspase-3 activation (FACS), apoptosis-induced membrane changes (FACS and radioactive detection of Annexin V binding), and cell proliferation (MTS assay) were evaluated in MDA-MB-231 cells. In vivo pharmaco-imaging experiments were performed in CB17 SCID mice bearing subcutaneous MDA-MB-231 TNBC tumors. 99mTc-Annexin V SPECT/CT (Single Photon Emission Computed Tomography/Computed Tomography) imaging was performed 6 hours and 24 hours after a single treatment with vehicle, Debio 1143 (100 mg/kg per os) or paclitaxel (7.5 mg/kg intravenously), and was completed by gamma counting of organs. Tumor metabolism was evaluated by 18F-FDG (fluorodeoxyglucose) PET/CT (Positron Emission Tomography) while animals received repeated administrations of vehicle, Debio 1143 (100 mg/kg per os) or paclitaxel (7.5 mg/kg intravenously).

Results: In MDA-MB-231 cells, Debio 1143 as a single agent was highly effective in inducing apoptosis. This was reflected by a dose-dependent activation of caspase-3, an increase of Annexin V cell binding, and a cytotoxic activity with a mean IC50 of 224 nM. In MDA-MB-231 tumor-bearing mice, Debio 1143 showed an effect on 99mTc-Annexin V tumor binding with an increased tumor SPECT signal and gamma counting results 6 hours after oral administration, while paclitaxel maximum effects were detected at 24 hours post-treatment. During repeated administration, oral Debio 1143 inhibited tumor growth, which was associated with a decreased tumor 18F-FDG uptake when measured during treatment (after 1 and 2 weeks of treatment). The effects on tumor growth and 18F-FDG uptake were still present 1 week after the end of the treatment period.

Conclusion: This pharmaco-imaging study of the effects of Debio 1143 in TNBC showed that Debio 1143 induced apoptosis both in vitro and in vivo. Moreover, 18F-FDG PET imaging made it possible to observe the effect of Debio 1143, suggesting that this imaging technique may be useful in a clinical setting. To conclude, this study supports the use of Debio 1143 in the treatment of TNBC - a still unmet medical need.

Citation Format: Alexandra Oudot, Olivier Raguin, Lucile Bauché, Francis Bichat, Anne Vaslin, Hélène Maby-El Hajjami, Claudio Zanna, Grégoire Vuagniaux, Pierre Fumoleau, François Brunotte, Bertrand Collin. Pharmaco imaging study of the effects of Debio 1143, a new orally available IAP inhibitor, in a triple negative breast cancer model. [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 2757. doi:10.1158/1538-7445.AM2014-2757

Dual labeling of lipopolysaccharides for SPECT-CT imaging and fluorescence microscopy

Lipopolysaccharides (LPS) or endotoxins are amphipathic, pro-inflammatory components of the outer membrane of Gram-negative bacteria. In the host, LPS can trigger a systemic inflammatory response syndrome. To bring insight into in vivo tissue distribution and cellular uptake of LPS, dual labeling was performed with a bimodal molecular probe designed for fluorescence and nuclear imaging. LPS were labeled with DOTA-Bodipy-NCS, and pro-inflammatory properties were controlled after each labeling step. LPS were then radiolabeled with (111)In and subsequently injected intravenously into wild-type, C57B16 mice, and their in vivo behavior was followed by single photon emission computed tomography coupled with X-ray computed tomography (SPECT-CT) and fluorescence microscopy. Time course of liver uptake of radiolabeled LPS ((111)In-DOTA-Bodipy-LPS) was visualized over a 24-h period in the whole animal by SPECT-CT. In complementary histological analyses with fluorescent microscopy, the bulk of injected (111)In-DOTA-Bodipy-LPS was found to localize early within the liver. Serum kinetics of unlabeled and DOTA-Bodipy-labeled LPS in mouse plasma were similar as ascertained by direct quantitation of β-hydroxymyristate, and DOTA-Bodipy-LPS was found to retain the potent, pro-inflammatory property of the unlabeled molecule as assessed by serum cytokine assays. It is concluded that the dual labeling process, involving the formation of covalent bonds between a DOTA-Bodipy-NCS probe and LPS molecules is relevant for imaging and kinetic analysis of LPS biodistribution, both in vivo and ex vivo. Data of the present study come in direct and visual support of a lipopolysaccharide transport through which pro-inflammatory LPS can be transported from the periphery to the liver for detoxification. The (111)In-DOTA-Bodipy-LPS probe arises here as a relevant tool to identify key components of LPS detoxification in vivo.

[Can one harvest a long bone stick in the radial forearm flap? Original radioanatomical and NanoSPECT-CT Bioscan microvascular study]

OBJECTIVES

The composite radial forearm flap is a surgical option in the reconstruction of large traumatic or oncologic orofacial defects. Nevertheless, it has been criticized for its poor bone transport faculties that would make this flap insufficient in large osseous mandibular reconstructions, or for oral prosthetic rehabilitation with dental implants. What is more, the morbidity of the donor site has often been pointed. The aim of this radioanatomic study was to revisit the vascularization of the composite radial forearm flap, focusing on the bone stick.

METHODS

A radioanatomic study was performed on seven upper limbs taken from fresh cadavers. First, the vessels were washed with a 40°C solution of potassium acetate. Then an intra-arterial injection of a mixture of lead oxide and agar-agar was performed. 3D-CT-scan examinations of the anatomical pieces were performed. In a second step, the flaps were harvested and analyzed with a Microscan examination (NanoSPECT-CT Bioscan(®), voxel 220 microns). Collateral branches of the radial artery to the bone and the skin were counted and classified.

RESULTS

One radial diaphyseal artery was present in all the cases. The nutrient foramen took place at the anteromedial aspect of the diaphysis, between 45 and 65 % of the length of the bone. A dense anastomotic periosteal network was highlightened, supplied by one to four musculoperiosteal branches, and one to six fascio-periosteal arteries arising from the radial artery. A total of mean five osseous branches, and 12 cutaneous branches have been observed.

CONCLUSIONS

The results of the present preclinical study suggested that a 16-cm bone stick could be harvested with an optimal vascular safety, without consideration for the morbidity at the donor site. The original approach in this study, relating anatomy to the preclinical imaging, allowed a precise visualization of the microvascularization of the soft and hard tissues. It opened a field of innovative research in plastic and reconstructive surgery.

Inter/intramolecular Cherenkov radiation energy transfer (CRET) from a fluorophore with a built-in radionuclide

Some radionuclides emit optical light, the Cherenkov radiation (CR, i.e. the blue glow in nuclear reactors), which activates fluorophores.

Application of the optically stimulated luminescence (OSL) technique for mouse dosimetry in micro-CT imaging

PURPOSE

Micro-CT is considered to be a powerful tool to investigate various models of disease on anesthetized animals. In longitudinal studies, the radiation dose delivered by the micro-CT to the same animal is a major concern as it could potentially induce spurious effects in experimental results. Optically stimulated luminescence dosimeters (OSLDs) are a relatively new kind of detector used in radiation dosimetry for medical applications. The aim of this work was to assess the dose delivered by the CT component of a micro-SPECT (single-photon emission computed tomography)∕CT camera during a typical whole-body mouse study, using commercially available OSLDs based on Al2O3:C crystals.

METHODS

CTDI (computed tomography dose index) was measured in micro-CT with a properly calibrated pencil ionization chamber using a rat-like phantom (60 mm in diameter) and a mouse-like phantom (30 mm in diameter). OSLDs were checked for reproducibility and linearity in the range of doses delivered by the micro-CT. Dose measurements obtained with OSLDs were compared to those of the ionization chamber to correct for the radiation quality dependence of OSLDs in the low-kV range. Doses to tissue were then investigated in phantoms and cadavers. A 30 mm diameter phantom, specifically designed to insert OSLDs, was used to assess radiation dose over a typical whole-body mouse imaging study. Eighteen healthy female BALB∕c mice weighing 27.1 ± 0.8 g (1 SD) were euthanized for small animal measurements. OLSDs were placed externally or implanted internally in nine different locations by an experienced animal technician. Five commonly used micro-CT protocols were investigated.

RESULTS

CTDI measurements were between 78.0 ± 2.1 and 110.7 ± 3.0 mGy for the rat-like phantom and between 169.3 ± 4.6 and 203.6 ± 5.5 mGy for the mouse-like phantom. On average, the displayed CTDI at the operator console was underestimated by 1.19 for the rat-like phantom and 2.36 for the mouse-like phantom. OSLDs exhibited a reproducibility of 2.4% and good linearity was found between 60 and 450 mGy. The energy scaling factor was calculated to be between 1.80 ± 0.16 and 1.86 ± 0.16, depending on protocol used. In phantoms, mean doses to tissue over a whole-body CT examination were ranging from 186.4 ± 7.6 to 234.9 ± 7.1 mGy. In mice, mean doses to tissue in the mouse trunk (thorax, abdomen, pelvis, and flanks) were between 213.0 ± 17.0 and 251.2 ± 13.4 mGy. Skin doses (3 OSLDs) were much higher with average doses between 350.6 ± 25.3 and 432.5 ± 34.1 mGy. The dose delivered during a topogram was found to be below 10 mGy. Use of the multimouse bed of the system gave a significantly 20%-40% lower dose per animal (p < 0.05).

CONCLUSIONS

Absorbed doses in micro-CT were found to be relatively high. In micro-SPECT∕CT imaging, the micro-CT unit is mainly used to produce a localization frame. As a result, users should pay attention to adjustable CT parameters so as to minimize the radiation dose and avoid any adverse radiation effects which may interfere with biological parameters studied.

Survivin-3B potentiates immune escape in cancer but also inhibits the toxicity of cancer chemotherapy

Dysregulation in patterns of alternative RNA splicing in cancer cells is emerging as a significant factor in cancer pathophysiology. In this study, we investigated the little known alternative splice isoform survivin-3B (S-3B) that is overexpressed in a tumor-specific manner. Ectopic overexpression of S-3B drove tumorigenesis by facilitating immune escape in a manner associated with resistance to immune cell toxicity. This resistance was mediated by interaction of S-3B with procaspase-8, inhibiting death-inducing signaling complex formation in response to Fas/Fas ligand interaction. We found that S-3B overexpression also mediated resistance to cancer chemotherapy, in this case through interactions with procaspase-6. S-3B binding to procaspase-6 inhibited its activation despite mitochondrial depolarization and caspase-3 activation. When combined with chemotherapy, S-3B targeting in vivo elicited a nearly eradication of tumors. Mechanistic investigations identified a previously unrecognized 7-amino acid region as responsible for the procancerous properties of survivin proteins. Taken together, our results defined S-3B as an important functional actor in tumor formation and treatment resistance.

Sex differentiation in an all-female (XX) rainbow trout population with a genetically governed masculinization phenotype

Sex determination is known to be male heterogametic in the rainbow trout, Oncorhynchus mykiss; however, scattered observations that deviate from this rather strict genetic control have been reported. Here, we provide a detailed morphological and histological characterization of the gonadal differentiation and development (from 43 days postfertilization to 11 months of age) in an all-female (XX) population with a genetically governed masculinization phenotype. In comparison with control males and females, the gonadal differentiation in these animals was characterized by many perturbations, including significantly fewer germ cells. This decrease in germ cells was confirmed by the significantly decreased expression of 2 germ cell maker genes (vasa and sycp3) in the masculinized XX populations as compared with the control females and control males. Although only a proportion of the total adult population was partially or fully masculinized, this early differentiating phenotype affected nearly all the sampled animals. This suggests that the adult masculinization phenotype is the consequence of an early functional imbalance in ovarian differentiation in the entire population. We hypothesize that the lower number of germ cells that we observed in this population could be one cause of their masculinization.

Abstract P4-02-06: Molecular imaging with trastuzumab and pertuzumab of HER2-positive breast cancer in mice: a step towards personalized medicine

Introduction: The accurate and reliable assessment of HER2 status is an essential step in the diagnostic workup and selection of targeted treatment strategy in breast cancer patients. However, current ex vivo methods do not evaluate HER2 status possible discordance between primary tumor and distant metastases, nor immediate response to therapeutic intervention. Non-invasive imaging of HER2 expression could be a relevant alternative with additional benefits such as a better selection of patients for HER2-targeted therapies and the possible optimization of treatment strategies. Recent clinical trials suggest a better efficacy of trastuzumab/pertuzumab doublet but a lower activity of pertuzumab monotherapy over trastuzumab alone.

Aim: The aim of our study was therefore to evaluate preclinically the use of radiolabeled DOTAGA (2, 2′, 2″-(10-(2,6-dioxotetrahydro-2H-pyran-3-yl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetic acid) conjugated trastuzumab and pertuzumab for SPECT/CT (Single Photon Emission Computed Tomography/Computed Tomography) HER2 imaging purposes.

Methods: Trastuzumab and pertuzumab were conjugated to a new bifunctional chelating agent: DOTAGA anhydride (DOTA analog) and subsequently radiolabeled with the gamma-emitter Indium 111. The functionality of [111In]-DOTAGA-antibodies analogs was evaluated by in vitro saturation assays using HER2-overexpressing human breast cancer cell line (HCC1954). In vivo biodistribution was studied by SPECT/CT imaging at 24h, 48h and 72h after intravenous injection of [111In]-DOTAGA-antibodies in subcutaneous BT474 tumor-bearing rodents.

Results: [111In]-DOTAGA-trastuzumab and [111In]-DOTAGA-pertuzumab showed respectively 2.6 and 2.7 DOTAGA/antibody. Both [111In]-DOTAGA-trastuzumab and [111In]-DOTAGA-pertuzumab achieved a radiochemical purity &gt; 95%. Biological activity of [111In]-DOTAGA-trastuzumab and [111In]-DOTAGA-pertuzumab was maintained: the affinity determined on HER2 expressing HCC1954 cell lines, was 5.5 and 5.6 nM. SPECT/CT imaging experiments in tumor-bearing rodents and gamma-counting of organs both showed that at 72h post-injection, more than 60 % of the activity was localized in the tumor (66.9±0.9 %ID/g for [111In]-DOTAGA-trastuzumab and 63.8±6.3 %ID/g for [111In]-DOTAGA-pertuzumab) and that an excess of non-radiolabeled corresponding antibody significantly shifted down tumor-targeting (to 17.6±2.4 %ID/g for [111In]-DOTAGA-trastuzumab and 8.7±0.8 %ID/g for [111In]-DOTAGA-pertuzumab.

Conclusions: Our results demonstrate a similar HER2 binding of trastuzumab and pertuzumab. Both radiolabeled [111In]-DOTAGA-trastuzumab and [111In]-DOTAGA-pertuzumab should be considered and might be promising tools for molecular imaging diagnosis of HER2 overexpression in breast cancer.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P4-02-06.

Respiratory gated PET/CT in a European multicentre retrospective study: added diagnostic value in detection and characterization of lung lesions

PURPOSE

The aim of our work is to evaluate the added diagnostic value of respiratory gated (4-D) positron emission tomography/computed tomography (PET/CT) in lung lesion detection/characterization in a large patient population of a multicentre retrospective study.

METHODS

The data of 155 patients (89 men, 66 women, mean age 63.9 ± 11.1 years) from 5 European centres and submitted to standard (3-D) and 4-D PET/CT were retrospectively analysed. Overall, 206 lung lesions were considered for the analysis (mean ± SD lesions dimension 14.7 ± 11.8 mm). Maximum standardized uptake values (SUV(max)) and lesion detectability were assessed for both 3-D and 4-D PET/CT studies; 3-D and 4-D PET/CT findings were compared to clinical follow-up as standard reference.

RESULTS

Mean ± SD 3-D and 4-D SUV(max) values were 5.2 ± 5.1 and 6.8 ± 6.1 (p < 0.0001), respectively, with an average percentage increase of 30.8 %. In 3-D PET/CT, 86 of 206 (41.7 %) lesions were considered positive, 70 of 206 (34 %) negative and 50 of 206 (24.3 %) equivocal, while in 4-D PET/CT 117 of 206 (56.8 %) lesions were defined as positive, 80 of 206 (38.8 %) negative and 9 of 206 (4.4 %) equivocal. In 34 of 50 (68 %) 3-D equivocal lesions follow-up data were available and the presence of malignancy was confirmed in 21 of 34 (61.8 %) lesions, while in 13 of 34 (38.2 %) was excluded. In 31 of these 34 controlled lesions, 20 of 34 (58.8 %) and 11 of 34 (32.4 %) were correctly classified by 4-D PET/CT as positive and negative, respectively; 3 of 34 (8.8 %) remained equivocal. With equivocal lesions classified as positive, the overall accuracy of 3-D and 4-D was 85.7 and 92.8 %, respectively, while the same figures were 80.5 and 94.2 % when equivocal lesions were classified as negative.

CONCLUSION

The respiratory gated PET/CT technique is a valuable clinical tool in diagnosing lung lesions, improving quantification and confidence in reporting, reducing 3-D undetermined findings and increasing the overall accuracy in lung lesion detection and characterization.

DOTAGA-trastuzumab. A new antibody conjugate targeting HER2/Neu antigen for diagnostic purposes

Improved bifunctional chelating agents (BFC) are required for indium-111 radiolabeling of monoclonal antibodies (mAbs) under mild conditions to yield stable, target-specific agents. 2,2',2"-(10-(2,6-Dioxotetrahydro-2H-pyran-3-yl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetic acid (DOTAGA-anhydride) was evaluated for mAb conjugation and labeling with indium-111. The DOTA analogue was synthesized and conjugated to trastuzumab-which targets the HER2/neu receptor-in mild conditions (PBS pH 7.4, 25 °C, 30 min) and gave a mean degree of conjugation of 2.6 macrocycle per antibody. Labeling of this immunoconjugate with indium-111 was performed in 75% yield after 1 h at 37 °C, and the proportion of (111)In-DOTAGA-trastuzumab reached 97% after purification. The affinity of DOTAGA-trastuzumab was 5.5 ± 0.6 nM as evaluated by in vitro saturation assays using HCC1954 breast cancer cell line. SPECT/CT imaging and biodistribution studies were performed in mice bearing breast cancer BT-474 xenografts. BT-474 tumors were clearly visualized on SPECT images at 24, 48, and 72 h postinjection. The tumor uptake of [(111)In-DOTAGA]-trastuzumab reached 65%ID/g 72 h postinjection. These results show that the DOTAGA BFC appears to be a valuable tool for biologics conjugation.

Coronary thrombectomy, technical comparison of two systems on a laboratory bench: the impact of bends, angles and thrombus age

AIMS

Despite the results of recent randomised studies, the systematic use of aspiration techniques in ST-elevation myocardial infarction has not been included in the new guidelines. To date, there have been very few bench tests of the different systems and the aim of our study was to test two catheters on different models of arteries with thrombi at six and 12 hours.

METHODS AND RESULTS

The test apparatus consisted of 3 mm diameter glass tubes of 150 mm in length. The thrombi were left for either six or 12 hours and ten models of tubes were used: straight, with a single bend and with two bends. Two types of catheters were tested: the Export® aspiration catheter (EAC) and the Proxis® embolic protection system (PES). The main assessment criterion was total thrombectomy. Total thrombectomy was achieved in only 55.3% of the tests and no difference appeared between the two systems. Total thrombectomy was achieved more frequently with 6-hour thrombi than with 12-hour thrombi for the two techniques, 62.5% vs. 42.5% (p = 0.018) and 67.5% vs. 48.7% (p = 0.025) for EAC and PES catheter, respectively. In contrast, total thrombectomy was more frequent in straight tubes and in tubes with a single bend than in tubes with double bends, respectively for EAC (64% vs. 44.8%, p = 0.028) and for PES (85.9% vs. 35.4%, p < 0.001).

CONCLUSIONS

The use of thrombectomy in the invasive management of acute coronary syndromes is growing. Our work on a "laboratory bench" reveals important technical differences. In consequence, in clinical practice, we speculate that the catheter system must be chosen according to both the artery anatomy and the delay between chest pain and PCI.

Abstract 1764: DOTA-conjugated antibodies for scintigraphic evaluation of new anti cancer treatments

Introduction: The treatment of cancer is being revolutionized by the development of targeted therapeutic biologics. Translational pharmaco-imaging represents a key step in the evaluation of these new targeted anti cancer therapies. In this respect, we have implemented and validated an antibody radiolabeling process for scintigraphic SPECT imaging.

Methods: A new macrocyclic reagent (DOTAGA, bearing an anhydride function able to react with primary amines) was used for DOTA conjugation of Trastuzumab®. DOTA Trastuzumab was synthesized by directly reacting DOTAGA with Trastuzumab®. The number of DOTA per antibody was determined using mass spectrometry.

The DOTA-conjugated antibodies were metallated with Indium-111. The functionality of DOTA Trastuzumab analogs was evaluated by in vitro saturation assays using two human breast cancer cell lines (SK BR 3 and HCC1954).

Results: Two DOTA- Trastuzumab analogs were synthesized. The first analog was bearing one DOTA per antibody while the second was bearing 4 DOTA per antibody. The labeling yield reached 90% for both conjugates and high specific activities were obtained (400 MBq/mg). The affinity of the DOTA Trastuzumab analogs, determined on Her2 expressing SK BR 3 and HCC1954 cell lines, was 1 nM and was similar to that of Trastuzumab®. SPECT imaging experiments in tumor bearing rodents are in progress for in vivo validation of the two analogs.

Conclusion: Together, these results demonstrate the efficiency of our new DOTA-synthesis and conjugation processes for biologics radiolabeling to assess biodistribution, anti-cancer efficacy and related toxicity of anti-cancer drugs by in vivo non invasive imaging.

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 1764. doi:10.1158/1538-7445.AM2011-1764

Effect of a chronic cholesterol-rich diet on vascular structure and oxidative stress in LDLR-/- mice

AIMS

There is conflicting evidence regarding the relationship between hypercholesterolemia and oxidative stress in vessels. To test the potential relationship, a mouse model of hypercholesterolemia was used.

METHODS

Low density lipoprotein receptor-deficient (LDLR(-/-)) and control (C57Bl/6) mice were fed a normal or (1.25%) high-cholesterol (HC) diet for 8 weeks, and the incidence of this chronic diet was evaluated on the degree of vascular oxidative stress and vascular structure (collagen content and lipid infiltration expressed in arbitrary units: AU=%/mm(2)).

RESULTS

Animals treated with the HC diet presented an increase in lipid infiltration (0.35±0.13 vs. 1.7±0.18 control and 1.04±0.16 vs. 1.84±0.23 LDLR(-/-), AU p<0.05) associated with higher collagen content (control: 2.13±0.40 vs. 3.46±0.36 and LDLR(-/-): 2.37±0.36 vs. 3.79±0.60; AU p<0.05 red Sirius staining). Interestingly, ROS production in the aorta was only increased in the LDLR(-/-) +cholesterol group (0.17±0.04 and 0.16±0.05 in the control groups, 0.14±0.02 vs. 0.34±0.06 in the LDLR(-/-) groups, p<0.05). C57Bl/6 and LDLR(-/-) mice presented altered vascular structure associated with the rich cholesterol diet, which was not necessarily associated with increased oxidative stress.

CONCLUSION

These findings highlight the complex interrelation between oxidative stress and lipid metabolism in the circulatory tract.

Combining sirolimus-eluting stents and external irradiation in cholesterol-fed rabbits increased incomplete stent apposition and decreased re-endothelialization

Restenosis after the implantation of a drug-eluting stent or after vascular irradiation therapy shares similar physiopathological mechanisms. No experimental data are currently available on vascular wall behavior after external irradiation on arteries stented with sirolimus-eluting stents (SES). Ten New Zealand white rabbits received a 0.5% cholesterol-enriched chow for 1 month. Bilateral iliac artery stent implantation was then performed with an SES (Cypher; Cordis Corp). The animals were randomized into either an irradiated group (I, 2 Gy external x-ray irradiation, n = 5) or a control group (C, n = 5). The cholesterol-enriched chow was continued for 1 additional month after stent implantation. The stented arteries were harvested for histological analyses. The number and the percentage of incompletely apposed stents struts (IASS) were significantly higher in irradiated versus control group (3.05 +/- 0.46 vs. 1.57 +/- 0.27 IASS, P < 0.01, and 28.44% +/- 3.97% vs. 15.2% +/- 2.46% of IASS, P < 0.01, respectively). The mean neointimal thickness behind the IASS was also higher in the irradiated group (I: 28.3 +/- 2.5 microm vs. C: 18.2 +/- 2.3 microm, P < 0.01). Re-endothelialization was lower in irradiated group (I: 44.6% +/- 17.5% vs. C: 75.2% +/- 5.7%, P < 0.01). The present study revealed that low-dose external irradiation increased incomplete stent apposition and reduced re-endothelialization of SES. These results underscore the potential deleterious cumulative side effects of these 2 procedures to prevent restenosis.