99mTc-Radiolabeled TPGS Nanomicelles Outperform 99mTc-Sestamibi as Breast Cancer Imaging Agent.

D-α-Tocopheryl polyethylene glycol 1000 succinate (TPGS) is a Food and Drug Administration (FDA) approved biomaterial that can form nanosized micelles in aqueous solution. TPGS micelles stand as an interesting system to perform drug delivery as they can carry lipophilic drugs and overcome P glycoprotein efflux as well. Therefore, TPGS micelles combined with other copolymers have been reported in many cancer research studies as a carrier for therapeutic drugs. Their ability to reach tumoral tissue can also be exploited to develop imaging agents with diagnostic application. A radiolabeling method with 99mTc for TPGS nanosized micelles and their biodistribution in a healthy animal model as well as their pharmacokinetics and radiolabeling stability in vivo was previously reported. The aim of this work was to evaluate the performance of this radioactive probe as a diagnostic imaging agent compared to routinely available SPECT radiopharmaceutical, 99mTc-sestamibi. A small field of view gamma camera was used for scintigraphy studies using radiolabeled TPGS micelles in two animal models of breast cancer: syngeneic 4T1 murine cell line (injected in BALB/c mice) and chemically NMU-induced (Sprague-Dawley rats). Ex vivo radioactivity accumulation in organs of interest was measured by a solid scintillation counter, and a semiquantitative analysis was performed over acquired images as well. Results showed an absence of tumoral visualization in 4T1 model for both radioactive probes by gamma camera imaging. On the contrary, NMU-induced tumors had a clear tumor visualization by scintigraphy. A higher tumor/background ratio and more homogeneous uptake were found for radiolabeled TPGS micelles compared to 99mTc-sestamibi. In conclusion, 99mTc-radiolabeled TPGS micelles might be a potential SPECT imaging probe for diagnostic purposes.

Comparison of [18F]Fluorocholine and [18F]Fluordesoxyglucose for assessment of progression, lung metastasis detection and therapy response in murine 4T1 breast tumor model.

The [18F]Fluorocholine ([18F]FCH) tracer for PET imaging has been proven to be effective for several malignances. However, there are only a few studies related to its breast tumor applicability and they are still limited. The aim of this study was investigate the efficacy of [18F]FCH/PET compared to [18F]FDG/PET in a murine 4T1 mammary carcinoma model treated and nontreated. [18F]FCH/PET showed its applicability for primary tumor and lung metastasis detection and their use for response monitoring of breast cancer therapeutics at earlier stages.

Nanostructured Lipid Carrier Co-loaded with Doxorubicin and Docosahexaenoic Acid as a Theranostic Agent: Evaluation of Biodistribution and Antitumor Activity in Experimental Model.

PURPOSE: Nanotheranostic platforms, i.e., the combination of both therapeutic and diagnostic agents on a single platform, are emerging as an interesting tool for the personalized cancer medicine. Therefore, the aim of this work was to evaluate the in vivo properties of a Tc-99m-labeled nanostructured lipid carrier (NLC) formulation, co-loaded with doxorubicin (DOX) and docosahexaenoic acid (DHA), for theranostic applications. PROCEDURES: NLC-DHA-DOX were prepared busing the hot melting homogenization method using an emulsification-ultrasound and were radiolabeled with Tc-99m. Biodistribution studies, scintigraphic images, and antitumor activity were performed in 4T1 tumor-bearing mice. RESULTS: NCL was successfully radiolabeled with Tc-99m. Blood clearance showed a relatively long half-life, with blood levels decaying in a biphasic manner (T1/2 α = 38.7 min; T1/2 ß = 516.5 min). The biodistribution profile and scintigraphic images showed higher tumor uptake compared to contralateral muscle in all time-points investigated. Antitumor activity studies showed a substantial tumor growth inhibition ratio for NLC-DHA-DOX formulation. In addition, the formulation showed more favorable toxicity profiles when compared to equivalent doses of free administered drugs, being able to reduce heart and liver damage. CONCLUSIONS: Therefore, NLC-DHA-DOX formulation demonstrated feasibility in breast cancer treatment and diagnosis/monitoring, leading to a new possibility of a theranostic platform.

Comparison of biodistribution profile of monoclonal antibodies nanoparticles and aptamers in rats with breast cancer.

The use of monoclonal antibodies and aptamers is growing every single day, as the use of nanoparticle systems. Although most of the products are under investigation, there are a few commercialized products available at the market, for human consume. In this study, we have compared three formulations (aptamer anti-MUC1, monoclonal antibody - Trastuzumab and monoclonal antibodies nanoparticles - PLA/PVA/MMT trastuzumab) to identify their profile as also to understand their behavior into an alive biological system. In this direction the radiolabeling of the products were done and they were all tested in animals (in vivo) in two conditions: healthy rats and breast cancer induced animals. The results showed that the nanoparticle has the better biodistribution profile, followed by the aptamer. We conclude that more studies and a global effort to elucidate the biological behavior of drugs and especially nano-drugs are necessary.

Visualization and body distribution of [¹³¹I]-herceptin in nude mice with BT-474 breast carcinoma.

The study aimed to investigate the bio-distribution and radio-immuno-imaging features of [(131)I]-herceptin in nude mice with BT-474 breast carcinoma. [(131)I]-Herceptin was administrated by tail intravenous injection to the nude mice with BT-474 breast carcinoma. Radiocounting was performed at 4, 12, 24, 48, and 96 h after administration. The activity ratio in the tumor tissue and non-tumor tissue (T/NT) and the radiocounting percentage per gram tissue to the injected dose (%ID/g) were calculated. The nude mice with BT-474 breast carcinoma were also visualized continuously by single photon emission computed tomography at 2, 4, 8, 12, 24, 48, and 96 h after the injection of [(131)I]-herceptin. Nude mice with MDA-MB-231 used as the control group were subjected to the same analyses. Clear tumor images were obtained after the injection of [(131)I]-herceptin in nude mice with BT-474 breast carcinoma. The images were the clearest at 24 h after the injection and remained clear even at 96 h. The T/NT ratio and %ID/g in the tumor tissues of nude mice with BT-474 were both significantly higher than those of the control group (P < 0.01). [(131)I]-Herceptin displays tumors clearly in the nude mice with BT-474 and accumulates well in the tumor tissues.

Synthesis and evaluation of (99m)Tc chelate-conjugated bevacizumab.

Vascular endothelial growth factor (VEGF) is one of the classic factors involved in tumor-induced angiognesis in several solid tumors. Bevacizumab, a monoclonal antibody against VEGF, can be used as an imaging tool in preclinical studies. The aim of this study was to radiolabel Bevacizumab with (99m)Tc and to evaluate in vivo its imaging properties in an adenocarcinoma animal model. For this purpose, Bevacizumab was derivatized with Suc-HYNIC as a bifunctional coupling agent. A mixture of Tricine/SnCl(2).2H(2)O was added to Bevacizumab-HYNIC and radiolabeled with (99m)TcO(4)(-). The radiochemical stability of the radiolabeled antibody was assessed. Biodistribution and scintigraphy imaging were performed in normal CD1 female mice and in spontaneous adenocarcinoma tumor bearing CD1 mice (n = 5). We demonstrated that 99mTc-HYNIC-Bevacizumab was stable. In vivo biodistribution studies revealed that tumor uptake of (99m)Tc-HYNIC-Bevacizumab was 1.37 ± 0.51% and 5.33 ± 2.13% at 4 and 24 h postinjection, respectively. Scintigraphy image studies showed tumor selective uptake of (99m)Tc-HYNIC-Bevacizumab in the tumor-bearing mice. We conclude that (99m)Tc-HYNIC-Bevacizumb has the potential to be used as a tracer for tumor imaging in preclinical studies.

Hemosiderin: a new marker for sentinel lymph node identification.

PURPOSE: To evaluate and present our initial results of a new marker (hemosiderin) for mammary sentinel lymph node identification in an experimental model. METHODS: Skins mapped like a lymphatic duct draining to the axilla in patients submitted to breast biopsy, in our mastology service, stimulated us to try it in an animal model (female dogs). Our theory was that some blood derivate (hemosiderin) was captured by macrophages and accessed the lymphatic ducts in direction to the axilla. Six female dogs of no defined race were studied. We injected 0,2 ml of technetium on both superior mammary glands. After ten minutes, a 2,5 ml solution of hemolized blood (hemosiderin) from the own animal was injected in the subareolar lymphatic plexus on the left superior mammary gland and 2,5 ml of patent blue concomitantly and equally on the contralateral gland. Ten minutes after, incisions on both axillae were made to search, through the lymphatic mapping and a gamma probe, the sentinel lymph nodes. RESULTS: Seven brown sentinel lymph nodes were identified and also radiomarked on the left axilla. Six blue sentinel lymph nodes were identified and also radiomarked on the right axilla. CONCLUSION: Preliminary studies of a potential new dye for sentinel lymph node identification are presented. It may be the change of the current use of the blue dyes and their severe side-effects on patients submitted to sentinel lymph node biopsies.

In vivo evaluation of three different 99mTc-labelled radiopharmaceuticals for sentinel lymph node identification.

This work was designed to compare sentinel lymph node (SLN) uptake of 99mTc-labelled human serum albumin colloid (99mTc-HSAC), 99mTc-labelled antimony sulphur colloid (99mTc-SC) and a 99mTc-labelled dextran 70 solution (99mTc-Dx) and their selectivity in the identification of this node in the right rear footpad (RRF) of normal mice and tumour bearing mice. Radiopharmaceutical uptake in the SLN (popliteal lymph node) and the lumbar lymph node (LLN), the second lymphatic node station from RRF, were measured at different time points post-intradermal or intratumoural injection into the RRF of NIH normal mice and of Balb/c mice harbouring the murine mammary tumour M2. 99mTc-HSAC uptake in the SLN was significantly higher than LLN uptake. The 99mTc-SC demonstrated high uptake in SLN, but accumulation in LLN was also high. 99mTc-Dx showed low uptakes in both SLN and LLN. The intradermal injection resulted in a more effective radiopharmaceutical accumulation in SLN than did the intratumoural inoculation. Data also show that increments in tumour volume reduced radiopharmaceutical uptake in the SLN. Our results show that 99mTc-HSAC exhibits the highest uptake in the SLN combined with the smallest amounts of radiopharmaceutical passing through to the LLN. Therefore, 99mTc-HSAC appears to be the best radiopharmaceutical for sentinel node detection.

Labelling, control and radiopharmacological evaluation of 99mTc-adenosine 5'-diphosphate (99mTc-ADP) as tumour seeking agent.

A study of 99mTc-adenosine-5'-diphosphate (99mTc-ADP) as a radiopharmaceutical for tumour diagnosis is presented. Two different labelling methods, using SnCl2 in alkaline solution and Zn as reducing agents, were developed. Reduction with Sn(II) alkaline solution was the selected method because a lower concentration of ADP (0.5 mg/mL) could be used and a higher radiochemical yield was achieved. A labelled molecule with a radiochemical purity higher than 95%, in vitro stability of at least 6 hours and an over all negative charge was obtained Biodistribution studies carried out in normal mice and rats revealed rapid urinary excretion and no specific accumulation of activity in any other particular organ. This behaviour was similar to that reported for 99mTc-adenosine-5'-triphosphate (99mTc-ATP). Rapid blood clearance, that could be fitted to a bicompartimental model, was also verified. No evidence of in vivo instability was observed. Studies in mice and rats bearing spontaneous mammary adenocarcinomas were performed and the results were compared to those from the 99mTc-ATP studies. Although the tumour models used were not the same, the incorporation of both labelled compounds was very similar. Radioactivity uptake in the tumour and the tumour-to-blood ratio were not notably high. However, a significant increment was observed in the tumour-to-muscle ratio (1.0 +/- 0.2 at 30 minutes to 2.7 +/- 0.4 at 240 minutes). Whole-body autoradiography enabled tumour visualization. Further investigations, including scintigraphic imaging, must be carried to complete the clinical evaluation of 99mTc-ADP as a tumour seeking agent.

99mTc direct labeling of anti-CEA monoclonal antibodies: quality control and preclinical studies.

The anti-carcinoembryonic B2C114 monoclonal antibody was radiolabeled with 99mTc by a direct method and quality control tested in vitro by instant thin layer chromatography, gel column scanning and cellulose acetate electrophoresis and assessed in vivo for radioimmunodetection on a murine spontaneous mammary carcinoma. The optimal results of percent 99mTc bound to protein were obtained at a dithiothreitol:antibody molar ratio ranging from 800:1 to 1000:1 and at a methylene diphosphonate:stannous fluoride weight ratio of 4.3:1. Although cysteine removed up to 18% of the label during the first 4 h, the stability of the tracer appeared to be excellent in human serum at 37 degrees C and when challenged with DTPA. 99mTc-labeled B2C114 demonstrated good and specific in vivo tumor targeting.

Direct labeling of monoclonal antibodies with 99mTc and radioimmunodetection of a murine mammary carcinoma with 99mTc-B2C114.

Two anti-CEA antibodies, B2C114 and IORCEA1, were radiolabeled with 99mTc by two direct methods (mercaptoethanol and ascorbic acid reduction), and the radio-immunoimaging properties of B2C114 were assessed in mice bearing an M3-reactive tumor. The labeling efficiency was greater than 90% as measured by ITLC in saline, methylethylketone and with serum albumin impregnated sheets using ethanol: water: NH4OH (2:5:1). The label was stable to challenge with excess DTPA, and in the case of ascorbic acid reduction, serum analysis showed that 10-15% of the radioactivity was lost during incubation. In vitro studies demonstrated that the radiolabeled antibodies retained their immunoreactivity. Biodistribution studies in normal Balb/c mice showed that the pattern of uptake was quite similar for both antibodies. Biodistribution of the 99mTc-B2C114 and image studies in the animal model showed that the tumor was clearly visualized and that B2C114 labeled with 99mTc is a possible candidate for human radioimmunodetection of CEA-expressing tumors.

99mTc-ADP: a potential agent for in vivo tumor detection.

The possibility of using 99mTc-labelled nucleotides as tumour seeking agents has been proposed by different research groups. We have recently reported the preparation of a 99mTc-ADP complex with a high radiochemical purity (> 95%), good in vitro and in vivo stability and promising biodistribution results when injected in mice bearing spontaneous mammary adenocarcinomas. Here we report the results of further investigations in animals with spontaneous neoplastic processes, including whole-body autoradiography in mice (20 minutes and 60 minutes post injection) and gamma-camera imaging studies in Wistar rats. Dynamic studies (up to 45 minutes) and static images (up to 18 hours) were acquired to determine the pharmacokinetics of 99mTc-ADP and the tumour/muscle and tumour/blood ratios. Blood-pool studies were also performed as a control. Tumours were visualized by autoradiography as was to be expected from the biodistribution studies. Dynamic studies showed a rapid blood clearance and a behaviour that fitted to a tricompartimental model. Radioactivity was rapidly taken up by the kidneys and excreted in the urine. No evidence of in vivo instability of the complex was observed. Tumour uptake reached the maximum values after 20 minutes post-injection. Tumour/blood and tumour/muscle ratios improved over time, enhancing tumour visualization. The best images were obtained after 3 hours post injection. In summary, our studies suggest that 99mTc-ADP is a promising radiopharmaceutical for tumour diagnosis.

Specific biodetection of a murine spontaneous mammary carcinoma with labelled anti-human blood group-A monoclonal antibody.

The expression of cell surface antigens of the spontaneous transplantable M3-murine tumour was studied by means of the monoclonal antibody (MAb) B2C114 which recognizes the human blood group-A carbohydrate antigen. Following radioiodination the MAb retained their immunoreactivity and demonstrated a significantly higher in vitro binding with isolated M3-tumour cells as compared with a control antibody. B2C114 revealed 10(6) antigenic sites per cell, with a constant affinity of 5.1 x 10(9)/M. Biodistribution studies showed that B2C114 discriminated between malignant tumour and mouse normal tissues. Radioimmunodetection of Balb/c mice bearing s.c. M3-tumour showed that tumour was specifically defined without subtraction 1 day after injection of the radiolabelled antibody.