Multi-modal imaging probe for assessing the efficiency of stem cell delivery to orthotopic breast tumours

Stem cells have been utilised as anti-cancer agents due to their ability to home to and integrate within tumours. Methods to augment stem cell homing to tumours are being investigated with the goal of enhancing treatment efficacy. However, it is currently not possible to evaluate both cell localisation and cell viability after engraftment, hindering optimisation of therapy. In this study, luciferase-expressing human adipocyte-derived stem cells (ADSCs) were incubated with Indium-111 radiolabelled iron oxide nanoparticles to produce cells with tri-modal imaging capabilities. ADSCs were administered intravenously (IV) or intracardially (IC) to mice bearing orthotopic breast tumours. Cell fate was monitored using bioluminescence imaging (BLI) as a measure of cell viability, magnetic resonance imaging (MRI) for cell localisation and single photon emission computer tomography (SPECT) for cell quantification. Serial monitoring with multi-modal imaging showed the presence of viable ADSCs within tumours as early as 1-hour post IC injection and the percentage of ADSCs within tumours to be 2-fold higher after IC than IV. Finally, histological analysis was used to validate engraftment of ADSC within tumour tissue. These findings demonstrate that multi-modal imaging can be used to evaluate the efficiency of stem cell delivery to tumours and that IC cell administration is more effective for tumour targeting.

A case report on 111In chloride bone marrow scintigraphy in management of adrenal myelolipoma

RATIONALE

Adrenal myelolipoma is a benign hormone-inactive tumor composed of hematopoietic tissue and mature adipose tissue. Because this tumor tends to be rich in fat, in many cases it can be diagnosed based on computed tomography (CT) or magnetic resonance imaging (MRI) findings alone. However, in the presence of much necrosis, calcification and hematopoietic tissue and/or the absence of much fat, and in cases with tumor apoplexy, this tumor becomes difficult to differentiate from other tumors. In such cases, a bone marrow scan may be informative as a non-invasive imaging diagnostic method for preoperative diagnosis of the tumor and determination of the method for the surgical treatment. We herein report a case of huge adrenal myelolipoma with the non-adipose portion identified using an Indium chloride (InCl3) bone marrow scan.

PATIENT CONCERNS

A 69-year-old woman was referred to our hospital because of a left peritoneal mass detected on a medical checkup. Abdominal CT revealed a mass measuring 14.3 cm in diameter located between the left kidney and the left adrenal gland, which showed coexistence of fat and soft tissue densities.

DIAGNOSES

A bone marrow scan is a nuclear medicine examination to assess hematopoietic activity. To avoid excessive resection of the tumor, we thought that a bone marrow scan could be applied for differentiation between myelolipoma and retroperitoneal liposarcoma by evaluating the hematopoietic activity of the tumor. Tumor enucleation was performed, and pathological examination showed a diagnosis of adrenal myelolipoma.

INTERVENTION

The patient was treated with laparoscopic enucleation.

OUTCOMES

No metastatic recurrence was found during 8 months of follow-up.

LESSONS

Diagnosis of myelolipoma by CT and MRI becomes difficult in the presence of a high volume of hematopoietic tissue. In such cases, a bone marrow scan may be informative as a non-invasive imaging diagnostic method for preoperative diagnosis of the tumor and determination of the method of surgical treatment.

Enhancing tissue permeability with MRI guided preclinical focused ultrasound system in rabbit muscle: From normal tissue to VX2 tumor

High Intensity Focused Ultrasound (HIFU) is an emerging noninvasive, nonionizing physical energy based modality to ablate solid tumors with high power, or increase local permeability in tissues/tumors in pulsed mode with relatively low power. Compared with traditional ablative HIFU, nondestructive pulsed HIFU (pHIFU) is present in the majority of novel applications recently developed for enhancing the delivery of drugs and genes. Previous studies have demonstrated the capability of pHIFU to change tissue local permeability for enhanced drug delivery in both mouse tumors and mouse muscle. Further study based on bulk tissues in large animals and clinical HIFU system revealed correlation between therapeutic effect and thermal parameters, which was absent in the previous mouse studies. In this study, we further investigated the relation between the therapeutic effect of pHIFU and thermal parameters in bulky normal muscle tissues based on a rabbit model and a preclinical HIFU system. Correlation between therapeutic effect and thermal parameters was confirmed in our study on the same bulk tissues although different HIFU systems were used. Following the study in bulky normal muscle tissues, we further created bulky tumor model with VX2 tumors implanted on both hind limbs of rabbits and investigated the feasibility to enhance tumor permeability in bulky VX2 tumors in a rabbit model using pHIFU technique. A radiolabeled peptidomimetic integrin antagonist, 111In-DOTA-IA, was used following pHIFU treatment in our study to target VX2 tumor and serve as the radiotracer for follow-up single-photon emission computed tomography (SPECT) scanning. The results have shown significantly elevated uptake of 111In-DOTA-IA in the area of VX2 tumors pretreated by pHIFU compared with the control VX2 tumors not being pretreated by pHIFU, and statistical analysis revealed averaged 34.5% enhancement 24h after systematic delivery of 111In-DOTA-IA in VX2 tumors pretreated by pHIFU compared with the control VX2 tumors.

EGF-coated gold nanoparticles provide an efficient nano-scale delivery system for the molecular radiotherapy of EGFR-positive cancer

Purpose Radiolabeled antibodies and peptides hold promise for molecular radiotherapy but are often limited by a low payload resulting in inadequate delivery of radioactivity to tumour tissue and, therefore, modest therapeutic effect. We developed a facile synthetic method of radiolabeling indium-111 (111In) to epidermal growth factor (EGF)-gold nanoparticles (111In-EGF-Au NP) with a high payload. Materials and methods EGF-Au NP were prepared via an interaction between gold and the disulphide bonds of EGF and radiolabeled using 111InCl3. Targeting efficiency was investigated by quantitating internalized radioactivity and by confocal imaging following exposure of MDA-MB-468 (1.3 × 106 EGFR/cell) and MCF-7 (104 EGFR/cell) cells to Cy3-EGF-Au NP. Cytotoxicity was evaluated in clonogenic assays. Results The proportion of total administered radioactivity that was internalized by MDA-MB-468 and MCF-7 cells was 15% and 1.3%, respectively (mixing ratio of EGF:Au of 160). This differential uptake in the two cell lines was confirmed using confocal microscopy. 111In-EGF-Au NP were significantly more radiotoxic to MDA-MB-468 than MCF-7 cells with a surviving fraction of 17.1 ± 4.4% versus 89.8 ± 1.4% (p < 0.001) after exposure for 4 h. Conclusions An 111In-labeled EGF-Au nanosystem was developed. It enabled targeted delivery of a high 111In payload specifically to EGFR-positive cancer cells leading to radiotoxicity that can be exploited for molecularly targeted radiotherapy.

Evaluation of ¹¹¹in-labelled exendin-4 derivatives containing different meprin β-specific cleavable linkers

BACKGROUND

Cleavable linkers, which are specifically cleaved by defined conditions or enzymes, are powerful tools that can be used for various purposes. Amongst other things, they have been successfully used to deliver toxic payloads as prodrugs into target tissues. In this work novel linker sequences targeting meprin β, a metalloprotease expressed in the kidney brush-border membrane, were designed and included in the sequence of three radiolabelled exendin-4 derivatives. As radiolabelled exendin-4 derivatives strongly accumulate in the kidneys, we hypothesised that specific cleavage of the radiolabelled moiety at the kidney brush-border membrane would allow easier excretion of the activity into the urine and therefore improve the pharmacological properties of the peptide.

RESULTS

The insertion of a cleavable linker did not negatively influence the in vitro properties of the peptides. They showed a good affinity to the GLP-1 receptor expressed in CHL cells, a high internalisation and sufficiently high stability in fresh human blood plasma. In vitro digestion with recombinant meprin β rapidly metabolised the corresponding linker sequences. After 60 min the majority of the corresponding peptides were digested and at the same time the anticipated fragments were formed. The peptides were also quickly metabolised in CD1 nu/nu mouse kidney homogenates. Immunofluorescence staining of meprin β in kidney sections confirmed the expression of the protease in the kidney brush-border membrane. Biodistribution in GLP-1 receptor positive tumour-xenograft bearing mice revealed high specific uptake of the 111In-labelled tracers in receptor positive tissue. Accumulation in the kidneys, however, was still high and comparable to the lead compound 111In-Ex4NOD40.

CONCLUSION

In conclusion, we show that the concept of cleavable linkers specific for meprin β is feasible, as the peptides are rapidly cleaved by the enzyme while retaining their biological properties.

Assessment of effective absorbed dose of (111)In-DTPA-Buserelin in human on the basis of biodistribution rat data

In this study, the effective absorbed dose to human organs was estimated, following intra vascular administration of (111)In-DTPA-Buserelin using biodistribution data from rats. Rats were sacrificed at exact time intervals of 0.25, 0.5, 1, 2, 4 and 24 h post injections. The Medical Internal Radiation Dose formulation was applied to extrapolate from rats to humans and to project the absorbed radiation dose for various human organs. From rat data, it was estimated that a 185-MBq injection of (111)In-DTPA-Buserelin into the human might result in an estimated absorbed dose of 24.27 mGy to the total body and the highest effective absorbed dose was in kidneys, 28.39 mSv. The promising results of this study emphasises the importance of absorbed doses in humans estimated from data on rats.

Imaging DNA damage in vivo using gammaH2AX-targeted immunoconjugates

DNA damage responses (DDR) occur during oncogenesis and therapeutic responses to DNA damaging cytotoxic drugs. Thus, a real-time method to image DNA damage in vivo would be useful to diagnose cancer and monitor its treatment. Toward this end, we have developed fluorophore- and radioisotope-labeled immunoconjugates to target a DDR signaling protein, phosphorylated histone H2A variant H2AX (γH2AX), which forms foci at sites of DNA double-strand breaks. Anti-γH2AX antibodies were modified by the addition of diethylenetriaminepentaacetic acid (DTPA) to allow (111)In labeling or the fluorophore Cy3. The cell-penetrating peptide Tat (GRKKRRQRRRPPQGYG) was also added to the immunoconjugate to aid nuclear translocation. In irradiated breast cancer cells, confocal microscopy confirmed the expected colocalization of anti-γH2AX-Tat with γH2AX foci. In comparison with nonspecific antibody conjugates, (111)In-anti-γH2AX-Tat was retained longer in cells. Anti-γH2AX-Tat probes were also used to track in vivo DNA damage, using a mouse xenograft model of human breast cancer. After local X-ray irradiation or bleomycin treatment, the anti-γH2AX-Tat probes produced fluorescent and single photon emission computed tomography signals in the tumors that were proportionate to the delivered radiation dose and the amount of γH2AX present. Taken together, our findings establish the use of radioimmunoconjugates that target γH2AX as a noninvasive imaging method to monitor DNA damage, with many potential applications in preclinical and clinical settings.

Tumor pretargeting in mice using MORF conjugated CC49 antibody and radiolabeled complimentary cMORF effector

AIM

Using the antiCEA antibody MN14, a LS174T mouse tumor model has been successfully targeted with (⁹⁹m)Tc for imaging and ¹⁸⁸Re for radiotherapy by phosphorodiamidate morpholino oligomers (MORF)/complementary MORF (cMORF) pretargeting strategy. This investigation evaluated the antiTAG-72 antibody CC49 as an alternative to MN14 for this application.

METHODS

Both CC49 and MN14 were labeled with ¹¹¹In via SCN-benzyl-DTPA and their biodistributions were compared to that of MN14 labeled via DTPA anhydride. Since the accessibility of the antibody to the effector is required for optimization of pretargeting, the internalization of both MORF-CC49 and MORF-MN14 antibodies in LS174T cells were evaluated in culture. In addition, the accessible concentration of MORF-CC49 antibody in tumor was determined in a series of pretargeting studies with escalating dosages of the [(⁹⁹m)Tc]cMORF effector. Finally, using these results and our semi-empirical model, an imaging study was performed under optimal pretargeting conditions.

RESULTS

The biodistribution of ¹¹¹In to trace the MN14 antibody depended significantly on the labeling method. Furthermore, both MORF-CC49 and MORF-MN14 antibodies showed rapid internalization in culture. Fortunately, the accessibility in tumor was found to be less seriously reduced in vivo. In a pretargeting study under optimal conditions, both by imaging and by necropsy, the [(⁹⁹m)Tc]cMORF effector accumulated predominantly in the tumor of pretargeted mice. Normal tissue accumulations were minimal except in kidneys, liver, and a segment of intestines.

CONCLUSION

MORF pretargeting with CC49 was equally successful in the LS174T tumor model to the MORF pretargeting with MN14. The MORF-CC49 antibody may therefore be considered for future investigations toward early clinical trials.

LONG-TERM CLEARANCE FROM SMALL AIRWAYS IN PATIENTS WITH CHRONIC BRONCHITIS: EXPERIMENTAL AND THEORETICAL DATA

Long-term clearance (21 days) from small airways was studied in 9 patients with chronic bronchitis (CB), 65 +/- 10 (mean +/- SD) years, and was compared to 15 age-matched healthy subjects of 67 +/- 7 (mean +/- SD) years. Six of the CB patients were studied twice. All subjects inhaled monodisperse 6 microm Teflon particles labelled with 111In with an extremely slow inhalation flow, 0.05 L/s. With this inhalation technique, particles are deposited mainly in the small conducting airways. Lung retention was measured at 0 and 24 hours, and at 7, 14, and 21 days after inhalation. Lung retention at 24 hours (% of deposition) was highly reproducible for the CB patients, studied twice, but it was not significantly different from that found for healthy subjects and, furthermore, not related to airway resistance (Raw), nor FEV1% predicted. Both healthy subjects and CB patients showed significant clearance in the period between 24 hours and day 21. The mean retention were higher (P<.001) in CB patients, 90%, 89%, 87% of 24 hours retention at 7, 14, and 21 days, compared to 80%, 76%, 71% of 24 hours retention at 7, 14, and 21 days measurements for healthy subjects. Clearance after 24 hours (retention at 21 days) was significantly related to FEV1% predicted, but not Raw. Reduced FEV1% predicted values was associated with slower clearance rates. Model calculations were performed to estimate intrapulmonary deposition patterns. A limited effect was shown for airway dimension and uneven ventilation. The differences between healthy and CB patients were, however, limited. It is not possible to conclude whether the difference in clearance after 24 hours is an effect of change in regional deposition, or slower small airway clearance in diseased airways. This technique to target the smallest ciliated airways, using an extremely slow inhalation flow, provides new possibilities to investigate smallest airway function and drug delivery that merits further investigations.

Pretargeted radioimmunotherapy using anti-CD45 monoclonal antibodies to deliver radiation to murine hematolymphoid tissues and human myeloid leukemia

Radioimmunotherapy (RIT) for treatment of hematologic malignancies frequently fails because of disease recurrence. We therefore conducted pretargeted (P)RIT studies to augment the efficacy in mice of therapy using a pretargeted anti-human (h)CD45 antibody (Ab)-streptavidin (SA) conjugate followed by a biotinylated clearing agent and radiolabeled 1,4,7,10-tetraazacylodode cane N,N',N",N'''-tetraacetic (DOTA)-biotin. Tumor-to-blood ratios at 24 hours were 20:1 using pretargeted anti-hCD45 RIT and <1:1 with conventional RIT. In vivo imaging studies confirmed that the PRIT approach provided high-contrast tumor images with minimal blood-pool activity, whereas directly labeled anti-hCD45 Ab produced distinct tumor images but the blood pool retained a large amount of labeled Ab for a prolonged time. Therapy experiments showed that (90)Y-DOTA-biotin significantly prolonged survival of mice treated with pretargeted anti-hCD45 Ab-SA compared with mice treated with conventional RIT using (90)Y-labeled anti-hCD45 Ab at 200 muCi. Because human CD45 antigens are confined to xenograft tumor cells in this model, and all murine tissues are devoid of hCD45 and will not bind anti-hCD45 Ab, we also compared one-step and PRIT using an anti-murine (m)CD45 Ab where the target antigen is present on normal hematopoietic tissues. After 24 h, 27.3% +/- 2.8% of the injected dose of activity was delivered per gram (% ID/g) of lymph node using (131)I-A20-Ab compared with 40.0 +/- 5.4% ID/g for pretargeted (111)In-DOTA-biotin. These data suggest that pretargeted methods for delivering RIT may be superior to conventional RIT when targeting CD45 for the treatment of leukemia and may allow for the intensification of therapy, while minimizing toxicities.

Diagnostic and therapeutic evaluation of 111In-vinorelbine-liposomes in a human colorectal carcinoma HT-29/luc-bearing animal model

Colorectal carcinoma is a highly prevalent and common cause of cancer in Taiwan. There is still no available cure for this malignant disease. To address this issue, we applied the multimodality of molecular imaging to explore the efficacy of diagnostic and therapeutic nanoradiopharmaceuticals in an animal model of human colorectal adenocarcinoma [colorectal cancer (CRC)] that stably expresses luciferase (luc) as a reporter. In this study, an in vivo therapeutic efficacy evaluation of dual-nanoliposome (100 nm in diameter) encaged vinorelbine (VNB) and (111)In-oxine on HT-29/luc mouse xenografts was carried out. HT-29/luc tumor cells were transplanted subcutaneously into male SCID mice. Multimodality of molecular imaging approaches including bioluminescence imaging (BLI), gamma scintigraphy, whole-body autoradiography (WBAR) and in vivo tumor growth tracing, histopathology and biochemistry/hematology analyses were applied on xenografted SCID mice to study the treatments with 6% polyethylene glycol (PEG) of (111)In-NanoX/VNB-liposomes. In vivo tumor growth tracing and BLI showed that tumor volume could be completely inhibited by the combination therapy with (111)In-VNB-liposomes and by chemotherapy with NanoX/VNB-liposomes (i.e., without Indium-111) (P<.01). The nuclear medicine images of gamma scintigraphy and WBAR also revealed the conspicuous inhibition of tumor growth by the combination therapy with (111)In-VNB-liposomes. Animal body weights, histopathology and biochemistry/hematology analyses were used to confirm the safety and feasibility of radiopharmaceuticals. A synergistic therapeutic effect on CRC xenografted SCID mice was proven by combining an Auger electron-emitting radioisotope (Indium-111) with an anticancer drug (VNB). This study further demonstrates the beneficial potential applications of multimodality molecular imaging as part of the diagnostic and therapeutic approaches available for the evaluation of new drugs and other strategic approaches to disease treatment.

Bifunctional coupling agents for radiolabeling of biomolecules and target-specific delivery of metallic radionuclides

Receptor-based radiopharmaceuticals are of great current interest in molecular imaging and radiotherapy of cancers, and provide a unique tool for target-specific delivery of radionuclides to the diseased tissues. In general, a target-specific radiopharmaceutical can be divided into four parts: targeting biomolecule (BM), pharmacokinetic modifying (PKM) linker, bifunctional coupling or chelating agent (BFC), and radionuclide. The targeting biomolecule serves as a "carrier" for specific delivery of the radionuclide. PKM linkers are used to modify radiotracer excretion kinetics. BFC is needed for radiolabeling of biomolecules with a metallic radionuclide. Different radiometals have significant difference in their coordination chemistry, and require BFCs with different donor atoms and chelator frameworks. Since the radiometal chelate can have a significant impact on physical and biological properties of the target-specific radiopharmaceutical, its excretion kinetics can be altered by modifying the coordination environment with various chelators or coligand, if needed. This review will focus on the design of BFCs and their coordination chemistry with technetium, copper, gallium, indium, yttrium and lanthanide radiometals.

[Octreotide scintigraphy in thyroid orbitopathy]

INTRODUCTION

Graves' disease, which has an autoimmune basis, is associated with the infiltration of activated lymphocytes into the retrobulbar tissues of the eye. These activated lymphocytes express somatostatin receptors on their surface which mediate the inflammatory response.

OBJECTIVE

To evaluate the efficiency of (111) In-Octreotide scintigraphy in the identification of orbital activity in Graves' disease and the usefulness of treatment with a somatostatin analogue, based on a pre-established protocol within the Nuclear Medicine Department.

METHODS

We studied a group of eighteen patients with symptomatic Graves' ophthalmopathy of between two months and four years duration. We injected 6 mCi of (111) In-Octreotide parenterally, and performed scintigraphy four and twenty-four hours later. Four patients, all in the active phase, showed orbital somatostatin receptors, for which they were treated with lanreotide 60 mg every fifteen days for three months. Patients were reviewed after 3 months treatment with a further scintigraphy and clinical study.

RESULTS

In our study all four treated patients had less than sixteen months of ophthalmopathy, and three responded well to the treatment.

CONCLUSION

Scintigraphy with Octreotide is a useful procedure allowing identification of patients in the active phase of the ophthalmopathy who are likely to respond well to treatment with somatostatin analogues.

Tumor Targeting with Antibody-Functionalized, Radiolabeled Carbon Nanotubes

Single-walled carbon nanotubes (CNT) are mechanically robust graphene cylinders with a high aspect ratio that are comprised of sp(2)-bonded carbon atoms and possessing highly regular structures with defined periodicity. CNT exhibit unique mechanochemical properties that can be exploited for the development of novel drug delivery platforms. We hypothesized that novel prototype nanostructures consisting of biologics, radionuclides, fluorochromes, and CNT could be synthesized and designed to target tumor cells.

METHODS

Tumor-targeting CNT constructs were synthesized from sidewall-functionalized, water-soluble CNT platforms by covalently attaching multiple copies of tumor-specific monoclonal antibodies, radiometal-ion chelates, and fluorescent probes. The constructs were characterized spectroscopically, chromatographically, and electrophoretically. The specific reactivity of these constructs was evaluated in vitro by flow cytometry and cell-based immunoreactivity assays and in vivo using biodistribution in a murine xenograft model of lymphoma.

RESULTS

A soluble, reactive CNT platform was used as the starting point to build multifunctional constructs with appended antibody, metal-ion chelate, and fluorescent chromophore moieties to effect specific targeting, to carry and deliver a radiometal-ion, and to report location, respectively. These nanoconstructs were found to be specifically reactive with the human cancer cells they were designed to target in vivo in a model of disseminated human lymphoma and in vitro by flow cytometry and cell-based immunoreactivity assays versus appropriate controls.

CONCLUSION

The key achievement in these studies was the selective targeting of tumor in vitro and in vivo by the use of specific antibodies appended to a soluble, nanoscale CNT construct. The ability to specifically target tumor with prototype-radiolabeled or fluorescent-labeled, antibody-appended CNT constructs was encouraging and suggested further investigation of CNT as a novel delivery platform.

Evaluation of CD20, CD22, and HLA-DR Targeting for Radioimmunotherapy of B-Cell Lymphomas

Despite the promise of radioimmunotherapy using anti-CD20 antibodies (Ab) for the treatment of relapsed patients with indolent non-Hodgkin lymphoma (NHL), most patients treated with conventional doses of (131)I-tositumomab or (90)Y-ibritumomab eventually relapse. We did comparative assessments using conventional radioimmunotherapy targeting CD20, CD22, and HLA-DR on human Ramos, Raji, and FL-18 lymphoma xenografts in athymic mice to assess the potential for improving the efficacy of radioimmunotherapy by targeting other NHL cell surface antigens. Results of biodistribution studies showed significant differences in tumor localization consistent with variable antigenic expression on the different lymphoma cell lines. Interestingly, the radioimmunoconjugate that yielded the best tumor-to-normal organ ratios differed in each tumor model. We also explored administering all three (111)In-1,4,7,10-tetra-azacylododecane N,N',N'',N'''-tetraacetic acid antibodies in combination, but discovered, surprisingly, that this approach did not augment the localization of radioactivity to tumors compared with the administration of the best single radiolabeled Ab alone. These data suggest that conventional radioimmunotherapy using anti-CD20, anti-HLA-DR, or anti-CD22 Abs is effective when used singly and provides targeted uptake of radiolabel into the tumor that is dependent on the levels of antigen expression. Improvements in tumor-to-normal organ ratios of radioactivity cannot be achieved using directly labeled Abs in combination but may be afforded by novel pretargeting methods.

In vivo tracking of macrophage activated killer cells to sites of metastatic ovarian carcinoma

Radio-labelling of blood cells is an established technique for evaluating in vivo migration of normal cells to sites of pathology such as infection and haemorrhage. A limitation of cellular immunotherapies to induce anti-tumour responses is in part due to the uncertain ability of cellular effectors to reach their intended target. We extended the approach of cell radiolabelling to accurately examine the in vivo distribution of cellular immunotherapy with ex-vivo macrophage activated killer (MAK) cells. We describe the use of two methods of cell labelling for tracking the destination of autologous-derived macrophage activated killer (MAK) cells linked to the bi-specific antibody MDX-H210 delivered either by intravenous (i.v.) or intraperitoneal (i.p.) injection in ten patients with peritoneal relapse of epithelial ovarian carcinoma. Our results demonstrate the feasibility of generating high numbers and purity of GMP quality MAK cells, which can be radiolabelled with (18)F-FDG or (111)In-oxime. MAK cell administration produced minimal infusional toxicity and demonstrated a reproducible pattern of in vivo distribution and active in vivo tracking to sites of known tumour following 8 of 16 i.v. infusions or 4 of 6 i.p. infusions. However, the leakage of (18)F-FDG limited the ability to confidently confirm the tracking of MAK cells to tumour in all cases and improved PET labels are required. The addition of MDX-H210 bispecific antibody did not alter the distribution of cells to tumour sites, but did accelerate the clearance of i.v. administered MAK cells from the pulmonary circulation. This data demonstrates that cellular cancer immunotherapies may be successfully delivered to the sites of active tumour following either i.v. or i.p. injection in a proportion of patients with metastatic cancer. Incorporation of tracking studies in early cycles of cellular immunotherapy may allow selection of patients who demonstrate successful targeting of the immunotherapy for ongoing treatment.

Long-term clearance from small airways decreases with age

The prevalence of respiratory symptoms increases with age. Age has been found to be negatively associated with large airway clearance. The small airways region is considered important for development of airway disease. Clearance after the first 24 h was studied in 46 healthy subjects with a wide age distribution, (mean 42, range 19-81 yrs). All subjects inhaled monodisperse 6 microm Teflon particles labelled with 111In, with an extremely slow inhalation flow (0.05 L.s-1). The particles were mainly deposited in the small conducting airways. Lung retention was measured at 0 and 24 h, and at 7, 14 and 21 days after inhalation. Significant relationships were found for the individual 24 h "large" airway clearance in per cent of initial lung deposition with age, forced expiratory volume in one second and forced vital capacity. Age was negatively associated with "small" airway clearance after 24 h as estimated at 2, 7, 14 and 21 days. Using stepwise linear regression only age remained significantly associated to clearance. In conclusion, small airway clearance over 21 days was found to decrease with age. This might be one factor associated with the high prevalence of respiratory symptoms associated among the elderly.

Detection of 111In-oxine-labeled bone marrow stromal cells after intravenous or intralesional administration in chronic paraplegic rats

Recent studies suggested that bone marrow stromal cells (BMSC) may have a therapeutic role in the treatment of paraplegia secondary to severe spinal cord injury (SCI). For this reason, we have studied the possibility of using nuclear medicine imaging techniques to evaluate the permanency and migration of BMSC after transplantation procedures in chronic paraplegic Wistar rats. After intravenous administration of 111In-oxine-labeled BMSC, gammagraphic images showed that the activity distributed all over the organism, but in the spinal cord only scarce activity was identified. When 111In-oxine-labeled BMSC were injected within the traumatic centromedullary cavity of paraplegic animals, the gammagraphic images showed persistent activity in the lesion zone, without any activity migrating to the rest of the organism, at least during the whole time of the study (10 days after transplantation procedures). Our results show the utility of 111In labeling for to know the permanency and distribution of BMSC after grafting procedures, and suggest the convenience of the intralesional administration of BMSC, instead of the intravenous administration, in the treatment of chronic traumatic paraplegia.

Long-term clearance from small airways in patients with cystic fibrosis

Impaired mucociliary clearance is a hallmark of cystic fibrosis (CF). Early morphological changes first appear in the small airways. Lung clearance was investigated in 11 young CF adults with mild-to-moderate lung disease using a method depositing particles mainly in the small airways. Radiolabelled Teflon particles (6 microm) were inhaled with an extremely slow inhalation flow, 0.05 L x s(-1). Lung retention was measured immediately following inhalations and, on four occasions up to 21 days. The results were compared with data from healthy subjects. The lung retention at 24 h in % of deposition was 67% (95% confidence interval 58-76) in the CF patients, compared to 48% (42-53) in the healthy subjects. Clearance on days 1-7 was larger in the CF patients, 22% (15-29) compared to the healthy subjects, 14% (12-16). No difference was observed between the CF patients and the healthy subjects in the slow clearance phase at day 7 to day 21, representing small airway clearance. Impaired mucociliary clearance in CF patients results in increased 24-h retention and a prolonged rapid clearance phase. The results of the study do not support the current authors' hypothesis that clearance from small airways is slower in cystic fibrosis patients compared to healthy subjects. Furthermore, the data suggest that mucociliary transport is not the dominant clearance mechanism in small airways.

Tumor targeting properties of indium-111 labeled genetically engineered Fab' and F(ab')2 constructs of chimeric tumor necrosis treatment (chTNT)-3 antibody

Genetic engineering techniques have allowed the construction of Fab' and F(ab')2 constructs of chimeric tumor necrosis treatment antibody (chTNT-3), a chimeric monoclonal antibody (MAb) that targets necrotic regions of solid tumors. The purpose of this study is to evaluate the in vitro and in vivo properties of Fab' and F(ab')2 constructs radiolabeled with indium-111 (111In) using diethylentriamine pentaacetic acid (DTPA) conjugation to develop a clinically useful imaging agent for the detection of necrosis in solid tumors. Optimization of the MAb-to-DTPA ratio showed that a 1:2 ratio gave the best immunoreactivity while providing good radiolabeling efficiency and high specific activity for all three DPTA conjugates. In addition, 111In-labeled Fab' and F(ab')2 conjugates were found to have faster whole body clearance times and better biodistribution profiles compared to parental 111In-labeled chTNT-3 in tumor-bearing mice. Although radiolabeled Fab' and F(ab')2 constructs showed lower tumor uptake than radiolabeled chTNT-3, biodistribution results showed that these constructs had significantly lower uptake in liver, spleen, and other normal organs (except the kidney), and therefore had higher tumor-to-organ ratios. In addition, a comparison of all derivatives showed that the F(ab')2 reagent gave the best results in tumor imaging studies. These results demonstrate that stable, a genetically engineered F(ab')2 construct can be successfully radiolabeled with 111In to produce potential imaging reagents for the imaging and monitoring of tumor necrosis.

[Radioisotope therapy with somatostatin analogues in neuroendocrine tumours (case report)]

Restricted number of neuroendocrine tumors (NET) shows overexpression of somatostatin receptors. Therefore, long-acting somatostatin analogues are used in diagnosis and treatment of those tumors. Here we present our first case of NET, localized in pancreas treated with DOTA-D-Phe 1-Tyr 3-octreotide (DOTATATE), for receptor-mediated radioisotope therapy. DOTATATE is a newly developed somatostatin analogue labeled with beta-emitter yttrium 90 (90Y) and beta, gamma-emitter lutetium 177 (177Lu). A 34-year old woman was suffering from several years gastrointestinal symptoms. NET of the pancreas with multiple metastases into the liver was diagnosed based on histopatological, biochemical and radiological tests. First, she had chemiotherapy (leucovorin, 5-FU, cisplatin), however there was any positive effects of this therapy. Next, she received four single doses of 90Y DOTATATE at 4-6- week intervals, yielding a cumulative dose of 7.4 GBq/m2. During the 4th cycle the Lu-177 DOTATATE was additionally administered. As a renal protection i.v. infusion of amino acid solution were used during the treatment sessions. To date, patient has shown partial remission with reduction of tumor masses. We observed spectacular clinical, biochemical and radiological improvement. Radioisotope therapy could be a powerful and promising method of treatment at least in patients who had no other treatment option.

In vivo distribution and fractionation of indium in rats after subcutaneous and oral administration of [114mIn]InAs

Two in vivo experiments were carried out in this study. In the first experiment five rats were given two subcutaneous injections of [(114m)In]InAs. Major sites of accumulation were spleen, liver and kidney. The intracellular distribution of indium was examined by differential centrifugation. The cytoplasmic fraction contained most of the indium activity followed by the mitochondrial fraction. Both outcomes are in close agreement with the results obtained in previous studies. Chromatographic separations on a preparative size exclusion column were carried out. It was shown that indium was mostly bound to high molecular mass compounds in serum and in the cytoplasmic fraction of spleen, liver and kidney. In a second experiment five rats were given four oral doses of [(114m)In]InAs over a short period. Prior to this experiment the in vitro solubility of cold InAs in simulated gastric fluid (SGF) and simulated intestinal fluid (SIF) was determined using graphite furnace atomic absorption spectroscopy. In the case of the SGF only 1.3% of an InAs suspension dissolved after 48 hours incubation at 37 degrees C. InAs was not soluble in SIF. Uptake of InAs after oral administration was minimal (<1%). Due to incomplete removal of traces of [(114m)In]InAs from the gastrointestinal tract, it was impossible to calculate accurately the in vivo distribution over the different organs. As the uptake and consequently the activity in the organs were very low, no further chromatographic separations could be carried out. Considering this very low uptake, it can be concluded that InAs will not accumulate in the body after oral exposure.

Increased cell death after therapy with an Arg-Gly-Asp-linked somatostatin analog

Receptor-targeted scintigraphy and radionuclide therapy with radiolabeled somatostatin analogs are successfully applied for somatostatin receptor-positive tumors. The synergistic effects of an apoptosis-inducing factor, for example, the Arg-Gly-Asp (RGD) motif, can increase the radiotherapeutic efficacy of these peptides. Hence, the tumoricidal effects of the hybrid peptide RGD-diethylaminetriaminepentaacetic acid (DTPA)-Tyr3-octreotate (cyclic[c](Arg-Gly-Asp-D-Tyr-Asp)-Lys(DTPA)-D-Phe-c(Cys-Tyr-D-Trp-Lys-Thr-Cys)-Thr), hereafter referred to as RGD-DTPA-octreotate, were evaluated in comparison with those of RGD (c(Arg-Gly-Asp-D-Tyr-Asp)) and Tyr3-octreotate (D-Phe-c(Cys-Tyr-D-Trp-Lys-Thr-Cys)-Thr).

METHODS

The therapeutic effects of RGD-111In-DTPA-octreotate, 111In-DTPA-RGD, and 111In-DTPA-Tyr3-octreotate were investigated with various cell lines by use of a colony-forming assay, and caspase-3 activity was also determined.

RESULTS

Tumoricidal effects were found with 111In-DTPA-RGD, 111In-DTPA-Tyr3-octreotate, and RGD-111In-DTPA-octreotate, in order from least effective to most effective. Also, the largest increase in caspase-3 levels was found with RGD-111In-DTPA-octreotate.

CONCLUSION

RGD-111In-DTPA-octreotate has more pronounced tumoricidal effects than 111In-DTPA-RGD and 111In-DTPA-Tyr3-octreotate, because of increased apoptosis, as indicated by increased caspase-3 activity.

Amplification targeting: a modified pretargeting approach with potential for signal amplification-proof of a concept

Conventional nuclear medicine imaging with large radiolabeled molecules such as antitumor antibodies suffers from slow localization and clearance. Pretargeting is under active investigation as an alternative using either (strept)avidin/biotin, bispecific antibodies, or oligomers. However, only the use of oligomers such as phosphorodiamidate morpholinos (MORFs) in pretargeting offers the potential of signal amplification at the target. Amplification targeting is a multistep procedure with the potential to greatly improve target localization of radioactivity (and eventually drugs) through the intermediate use of polymers conjugated with multiple copies of oligomers.

OBJECTIVE

This study was conducted to prove the concept in vivo in tumored mice of amplfication targeting.

METHODS

Nude mice bearing LS174T tumors received in order: the anti-CEA antibody MN14 conjugated with MORF, a polymer conjugated with multiple copies of complementary MORFs (cMORFs), and, finally, (99m)Tc-MORF.

RESULTS

In tumored animals, dual radiolabels ((99m)Tc and (111)In) were used to demonstrate that, after 18 h, about 25% of antibody MORFs in tumor were targeted with polymeric cMORFs and, after 3 h, about 12% of the polymeric cMORFs in tumor were targeted with (99m)Tc-MORF. Therefore, hybridization in tumor in both cases (i.e., polymeric cMORF to antibody MORF and radiolabeled MORF to polymeric cMORF) was surprisingly efficient given the barriers to targeting in vivo and the competition between targeting and clearance. Moles of radiolabeled MORF accumulating in tumor were more than tripled for study animals receiving all 3 injections compared with control animals not receiving the antibody or the polymer. Furthermore, MORF expression (on antibody) and cMORF expression (on polymer) were rapidly lost in normal organs such as liver, spleen, and kidneys but not in tumor, thus improving the target-to-nontarget ratios.

CONCLUSION

Although signal amplification has not yet been convincingly demonstrated and amplification targeting will require further studies for optimization, the concept has now been shown to be feasible.

Radioimmunotherapy of Human Colon Carcinoma Xenografts Using a213Bi-Labeled Domain-Deleted Humanized Monoclonal Antibody

The data presented within this paper is the first report of a humanized domain-deleted monoclonal antibody (HuCC49DeltaCH2) to be utilized in a radioimmunotherapeutic (RIT) application with 213Bi. An initial study indicated that 111In-HuCC49DeltaCH2 targets the subcutaneously implanted human colon carcinoma xenograft, LS-174T, when injected via a peritoneal route. The HuCC49DeltaCH2 was then radiolabeled with 213Bi, an alpha-emitting radionuclide with a half-life of 45.6 minutes, and evaluated for therapeutic efficacy. Dose titration studies indicated that a single dose of 500-1000 microCi, when injected by an intraperitoneal route, resulted in the growth inhibition or regression of the tumor xenograft. The radioimmunotherapeutic effect was found to be dose-dependent. Specificity of the therapeutic efficacy was confirmed in a subsequent experiment with athymic mice bearing TAG-72 negative MIP (human colorectal) xenografts. A preliminary study was also performed to assess a multiple-dose administration of 213Bi-HuCC49DeltaCH2. Doses (500 microCi) were administered at 14-day intervals after tumor implantation. A reduction in volume and/or delay in tumor growth was evident following the second and third injections of 213Bi-HuCC49DeltaCH2. As further validation of the use of 213Bi-HuCC49DeltaCH2 for RIT, a study using 131I was conducted. The overall survival of mice receiving 213Bi-HuCC49DeltaCH2 was greater than those that received 131I-HuCC49DeltaCH2.

Pharmacokinetics and biodistribution of [111In]-avidin and [99mTc]-biotin-liposomes injected in the pleural space for the targeting of mediastinal nodes

Pharmacokinetics and mediastinal node uptake of [111In]-avidin and [99mTc]-biotin-liposomes following either intrapleural (pleural) or intraperitoneal (ip) injection were determined using scintigraphic imaging. Biodistribution results of [111In]-avidin at 44 h showed 3.3% uptake in mediastinal nodes by pleural injection vs 1.3% with ip injection. Mediastinal node accumulation with [99mTc]-biotin-liposomes was not different between injections (0.6% ip vs 0.5% pleural). This study demonstrates the potential of the pleural route as a technique for mediastinal node targeting using the avidin/biotin-liposome system.

Radiolabeling of magnetic targeted carriers (MTC) with indium-111

Magnetic targeted carriers (MTC) are magnetically susceptible microparticles that can be physically targeted to a specific site. MTC were radiolabeled with (111)In using three different methods. Reaction parameters were investigated in order to optimize the final properties of the labeled MTC. The reaction parameters studied were chelation agent, chelation time, temperature, radiolabeling time, solvent, and molar ratios. A 97.7 +/- 0.9% binding efficiency and plasma stability of 92.6 +/- 0.1% over 7 days were achieved when 2-p-aminobenzyl-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetra-acetic acid (ABz-DOTA) was used as the chelating agent. A preliminary animal biodistribution study confirmed the binding stability. The labeling of the MTC with the diagnostic isotope (111)In was undertaken to allow for quantitative imaging and dosimetry prior to therapy with (90)Y radiolabeled MTC.

Biodistribution and pharmacokinetics of 111In-dTPA-labelled pegylated liposomes after intraperitoneal injection

The biodistribution and pharmacokinetics of 111In-DTPA-labelled pegylated liposomes (IDLPL) and unencapsulated 111In-DTPA administered by the intraperitoneal (i.p.) and i.v. routes in non-tumour-bearing mice were compared. Mice received i.p. or i.v. injections of 0.37 MBq 111In-DTPA either encapsulated in liposomes or as an unencapsulated agent. A variety of tissues were dissected from 5 min to 192 h to determine the biodistribution and pharmacokinetics. Injection of IDLPL via the i.p. route caused a 74-fold increase in the area under the concentration (AUC) versus time curve in the peritoneum compared to unencapsulated 111In-DTPA. Similarly, the AUC for all the intra-abdominal tissues was increased significantly (20-427-fold). When i.p. IDLPLs were compared directly with i.v. IDLPLs, more modest changes were seen. There were increases in AUC for peritoneum (1.4-fold), ovary (1.3-fold), stomach (2.9-fold), pancreas (3.6-fold). small intestine (1.5-fold). colon (1.2-fold), gallbladder (5.1-fold) and adrenal gland (2.1-fold). These data support the development of i.p. liposomal chemotherapy for the treatment of intraperitoneal malignant disease.

Side-to-side symmetry of radioprotein transfer from tissue space to systemic vasculature following subcutaneous injection in normal subjects and patients with breast cancer

Quantitative lymphoscintigraphy can be used for investigation of unilateral lymphatic disease of the limbs, such as breast cancer-related lymphoedema (BCRL). Previous studies have compared lymphatic function in the affected limb with that in the unaffected contralateral limb. This study aims to confirm that the assumption of pre-morbid symmetry, never previously demonstrated, is valid. A dual-isotope technique, with bilateral subcutaneous hand injection of polyclonal human immunoglobulin G (HIgG) labelled with either technetium-99m or indium-111, was performed on a total of 37 subjects. The use of two different labels, one for each limb, enabled comparison not only of the rate of clearance from the injection depot, but also of the rate of appearance in venous blood. Results demonstrate clear symmetry between the two arms with respect to both depot clearance and blood appearance rates, as well as the coupling between these two variables. In unilateral lymphatic disease, results of quantitative lymphoscintigraphy should be expressed in relation to the normal arm rather than to an independent control population.

Assessment of the tissue distribution of transplanted human endothelial progenitor cells by radioactive labeling

BACKGROUND

Transplantation of endothelial progenitor cells (EPCs) improves vascularization and left ventricular function after experimental myocardial ischemia. However, tissue distribution of transplanted EPCs has not yet been monitored in living animals. Therefore, we tested whether radioactive labeling allows us to detect injected EPCs.

METHODS AND RESULTS

Human EPCs were isolated from peripheral blood, characterized by expression of endothelial marker proteins, and radioactively labeled with [111In]indium oxine. EPCs (106) were injected in athymic nude rats 24 hours after myocardial infarction (n=8) or sham operation (n=8). Scintigraphic images were acquired after 1, 24, 48, and 96 hours after EPC injection. Animals were then killed, and specific radioactivity was measured in different tissues. At 24 to 96 hours after intravenous injection of EPCs, approximately 70% of the radioactivity was localized in the spleen and liver, with only approximately 1% of the radioactivity identified in the heart of sham-operated animals. After myocardial infarction, the heart-to-muscle radioactivity ratio increased significantly, from 1.02+/-0.19 in sham-operated animals to 2.03+/-0.37 after intravenous administration of EPCs. Injection of EPCs into the left ventricular cavity increased this ratio profoundly, from 2.69+/-1.54 in sham-operated animals to 4.70+/-1.55 (P<0.05) in rats with myocardial infarction. Immunostaining of cryosections from infarcted hearts confirmed that EPCs homed predominantly to the infarct border zone.

CONCLUSIONS

Although only a small proportion of radiolabeled EPCs are detected in nonischemic myocardium, myocardial infarction increases homing of transplanted EPCs in vivo profoundly. Radiolabeling might eventually provide an useful tool for monitoring the fate of transplanted progenitor cells and for clinical cell therapy.

Radiolabeled monoclonal antibodies specific to the extracellular domain of prostate-specific membrane antigen: preclinical studies in nude mice bearing LNCaP human prostate tumor

Prostate-specific membrane antigen (PSMA), a transmembrane glycoprotein, is highly expressed by virtually all prostate cancers. PSMA is also expressed on the tumor vascular endothelium of virtually all solid carcinomas and sarcomas but not on normal vascular endothelium. PSMA is currently the focus of several diagnostic and therapeutic strategies. We have previously reported on the radiolabeling and in vitro binding properties of monoclonal antibodies (mAbs) (J415, J533, and J591) that recognize and bind with high affinity to the extracellular domain of PSMA (PSMA(ext)). This article reports on the in vivo behavior and tumor uptake of (131)I- and (111)In-labeled antiPSMA(ext) mAbs (J415, J533, and J591) and their potential utility for radioimmunotherapy.

METHODS

In nude mice bearing PSMA-positive human LNCaP tumors, the pharmacokinetics, biodistribution, and tumor uptake of these antibodies was compared with (111)In-7E11 mAb, specific to the intracellular domain of PSMA (PSMA(int)). Autoradiographic studies were done to identify intratumoral distribution of radiolabeled mAbs.

RESULTS

With (131)I-labeled antibodies, the net tumor retention of radioactivity by day 6 was significantly higher with J415 (15.4% +/- 1.1%) and 7E11 (14.5% +/- 1.7%) than with J591 (9.58% +/- 1.1%). By contrast, the tumor uptake of (111)In-1,4,7,10-tetraazacyclododecane-N,N',N", N"'-tetraacetic acid-labeled J415 and J591 gradually increased with time and was quite similar to that of 7E11. In addition, the blood clearance of (111)In-labeled J415 and J591 antibodies was relatively faster than that of radiolabeled 7E11. As a consequence, the tumor-to-blood ratios with J415 and J591 were higher than that of 7E11. The localization of radiolabeled anti-PSMA(ext) antibodies in PSMA-positive LNCaP tumors was highly specific because the tumor uptake of (131)I-labeled J415 and J591 was more than twice that of a nonspecific antibody. Furthermore, the tumor uptake of (131)I-J591 was almost 20 times higher in PSMA-positive LNCaP tumors than in PSMA-negative PC3 and DU145 tumor xenografts. Autoradiographic studies suggested that 7E11 (anti-PSMA(int)) distinctly favors localization to areas of necrosis whereas J415 and J591 (anti-PSMA(ext)) demonstrated a distinct preferential accumulation in areas of viable tumor.

CONCLUSION

These results clearly demonstrate that PSMA-specific internalizing antibodies such as J415 and J591 may be the ideal mAbs for the development of novel therapeutic methods to target the delivery of beta-emitting radionuclides ((131)I, (90)Y, and (177)Lu) for the treatment of PSMA-positive tumors. In addition, because J591 and J415 mAbs are specific to PSMA(ext), thus targeting viable tumor, these immunoconjugates are better candidates for targeted radioimmunotherapy than are antibodies targeting PSMA(int).

Pretargeted radioimmunotherapy (PRIT) using an antibody-streptavidin fusion protein in non-Hodgkin's lymphoma

Pretargeted radioimmunotherapy (PRIT) decreases the amount of time that radioactivity non-selectively circulates. Our PRIT approach is a multi-step method in which a monoclonal antibody is used to target streptavidin to a tumor-associated antigen and biotin is then used to target 90Y to the streptavidin. A genetically engineered antibody streptavidin fusion construct was used to target tumor in a patient with non-Hodgkin's lymphoma. Impressive localization of 90Y to known and previously unknown areas of adenopathy was observed, thus demonstrating that a genetically engineered fusion protein can selectively target lymphoma cells as part of a clinically meaningful PRIT strategy.

Reduction of kidney uptake in radiometal labeled peptide linkers conjugated to recombinant antibody fragments. Site-specific conjugation of DOTA-peptides to a Cys-diabody

Arano and co-workers (Arano et al. (1999) Cancer Res. 59, 128-134) have synthesized peptides with an N-terminal radioiodinated hippuric acid and a C-terminal lysine linked to antibody fragments via the epsilon-amino group of lysine that show reduced kidney uptake compared to antibody fragments directly radioiodinated. This approach takes advantage of the lysine specific carboxypeptidase activity of the kidney brush border enzymes that cleave off the radiolabeled peptide linker from the antibody fragment prior to uptake by proximal tubule cells. On the basis of their approach, we have synthesized a tetrapeptide with an N-terminal DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) and a C-terminal (N(epsilon)-maleoyl)lysine that was site-specifically conjugated to an anti-CEA diabody (Yazaki et al. (2001) Bioconjugate Chem. 12, 220-228) that was engineered to contain a C-terminal cysteine (Cys-diabody). Biodistributions of the In-111-radiolabeled conjugate in nude mice show significantly reduced kidney uptake (a maximum of 82%ID/g at 6 h) compared to In-111 radiolabeled DOTA-diabody (184%ID/g at 6 h) in which DOTA was conjugated to endogenous lysine residues using DOTA-active ester chemistry. To further reduce kidney uptake, a homologous compound with a C-terminal (N(epsilon)-amino-1,6-hexane-bis-vinyl sulfone)lysine was synthesized and site-specifically conjugated to the Cys-diabody. Biodistributions of this In-111-labeled conjugate reduced kidney uptake to 54%ID/g at 6 h. To explore the effect of the relative positions of the chelate vs the cys-diabody on kidney uptake, we also synthesized a tetrapeptide with an N-terminal bromoacetate for conjugation to Cys-diabody and a C-terminal (N(epsilon)-amidino-propyl-3-thio-vinylsulfonyl-DO3A)lysine. This peptide essentially reverses the positions of the chelate and Cys-diabody attachment points on the peptide, while retaining the linker length on the epsilon-amino group of the lysine. In this case, biodistributions of the In-111-radiolabeled conjugate in nude mice showed high kidney uptake (189%ID/g at 6 h), comparable to that obtained with the In-111-radiolabeled active ester conjugated DOTA-diabody (184%ID/g at 6 h). We conclude that the peptide linker strategy of Arano and co-workers to reduce kidney uptake can be successfully applied to chelate/radiometal complexes and requires that the chelate/radiometal be located at the N-terminus of the peptide and the antibody fragment attachment site on the epsilon-amino group of the lysine. Furthermore, we demonstrated a role for the attachment chemistry to the epsilon-amino group of the lysine on the magnitude of kidney uptake.

Clinical utility of indium 111-capromab pendetide immunoscintigraphy in the detection of early, recurrent prostate carcinoma after radical prostatectomy

BACKGROUND

Despite the ability of radical prostatectomy to eradicate prostate carcinoma, biochemical evidence of recurrent prostate carcinoma may be seen in approximately 40% of patients 15 years after they undergo surgery. Localization of recurrent disease after radical prostatectomy is difficult and may greatly influence subsequent clinical management. The authors examined the utility of indium 111 ((111)In)-capromab pendetide immunoscintigraphy to detect recurrent prostate carcinoma radiographically in men with early biochemical evidence of failure (serum prostate specific antigen [PSA] < or = 4.0 ng/mL) and assessed the minimum serum PSA level necessary for imaging recurrent disease.

METHODS

Between May 1987 and August 1995, 255 hormone-naïve men with a mean (+/- standard deviation) age of 65 years +/- 7 years who underwent radical prostatectomy for clinically localized prostate carcinoma were followed without adjuvant therapy until early PSA recurrence in this multicenter study. Preoperatively, all patients had negative bone scans and pathologically negative lymph nodes, and they did not undergo hormonal ablation, chemotherapy, or radiation therapy preoperatively or postoperatively until the (111)In-capromab pendetide scan was performed. All men in this study had postoperative serum PSA levels < or = 4.0 ng/mL at the time of radionuclide imaging. All men underwent imaging with the capromab pendetide scan to localize recurrent disease, and charts were reviewed to document clinical evidence of recurrence.

RESULTS

Pathologic findings included mean Gleason scores of 6.7 +/- 1.2; pathologic tumors classified as pT2a (18%), pT2b (26%), pT3a (38%), pT3b (16%), and pT4a (2%); a pathologic lymph node status of pN0 (100%); positive surgical margins (44%); and perineural invasion (42%). Capromab pendetide uptake was seen in 72% of 255 men throughout a range of patients' postoperative serum PSA levels (0.1-4.0 ng/mL), with 31% of men having local uptake (prostatic fossa) only. Of 151 men who underwent additional imaging studies, 16 of 139 men (12%) and 15 of 92 men (16%) showed evidence of recurrent disease by bone scintigraphy and computed tomography scans, respectively. Gleason score, pathologic stage, perineural invasion, and margin status were not correlated significantly with the (111)In-capromab pendetide scan.

CONCLUSIONS

Capromab pendetide imaging can localize early PSA recurrence and may guide appropriate treatment after patients undergo radical prostatectomy. No minimum serum PSA value was needed to potentially detect radiographic disease after surgery. Further confirmatory studies and long-term follow-up of this cohort documenting response to salvage therapy are needed to validate these imaging findings.

Application of extracorporeal immunoadsorption to reduce circulating blood radioactivity after intraperitoneal administration of indium-111-HMFG1-biotin

BACKGROUND

Extracorporeal immunoadsorption (ECAT) is a method of reducing activity in radiosensitive organs by removing excess monoclonal antibodies (MAbs) from the blood. Previously, the authors experimentally evaluated ECAT based on the avidin-biotin concept after intravenous administration of radioimmunoconjugates. The aim of the current study was to determine whether ECAT could be used to reduce activity after intraperitoneal (i.p.) administration of indium-111((111)In)-HMFG1-biotin in rats, and to compare the pharmacokinetics of (111)In-HMFG1 with or without attached biotin after i.p. injection.

METHODS

HMFG1, a murine immunoglobulin G(1) MAb that recognizes an epitope on the polymorphic epithelial mucin (PEM) antigen, was labeled with (111)In and then biotinylated. ECAT was explored from unseparated blood using an avidin-agarose adsorption column. Thirty rats were used as controls and 13 underwent ECAT. The whole-body (WB), blood, and organ activity were monitored.

RESULTS

The binding capacity of (111)In-HMFG1-biotin to avidin was high. Biotinylation did not enhance the excretion of HMFG1. When ECAT was employed, the WB and blood radioactivity were reduced by 35-40% (P < 0.05) and 75--86% (P < 0.01), respectively. After the completion of ECAT, the activity uptake in organs was significantly decreased.

CONCLUSIONS

ECAT was successfully applied after i.p. injection of the (111)In-HMFG-biotin MAb to reduce the radioactivity in the WB, blood, and radiosensitive organs. Due to redistribution of the radiolabeled MAbs during and after the completion of ECAT, the adsorption may have been prolonged or repeated. Biotinylation did not significantly change the biodistribution of the (111)In-HMFG1 in rats after intraperitoneal injection.

A comparison of intravascular source designs based on the beta particle emitter 114mIn/114In. Line source versus stepping source

BACKGROUND

Catheter-based intravascular brachytherapy (IVB) sources of the next generation will have to meet high demands in terms of miniaturization, flexibility, safety, reliability, costs and versatility. The radionuclide pair 114mIn/114In (half-life 49.51 days, maximum beta energy 2.0 MeV, average beta energy 0.78 MeV) is an attractive beta emitter for application in such a source.

METHODS

Since metallic indium is unfit for the manufacture of a brachytherapy source, the feasibility, safety and dosimetric properties of a design concept comprising a linear array of ceramic In2O3 spheres within a thin-walled, superelastic Ni/Ti capsule are investigated.

RESULTS

Neutron activation of enriched In2O3 spheres yields a specific activity sufficiently high for the manufacture of a stepping source, keeping treatment times limited to a few minutes. Although 114mIn/114In also emits some gamma radiation, the effective doses received by members of the medical staff are an order of magnitude lower than those received from fluoroscopy. The dose distributions about a 40-mm line source and a 5-mm stepping source (outer diameter 0.36 mm) are calculated using MCNP4C. Dose-volume histograms (DVHs) are calculated for the line source (centered and noncentered) and the stepping source (centered) using the geometry of a human coronary artery.

CONCLUSION

The results show that a centered stepping source with optimized dwell times delivers the most homogenous dose within the target volume.

Amplified delivery of indium-111 to EGFR-positive human breast cancer cells

A method is described to amplify the delivery of 111In to human breast cancer cells utilizing a novel human serum albumin-human EGF (HSA-hEGF) bioconjugate substituted preferentially in the HSA domain with multiple DTPA metal chelators for 111In. 111In-DTPA-HSA-hEGF exhibited a lower receptor-binding affinity than 111In-DTPA-hEGF but was rapidly and specifically bound, internalized and translocated to the nucleus in EGFR-positive MDA-MB-468 breast cancer cells. 111In-DTPA-HSA-hEGF was cytotoxic in vitro mainly through the emission of short-range Auger electrons and partially through the effects of the hEGF moiety to MDA-MB-468 cells overexpressing EGFR (1-2 x 10(6) receptors/cell) but not towards MCF-7 breast cancer cells with a 100-fold lower level of EGFR on their surface. The cytotoxicity in vitro against MDA-MB-468 cells of 111In-DTPA-HSA-hEGF substituted with nine DTPA chelators was enhanced 4-fold compared to 111In-DTPA-hEGF monosubstituted with DTPA. Studies are planned to further evaluate 111In-DTPA-HSA-hEGF in vivo as a new imaging and targeted radiotherapeutic agent for breast cancer.

Antiangiogenic therapy with somatostatin receptor-mediated in situ radiation

Tumor growth and the development of metastases require an angiogenic response. Angiogenic vessels uniquely express somatostatin subtype 2 (sst 2) receptors that can transport somatostatin or its analogs into the cell. We hypothesized that radiolabeled somatostatin analogs could inhibit the angiogenic response by selectively destroying proliferating endothelial cells. We evaluated the antiangiogenic effects of 111In-pentetreotide, an sst 2-preferring somatostatin analog in a human vessel model. Disks of human placental vein were embedded in fibrin gels in culture and observed for angiogenic sprouting for 14 days. Vein disks were treated with 111In-pentetreotide (1.5, 15, and 150 microCi/mL) on the day of implantation. Control groups included disks treated with nutrient medium alone, with 111In-chloride, and with unlabeled pentetreotide. The percentage of wells that initiated an angiogenic response and the overall length and density of neovessel sprouts were assessed on Day 14. 111In-pentetreotide treatment did not completely block initiation of the angiogenic response but significantly decreased the growth of neovessels after initiation. Both the receptor-specific Auger electron-induced and nonspecific gamma radiation-mediated effects contributed to the angiotoxicity.

The dynamic in vivo distribution of bone marrow-derived mesenchymal stem cells after infusion

Bone marrow-derived mesenchymal stem cells (MSCs) have the potential to differentiate along different mesenchymal lineages including those forming bone, cartilage, tendon, fat, muscle and marrow stroma that supports hematopoiesis. This differentiation potential makes MSCs candidates for cell-based therapeutic strategies for mesenchymal tissue injuries and for hematopoietic disorders by both local and systemic application. In the present study, rat marrow-derived MSCs were ex vivo culture-expanded, labeled with (111)In-oxine, and infused into syngeneic rats via intra-artery (i.a.), intravenous (i.v.) and intraperitoneal cavity (i.p.) infusions. In addition, for i.a. and i.v. infusions, a vasodilator, sodium nitroprusside, was administered prior to the cell infusion and examined for its effect on MSC circulation. The dynamic distribution of infused MSCs was monitored by real-time imaging using a gamma camera immediately after infusion and at 48 h postinfusion. After 48 h, radioactivity in excised organs, including liver, lungs, kidneys, spleen and long bones, was measured in a gamma well counter and expressed as a percentage of injected doses. After both i.a. and i.v. infusion, radioactivity associated with MSCs was detected primarily in the lungs and then secondarily in the liver and other organs. When sodium nitroprusside was used, more labeled MSCs cleared the lungs resulting in a larger proportion detected in the liver. Most importantly, the homing of labeled MSCs to the marrow of long bones was significantly increased by the pretreatment with vasodilator. These results indicate multiple homing sites for injected MSCs and that the distribution of MSCs can be influenced by administration of vasodilator.

Comparison of clearance of particles inhaled with bolus and extremely slow inhalation techniques

Ten healthy nonsmokers inhaled 6-microm (aerodynamic diameter) Teflon particles labelled with 111In twice, once with the shallow bolus technique (volumetic lung depth 76+/-20 mL ([+/- SD]) and once with the extremely slow inhalation technique (0.05 L/s). The radioactivity in the lungs was measured at 1 and 24 hours as well as at 1, 2, and 3 weeks after both inhalations. The 24-hour lung retention a percentage of lung deposition was significantly lower for the bolus inhalation, 46%+/-9% (+/- SD) than for the extremely slow inhalation, 56%+/-11%. The retention after 21 days as a percentage of the 24-hour retention was 55%+/-9% for the shallow bolus inhalation and 56%+/-10% for the extremely slow inhalation. Also within the subjects, clearance was similar for the 2 modes of inhalation. Deposition of particles inhaled with the 2 modes of inhalation was calculated with 2 model, one being based on Monte (Carlo particle transport together with an asymmetric lung model. Deposition predicted with this model agreed well with the experimental data under the assumption that there are large retained fractions only in small ciliated airways (bronchioli) and not in large ones. For the bolus inhalation, the model predicted 43% to 50% deposition in the bronchial (BB) region of initial lung deposition, 33% to 38% in the bronchiolar (bb) region, and 16% to 22% in the alveolar region. For the extremely slow inhalation, the model predicted 31% to 34% deposition in the BB region, 45% to 47% in the bb region, and 21% to 22% in the alveolar region. In addition, it predicted about the same ratio between bb and alveolar depositions for the 2 modes of inhalation. Thus, both the experimental and theoretical data indicate that the shallow bolus particles to a considerable extent reach both the bb and the alveolar regions and that they do that at about the same extent as the particles inhaled extremely slow. This conclusion is concerning the experimental data based on the assumption that there are no large retained fractions in the BB region. Another interpretation of the similar clearance for the two modes of inhalation is that there are large retained fractions in both the BB and the bb regions and that individual charactristics of clearance of these fractions are of importance rather than the site of deposition.

In vivo distribution and speciation of [114mIn]InCl3 in the Wistar rat

Five Wistar rats were given an intraperitoneal injection of [114mIn]InCl3 during four consecutive days. One hour after the last injection the rats were sacrificed. The in vivo distribution of 114mIn was studied in the blood and in different organs. Differential centrifugation was used to study the distribution in liver, kidney and spleen homogenate. Rat serum, packed cell lysate, urine and the cytosol of liver, kidney and spleen homogenate were examined by size exclusion fast protein liquid chromatography. The results showed that serum accounts for 90% of the indium activity in whole blood. Indium is preferentially accumulated within the liver, spleen and kidney, the highest amount of 114mIn being localised in the cytosolic fraction followed by the mitochondria. Size exclusion experiments showed that, in rat serum, indium is exclusively bound to transferrin. These results differed from earlier in vitro incubation experiments of human serum with 114mIn. It was not possible, from the experiments described herein, to conclude unequivocally whether indium is bound to haemoglobin of packed cell lysate or to another high molecular mass compound. Indium is associated with the high molecular mass fraction in liver, kidney and spleen cytosol; only in kidney are small amounts of 114mIn found in the low molecular mass fraction. The in vivo inhibitory effect of indium on the delta-aminolaevulinic acid dehydratase (ALAD) enzymatic activity in red blood cells and kidney tissue, well documented by other researchers, could not be attributed to direct binding of indium with this enzyme.

Treatment of metastatic renal cell carcinoma with activated autologous macrophages and granulocyte--macrophage colony-stimulating factor

Fifteen patients with progressive metastatic renal cell carcinoma were treated with granulocyte-macrophage colony-stimulating factor and intravenous infusions of activated autologous macrophages (AAMs). The latter were prepared from leukapheresis-separated mononuclear cells cultured in the presence of granulocyte-macrophage colony-stimulating factor, exposed to gamma interferon, and submitted to elutriation to separate AAMs. Three intravenous injections of AAMs were performed within a 2-week interval. This treatment cycle was repeated once or twice, in cases of tumor response or stabilization. Ninety-seven preparations containing a mean 3 x 10(9) AAMs were administered and usually well tolerated. One partial response, eight stabilizations and six progressions were observed. The median time to progression and median overall survival time after inclusion were 7 and 9 months, respectively. The cells injected did not accumulate substantially in tumor lesions, as shown by scintigraphic imaging of indium-111-labeled AAMs. Thus, combined granulocyte-macrophage colony-stimulating factor and AAM treatment was well tolerated and resulted in transitory stabilization (n = 8) or partial regression (n = 1) in 9 of 15 patients.

In vitro and in vivo stability of new multilamellar vesicles

Factors affecting multilamellar vesicles transport to the blood compartment after oral administration to rats were evaluated first in vitro. A high entrapment of protein A was obtained when the vesicles were prepared by shearing a lyotropic lamellar phase composed of soybean phosphatidylcholine, cholesterol and polyoxyethylene alcohol (C12H25(OCH2CH2)4OH) as neutral detergent. In vitro tests showed that these vesicles (spherulites) were stabled in 50% of fetal calf serum, in acidic (pH 3) or basic (pH 10) buffers, in pancreatin but are partially lysed in 20mM bile salts. Oral administration of spherulites entrapping 111In-NTA in fasting rats showed a increase of radioacticivity in blood. This could be explained by passage of some spherulites in the enterocytes.

Biodistribution of radiolabeled adenosylcobalamin in patients diagnosed with various malignancies

OBJECTIVE

To study the biodistribution of a vitamin B12 analog, indium In 111-labeled diethylenetriaminepentaacetate adenosylcobalamin (In 111 DAC), in patients recently diagnosed as having primary or recurrent malignancy.

PATIENTS AND METHODS

Thirty patients (14 women and 16 men) with radiographically or clinically diagnosed breast, lung, colon, sarcomatous, thyroid, or central nervous system malignancies were studied prior to definitive surgery or biopsy. A maximum of 650 microCi (2.2 microg) of In 111 DAC was administered intravenously. Vitamin B12 and folate levels were determined prior to injection. Serum clearance and urinary and stool excretion of the tracer were measured. Images were routinely obtained at 0.5, 3 to 5, and 20 to 24 hours after injection. Biodistribution of In 111 DAC was determined by computer analysis of regions of interest.

RESULTS

Serum T1/2 clearance was 7 minutes. Average urinary and stool excretion of the injected dose over 24 hours was 26.1% and 0.4%, respectively. The greatest focal uptake of In 111 DAC occurred in the liver and spleen, followed by the nasal cavity and salivary and lacrimal glands. The average tumor uptake of the injected dose was 2% at 30 minutes and 1.5% at 24 hours. High-grade primary and metastatic breast, lung, colon, thyroid, and sarcomatous malignancies were all imaged at 3 to 5 hours after injection. Central nervous system tumors and advanced metastatic prostate cancer were best identified at 24 hours. Mammographically occult, palpable, and nonpalpable breast cancers were delineated by In 111 DAC. Low-grade malignancies as well as early skeletal metastatic disease were not effectively imaged by the vitamin B12 tracer. Patients with elevated baseline vitamin B12 or those concurrently taking corticosteroids appeared to have optimal visualization of their malignancies.

CONCLUSION

Vitamin B12 may be a useful vehicle for delivering diagnostic and therapeutic agents to various malignancies. Further evaluation of cobalamin analogs and their interaction with transport proteins and cellular receptors within malignant tissue and infection is warranted.

Anti-proliferative effect of radiolabelled octreotide in a metastases model in rat liver

Most neuroendocrine tumours and several other tumours, such as breast carcinoma and malignant lymphoma, express somatostatin receptors (SS-Rs). Lesions expressing these receptors can be visualised by receptor scintigraphy using a low radioactive dose of the radiolabelled SS analogue [111In-DTPA0]octreotide. This radioligand is internalised and transported to the lysosomes with a long residence time of 111In. The aim of this experimental study in rats was to investigate whether the same agent, given in a high radioactive dose, can be used for therapy of hepatic metastases of different tumour cell lines. The development of hepatic metastases was determined 21 days after direct injection of SS-R-positive or -negative tumour cells into the vena porta in rats. On day 1 and/or 8, animals were treated with 370 MBq (0.5 microg) [111In-DTPA0]octreotide. In one experiment, using SS-R-positive tumour cells, animals were pre-treated with a high dose of cold octreotide to block the SS-R by saturation. The number of SS-R-positive liver metastases was significantly decreased after treatment with [111In-DTPA0]octreotide. Blocking the SS-R by octreotide substantially decreased the efficacy of treatment with [111In-DTPA0]octreotide, suggesting that the presence of SS-R is mandatory. This was confirmed by the finding that the number of SS-R-negative liver metastases was not affected by treatment with [111In-DTPA0]octreotide. Therefore, we conclude that (i) high radioactive doses of [111In-DTPA0]octreotide for PRRT (peptide receptor radionuclide therapy) can inhibit the growth of SS-R-positive liver metastases in an animal model, (ii) PRRT is effective only if SS-Rs are present on the tumours, (iii) the effect of PRRT with [111In-DTPA0]octreotide can be reduced by pre-treatment with cold octreotide, which indicates that receptor binding is essential for PRRT. Our data suggest that PRRT with radiolabelled octreotide might be a new promising treatment modality for SS-R-positive tumours.

Scintigraphic measurement of regional gastrointestinal transit in the dog

Scintigraphic techniques can measure sequentially gastric emptying, small bowel transit, and colonic transit in humans, and comparable methods for experimental studies in animals would be useful. We developed such a method in dogs and examined the effects of prokinetic drugs on regional transit. Two isotopes were given to fasting dogs. Polystyrene pellets labeled with 99mTc were mixed in a can of dog food and 111In- labeled pellets were given in a gelatin capsule coated with a pH-sensitive polymer, designed to dissolve in the distal bowel. Gamma camera images were obtained for up to 24 h. Prokinetic drugs were given by intravenous injection. Duplicate baseline studies showed good agreement in seven dogs. In a second group (n = 4), intra- and interanimal variabilities were established. Two novel prokinetic drugs (AU-116 and AU-130) accelerated small bowel and colonic transit. A simple noninvasive method for measuring whole gut transit in dogs was developed and validated. Two new prokinetics accelerated small bowel and colonic transit.