[show abstract][hide abstract] ABSTRACT: The αvβ6 integrin is up-regulated in cancer and wound healing but it is not generally expressed in healthy adult tissue. There is increasing evidence that it has a role in cancer progression and will be a useful target for antibody-directed cancer therapies. We report a novel recombinant diabody antibody fragment that targets specifically αvβ6 and blocks its function. The diabody was engineered with a C-terminal hexahistidine tag (His tag), expressed in Pichia pastoris and purified by IMAC. Surface plasmon resonance (SPR) analysis of the purified diabody showed affinity in the nanomolar range. Pre-treatment of αvβ6-expressing cells with the diabody resulted in a reduction of cell migration and adhesion to LAP, demonstrating biological function-blocking activity. After radio-labeling, using the His-tag for site-specific attachment of (99m)Tc, the diabody retained affinity and targeted specifically to αvβ6-expressing tumors in mice bearing isogenic αvβ6 +/- xenografts. Furthermore, the diabody was specifically internalized into αvβ6-expressing cells, indicating warhead targeting potential. Our results indicate that the new αvβ6 diabody has a range of potential applications in imaging, function blocking or targeted delivery/internalization of therapeutic agents.
PLoS ONE 01/2013; 8(9):e73260. · 3.73 Impact Factor
[show abstract][hide abstract] ABSTRACT: Adoptive immunotherapy using chimeric antigen receptor-engrafted T cells is a promising emerging therapy for cancer. Prior to clinical testing, it is mandatory to evaluate human therapeutic cell products in meaningful in vivo pre-clinical models. Here, we describe the use of fused single-photon emission CT-CT imaging to monitor real-time migration of chimeric antigen receptor-engineered T cells in immune compromised (SCID Beige) mice. Following intravenous administration, human T cells migrate in a highly similar manner to that reported in man, but penetrate poorly into established tumors. By contrast, when delivered via intraperitoneal or subcutaneous routes, T cells remain at the site of inoculation with minimal systemic absorption-irrespective of the presence or absence of tumor. Together, these data support the validity of pre-clinical testing of human T-cell immunotherapy in SCID Beige mice. In light of their established efficacy, regional administration of engineered human T cells represents an attractive therapeutic option to minimize toxicity in the treatment of selected malignancies.
Journal of Clinical Immunology 04/2011; 31(4):710-8. · 3.38 Impact Factor
[show abstract][hide abstract] ABSTRACT: The integrin alphavbeta6 is expressed only on epithelia and then usually only during processes of tissue remodelling including cancer, where its high expression correlates with reduced survival. Thus, alphavbeta6 represents an important target for imaging and therapy of cancer and new molecular-specific targeting agents are required. We have developed A20FMDV2, a peptide derived from the VP1 coat protein of foot-and-mouth-disease virus that binds specifically and stably to alphavbeta6. Using a newly generated pair of isogenic human cell lines that differ only in alphavbeta6 expression, it was shown, using biodistribution and SPECT imaging, that indium-111-labelled A20FMDV2 locates specifically to alphavbeta6-expressing tissues in vivo, achieving at least seven-times higher retention in alphavbeta6-positive than in alphavbeta6-negative tumours. In further studies with MCF10.DCIS.COM and MCF10A.CA1a breast carcinoma cell lines, which express alphavbeta6 endogenously, the radiopeptide achieved similar levels of tumour retention and permitted excellent discriminatory imaging of tumours. Thus, A20FMDV2 can be used for molecular-specific targeting of alphavbeta6 for imaging in vivo the often more aggressive, alphavbeta6-positive cancers. In the future, A20FMDV2 could serve also to deliver therapy to these same cancers.
The Journal of Pathology 09/2010; 222(1):52-63. · 7.59 Impact Factor
[show abstract][hide abstract] ABSTRACT: Gastrin/cholecystokinin subtype 2 receptors (CCK-2Rs) are overexpressed in several tumor types and are, thus, a potential target for peptide receptor radionuclide therapy (PRRT) of cancer. To improve the in vivo performance of CCK-2R binding peptides, we have previously synthesized and screened a series of divalent gastrin peptides for improved biochemical and biologic characteristics. In this study, we explore in more detail the most promising of these compounds and compare its performance with a previously described monomeric peptide.
From six (111)In-labeled 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid (DOTA)-conjugated divalent gastrin peptides based on the C-terminal sequence of minigastrin, the maleimide-linked compound DOTA-GSC(succinimidopropionyl-EAYGWNleDF-NH(2))-EAYGWNleDF-NH(2) (MGD5) was selected. The in vitro stability, receptor binding, and internalization of (111)In-MGD5 were studied and compared with those of monomer compound (111)In-APH070. In vivo biodistribution and imaging using a SPECT/CT camera were also performed.
More than 90% of the labeled divalent peptide remained intact after 20 h of incubation in plasma. The inhibitory concentration of 50% of the divalent peptide was 1.0 versus 5.6 nM for the monomer, and the dissociation constant was 0.7 versus 2.9 nM. The rate of internalization of the divalent peptide was twice that of the monomer. Tumor uptake of the divalent peptide in vivo was about 6 times that of the monomer. The rate of washout of the divalent peptide from the tumor was lower than that of the monomer.
Dimerization of the CCK-2R binding site results in an increase in binding affinity and an increase in tumor uptake both in vitro and in vivo. It is likely that these increases would result in improved tumor-targeting efficiency in patients with CCK-2R-positive tumors.
Journal of Nuclear Medicine 11/2009; 50(12):2082-9. · 5.77 Impact Factor
[show abstract][hide abstract] ABSTRACT: Automation of radiopharmaceutical preparation represents a way of reducing radiation doses to operators and providing good manufacturing practice-compliant manufacture of radiopharmaceuticals. Although widely adopted for PET radiochemical synthesis, such methods have not widely been used for the preparation of therapeutic radiopharmaceuticals. Here we describe an evaluation of an automated system for the preparation of radiolabelled antibodies. A labelling method based on the Modular Lab system was developed and applied to the radiolabelling of the monoclonal antibody conjugate, YAML568-CHX'A-DTPA, with indium-111. Antibodies were labelled using both manual and automated means and analysed by high-performance liquid chromatography and thin-layer chromatography methods. Radiochemical purities achieved using automation (mean 98%) were slightly lower than those achieved manually (mean 99%); however, the radiochemical purity obtained was reproducible and well within the set specification of greater than 95%. The Modular Lab system can be used to automate the radiolabelling of monoclonal antibody-chelate conjugates with metallic isotopes such as indium for the potential application for therapeutic radionuclide therapy.
Nuclear Medicine Communications 11/2009; 31(2):173-7. · 1.38 Impact Factor
[show abstract][hide abstract] ABSTRACT: Tumour growth is dependent on angiogenesis, the key mediator of which is vascular endothelial growth factor-A (VEGF-A). VEGF-A exists as two families of alternatively spliced isoforms - pro-angiogenic VEGF(xxx) generated by proximal, and anti-angiogenic VEGF(xxx)b by distal splicing of exon 8. VEGF(165)b inhibits angiogenesis and is downregulated in tumours. Here, we show for the first time that administration of recombinant human VEGF(165)b inhibits colon carcinoma tumour growth and tumour vessel density in nude mice, with a terminal plasma half-life of 6.2h and directly inhibited angiogenic parameters (endothelial sprouting, orientation and structure formation) in vitro. Intravenous injection of (125)I-VEGF(165)b demonstrated significant tumour uptake lasting at least 24h. No adverse effects on liver function or haemodynamics were observed. These results indicate that injected VEGF(165)b was taken up into the tumour as an effective anti-angiogenic cancer therapy, and provide proof of principle for the development of this anti-angiogenic growth factor splice isoform as a novel cancer therapy.
European journal of cancer (Oxford, England: 1990) 09/2008; 44(13):1883-94. · 4.12 Impact Factor
[show abstract][hide abstract] ABSTRACT: Pancreatic cancer has a very poor prognosis with a less than 5% survival rate at 5 years. Neither external beam radiation nor chemotherapy, alone or in combination, have given encouraging results so far. A possible solution might come from the use of targeted therapy such as radioimmunotherapy. We present here the results obtained from the preclinical development of a new monoclonal antiferritin antibody (Ab), AMB8LK. Ferritin is overexpressed in pancreatic cancer and could thus be used as a target for the delivery of radioactivity at the tumour sites. The AMB8LK Ab was conjugated to three chelating agents: the 2-(4-isothiocyanatobenzyl)-diethylenetriamine pentaacetic acid (PSCN-Bz-DTPA), the (R)-2-amino-3-(4-isothiocyanatophenyl)propyl]-trans-(S,S)-cyclohexane-1,2-diamine-pentaacetic acid (p5CN-Bz-CHX-A"-DTPA) and the 2-(4-isothiocyanatobenzyl)-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (pSCN-Bz-DOTA). Radiolabelling of the three immunoconjugates with indium 111 and yttrium 90 as well as in vitro stability and immunoreactivity against pure ferritin and cells expressing ferritin were analysed. In vivo biodistribution studies were conducted on normal and on human pancreatic adenocarcinoma CAPAN-1 tumour bearing mice. These experiments demonstrated good radiolabelling (>95%), stability and immunoreactivity of the three compounds. In the biodistribution studies, differences between the three immunoconjugates were apparent in the rate of blood clearance and in tumour, liver and bone uptake. A very good pancreatic adenocarcinoma tumour targeting was observed especially with the Bz-DTPA-AMB8LK: 20% of the injected dose of the indium-labelled compound 3 days after injection; 15% of the injected dose 5 days after that of the yttrium-labelled Ab. Altogether, these results in animal models suggest that (90)Y-Bz-DTPA-AMB8LK is a good candidate for further therapeutic efficacy studies.
Nuclear Medicine and Biology 05/2007; 34(3):293-304. · 2.52 Impact Factor
[show abstract][hide abstract] ABSTRACT: The gastrin/cholecystokinin-2 (CCK-2) receptor has been identified as a possible target for peptide receptor radionuclide imaging and therapy. Several radiolabeled peptides binding to this receptor have been explored in animal models and clinical trials but either low tumor uptake or high renal retention has been found. The aim of this study was to identify a peptide with improved tumor-to-kidney pharmacodynamics when compared with current candidates.
A small peptide-chelator library of 34 compounds based on the C-terminal sequences of CCK-8 or minigastrin was constructed. The peptides were radiolabeled with (111)In with high labeling efficiency (>90%), as determined by high-performance liquid chromatographic analysis. The labeled peptides were screened by assessing tumor and kidney uptake in pancreatic xenograft nude mouse models, including AR42J. An extensive biodistribution analysis was performed on the lead candidate from the library.
Minigastrin analogs containing a pentaglutamate sequence showed the highest tumor uptake but very high renal retention. CCK analogs showed the lowest tumor and renal uptake. Deletion of the pentaglutamate sequence in the gastrin analogs lowered the tumor uptake by a factor of 3 but decreased the kidney uptake by a factor of 20. Insertion of histidine residues in the sequence reduced kidney uptake by a further factor of almost 2-fold. In AR42J tumor-bearing mice, the peptide with the sequence DOTA-HHEAYGWMDF-NH(2) (DOTA is tetraazacyclododecane tetraacetic acid) showed the highest tumor-to-kidney ratio of all peptides studied, with saturable uptake in target organs and low uptake by nontarget tissues other than the kidney.
This peptide is a worthwhile candidate for clinical studies to determine whether it is suitable for use in peptide receptor-targeted radionuclide therapy.
Journal of Nuclear Medicine 04/2007; 48(4):615-22. · 5.77 Impact Factor
[show abstract][hide abstract] ABSTRACT: In this study, a human carcinoembryonic antigen (CEA) transgenic (CEA.Tg) mouse model was evaluated for the preclinical assessment of agents directed against CEA.
Cell-type and organ-specific expression of CEA was studied in CEA.Tg mice derived from a colony that carries the complete human CEA gene together with flanking regulatory sequences and also in wild-type controls. Biodistribution studies were performed on wild-type and CEA.Tg mice by intravenous injection of 125I-labeled anti-CEA (PR1A3) or isotype control (IC) murine monoclonal antibodies (mAbs). Studies were also performed on tumor-bearing CEA.Tg and nude mice.
As with humans, the CEA.Tg mice had low serum levels of CEA (mean, 8.8 +/- 5.52 ng/mL), and cell-surface CEA expression was primarily localized in the gastrointestinal tract. Both mAbs showed similar biodistribution patterns in the wild-type mice, whereas in the CEA.Tg mice, PR1A3 specifically localized to the CEA-expressing tissues. In the gastrointestinal tract, the percentage injected dose for PR1A3 was significantly higher than that for IC mAb at all the time points sampled. In CEA.Tg mice bearing a murine tumor transfected with human CEA, PR1A3 targeted tissues with constitutive CEA expression and was retained at the tumor site at high levels, whereas in nude mice, PR1A3 localized only to the site of the transplanted tumor.
These results demonstrate the targeting potential of the anti-CEA antibody, PR1A3, and emphasize the value of using a transgenic model in preclinical studies.
Journal of Nuclear Medicine 11/2002; 43(10):1368-76. · 5.77 Impact Factor
[show abstract][hide abstract] ABSTRACT: Tumour growth is dependent on angiogenesis, the key mediator of which is vascular endothelial growth factor (VEGF-A). VEGF-A exists as two families of alternatively spliced isoforms – pro-angiogenic VEGFxxx generated by proximal, and anti-angiogenic VEGFxxxb by distal splicing of exon 8. VEGF165b inhibits angiogenesis and is downregulated in tumours. Here, we show for the first time that daily administration of 5μg recombinant human VEGF165b inhibits colon carcinoma tumour growth and tumour vessel density in nude mice with a terminal plasma half-life of 6.2h. No adverse effects on liver functions were observed. Intravenous (i.v.) injection of 125I-VEGF165b demonstrated a significant tumour uptake after 4h. VEGF165b directly inhibited endothelial cell orientation and structure formation on extracellular matrix. These results indicate that VEGF165b injection was taken up into the tumour as an effective anti-angiogenic cancer therapy and provide proof of principle for the development of anti-angiogenic growth factor splice isoforms as novel cancer therapies.