Liesbet Vervoort

Monoclonal antibody 14C5 targets integrin αvβ5

This study identifies and characterizes the antigen recognized by monoclonal antibody (mAb) 14C5. We compared the expression of antigen 14C5 with the expression of eight integrin subunits (α1, α2, α3, αv, β1, β2, β3, and β4) and three integrin heterodimers (αvβ3, αvβ5, and α5β1) by flow cytometry. Antigen 14C5 showed a similar expression to αvβ5 in eight different epithelial cancer cell lines (A549, A2058, C32, Capan-2, Colo16, HT-1080, HT-29, and SKBR-3). Specific binding of P1F6, an anti-αvβ5 specific antibody, was blocked by mAb 14C5. After transient expression of αvβ5 in 14C5-negative Colo16 cells, mAb 14C5 was able to bind a subpopulation of αvβ5-positive cells. We evaluated the tissue distribution of the 14C5 antigen in colon (n = 20) and lung (n = 16) cancer tissues. The colon carcinoma cells stained positive for 14C5 in 50% of tumors analyzed, whereas bronchoalveolar lung carcinoma and typical carcinoid were not positive for the antigen. More common types of non–small cell lung cancer, i.e., squamous (n = 5) and adenocarcinoma (n = 3), stained positive in 2 of 5 squamous carcinomas and in 1 of 3 investigated adenocarcinoma. Colon (95%) and lung (50%) carcinoma tissues showed extensive expression of antigen 14C5 in the stroma surrounding the tumor cells and on the membrane of the adjacent fibroblasts. We show for the first time that mAb 14C5 binds the vascular integrin αvβ5, suggesting that mAb 14C5 can be used as a screening agent to select colon and lung cancer patients that are eligible for anti-αvβ5–based therapies. [Mol Cancer Ther 2008;7(12):3771–9]

Preclinical Evaluation of Monoclonal Antibody 14C5 for Targeting Pancreatic Cancer

The use of radiolabeled antibodies that are able to target primary tumors as well as metastatic tumor sites with minimal reactivity to normal tissues is a promising approach for treating pancreatic cancer. In this study, the integrin alpha(v)beta(5) is studied as a target for the diagnosis of and potential therapy for human pancreatic cancer by using the radiolabeled murine monoclonal antibody (mAb) 14C5. Biopsy specimens from human pancreatic tumors were examined for the expression of the integrin alpha(v)beta(5). The pancreatic tumor cell line Capan-1 was used to test the in vitro targeting potency of mAb 14C5 labeled with 125/131-iodine and 111-indium. Internalization, retention, and metabolism were investigated in cellular radioimmunoassays. Biodistribution and tumor-targeting characteristics were studied in Capan-1 xenografts. All tumor sections were positive for the integrin alpha(v)beta(5), with an extensive positive staining of the stroma. Saturation binding experiments showed high affinity with comparable K(d)s. In vitro internalization experiments showed a longer intracellular retention of (111)In-p-benzyl isothiocyanate-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (p-SCN-Bz-DOTA)-14C5 in comparison to (125)I-14C5 and (111)In-p-isothiocyanatobenzyl diethylenetriaminepentaacetic acid (p-SCN-Bz-DTPA)-14C5. In vivo radioisotope tumor uptake was maximum at 48-72 hours, with the uptake of (111)In-p-SCN-Bz-DOTA-14C5 (35.84 +/- 8.64 percentage of injected dose per g [%ID/g]) being 3.9- and 2.2-folds higher than (131)I-14C5 (12.16 +/- 1.03%ID/g) and (111)In-p-SCN-Bz-DTPA-14C5 (14.30 +/- 3.76%ID/g), respectively. Planar gamma imaging with mAb 14C5 indicated clear localization of the pancreatic tumors versus minimal normal tissue uptake. mAb 14C5 is a promising new antibody for targeting the integrin alpha(v)beta(5) for the diagnosis of and potential therapy for pancreatic cancer.

PH1-derived bivalent bibodies and trivalent tribodies bind differentially to shed and tumour cell-associated MUC1.

Most adenocarcinomas express altered MUC1 as a tumour-associated antigen. Due to suboptimal glycosylation in tumour-associated MUC1, the apomucin core is exposed, revealing new epitopes for antibody-directed immunotherapy. The human PH1 Fab binds specifically to this MUC1 apomucin. We describe the engineering and functional characterization of bi- and trivalent recombinant antibody derivatives from the PH1 Fab. Bi- and tribodies were made using the disulfide-stabilized Fab fragment as a heterodimerization scaffold with PH1 single-chain variable fragments fused to either one or both Fab-chain C-termini. Immunoassays revealed 27- and 165-fold improved dissociation constants (K(D) = 30 and 5 nM) of the PH1 bi- and tribodies compared with the parental Fab (K(D) = 820 nM). Unexpectedly, major differences were seen in the ability of the antibody constructs to bind shed and tumour cell-tethered MUC1. While the tribody did not discriminate between both MUC1 forms, the bibody demonstrated preferential interaction with membrane-bound MUC1 compared with shed MUC1. This preferential recognition of membrane-bound MUC1, along with the high serum stability of the bibody, its intermediate size and efficient internalization by MUC1(+) cells, makes the human PH1-derived bibody a valuable candidate as a cancer-targeting therapeutic.

Membrane type 1 matrix metalloproteinase detection in tumors, using the iodinated endogenous [123I]-tissue inhibitor 2 of metalloproteinases as imaging agent.

Matrix metalloproteinases (MMPs) are principal participants in tumor development. In addition to serve as a useful biochemical marker, MMP expression may also provide a target for the diagnostic in vivo imaging of tumors, using a radiolabeled inhibitor. This study investigates the use of membrane type 1 (MT1)-MMP as target for in vivo tumor diagnosis. Specific binding of the endogenous tissue inhibitor of metalloproteinase-2 (TIMP-2) to MT1-MMP has been previously described. In this study, biodistribution and imaging experiments were performed on MT1-MMP-overexpressing (S.1.5) and control (C.IV.3) tumor-inoculated mice using [(123)I]-recombinant human TIMP-2 (rhTIMP-2) as radioligand and [(123)I]-rhTIMP-1 as control. The expression profile was controlled in vitro and on tumor extracts. rhTIMP-2 as well as rhTIMP-1 were labeled using the Iodogen method and characterized. Biodistribution of [(123)I]-rhTIMP-2 showed a tumor uptake of 2.87% ± 1.58% ID/g at 3 hours postinjection in S.1.5. Tumor values of [(123)I]-rhTIMP-1 and [(123)I]-rhTIMP-2 evaluated in S.1.5 and C.IV.3, respectively, were significantly lower. Planar imaging revealed significant uptake of [(123)I]-rhTIMP-2 in S.1.5 compared with contralateral background areas. This could not be observed in C.IV.3 and with [(123)I]-rhTIMP-1 in S.1.5. All tumors were well established (200-800  mg). These results suggest that rhTIMP-2 holds potential for development of radiotracers for in vivo imaging in overexpressing MT1-MMP but not in similar tumors that do not express this protease.