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.