Production and characterization of monoclonal antibodies specific for canine CD138 (syndecan-1) for nuclear medicine preclinical trials on spontaneous tumours.

We isolated 11 antibodies specific for canine CD138 (cCD138) to validate the interest of CD138 antigen targeting in dogs with spontaneous mammary carcinoma. The affinity of the monoclonal antibodies in the nanomolar range is suitable for immunohistochemistry and nuclear medicine applications. Four distinct epitopes were recognized on cCD138 by this panel of antibodies. CD138 expression in canine healthy tissues is comparable to that reported in humans. CD138 is frequently expressed in canine mammary carcinomas corresponding to the human triple negative breast cancer subtype, with cytoplasmic and membranous expression. In canine diffuse large B-cell lymphoma, CD138 expression is associated with the 'non-germinal center' phenotype corresponding to the most aggressive subtype in humans. This homology of CD138 expression between dogs and humans confirms the relevance of tumour-bearing dogs as spontaneous models for nuclear medicine applications, especially for the evaluation of new tumour targeting strategies for diagnosis by phenotypic imaging and radio-immunotherapy.

Radioimmunotherapy of prostate cancer in human xenografts using monoclonal antibodies specific to prostate specific membrane antigen (PSMA): studies in nude mice.

BACKGROUND: Prostate specific membrane antigen (PSMA), expressed by virtually all prostate cancers is an ideal target for targeted therapy of prostate cancer. Radiolabeled J591 monoclonal antibody (MAb) binds with high affinity to an extracellular epitope of PSMA and localizes specifically in PSMA positive LNCaP tumors in vivo. METHODS: Pre-clinical radioimmunotherapy (RIT) studies using (131)I-huJ591 and (90)Y-1,4,7,10-tetraazacyclododecane-N,N',N",N"'-tetraacetic acid (DOTA)-huJ591 MAbs were studied in nude mice bearing LNCaP xenografts. RESULTS: A 15-90% reduction in mean tumor volume was observed after a single dose of (131)I-huJ591 (3.7-11.1 MBq) or (90)Y-DOTA-huJ591 (3.7-7.4 MBq). The median survival time increased 2-3 times relative to untreated controls. Multiple administrations of fractionated doses of (90)Y-DOTA-huJ591 were even more effective with minimal toxicity. Radiation dose to blood and tumor was higher with (90)Y than with (131)I. The maximum tolerated dose (MTD) is 5.55 MBq for (90)Y-DOTA-huJ591 and more than 11.1 MBq for (131)I-huJ591. For (90)Y-DOTA-huJ591 at MTD, dose to the tumor was 2,753 cGy. CONCLUSIONS: In nude mice bearing PSMA positive tumors, radiation dose to the tumor with (90)Y-DOTA-J591 is greater for large tumors than with (131)I-J591. The theoretical and practical considerations strongly suggest that (90)Y-DOTA-huJ591 may be a suitable radiopharmaceutical for the treatment of prostate cancer.