This Article Full Text Full Text (PDF) Correction (v13,p6245) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Al-Ejeh, F. Articles by Brown, M. P. Search for Related Content PubMed PubMed Citation Articles by Al-Ejeh, F. Articles by Brown, M. P.

In vivo Targeting of Dead Tumor Cells in a Murine Tumor Model Using a Monoclonal Antibody Specific for the La Autoantigen

Authors' Affiliations: ¹ Experimental Therapeutics Laboratory, Hanson Institute; ² School of Pharmacy and Medical Sciences, University of South Australia; and ³ Department of Medical Oncology, Royal Adelaide Hospital, Adelaide, South Australia, Australia

Requests for reprints: Michael P. Brown, Department of Medical Oncology, Royal Adelaide Hospital, Level 7, East Wing, North Terrace, Adelaide, SA 5000, Australia. E-mail: michael.brown{at}health.sa.gov.au.

Purpose: To investigate the potential of the La-specific monoclonal antibody (mAb) 3B9 as an in vivo tumor-targeting agent.

Experimental Design: The murine EL4 lymphoma cell line was used for in vitro studies and the EL4 model in which apoptosis was induced with cyclophosphamide and etoposide was used for in vivo studies. In vitro studies compared 3B9 binding in the EL4 cell with that in its counterpart primary cell type of the thymocyte. For in vivo studies, 3B9 was intrinsically or extrinsically labeled with carbon-14 or 1,4,7,10-tetra-azacylododecane-N,N',N'',N''''-tetraacetic acid–indium-111, respectively, and biodistribution of the radiotracers was investigated in EL4 tumor-bearing mice, which were treated or not with chemotherapy.

Results: La-specific 3B9 mAb bound EL4 cells rather than thymocytes, and binding was detergent resistant. 3B9 binding to dead EL4 cells in vitro was specific, rapid, and saturable. Significantly, more 3B9 bound dead EL4 tumor explant cells after host mice were treated with chemotherapy, which suggested that DNA damage induced 3B9 binding. Tumor binding of 3B9 in vivo was antigen specific and increased significantly after chemotherapy. Tumor accumulation of 3B9 peaked at 50% of the injected dose per gram of tumor 72 h after chemotherapy and correlated with increased tumor cell death. Tumor/organ ratios of 3B9 biodistribution, which included the tumor/blood ratio, exceeded unity 48 or more hours after chemotherapy.

Conclusions: La-specific mAb selectively targeted dead tumor cells in vivo, and targeting was augmented by cytotoxic chemotherapy. This novel cell death radioligand may be useful both for radioimmunoscintigraphy and radioimmunotherapy.