Postchemotherapy and Tumor-Selective Targeting with the La-Specific DAB4 Monoclonal Antibody Relates to Apoptotic Cell Clearance

Abstract

Early identification of tumor responses to treatment is crucial for devising more effective and safer cancer treatments. No widely applicable, noninvasive method currently exists for specifically detecting tumor cell death after cytotoxic treatment and thus for predicting treatment outcomes. Methods: We have further characterized the targeting of the murine monoclonal antibody DAB4 specifically to dead tumor cells in vitro, in vivo, and in clinical samples. We found that sustained DAB4 binding to treated cells was closely associated with markers of intrinsic apoptosis and DNA double-strand break formation. In a competition binding assay, DAB4 bound EL4 murine thymic lymphoma cells in preference to the normal counterpart of murine thymocytes. Defective in vivo clearance of apoptotic cells augmented in vivo accumulation of DAB4 in tumors particularly after chemotherapy but was unchanged in normal tissues. Tumor targeting of DAB4 was selective for syngeneic murine tumors and for human tumor xenografts of prostate cancer (PC-3) and pancreatic cancer (Panc-1) before and more so after chemotherapy. Furthermore, DAB4 was shown to bind to dead primary acute lymphoblastic leukemic blasts cultured with cytotoxic drugs and dead epithelial cancer cells isolated from peripheral blood of small cell lung carcinoma patients given chemotherapy. Conclusion: Collectively, these results further demonstrate the selectivity of DAB4 for chemotherapy-induced dead tumor cells. This postchemotherapy selectivity is related to a relative increase in the availability of DAB4-binding targets in tumor tissue rather than in normal tissues. The in vitro findings were translated in vivo to human xenograft models and to ex vivo analyses of clinical samples, providing further evidence of the potential of DAB4 as a marker of tumor cell death after DNA-damaging cytotoxic treatment that could be harnessed as a predictive marker of treatment responses.

Long Noncoding RNAs CUPID1 and CUPID2 Mediate Breast Cancer Risk at 11q13 by Modulating the Response to DNA Damage

“…Flow-cytometric assays using biotinylated anti-gH2AX (JBW301, Millipore) and DNA content staining with 7AAD (Invitrogen) were carried out as described previously, 23 and samples were acquired and analyzed with FACSCanto II (Becton Dickinson).…”

WITHDRAWN: Positron Emission Tomographic imaging of tumor cell death using Zirconium-89-labeled APOMAB® following cisplatin chemotherapy in lung and ovarian cancer xenograft models

“…As well as in vitro studies, we have shown that DAB4 binds with high speci city to dead tumor cells in vivo. We drew on this tumor-targeting property to radiolabel DAB4 with 111 Indium for tumor imaging [18,19] and with 90 Yttrium [17], 177 Lutetium [20] and 227 Thorium [21] for antitumor therapy by exploiting the phenomenon of β-and α-radiation cross re [22].…”

APOMAB Antibody–Drug Conjugates Targeting Dead Tumor Cells are Effective In Vivo

“…APOMAB Ò (DAB4) is a mouse mAb, which targets the Lupusassociated (La)/Sj€ ogren Syndrome-B (SSB) antigen, which is overexpressed in a variety of different cancers (7)(8)(9)(10)(11). La/SSB only becomes available for antibody binding in cells that have lost membrane integrity, particularly in apoptotic and necrotic cancer cells, making DAB4 a dead tumor cell-targeting mAb (7,(12)(13)(14)(15)(16)(17). As La/SSB is highly conserved between mice and humans, DAB4 binds both mouse and human forms of La/SSB.…”

“…Nevertheless, characteristics of the in vitro binding of the DAB4 mAb to dead tumor cells compared with a TNT mAb help to explain tumor accumulation of DAB4. In vitro, DAB4 preferentially binds to dead tumor cells, which die because of DNA-damaging antitumor treatment; this binding is saturable, rapid, high-avidity, irreversible, and involves protein-protein crosslinking of DAB4 with its target antigen, La/SSB, during tumor cell death (7,(12)(13)(14)(15)(16). TNT3 has been used preclinically as an effective vehicle for the delivery of immunostimulatory CpG to the tumor site in mouse xenograft tumor models (21) and as a fusion protein for tumor delivery of IFNg (22).…”