Selective localisation of two radiolabelled anti-sarcoma monoclonal antibodies in human osteosarcoma xenografts

Abstract

Two mouse monoclonal antibodies (MoAbs), TP-1 and TP-3, previously shown in immunohistochemical studies to react with osteosarcomas, were labelled with 125I or 131I and evaluated for their ability to localise to human osteogenic sarcoma xenografts after intravenous injection. The radiolabelled TP-1 and TP-3 MoAbs had immunoreactive fractions of 70% and 67%, respectively, and bound to target cells with binding constants of 8.5 X 10(8) M-1 and 4.0 X 10(9) M-1, respectively. After injection of labelled TP-3 IgG, approximately 16% of the dose X g-1 tissue was found in the tumour after 24 hours. Maximum tumour/blood radioactivity ratios of 6-7 were achieved 3-4 days after antibody injection, while the ratios for the normal tissues were less than 1. The tumours could be clearly visualised by whole-body gamma scintigraphy without the need for subtraction techniques. The TP-1 IgG accumulated to a large extent also in the spleen. Hence, with this antibody the tumour was less well delineated from the adjacent normal tissues. However, the F(ab')2 fragments, derived from the TP-1 IgG, gave tumour/blood ratios up to approximately 40 after 3-4 days and yielded sharp gamma scintigrams of the tumour. Specificity of the antibody localisation was indicated by the lack of accumulation in a contralateral melanoma xenograft and the failure of 2 isotype-matched irrelevant MoAbs to localise to the sarcomas. With the F(ab')2 fragments satisfactory images could be obtained already after 16 hours. The results suggest that this preparation may be useful in clinical radioimmunodetection of osteogenic sarcomas.

Evaluation of CD146 as Target for Radioimmunotherapy against Osteosarcoma

“…The presented biodistribution data indicate that favorable tumor to tissue ratios can be achieved with radiolabeled versions of the OI-3 mAbs, indicative of CD146 being a suitable target for radioimmunotherapy. In the OHS xenograft model, 24 hours after intravenous administration of 125 I-labeled mAbs TP-1 and TP-3 [ 34 , 50 ], tumor to normal tissue ratios were comparable to the ratios found for the OI-3 mAbs labeled with 125 I in this study. The results obtained when the OI-3 mAbs were labeled with the more therapeutically relevant radionuclide 177 Lu, further demonstrated a promising biodistribution profile.…”

“…The use of antibody-toxin conjugates has previously been suggested as a modality in OS [ 33 ]. In vitro and in vivo targeting with radiolabeled antibodies have also been evaluated with the OS specific mAbs TP-1 and TP-3 [ 34 ]. TP-1 and TP-3 were found to bind to an alkaline phosphatase isoform with no or very limited expression on normal cells and other cancer forms [ 35 ].…”

Radioimmunotargeting of human tumour cells in immunocompetent animals

“…The monoclonal antibody TP-1 (IgG2a) ) is specific for an epitope on a sarcoma associated antigen (Bruland et al, 1988). The immunoglobulin fractions were separated from ascites with affinity chromatography on protein-A Sepharose columns (Pharmacia, Sweden), and purity was controlled with Fast Protein Liquid Chromatography (FPLC, Pharmacia, Sweden), or polyacrylamide gel electrophoresis, as earlier described for both H7 (Fjeld et al, 1988), and TP-1 (Bruland et al, 1987).…”

“…H7 was enzymatically fragmented to Fab with papain (Goding, 1983;Fjeld et al, 1988), and TP-1 to F(ab')2 with pepsin (Parham, 1983;Bruland et al, 1987).…”

Abundant Tyrosine Residues in the Antigen Binding Site in Anti-Osteosarcoma Monoclonal Antibodies Tp-1 and Tp-3: Application to radiolabeling

“…The murine MAbs TP-1 (y2a) and TP-3 (y2b) (4) recognize two different epitopes on a tumor-associated antigen expressed on both canine and human 0s cells (5,6). The tumor targeting of radiolabeled TP antibodies has been examined in vivo in various animal models (7)(8)(9)(10) and in patients suffering from 0s (1 1). Specific tumor uptake was observed in both primary and metastatic 0s.…”