Construction and Evaluation of the Tumor Imaging Properties of 123I-Labeled Recombinant and Enzymatically Generated Fab Fragments of the TAG-72 Monoclonal Antibody CC49

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• 作者：Ying Tang ; Shaoxian Yang ; Jean Garié ; py ; Deborah A. Scollard ; Raymond M. Reilly
• 刊名：Bioconjugate Chemistry
• 出版年：2007
• 出版时间：May 2007
• 年：2007
• 卷：18
• 期：3
• 页码：677 - 684
• 全文大小：448K
• 年卷期：v.18,no.3(May 2007)
• ISSN：1520-4812

文摘

Tumor-associated glycoprotein-72 (TAG-72) is overexpressed in a high percentage of epithelial cancers and hasproven useful as a target for imaging and targeted radiotherapy. Our goal was to express a recombinant Fab(rFab) of the TAG-72 monoclonal antibody CC49 in Pichia pastoris and directly compare its tumor and normaltissue uptake and imaging properties with enzymatically generated Fab (eFab). In this study, the genes coding forCC49 Fab were cloned from hybridoma cells and expressed in P. pastoris. Fab was purified to homogeneity andits immunoreactivity toward bovine submaxillary mucin (TAG-72) confirmed by ELISA. The tumor and normaltissue localization of ¹²³I-CC49 rFab and eFab were compared in athymic mice bearing s.c. LS174T colon canceror TAG-72-negative A375 melanoma xenografts. Results showed that pure and immunoreactive rFab of CC49was produced and labeled with ¹²³I. At 24 h post i.v. injection (p.i.), tumor uptake for ¹²³I-rFab in LS174T xenograftswas 6.0% ID/g which was 18-fold higher than in A375 tumors. Tumor-to-normal tissue ratios increased between2 and 24 h and exceeded 5:1 at 24 h p.i. of ¹²³I-rFab. ¹²³I-rFab exhibited significantly lower liver uptake at 12 hp.i. and lower kidney uptake at 2 h p.i. than ¹²³I-eFab. LS174T tumors were imaged as early as 2 h afteradministration of ¹²³I-rFab. We conclude that CC49 rFab can be produced in a P. pastoris host system andaccumulated at comparable levels as eFab in LS174T colon cancer xenografts in mice. The lower liver uptake of¹²³I-rFab as compared with eFab suggests that it may be more useful for imaging liver lesions. No major effect,except for kidneys and liver, was observed on tumor and normal tissue uptake due to introduction of hexahistidineand FLAG affinity tags or peptide linkers in the scaffold of rFab.