Comparison of blocked and non-blocked ricin-antibody immunotoxins against human gastric carcinoma and colorectal adenocarcinoma cell lines
✍ Scribed by Luigi Cattel; Laura Delprino; Paola Brusa; Franco Dosio; Paolo M. Comoglio; Maria Prat
- Book ID
- 104663496
- Publisher
- Springer-Verlag
- Year
- 1988
- Tongue
- English
- Weight
- 749 KB
- Volume
- 27
- Category
- Article
- ISSN
- 0340-7004
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✦ Synopsis
To avoid non-specific binding of intact ricin-antibody conjugates, we prepared a new blocked thioether-linked ricin-antibody IT, in which the galactose binding site of ricin had lost the ability to bind to galactosidic residues of Sepharose 6B gel. As carrier agent, the monoclonal antibody AR-3, which defines the CAR-3 tumour-associated antigenic determinant expressed selectively on different human carcinoma cell lines, was used. Purification of the new conjugate was performed in three sequential steps: (1) by HPLC gel filtration on TSK G3000SW to remove the unconjugated ricin: (2) by affinity chromatography on Affi-Gel Blue to separate the free antibody from the conjugate and (3) by affinity chromatography on Sepharose 6B to separate the galactose-binding IT from the non-binding moiety. The cytotoxicity of the blocked and non-blocked thioether-linked IT was compared with that of classical ricin-antibody IT conjugated via SPDP and that of ricin A chain IT. The comparison was made on two different target cell lines (KATO III human gastric carcinoma and HT-29 human colorectal carcinoma) versus two control cell lines (HL-60 promyelocytic pre-leukaemic and COLO38 melanoma). The results showed that the blocked thioether IT displayed a more selective toxicity to target cells than the non-blocked IT and was much more potent than the ricin A chain conjugate.