Premium
Release of Toxic Gd 3+ Ions to Tumour Cells by Vitamin B 12 Bioconjugates
Author(s) -
Siega Patrizia,
Wuerges Jochen,
Arena Francesca,
Gianolio Eliana,
Fedosov Sergey N.,
Dreos Renata,
Geremia Silvano,
Aime Silvio,
Randaccio Lucio
Publication year - 2009
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200802680
Subject(s) - moiety , chemistry , hydrolysis , carboxylate , viability assay , chelation , trypan blue , nuclear chemistry , stereochemistry , crystallography , medicinal chemistry , in vitro , inorganic chemistry , biochemistry
Two probes consisting of vitamin B 12 (CNCbl) conjugated to Gd chelates by esterification of the ribose 5′‐OH moiety, Gd–DTPA–CNCbl ( 1 ; DTPA = diethylenetriamine‐ N , N , N′ , N′′ , N′′ ‐pentaacetic acid) and Gd–TTHA–CNCbl ( 2 ; TTHA = triethylenetetramine‐ N , N , N′ , N′′ , N′′′ , N′′′ ‐hexaacetic acid), have been synthesised and characterised. The crystal structure of a dimeric form of 1 , obtained by crystallisation with an excess of GdCl 3 , has been determined. The kinetics of binding to and dissociation from transcobalamin II show that 1 and 2 maintain high‐affinity binding to the vitamin B 12 transport protein. Complex 2 is very stable with respect to Gd 3+ release owing to the saturated co‐ordination of the Gd 3+ ion by four amino and five carboxylate groups. Hydrolysis of the ester functionality occurs on the time scale of several hours. The lack of saturation and the possible involvement of the ester functionality in co‐ordination result in lower stability of 1 towards hydrolysis and in a considerable release of Gd 3+ in vitro. Gd 3+ ions released from 1 are avidly taken up by the K562 tumour cells to an extent corresponding to approximately 10 10 Gd 3+ per cell. The internalisation of toxic Gd 3+ ions causes a marked decrease in cell viability as assessed by Trypan blue and WST‐1 tests. On the contrary, the experiments with the more stable 2 did not show any significant cell internalisation of Gd 3+ ions and any influence on cell viability. The results point to new avenues of in situ generation of cytotoxic pathways based on the release of toxic Gd 3+ ions by vitamin B 12 bioconjugates.