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1st World Conference on Physico-Chemical Methods in Drug Discovery and Development
Synthesis, structural and biochemical characterization of oxime bond
containing anticancer drug delivery systems
Gábor Mező1, Antal Csámpai2, Bence Kapuvári3, Erika Orbán1, Ildikó Szabó1, László
Radnai4 and Marilena Manea5,6
1
Research Group of Peptide Chemistry, Hungarian Academy of Sciences, Eötvös L.
University, Budapest, Hungary; 2Institute of Chemistry, Eötvös L. University, Budapest,
Hungary; 3National Institute of Oncology, Budapest, Hungary; 4Department of
Biochemistry, Eötvös L. University, Budapest, Hungary; 5Laboratory of Analytical
Chemistry and Biopolymer Structure Analysis, Department of Chemistry and
6
Zukunftskolleg, University of Konstanz, Konstanz, Germany
Chemoselective ligation approaches are widely used in the synthesis of cyclic peptides and
peptide conjugates. Oxime bond formation is one of the most commonly used, due to its
chemical stability and easy synthesis. The oxime linkage is formed between an oxo group
(ketone or aldehyde) and a hydroxylamine derivative such as aminooxyacetic acid.
Chemoselective ligation procedures are also employed in the preparation of drug delivery
systems in which drugs are attached to peptides or to other types of targeting moieties. The
advantages of drug delivery systems is their increased selectivity and lower toxicity
resulting in higher therapeutic efficiency. However, many drugs have no functional groups
that can be used for conjugation or the modification of the functional groups lead to the loss
of the biological activity. Drugs containing oxo groups can be attached via oxime bond to
various carriers. In our study, daunorubicin (anthracycline antibiotic) and exemestane
(steroidal aromatase inhibitor) as antineoplastic agents were modified with aminooxiacetic
acid (Aoa). The isomer composition of the oxime bond of the compounds was determined
by NMR spectroscopy. The drugs were attached to the gonadotropin-releasing hormone
(GnRH) derivatives. These hormone peptides have own antitumor activity and recognize
the GnRH receptors that are overexpressed on tumor cells providing increased selectivity to
the conjugates. Daunorubicin (Dau) was coupled to GnRH-III (Glp-His-Trp-Ser-His-AspTrp-Lys-Pro-Gly-NH2), a weak agonist peptide, while exemestane was incorporated
between two peptide chains of a GnRH antagonist (Ac-D-Trp-D-Cpa-D-Trp-Ser-D-LysAsp(Leu-Gln-Pro-D-Ala-NH2)-DEA) resulting in a dimer. Dau has antitumor activity due
to its ability to intercalate into the DNA chains. Therefore, the interaction with DNA of
Dau, Dau=Aoa-OH and its conjugated form was studied by fluorescence spectroscopy. It
was found that Dau and Dau-GnRH-III conjugate bound to the DNA, while the interaction
of Dau=Aoa-OH with DNA was less pronounced. The cellular uptake studies of Dau and
Dau-GnRH-III conjugate, determined by flow cytometry, showed that Dau was taken up in
a higher amount by MCF-7 human breast and C26 murine colon cancer cells than DauGnRH-III conjugate. However, the in vitro cytostatic effect of Dau was only one order of
magnitude higher than it was obtained in the case of Dau=Aoa-OH and Dau-GnRH-III
conjugate.
Acknowledgement
This work was supported by grants from the Hungarian National Science Fund (OTKA
T049814, NK 77485), the Ministry of Health (ETT 202/2006), GVOP-3.2.1.-2004-040005/3 and Zukunftskolleg and AFF (Project 01/09), University of Konstanz.