Targeted delivery of chemotherapeutic agents is a new approach for the treatment of
cancer, which provides increased selectivity and decreased systemic toxicity. We have recently developed a promising drug delivery system, in which the anticancer drug
daunorubicin (Dau) was attached via
oxime bond to a
gonadotropin-releasing hormone-III (
GnRH-III) derivative used as a targeting moiety (Glp-His-Trp-Lys(Ac)-His-Asp-Trp-Lys(Da = Aoa)-
Pro-Gly-NH2; Glp =
pyroglutamic acid, Ac = acetyl; Aoa = aminooxyacetyl). This bioconjugate exerted in vitro
cytostatic/cytotoxic effect on human breast, prostate and
colon cancer cells, as well as significant in vivo
tumor growth inhibitory effect on colon
carcinoma bearing mice. In our previous studies, H-Lys(Dau = Aoa)-
OH was identified as the smallest metabolite produced in the presence of rat liver lysosomal homogenate, which was able to bind to
DNA in vitro. To get a deeper insight into the mechanism of action of the bioconjugate, changes in the
protein expression profile of HT-29 human
colon cancer cells
after treatment with the bioconjugate or free
daunorubicin were investigated by mass spectrometry-based proteomics. Our results indicate that several metabolism-related
proteins, molecular chaperons and
proteins involved in signaling are differently expressed after targeted chemotherapeutic treatment, leading to the conclusion that the bioconjugate exerts its cytotoxic action by interfering with multiple intracellular processes.