Bence Kapuvári

Development of an Oxime Bond Containing Daunorubicin-Gonadotropin-Releasing Hormone-III Conjugate as a Potential Anticancer Drug

Here, we report on the synthesis and biological properties of a conjugate in which daunorubicin (Dau) as chemotherapeutic agent was attached through an oxime bond to gonadotropin-releasing hormone-III (GnRH-III) as targeting moiety. In vitro toxicity and the cytostatic effect of the conjugate on MCF-7 human breast and C26 murine colon cancer cell lines were determined, and the results were compared with those obtained for the free daunorubicin, as well as with the doxorubicin containing derivative. In vivo antitumor effect of daunorubicin-GnRH-III was studied on Balb/c female mice transplanted with C26 tumor. Our data indicate that the daunorubicin-GnRH-III conjugate had a lower toxic effect than the free daunorubicin and it was essentially nontoxic up to 15 mg (Dau content)/kg body weight. The treatment of the C26 tumor bearing mice with the conjugate led to tumor growth inhibition and longer survival time in comparison with the controls and with the administration of the free drug. When mice were treated twice with the conjugate (on days 4 and 7 after tumor transplantation), 46% tumor growth inhibition was obtained. In this case, the increase of the median survival time was 38% compared to the controls.

Enhanced enzymatic stability and antitumor activity of daunorubicin-GnRH-III bioconjugates modified in position 4.

Here, we report on the synthesis, enzymatic stability, and antitumor activity of novel bioconjugates containing the chemotherapeutic agent daunorubicin attached through an oxime bond to various gonadotropin-releasing hormone-III (GnRH-III) derivatives. In order to increase the enzymatic stability of the bioconjugates (in particular against chymotrypsin), (4)Ser was replaced by N-Me-Ser or Lys(Ac). A compound in which (4)Lys was not acetylated was also prepared, with the aim of investigating the influence of the free ε-amino group on the biochemical properties. The in vitro cytostatic effect of the bioconjugates was determined on MCF-7 human breast, HT-29 human colon, and LNCaP human prostate cancer cells by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Their stability/degradation (1) in human serum, (2) in the presence of rat liver lysosomal homogenate, and (3) in the presence of digestive enzymes (trypsin, chymotrypsin, and pepsin) was analyzed by liquid chromatography in combination with mass spectrometry. The results showed that (1) all synthesized bioconjugates had in vitro cytostatic effect, (2) they were stable in human serum at least for 24 h, and (3) they were hydrolyzed in the presence of lysosomal homogenate. All compounds were stable in the presence of (1) pepsin and (2) trypsin (except for the (4)Lys containing bioconjugate). In the presence of chymotrypsin, all bioconjugates were digested; the degradation rate strongly depending on their structure. The bioconjugates in which (4)Ser was replaced by N-Me-Ser or Lys(Ac) had the highest enzymatic stability, making them potential candidates for oral administration. In vivo tumor growth inhibitory effect of two selected bioconjugates was evaluated on orthotopically developed C26 murine colon carcinoma bearing mice. The results indicated that the compound containing Lys(Ac) in position 4 had significantly higher antitumor activity than the parent bioconjugate.

Structure, enzymatic stability and antitumor activity of sea lamprey GnRH-III and its dimer derivatives.

Direct antitumor activity of sea lamprey (Petromyzon marinus) gonadotropin-releasing hormone III (Glp-His-Trp-Ser-His-Asp-Trp-Lys-Pro-Gly-NH(2); lGnRH-III) was described on several tumor cells. To improve the selectivity of antitumor effects without increasing the hormone releasing activity and to enhance the enzymatic stability, lGnRH-III dimers were prepared via disulfide bond formation. Our results demonstrate that the lGnRH-III dimer derivatives exhibited higher antiproliferative effect and enzymatic stability in comparison with the native lGnRH-III, while lower LH-releasing potency was determined. In order to find a correlation between the biological and structural features of these compounds, the conformation of lGnRH-III and its dimer derivatives was determined by ECD, VCD, FT-IR and (1)H NMR.

Anticancer drug delivery systems containing GnRH-III as a targeting moiety

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