Conjugates of daidzein-alliinase as a targeted pro-drug enzyme system against ovarian carcinoma

Abstract

Human ovarian cancer cells specifically bind the isoflavone daidzein. A chemical conjugate between daidzein and the garlic enzyme alliinase was prepared. The conjugate specifically bound to ovarian cancer cells and upon addition of the prodrug alliin, it effectively produced cytotoxic allicin molecules which killed the cancer cells. In vivo targeting and antitumor effect was confirmed by NIR and bioluminescence imaging using daidzein-alliinase-CyTE-777 conjugates and luciferase-expressing ovarian cancer cells. Co-localization of the fluorescent conjugate with bioluminescence was observed for intraperitoneal tumors while nonconjugated alliinase did not accumulate. Biodistribution studies with Europium-labeled conjugate revealed a five fold higher uptake in tumors as compared to other tissues. Treatment of tumor bearing mice with daidzein-alliinase and alliin effectively attenuated tumor progression during the first 12 days while a 5-fold increase in bioluminescence was detected in placebo-treated animals. Autopsy revealed only small individual foci of luminescence at the site of tumor cells inoculation. Histological examination of organs and tissues did not reveal any additional foci of carcinoma or signs of toxicity. These results suggest that the targeted alliinase conjugates in the presence of alliin, generated therapeutically effective levels of allicin which were capable of suppressing tumor progression of intraperitoneal ovarian cancer in an animal model.

Keywords::

• Alliinase
• alliin
• allicin
• ovarian carcinoma
• drug targeting
• daidzein

Acknowledgements

We would like to thank Dr. Alex Starr from the Sourasky Medical Center in Tel Aviv, Israel, for the clinical examination of the peritoneal cavity and thorax of tumor bearing mice, Helena Sheikhet Migalovich and Dr. Vyacheslav Kalchenko for advice in the IVIS imaging studies, to Dr. Irina Shin for characterization of alliinase and to Prof. Meir Wilchek for helpful discussions. This investigation was supported by a grant from the Gurwin Foundation at the Weizmann Institute. MN is incumbent of the Helen and Morris Mauerberger Chair. DM is incumbent of the Besen-Brender Chair.

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.