Protective role of Egyptian propolis against tumor in mice Om-Ali Y. El-khawaga a, * , Tarek A. Salem b , Mohamed F. Elshal b a Biochemistry Division, Chemistry Department, Faculty of Science, Mansoura University, Mansoura City, Egypt b Molecular Biology Department, Genetic Engineering and Biotechnology Institute, Menofiya University, Mansoura City, Egypt Received 2 May 2003; received in revised form 6 July 2003; accepted 7 July 2003 Abstract Background: Propolis has numerous biologic activities including antibiotic, antifungal, antiviral and anti-inflammatory properties. The present work is aimed to study the effect of crude Egyptian propolis on tumor in mice induced by Ehrlich ascitis carcinoma (EAC) cell line. Results: The administration of propolis (160 mg/kg body weight), by gastric intubation 2 h before the intraperitoneal injection of EAC, effectively inhibited tumor growth and the proliferation of EAC. The tumor volume was markedly reduced from 7 F 0.9 ml in EAC-infected mice to 1.6 F 0.95 ml in propolis-treated mice. Also, the lipid peroxide level which was 13.3 F 1.24 nmol malodialdehyde (MDA)/mg protein in EAC infected mice was significantly decreased to 3.3 F 2.1 nmol MDA/mg protein. Reduced glutathione (GSH) and glutathione S-transferase (GST) concentrations were markedly increased in propolis-treated mice. This effect was associated with inhibition of cell cycle progression and induction of apoptosis. Administration of propolis 2 h before injection of EAC arrested cells in G0/G1 phase and resulted in a decrease in the viability, DNA, total RNA and protein level of tumor cells. Conclusions: Crude Egyptian propolis has a strong inhibitory activity against tumors. The anti-tumor mechanism may be mediated by preventing oxidative damage and induction of apoptosis. D 2003 Published by Elsevier B.V. Keywords: Propolis; Ehrlich ascites carcinoma cells; Apoptosis; Oxidative stress and antioxidants 1. Introduction Cancer is considered one of the most common causes of morbidity and mortality worldwide. The target of much research has been on the discovery of natural and synthetic compounds that can be used in the prevention and/or treatment of cancer. Natural products of either plant or animal origin that exhibited antitumor activity have been discovered [1]. Propolis (bee glue) is a mixture of compounds obtained from beehives that has a strong character- istic smell and taste. The mixture contains a number of plant products including flavonoids and is de- posited in beehives by bees where it is thought to prevent microbial infection of the hive. Propolis has attracted the interest of many investigators because of its anti-bacterial [2], anti-viral [3], anti-inflam- matory [4], and immuno-stimulatory [5] effects. For many years, propolis has been used by laymen and physicians in attempts to treat a variety of human diseases. Chemical and pharmacological study of propolis from various locations was investigated by Papay et 0009-8981/$ - see front matter D 2003 Published by Elsevier B.V. doi:10.1016/S0009-8981(03)00323-1 * Corresponding author. Tel.: +20-50-6327112; fax: +20-50- 2246781. E-mail address: elkhawaga70s@mans.edu.eg (O.-A.Y. El-khawaga). www.elsevier.com/locate/clinchim Clinica Chimica Acta 338 (2003) 11 – 16