MK615, a prospective anti-proliferative agent, enhances CD4/CD8 ratio after exposure to irradiation WAEL S. AL-JAHDARI 1,2 , HIDEYUKI SAKURAI 1 , YUKARI YOSHIDA 1,3 , ABDULELAH MOBARAKI 1 , YOSHIYUKI SUZUKI 1 , & TAKASHI NAKANO 1,3 1 Department of Radiation Oncology, Gunma University Graduate School of Medicine, Gunma, 2 Japan Society for the Promotion of Science, Chiyoda, Tokyo, and 3 The 21st Century Center of Excellence (COE) Program for Biomedical Research Using Accelerator Technology, Gunma University, Graduate School of Medicine, Gunma, Japan (Received 15 July 2009; Revised 10 August 2010; Accepted 18 August 2010) Abstract Purpose: Recently, it was found that MK615 possessed an anti-proliferative ability on treated cancer cells as a consequence of triterpenoid compounds. It is well known that radiation affects cellular-mediated immunity in cancer patients who are treated with radiotherapy. Similarly, the ability of triterpenoid compounds to enhance the cellular-mediated immunity has been observed. Therefore, in the present study, we attempted to investigate the effect of MK615 on both cancer cells and cellular-mediated immunity after irradiation. Materials and methods: After mice were inoculated with mouse mammary carcinoma (FM3A) cells, they were categorised as follows: Non-treated, irradiated with 5 Gy, treated with 660 mg/day MK615 (MK615, an extract from the Japanese apricot) and lastly exposed to both irradiation and MK615. Afterward, mice were sacrificed and spleens were utilised to measure the cluster of differentiation 4 and 8 (CD4 and CD8) using flowcytometry. Simultaneously, in vitro study, human alveolar basal epithelial carcinomic (A549), mouse lymphoma (EL4) and FM3A cell lines were examined. Growth inhibition was assessed via colony, cell viability and apoptotic assays. Results: The median survival was in favour of the MK615-treated group (26.1 + 1.9 days) compared with non-treated group (22.3 + 2.3 days) (p 5 0.05). Approximately 50% reduction of the CD4/CD8 ratio was observed following the exposure to irradiation alone. However, this ratio was comparable between the non-treated and both MK615-treated groups. Additionally, only the dual treatment was associated with tumour volume reduction. In contrast, in vitro study showed that MK615 had no significant (p  0.1) effect on the selected cell lines with or without irradiation. Conclusion: MK615 has a potential to reduce tumour volume and may normalise cellular-mediated immunity level following the exposure to irradiation. Keywords: MK615, irradiation, CD4/CD8 ratio, triterpenoids Introduction Recently, the biological activities of triterpenoids have gained a wide interest. There are various appraisals have appeared on various aspects of the activities of triterpenoids. Triterpenoids were found to possess immune-stimulation (Marciani et. al. 2000), anti tumour-promoting activity (Takasaki et al. 2003), anti-inflammatory activity (Akihisa et al. 1996), bio-activities of saponins (Manez et al. 1997), plant-defence compounds from oat roots (Rao and Gurfinkel 2000) and the aphrodisiac and adaptogenic properties of ginseng (Nocerino et al. 2000a). Triterpenoids have different constituents and structural properties that are found in several species (Hasler et al. 1990, Brinkhaus et al. 2000, Nocerino et al. 2000b, Jiang et al. 2008). One of these species is MK615 which is an extract compound from Japanese apricot ‘‘Prunus mume Sieb. et Zucc’’. MK615 has for centuries been used as a traditional Japanese medicine (Adachi et al. 2007). It contains various chemical substances such as citric acid, malic acid, cyanogenic glycosides, carbohydrate, protein, fat, sodium, potassium, iron zinc and triterpenoids. Chromatographically, MK615 contains different types of triterpenoids such as ursolic acid, oleanolic acid, lupeol, a-amyrin, cycloartenol, and 24-methylencycloartanol (Yamai Correspondence: Dr Takashi Nakano, MD, PhD, Department of Radiation Oncology, Gunma University Graduate School of Medicine, 3-39-22 Showa- machi, Maebashi, Gunma, 371-8511, Japan. Tel: þ81 27220 8383. Fax: þ81 27220 8397. E-mail: tnakano@med.gunma-u.ac.jp Int. J. Radiat. Biol., Vol. 87, No. 1, January 2011, pp. 81–90 ISSN 0955-3002 print/ISSN 1362-3095 online Ó 2011 Informa UK, Ltd. DOI: 10.3109/09553002.2010.518202