Inhibition of 4-NQO-induced F433 rat tongue carcinogenesis by oleuropein-rich extract

Olive leaf extract provides nutritional support for detoxification at the cellular level, when the body is under stress. The present study aimed to evaluate the chemopreventive effect of oleuropein-rich extract (ORE) on 4-NQO-induced rat tongue carcinogenesis. Eighty male F344 rats, 6 weeks age were divided into 5 groups (10 animals each for groups 1 and 2 and 20 each for groups 3, 4, and 5). Group 1 served as an untreated control. Group 2 was given ORE-containing diet alone. Rats of groups 3, 4, and 5 were given daily 20 ppm 4-NQO in drinking water for 8 weeks. Group 4 was fed diets containing ORE, concomitantly with the time of carcinogen exposure and continued 1 week after its stoppage. Group 5 was fed diets mixed with ORE starting 1 week after cessation of 4-NQO treatment. The experiment was terminated when the rats aged 37 weeks, and all animals were euthanized. The tongues were carefully inspected for pathological lesions, excised, and were processed for c-Met and Ki-67 immunohistochemical examination. The gross inspection, histopathological and immunohistochemical results of the present study showed a beneficial regression effect of ORE on tumor progression, especially when it was administered concomitantly with 4-NQO rather than when given after the stoppage of the carcinogenic material. In conclusion, ORE has a chemopreventive role in tongue squamous cell carcinoma, and further studies are needed to explore the molecular mechanisms of its tumor suppressive effect at this level.