Onosma species (Boraginaceae) are well known as medicinal plants due to their wide range of pharmaceutical potential. The present study aims to investigate the anticancer (in vitro) and chemo-protective (in vivo) efficacies of Onosma mutabilis extract (OME) in the azoxymethane (AOM)-induced aberrant crypt foci (ACF) in rats. The in vitro antiproliferative effects of OME were determined on two human tumor cell lines (Caco-2 and HT-29) via MTT assay. The in vivo chemoprotective effects of OME were investigated by performing various biochemical analyses in serum and tissue homogenates of albino rats, along with determining oxidative stress biomarkers. Inflammatory biomarkers of colon, colonic gross morphology (by methylene blue), ACF formation, and colonic histopathology (H & E stain) were determined. The immunohistochemistry of colonic tissues was also assessed by Bax and Bcl-2 protein expression. The results showed that the antitumor activity of OME against Caco-2 and HT-29 colorectal cancer cells ranged between 22.28-36.55 µg/mL. OME supplementation caused a significant drop in the ACF values and improved the immunohistochemistry of the rats shown by up-regulation of Bax and down-regulation of Bcl-2 protein expressions. These outcomes reveal that O. mutabilis may have chemoprotective efficiency against AOM-induced colon cancer represented by the attenuation of ACF formation possibly through inhibition of free radicals, inflammation, and stimulation of the colon antioxidant armory (SOD, CAT, and GPx) and positive regulation of the Nrf2-Keap1 pathway.
Keywords: Boraginaceae; chemoprevention; colon cancer; histopathology; oxidative stress.