Dual properties of hispidulin: antiproliferative effects on HepG2 cancer cells and selective inhibition of ABCG2 transport activity

• Published in: Molecular and cellular biochemistry 2015-11, Vol.409 (1-2), p.123-133
• Main Authors: Scoparo, Carina T., Valdameri, Glaucio, Worfel, Paulo R., Guterres, Fernanda A. L. B., Martinez, Glaucia R., Winnischofer, Sheila M. B., Di Pietro, Attilio, Rocha, Maria E. M.
• Format: Article
• Language: English
• Subjects: Acetylcysteine; Analysis; Animals; Antioxidants; Antioxidants - pharmacology; Apoptosis - drug effects; ATP Binding Cassette Transporter, Sub-Family G, Member 2; ATP-Binding Cassette Transporters - antagonists & inhibitors; Biochemistry; Bioflavonoids; Biological Transport - drug effects; Biomedical and Life Sciences; Cancer; Cancer cells; Carcinoma, Hepatocellular - drug therapy; Carcinoma, Hepatocellular - pathology; Cardiology; Catalase - biosynthesis; Catalase - genetics; Cell Line, Tumor; Cell Proliferation - drug effects; Cell Survival - drug effects; Cellular biology; Drug resistance; Enzymatic activity; Enzymes; Flavones; Flavones - pharmacology; Flavonoids; Glutathione - metabolism; Health aspects; HEK293 Cells; Hep G2 Cells; Herbal medicine; Humans; Hydrogen peroxide; L Cells (Cell Line); Life Sciences; Liver Neoplasms - drug therapy; Liver Neoplasms - pathology; Medical Biochemistry; Mice; Mitoxantrone - metabolism; Multidrug Resistance-Associated Proteins - biosynthesis; Oncology; Plants, Medicinal - metabolism; Prevention; Reactive Oxygen Species - metabolism; RNA; RNA, Messenger - biosynthesis; Side effects
• ISSN: 0300-8177; 1573-4919
• DOI: 10.1007/s11010-015-2518-8

Hepatocellular carcinoma is the third most common cause of cancer-related deaths worldwide. Furthermore, the existing pharmacological-based treatments are insufficiently effective and generate many side effects. Hispidulin (6-methoxy-5,7,4′-trihydroxyflavone) is a flavonoid found in various medicinal herbs that present antineoplastic properties. Here we evaluated how modulation of reactive oxygen species (ROS) and alterations of antioxidant defenses could be associated to the antiproliferative effects of hispidulin in HepG2 cells. In addition, we studied the inhibitory activity of hispidulin on the efflux of drugs mediated by ABC transporters involved in multidrug resistance. In order to understand the increase of intracellular ROS promoted by hispidulin, we investigated the mRNA expression levels and activities of antioxidant enzymes, and the GSH/GSSG ratio. We showed that hispidulin significantly down-regulated the transcription levels of catalase, leading to reduction of enzyme activity and decrease of the GSH content. We also observed that, in the presence of N -acetylcysteine or exogenous catalase, the proliferation was lowered back to the control levels. These data clearly indicate a strong involvement of intracellular ROS levels for triggering the antiproliferative effects. We also demonstrated that the inhibition produced by hispidulin on drug efflux was specific for ABCG2, since no effects were observed with ABCB1 and ABCC1. Furthermore, HepG2 cells were more sensitive to hispidulin-mediated cell death than immortalized L929 fibroblasts, suggesting a differential toxicity of this compound between tumor and non-tumor cell lines. Our results suggest that hispidulin constitutes a promising candidate to sensitize chemoresistant cancer cells overexpressing ABCG2.