Hepatocellular carcinoma (HCC), the most common of the primary liver cancers, is the fifth most common malignancy in the world, as well as the second most frequent cause of cancer-related deaths worldwide [1, 2]. In China, HCC morbidity and mortality contribute to approximately 50% of total number of cases of liver cancer, as well as liver cancer-related deaths . Chemotherapy and surgery are effective methods for treatment of cancer [4, 5]. Unfortunately, the lack of effective and targeted drugs has led to a low five-year survival rate. One exception is sorafenib, a tyrosine protein kinase inhibitor . In addition, chemotherapy is often accompanied with serious side effects, including immunodeficiency, cell damage, and neurological, renal, and cardiac toxicity. Over the past 10 years, the global incidence of liver cancer has not been effectively controlled . Therefore, it is necessary to identify and develop natural anti-cancer drugs with good anti-tumor activity, as well as low side effects .
Flavonoids, which are plant-derived ubiquitous components of the human diet, are thought to be promising candidates for the prevention and treatment of cancer [9, 10]. They are low molecular weight compounds that are comprised of a three-ring structure with various substitutions . Flavonoids possess anti-tumor activity against various human cancer cell lines and xenograft systems of human tumors, which suggests the presence of potential anti-cancer agents .
Diosmin, a flavonoid, was initially isolated from Scrophularia nodosa in 1925, and then utilized as a medicine for venous lymphatic insufficiency in 1969. Since then, scientists have carried out extensive research on its function. In addition, these results indicate that diosmin can be used for the treatment of hemorrhoids, lymphedema and varicose veins . It has also been reported that diosmin exhibits anti-cancer, antimicrobial, antioxidant, oestrogenic and anti-inflammatory activities . We have discovered that diosmin has the opposite effect, such as antiproliferative and pro-apoptotic activity, on tumor cells. This includes oral cancer cells, colon cancer cells, breast cancer cells and liver cancer cells [15, 16, 17].
Nevertheless, the antitumor mechanism of diosmin remains unknown. In addition, research on proliferation inhibition of diosmin in HepG2 cells has rarely been reported. Network pharmacology and molecular docking technology are emerging and promising techniques in pharmacological research over recent years . Molecular docking has been applied to evaluate the relationship between small molecule compound ligands and macromolecular bioreceptors via molecular mechanics energy analysis. It has been widely used in virtual screening of target proteins, and elucidating the mechanisms of action. The credibility of the results has been validated among various molecular pharmacological experiments .
Herein, we analyzed and identified potential target proteins of diosmin from the PharmMapper and Genecards database, the string database and Gene Ontology Resource. Moreover, we identified the main tumor suppressor pathway of diosmin using KEGG analysis. Furthermore, we performed molecular docking analysis to determine the site of action of the main target proteins, using the small molecule diosmin as substrate. Finally, western blot technology was utilized to determine the function of diosmin in inhibiting proliferation of HepG2 cells. These results provide a scientific theoretical basis for the development of anti-cancer drugs through the use of diosmin as the lead or analogue. Fig. 1 depicts the flowchart of our study.