Evaluation of the Effects of the Flavonoid Apigenin on Apoptotic Pathway Gene Expression on the Colon Cancer Cell Line (HT29)

Abstract

Apigenin (4',5,7-trihydroxyflavone) is one of the leading components supporting targeted treatment options. We explored the cytotoxic and apoptotic effects of various doses of apigenin administered alone and together with 5-fluorouracil (5-FU)-a chemotherapeutic agent with high cytotoxicity-for different incubation periods, on morphologic, DNA, RNA (messenger RNA [mRNA]), and protein levels on the p53 mutant HT29 human colon adenocarcinoma cell line. Treatment with apigenin alone for a 72-hour incubation at 90-μM dose resulted in an apoptotic percentage of 24.92% (P=.001). A higher percentage (29.13%) was observed after treatment with the same dose of apigenin plus 5-FU for the same incubation period (P=.001). These results were confirmed as mRNA and protein expression levels of caspase-3 increased 2.567-fold and mRNA expression levels of caspase-8 increased 3.689-fold compared with the control group. On the other hand, mRNA expression levels of mammalian target of rapamycin (mTOR) and cyclin D1 (CCND1) decreased by 0.423-fold and 0.231-fold, respectively. To our knowledge this is the first study showing that treatment with apigenin alone results in cell cycle arrest through activation of caspase cascade and stimulation of apoptosis in HT29 cells. It also shows that use of apigenin plus 5-FU further increases this effect. This study draws attention to the probable clinical effectiveness of apigenin plus a chemotherapeutic agent with high cytotoxicity. It also highlights the induction of desirable apoptotic effects by targeting the caspase cascade pathway through administration of reduced doses for shorter incubation periods.

Plant Flavone Apigenin: an Emerging Anticancer Agent

“…The same study also exhibited that apigenin could activate p53 by phosphorylating it at Ser-37 and Ser-15 via the ataxia telangiectasia mutated (ATM) pathway to potentiate apoptosis. Turketekin et al [79] reported that apigenin-induced cell cycle arrest and apoptosis in p53 mutant colon cancer cells. Similar studies also show that apigenin possesses autophagy-inducing effects in HCT116 colon cancer cells, and combined treatment with inhibitor 3-methyladenine (3-MA), an autophagy inhibitor, potentiates apoptosis [80].…”

Plants vs. Cancer: A Review on Natural Phytochemicals in Preventing and Treating Cancers and Their Druggability

“…Apigenin is also being considered as a mediator for chemoprevention in the cancerous process and induces a process of autophagia but may induce resistance against chemotherapy [35]. It induces apoptosis in human colon cancer cells [36, 37], reduces azoxymethane (AOM) induced aberrant crypt foci (ACF) formation in male Sprague-Dawley rats, and increases apoptosis which may contribute to the colon cancer prevention [38]. Apigenin affects leptin/leptin receptor pathway, and induces cell apoptosis in lung adenocarcinoma cell line [39].…”

Insights into novel anticancer applications for apigenin

“…17 Besides induction of p21/WAF1 protein (which is also involved in the cell division cycle), apigenin also leads to changes in the phosphorylation of p53 tumor suppressor protein, induction of the nonsteroidal anti-inflammatory drug-activated gene (a growth factor involved in anti-tumorigenesis) and caspase-3 activity. 18,19 Another way in which this flavonoid promotes programmed cell death is through the modification of the Bax/Bcl-2 protein ratio and the release of cytochrome C to the cytoplasm, which binds apoptotic protease activating factor-1.…”