The Effects of Apigenin on Cell Proliferation and Apoptosis in Glioblastoma Multiforme

Glioblastoma multiforme (GBM) is a WHO grade IV brain tumor. These tumors are highly proliferative, infiltrative, necrotic, angiogenic, and resistant to apoptosis. One major characteristic of GBM is the overexpression of epidermal growth factor receptor (EGFR), which leads to cell growth and proliferation when activated. GBM is very difficult to treat due to its location, heterogeneity, and invasiveness; an effective treatment is therefore needed. The use of flavonoids, which are natural compounds found in many fruits and vegetables, has been studied in the treatment of many different tumor types. Apigenin is a specific flavonoid that has previously been shown to have antitumor activity in a number of cancer cells. Our study set out to investigate the molecular effects of apigenin treatment on glioblastoma cell proliferation and viability using the trypan blue exclusion assay, MTT assay, and an LDH assay. In addition, Western blot analyses were utilized out to determine the signaling pathways through which apigenin treatment exerts its effects on cell proliferation and apoptosis. Finally, hoechst-propidium iodide staining and flow cytometry were used to examine the extent of apoptosis and the cell cycle context of these effects. Our results show that apigenin reduces cell viability and proliferation in a dose and time dependent manner while increasing cytotoxicity in GBM cells. Additionally, apigenin inhibits the EGFR mediated phosphorylation in the presence of EGF treatment of AKT, mTOR, and s6k resulting in decreased cell survival, growth and proliferation. It also inhibits the MAPK pathways in one cell line thereby reducing cell growth and proliferation. It also inhibits the anti-apoptotic effects of BCL-XL and increases PARP cleavage, which leads to increased apoptosis. Finally, apigenin induced cycle arrest at the G2M checkpoint, meaning that apoptosis primarily occurred at the DNA repair checkpoint in the cell cycle. In conclusion, apigenin has demonstrated some in vitro biological effects on glioblastoma cell lines that show promises in limiting the growth, proliferation and survival of these cell lines. Future research should look to identify means through which apigenin can be administered in clinically significant concentrations to the brain

The Antiproliferative and Apoptotic Effects of Apigenin on Glioblastoma Cells

OBJECTIVES: Glioblastoma (GBM) is highly proliferative, infiltrative, malignant and the most deadly form of brain tumour. The epidermal growth factor receptor (EGFR) is overexpressed, amplified and mutated in GBM and has been shown to play key and important roles in the proliferation, growth and survival of this tumour. The goal of our study was to investigate the antiproliferative, apoptotic and molecular effects of apigenin in GBM. METHODS: Proliferation and viability tests were carried out using the trypan blue exclusion, MTT and lactate dehydrogenase (LDH) assays. Flow cytometry was used to examine the effects of apigenin on the cell cycle check-points. In addition, we determined the effects of apigenin on EGFR-mediated signalling pathways by Western blot analyses. KEY FINDINGS: Our results showed that apigenin reduced cell viability and proliferation in a dose- and time-dependent manner while increasing cytotoxicity in GBM cells. Treatment with apigenin-induced is poly ADP-ribose polymerase (PARP) cleavage and caused cell cycle arrest at the G2M checkpoint. Furthermore, our data revealed that apigenin inhibited EGFR-mediated phosphorylation of mitogen-activated protein kinase (MAPK), AKT and mammalian target of rapamycin (mTOR) signalling pathways and attenuated the expression of Bcl-xL. CONCLUSION: Our results demonstrated that apigenin has potent inhibitory effects on pathways involved in GBM proliferation and survival and could potentially be used as a therapeutic agent for GBM