ETHNOPHARMACOLOGICAL RELEVANCE: Annona muricata known as "the cancer killer" has been widely used in the traditional medicine for the treatment of cancer and tumors. The purpose of this study is to investigate the anticancer properties of ethyl acetate extract of Annona muricata leaves (EEAM) on HT-29 and HCT-116 colon cancer cells and the underlying mechanisms.
MATERIALS AND METHODS: The effect of EEAM on the cell proliferation of HT-29 and HCT-116 cells was analyzed by the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium) assay. High content screening system (HCS) was applied to investigate the cell membrane permeability, mitochondrial membrane potential (MMP), nuclear condensation and cytochrome c translocation from mitochondria to cytosol. Reactive oxygen species (ROS) formation, lactate dehydrogenase (LDH) release and activation of caspase-3/7, -8 and -9 were measured while treatment. Flow cytometric analysis was used to determine the cell cycle distribution and phosphatidylserine externalization. The protein expression of Bax and Bcl-2 was determined using immunofluorescence analysis. In addition, the potential of EEAM to suppress the migration and invasion of colon cancer cells was also examined.
RESULTS: EEAM exerted significant cytotoxic effects on HCT-116 and HT-29 cells as determined by MTT and LDH assays. After 24 h treatment, EEAM exhibited the IC₅₀ value of 11.43 ± 1.87 µg/ml and 8.98 ± 1.24 µg/ml against HT-29 and HCT-116 cells, respectively. Flow cytometric analysis demonstrated the cell cycle arrest at G1 phase and phosphatidylserine externalization confirming the induction of apoptosis. EEAM treatment caused excessive accumulation of ROS followed by disruption of MMP, cytochrome c leakage and activation of the initiator and executioner caspases in both colon cancer cells. Immunofluorescence analysis depicted the up-regulation of Bax and down-regulation of Bcl-2 proteins while treated with EEAM. Furthermore, EEAM conspicuously blocked the migration and invasion of HT-29 and HCT-116 cells.
CONCLUSIONS: These findings provide a scientific basis for the use of A. muricata leaves in the treatment of cancer, although further in vivo studies are still required.
We recently reported the antineovascularization effect of scopoletin on rat aorta and identified its potential anti-angiogenic activity. Scopoletin could be useful as a systemic chemotherapeutic agent against angiogenesis-dependent malignancies if its antitumorigenic activity is investigated and scientifically proven using a suitable human tumor xenograft model. In the present study, bioassay-guided (anti-angiogenesis) phytochemical investigation was conducted on Nicotiana glauca extract which led to the isolation of scopoletin. Further, anti-angiogenic activity of scopoletin was characterized using ex vivo, in vivo and in silico angiogenesis models. Finally, the antitumorigenic efficacy of scopoletin was studied in human colorectal tumor xenograft model using athymic nude mice. For the first time, an in vivo anticancer activity of scopoletin was reported and characterized using xenograft models. Scopoletin caused significant suppression of sprouting of microvessels in rat aortic explants with IC50 (median inhibitory concentration) 0.06μM. Scopoletin (100 and 200mg/kg) strongly inhibited (59.72 and 89.4%, respectively) vascularization in matrigel plugs implanted in nude mice. In the tumor xenograft model, scopoletin showed remarkable inhibition on tumor growth (34.2 and 94.7% at 100 and 200mg/kg, respectively). Tumor histology revealed drastic reduction of the extent of vascularization. Further, immunostaining of CD31 and NG2 receptors in the histological sections confirmed the antivascular effect of scopoletin in tumor vasculature. In computer modeling, scopoletin showed strong ligand affinity and binding energies toward the following angiogenic factors: protein kinase (ERK1), vascular endothelial growth factor A (VEGF-A), and fibroblast growth factor 2 (FGF-2). These results suggest that the antitumor activity of scopoletin may be due to its strong anti-angiogenic effect, which may be mediated by its effective inhibition of ERK1, VEGF-A, and FGF-2.