Beta-Caryophyllene (BCP), a naturally occurring sesquiterpene abundantly found in cloves, hops, and cannabis, is the active candidate of a relatively new group of vascular-inhibiting compounds that aim to block existing tumor blood vessels. Previously, we have reported the anti-cancer properties of BCP by utilizing a series of in-vitro anti-tumor-related assays using human colorectal carcinoma cells. The present study aimed to investigate the effects of BCP on in-vitro, ex-vivo, and in-vivo models of anti-angiogenic assays and evaluate its anti-cancer activity in xenograft tumor (both ectopic and orthotopic) mice models of human colorectal cancer. Computational structural analysis and an apoptosis antibody array were also performed to understand the molecular players underlying this effect. BCP exhibited strong anti-angiogenic activity by blocking the migration of endothelial cells, tube-like network formation, suppression of vascular endothelial growth factor (VEGF) secretion from human umbilical vein endothelial cells and sprouting of rat aorta microvessels. BCP has a probable binding at Site#0 on the surface of VEGFR2. Moreover, BCP significantly deformed the vascularization architecture compared to the negative control in a chick embryo chorioallantoic membrane assay. BCP showed a remarkable reduction in tumor size and fluorescence molecular tomography signal intensity in all the mice treated with BCP, in a dose-dependent relationship, in ectopic and orthotopic tumor xenograft models, respectively. The histological analysis of the tumor from BCP-treated mice revealed a clear reduction of the density of vascularization. In addition, BCP induced apoptosis through downregulation of HSP60, HTRA, survivin, and XIAP, along with the upregulation of p21 expressions. These results suggest that BCP acts at multiple stages of angiogenesis and could be used as a promising therapeutic candidate to halt the growth of colorectal tumor cells.
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.