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Verbascoside Attenuates Rac-1 and HIF-1α Signaling Cascade in Colorectal Cancer Cells.

OBJECTIVE
Metastasis phenotype is considered as the main challenge in colon cancer therapeutic methods. Furthermore, the side effects of conventional colorectal cancer treatment methods have attracted a lot of attention into natural ingredients. The aim of the study was to assess the molecular mechanism of verbascoside as natural bio-compound in human HT29 colon cancer cells.


METHODS
HT29 cells were cultured in RPMI-1640 medium containing 10% FBS and 1% penicillin/ streptomycin at 37°C and 5% CO2. HT-29 cells were treated with different concentrations of verbascoside (10, 20, 30, 40, 50, 70, 100 µg/ml) for 24 hours, then MTT assay was used to calculate 50% inhibitory concentration. The migration of the colon cancer cells was evaluated by scratch assay. To evaluate involved antiproliferative mechanism, Rac-1 (Ras-related C3 botulinum toxin substrate 1) and HIF-1α (hypoxia-inducible factor-1α) related gene expression were evaluated by Real Time PCR.


RESULTS
The results showed that verbascoside inhibited HT29 colon cancer cell proliferation dose-dependently and IC50 was evaluated as 50 μg/ml (***P<0.001). The results of wound healing assay demonstrated verbascoside decreased cell migration in a dose dependent manner. In the IC50 treated HT29 cells metastatic progression was significantly suppressed as **P<0.01. The results of Real Time PCR showed an attenuating effect of verbascoside on Rac-1, Zeb-1 (zinc finger E-box binding homeobox 1), Arp2 (Actin-Related Proteins), Pak1 (p21 (RAC1) activated kinase 1), VEGF (Vascular endothelial growth factor) and HIF-1α as Epithelial-Mesenchymal Transition markers. The down regulation of mRNA levels was Rac-1= 15.38, HIF-1 α = 16.66, Pak-1, Arp-2= 6.25, VEGF=24.39, Zeb-1=35.71 in HT29 cells treated with IC50 concentration of verbascoside.


CONCLUSION
Colorectal cancer cells induce Rac-1 and HIF-1α overexpression which plays an important role in the activation and progression of cell motility, angiogenesis and metastasis. Overall results showed that verbascoside elucidated significant anti-metastatic and anti-invasion activities through suppression of Rac-1, HIF-1α, and Zeb-1 signaling pathway and it may be a suitable candidate to overwhelm colon cancer metastatic phenotype.