Abstract
Thunbergia Laurifolia Linn. (TL) is one of the most familiar plants in Thai traditional medicine that is used to treat various conditions, including cancer. However, the antitumor activity of TL or its constituents has never been reported at the molecular level to support the folklore claim. The present study was designed to investigate the antitumor effect of an aqueous extract of TL in human breast cancer cells and the possible mechanism(s) of action. An aqueous crude extract was prepared from dried leaves of TL. Folin-Ciocalteu colorimetric assays were used to determine the total phenolic content. Antiproliferative and cell cycle effects were evaluated in human breast adenocarcinoma MCF-7 cells by MTT reduction assay, cell growth inhibition, clonogenic cell survival, and flow cytometric analysis. Free radical generation by the extracts was detected using electron paramagnetic resonance spectroscopy. The exposure of human breast adenocarcinoma MCF-7 cells to a TL aqueous extract resulted in decreases in cell growth, clonogenic cell survival, and cell viability in a concentration-dependent manner with an IC50 value of 843 μg/ml. Treatments with extract for 24 h at 250 μg/ml or higher induced cell cycle arrest as indicated by a significant increase of cell population in the G1 phase and a significant decrease in the S phase of the cell cycle. The capability of the aqueous extract to generate radical intermediates was observed at both high pH and near-neutral pH conditions. The findings suggest the antitumor bioactivities of TL against selected breast cancer cells may be due to induction of a G1 cell cycle arrest. Cytotoxicity and cell cycle perturbation that are associated with a high concentration of the extract could be in part explained by the total phenolic contents in the extract and the capacity to generate radical intermediates to modulate cellular proliferative signals.
Highlights
The efficacy of polyphenols for cancer treatment has emerged as alternative to pharmacological agents in recent years
The exposure of human breast adenocarcinoma MCF-7 cells to a Thunbergia Laurifolia Linn. (TL) aqueous extract resulted in decreases in cell growth, clonogenic cell survival, and cell viability in a concentration-dependent manner with an IC50 value of 843 μg/ml
The findings suggest the antitumor bioactivities of TL against selected breast cancer cells may be due to induction of a G1 cell cycle arrest
Summary
The efficacy of polyphenols for cancer treatment has emerged as alternative to pharmacological agents in recent years. (TL) is a medium sized climbing plant of the family Acanthaceae usually found in moist and gallery evergreen areas. It is commonly known as Babbler’s Bill Leaf or Laurel Clock Vine or Rang Chuet in Thai. Ethanolic, and organic solvent-extracts of TL were demonstrated to exhibit powerful antioxidant activity in vitro and showed pharmacological effectiveness in various animals models (Hanchaipiboonkun, 2008; Palipoch et al, 2011; Wonkchalee et al, 2012; Thongsaard and Marsden, 2013; Boonyarikpunchai et al, 2014; Khobjai et al, 2014; Rojsanga et al, 2015). Methanolic extracts of TL were demonstrated to minimize the adverse effects of toxicants by regulating P-glycoprotein activity, CYP450, and lipid metabolism gene expression in HepG2 cells (Rocejanasaroj et al, 2014). The cytotoxic effects of TL and it’s likely mechanism in modifying the phenotype of human cancer cells have never been reported
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