Houttuynia cordata Thunb. Hexane fraction induces MDA-MB-231 cell apoptosis via caspases, ER stress, cell cycle arrest and attenuated Akt/ERK signaling

Houttuynia cordata Thunb. (HCT) is a perennial plant used in traditional Thai medicine for many centuries. This study aimed to investigate the antiproliferative effect of the hexane fraction, which has not been explored before. HCT ethanol extract (crude extract) was sequentially fractionated to obtain a hexane (H) fraction. GC-MS was used to determine the phytochemicals. The H fraction consisted of lipids, mainly α-linolenic acid and some terpenoids. MTT assay was used to determine the cytotoxic effects of H fraction in MCF-7, MDA-MB-231, NIH3T3 and PBMCs. The mode of cell death and cell cycle analysis were determined by flow cytometry. The mechanisms of cell death were defined by mitochondrial transmembrane potential (MTP) reduction and activation of caspase-3, -8 and -9. The expression levels of the Bcl-2 family, cell cycle-related, endoplasmic reticulum (ER) stress-associated proteins; and Akt/ERK signaling molecules were investigated by immunoblotting. The H fraction was toxic to MDA-MB-231 more than MCF-7 cells but not to NIH3T3 and PBMCs. The growth of MDA-MB-231 cells was inhibited through apoptosis. MTP was disrupted whereas caspase-3, -8 and -9 were activated. The expression of pro-apoptotic Bax and Bak was upregulated, while Bid and anti-apoptotic Bcl-xL proteins were downregulated. Cyclin D1 and CDK4 levels were downregulated. The cell cycle was arrested at G1. Moreover, GRP78 and CHOP elevation indicated ER stress-mediated pathway. The expression ratio of pAkt/Akt and pERK/ERK were reduced. Taken together, the molecular mechanisms of MDA-MB-231 cell apoptosis were via intrinsic/extrinsic pathways, cell cycle arrest, ER stress and abrogation of Akt/ERK survival pathways. According to the most current research, the H fraction may be used as an adjuvant in the BC treatment; however, before the anticancer strategy can be applied to patients, it is important to determine each active compound's effects in cell lines and in vivo when compared with a combined mixture.

Anti-cancer Effect and Active Phytochemicals of Houttuynia cordata Thunb. against Human Breast Cancer Cells

BACKGROUND

Houttuynia cordata Thunb (HCT) is a medicinal herb used in Southeast Asia. Aim of this work: This study aimed at investigating the cytotoxicity of this plant extract and fractions towards human breast cancer MDA-MB-231 and MCF-7 cells. HCT's phytoactive compounds are determined.

MATERIALS AND METHODS

Cell viability was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The mode of cell death was measured by staining with annexin V-FITC and propidium iodide (PI) employing flow cytometry technique. The oxidative stress was measured by using 2',7'-dihydrodichlorofluorescein diacetate (DCFH-DA) and dihydroethidium (DHE+) fluorescent probes and using a fluorescence microplate reader. HCT phytochemicals were characterized by high performance liquid chromatography (HPLC).

RESULTS

The proliferation of MDA-MB-231 and MCF-7 cells was dramatically decreased by the crude extract and individual fraction of HCT. Ethyl acetate was the solvent fraction with the highest toxicity against MCF-7 cells, followed by dichloromethane, crude, and hexane fractions, respectively, whereas in MDA-MB231 cells, dichloromethane, crude, hexane, and ethyl acetate fractions each had the strongest impact, respectively. The methanol fraction had no effect on either cell line up to 200 μg/ml. The extract and fractions were less harmful to the NIH3T3 normal murine fibroblast cell line. The mode of both cell death was apoptosis evidenced by the increase of cell population stained with annexin V-FITC and PI. The fluorescence probes of both DCFH-DA and DHE in MDA-MB-231 cell line were enhanced. Phenolic acids included chlorogenic acid (CA), gallic acid (GA), transcoumaric acid (TCA), vanillic acid (VA), and syringic acid (SA), as well as flavonoids like quercetin and rutin, were identified as the active phytochemicals in the crude and fractions by using HPLC method.

CONCLUSION

MDA-MB-231cells underwent apoptosis via oxidative stress when induced with HCT hexane fraction. Phenolic acids and flavonoids were identified in HCT's extract and fractions.