A comparative study of the antiproliferative effect of kohlrabi and green cabbage on colorectal cancer cell lines. (c2012)

Abstract

Experimental studies showed that phytochemicals from Brassicaceae Cruciferae vegetables possess anticarcinogenic properties. This association is attributed to glucosinolates molecules, mainly isothiocyanates and indoles released upon consumption of these vegetables. Two members of this family, namely cabbage (Brassica oleracea, group Capitata) and kohlrabi (Brassica oleracea, group Gongylodes) seem to share similar anticarcinogenic characteristics. The aim of this study is to compare the effect of the ethanolic extracts of the edible parts of these two plants on the proliferation and apoptosis of HT-29 and Caco-2 colorectal cancer cell lines. The cytotoxicity of the extracts was assayed using the Trypan Blue Exclusion method and the IC50 was determined to be higher in kohlrabi compared to cabbage. Consequently, WST-1 assay was used to assess the effect of these plant extracts on the proliferation of colorectal cancer cell lines: both extracts exhibited a sharp antiproliferative effect in a dose and time dependent manner, even though the cell viability recorded upon kohlrabi treatment was slightly higher. Analysis of cell DNA content by flow cytomtery revealed the ability of both kohlrabi and cabbage extracts to induce cell cycle arrest in HT-29 cells at the G phase and S phase in similar patterns. Furthermore both extracts promoted apoptosis in colorectal cancer cell lines, as revealed by Cell Death ELISA Assay, as well as Annexin/PI staining followed by flow cytometry analysis. The apoptotic pathway seems to involve the pro-apoptotic protein Bax and the anti-apoptotic protein Bcl-2: the expression of these apoptotic regulatory proteins was altered upon cabbage and kohlrabi treatments in a dose-dependent manner, with a slightly higher increase in the Bax/Bcl-2 ratio upon treatment with cabbage extract. As a conclusion, kohlrabi should be considered, like cabbage, among the potent anti-carcinogenic cruciferous vegetables.