Background:
The effect of cruciferous vegetable intake on breast cancer survival is controversial at present. Glucosinolates are
the naturally occurring constituents found across the cruciferous vegetables. Isothiocyanates are produced from the hydrolysis of
glucosinolates and this reaction is catalysed by the plant-derived enzyme myrosinase. The main isothiocyanates (ITCs) from cruciferous
vegetables are sulforaphane, benzyl ITC, and phenethyl ITC, which had been intensively investigated over the last decade for their antibreast cancer effects.
Objective:
The aim of this article is to systematically review the evidence from all types of studies, which examined the protective effect
of cruciferous vegetables and/or their isothiocyanate constituents on breast cancer.
Methods:
A systematic review was conducted in Pubmed, EMBASE, and the Cochrane Library from inception to 27 April 2020. Peerreviewed studies of all types (in vitro studies, animal studies, and human studies) were selected.
Results:
The systematic literature search identified 16 human studies, 4 animal studies, and 65 in vitro studies. The effect of cruciferous
vegetables and/or their ITCs intake on breast cancer survival was found to be controversial and varied greatly across human studies. Most
of these trials were observational studies conducted in specific regions, mainly in the US and China. Substantial evidence from in vitro and
animal studies was obtained, which strongly supported the protective effect of sulforaphane and other ITCs against breast cancer. Evidence
from in vitro studies showed sulforaphane and other ITCs reduced cancer cell viability and proliferation via multiple mechanisms and
pathways. Isothiocyanates inhibited cell cycle, angiogenesis and epithelial mesenchymal transition, as well as induced apoptosis and altered
the expression of phase II carcinogen detoxifying enzymes. These are the essential pathways which promote the growth and metastasis of
breast cancer. Noticeably, benzyl ITC showed a significant inhibitory effect on breast cancer stem cells, a new dimension of chemoresistance in breast cancer treatment. Sulforaphane and other ITCs displayed anti-breast cancer effects at variable range of concentrations
and benzyl isothiocyanate appeared to have a relatively smallest inhibitory concentration IC50. The mechanisms underlying the cancer
protective effect of sulforaphane and other ITCs have also been highlighted in this article.
Conclusion:
Current preclinical evidence strongly supports the role of sulforaphane and other ITCs as potential therapeutic agents for
breast cancer, either as adjunct therapy or combined therapy with current anti-breast cancer drugs, with sulforaphane appeared to display
the greatest potential.
An examination of obesity and breast cancer survival in post-menopausal women
