Breast cancer is the most common form of
cancer diagnosed in women worldwide and the second leading cause of
cancer-related deaths in the USA. Despite the development of newer diagnostic methods, selective as well as targeted
chemotherapies and their combinations, surgery, hormonal
therapy,
radiotherapy,
breast cancer recurrence,
metastasis and drug resistance are still the major problems for
breast cancer. Emerging evidence suggest the existence of cancer stem cells (CSCs), a population of cells with the capacity to self-renew, differentiate and be capable of initiating and sustaining
tumor growth. In addition, CSCs are believed to be responsible for
cancer recurrence, anticancer drug resistance, and
metastasis. Hence, compounds targeting breast CSCs may be better therapeutic agents for treating
breast cancer and control recurrence and
metastasis. Naturally occurring compounds, mainly
phytochemicals have gained immense attention in recent times because of their wide safety profile, ability to target heterogeneous populations of
cancer cells as well as CSCs, and their key signaling pathways. Therefore, in the present review article, we summarize our current understanding of breast CSCs and their signaling pathways, and the
phytochemicals that affect these cells including
curcumin,
resveratrol,
tea polyphenols (epigallocatechin-3-gallate, epigallocatechin),
sulforaphane,
genistein,
indole-3-carbinol, 3, 3'-di-indolylmethane,
vitamin E,
retinoic acid,
quercetin,
parthenolide,
triptolide,
6-shogaol,
pterostilbene,
isoliquiritigenin,
celastrol, and
koenimbin. These
phytochemicals may serve as novel therapeutic agents for
breast cancer treatment and future leads for drug development.