%0 Journal Article
%T Tannic Acid Preferentially Targets Estrogen Receptor-Positive Breast Cancer
%A Brian W. Booth
%A Beau D. Inskeep
%A Hiral Shah
%A Jang Pyo Park
%A Elizabeth J. Hay
%A Karen J. L. Burg
%J International Journal of Breast Cancer
%D 2013
%I Hindawi Publishing Corporation
%R 10.1155/2013/369609
%X Research efforts investigating the potential of natural compounds in the fight against cancer are growing. Tannic acid (TA) belongs to the class of hydrolysable tannins and is found in numerous plants and foods. TA is a potent collagen cross-linking agent; the purpose of this study was to generate TA-cross-linked beads and assess the effects on breast cancer cell growth. Collagen beads were stable at body temperature following crosslinking. Exposure to collagen beads with higher levels of TA inhibited proliferation and induced apoptosis in normal and cancer cells. TA-induced apoptosis involved activation of caspase 3/7 and caspase 9 but not caspase 8. Breast cancer cells expressing the estrogen receptor were more susceptible to the effects of TA. Taken together the results suggest that TA has the potential to become an anti-ER+ breast cancer treatment or preventative agent. 1. Introduction Breast cancer is the leading cause of cancer deaths among women in developed countries [1, 2]. The use of natural dietary compounds to block or delay the onset of cancer is a promising chemoprevention strategy [3¨C7]. The purpose of these chemopreventive agents is to suppress cancer cell proliferation, induce cancer cell differentiation, or initiate apoptosis in cancer cells. Studies have demonstrated that natural phytochemicals containing phenolic compounds possess anticancer properties [8¨C10]. Polyphenols have anticancer functions both in vitro and in vivo [11¨C16]. Tannic acid (TA) belongs to the class of hydrolysable tannins and is comprised of a pentagalloylglucose core esterified at all functional hydroxyl groups with gallic acid molecules [17]. TA is a potential anticancer agent. Apoptotic activity is increased in breast cancer and prostate cancer cells in response to exposure to tannin extracts [18¨C20]. TA functions as a collagen crosslinking agent through both hydrogen bonding and hydrophobic effects. Type I collagen is a common tissue engineering scaffold due to its intrinsically bioactive and biodegradable qualities. Collagen is a naturally derived material and, when uncross-linked, is enzymatically degraded [21]. If used as a biomaterial for tissue engineering purposes the TA-crosslinked collagen Type I would not only serve as an attachment scaffold for cells but also function as an extended release anticancer treatment. As TA-cross-linked collagen is remodeled TA will be released [22]. TA-crosslinked collagen sheets enhance wound healing of the skin in rats [23] and we have previously demonstrated that TA-crosslinked collagen sheets promote adipocyte
%U http://www.hindawi.com/journals/ijbc/2013/369609/