A comparison of the effects of soya isoflavonoids and fish oil on cell proliferation, apoptosis and the expression of oestrogen receptors α and β in the mammary gland and colon of the rat

Abstract

Isoflavonoids and fish oil may be protective against colorectal cancer, but the evidence in relation to breast cancer risk is ambiguous. In the present study, we have investigated the impact of soya-derived isoflavonoids andn-3 fatty acids from fish oil, both individually and in combination, on apoptosis, cell proliferation and oestrogen receptor (ER) expression in the colon and mammary gland of the rat. Female rats were fed diets high inn-3 fatty acids (80 g/kg diet) or soya protein (765 mg/kg diet isoflavones) for 2 weeks, and then killed before the removal of the colon and mammary glands. Cell proliferation and apoptosis were quantified morphologically in whole crypts and terminal end buds. The expressions ofERαandERβwere measured in colon tissue scrapes and the mammary gland. Fish oil significantly increased apoptosis and decreased mitosis in both tissues, an effect associated with a decrease in the expressions ofERα andERβ. Soya had no effect on apoptosis in either tissue, but reduced mitosis in the colon (P < 0·001) while increasing it in the mammary gland (P = 0·001). The changes in proliferation were associated with contrasting changes in theERexpression such that fish oil significantly decreased bothERβandERα, while soya increasedERαand decreasedERβ. The results may provide a novel mechanism by whichn-3 fatty acids could reduce cancer risk, but the interpretation of the results in relation to soya consumption and breast cancer risk requires further investigation.

Diet-Based Strategies for Cancer Chemoprevention: The Role of Combination Regimens Using Dietary Bioactive Components

“…Therefore, this combinatorial interaction could be beneficial in allowing women at increased risk of breast cancer to ingest soy with flaxseed, thereby obtaining the health benefits of soy without the added risk. Along this line of findings, a complementary role of fish oil was identified in another study when it was combined with soy protein and found to offset the overexpression of ER-α, thus diminishing the potential negative tumorigenic effects of soy protein (Kramer et al 2009). …”

Effect of Dietary Intake of Isoflavones on the Estrogen and Progesterone Receptor Status of Breast Cancer

“…A randomized controlled trial reported that increased isoflavone intake can affect estrogen metabolism by altering the steroid hormone concentrations and menstrual cycle length in a manner consistent with this hypothesis (26). Moreover, a recent study reported that soya increased the expression of α-ER in the mammary gland of the rat (27). Another study investigated the effects of genistein and daidzein on ER α-mRNA and protein expression within the endometrium of premenopausal women and found that their antiestrogenic properties resulted in more expression of α-ER (28).…”

Dietary intake of isoflavones and breast cancer risk by estrogen and progesterone receptor status

“…Soy isoflavones can act as an estrogenic agonist or antagonist depending on the estrogen concentration [11] and reduce levels of ovarian steroids in normal women [12]. Some experimental data even suggest that soy constituents can be estrogenic and potentially risk enhancing [27], and that soy increased the expression of alpha estrogen receptors in the rat mammary gland [28].…”