Rodent Models Assessing Mammary Tumor Prevention by Soy or Soy Isoflavones

Abstract

While epidemiological studies performed in Asian countries generally show that high levels of dietary soy are associated with reduced breast cancer risk, studies in Western countries have typically failed to show this correlation. In an attempt to model the preventative actions of soy on mammary tumor development, rodent models have been employed. Thirty-four studies were identified that evaluated the impact of soy products or purified soy isoflavones on mammary tumor initiation (studies evaluating established mammary tumors or mammary tumor cell lines were not included) and these studies were separated into mammary tumors induced by chemical carcinogens or transgenic expression of oncogenes based on the timing of soy administration. Regardless of when soy-based diets or purified isoflavones were administered, no consistent protective effects were observed in either carcinogen-induced or oncogene-induced mammary tumors. While some studies demonstrated that soy or purified isoflavones could reduce mammary tumor incidence, other studies showed either no effect or tumor promoting effects of soy products or isoflavones. Most importantly, only five studies found a decrease in mammary tumor incidence and six studies observed a decrease in tumor multiplicity, two relevant measures of the tumor preventative effects of soy or isoflavones. The variable outcomes of the studies examined were not completely surprising given that few studies employed the same experimental design. Future studies should be carefully designed to more accurately emulate soy consumption observed in Asian cultures including lifetime exposure to less refined soy products and potentially the incorporation of multigenerational feeding studies.

Dietary effect of mead acid on DMBA‑induced breast cancer in female Sprague‑Dawley rats

“…It is well known that there are a number of risk factors for breast cancer (e.g., an advanced age or viral infection) (21). The dietary quality and habits are also one of the factors affecting breast cancer (e.g., the consumption of red meat, ultra-processed sugary products, sulforaphane, vitamin D, calcium, soy isoflavone) (18,(22)(23)(24)(25). Recently, the influence of the quality of daily foods on breast cancer has attracted considerable attention.…”

“…A large-scale cohort study carried out in France revealed that the intake of ultra-processed sugary products was associated with the incidence of breast cancers (23). By contrast, sulforaphane extracted from broccoli, vitamin D, calcium and soy isoflavone have been reported to function as possible cancer-preventive agents (18,24,25). Therefore, it seems that the constituents of foods consumed on a daily basis play a role in breast carcinogenesis.…”

Physiologically Active Molecules and Functional Properties of Soybeans in Human Health—A Current Perspective

“…Furthermore, isoflavone is produced by an oncogene and functions as an inhibitor of tyrosine protein kinase [ 45 ]. Among the soybean isoflavones, genistein inhibits the growth of cells that cause breast, colon, lung, prostate, and skin cancers in vitro ( Figure 5 ) [ 36 , 46 ]. In addition, genistein inhibits the formation of boils by preventing vasculogenesis, thus blocking the supply of oxygen or nutrients [ 47 ].…”

Isolated Soy Protein Promotes Mammary Tumor Development Induced by the Type I Insulin-like Growth Factor Receptor in Transgenic Mice

“…Since it is difficult to control for the contributions of other lifestyle factors to breast cancer risk in humans and human prevention trials would take decades to complete, several studies have utilized rodent models to investigate the impact of soy on mammary tumor development. Animal models using chemical carcinogens or oncogenic transgenes have showed mixed results (reviewed in (17)) with some studies showing that soy decreases tumor latency or increases tumor incidence while other studies demonstrate that soy protects against mammary tumor development or had no effect.…”