GSE122271
RNA sequencing of PND55 mammary glands of mice fed 20% ISP, 1% ISP, 20% casein or Teklad 2018
Epidemiologic studies demonstrate that women from cultures that consume high levels of dietary soy have reduced breast cancer rates compared to women from cultures where soy consumption is typically much lower. The types of soy products consumed can also differ with Asian cultures consuming primarily minimally refined soy products while Western cultures often consume more highly refined soy products such as isolated soy protein (ISP). Our previous work showed that lifetime exposure to a diet containing 20% ISP promoted mammary tumor development in MTB-IGFIR transgenic mice. In this study, lifetime exposure to lower levels of ISP were evaluated (5% ISP and 1% ISP) to determine whether more moderate levels of ISP could protect against mammary tumorigenesis.  A standard rodent diet, Teklad 2018 was also included in this study and Teklad 2018 contains a less refined form of soy, namely soybean meal. MTB-IGFIR mice fed ISP diets, independent of the concentration, displayed increased mammary tumor incidence and reduced tumor latency compared to MTB-IGFIR mice fed a 20% casein diet. Unexpectedly, MTB-IGFIR mice fed Teklad 2018 were completely protected against mammary tumor development. Although RNA sequencing of mammary tumors from ISP or casein fed mice did not identified gene expression patterns associated with the ISP diets, the ISP diets consistently promoted the expression of contractile related proteins in pubertal mammary glands. Therefore, lifetime exposure to ISP may alter gene expression in pubertal mammary glands rendering them more susceptible to transformation. Based on these findings women may want to avoid highly refined soy products such as ISP and switch to less refined forms of dietary soy until additional studies can be performed. Overall design: Mice were exposed to 20% isolated soy protein (ISP), 1% ISP, 20% casein or Teklad 2018 throughout embryonic and postnatal development (lifetime exposure). 4th mammary glands were collected, lymph node removed, and RNA extracted prior to sending for RNA sequencing.