Isolated Soy Protein Promotes Mammary Tumor Development Induced by the Type I Insulin-like Growth Factor Receptor in Transgenic Mice.
Level 5 - mechanism / opinion, no new human data
Preclinical animal model study
PubMed 32692262 · doi:10.1080/01635581.2020.1795210
What was done
Transgenic mice with mammary-specific expression of the type I insulin-like growth factor receptor (MTB-IGFIR) were fed diets with lifetime exposure to 20%, 5%, or 1% isolated soy protein (ISP) versus a 20% casein control diet. Additional groups were fed Teklad 2018 (containing whole soybean meal) or Teklad 2018ISP (soybean meal replaced with ISP) to evaluate the impact of refined versus less refined soy on mammary tumorigenesis.
What was found
MTB-IGFIR mice fed ISP diets exhibited increased mammary tumor incidence and reduced tumor latency compared to mice fed 20% casein (exact numerical incidences, latencies, and p-values not reported in the abstract). Mice fed the whole soybean meal diet were completely protected against mammary tumor development. In mice fed the Teklad 2018ISP diet, 2 of 10 mice developed mammary tumors.
Why it matters
This study suggests that the form of dietary soy matters in preclinical models, with isolated soy protein promoting and whole soybean meal protecting against IGF-IR-driven mammary tumor development.
Limits
This is an animal model study with mammary-specific transgenic overexpression of IGF-IR, which may not reflect human physiology or breast cancer risk. Total sample size across most groups is omitted from the abstract (only the n = 10 for the Teklad 2018ISP group is given). Quantitative rates, survival/latency times, and statistical significance values are not provided in the abstract for the primary comparisons.
Cited by
- supports In animal models, isolated and hydrolyzed soy protein produced significantly different effects, particularly regarding cancer outcomes, compared to whole soy foods.