THURSDAY, Feb. 2, 2017 (HealthDay News) — Lifetime intake of soy isoflavone genistein (GEN) improves the response of mammary tumors to tamoxifen (TAM) therapy in a rat model, according to an experimental study published online Feb. 1 in Clinical Cancer Research.
Xiyuan Zhang, Ph.D., from Georgetown University in Washington, D.C., and colleagues compared the effects of GEN intake mimicking Asian (lifetime) or Caucasian (adulthood) intake patterns. Female Sprague-Dawley rats were fed a diet supplemented with 0 (control) or 500 ppm GEN (lifetime GEN) from postnatal day 15. After induction of mammary tumors, a group of control rats was switched to the GEN diet (adult GEN). When the first tumor reached 1.4 cm in diameter, TAM was added to the diet and a subset of control rats started GEN intake (post-diagnosis GEN).
The researchers found that compared with post-diagnosis GEN, lifetime GEN intake reduced de novo resistance to TAM. Compared with the post-diagnosis GEN group, the risk of recurrence was lower in the lifetime and adult GEN groups. Compared with controls, post-diagnosis, and/or adult GEN groups, the lifetime GEN group had downregulation of unfolded protein response (UPR), autophagy-related genes, and genes linked to immunosuppression as well as upregulation of cytotoxic CD8a in tumors.
“GEN intake mimicking Asian consumption patterns improved response of mammary tumors to TAM therapy and this effect was linked to reduced activity of UPR and pro-survival autophagy signaling, and increased anti-tumor immunity,” the authors write.
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