Peptide YY and vitamin E inhibit hormone-sensitive and -insensitive breast cancer cells

We have shown that peptide YY, an endogenous gut hormone, and vitamin E succinate (VES) inhibit pancreatic cancer cell growth in vitro. We hypothesized that PYY and VES would inhibit breast cancer cell viability regardless of the hormone receptor status. Human breast ZR-75 ductal carcinoma (estrogen receptor negative) and MCF-7 adenocarcinoma (estrogen receptor positive) cells were cultured and exposed to VES (10 pg/ml), PYY (500 pmol), or both agents together. MTT assay was performed at 24, 48, and 72 h to evaluate cell viability. At every time interval, PYY and VES significantly inhibited cell growth compared to control. The effects of PYY were similar in magnitude to those of VES. Combining the agents resulted in a significant additive inhibition of growth with the greatest effect seen at 72 h. We have shown that PYY and vitamin E inhibit in vitro growth of breast cancer cells with variable hormone receptor status. When used in combination, the agents have a significant increase in effect. Further studies are ongoing to define the mechanism of action of these agents and to translate the experiments to an in vivo model.