Breast cancer is a cancer with a very high number of morbidity and death in Japan.Of the breast cancer categories, hormone receptor-positive (ER / PR-positive) breast cancer accounts for more than 70% of the total.Hormone therapy that suppresses the action of estrogen is performed in the course of treatment, but it is also a problem that hormone therapy does not work in some patients.Therefore, it is strongly desired to clarify not only the mechanism of breast cancer cell proliferation but also the mechanism by which hormone therapy becomes ineffective.

　As a result of the research conducted by the research group, it was discovered for the first time in the world that leucine is the key to cell proliferation in breast cancer cells.We also found that the functions of two proteins, LLGL2 and SLC7A5, are important for hormone receptor-positive breast cancer cells to take up leucine into the cells.Furthermore, it has been shown that the abundance of these two proteins in cancer cells is one of the causes of hormone therapy ineffectiveness.

　This research result is the first in the world to clarify the mechanism of intracellular uptake of leucine in breast cancer cells, so that only one amino acid is the key to the growth of breast cancer cells, and further, it is for the intracellular uptake of amino acids. This is an epoch-making discovery that revealed that the proteins involved affect the effects on cancer therapeutic drugs.　

Paper information:[Nature] LLGL 2 Rescues Nutrient Stress By Promoting Leu Uptake in ER + Breast Cancer