NR4A1 and breast cancer: Studies were performed with and without inhibition of the enzyme, glutaminase (GLS), the first step in glutamine catabolism that generates glutamate, and key target for therapy directed to glutamine-metabolizing cancers.<h4>Methods</h4>The study used xenograft mouse models for two breast cancer cell lines, HCC1806, a highly glutaminolytic triple-negative cell line, and MCF-7, a hormone receptor positive line with only low levels of glutaminolysis.