Proteomic analysis of human mammospheres treated with lysine and estradiol

Despite anti-estrogen therapy, almost 30% of estrogen receptor positive (ER+) breast cancer patients relapse. Amino acids (AAs) in the tumor microenvironment may affect the metastatic capacity of breast cancer cells. Essential AAs (EAAs) cannot be produced by human cells and might therefore be targetable as therapeutics. By using liquid chromatography-mass spectrometry we identified the ribophorin-2 (RPN2) and the splicing factor U2AF 35 kDa subunit (U2AF1) as the most significantly affected proteins after lysine and estradiol (E2) exposure in T47D and MCF-7 mammospheres, respectively. RPN2 and U2AF1 were identified as prognostic factors for patient survival in breast cancer databases.