OBJECTIVES/SPECIFIC AIMS: These studies seek to evaluate hormonal regulation of luminal breast cancer lipid metabolism and to identify targetable progesterone-mediated changes in lipid biology that contribute to therapeutic resistance in breast cancer. METHODS/STUDY POPULATION: Established and patient-derived luminal breast cancer cell lines, which express ER and PR, were used for this study. RNA transcript and protein expression levels were evaluated by qRT-PCR and immunoblot, respectively. Broad scale lipidomics of progesterone-treated cells was conducted via ultra-high pressure liquid chromatography-mass spectrometry (UHPLC-MS) through the UCD Skaggs School of Pharmacy Mass Spectrometry Core. RESULTS/ANTICIPATED RESULTS: Data mining of previously published microarray data of CK5+ and CK5− syngeneic cancer sublines revealed that CK5+ cells have increased expression of lipid processing genes, including LPL and PPARG. As progestin treatment induces a subpopulation of cells to turn on CK5 expression in luminal breast cancers, UHPLC-MS-based lipidomics analysis will expose whether modulation of the lipid landscape occurs in all cells with progesterone treatment, or whether this phenomenon is heightened specifically in CK5+ cells. I also expect that ER+ breast cancers with progestin induced-altered lipid content, such as lipid droplet formation, will evade therapy-induced death. DISCUSSION/SIGNIFICANCE OF IMPACT: There are numerous approved and developmental therapeutics targeting lipid biology. By determining if progestins alter lipid metabolic genes specifically in CK5+ CSCs, which are endocrine resistant, strategies may be devised to target these resistant cells using combination therapy in conjunction with existing therapies to prevent tumor recurrence.