Protein expression profile and microRNA expression signature in estrogen receptor-positive and -negative breast cancers: report of two cases

BACKGROUND: Identification of the proteins that are associated with estrogen receptor (ER) status is a first step in selecting drugs against hormone-dependent breast cancer. Recently, the proteins associated with ER status were reported using liquid chromatography and tandem mass spectrometry, and microRNA (miRNA) profiling of breast cancer subtype was demonstrated using real-time-PCR. METHODS: We present herein two cases with differential protein expression and miRNA profiling in ER-positive and -negative breast cancer. RESULTS: Proteins associated with fatty acid metabolism were uniquely detected in ER-positive breast cancer. The level of miR-181a expression in ER-positive cancer was higher than that in ER-negative cancer, while the expression of miR-27a, miR-107, and miR-195 was lower in ER-positive compared with ER-negative cancer. CONCLUSION: These cases suggest that fatty acid synthase (FAS) and FAS-related miRNAs are important in ER-positive breast cancer.