Abstract: Estrogen, hormones and growth factors in serum play important roles in the carcinogenesis and development of breast cancer. The study of the effects of the above factors on protein components and their contents in breast cancer cells is necessary for understanding the molecular mechanisms. In this study, isobaric tags for relative and absolute quantification (iTRAQ) labeling coupled with two-dimensional liquid chromatography-tandem mass spectrometry (2D-LC-MS/MS) was employed to compare the differential protein expressions in MCF7 cells upon 17β-oestradiol (E2) stimulation or serum deprivation (SD) versus in normal conditions. A total of 576 proteins with the confidential level of ≥95% were identified, 26 proteins among the 576 proteins were found to be differentially expressed after E2 stimulation or serum deprivation, and among them 10 proteins were up-regulated and 16 proteins were down-regulated by more than two folds. Interestingly, both E2 and serum significantly altered the level of proteins involved in protein synthesis. This demonstrated iTRAQ coupled LC-MS/MS is an efficient methodology in comparative proteomics.

Key words: breast cancer cells , estrogen, serum deprivation, two-dimensional liquid chromatography-tandem mass spectrometry (2D-LC-MS/MS), isobaric tags for relative and absolute quantification (iTRAQ)