Breast cancer is the second leading cause of cancer death in women. This study suggests a chemopreventive strategy. Retinoic acid can reduce expression of the inhibitor of apoptosis protein, survivin (induced three-fold by retinoic acid receptor (RARa)-selective agonist Am580 in T-47D breast cancer cells). In MCF-7 mammary carcinoma cells, growth inhibition by RA entails an early cell cycle arrest followed by induction of apoptosis. Expression array analyses revealed that RA induces the expression of several genes involved in cell cycle regulation, including the p53-controlled antiproliferative gene, B-cell translocation gene, member 2 (Btg2).

We measured histone H2A directly from breast cancer cells (MALDI). Protein extractions were obtained from RA treated MCF-7 breast cancer cells with organic solvent (ProteoSolve) and high pressure (Barocycler, Pressure BioSciences, West Bridgewater, MA), trypsinized, and the following proteins with LCMS (Hitachi NanoFrontier nLC, Dallas, TX): gi|938234 SOX-9 [Homo sapiens] Mass: 6448; gi|110591141 Chain A, Solution Structure Of The First Homeobox Domain Of At- Binding Transcription Factor 1 (Atbf1) Mass: 7974; gi|5454114 tissue factor pathway inhibitor isoform a precursor [Homo sapiens] Mass: 34992; gi|83715968 sarcoma antigen NY-SAR-79 [Homo sapiens] Mass: 124077; gi|119587536 ferredoxin 1 [Homo sapiens] Mass: 28101; and gi|3851261 immunoglobulin M heavy chain [Homo sapiens] Mass:10193.

High pressure extraction increased protein yield and helped to identify proteins not previously seen and revealed marked differences between retinoic acid treated and non-treated cells. The identification of additional proteins will allow characterization of the metabolic cascade induced by RA and may lead to new therapeutic strategies in breast cancer.