Background/Aim: Breast cancer (BC) incidence and mortality rates have been increasing due to the lack of appropriate diagnostic tools for early detection. Proteomicsbased studies may provide novel targets for early diagnosis and efficient treatment. The aim of this study was to investigate the global changes occurring in protein profiles in breast cancer tissues to discover potential diagnostic or prognostic biomarkers. Materials and Methods: BC tissues and their corresponding healthy counterparts were collected, subtyped, and subjected to comparative proteomics analyses using two-dimensional gel electrophoresis (2-DE) and twodimensional electrophoresis fluorescence difference gel (DIGE) coupled to matrix-assisted laser desorption/ ionisation-time of flight mass spectrometry (MALDI-TOF/TOF) to explore BC metabolism at the proteome level. Western blot analysis was used to verify changes occurring at the protein levels. Results: Bioinformatics analyses performed with differentially regulated proteins highlighted the changes occurring in triacylglyceride (TAG) metabolism, and directed our attention to TAG metabolism-associated proteins, namely glycerol-3-phosphate dehydrogenase 1 (GPD1) and monoacylglycerol lipase (MAGL). These proteins were downregulated in tumor groups in comparison to controls.Conclusion: GPD1 and MAGL might be promising tissuebased protein biomarkers with a predictive potential for BC.

Berberine is a plant-derived alkaloid possessing antimicrobial activity; unfortunately, its efflux through multidrug resistance pumps reduces its efficacy. Cellular life span of Escherichia coli is generally shorter with prolonged berberine exposure; nevertheless, about 30% of the cells still remain robust following this treatment. To elucidate its mechanism of action and to identify proteins that could be involved in development of antimicrobial resistance, protein profiles of E. coli cells treated with berberine for 4.5 and 8 hours were compared with control cells. A total of 42 proteins were differentially expressed in cells treated with berberine for 8 hours when compared to control cells. In both 4.5 and 8 hours of berberine-treated cells, carbohydrate and peptide uptake regimens remained unchanged, although amino acid maintenance regimen switched from transport to synthesis. Defect in cell division persisted and this condition was confirmed by images obtained from scanning electron microscopy. Universal stress proteins were not involved in stress response. The significant increase in the abundance of elongation factors could suggest the involvement of these proteins in protection by exhibiting chaperone activities. Furthermore, the involvement of the outer membrane protein OmpW could receive special attention as a protein involved in response to antimicrobial agents, since the expression of only this porin protein was upregulated after 8 hours of exposure.

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Tetracycline regulated protein expression in mammalian cells is a powerful tool to predict the physiological function, cellular localization, and stability of a protein. In addition, to predict metabolic networks affected by the expression of wild-type or mutant forms of proteins, researchers generally produce a single mammalian cell clone that can express the protein of interest under tetracycline control and study the changes occurring in overall proteome before and after expression of a protein of interest. One limitation of tetracycline regulated clonal cell creation, however, is that it sometimes creates clones with changed protein levels even without the expression of the protein of interest due to the nonspecific insertion of the gene encoding the protein of interest into the genome or disruption of a metabolic pathway due to insertional silencing or activation. The aim of this study was to demonstrate the limitation of tetracycline regulated gene expression by creating clonal cell lines expressing the wild-type or the mutant forms of Fat mass and obesity-associated protein. Comparative proteome analysis of the protein extracts by two-dimensional gel electrophoresis coupled to MALDI-TOF/TOF revealed the presence of eight proteins subjected to differential regulation even in the absence of induction. The identified proteins were 14-3-3 protein Epsilon, Vimentin, Heterogeneous nuclear ribonucleoprotein K, Tubulin beta-2C chain, Heat shock protein HSP 90-alpha, Heat shock protein HSP 90-beta, Alpha-enolase, TATA-binding protein-associated factor 2N. An ultimate care should be taken to prevent reporting of deceitful proteins generated from studies utilizing tetracycline regulated gene expression systems.