COMPARATIVE PROTEOMIC PROFILING OF NORMAL AND BREAST CANCER CELLS UNDER HYPOXIC CONDITIONS

Abstract

influences emanating from the tissue microenvironment, such as cell-cell and cell-matrix interactions and other local pathophysiologic conditions as hypoxia. However the hypoxic effect may be different according to the cell conditions. For example, the low concentration of tissue oxygen (pO2 <7 mmHg) may exert anti-proliferative effects on normal cells and may induce differentiation or apoptosis and necrosis. On the other contrary, tumour cells likely react to hypoxic stress with an adaptive process through modification of gene expression that may confer an aggressive phenotype to cells, promoting their local and distant spread [1]. In general it is believed that hypoxic microenvironments in tumors contribute to cancer progression, which in turn may alter metabolism, growth, and therapeutic responsiveness. The aim of present research was to study in a broad proteomic context the effects exerted by hypoxic conditions on the 8701-BC breast cancer cells compared with HB2 immortalized normal mammary epithelial cells. These cell lines have been extensively characterized, also for their proteomic profiles [2, 3]. For this purpose, cells were grown at low oxygen content (pO2 2%) and examined in parallel with normoxic cells (pO2 20%). To determine global protein pattern changes during hypoxia, we used the Immobilin/2DIPG electrophoresis system and we gave them identity by several methods, as previously reported [3]. Using the silver stain method, we were able to resolve about 1000 proteins from both normoxic and hypoxic samples. Present results have shown that the hypoxic condition exerted different effects on the two cell lines. Normal mammary epithelial cells displayed a generalized down regulation of the protein pool detectable on the proteomic map, including the significant class of apoptosis inhibitor, with the exception of the glycolytic enzymes that showed increased expression level. Conversely, the protein complement detectable in the 8701-BC breast cancer cells was not altered significantly by the hypoxia, except for the class of cytoskeletal proteins that showed highly modulated expression patterns. These results suggest that while the non-tumoral cells are very responsive to the hypoxia, the neoplastic cells, isolated from an advanced malignant breast cancer, were already basically adapted to anaerobic metabolism, but still responsive for other cellular activities, like cell motility which may contribute in directing the neoplastic cells towards a still more aggressive phenotype.