DIFFERENTIAL INFLUENCE OF HYPOXIA ON GENE EXPRESSION OF TUMORAL AND NON TUMORAL MAMMARY CELLS

Abstract

Cancer metastasis is the result of a series of deregulated biological phenomena, including alterations of cell-cell and cell-matrix interactions and of other microenvironmental conditions such as the oxygen tissue supply. Hypoxia is a well-known driver of aggressive cancer phenotypes, indeed tumors with poor prognosis have higher proportions of anoxic and hypoxic areas1. The consequences of tumour hypoxia can be local or even systemic towards distant organs, and it can evoke diversified responses: whereas low oxygen concentration in tissue environments. (pO2 <7 mmHg) exerts anti-proliferative effects and promotes differentiation, apoptosis and/or necrosis on normal cells, the tumoral cells react to hypoxic stress with adaptive processes that confer them an aggressive phenotype2. Indeed, the hypoxic microenvironment in tumors contributes to alter energy metabolism, cell growth and responsiveness to therapy. The aim of present study was the identification, by a proteomic strategy, of the effects exerted by hypoxic conditions on the 8701-BC breast cancer cells compared with HB2 immortalized normal mammary epithelial cells. For this purpose, the two cell cultures, were grown at low oxygen content (pO2=2%) in parallel with normoxic cells (pO2=20%). Hypoxic and normoxic cells at confluence were then properly collected, lysed and subjected to 2D-IPG based proteomic analysis3. Proteins identified by several methods4 were then clusterized by using the gene ontology database DAVID. The results showed that the hypoxic condition exerts different effects on the proteomic profile of the two cell lines. In particular, a general down-regulation of the proteome complement was observed for the HB2 cells and especially for the classes of the negative regulators of apoptosis and of the proteins involved in membrane vesiculation. Conversely, the proteomic profile of the 8701-BC cells was not altered significantly by the hypoxia, except for the highly modulated protein class of the cytoskeleton. These data suggest that hypoxia may depress cell behaviour of non-tumoral cells, while is ineffective on neoplastic cells, basically adapted to anaerobic metabolism, or even promotes cell motility which contributes in directing the tumour cells to acquire a more aggressive phenotype.