Identification of mechanism(s) leading tohyperdiploidy in progenitor tumor cells derivedfrom MCF7 breast cancer cells

Stem cells are a minor population of mostly restingcells defined by their long life, high clonogenicity,self-replicating potential, plasticity, and drugresistance (Finn, 2008). Cells with these propertieshave been identified in various normal andcancerous human tissues (Wicha, 2006), as well asin several long-term tumor cell lines (Setoguchi,2004). We have some preliminary data indicatingthat cells isolated from MCF7 line divide slowlyand form spheres, both features of progenitorstumor cells, when grown in ultralow adherentplates and in absence of serum. Furthermore, thesefeatures were associated to two distinct populationscharacterized by different content in terms ofnumber of chromosomes. We hypothesize thatthere are mechanisms that lead to the formation ofhyperdiploid cells starting from progenitors cellswith a near-diploid karyotype. We are investigatingwhich genes might be involved in this process andif symmetric or asymmetric division depending byaltered mitotic genes expression. Moreover wesupposed that cell-cell fusion could be amechanism that lead to hyperdiploidy. Tounderstand whether changes in ploidy occurring inprogenitor cells might be the result of cell fusion,we transfected cells from MCF7-sphere with twovectors encoding H2B-GFP (green) and H2B-RFPruby(red) to stain chromosomes. Cell were coculturedand fusion occurrence was evaluated by fluorescence microscopy detecting nuclei with bothtypes of fluorescence, indicating fusion as possiblemechanism to generate hyperdiploid cells.