FIGURE 1.

Cellular plasticity and tumor cell aggressiveness. (A) The original model of cellular plasticity proposed that the EMT program was associated with the appearance of CSC properties and it was supposed that these mesenchymal-like cells were responsible for driving cancer cell growth, chemotherapy resistance, metastasis and relapse. (B) The new models of cellular plasticity propose that stemness properties would be of different functional significance depending on the cell context and the particular cancer progression stage. In these models, hybrid cells (E/M1-4) expressing both epithelial (E) and Mesenchymal (M) markers develop cellular plasticity with different stemness properties, allowing tumor cells to adapt to the diverse circumstances of the tumor microenvironment, and to take special advantages of the functional properties conferred by the establishment of these programs. The aggressiveness would be manifested by a wide spectrum of distinct hybrid cells, requiring particular properties according to the hurdles present during tumourigenesis.