Colon cancer stem cells: Controversies and perspectives

Figure 1 Schematic presentation of two possible ways of colon adeocarcinoma formation. A: “Bottom-up” theory: intestinal stem cells (ISCs, arrow) at the base of the crypt, within the stem cell zone, are the cell of origin of neoplasia as a consequence of anomalous differentiation; B: “Top-down” theory: a progenitor or differentiated cell is the first transformed cell that can acquire stem cells (arrow) behavior before inducing cancer.