Fig. 2.

Cancer Stem Cells (CSC) display enhanced chemoresistance and account for metastases and disease relapse. A tumor typically consists of a minority of CSC, which give rise to more differentiated cancer cells. These differentiated tumor cells represent the majority of cells in the primary tumor, but have a limited self-renewal capacity. Untargeted therapy (e.g. chemotherapy) mainly affects highly proliferating non-CSC. Therapy resistant CSC are spared and can subsequently lead to tumor regrowth and therapy resistance in the initially responding patient (middle panel). Anti-CSC therapy prior to or together with untargeted therapy would hinder the tumors ability to regrow (right panel). Cancer cells with CSC properties can leave the primary tumor via blood or lymphatic vessels and form metastases in distant organs (lower left panel)