Recent cancer research has shown that several types of haematological and solid malignancies should be regarded as complex tissues with a hierarchical structure like organs.
Transplantation studies show that only a small number of cells in a tumour have the potential to initiate a new malignancy. These so-called cancer stem cells are held responsible for tumour growth, progression of the disease and metastasis.
It is believed that cancer stem cells are more resistant to various forms of treatment than other cells in the tumour. For this reason, any successful therapy should efficiently eliminate these cancer stem cells.
New therapeutic options might be aimed at sensitising the cancer stem cells to therapy. Examples are the induction of differentiation, disturbing the cancer stem cell niche, and interference with signals that protect cancer stem cells from therapy.