Is the cancer stem cell population "a player" in multi-drug resistance?

The concept of cancer as a stem cell disease has the potential to dramatically change our view of the problem of its treatment. A major cellular target of cancer therapy will be directed against neoplastic stem cells. Current investigations are attempting to combine molecular targeted therapy concepts with the concept of the cancer stem cells. Molecular targeted therapy against cancer stem cells can be divided into 6 categories that correspond to following types of targets, presented in this review: surface molecules; ABC multidrug resistance proteins; specific oncoproteins; normal and neoplastic stem cell pathways; survival factors, present in cancer stem cells, such as NF-kappaB pathway, PI3K, downstream signaling molecules and related signal-transduction pathways and oxidative stress.