ABSTRACT
In contrast, the cancer stem cell model suggests that only rare cancer stem cells have the intrinsic ability to proliferate extensively to form new tumors. Stem cells are multipotent with high proliferative potential and with concomitant properties of self-renewal and differentiation into multilineage cells. The multilineage differentiation of cancer stem cells may contribute to the heterogeneity of certain tumors, including breast cancer. The parallels between normal stem cells and cancer stem cells suggest that some cancer stem cells arise from mutated normal stem cells, and are responsible for the proliferative capacity of cancers. Stem cell niches regulate stem cell proliferation and cell fate decisions, and they also play a protective role by shielding stem cells from environmental insults. The stem cell niche provides this microenvironment for cancer stem cells, and the combination of lethal seeds in lethal soil is likely to lead to the most aggressive forms of breast cancer, with the most fatal course.
