Breast cancer stem cells
Some indication that stem cells play a role in breast cancer comes from epidemiology data on breast cancer incidence following radiation exposure. Women exposed to radiation in their late adolescence following the Hiroshima and Nagasaki atomic blasts had the high susceptibility of breast cancer 20 to 30 years later compared to womens exposed at other age groups. This suggests that adult mammary stem cells accumulate genetic changes leading to transformation over several years with eventual development of solid tumours. Recently, Al-Hajj and collegues showed that human breast cancer stem cells, identified on the basis of CD44, CD24, Lin expression could form tumours when as few as 100 cells were injected into non obese diabetic/severe combined immunodeficiency disease mice. These cells have some of the key characteristics of stem cells. When 20.000 cells without this phenotype were used, they were unable to form a tumour.