Understanding Stem Cells part 43

Cancer: Getting to the root of the problem

Why are some cancers so hard to eliminate, even after many rounds of chemotherapy? The answer may lie in a few abnormal stem cells. Cancerous stem cells were first identified in 1997 when a research group from the University of Toronto  transferred a few blood stem cells from human leukemia patients into mice and watched leukemia develop in the mice. Stem cell-like cells have also recently been found in breast and brain tumors. Like normal stem cells, tumor stem cells exist in very low numbers, but they can replicate and give rise to a multitude of cells. Unlike normal stem cells, however, cancerous stem cells lack the controls that tell them when to stop dividing. Traditional chemotherapy kills  off the majority of the tumor cells, but if any of the cancerous stem cells survive the treatment, the cancer may return. Research into the differences in gene expression between normal and tumor stem cells may lead to treatments where the root of the problem-the cancer stem cell-is targeted.