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.

The Role of Stem Cells in Basic Research

Stem cells offer opportunities for scientific advances that  go  far  beyond  regenerative  medicine.  They offer  a window  for  addressing  many  of biology’s most  fundamental questions.  Watching embryonic stem cells give rise to specialized cells is like peeking  into  the earliest  development of the  many  tissues and organs of the human body. Stem cell research may  help  clarify  the  role  genes  play  in  human  development and how genetic mutations affect nor- mal processes. They can be used to study how infec- tious  agents invade and attack human cells, to investigate  the genetic  and  environmental  factors that are involved in cancer and other diseases, and to decipher what happens during aging.

Stem  cells  may  also  revolutionize  tradi- tional   chemical   medicine.   Because embryonic stem  cells  can  continue  to divide for long periods  of time and pro- duce a variety  of cell types, they could provide  a valuable   source  of  human  cells for testing drugs  or measuring  the effects of toxins  on  normal tissues  with- out risking the health of a single human  volunteer.  In  the  future,  thousands  of compounds could be quickly  tested on a wide assortment of cell types derived from stem cells, making drug discovery more efficient and cost effective.
Using  nuclear  transfer to produce stem cells could be particularly useful for testing drugs for disorders that are of genetic origin. For example, it is difficult to   study   the   progression  of   Alzheimer’s  and Parkinson’s diseases  in the brains of live patients— but by using  the cells of an Alzheimer’s patient to create stem cell lines with nuclear transfer, scientists could  trace  the development of the  disease  in a culture  dish  and  test  drugs  that  regenerate   lost nerve cells with no danger to the patient.

Stem  cells  may  also  help  scientists  calculate  the effects of toxic substances  in drugs, food, and the environment.