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Treating Cancer By Modifying Cancer Stem Cells

In some future Star Trek century, doctors cure using an intelligent probe. In the 21st Century, medicine, though far from that fictional world, is itself poised for major advances in an emerging area of science called Systems Biology. In turn Systems Biology has major implications for cancer therapy.

At its core, Systems Biology focuses on the integrated interplay among the thousands of molecules within and between cells that underlie health and disease. Central to this molecular dance is the genetic regulatory network that coordinates the activities of some 30,000 genes and their products into the choreography that leads from the fertilized egg to the adult human. Different cell types — liver, kidney, pancreas, nerve — are due to different patterns of activity among these genes. Different combinations of genes make their unique proteins in the different cell types. In the genetic network that coordinates these processes, genes turn one another on and off in complex ways. When this process goes awry, cancer can result.

Strikingly, cancer biologists have recently discovered that many cancers are driven by a very small subset of the cells within the cancer called cancer stem cells. For example, this appears true in brain, prostate, skin, and breast cancer. This affords new hope. Because normal stem cells can change, or differentiate, into a variety of normal cell types, this suggests that cancer stem and progenitor cells can also differentiate into normal cells. And indeed they can. Mutated cancer cells can give rise to normal cell types.

At the University of Calgary, my colleague, Dr. Sui Huang, and I have screened 1,500 FDA approved drugs and found 16 that induce a mild breast cancer cell line to differentiate into adult breast cells and stop proliferating. Caveats are important: Not all cells differentiate, the same 16 drugs may not work on other breast cancer cells, nor may they work in vivo. But here is new hope for a new approach to what can be called "cancer differentiation therapy". Let us all hope.