Excerpts from the new book The Cancer Chronicles: Unlocking Medicine's Deepest Mystery by George Johnson:
Even more unsettling is a contentious idea called the cancer stem cell theory [see “Stem Cells: The Real Culprits in Cancer?” by Michael F. Clarke and Michael W. Becker; Scientific American, July 2006]. In a developing embryo, stem cells are those with the ability to renew themselves indefinitely—dividing and dividing while remaining in an undifferentiated state. When a certain type of tissue is needed, genes are activated in a specific pattern, and the stem cells give rise to specialized cells with fixed identities. Once the embryo has grown into a creature, adult stem cells play a similar role, standing ready to differentiate and replace cells that have been damaged or have reached the end of their life. Because healthy tissues arise from a small set of these powerful forebears, why couldn't the same be true for tumors?
This would be an unexpected twist on the conventional view in which any cancer cell that has acquired the right combination of mutations is capable of generating a new tumor. Imagine if instead the growth and spread of a cancer is driven by a fraction of special cells, those that have somehow become endowed with an intrinsic quality called “stemness.” Only the cancer stem cells would have the ability to replicate endlessly, metastasize and seed another malignancy. How much easier that might make things for oncologists. Maybe chemotherapies fail because they spare the cancer stem cells. Remove these linchpins, and the malignancy would collapse.
As I struggled to fit this all into the big picture, I was relieved to find researchers who seemed as baffled as I was. However it all pans out, the underlying view of cancer as a Darwinian process—arising like life itself through random variation and selection—would remain unshaken. But as an outsider trying to understand the essence of cancer, I felt daunted by the possibility of even more convolutions.
In the end, all biology comes down to genes talking to genes—within the cell or from cell to cell—in a constant molecular chatter. I had not considered, however, that the genes in human tissues can also exchange information with the genes residing in the microbes that occupy our bodies. Cancer is a disease of information, of mixed-up cellular signaling. Now there is another realm to explore.
Even more unsettling is a contentious idea called the cancer stem cell theory [see “Stem Cells: The Real Culprits in Cancer?” by Michael F. Clarke and Michael W. Becker; Scientific American, July 2006]. In a developing embryo, stem cells are those with the ability to renew themselves indefinitely—dividing and dividing while remaining in an undifferentiated state. When a certain type of tissue is needed, genes are activated in a specific pattern, and the stem cells give rise to specialized cells with fixed identities. Once the embryo has grown into a creature, adult stem cells play a similar role, standing ready to differentiate and replace cells that have been damaged or have reached the end of their life. Because healthy tissues arise from a small set of these powerful forebears, why couldn't the same be true for tumors?
This would be an unexpected twist on the conventional view in which any cancer cell that has acquired the right combination of mutations is capable of generating a new tumor. Imagine if instead the growth and spread of a cancer is driven by a fraction of special cells, those that have somehow become endowed with an intrinsic quality called “stemness.” Only the cancer stem cells would have the ability to replicate endlessly, metastasize and seed another malignancy. How much easier that might make things for oncologists. Maybe chemotherapies fail because they spare the cancer stem cells. Remove these linchpins, and the malignancy would collapse.
As I struggled to fit this all into the big picture, I was relieved to find researchers who seemed as baffled as I was. However it all pans out, the underlying view of cancer as a Darwinian process—arising like life itself through random variation and selection—would remain unshaken. But as an outsider trying to understand the essence of cancer, I felt daunted by the possibility of even more convolutions.
In the end, all biology comes down to genes talking to genes—within the cell or from cell to cell—in a constant molecular chatter. I had not considered, however, that the genes in human tissues can also exchange information with the genes residing in the microbes that occupy our bodies. Cancer is a disease of information, of mixed-up cellular signaling. Now there is another realm to explore.
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