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Human Heredity 11th Edition by Michael Cummings
Edition 11ISBN: 978-1305251052Human Heredity 11th Edition by Michael Cummings
Edition 11ISBN: 978-1305251052 Exercise 21
Cancer Stem Cells
For several decades, cancer therapy has used chemicals and radiation in an attempt to kill all cells in a tumor as the way to cure this disease. The underlying assumption in this approach is that all cells in a cancer can divide and metastasize, or move to other locations in the body and begin dividing, spreading the cancer. However, work on a number of cancers has led researchers to consider another model, called the cancer stem cell model. According to this model, cancers are organized much like normal adult tissue containing stem cells that can divide to form a limited number of cell types. Remember that stem cells have two properties: (1) self-renewal by division and (2) the ability to differentiate to form specific cell types, which divide only slowly or not at all. In the cancer stem cell model, the pathway of self-renewal has turned into one of continuous division but leaving the other pathway still active.
If this is true, then most cancer cells in a tumor have followed the second pathway and cannot divide fast enough (or at all) to contribute to tumor growth. Instead, attention should be focused on identifying and eliminating the small number of stem cells whose continuous division is driving the growth of the tumor.
Persuasive evidence for the stem cell model has shown that in breast cancer, brain cancer, and colon cancer, only a small number of cells are required to transfer the cancer into mice; most cells in these cancers are nontumorigenic, that is, they cannot transfer the cancer when transplanted into mice. Further work has shown that the stem cells from these and other cancers can be distinguished by biochemical markers that may prove to be the starting point for the development of drugs that target the stem cells.
Although some cancers may follow a stem cell model, this by no means shows that all cancers follow such a model. Other cancers may not contain two types of cells and all cells in these tumors may divide and have the potential to spread the cancer by metastasis. The stem cell model needs further study, but offers a new approach to therapy that may be cancer-specific or patient-specific, changing the basic approach to cancer treatment.
Does the cancer stem cell hypothesis undercut the idea that cancers have a clonal origin, or can the two ideas be reconciled?
For several decades, cancer therapy has used chemicals and radiation in an attempt to kill all cells in a tumor as the way to cure this disease. The underlying assumption in this approach is that all cells in a cancer can divide and metastasize, or move to other locations in the body and begin dividing, spreading the cancer. However, work on a number of cancers has led researchers to consider another model, called the cancer stem cell model. According to this model, cancers are organized much like normal adult tissue containing stem cells that can divide to form a limited number of cell types. Remember that stem cells have two properties: (1) self-renewal by division and (2) the ability to differentiate to form specific cell types, which divide only slowly or not at all. In the cancer stem cell model, the pathway of self-renewal has turned into one of continuous division but leaving the other pathway still active.
If this is true, then most cancer cells in a tumor have followed the second pathway and cannot divide fast enough (or at all) to contribute to tumor growth. Instead, attention should be focused on identifying and eliminating the small number of stem cells whose continuous division is driving the growth of the tumor.
Persuasive evidence for the stem cell model has shown that in breast cancer, brain cancer, and colon cancer, only a small number of cells are required to transfer the cancer into mice; most cells in these cancers are nontumorigenic, that is, they cannot transfer the cancer when transplanted into mice. Further work has shown that the stem cells from these and other cancers can be distinguished by biochemical markers that may prove to be the starting point for the development of drugs that target the stem cells.
Although some cancers may follow a stem cell model, this by no means shows that all cancers follow such a model. Other cancers may not contain two types of cells and all cells in these tumors may divide and have the potential to spread the cancer by metastasis. The stem cell model needs further study, but offers a new approach to therapy that may be cancer-specific or patient-specific, changing the basic approach to cancer treatment.
Does the cancer stem cell hypothesis undercut the idea that cancers have a clonal origin, or can the two ideas be reconciled?
Explanation
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The clonal origin concept of cancer stat...
Human Heredity 11th Edition by Michael Cummings
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