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Rich66 · 11-15-2009, 04:30 PM

Cancer stem cells targeted to prevent relapse

By: Vivek Sinanan

Posted: 10/22/09

According to a recent paper by Richard Jones of the Hopkins Sidney Kimmel Comprehensive Cancer Center, cancer stem cells (CSCs) can help in the long-term treatment of cancer by preventing relapse.

For at least the past three decades, the existence of CSCs has been known. They are characterized as cells that are biologically similar to normal cells but have the ability to regenerate or self-renew.

According to Jones, these CSCs are only a small fraction of the total cancerous cells but, in theory, they contain all the capacity for the tumor's self-renewal.

CSCs therefore pose a major threat to contemporary cancer treatments. Because of their unique ability, they are more resistant to most standard anti-cancer therapies and treatments than other cancer cells.

Jones' research found that the CSCs tend to copy the defensive mechanisms of other stem cells. Quiescence, in which a cell goes into a dormant state, allows cancer cells to avoid detection by many anti-cancer drugs - efflux pumps, located on cell membranes, can rid the cell of toxins, while detoxifying enzymes break down foreign substances before they can do much harm. All of these mechanisms work together to keep CSCs unharmed by cancer treatments, increasing the likelihood of cancer recurrence.

New research has exposed the potential of CFCs to treat cancer. Scientists from the National Cancer Institute theorized that CSCs and their ability to resist treatment are responsible for relapses in cancer patients, and direct targeting of these stem cells could lead to eventual cures for cancer. Preliminary research has shown that they may be the key to unlocking new cancer treatments if they are directly targeted.

There are several pathways that contribute to the growth and development of normal stem cells during pre- and post-natal development in children. Research has shown that inhibiting these pathways could be effective in the treatment of not one but several types of cancers due to the stem cells' important role in cell maintenance and growth.

A second method of treatment deals with telomeres, the structures that recently won Carol Greider of Hopkins, Elizabeth Blackburn and Jack Szostak the Nobel Prize in Medicine. The survival and aging of a cell is directly linked to the length of its telomeres and the presence of telomerase, the enzyme that synthesizes telomeres.

In an experiment performed at the Dana-Faber Cancer Institute in Boston, researchers mated mice who were predisposed to cancer with mice whose telomerase had been silenced, known as "telomerase knock-out mice." The researchers found that this crossing significantly lowered the development of cancers in these mice.

This is because normal stem cells, and by extension CSCs, require telomerase to lengthen their telomeres. If cells did not have this DNA-lengthening machinery, the DNA would get shorter and shorter with each replication cycle. Genes would eventually be lost from the ends and the cell could potentially die. In normal cells, telomerase prevents rapid DNA loss from occurring, but as a person ages, telomeres, themselves, eventually shorten. In cancer cells, telomerase is over-active, re-growing DNA at lightning speed so that the cancer can continue to replicate uncontrollably. When the telomerase knock-out mice mated with their cancerous counterparts, they produced offspring who were at high risk for cancer but who could not develop their tumors because of the lack of telomerase.

There is one great limit to these new treatments. CSCs make up only a small portion of the cancerous cells in tumors, on average less than one percent. Any impact of treatments on CSCs may be masked by the large bulk of non-CSC cancer cells, and the detection methods available today are incapable of catching them all.

Nevertheless, a CSC-centered approach to
cancer treatments could one day eliminate the possibility of cancer recurrence.

© Copyright 2009 News-Letter

ABCS 2009 Interview with Robert A. Weinberg, Ph.D.

The CTRC-AACR San Antonio Breast Cancer Symposium, Dec. 9-13, 2009, attracts world leaders in cancer research and treatment, including clinical oncologists, industry leaders, basic scientists and translational researchers who are working to improve patient care with the ultimate goal of eradicating breast cancer.
Watch Robert A. Weinberg, Ph.D., a founding member of Whitehead Institute for Biomedical Research and professor of Biology at MIT, talk about "Breast Cancer Stem Cells and the Epithelial-Mesenchymal Transition."

http://www.youtube.com/watch?v=Tmbjj6Nzo4U

11-15-2009, 04:30 PM	#54
Rich66 Senior Member Join Date: Feb 2008 Location: South East Wisconsin Posts: 3,431	Re: Cancer stem cells: The root of all evil? Cancer stem cells targeted to prevent relapse By: Vivek Sinanan Posted: 10/22/09 According to a recent paper by Richard Jones of the Hopkins Sidney Kimmel Comprehensive Cancer Center, cancer stem cells (CSCs) can help in the long-term treatment of cancer by preventing relapse. For at least the past three decades, the existence of CSCs has been known. They are characterized as cells that are biologically similar to normal cells but have the ability to regenerate or self-renew. According to Jones, these CSCs are only a small fraction of the total cancerous cells but, in theory, they contain all the capacity for the tumor's self-renewal. CSCs therefore pose a major threat to contemporary cancer treatments. Because of their unique ability, they are more resistant to most standard anti-cancer therapies and treatments than other cancer cells. Jones' research found that the CSCs tend to copy the defensive mechanisms of other stem cells. Quiescence, in which a cell goes into a dormant state, allows cancer cells to avoid detection by many anti-cancer drugs - efflux pumps, located on cell membranes, can rid the cell of toxins, while detoxifying enzymes break down foreign substances before they can do much harm. All of these mechanisms work together to keep CSCs unharmed by cancer treatments, increasing the likelihood of cancer recurrence. New research has exposed the potential of CFCs to treat cancer. Scientists from the National Cancer Institute theorized that CSCs and their ability to resist treatment are responsible for relapses in cancer patients, and direct targeting of these stem cells could lead to eventual cures for cancer. Preliminary research has shown that they may be the key to unlocking new cancer treatments if they are directly targeted. There are several pathways that contribute to the growth and development of normal stem cells during pre- and post-natal development in children. Research has shown that inhibiting these pathways could be effective in the treatment of not one but several types of cancers due to the stem cells' important role in cell maintenance and growth. A second method of treatment deals with telomeres, the structures that recently won Carol Greider of Hopkins, Elizabeth Blackburn and Jack Szostak the Nobel Prize in Medicine. The survival and aging of a cell is directly linked to the length of its telomeres and the presence of telomerase, the enzyme that synthesizes telomeres. In an experiment performed at the Dana-Faber Cancer Institute in Boston, researchers mated mice who were predisposed to cancer with mice whose telomerase had been silenced, known as "telomerase knock-out mice." The researchers found that this crossing significantly lowered the development of cancers in these mice. This is because normal stem cells, and by extension CSCs, require telomerase to lengthen their telomeres. If cells did not have this DNA-lengthening machinery, the DNA would get shorter and shorter with each replication cycle. Genes would eventually be lost from the ends and the cell could potentially die. In normal cells, telomerase prevents rapid DNA loss from occurring, but as a person ages, telomeres, themselves, eventually shorten. In cancer cells, telomerase is over-active, re-growing DNA at lightning speed so that the cancer can continue to replicate uncontrollably. When the telomerase knock-out mice mated with their cancerous counterparts, they produced offspring who were at high risk for cancer but who could not develop their tumors because of the lack of telomerase. There is one great limit to these new treatments. CSCs make up only a small portion of the cancerous cells in tumors, on average less than one percent. Any impact of treatments on CSCs may be masked by the large bulk of non-CSC cancer cells, and the detection methods available today are incapable of catching them all. Nevertheless, a CSC-centered approach to cancer treatments could one day eliminate the possibility of cancer recurrence. © Copyright 2009 News-Letter ABCS 2009 Interview with Robert A. Weinberg, Ph.D. The CTRC-AACR San Antonio Breast Cancer Symposium, Dec. 9-13, 2009, attracts world leaders in cancer research and treatment, including clinical oncologists, industry leaders, basic scientists and translational researchers who are working to improve patient care with the ultimate goal of eradicating breast cancer. Watch Robert A. Weinberg, Ph.D., a founding member of Whitehead Institute for Biomedical Research and professor of Biology at MIT, talk about "Breast Cancer Stem Cells and the Epithelial-Mesenchymal Transition." http://www.youtube.com/watch?v=Tmbjj6Nzo4U __________________ Mom's treatment history (link)