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Medicineworld.org: Experimental drug shows promise against cancers

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Experimental drug shows promise against cancers




An experimental drug currently being tested against breast and lung cancer shows promise in fighting the brain cancer glioblastoma and prostate cancer, scientists at UT Southwestern Medical Center have found in two preclinical studies.

The drug's actions, observed in isolated human cells in one trial and in rodents in the other, are particularly encouraging because they attacked not only the bulk of the tumor cells but also the rare cancer stem cells that are thought to beresponsible for most of a cancer's growth, said Dr. Jerry Shay, professor of cell biology and a senior co-author of both papers. The glioblastoma study appears in the recent issue of Clinical Cancer Research The prostate cancer study is available online in the International Journal of Cancer.



Experimental drug shows promise against cancers

In the glioblastoma study, performed in mice, the drug also crossed from the bloodstream into the brain, which is particularly important because a number of drugs are not able to cross the blood-brain barrier.

"Because it attacks a mechanism that's active in most cancers, it might prove to be widely useful, particularly when combined with other therapies," said Dr. Shay.

Dr. Shay and colleagues study telomeres, bits of DNA that help control how a number of times a cell divides. Telomeres are protective "caps" of DNA on the ends of chromosomes, the structures that contain the body's genes. As long as telomeres are longer than a certain minimum length, a cell can keep dividing. But telomeres shorten with each cell division, so a cell stops dividing once the telomeres are whittled down to that minimum.

In cancer cells, however, an enzyme called telomerase keeps rebuilding the telomeres, so the cell never receives the cue to stop dividing. In essence, they become immortal, dividing endlessly.

The drug used in these studies (imetelstat or GRN163L) blocks telomerase. It is already in clinical trials as a potential therapy for breast and lung cancer, as well as for chronic lymphocytic leukemia.

Glioblastomas are the most common cancerous brain tumors in adults, as per the American Cancer Society. They are difficult to treat with drugs because blood vessels in the brain have tightly constructed walls that allow only a few substances to pass through.

The researcher focused on cells called tumor-initiating cells. Some scientists think that tumors contain a small subset of initiating cells or cancer stem cells that are able to initiate and drive tumors and that are often resistant to radiation treatment and chemotherapy.

In the glioblastoma study, Dr. Shay and colleagues observed that imetelstat blocked the action of telomerase in isolated tumor-initiating cells as well as the bulk of the tumor cells, eventually killing the cells. Combining imetelstat with radiation and a standard chemotherapy drug made imetelstat even more effective. When the scientists implanted human tumor-initiating cells into rodents, they observed that imetelstat was able to enter brain tissue and inhibit telomerase activity.

In the prostate cancer study, the scientists isolated tumor-initiating cells from human prostate cancer cells. The cells showed significant telomerase activity. Imetelstat blocked the enzyme's activity, and telomeres shortened greatly.


Posted by: Janet    Source




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An experimental drug currently being tested against breast and lung cancer shows promise in fighting the brain cancer glioblastoma and prostate cancer, scientists at UT Southwestern Medical Center have found in two preclinical studies. The drug's actions, observed in isolated human cells in one trial and in rodents in the other, are particularly encouraging because they attacked not only the bulk of the tumor cells but also the rare cancer stem cells that are thought to beresponsible for most of a cancer's growth, said Dr. Jerry Shay, professor of cell biology and a senior co-author of both papers. The glioblastoma study appears in the recent issue of Clinical Cancer Research The prostate cancer study is available online in the International Journal of Cancer.

Medicineworld.org: Experimental drug shows promise against cancers

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