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【bio-news】细胞死亡的新形式
Scientists have discovered a novel form of cell death in which cells crawl inside other cells to die. The process, dubbed entosis, may be a method of suppressing tumors, the researchers say, but others aren't so sure.
For more than 25 years, scientists examining cultures of human cancer cells have occasionally spotted cells tucked within other cells. But the phenomenon remained largely unexplored until a team led by cell biologist Michael Overholtzer of Harvard Medical School in Boston recently saw the same thing while working with a line of normal breast cells. As in breast tissue, these cultured cells usually grow on a membrane or matrix. When they became detached, however, some cells appeared to be enveloped by other cells. Intrigued, the researchers looked closer.
Overholtzer's team found that up to 70% of the detached cells died once engulfed by another detached cell. However, up to 9% divided while enveloped and up to 18% were eventually released unharmed. Blocking the mechanisms involved in other methods of cell death including apoptosis and phagocytosis did not disrupt the process, confirming that entosis operates in a different way.
Further experiments revealed that cadherins, proteins that keep cells joined to each other, are required for entosis. The researchers are still working out the details, but they speculate in the 30 November issue of Cell that entosis occurs due to an imbalance in adhesion forces between two cells when they dislodge from the matrix. This could lead to one cell pushing into the other until it is engulfed, akin to pressing your fist into a balloon.
However entosis occurs, it appears to be widespread. The team found evidence of the process in several other cell types, including breast, ovarian, umbilical cord, and kidney cancer cells. Overholtzer says tumor suppression may be one function of entosis. When a chemical that inhibits entosis was applied to a line of breast cancer cells, colony formation--an indicator of tumor growth in vitro--increased 10-fold.
Conversely, cancer cells could be using entosis as a survival tool. It may be "a way for a tumor cell to escape recognition by chemotherapeutic drugs or the immune system" by hiding out inside another cell, says Maureen Murphy, a molecular biologist at Fox Chase Cancer Center in Philadelphia, Pennsylvania. That may explain why not all cells die during entosis.
Craig Thompson, a cancer biologist at the University of Pennsylvania, is more skeptical. The fact that some cells survive entosis, he says, suggests that it is not a very effective process for suppressing tumors and raises concern that it may be a phenomenon that primarily occurs in the lab rather than in the body.
http://sciencenow.sciencemag.org/cgi/content/full/2007/1129/4 New Form of Cell Death Discovered
细胞死亡的新形式
Scientists have discovered a novel form of cell death in which cells crawl inside other cells to die. The process, dubbed entosis, may be a method of suppressing tumors, the researchers say, but others aren't so sure.
科学家们发现了一种新的细胞死亡方式，即一个细胞慢慢进入另一个细胞然后死亡。研究者们说这个称为“entosis”的过程可能成为抑制肿瘤的方法，但尚不完全确定。
For more than 25 years, scientists examining cultures of human cancer cells have occasionally spotted cells tucked within other cells. But the phenomenon remained largely unexplored until a team led by cell biologist Michael Overholtzer of Harvard Medical School in Boston recently saw the same thing while working with a line of normal breast cells. As in breast tissue, these cultured cells usually grow on a membrane or matrix. When they became detached, however, some cells appeared to be enveloped by other cells. Intrigued, the researchers looked closer.
25年前，科学家们在进行人肿瘤细胞培养时就偶然发现过有斑点细胞卷入其它细胞的现象。但是无人深入研究这一现象，直到最近波士顿哈佛医学院细胞生物学家Michael Overholtzer领导的研究小组在研究正常乳腺细胞时发现了相同情形。类似于在乳腺组织中，这些培养的细胞常常生长在薄膜或基质上。将两者分离后，一些细胞被包裹进另一些细胞。研究者们正在进一步研究。
Overholtzer's team found that up to 70% of the detached cells died once engulfed by another detached cell. However, up to 9% divided while enveloped and up to 18% were eventually released unharmed. Blocking the mechanisms involved in other methods of cell death including apoptosis and phagocytosis did not disrupt the process, confirming that entosis operates in a different way.
Overholtzer的小组发现一旦被卷入到别的细胞，70%的分离细胞死亡。然而，还有9%进行了分裂，18%最后完好无损地释放出来。阻断可诱导凋亡和吞噬等细胞死亡其他方式的机制，但均并不会中断entosis，证实了entosis具有独特的作用机制。
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作者:admin@医学,生命科学 2011-02-19 05:12
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