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【bio-news】新的细胞死亡机制被发现
By Steve Mitchell
ScienceNOW Daily News
29 November 2007
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. 这个新发现的细胞死亡机制不是凋亡（apoptosis），而是endosis 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.
科学家们已经发现了一种新的细胞死亡形式，某种细胞被包裹入另一种细胞，然后死亡。这个过程被定义为entosis，有希望成为抑制肿瘤的新方法，但是研究者也承认结果还不确定。
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.
科学家们研究培养的人类细胞已经有不止25年的历史了，在此过程中 ，有时会不小心将某些细胞卷入其他细胞破坏自身。这种现象一直没有合理的解释，直到哈佛大学医学院的生物学家Michael Overholtzer带领的团队近期在研究一些正常的乳腺细胞的时候注意到了同样的现象。在乳腺组织，这些培养的细胞一般生长在膜上或是基质上。当它们分离的时候，有一些细胞就会被另一些细胞包裹。研究人员们都被这个现象吸引了。
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.
研究人员发现，70%被其他的细胞卷入的细胞都死亡了。但是，也有9%被卷入的细胞能够分裂，有18%最后可以安然无恙。阻断我们熟知的其他的细胞死亡机制比如凋亡或是吞噬方式，都不会改变这个结局，这进一步证实了entosis是一种新的细胞死亡方式。
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作者:admin@医学,生命科学 2011-04-26 05:14
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