And when it's weakened, those mutated cells are not recognized by your immune system.

免疫系统功能一旦降低，就识别不出发生突变的细胞了。

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Maybe it got mutated and its making the wrong kinds of proteins; cancer cells often do that.

它可能已经变异,产生了错误的蛋白,癌细胞往往就是这样

耶鲁公开课 - 生物医学工程探索课程节选

Even when a tumor is all but eliminated by Taxol, a few cells with mutated microtubules that are invulnerable to the drug can remain, growing into more deadly tumors.

FORBES: Taxol's Next Stand

Eventually, huge numbers of these mutated proteins build up, form insoluble masses within cells, which kill them.

BBC: vCJD and BSE - the link

However, when it is mutated it is unable to do this, leaving cells at risk of becoming potentially cancerous.

BBC: How gene causes breast cancer