癌症难以治愈的内在原因,或为进化上需要

最近两名科学家发表文章,认为癌症的本质并不是与我们作对,这一疾病事实上是进化上最终的一步,它是用来避免有瑕疵的基因传递到下一代,这可能揭示了癌症难以治愈的内在原因。

当然,这仅仅是一个假设,并没有经过试验的验证,而且他们也不认为任何人死于癌症是顺理成章的事情。事实上正好相反,研究者们认为这一理念能够帮助我们更好地理解这一疾病,从而设计更加有效的治疗手段,比如免疫疗法等等。

就这一观点,我们可以讨论一下:为什么我们的身体想要杀死自己?这篇文章背后的依据是,每个人的体内都有一系列的安全守卫机制,这些机制能够避免我们的DNA发生突变后传递给新的细胞。

其中最重要的一个机制就是细胞凋亡,或者说程序性细胞死亡。如果细胞的DNA已经损伤到难以修复的地步,将会最终导致细胞凋亡,凋亡后的细胞能够快速地被免疫系统识别,从而通过吞噬的方式解决这一异物。

但最新的这一理论认为,当细胞凋亡等安全守卫机制不再一如往常般有效的时候,癌症将会出现,作为最终的守卫机制发挥功能。癌症的目的即在突变的细胞传递下去之前将其杀死,以摧毁整个生命为代价。

具有分裂能力的细胞需要受到至少4个安全检查机制的调控。

细胞凋亡在大多数情况下都能够发现细胞损伤,但有时候也会错过一些。当这种情况发生时,将会导致细胞不受控制地增长,甚至导致癌症。

听上去好像有些不靠谱,但是作者认为这跟衰老的机制是一样的,毕竟地球承受不了无休止的生命。

“癌症像是一个终极的进化机制,就像DNA修复以及凋亡一样,能够保护地球上的生命不至于灭绝”。

也就是说,根治癌症的方法是不存在的。我们对待这种疾病的方法应该着重于延长患者的寿命以及生活质量。

 

The final checkpoint. Cancer as an adaptive evolutionary mechanism

Rumena Petkova & Stoyan Chakarov

The mechanisms for identification of DNA damage and repair usually manage DNA damage very efficiently. If damaged cells manage to bypass the checkpoints where the integrity of the genome is assessed and the decisions whether to proceed with the cell cycle are made, they may evade the imperative to stop dividing and to die. As a result, cancer may develop. Warding off the potential sequence-altering effects of DNA damage during the life of the individual or the existence span of the species is controlled by a set of larger checkpoints acting on a progressively increasing scale, from systematic removal of damaged cells from the proliferative pool by means of repair of DNA damage/programmed cell death through ageing to, finally, cancer. They serve different purposes and act at different levels of the life cycle, safeguarding the integrity of the genetic backup of the individual, the genetic diversity of the population, and, finally, the survival of the species and of life on Earth. In the light of the theory that cancer is the final checkpoint or the nature’s manner to prevent complex organisms from living forever at the expense of genetic stagnation, the eventual failure of modern anti-cancer treatments is only to be expected. Nevertheless, the medicine of today and the near future has enough potential to slow down the progression to terminal cancer so that the life expectancy and the quality of life of cancer-affected individuals may be comparable to those of healthy aged individuals.

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