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Altering our proteome: the options
改变我们的蛋白质组：选择 There are four
fundamentally distinct ways to introduce a protein (or an RNA -- for brevity
I will hereafter mention only proteins) into a person's cells and/or
extracellular milieu. 有四种根本不同方法，可以把一种蛋白质（或一种RNA Ð为简单起见我此后只谈蛋白质），引入一个人的细胞和／或细胞外环境中。 The simplest of
the four is transplantation: introduce cells or organs from someone who
already expresses the protein. This is clearly limited to proteins that some
humans express (a relevant limitation, as discussed here, for example), and
generally also carries the side-effect of an immune response which must be
suppressed by lifelong drug administration, impairing the recipient's
resistance to infections and possibly to cancer. 四种中最简单的一种是移植：把已经表达该种蛋白质的某人的细胞或器官引入。这显然被限制于某些人表达的蛋白质（一种相关限制，例如，已在这里here讨论过），一般来说也带有免疫反应的副作用，免疫反应须终身给药来抑制，这削弱了受体对感染、可能还有对癌症的抵抗力。 The second option
is ex vivo genetic modification of cells followed by their introduction into
the recipient. This has many advantages over transplantation -- e.g., genes
expressing non-human proteins can be added, and autologous cells (ones taken
from the patient) can in theory be used and an immune response thereby
avoided. 第二种选择是细胞的体外遗传修饰，然后把它们引入受体。这较之移植有很多好处Ñ例如，表达非人类蛋白质的基因可以添加进去，在理论上可以利用自身的细胞（取自病人自己的细胞），因此可以避免免疫反应。 However, this
approach (generically termed "cell therapy" and including stem cell
therapy) still has limitations: the cells that the engineered cells are
designed to replace must be eliminated. 然而，这种方法（一般称为"细胞疗法"，包括干细胞疗法）仍然有局限性：工程细胞被设计去置换的那些细胞必须被除去。 Sometimes they
are already gone and that is precisely the problem to be rectified,
but sometimes they are present
but failing. They can theoretically be eliminated in conjunction with
introducing new cells, but there are profound technical difficulties in doing
this smoothly enough to maintain tissue function throughout the procedure. 有时它们已经不在，那就正好问题被被矫正（problem to be rectified），但是，有时它们还在但衰竭（present but failing）。在理论上它们可以在引入新细胞的同时被除去，但在整个过程中要足够顺利进行来维持组织功能，这有很大技术难度。 Thus, a lot of
the SENS interventions will require use of the other two approaches --
somatic protein therapy and somatic gene therapy. 这样，SENS的很多干预，就需要利用其他两种方法Ñ体蛋白疗法和体基因疗法。 Getting engineered DNA into specific places in the genome
使工程化DNA进入基因组的特异位置
Several of the strategies
for repairing the seven SENS
targets will almost certainly require, in some tissues, altering the
genomic DNA of cells in the body -- somatic gene therapy. 有几个策略可用于修复SENS七目标（SENS targets），这在某些组织中几乎肯定需要改变身体中细胞基因组DNAÑ体基因疗法。 This is much
harder than taking cells from the person, altering their DNA in the
laboratory and putting them back, because altering the DNA of cells is very
error-prone. If you do the alteration in the lab, you can check whether the
correct alteration happened (and that nothing else happened) and only put
back cells that pass that test. 这比从某人取出细胞、在实验室改变细胞DNA、并把细胞放回，要困难得多，因为改变细胞DNA非常容易出错。如果您在实验室进行了改变，您可以检测是否发生了正确的改变（或者没有其他的什么发生），并仅仅放回检测通过的细胞。 The error-prone
nature of all existing approaches to somatic gene therapy is the main reason
why it is still in its infancy: it's still dangerous. Therefore, one of the
things SENS needs most badly is improvements in our techniques for doing what
we want to do to our genomes in situ and not accidentally doing other things
at the same time. Luckily, several methods are currently under intense
investigation. 体基因疗法的全部已有方法都有容易发生错误的本性，这就是它还处于孩提时代的主要理由：它仍然是危险的。因此，SENS很糟糕地需要的事情之一是：改善我们的技术，使我们能在原位对我们的基因组做我们要做的事情，而同时又不意外地做其他的事情。 For most
applications, all we need to do is get a new gene or genes into our
chromosomes, and it actually doesn't much matter where it goes in -- unless
it disrupts the genes we already have. 对于大部分应用来说，我们要做的全部事情是：使一个新基因或若干基因进入我们的染色体，它进入染色体的哪个部位，实际上没有什么关系Ñ除非它中断了我们已有的基因。 Unfortunately,
that "unless" can't be neglected, because if we're trying to get
the DNA into all (or even most) of our cells then it's going to hit genes in
a fair proportion of them, and in a few of them it's more or less certain to
hit genes involved in cell cycle control -- which means, of course, that it
may promote cancer. 不幸地，这个"除非"不能小瞧了，因为如果我们试图把DNA放进我们的全部（或大部分）细胞中，那么它将袭击细胞的很大一部分基因，在少数细胞中它将或多或少肯定会袭击涉及到细胞周期控制的基因Ñ这当然意味着它可能引起癌症。 The first big
breakthrough in solving this problem was when it was found that one virus,
the adeno-associated virus (AAV), preferentially inserts into a particular
(safe) place on human chromosome 19. 解决这一问题的第一个大突破，是发现一种病毒，即腺病毒相关病毒(AAV)，会有选择地插进人类第19号染色体的一个特殊（安全）位置。 This is good, but
not good enough, because in order to make the virus carry useful genes that
we want to put into our cells we have to take out the stuff that gives it its
site-specificity. But there are various approaches being explored for hybrid
viruses that get the best of both worlds. 这虽好但不够好，因为要使病毒携带我们想放进我们细胞的有用基因，我们不得不拿掉赋予该病毒位点特异性的东西。但是，有各种方法来探索杂种病毒，这样的杂种病毒能使两个方面都好。 AAV doesn't
always insert in this particular spot, however, even when it still has its
site-specific preference. This is largely because it is a linear,
single-stranded DNA virus, and linear single-stranded DNA has a habit of
"invading" double-stranded DNA and sometimes undergoing
recombination with it at random. 然而，AAV即使当它仍然具有它的位点特异偏好时，也不会总是插入这一特殊位置。这主要是因为它是线性的、单线的DNA病毒，而线性的、单线的DNA，有"侵略"双线DNA的习惯，有时进行与双线DNA随机重组。 Much excitement
is therefore currently surrounding a new type of virus -- actually a
bacterial virus, usually called a phage -- which is circular and
double-stranded and which therefore has only a very low tendency to
intercalate into other DNA at random. It does get into DNA, but only when it
expresses a particular enzyme called an integrase. 因此，令人兴奋的是：目前正在围绕着一种新型的病毒Ñ实际上是一种细菌病毒，通常称为噬菌体Ñ它是环状双线的，因此它随机插入其他DNA的倾向性很低。它确实会进入DNA，但只有当它表达一种特殊酶（称为连接酶）时才行。 Better yet, it
only goes into a few specific places in the genome -- and these are not
obviously as safe as the AAV site, because they tend to be in the gaps in the
middle of genes called introns. However, some success has been achieved in
"evolving" these enzymes in the lab so that they prefer different
sites, so there is strong hope that these phages will be safe gene therapy
vectors soon. 尤其可贵的是，它只进入基因组的少数特异位置Ñ这些明显地不如AAV位点那么安全，因为它们倾向于进入称为内含子的基因中间缝隙。然而，已经取得某种成功：在实验室中"进化"了这些酶，使它们喜欢不同的位点，所以这些噬菌体极有希望很快成为安全的基因疗法载体。 Nearly everything that we would like to do with
gene therapy, whether for aging or for any other condition, can probably be
done pretty well by introducing new genes into cells in a safe place. 我们喜欢同基因疗法打交道的几乎每件事，不管是为了衰老，或是为了任何其他情况，都可能做得很好：把新基因引入细胞某一安全位置。 Sometimes we want to stop a gene from expressing
its product, because the product is toxic (such as the mutation that causes
Huntington's disease), but even then we can probably achieve the desired
effect just by putting in a gene, because we can use the amazing phenomenon
of RNA interference to cause the gene's transcript to be destroyed before it
is translated. 有时，我们要停止一种基因表达它的产物，因为这种产物有毒性（例如，引起亨廷顿氏舞蹈病的突变），但即使在这种情况下，我们也有可能仅仅放进一个基因，来达到想要达到的效果，因为我们可以利用RNA干涉的这种令人惊讶现象、在该基因的转录物在被翻译之前就毁坏它。 But there is one case where we probably will really
need somatic gene therapy targeted at a specific place in the genome, and
that's for my preferred anti-cancer therapy, WILT. It's not going to
be good enough to use RNAi against telomerase -- that's just as easy to
"escape" as pharmacological telomerase inhibitors. 但是，有一种情况：我们也许真正需要瞄准基因组一个特异位置的体基因疗法，那就是我所喜爱的抗癌疗法WILT。利用干涉RNA来抗击端粒酶，这还不够好Ñ那仅仅如同"逃避"端粒酶抑制药物一样容易。 What we need to do for WILT is actually delete (or
at least seriously disrupt) the telomerase genes. At present, there are
several approaches to targeted gene disruption (or gene targeting, as it's
usually called) that can be customised to attack anywhere in the genome, but
they're all highly error-prone, disrupting other locations a great deal. 我们为WILT所须做的，实际上是删除（或至少是严重破坏）端粒酶基因。目前，有几种方法可用于打靶的基因破坏（或称基因打靶，实际名称也是这样），它可以定制，用来攻击基因组的任何地方，但它们全都容易出错，在非常多的地方破坏其他位点。 The best bet at the moment is probably that the
phage integrase method can be used by getting a better hold of how its
site-specificity works and therefore being able to design changes to it rather
than using the very weak technique of in vitro evolution -- but this will
need a lot of hard work. 目前大可一赌的是：嗜菌体整合酶方法也许可以利用：较好地拿捏位点特异性使之起作用，而因此能设计改变嗜菌体整合酶，而不是利用体外进化的很不可靠的技术Ñ但这需要做大量艰苦的工作。 Getting proteins into cells to avoid gene therapy
使蛋白质进入细胞以避免基因疗法 Many
components of SENS entail alteration of the genome in many different cell
types. For cells that are constantly renewed from stem cells, this is
relatively easy, because we can extract cells from the individual, do what we
want to those cells in the laboratory, check that we've done exactly what we
wanted to do, and put them back in. SENS的很多组成部分，都是需要在很多不同细胞类型中改变基因组。对于能从干细胞不断更新的细胞，这比较容易，因为我们可以从该个体提取细胞，让那些细胞在实验室中做我们要它们做的事、检测我们要做的事情正确了没有、再把它们放回进去。 This is not easy,
let me stress -- especially hard is doing all this without the cells losing
their "stemness" -- but it'll probably be a lot easier than the
alternative of somatic gene therapy. But tissues that do not have continuous
renewal can't be altered in this way, so at first it might seem that somatic
gene therapy is the only option there. 让我着重指出，这不容易Ñ特别困难的是：做好所有这些事而这些细胞又不会失去它们的"干细胞性"Ñ但它比选择体基因疗法可能会容易得多。但是，不能连续更新的组织，就不能以这种方式来改变，那么首先在这里似乎是：体基因疗法是唯一的选择。 There is in fact
another possibility, however. The basic reason we want to change the genome
of cells is so that those cells will make different proteins than they used
to. For most SENS purposes (and indeed for most biomedical purposes
generally), we want the cell to have proteins that it didn't have before, as
opposed to lacking ones that it used to have. In principle, therefore, this
can be done by introducing the proteins themselves, rather than the genes
encoding them . 然而，事实上另有一种可能性。我们要改变细胞基因组的基本理由是：那些细胞将会制造它们惯常不会制造的不同蛋白质。对于SENS大部分目的来说（并且总的来说对于大部分生物医学目的来说），我们要细胞制造以前没有的蛋白质，相反于缺乏某些蛋白质（缺乏是惯常有）。因此，在原则上，可以这样做：引入蛋白质本身，而不必引入编码蛋白质的基因。 The obvious
problem with such an approach is scale. Most proteins are rather short-lived,
so the cell needs to make them again and again in order to have them around
in the required abundance. Thus, it would be impractical to introduce enough
protein. When Roscoe Brady first sought to explore this approach he was
soundly dismissed for this reason. 使用这种方法的明显问题是度量。大多数蛋白质都很短寿，所以细胞必须一再制造他们，以便使它们大约处在所需的丰度。这样，要引入足够的蛋白质是将是不切实际的。当Roscoe Brady最先寻求探索这种方法时，他因这个理由而被认为是异想天开。 It
turns out, however, that there are plenty of cases where this is not a
showstopper. The class of proteins that Brady was (and still is) interested
in are enzymes which break things down in lysosomes; these enzymes are
congenitally absent in sufferers of lysosomal storage diseases. 然而，原来有大量例子表明，这不是一场精彩表演的中断。Brady过去感兴趣的（现在仍然感兴趣的）蛋白质类型，是溶酶体中的降解酶；在溶酶体储存病患者中，天生缺乏这些酶。 Brady eventually
succeeded in developing methods to make enough enzyme and target it to the
right cells to be able to give many such people a normal life when they would
otherwise certainly have died in childhood. One of the most important SENS
strands, lysosomal enhancement, may well
be able to work this way for many tissues. Brady最终成功地发展了一些方法：制造足够的酶，把酶打靶到适当的细胞，能够给很多这样的人以正常寿命，不然他们在儿童期肯定会死亡。SENS最重要的组成部分之一，是溶酶体增强（lysosomal enhancement），可以很好地用这种方法为很多组织做事。 Another way out
of the protein scale problem is to introduce the genes for the desired
proteins into one tissue and arrange for them to be exported from the cells
that make them and imported by the ones that need them. 解决蛋白质度量问题的另一个方法是，把能得到该蛋白质的基因，引入一个组织，并安排它们从制造该蛋白质的细胞输出，而被需要该蛋白质的组织所输入。 This makes sense
because genes can be introduced safely in stem cells in vitro much more
easily than somatically, as noted above. It is quite easy to modify genes so
that their encoded protein will be secreted, and there are also techniques
for targeting proteins in the circulation to particular organs. 此法行得通，因为基因可以在体外安全地被引入干细胞，比引入身体容易得多，上述已经说过。很容易修饰基因，使它们所编码的蛋白质能被分泌，也有技术使血液循环中的蛋白质打靶到特殊器官。 An especially
important one is the brain, which is protected from the circulation by a
special system that stitches the cells of the blood vessel lining together
much more tightly than elsewhere in the body -- this is called the
blood-brain barrier. Some proteins need to be transported into the brain from
the blood, and we now have a moderate understanding of how this happens and
how we could exploit that system to get our chosen proteins across. 一个特别重要的器官是脑，它被一个特殊的系统保护，免受循环系统所影响，该系统把血管细胞缝合，比身体的其他地方紧密得多地排列一起Ñ这被称为血-脑屛障。某些蛋白质需要从血液运输到脑，现在我们大致了解这是怎样发生的，而我们怎样能利用该系统使我们所选择的蛋白质横跨血-脑屛障。 Finally I should
say a word about germline gene therapy. This means changing the genome of
either a gamete (sperm or egg) or a zygote (a single cell formed either by
fertilisation or by somatic cell nuclear transfer, a.k.a. cloning) so that
people are born with a designed genetic alteration. 最后，我应当提一句生殖系基因疗法。这意味着改变配子（精子或卵子）或合子（由受精或体细胞核移植形成的一个细胞，核移植也称克隆），以至于人是由一种设计了的遗传变化而出生。 Some people think
this would always be far too dangerous to be useful, but others have argued
persuasively that these dangers can be overcome. However, the attractiveness
of this approach is limited by the timescales involved (the fact that aging
only starts being bad for us after we reach 50 or so). 一些人认为，这没用，因为总是太过于危险，但其他人则雄辩地说，这些危险是可以克服的。然而，由于所涉及的时间度量的关系，这种方法的吸引力是有限的（事实上，老化在我们达到50岁左右才开始有害）。 The point here is
that even though somatic gene therapy (putting new genes into the cells of an
adult) is technically much harder than germline gene therapy, 50 years is
such a long time in science that we are virtually certain to be able to do a
lot more for someone in year N+50 by somatic gene therapy than we could do in
year N by germline therapy. So I think germline gene therapy is quite likely
to become an important biomedical procedure in the future, but not in
combating aging. 在这里重要的一点是，虽然体基因疗法（把新基因放进成体细胞中），在技术上比生殖细胞系基因疗法困难得多，但是，50年在科学上是如此长的时间，以至于用体基因疗法实际上我们肯定能够为N＋50岁的人做更多的事，比用生殖系疗法为N岁的人所做的事要多得多。所以，我认为，生殖系基因疗法在将来可能成为一种重要的生物医学方法，但在与老化战斗中不是重要方法。 |
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