Archive for February, 2009

h1

Foetal stem cells cause tumours: Irrelevant and obvious

Friday, 20 February, 2009

Too many people overreacting about a recently released story of a boy developing tumours subsequent to being treated by foetal stem cells, grasping onto the case as evidence for the soundness of their moral viewpoint on embryonic stem cells. A typical example is Josephine Quintavalle of Comment on Reproductive Ethics, who is reported to have said:

The risks of tumour formation in association with embryonic stem cells are widely acknowledged and one reason why there are very serious concerns about the proposed use of such cells in treating spinal cord injury in the US. It would appear from this report that foetal stem cells are similarly unstable. These are not areas of therapy we should be rushing into, whatever the ethical debates surrounding the use of embryo or foetal tissue per se.

Notice she just assumed foetal stem cells are the same as embryonic stem cells?

The first objection to this madness is simply that embryos are not foetuses and foetuses are not embryos. The paper in which this case was presented, in the journal PLoS Medicine, clearly states that the “neural stem cells used were derived from fetuses aborted at week 8-12”, and in fact defines the term fetus as “unborn offspring from the end of the 8th week after conception”.  These are not pluripotent embryonic stem cells, sourced from embryos and able to develop into many tissues. The cells used were ‘merely’ multipotent foetal neural stem cells, sourced from foetuses and only able to develop into neural tissues.

Pro-life groups, who rely on misusing words to equivocate babies with single-celled zygotes, are likely to continue making this mistake. Strangest of all, they should not be opposed to foetal stem cells, as they are sourced from abortions that would have happened anyway. In this sense, they are similar to the embryonic stem cells sourced from otherwise discarded leftover IVF embryos. Better they be used as a cure rather than be binned and incinerated, right? So, this case, while unfortunate, is irrelevant to whether embryonic stem cells should be used.

Secondly, cancer is a risk present with all stem cells (and indeed all cells). After all, stem cells are, by definition, able to proliferate – to grow and mitotically divide – many times. As a consequence, it only takes a single mutation to some aspect of growth regulation for a stem cell to become a tumour. For a normal cell to become cancerous, it must gain the ability to proliferate in addition to a lack of regulation. This has been known for ages, and is reviewed well by Michael Clarke and Michael Becker in Scientific American and, more technically, by Michael Clarke and Margeret Fuller in the journal Cell. All stem cells pose a risk of turning cancerous, regardless of whether they are adult stem cells, embryonic stem cells, or a somatic cell induced into pluripotency.

Embryonic stem cells, foetal stem cells and induced pluripotent stem cells carry such high risk of cancer for the same reason that makes them have such great potential for repairing tissue and curing disease. While adult stem cells can divide many times, only embryonic stem cells (or similar) can divide almost indefinitely.The restricted lifespan of adult stem cells make them less likely to form a tumour, but also means they have less time to repair the tissue. Preferring stem cells for this reason is rather like preferring to hire elderly people to be spies because they likely to retire or die before they go rogue or are turned into being a double agent.

Unfortunately, all current stem cell therapies with the promise of embryonic stem cells also carry the elevated risk of cancer.  So this case of a boy developing tumours from stem cell therapy, while unfortunate, was obviously going to happen to someone.

h1

Homo evolutis – the backlash

Monday, 9 February, 2009

The old speciation argument has raised its head again, with Juan Enriquez (Chairman and CEO of a company called Biotechonomy), giving a talk at TED (Technology Engineering Design) this year. He argued that

humanity is on the verge of becoming a new and utterly unique species, which he dubs Homo Evolutis.

Now, I’ve no issue with him stating speciation may occur, because it might. What I feel is wrong, and what also rubbed a lot of other people the wrong way, is his reasoning for why. He was portrayed as saying:

What makes this species so unique is that it “takes direct and deliberate control over the evolution of the species.”

This sort of talk made George Dvorsky, a fellow futurist, quite uncomfortable. And it made biologist P.Z. Myers quite cranky at futurists.

The point is, Enriquez appears to not quite know what the usual definition of a biological species actually is. In strict biological terms, a species is defined as a “group of actually or potentially interbreeding natural populations, which is reproductively isolated from other such groups”. Having brain-interfaced cybernetic wings or genetic enhancements to your somatic cells won’t make you a new species any more than having a wooden peg leg and drinking rum make you a new species of human (Homo pirata?). To become a new species, you must be able to reproduce with some others, but not with natural humans. This specific desire to control evolution directly, as Juan is said to have discussed, would not do this. At most, it could reprsent some sort of difference in opinion within our one species – between humans who were for enhancement technology, and those who were against. It would be hard enough to even say this represents a new subspecies or even race of humans.

In Enriquez’s defense, after some degree of ‘taking deliberate control over evolution’, it is possible that this could lead to speciation. It could be as simple as restricting breeding through totalitarian reproductive regulations, as in the eugenics of the past, isolating a number of humans from one another until speciation occurred. Alternatively, genetic modifications to the germline could introduce a genetic incompatibility between engineered humans and normal humans (the most obvious example being the addition of an extra chromosome). It’s even possible for some form of simple modification to a structure involved in reproduction (i.e. genitalia) to introduce a physical incompatibility prohibiting easy mating. But merely taking such control over evolution doesn’t imply you actually guide evolution to the degree that speciation occurs.

All that said, I do feel it is difficult for the species concept to be applied rigidly to technologically-assisted reproduction. The definition of species specifies the population must be a natural population, so as to exclude inter-species matings caused by human intervention. But can human intervention be excluded from the definition of a human species? Is it natural for humans to technologically-assist in their own reproduction? These are important questions, because one must consider the advances in genetic technology which come to mind in this sort of dicussion; it is difficult to imagine how any human could not be able to potentially reproduce with any other human given access to sufficient technology. Yet by the same token, such technology may allow Homo sapiens to potentially interbreed with chimpanzees or gorillas (or even farther afield genetically!), so should we extend our species then? How much technological assistance do we allow into our definition of interbreeding?

These same sort of questions come up every time somebody dreams up a new idea for what humans will become, be it Homo superior, Homo artificialis, Homo novus or Homo evolutis.

h1

‘Genetic engineering’ implies an act of engineering

Friday, 6 February, 2009

The term genetic engineering, according to Wiktionary, is the “the deliberate modification of the genetic structure of an organism.” Other definitions, especially those used by biotechnology regulators and lawmakers, often specify that genetic engineering refers only to modifications made by recombinant DNA technology, but I prefer the more broad usage. Genetic engineering is, as the name implies, the engineering of genetic material in living cells.

There are two processes which, I believe,  are mistakenly called genetic engineering: artificial selection (aka selective breeding) and PGD (pre-implantation genetic diagnosis, also known as embryo screening). Artificial selection refers to selective breeding of organisms with the desired traits (and, it is hoped, the desired genes) in order to breed more organisms with the desired traits. Pre-implantation genetic diagnosis is the term for determining the genetic makeup of human embryos before they are implanted for IVF, and usually implies choosing to implant the healthiest or more desirable of embryos.

These are both selective processes, and are often likened to genetic engineering, but often for different reasons. Selective breeding is often considered to be genetic engineering by those defending genetic modification of crops and livestock, as surely the traditional farming methods of the past couldn’t have been wrong (*cough cough*). On the other hand, PGD is often maligned as genetic engineering by those opposed to the idea, as surely genetic engineering of humans is to be vehemently opposed (*cough cough*). In fact, some proponents of human enhancement could even make both leaps at once, claiming that genetic engineering is just like the evolutionary processes of nature (only faster) and therefore that techniques like PGD are likewise just speeding up the natural selection of human embryos that occurs naturally.

But I strongly believe that a selective process is not a form of engineering. In most cases of selection, genomes are not first intentionally modified by human actions. Instead, modifications happen mostly randomly due to mutations and the natural forms of genetic recombination that occur during reproduction. This provides the variety on which breeders, farmers and parents/reproductive specialists can act to select which will be kept and which will be discarded. So, while these selective processes are intentional modifications of the proportions of certain genetic material in a population, they do not entail any intentional modification the genetic material of any individual organism. Selection is no more an act of genetic engineering than going shopping is an act of manufacturing.

Further, I’d be inclined to argue that cloning is also not a form of genetic engineering, as the genetic material is replicated intact rather than modified. Cloning is really just a very effective form of selective breeding, where every piece of genetic material within a particular cell is replicated in the cloned organism. Cloning, therefore, is no more an act of genetic engineering than using copy+paste is an act of writing.

All of this is really just semantics and word games, because it doesn’t really affect the ethical discussions on these issues. Equivocation is avoided, certainly, but appeals to the past, appeals to tradition, slippery slope arguments or arguments rooted in repugnance are also dubious moral arguments. Every new technology will have consequences, some similar to those seen in other technologies and some completely novel. Each technology should be evaluated individually, with comparisons used only when necessary and not stretched beyond reasonable limits.