Wednesday, March 29, 2017

The (bad) luck of the draw; more evidence

A while back, Vogelstein and Tomasetti (V-T) published a paper in Science in which it was argued that most cancers cannot be attributed to known environmental factors, but instead were due simply to the errors in DNA replication that occur throughout life when cells divide.  See our earlier 2-part series on this.

Essentially the argument is that knowledge of the approximate number of at-risk cell divisions per unit of age could account for the age-related pattern of increase in cancers of different organs, if one ignored some obviously environmental causes like smoking.  Cigarette smoke is a mutagen and if cancer is a mutagenic disease, as it certainly largely is, then that will account for the dose-related pattern of lung and oral cancers.

This got enraged responses from environmental epidemiologists whose careers are vested in the idea that if people would avoid carcinogens they'd reduce their cancer risk.  Of course, this is partly just the environmental epidemiologists' natural reaction to their ox being gored--threats to their grant largesse and so on.  But it is also true that environmental factors of various kinds, in addition to smoking, have been associated with cancer; some dietary components, viruses, sunlight, even diagnostic x-rays if done early and often enough, and other factors.

Most associated risks from agents like these are small, compared to smoking, but not zero and an at least legitimate objection to V-T's paper might be that the suggestion that environmental pollution, dietary excess, and so on don't matter when it comes to cancer is wrong.  I think V-T are saying no such thing.  Clearly some environmental exposures are mutagens and it would be a really hard-core reactionary to deny that mutations are unrelated to cancer.  Other external or lifestyle agents are mitogens; they stimulate cell division, and it would be silly not to think they could have a role in cancer.  If and when they do, it is not by causing mutations per se.  Instead mitogenic exposures in themselves just stimulate cell division, which is dangerous if the cell is already transformed into a cancer cell.  But it is also a way to increase cancer by just what V-T stress: the natural occurrence of mutations when cells divide.

There are a few who argue that cancer is due to transposable elements moving around and/or inserting into the genome where they can cause cells to misbehave, or other perhaps unknown factors such as of tissue organization, which can lead cells to 'misbehave', rather than mutations.

These alternatives are, currently, a rather minor cause of cancer.  In response to their critics, V-T have just published a new multi-national analysis that they suggest supports their theory.  They attempted to correct for the number of at-risk cells and so on, and found a convincing pattern that supports the intrinsic-mutation viewpoint.  They did this to rebut their critics.

This is at least in part an unnecessary food-fight.  When cells divide, DNA replication errors occur.  This seems well-documented (indeed, Vogelstein did some work years ago that showed evidence for somatic mutation--that is, DNA changes that are not inherited--and genomes of cancer cells compared to normal cells of the same individual.  Indeed, for decades this has been known in various levels of detail.  Of course, showing that this is causal rather than coincidental is a separate problem, because the fact of mutations occurring during cell division doesn't necessarily mean that the mutations are causal. However, for several cancers the repeated involvement of specific genes, and the demonstration of mutations in the same gene or genes in many different individuals, or of the same effect in experimental mice and so on, is persuasive evidence that mutational change is important in cancer.

The specifics of that importance are in a sense somewhat separate from the assertion that environmental epidemiologists are complaining about.  Unfortunately, to a great extent this is a silly debate. In essence, besides professional pride and careerism, the debate should not be about whether mutations are involved in cancer causation but whether specific environmental sources of mutation are identifiable and individually strong enough, as x-rays and tobacco smoke are, to be identified and avoided.  Smoking targets particular cells in the oral cavity and lungs.  But exposures that are more generic, but individually rare or not associated with a specific item like smoking, and can't be avoided, might raise the rate of somatic mutation generally.  Just having a body temperature may be one such factor, for example.

I would say that we are inevitably exposed to chemicals and so on that will potentially damage cells, mutation being one such effect.  V-T are substantially correct, from what the data look like, in saying that (in our words) namable, specific, and avoidable environmental mutations are not the major systematic, organ-targeting cause of cancer.  Vague and/or generic exposure to mutagens will lead to mutations more or less randomly among our cells (maybe, depending on the agent, differently depending on how deep in our bodies the cells are relative to the outside world or other means of exposure).  The more at-risk cells, the longer they're at risk, and so on, the greater the chance that some cell will experience a transforming set of changes.

Most of us probably inherit mutations in some of these genes from conception, and have to await other events to occur (whether these are mutational or of another nature as mentioned above).  The age patterns of cancers seem very convincingly to show that.  The real key factor here is the degree to which specific, identifiable, avoidable mutational agents can be identified.  It seems silly or, perhaps as likely, mere professional jealousy, to resist that idea.

These statements apply even if cancers are not all, or not entirely, due to mutational effects.  And, remember, not all of the mutations required to transform a cell need be of somatic origin.  Since cancer is mostly, and obviously, a multi-factor disease genetically (not a single mutation as a rule), we should not have our hackles raised if we find what seems obvious, that mutations are part of cell division, part of life.

There are curious things about cancer, such as our large body size but delayed onset ages relative to the occurrence of cancer in smaller, and younger animals like mice.  And different animals of different lifespans and body sizes, even different rodents, have different lifetime cancer risks (some may be the result of details of their inbreeding history or of inbreeding itself).  Mouse cancer rates increase with age and hence the number of at-risk cell divisions, but the overall risk at very young ages despite many fewer cell divisions (yet similar genome sizes) shows that even the spontaneous mutation idea of V-T has problems.  After all, elephants are huge and live very long lives; why don't they get cancer much earlier?

Overall, if if correct, V-T's view should not give too much comfort to our 'Precision' genomic medicine sloganeers, another aspect of budget protection, because the bad luck mutations are generally somatic, not germline, and hence not susceptible to Big Data epidemiology, genetic or otherwise, that depends on germ-line variation as the predictor.

Related to this are the numerous reports of changes in life expectancy among various segments of society and how they are changing based on behaviors, most recently, for example, the opiod epidemic among whites in depressed areas of the US.  Such environmental changes are not predictable specifically, not even in principle, and can't be built into genome-based Big Data, or the budget-promoting promises coming out of NIH about such 'precision'.  Even estimated lifetime cancer risks associated with mutations in clear-cut risk-affecting genes like BRCA1 mutations and breast cancer, vary greatly from population to population and study to study.  The V-T debate, and their obviously valid point, regardless of the details, is only part of the lifetime cancer risk story.

Just after posting this, I learned of a new story on this 'controversy' in The Atlantic.  It is really a silly debate, as noted in my original version.  It tacitly makes many different assumptions about whether this or that tinkering with our lifestyles will add to or reduce the risk of cancer and hence support the anti-V-T lobby.  If we're going to get into the nitty-gritty and typically very minor details about, for example, whether the statistical colon-cancer-protective effect of aspirin shows that V-T were wrong, then this really does smell of academic territory defense.

Why do I say that?  Because if we go down that road, we'll have to say that statins are cancer-causing, and so is exercise, and kidney transplants and who knows what else.  They cause cancer by allowing people to live longer, and accumulate more mutational damage to their cells.  And the supposedly serious opioid epidemic among Trump supporters actually is protective, because those people are dying earlier and not getting cancer!

The main point is that mutations are clearly involved in carcinogenesis, cell division life-history is clearly involved in carcinogenesis, environmental mutagens are clearly involved in carcinogenesis, and inherited mutations are clearly contributory to the additional effects of life-history events.  The silly extremism to which the objectors to V-T would take us would be to say that, obviously, if we avoided any interaction whatsoever with our environment, we'd never get cancer.  Of course, we'd all be so demented and immobilized with diverse organ-system failures that we wouldn't realize our good fortune in not getting cancer.

The story and much of the discussion on all sides is also rather naive even about the nature of cancer (and how many or of which mutations etc it takes to get cancer); but that's for another post sometime.

I'll add another new bit to my post, that I hadn't thought of when I wrote the original.  We have many ways to estimate mutation rates, in nature and in the laboratory.  They include parent-offspring comparison in genomewide sequencing samples, and there have been sperm-to-sperm comparisons.  I'm sure there are many other sets of data (see Michael Lynch in Trends in Genetics 2010 Aug; 26(8): 345–352.  These give a consistent picture and one can say, if one wants to, that the inherent mutation rate is due to identifiable environmental factors, but given the breadth of the data that's not much different than saying that mutations are 'in the air'.  There are even sex-specific differences.

The numerous mutation detection and repair mechanisms, built into genomes, adds to the idea that mutations are part of life, for example that they are not related to modern human lifestyles.  Of course, evolution depends on mutation, so it cannot and never has been reduced to zero--a species that couldn't change doesn't last.  Mutations occur in plants and animals and prokaryotes, in all environments and I believe, generally at rather similar species-specific rates.

If you want to argue that every mutation has an external (environmental) cause rather than an internal molecular one, that is merely saying there's no randomness in life or imperfection in molecular processes.  That is as much a philosophical as an empirical assertion (as perhaps any quantum physicist can tell you!).  The key, as  asserted in the post here, is that for the environmentalists' claim to make sense, to be a mutational cause in the meaningful sense, the force or factor must be systematic and identifiable and tissue-specific, and it must be shown how it gets to the internal tissue in question and not to other tissues on the way in, etc.

Given how difficult it has been to chase down most environmental carcinogenic factors, to which exposure is more than very rare, and that the search has been going on for a very long time, and only a few have been found that are, in themselves, clearly causal (ultraviolet radiation, Human Papilloma Virus, ionizing radiation, the ones mentioned in the post), whatever is left over must be very weak, non tissue-specific, rare, and the like.  Even radiation-induced lung cancer in uranium minors has been challenging to prove (for example, because miners also largely were smokers).

It is not much of a stretch to simply say that even if, in principle, all mutations in our body's lifetime were due to external exposures, and the relevant mutagens could be identified and shown in some convincing way to be specifically carcinogenic in specific tissues, in practice if not ultra-reality, then the aggregate exposures to such mutations are unavoidable and epistemically random with respect to tissue and gene.  That I would say is the essence of the V-T finding.

Quibbling about that aspect of carcinogenesis is for those who have already determined how many angels dance on the head of a pin.

Friday, March 24, 2017

Paid To Prey (PTP) journals

In the bad old days if you as a scientist had something worth saying, a journal would (after vetting through a mainly fair confidential review system) publish it.  If you had good things to say, whether or not you had grants, your ideas were heard, and you could make a career on the basis of the depth of your thought, your careful results, and so on.

If you needed funds to do your research, such as to travel or run a laboratory, well, you needed a grant to do your work.  This was the system we all knew.  You had to have funding, but you couldn't just pay your way through to publishing.  Also, if you were junior, start-up funds were typically made available if you needed them, to give you a leg up and a chance to get your career going.

Publishing has always had costs, of course, but the journals survived by library and personal subscriptions, often based on professional society memberships, where the fees were modest, especially for the most junior members.

Now what we have is a large pay-to-play (PTP) industry.  Pay-to-play journals are almost synonymous with corruption.  The mass of nearly-criminal ones prey on the career fears of desperate students, post-docs, and faculty (especially junior faculty, perhaps).  Even the honest PTP journals, of which there are many, essentially prey on investigators, and taxpayers, but the horde of dishonorable ones are no better than highwaymen, robbing the most vulnerable.  A story in the NY Times exposes some of the schemes and scams of the dishonorable PTPers.  But it doesn't go nearly far enough.

How cruel is this rat race?  Where does the PTP money come from?
We have every moral as well as fiscal right to ask where the PTP subscriptions are coming from.  Are low-paid, struggling post-docs, students, junior or even more senior faculty members using their own personal funds to keep in the publication score-counting game?  How much taxpayer money goes, even via legitimate grants, to these open-source publishers rather than to the research costs for which these grants were intended.  In the past, you might have had to pay for color figures, or for reprints, and these costs did come generally from grant funds, but they were not very expensive.  And of course grants often pay for faculty salaries (a major corruption of the system that nobody seems able to fix and on which too many depend to criticize).

The idea of open-source journals sounded good, and not like a private-profiteering scam.  But too many have turned out to be the latter, chickens laying golden eggs even for the better journals, when there is profit to be made. The original, or at least more publicly proclaimed open-source idea was that even if you couldn't afford a subscription or didn't have access to a university library--especially, for example, if you were in a country with a paucity of science resources--you would have access to the world's top science anyway.  But even if the best of the open-source organizations are non-profit, non-predatory PTP operations, and how would we know?, we are clearly preying on the fears of those desperate for careers in heavily oversubscribed, heavily Malthusian overpopulated science industries.

There is no secret about that, but too many depend on the growth model for there to be an easy fix, except the painful one of budget cuts.  The system is overloaded and overworked and that suggests that even if everyone were doing his/her best, sloppy or even corrupt work would make it through the minimal PTP quality control sieve.  And that makes it easy to see why many may be paying with personal funds or submitting sloppy (or worse) work--and too much of it, too fast.

There isn't any obvious solution in an overheated hyper-competitive system.  We do have the web, however, and one might suggest shutting down the PTP industry, or at least somehow closing its predatory members, and using the web to publicize new findings.  Perhaps some of the open review sources, like ArXiv, can deal with some of the peer reviewing issues to maintain a quality standard.

Of course, Deans and Chairs would have to actually do the work of evaluating the quality of their faculty members' works (beyond 'impact factors', grant totals, paper counts, and so on) to reward quality of thought rather than any quantity-based measures.  That would require the administrators to actually think, know their fields, and take the time to do their jobs.  Perhaps that's too much to ask of a system now sometimes proudly proclaiming it's on the 'business model'.

But what we're seeing is what we deserve because we've let it happen.

Thursday, March 16, 2017

Higher resolution discrimination: The GOP wants to allow employers to require genetic testing

This morning, Ed Yong published an article that takes on issues that we at the The Mermaid's Tale care very deeply about.
Link to article
The consequences for important medical research are not going to be pretty.

And I can't help but be angry about this for threatening to take away the fun of genetics too. If we can't have some control over our genetic testing, we can't do it for fun, for education, for finding out more about ourselves, for the awe of it, for innerspace exploration in the technology age. They're taking that away from us by eroding GINA.

I have lots of other thoughts... like about how this fits in so nicely with (not all of) the right's racist/eugenics inclinations.

And juxtapose this view from the political right where there is full-on acceptance of actually-more-than-genetics-can-even-deliver against their anti-science politics and policy...

It's like science is totally fine for Republicans as long as Mother Nature is a dictator.

If it's more complicated than that, then deny it, defund it, bulldoze it. The reality is, genetics is largely probabilistic; it is not a dictatorship. It's just so hard to convince people that it isn't. The ideological drive to justify behavioral differences and socioeconomic inequality with Nature above all is just too strong. If it's Nature, then we don't have to do the hard work of addressing the problems because Nature is Nature is Nature. This is really old thinking that really new knowledge (both through lots of science and lots of lived experience and lots of humanities and lots of art) has overturned but has not managed to catch on all that well. Along with new knowledge we get increasing understanding of genetics so these ancient beliefs can just be spouted by politicians using new-fangled science jargon.

This is really hard to write about today as all the stories about the proposed (and highly probable) budget cuts to science and the arts are blasting through my newsfeeds. It's overwhelming me today. I'm feeling hopeless and angry on behalf of science, art, knowledge, medicine, humanity, humans, children, teenagers, grown-ups, geezers. It's too much today.

But, back to Ed's article, I do need to put this here because it mentions that I have taught with 23andMe and longtime readers of the MT might know about that:

I don't teach with 23andMe anymore. I was doing it for as long as my university would pay for the kits. It was totally voluntary and students had to read Misha Angrist's book and endure long discussions and pass a quiz before deciding whether to go through with the testing. It was so powerful for teaching evolution, genetics, anthropology, etc... and we critiqued the hell out of it. My university said I needed to pay for the kits through course fees from now on. Before any of these threats to GINA, I decided not to do that and to stop using 23andMe. Now, even if my university reconsidered and funded the kits, I still wouldn't take it up again as a teaching tool.