"A small-cell lung cancer genome with complex signatures of tobacco exposure" is the title of a study from the Wellcome Trust Sanger Institute in Cambridge, published online by nature on 16 December 2009.
It sounds like Sherlock Holmes finding the fingerprints of the murderer.
In a nutshell, here is the fact:
The researchers decoded the set of genes present in a bone marrow metastasis of a small-cell lung cancer of ONE PATIENT and found 22,910 somatic substitutions that bind and mutate the DNA. To say it with their words (whatever they mean): "Using massively parallel sequencing technology, we sequenced a small-cell lung cancer cell line, NCI-H209, to explore the mutational burden associated with tobacco smoking". One of the researcher, Peter Campbell, stated: "On the basis of average estimates, we can say that one mutation is fixed in the genome for every 15 cigarettes smoked".
Lots of web sites and world’s media went to seventh heaven and sprang up to exploit that study with headings like: 15 Cigarettes Equal One DNA Mutation – How does cigarette smoke induce cancer? – Cigarettes mutate smokers’ genes – and more of the same.
Why do I say that they "exploited" that study?
THE SMOKING HISTORY OF THE PATIENT WAS NOT AVAILABLE
Here is why:
– The agencies of mass communications do not bother to investigate.
The journalists, as usual, did not bother to read the full article: a press release is all they need to throw a piece of news that grabs the average man’s attention.
The work, from the scientific point of view, is probably interesting for researchers in the fields of DNA, cell lines, molecular biology, and the like. From a practical point of view it does not seem to be of much value: Steve Elledge, from Harvard Medical School in Boston, Massachusetts, said that such an approach won’t be practical until scientists have hundreds of sequences readily available. He stated: "It’s still very expensive, and I think all these efforts should be coupled with an equal amount of effort on studying gene function" (see: Medical News Today).
– From my point of view, this study is better than nothing, but close to it. Here is why:
1. Many malignant tumors show differences in molecular abnormalities, growth factor receptors, hormonal influences, differences in DNA repair capacity and cytochrome P450. The latter has numerous body functions at molecular level and, besides the fact that it can vary from person to person, its activity is increased, decreased, or inactivated by various substances, including fruit juices. These factors alone make it highly improbable that the genome sequencing may help the treatment of cancers.
2. There is a multitude of studies in which the authors reach conclusions rejected by statisticians and epidemiologists because of the small number of cases investigated. What about this one where they examined the lesion of just ONE patient?!…
3. The researchers admitted that the smoking history of the patient was not available (!!!). By Jupiter, how can that be possible? Where in the world they operate on a patient without doing beforehand the anamnesis?
4. As reported in the article, the lesion was a bone marrow metastasis of a 55 y.o. male with small-cell carcinoma of the lung (SCLC). Nowhere it is said how and when such diagnosis was made. In that case the primary lesion could have been, even though very rare, in the prostate. But, let’s take for granted that it was from the lung. SCLC is found mainly in smokers, no doubts about that, but not solely
. The researchers "did not know" whether the patient was or not a smoker but, "using massively parallel sequencing technology" they figured out that every 15 cigarettes there occurs a DNA mutation. Besides that revolutionary finding, they decided (discovered?) that the patient was a smoker! What if he was not?
5. If it is known that tobacco is thought (not demonstrated) to be the main cause of lung cancer, but other causes like radon, asbestos, diesel exhaust, arsenic, various chemicals, air pollution, inherited or acquired DNA mutations, all and more have been implicated by various studies. Despite that, the authors emphasize "Worldwide, tobacco smoking is the principal lifestyle exposure that causes cancer". As a matter of fact, in the prisoner’s dock they put only the tobacco, the number of cigarettes smoked.
That, in my opinion, is going too far and it leads to suppose that their aim is to make their study (of a single patient with no available smoking history) the building stone of the antismoking campaign and, therefore, a suspect conflict of interest.
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