Posts Tagged ‘lung cancer’
More than a billion people worldwide smoke tobacco. With a 20-fold greater risk of developing lung cancer than nonsmokers, plus increased risks of other types of cancers, choosing to smoke represents the most significant carcinogenic exposure confronting public health professionals today. A recently completed study published in Nature (se below) reports on the sequencing of DNA from a small-cell lung cancer victim. Tobacco smoke deposits hundreds of chemicals in an individual’s airways and lungs including numerous mutagens. The investigators have used massively parallel sequencing to illuminate the distinctive mutations associated with exposure to cigarette smoke carcinogens, as well as the signature of DNA repair activities.
The investigators didn’t speculate about the policy implications of this work, but things that come to mind for me include better early detection of pre-cancerous conditions, genomic therapies that intervene on a macromolecular level and an airtight method for denying someone health insurance coverage for lung cancer treatment because of self-inflicted tobacco carcinogenesis.
One of the worrisome statements made in the discussion section was that, on average, lung cancer develops after 50 pack-years of smoking (where a pack-year is 7,300 cigarettes, representing the number smoked in a pack a day for a year), or an average of one mutation for every 15 cigarettes smoked, which could potentially transform a normal cell into a cancerous one that eventually clones into a tumor.
There are a couple of epidemiological modeling papers cited for that conclusion that should be looked in on later, but the 50 pack-years assessment provoked a bit of an oh-shit moment, because if I’m understanding the number properly, 50 pack-years is around a pack a day for one year; the dose-response relationship is cumulative, so the same risk would be associated with half a pack a day for two years, and so forth. Tobacco contains a lot of other carcinogens other than mutagens, which initiate a carcinogenic response; these other carcinogens are promoters, which accelerate the growth and development of a tumor. So, even if you’ve only currently a “light” smoker, you’re probably still screwing yourself health-wise; even if you quit years ago, you may have macromolecular or cellular injury now, that will eventually turn into lung cancer, but it just hasn’t progressed to the that you’re experiencing adverse effects. It’s just another reason for not smoking at all or stopping at the earliest instance possible, in order to preserve your health (and insurance).
Pleasance, E.D. et al. 2009. A small-cell lung cancer genome with complex signatures of tobacco exposure. Nature. 463, 184-190 (14 January 2009) http://www.nature.com/nature/journal/v463/n7278/full/nature08629.html
This is something that sounds so cool as an exposure monitoring technology that I hope it pans out experimentally and can be deployed.
Lung cancer cells may exude volatile organic compounds different than normal cells, principally as the byproducts of oxidative stress and byproducts of reactive oxygen species (ROS)-induced processes. The differences may be detectable in breath samples. A monitoring tool is being investigated as a non-invasive way to identify non-small-cell lung cancer. The objective for this tool would be to increase the odds of starting treatment while the disease is in its early stages and still localized. The analytical method involves an array of gold nanoparticle sensors in combination with pattern recognition methods; this level of description is what has been found in the press coverage, and having written it I realize I know as much now as I did before hearing about this technique, which is zip. I’m reading the paper trying out the methodology with headspace samples of tumor cell lines, published in the journal Small and realizing I have a lot of catching up to do on analytical methods. . . .
The sensor can discriminate the breath of normal individuals from lung cancer patients, overcoming the problem of high humidity in the breath samples (a problem with the prior method using carbon nanotubules) and without requiring preconcentration of the breath samples (which would require more complex laboratory techniques). Hossam Haick, the lead investigator estimates this method could become available as a diagnostic tool in about three to five years.