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Scientists Crack 'Entire Genetic Code' of Cancer
Entropy98 writes "Scientists have unlocked the entire genetic code of skin and lung cancer. From the article: 'Not only will the cancer maps pave the way for blood tests to spot tumors far earlier, they will also yield new drug targets, say the Wellcome Trust team. The scientists found the DNA code for a skin cancer called melanoma contained more than 30,000 errors almost entirely caused by too much sun exposure. The lung cancer DNA code had more than 23,000 errors largely triggered by cigarette smoke exposure. From this, the experts estimate a typical smoker acquires one new mutation for every 15 cigarettes they smoke. Although many of these mutations will be harmless, some will trigger cancer.' Yet another step towards curing cancer. Though it will probably take many years to study so many mutations."
The critical point here is that most of these mutations are acquired *after* the cancer gets going, regardless of whether the mutagen in question is still being administered.
Therefore, it's not proper to infer a linear relationship between the dose of mutagen and the number of mutations.
Beyond that, the numbers involved in that extrapolation seem to have been pulled out of thin air, and I question whether they knew the smoking history of the individual who donated the material that created that cell line. (The lung cancer in question had 30,000 mutations, so by their logic the smoker must have smoked 345,000 cigarettes, or 17,250 packs of 20. That's a pack a day for 47 years, which is admittedly within the bounds of possibility, but still an awful lot of smoking.)
Whatever. Smoking is still awful for you, but this kind of nonsensical extrapolation without regard to detail is terribly annoying.
That's pretty much on target. UV light is absorbed by DNA, and it causes changes like Thymine-Thymine dimers (ATCG are DNA bases, a T-T dimer is when two adjacent T's on the same strand bind to each other). Cells have DNA repair mechanisms, some of which are accurate, others of which are not. If the repair is inaccurate you have a mutation in a semi-random location (needs something like two adjacent thymines, and it probably needs to not be in it's condensed storage form). A mutation in each of about 8 genes that control the cell cycle will lead to uncontrolled replication and further mutation. Certain types of cells are vulnerable to different things, and require certain genes to be knocked out (or overexpressed) to form certain types of cancer. It's all very random, but there are trends within each type of cancer (hence its behavior).