Have you been told or been thinking that smoking causes lung cancer? Well, this is not exactly clear from recent studies.
An association between a genetic variation on chromosome 15 (15q24/15q25.1) and risk of lung cancer was found by three independent studies. But the link to smoking, or more scientifically nicotine dependence, is not clear. Some of the studies are still preliminary. So it is still possible that people with 'abnormal' chromosome 15 tend to be affected by environment - smoking - more easily and therefore are more likely to develop cancer in the long run.
We'll see if further studies with more - up to millions of - people can make it clear.
The papers mentioned here are: