[TigersEye]

This, IIRC, is a somewhat controversial study.

That may be true. It indicates that there is a possibility though.

Finally, it is a scare headline only -- how many otherwise healthy chemicals (or even vitamins) would, in an in vitro study, speed up cancer?

I don't know but if they aren't in cigarette smoke it would be a non-sequitur to this subject.

[jjsheridan5]

That may be true. It indicates that there is a possibility though.

Of course it is a possibility. And there is a possibility that nicotine slows down cancer. It is possible that nicotine has no effect. In vitro studies can point you to further areas of research, and no more.

I don't know but if they aren't in cigarette smoke it would be a non-sequitur to this subject.

Not really. People read the headline "Nicotine Speeds up Cancer", and they don't necessarily understand the context. The context is that that statement means almost nothing, as a practical matter, except possibly to provide another area of research. This is not a "non-sequitur" -- the headline is designed to scare people unnecessarily, by not providing context. A non-scare headline would be more along the lines of "We have no idea what nicotine's effect is on lung cancer". You say "speeds up cancer", and most people will naturally assume that you mean in cancer patients, not in a petri dish.