interesting
This is a very interesting and intelligent thread.
I would just like to point out that not all cancers are caused by carcinogens or mutagens. It can be a "natural" process, resulting from mutations that occur when a cell replicates.
As for a viruses (the correct plural form of this word), they could prove to be very useful for this sort of thing, but they can also be the cause of mutations. The reason women have routine PAP smears is to detect the presence of human-papilloma virus (and any abnormal cells). HPV causes cervical cancer. I do not know this particular viruses lifestyle, I only use it as a point to illustrate that the potential advantages to virus-based gene therapy are also possible disadvantages. A group in France just recently had to call off their gene therapy experiments. They were treating a severe immunodeficiency that is caused by a single gene mutation with viral vectors that introduced functional copies of the gene into children. Virtually all the children were cured by this method. Unfortunately, two of the children developed leukemias, the nature of which had never been seen before. When I read this I couldn't help but think it was not surprising. The gene therapy viruses insert more or less randomly (even the best targeting is imprecise at this point). It seems likely to me that the gene therapy target could insert into the middle of an essential cell-regulatory gene, disrupting its function and causing the cell to replicate unchecked.
Until scientists can solve all these problems, as I believe they someday will, gene therapy for cancer and other genetic diseases comes with dangers that many feel outweigh its potential benefits.
