Reading a just outdated issue of The Economist, I find this article in the science section about how HIV treatments could be used to treat cancer.
One of the things many people interested in biology but without a background in biology believe (I hope I am not just describing myself here) is that information goes only in one direction: genes - mRNA - proteins. Actually the opposite is true. Enzymes such as reverse transcriptase can copy can include fragments of RNA into DNA. This is of course a technique used by viruses in order to alter the genetic programme of a cell to produce more copies of the virus. This system is also used to change the genetic programme of a cell during development so if the work of the enzyme is hindered so is development (at least in some crucial steps).
It seems that cancer cells have a lot of reverse transcriptase (this is, unfortunately, not explained in the article) and thus treatments used to prevent viral diseases could be used to hinder tumour growth. In vivo experiments with mice transplanted with human cancer cells show that there is a correlation between tumour growth and the use of HIV treatments that hinder the reverse transcriptase enzymes.
It is one more example of how development and cancer are connected (my take, and I don't claim to be the first one with this insight) is that we would not have cancer if we were not the result of developmental processes.