Edit: just to clarify, I am asking what, if anything, the literature says can be gleaned about evolution by studying cancer, especially relating to how multicellularity evolved and the traits used to force cells under control of the organism.
Most of the original question details I had added were just my own thoughts on the topic.
Is there a sense in which cancer can be considered as a return to the unicellular "origin" of a cell?
It has always seemed to me like cancer is almost inevitable by the structure of the cell (its poor "design", essentially). The only thing standing in the way are the cellular controls: senescence/apoptosis (e.g. p53 pathway), immunosuppression (e.g. cytotoxic T lymphocytes), telomeres, etc...
So it seems like multi-cellularity did not evolve "ground-up", but was instead generated by slowly differentiating the functions of the various cells, while developing "top-down"controls against errant cellular behaviour. Thus, cancer, which occurs when these protections fail, is in some sense merely a return to an ancient evolutionary root.
I suppose some arguments against this include the fact that modern cells are vastly different than their ancient ancestors (or even modern archaea/bacteria). So the best we can perhaps say is that the core of the cell has been sufficiently preserved (ribosomes are still mostly RNA, are they not? :] ). Further, it is hard to call some of the "micro-evolutions" of cancer (e.g. interleukin-8 production) as returns to primitive behaviour. In these cases, I tend to see them as necessary occurrences to remove the "top-down" controls, rather than as integral to the destructive out-of-control growth characterizing oncogenesis. But, debatably, perhaps not all of them are (e.g. extravasation in metastasis).
Obviously this seems very simplistic, but is there any literature thinking about it this way? Or directly debunking it?