Why is it proving almost impossible to cure many cancers? They seem to have astonishing powers of evolution of resistance to the chemotherapy we bombard them with. And the more we hit them the more extreme their evolution becomes. In Body by Darwin I explain that severe departures from the normal diploid complement of chromosomes typify cancers moving toward greater malignancy. Typically they can double their chromosome number and then whittle away at their outsize genomes to produce a range of cells with different chromosomal irregularities in which many gene copies and sometimes whole arms of chromosomes, even entire chromosomes, become lost. This "genetic chaos" should prove lethal but in the strange world of cancer it occasionally does not, and gives birth to ever more malevolent clones of cancer cells. One drastic process has been recently named chromothripsis - where a whole chromosome literally shatters to pieces and is stitched back together at random by DNA repair enzymes. Again, occasionally, rather than proving lethal this has been shown to remodel chromosomes in such a way that it gives the cancer a selective advantage. Rather than the stepwise gradualism of evolution by single point mutation and selection, this wholesale upheaval reminds us of what Victorian biologists called saltation - a massive evolutionary leap - or what heretical geneticist Richard Goldschmidt, in the 1940s, called his "hopeful monster" theory.
The scientists in the report linked above have found another route to genome doubling - tetraploidy - by showing that inflammation can cause cells to fuse together. The cell fusion doubles the chromosomes in the nucleus of the fused cell and can become the source of waves of chromosomal instability - the hallmark of malignant cancer.