"Chromosomal catastrophes" have been found to occur along the evolutionary timeline of colorectal cancer development, according to new research led by the Queen Mary University of London. The findings are published in Nature Ecology & Evolution.

Lead author Dr. William Cross from the Queen Mary University of London said: "Our results change the way in which we understand how bowel cancers develop. Although the classical model of colorectal cancer development appears correct in some cases, our results suggest that we need to rethink certain aspects of it."

Prof Trevor Graham from the Queen Mary University of London said: "Bowel cancer is one of the most common cancers in the UK. Our study gives more insight into how bowel cancer develops and provides a foundation that we can build upon to develop tools to predict who is at risk of developing the disease."

As tumors grow, different cells acquire various genetic changes that allow them to adapt to their environment. The cells that acquire changes that confer the best chance of survival and growth within the environment are favored, and so increase in number.

Bowel cancer

This is the basis of cancer evolution. In this way, numerous populations of cells with different genetic codes build up, creating tumors that are highly genetically diverse or heterogeneous.

Understanding how cancers develop and change over time is a big challenge. For obvious reasons, scientists can not simply sit and watch cancer growing in a person.

The researchers from Queen Mary's Barts Cancer Institute were part of a collaborative team that set out to identify when particular genetic changes arise during bowel cancer development.

By comparing the genetics of benign and cancerous bowel tumors, the international team—led by Prof Trevor Graham (Queen Mary University of London) and Prof Ian Tomlinson (the University of Oxford and the University of Birmingham) – revealed that the benign growths were more heterogeneous than the cancerous tumors.

Also, the team identified some other striking differences between the genetic makeups of the two tumor types. Unlike the benign samples, the cancerous tumors appeared to have largely rearranged chromosomes (structures that carry our genetic information in the form of genes), with sections of the genetic code being lost or gained.

Using mathematical modeling, the researchers were able to determine when these rearrangements occurred in the timeline of cancer development. Surprisingly, they found that the majority of the genetic alterations occurred very close together in time, possibly even in a single incident referred to by the researchers as a 'chromosomal catastrophe." This event appeared to be associated with the transition from benign to cancerous tumors.