Does evolution play a part in where we develop cancer?

Scientists from Deakin University, in partnership with France’s National Centre for Scientific Research (CNRS), have suggested that the reasons people and animals develop cancer in some organs but not in others may have more to do with evolution than any lifestyle or genetic factors.

Dr Beata Ujvari, from Deakin’s Centre for Integrative Ecology, said the difference in cancer prevalence between organs has previously been accredited to intrinsic factors such as stem cell numbers and high mutation rates in certain organs, or to extrinsic factors such as cigarette smoking and pollution.

Her team proposes that evolution has protected essential but unpaired organs (such as the heart) from tumour development, while larger and often paired organs (such as the liver) are more likely to develop cancers as they might be less essential to survival.

“For example, the relative rarity of heart and brain cancers can potentially be attributed to the low cellular turnover in these organs, and therefore to the low opportunities for cancer-causing mutations,” she said.

“We think that turnover rates may also be low in these organs because they are crucial to survival. While the cell turnover rate is approximately 4–15% per year in the heart and 2.7% in the brain, the intestinal epithelium completely self-renews approximately every five days.”

The scientists predict that after the effects of stem cell numbers, rates of cell division and exposure to toxins and infection are taken into consideration, the ecology of different organs will account for considerable differences in vulnerability to cancer.

“This kind of evolutionary ecological analysis of variations in different organs may prove of great value in cancer prevention and treatment,” Dr Ujvari said.

The research, published in the journal Trends in Cancer, is part of an International Associated Laboratory (Laboratory Without Walls) project, awarded by the CNRS to build collaboration between the centre and Deakin University. The project will allow Dr Ujvari to explore the links between evolution and cancer with her French colleague, Professor Frédéric Thomas.

“Oncology as a scientific field has, until now, developed in relative isolation from ecological and evolutionary sciences,” said Dr Ujvari. “This is unfortunate because links between these disciplines have the mutual potential to reveal new perspectives and lines of research.

“For instance, while cancer is traditionally considered as a distinct pathology from a medical point of view, interdisciplinary approaches reveal that it is instead an unavoidable dynamic phenomenon governed by evolutionary principles and ecological relationships.

“This project aims to fill an important gap in ecology and evolution, exploring a research direction never explored before.”