The environment has a great impact on our health and the location we live affects our body, facts a new study proves. Konstantinos Voskarides, researcher at the University of Cyrpus’ Medical School, tried to explain the increase of cancer incidence worldwide in his study.
According to its findings, pockets of human populations and geographical locations are seemingly at higher risk of cancer incidence than others and populations living in very low temperatures, like in Denmark and Norway, had among the highest incidences of cancer in the world.
The study which was published in the journal Molecular Biology and Evolution, early in December, has advanced a new hypothesis: there is an evolutionary relationship that exists between adaptation at extreme environmental conditions, like cold and high altitudes, and increased cancer risk in humans.
The researcher concluded that the extremely cold environment contributed to the cancer risk. To do so, the researcher focused on the effect of low temperatures, either within Arctic/Scandinavian climates or high altitudes. He also analysed the relationship between cancer risk and local average annual temperatures in those areas.
In his study, Voskarides carefully examined the most accurate and reliable data of worldwide cancer incidence (the Globocan 2012 database contains a variety of incidence/prevalence analysis per country or per cancer type) and also sifted through genetic clues among 247 different cancer genome-wide association studies.
He also probed the available literature on cancer incidence and genetic data of human populations living in extreme cold and extremely high altitudes.
While working on his research, the researcher found a striking pattern which began to emerge, with the highest incidence of certain cancers linked to those populations living in the coldest environments. The analysis of 186 human populations showed a great linearity of high cancer incidence the lower the environmental temperature.
The genetic evidence was also clear and highly significant. Genes that were examined from populations surviving under extreme environmental conditions were also found predisposed to cancer. Also, among the highest cancer associations for the studied genes is colorectal cancer for Natives Americans and Siberian Eskimos, oesophageal cancer and lung cancer for Siberian Eskimos, leukaemia for Oromo (a high-altitude population in Ethiopia) and a variety of cancers for high-altitude dwelling Andeans and Tibetans.
Natural selection has especially favoured tumour suppressor genes in those populations instead of oncogenes, according to the study.
The researcher said that the findings of this study provide evidence that genetic variants found to be beneficial in extreme environments can also predispose people to cancer. He added that cell resistance at low temperatures and at high altitudes probably increases the probability of malignancy. This effect could hardly be filtered out by natural selection since most cancers appear at a later age, after most people have their children.
“These data show that these populations exhibit extremely high cancer incidence, especially for lung, breast, and colorectal cancer,” said Voskarides.
According to Voskarides, the evidence found proves that cancer rates are increased in those populations through natural selection procedures. The researcher believes that his study is the first study that provides evidence that high cancer risk may be a result of evolutionary adaptation in certain environmental conditions.