Natural Selection: Can it Determine Tumor Development?

Researchers hypothesize why certain cancers are more prevalent than others.

Researchers in a recent report suggested that certain cancers are more common because the affected organs have not developed the defense mechanisms that other organs have.

Scientists propose that certain large or paired organs can tolerate tumors, while smaller, more critical organs, such as the heart, cannot withstand the disease, according to a report published by Trends in Cancer. These larger organs have likely not developed the same defense mechanisms against cancer.

“The organs that are the most important to keeping you alive and capable of reproduction, such as the heart, brain, or uterus, may enjoy a better protection against cancer, all other things being equal,” said researcher Frédéric Thomas, PhD. We are not saying that this is the main factor to explain the different susceptibility of organs to cancer, but it is a factor that contributes with others.”

While most oncologists seek explanation for differing rates through examining external risk factors (smoking, UV exposure, etc) or internal factors (cell division), these researchers are suggesting that natural selection may play a key role in cancer development.

“Organs that are large or in pairs could potentially accumulate larger numbers of oncogenic manifestations without being impaired, whereas small and important organs like the pancreas could be easily compromised with only a few tumors inside,” Dr Thomas said.

If all other factors are equal, researchers state that the pancreas should be able to fight cancer easier than the kidney, according to the study. Researchers recommend that oncologists view each organ as an independent island with certain environmental conditions.

Cancer can only survive in favorable conditions, making certain organs more desirable for tumor development.

“A complete analysis requires that we take into account all the possible confounding factors," Dr Thomas said. “We cannot just look at existing statistics on cancer and the size of the organs and make a correlation to see if it works or not.”

The researchers are currently conducting a long-term study with mouse models to determine cancerous and precancerous mutations in different organs.

“It's a novel hypothesis that deserves to be explored,” Dr Thomas concluded. “We hope this paper will stimulate research in that direction.”