Rogue Gene Increases Cancer Risk
Written by Carolyn Chiu
Edited by Theodore Do
May 2, 2021
Edited by Theodore Do
May 2, 2021
When we mention evolution, we usually think of improvement. This definition is not necessarily true in the context of biology. Take humans, the closest evolutionary relative of chimps. Although we are certainly more intelligent than our hairier counterparts, we also have a higher genetic predisposition for developing carcinoma cancers.
The most recent common ancestor of humans and chimpanzees possessed the SIGLEC12 gene, which produces a protein that contributes to the immune system. While chimpanzees continue to produce functional Siglec-12 proteins, the SIGLEC12 gene in humans suffered a mutation that rendered our Siglec-12 proteins incapable of fulfilling its original function. Over years of evolution, the majority of the population has stopped producing this protein altogether. The SIGLEC12 gene was discovered two decades ago, but there have been minimal efforts in further research because the SIGLEC12 gene was believed to be irrelevant. However, Ajit and Nissi Varki at the University of San Diego recently discovered that this dysfunctional protein bears side effects for the 30% of people who still produce it.
First, the Varkis’ research team used an antibody to detect the Siglec-XII protein (referenced with Roman numerals to differentiate it from the functional form) in healthy tissues versus advanced cancerous cells. 30% of the healthy samples possessed this protein as expected. In contrast, this protein was present in the majority of cancer patients. When they moved on to cancer patients, they found that 80% of the cancer patients possessed this protein, and the 20% who did not had better health prospects overall. These statistics prove there to be a correlation between the SIGLEC12 gene and greater carcinoma risk. In a follow-up experiment, they injected one group of laboratory mice with Siglec-XII-producing tumor cells and another group with tumor cells lacking Siglec-XII. The cancers of the test group grew significantly faster than the cancers of the control group and quickly developed into advanced stages, demonstrating causation between Siglec-XII and cancer development.
What can we do with this knowledge? The Varkis have already started developing an accessible urine test to detect the protein responsible for this phenomenon. They plan to introduce a chemotherapy treatment using antibodies to selectively target cancerous cells with the Siglec-XII protein in the future. Unlike the uncertain direction of evolution, the field of medical research is always improving.
Image Source: “Stress Neuralgia Headache” by Christian Dorn licensed under CC-0