Human Evolution May Be Responsible for Increased Risk of Developing Cancer
Even in the absence of risk factors such as the use of tobacco and genetic predisposition, human beings are susceptible to developing tumors that lead to colorectal, lung, prostate and breast cancers. A study led by researchers from UC San Diego in collaboration with the Moores Cancer center explains why this is so.
The study suggests that a unique evolutionary gene mutation may partly be to blame. Ajit Varki, a senior author of the study, who’s a professor at the UC San Diego School of Medicine, explained that the siglec-12 protein of a human’s immune system, which is produced by the siglec-12 gene, mutated in a way that eradicated its ability to differentiate between the body’s own microbes and foreign microbes, which led to its elimination through evolution.
This doesn’t mean the natural process has been wiped out completely from the population. Instead it presents in some people a siglec-12 dysfunctional protein, which increases an individual’s risk of developing cancer. The study was published in “FASEB BioAdvances.” Ajit Varki led this study with Nissi Varki, who is a pathology professor at the University of California School of Medicine.
The researchers used both cancerous and normal tissue samples in their study. They found that nearly 30% of individuals whose bodies still generated siglec-12 proteins were more than two times at the risk of developing an advanced cancer. This is in comparison to individuals who do not produce the siglec-12 protein.
While chimpanzees still generate functioning siglec-12, the gene has been eliminated in more than half of the global population. Since its discovery, the protein was thought to be of no relevance, which may explain why few additional studies on the protein have been conducted.
The researchers also discovered that more than 80% of patients diagnosed with advanced-stage colorectal cancer had the siglec-12 gene. These terminal patients had substantially worse outcomes in comparison with the patients who did not have the gene. Varki explained that the results of the study suggest that the people whose bodies still generate the siglec-12 protein are more at risk of developing an advanced cancer.
To validate their findings, the researchers introduced tumor cells in mice that were engineered to produce the siglec-12 protein. The cancers were observed and noted to grow much faster in addition to switching on various biological pathways that are associated with advanced cancers. This was in comparison to other tumor cells that did not have a functioning siglec-12 protein.
In addition to this important discovery, the research team also developed a urine test that could be utilized in the detection of the siglec-12 protein.
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