Evolution may be to blame for humans’ susceptibility to a certain cancer

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  • Some humans are more prone to developing carcinomas than others
  • This is due to the presence of a dysfunctional gene that is still present in some people
  • Researchers have now developed a urine test that can detect the presence of this protein

Humans seem to be more prone to developing carcinomas (cancers starting in the skin or tissue lining organs), in comparison to our closest evolutionary relatives – chimpanzees.

We are prone to developing advanced carcinomas even without known risk factors such as smoking and genetic predisposition being present.

Researchers at the University of California School of Medicine and Moores Cancer Center conducted a study aimed at explaining why this may be the case.

Evolution to blame

Findings of the study suggest that distinct genetic mutations that happened during the course of our evolution may be part of the reason why we are prone to developing these cancers. 

SIGLEC 12 is a primate protein-coding gene that harbours specific mutations in humans.

According to senior author of the study, Ajit Varki, “At some point during human evolution, the SIGLEC12 gene – and more specifically, the Siglec-12 protein it produces as part of the immune system – suffered a mutation that eliminated its ability to distinguish between 'self' and invading microbes, so the body needed to get rid of it.” 

He went on to say the gene is not completely gone from the body and “it appears that this dysfunctional form of the Siglec-12 protein went rogue and has now become a liability for the minority of people who still produce it”.

When the researchers studied normal tissues and compared them to cancer tissues, they found that the risk of developing advanced cancer was more than double in people who produce a SIGLEC-12 compared to those who don't. 

Only in humans and chimpanzees

The majority of the global population no longer produce the SIGLEC-12 protein because dysfunctional encoded proteins are normally erased over time, and the protein is only functional in chimpanzees.

It was believed that the gene had no relevance in cases where it was still present in humans, but the researchers found that it is in fact significant because of its prevalence in the majority of advanced cancer samples. 

"These results suggest that the minority of individuals who can still make the protein are at much greater risk of having an advanced cancer," said corresponding author, Nissi Varki.

The researchers went on to say that such a discovery is beneficial as it can be used in future for diagnostics and treatments, and the team already made progress by developing a urine test that can detect the presence of the dysfunctional protein.

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Image credit: Cottonbro, Pexels
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