Stomach cancer remains one of the world’s most serious forms of cancer, affecting nearly one million people each year.
It is currently the fifth most common cancer worldwide and one of the leading causes of cancer-related deaths.
Although doctors know that factors such as smoking, obesity, and infection with the bacterium Helicobacter pylori can increase the risk of stomach cancer, many questions remain about how the disease begins and develops over time.
Now, an international team of researchers has made an important breakthrough by studying the genetic changes that occur in the normal lining of the stomach long before cancer develops.
The research, published in Nature, provides one of the most detailed views yet of how mutations build up in stomach tissue throughout life and offers clues about the earliest stages of cancer formation.
The study was led by scientists from the Wellcome Sanger Institute, the Broad Institute of MIT and Harvard, the University of Hong Kong, and several collaborating institutions. For the first time, the researchers systematically examined somatic mutations in normal stomach tissue.
Somatic mutations are genetic changes that occur in cells during a person’s lifetime. Unlike inherited mutations, these changes are not passed from parents to children. Instead, they gradually accumulate as people age.
Recent advances in DNA sequencing technology have allowed scientists to study these mutations in much greater detail. By tracking the patterns of mutations in normal tissues, researchers can learn how cells change over time and identify the earliest warning signs of cancer.
To carry out the study, the team collected 238 samples of normal stomach glands from 30 individuals. Eighteen of the participants had stomach cancer, while twelve did not.
Using highly specialized techniques, including laser capture microdissection and whole-genome sequencing, the researchers examined the complete DNA sequence of individual stomach glands.
One surprising discovery was that the normal stomach lining appears to be remarkably well protected from the harsh acidic environment inside the stomach. Many scientists expected that constant exposure to stomach acid might leave a clear genetic fingerprint on stomach cells.
However, the researchers found that mutation rates in normal stomach glands were similar to those seen in many other tissues throughout the body. This suggests that the stomach has effective protective mechanisms that shield its cells from acid-related damage.
The study also revealed that genetic changes linked to cancer become increasingly common with age. By the age of 60, nearly ten percent of the stomach lining is occupied by cells carrying so-called driver mutations.
These mutations occur in genes that can promote cancer growth. While having a driver mutation does not automatically mean someone will develop cancer, these cells may have a greater chance of becoming cancerous in the future.
The researchers found that people with chronic inflammation of the stomach tended to have a higher proportion of these mutated cells. This finding supports growing evidence that long-term inflammation may encourage the accumulation of harmful genetic changes and increase cancer risk.
Another important observation came from comparing normal tissue with cancerous tissue. In patients who already had stomach cancer, some areas of tissue that appeared normal under the microscope had already begun to show genetic changes associated with cancer development.
These tissues contained more mutations than expected, suggesting they were already moving toward a cancerous state. Fully developed cancer tissues contained far higher numbers of mutations, indicating that genetic damage accelerates as cancer progresses.
Perhaps the most unexpected finding involved unusual chromosome changes. The researchers discovered that some stomach lining cells contained three copies of certain chromosomes instead of the usual two.
This condition, known as trisomy, affected chromosomes 13, 18, and 20. Interestingly, these changes were not found consistently in all participants and have not been commonly observed in normal tissues from other parts of the body.
The discovery puzzled the researchers because it suggests that some people may have been exposed to an unknown factor capable of causing these unusual chromosome changes. The source of this possible mutagen remains a mystery and will require further investigation. Identifying it could potentially reveal a previously unrecognized risk factor for stomach cancer.
The findings add an important piece to a growing effort by scientists to create a detailed mutation map of the human body. By comparing mutation patterns across different organs and tissues, researchers hope to better understand why certain cancers develop and how they might be prevented.
Beyond cancer, this work may also help scientists understand other diseases linked to the accumulation of genetic mutations over time. The ability to study normal tissues in such detail is opening a new window into human health and aging.
While more research is needed, the study provides valuable insights into how stomach cancer may begin many years before symptoms appear. It highlights the role of aging, inflammation, and possibly unknown environmental factors in shaping the genetic landscape of the stomach.
As scientists continue to uncover these hidden changes, they move closer to finding new ways to detect cancer earlier, identify people at higher risk, and develop more effective strategies for prevention and treatment.
The study was published in the journal Nature.
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