Helicobacter pylori is a bacterium that causes stomach ulcers. Those ulcers cause chronic inflammation and damage in tissue in the stomach, which increases the risk of gastric cancer. Scientists at Fred Hutchinson Cancer Research Center and Zhengzhou University have now identified one strain of that microbe that has a strong connection to cancer. The researchers are hopeful that this work will help improve diagnostic tests and therapeutic strategies; their findings have been reported in PLOS One.
"We've known the H. pylori bacterium has a strong correlation to stomach cancer, but it's been difficult to pinpoint why certain patients, especially in areas like Northeast Asia, are more susceptible to stomach cancer," explained the senior author of the study, Dr. Nina Salama, a member of Fred Hutch's Human Biology and Public Health Sciences divisions. "While it's preliminary in nature, these results could be the first step towards identifying the highest risk groups and improving screening and treatment plans."
Patients at Henan Cancer Hospital in Henan, China were recruited for this study, including 24 without cancer and 25 with gastric cancer. Stool and stomach endoscopy samples from these individuals allowed the researchers at Fred Hutch to assess a gene in the H. pylori genome. Specifically, they evaluated the EPIYA D variant of the cagA gene. They found that 91 percent of the cancer patients carried an H. pylori strain with the EPIYA D variant.
H. pylori like to take up residence in the mucosal layer of the human stomach. It’s a common microbe, and over 50 percent of our planet’s population is thought to carry it. Considering that, it's no surprise that the World Health Organization (WHO) identified stomach cancer as the sixth most common type and the third leading cause of cancer deaths in 2018.
"Unfortunately, infections like H. pylori directly or indirectly cause up to 20 percent of cancers worldwide," noted Salama. "But knowing the cause gives us a clear target to develop vaccines for prevention or tools to better recognize risk."
There are caveats to this study, given the small sample size. But the teams at Fred Hutch and Zhengzhou University are hoping to do similar research in the future with a larger group of patients.
In the video from the New England Journal of Medicine, learn more about research on the connection between H. pylori and gastric cancer.