H. pylori in the Stomach: A Cancer Risk

Helicobacter pylori is a type of gut bacteria that infects the lining of the stomach. It is transmitted or spread via oral-oral or fecal-oral route. Many people catch the bug through contaminated food and water. Parent-child transmission is common and many acquire the infection during childhood.

• Helicobacter pylori is one of the strongest risk factors for certain types of stomach (or gastric) cancer
• Eradication of H. pylori using antibiotics can significantly reduce the risk of developing stomach cancer

H. pylori is much more common among Asian populations and in Eastern and Southern Europe. Meanwhile, the overall incidence of H. pylori-related stomach cancer in the US and Europe has declined. However, the prevalence of H. pylori in Black and Hispanic American communities is on the rise in the US.

H. pylori causes severe inflammation of the stomach when it infects gastric epithelial cells within the stomach lining. This condition is called gastritis. Prolonged gastritis can lead to the development of ulcers, which are painful, bleeding sores. Some diseases linked to H. pylori infection include:

• Chronic gastritis, which may be followed by metaplasia and dysplasia
• Autoimmune gastritis
• Ulcers in the stomach (also known as peptic ulcers)
• Ulcers in the duodenum (first part of the small intestine)
• Gastric mucosa-associated lymphoid tissue (MALT) lymphoma
• Gastric adenocarcinoma (both diffuse and intestinal type)

H. pylori is known to be the main risk factor for stomach cancer. Notably, the World Health Organization (WHO) has classified H. pylori as a Class I (definite) carcinogen since 1994. However, while there are multiple strains of H. pylori, not every strain causes diseases like gastritis or stomach cancer. Most people will not experience symptoms or illness while infected.

It’s also important to note that this bacterium is only one possible cause of stomach cancer. Infection with H. pylori could heighten your cancer risk when combined with other risk factors like:

• Smoking
• Obesity
• Heavy alcohol consumption
• Diet low in fruits and vegetables

Successful, pathogenic (disease-causing) H. pylori strains carry a cag pathogenicity island (cagPAI) in their genome. This part of the genome encodes a needle-like injection system that allows the bacterium to:

• Attach to the stomach lining
• Inject and deliver bacterial cancer-promoting protein (e.g. CagA) into stomach cells
• Induce a strong inflammatory response
• Damage the stomach lining and prevent wound healing that results in ulcer formation through prolonged, uncontrolled inflammation

In gastric epithelial cells within the stomach lining, CagA and other genes or proteins from H. pylori can participate in several signalling pathways that control cell growth and cell invasion.

“With H. pylori, you have an infection, which causes inflammation, then healing, then more inflammation. Over time, this cycle of constant cell regeneration can result in mistakes that lead to cancer,” says Dr Patrick Lynch of the Department of Gastroenterology Hepatology and Nutrition, Division of Internal Medicine, MD Anderson Cancer Center.

“The whole process of stomach cancer risk associated with H. pylori is one of inflammation.”

Fortunately, the risk of developing stomach cancer can be greatly reduced by eradicating H. pylori infection. This can be achieved with the use of antibiotics. The following video covers the detection methods and treatments for H. pylori infection.