There are a number of cancers that have been linked definitively to infectious agents. T-cell leukemia has been shown to be caused by HTLV1, a retrovirus very similar to the virus that causes AIDS. The human papillomavirus (HPV) has been implicated in cervical cancer, and primary liver cancer has been shown to be caused by the Hepatitis B virus.
There is now clear evidence that a bacterial infection commonly found in the stomach caused by Helicobacter pylori (H. pylori) is responsible for stomach ulcers and cancer of the stomach. It has been found in 70% of those individuals with stomach cancer and is carried by 50% of the world’s people. This bacterium has a characteristic corkscrew morphology – shape. It has been proposed that the H. pylori pathogen is protected from the harsh acidic conditions of the stomach by its ability to bore into the protective gastric mucosal lining. It has also been established that H. pylori infection may lead to chronic inflammation that can trigger either gastric ulcers or cancer.
Dr. Nina Salama and her team at the Fred Hutchinson Cancer Research Center in Seattle successfully created genetically modified H. pylori that lacked four essential shape-forming proteins and as a result the organism lost its corkscrew morphology. As a consequence, these modified bacteria became less effective in attacking gastric tissue. H. pylori has a shape that is shared by other virulent bacteria including Vibrio cholerae that causes cholera and Campylobacter jejuni that is responsible for bacterial diarrhea.
Currently H. pylori is resistant to treatment with traditional antibiotics. However, discoveries such as the ones made by Dr. Salama offer hope that a more complete understanding of the mechanism of infection may eventually prove useful in treating the infection and preventing gastric ulcers and cancer in the future.