The organism in question is Porphyromonas gingivalis. This bacterium has been found to be present in 61 percent of patients who are suffering with esophageal squamous cell carcinoma, according to a new study.
Esophageal squamous cell carcinoma is cancer arising from the esophagus (or oesophagus), which is the muscular food pipe that runs between the throat and the stomach. A second type of cancer is associated with the food pipe, called adenocarcinoma. However, it is esophageal squamous cell carcinoma that is more common. In the U.S. there are around 15,000 cases per year.
Those with the condition experience difficulty in swallowing and associated weight loss. Other symptoms vary, and can include pain when swallowing, a hoarse voice, enlarged glands around throat, and sometimes the coughing up of blood. Squamous-cell carcinoma relates to a cancer of the lining of the skin that lines the digestive tract. Depending of the nature of the condition, surgical removal of the affected esophagus may offer the possibility of a cure. Other treatments include radiotherapy and chemotherapy.
The association between a common oral bacterium and the form of cancer has been made by researchers based at the University of Louisville School of Dentistry. The team was led by Dr. Huizhi Wang, who serves as the assistant professor of oral immunology and infectious diseases.
The bacterium Porphyromonas gingivalis is a Gram-negative, rod-shaped, anaerobic, pathogenic organism. Enzymes produced by the bacterium can attack collagen. Periodontal, or gum, disease is one of the most common infectious diseases worldwide. In its more severe forms, such as periodontitis, the condition causes loss of the bone that supports the teeth. In addition to gum disease, the bacterium has been linked to rheumatoid arthritis.
To arrive at the association between esophageal squamous cell carcinoma and the bacterium, the medical scientists tested tissue samples from 100 patients with the type of cancer and compared these with 30 subjects who did not have this form of cancer. These subjects acted as controls.
Samples were examined for the expression of lysine-gingipain. This is the collagen-busting enzyme produced by P. gingivalis. In addition, the researchers examined the samples for levels of bacterial cell DNA from samples taken from esophageal tissues.
It was found that both the unique enzyme and bacterial DNA were found in much higher levels in the cancerous tissue of esophageal squamous cell carcinoma patients compared with surrounding tissue or from the control subjects.
Furthermore, it was found that P. gingivalis was linked with factors like cancer cell differentiation, metastasis and patient survival rate.
As to why this association might be, Dr. Wang speculates that either esophageal squamous cell carcinoma cells create a preferred environment for the bacterium (so the bacterium gravitates towards cancerous cells) or, in some way, P. gingivalis is a contributor to the cancer formation.
The are two implications from the research. The first is that P. gingivalis infection could present a risk for developing cancer of the esophageas. By implication, the elimination of the oral bacterium acts as a safety measure to decrease the chance of someone developing the specific form of cancer. Given that the cancer can be triggered by other factors, eliminating the organism will not eliminate the risk of developing esophageal cancer altogether. This would direct activities (and hence medical recommendations) towards improving oral hygiene.
The second implication, is the presence of the bacterium can potentially function as a biological marker (biomarker) for the specific type of cancer. This would allow medical professionals to make an earlier diagnosis and treat a patient in a more targeted fashion more quickly. It may be possible, should this finding be supported, to use genetic methods target the bacterium as a means to signal where cancer cells are, facilitating a more effective targeting of anti-cancer drugs.
The research is published in the journal Infectious Agents and Cancer. The research paper is titled “Presence of Porphyromonas gingivalis in esophagus and its association with the clinicopathological characteristics and survival in patients with esophageal cancer.”
This article is one of Digital Journal’s Essential Science columns. Each week we explore a topical and important scientific issue. Last week we explored the possible risks to the food chain for the herbicide glyphosate; and the week before we explored bio-designing yeast to improve biofuels.
