Oral Bacteria May Cause Colon and Other Cancers to Spread

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Cancer is the second most leading cause of death worldwide. In the United States alone, new cancer cases in 2019 were estimated at 1.75 million, over 600,000 resulting in death. This article will provide a deeper understanding of the critical role oral bacteria can play in cancer.


Relationship Between F. Nucleatum and the Development of Colorectal Cancer

Colon cancer is one of the most common forms of the disease in both men and women. In the U.S., it is the second leading cause of cancer deaths. Studies show that a common oral bacterium known as F. nucleatum is linked to the velocity of growth in colon cancer, as well as periodontal disease.

Colorectal cancer is a common malignant tumor affecting people worldwide, and about one-third of these cases are correlated with Fusobacterium nucleatum. F. nucleatum is an oral bacterium that's been regarded as an opportunistic pathogen found in samples of patients with oral, intestinal, and other types of infections.

A study conducted in 2017 provided the original evidence for F. nucleatum’s potential to cause the spread of cancer cells throughout the body. The study showed that when human colon tumors containing F. nucleatum are injected into a mouse, cancer cells, including live bacteria, will break off and reattach to the liver.

There is no evidence that this bacterium is directly initiating cancer or releasing molecules that are causing the cancer cells to migrate. Instead, F. nucleatum sticks to and even enters cancer cells using the protein Fap2, which docks with sugars overrepresented on the surface of cancer cells. This in turn causes cancer cells to release two proteins known as IL-8 and CXCL1, which are members of the cytokine protein family that play critical roles in immune system activation against infections. The cytokine combination of IL-8 and CXCL1 was previously shown in multiple studies to induce the spread of cancer cells. F. nucleatum also produces a molecule known as FadA adhesin, which has been found to stimulate the growth of cancerous cells.

Finding pro-metastatic human proteins that are released by cancer cells upon bacterial infections opens the door for future research. This will hopefully provide insight into the potential blocking of the secretion of cytokines to combat metastasis induced by bacteria.


Relationship Between Oral Bacteria and Other Cancers

Oral bacteria isn’t only linked to colon-specific cancers, but also to esophageal cancers. Analyzed data from microorganism samples found that in the mouths of 120,000 people, there were two predominant forms of bacteria that not only lead to gum disease, but also show higher risks for esophageal cancer.

Researchers conducted a decade-long study that analyzed oral wash samples taken from over 122,000 people to find out who developed esophageal cancer. Researchers then compared the genetic information of participants who developed esophageal cancer to the genetic information of those who did not.

The study found that the presence of Tannerella forsythia, a member of the red complex of periodontal pathogens, and an abundance of the oral bacteria porphyromonas gingivalis were tied to increased risks of esophageal adenocarcinoma (EAC) and esophageal squamous cell carcinoma (ESCC), respectively. This proves the need for further research on the role of oral microbiota, which may lead to preventative strategies for esophageal cancer and identifications for such cancers.