According to a recent study, a bacteria that typically causes dental plaque may be responsible for a resistant form of colorectal cancer.
Researchers discovered that the bacteria, which seems to shield cancer cells from cancer-fighting medications, was present in 50 percent of the tumors examined. They believe this could pave the way for new cancer screenings.
In the United States, colon cancer is the second-leading cause of cancer deaths. According to the American Cancer Society, it’s expected to kill over 53,000 people in 2024.
Colorectal cancer cases have also gone up significantly among younger people. Between 1995 and 2019, colon cancer cases have shot up from 11 to 20 percent, in those younger than the age of 55. To make matters worse, many of these cases are diagnosed at the more aggressive stages.
Dr. Flavio Rocha, a physician in chief and surgical oncologist, said that while colorectal cancer is very treatable if caught early, they are still unclear what is causing the sharp increase in cases among younger people.
Unfortunately, the new research doesn’t tell us why the numbers are increasing – it’s still too early to say that the bacteria is responsible for the cases in younger patients.
The Bacterium Responsible
Researchers have suspected there may be a link between colorectal cancer and fusobacterium nucleatum, for nearly a decade. The bacteria, which is normally only found in the oral cavity, is responsible for plaque buildup and gum disease.
However, it’s unclear how the bacteria can move through the gastrointestinal tract to affect tumor cells in areas where the bacteria typically aren’t able to survive.
In the recent study, researchers looked at the bacterial composition of nearly 200 colon cancer tumors, in addition to stool samples from over 1,200 patients, half of whom were healthy.
They eventually discovered that the bacteria has two separate subspecies, one of which seems to protect colorectal tumors from cancer-fighting medications.
In healthy individuals, T-cells, a type of immune cell, can recognize and attack cancer cells. However, this bacteria attracts a different type of immune cell into the tumor, one that makes them immune to the T-cell’s attacks.
In the study, this subspecies was seen in half of all colorectal cancer cells. Corresponding stool samples also had higher levels of the bacteria subspecies, compared to the control.
Researchers also noticed that those with higher levels of the bacteria had very aggressive cases that did not respond to cancer-fighting drugs.
When they transplanted the bacteria to mice, they noticed the formation of precancerous polyps, an early warning sign of cancer. However, they have not yet been able to prove the causation in humans.
