A mysterious rise in aggressive colon and stomach cancers may be partly fueled by bacteria, two new studies suggest.
Experts have been baffled by the surprising rise in colon and rectal tumors over the past two decades, which are increasingly affecting young people.
Theories explaining this increase include more people eating diets high in junk food and increasing obesity rates. But researchers at the Fred Hutchinson Cancer Center in Seattle have discovered that Fusobacterium nucleatum, which lives in dental plaque, may explain why some colon tumors are so difficult to treat.
Half of all CRC tumors – the most aggressive and deadly – contained the bacteria, which can travel from the mouth to the intestine through swallowing.
Meanwhile, Chinese and Singaporean scientists showed in a study this week that bacteria normally found in the throat, mouth and vagina, called Streptococcus anginosus, can promote the growth of stomach cancers.
S. anginosus colonizes the mucous membranes of the nose and mouth and can cause abscesses, tissue infections such as flesh-eating disease, infections of the inner lining of the heart, and joint infections.
The graph above shows cases of colon cancer in people under 50 by year. There is a decline in 2020 as the Covid pandemic led to a reduction in the number of people attending screenings.
Bowel cancer can cause blood in your stool, a change in bowel habits, a lump in the intestine that can cause an obstruction. Some people also experience weight loss because of these symptoms.
Researchers hope their findings will lead to better cancer treatments that target the gut’s bacterial microbiome and eliminate stealth bacteria.
Researchers at the cancer center conducted laboratory research to see how the bacteria Fusobacterium nucleatum influences the environment that allows tumor cells to grow.
They isolated the strains of bacteria from selected cancer patients in North America and Europe. They also studied the genetic makeup of the bacteria in more detail.
Samples from cancer patients were analyzed for the presence of the bacteria, which involved extracting DNA from tissue samples and using genetic sequencing techniques to identify the species.
They then analyzed the abundance of the bacteria in stool samples from people with and without colon cancer to assess any potential links between the bacteria colonizing the body and promoting the disease.
The researchers found that a specific subtype of the bacteria was present in tumor tissue in about 50% of cancer cases, although they did not specify how advanced the stages of these cancers were.
They found this microbe in greater numbers in stool samples from colorectal cancer patients than in stool samples from healthy people.
They found that cancer treatments that target both bacteria in the body and tumor cells could improve patient outcomes.
The researchers said the bacteria could be behind the rise in cancers among young people, although they couldn’t be sure, given that many of their study subjects were over 50. .
But co-senior author Dr Susan Bullman said the findings raised “the question of whether there are high levels of this bacteria in early-onset colorectal cancer, which is increasing globally for unknown reasons.”
Actor Chadwick Boseman died in 2020 after a four-year battle with colorectal cancer
Meanwhile, in Asia, researchers have reported that another common and generally harmless bacteria plays an important role in causing stomach cancer, S. anginosus, which is part of the normal flora of the mouth, nose, throat, intestines and vagina.
The bacteria can cause abscesses, pneumonia, heart infections, urinary tract infections and tissue infections.
In studies with mice, they determined that when the body’s immune system is weakened, the bacteria can spread to other parts of the body and cause an inflammatory response that can cause acute damage to the stomach lining , an infection called gastritis.
This can trigger cancer growth, in some cases doubling the size of tumors. Another type of bacteria, Helicobacter pylori, is also known to cause stomach ulcers, which increase the risk of developing gastric cancer, the fifth most common type worldwide.
Professor Joseph Sung Jao-yiu from the Chinese University of Hong Kong and co-author of the study said: “This lays an important foundation for further studies in humans that will help clinicians better treat and prevent the gastric cancer caused by bacteria.”
Tumors get a lot of help from the bacteria that live in our mouth, throat, and intestines. These bacteria are generally harmless, except that they occasionally cause treatable illnesses.
As illustrated above, lack of energy, unintentional weight loss, constant indigestion, difficulty swallowing, nausea, and a lump at the top of the stomach are all warning signs and symptoms of breast cancer. stomach.
Rates of colorectal cancer (CRC) in younger age groups have seen a historic 50% increase among adults under age 50 in the United States since 1999 – what is considered “early” cancer or when the Cancer occurs between the ages of 18 and 49. .
It kills around 52,000 people each year.
Studies suggest that globally, cases have increased by 80% in this age group over three decades, reaching 3.26 million cases per year in 2019, up from 1.82 million in 1990.
The F. nucleatum bacteria hides in the mouth and makes cancer much harder to treat by acting as a protective covering around tumor cells, shielding them from targeted drugs.
In their study published in the journal NatureCancer researchers at the Hutch Center examined levels of the bacteria in stained tumor tissue taken from 200 CRC patients.
Dr Susan Bullman, cancer researcher at Fred Hutch, said: “We have consistently found that patients with colorectal tumors containing Fusobacterium nucleatum have poor survival and a poorer prognosis than patients without the microbe.”
“We now discover that a specific subtype of this microbe is responsible for tumor growth.” This suggests that treatments and screening targeting this subgroup of the microbiota would help people at higher risk of more aggressive colorectal cancer.
Actor Chadwick Boseman, famous for his roles in the films Black Panther and Get on Up, has died of early-onset CRC at the age of 43.
Stomach cancer kills approximately 11,000 Americans each year. Sixty-two percent of people with stomach cancer are diagnosed after the cancer has already spread, either regionally or distantly, beyond where it started. begin. This makes it incredibly difficult to treat.
Professor Sung, who co-led the Asian study, said: “Our results suggest that long-term infection with S. anginosus causes intense chronic gastritis comparable to infection with H. pylori.
“In fact, these two pathogens may act collaboratively to promote gastric inflammation and ultimately gastric cancer.” This could change the way we approach disease prevention and treatment.
Their research was published in the journal Cell.