A common food bug picked up in childhood may be fueling a colon cancer epidemic in young people, according to a bombshell study.
Colorectal (bowel) cancer, long considered a disease of old age, is increasingly striking people in their 20s, 30s and 40s in the US and UK in a phenomenon that has baffled doctors.
Now, researchers at the University of California San Diego believe they’ve found a potential culprit: E. coli, a foodborne bacteria that infects around 75,000-90,000 Americans each year and at least 1,500 Britons.
By analyzing DNA from young colon cancer patients, the team found unique genetic changes in their digestive tracts that appear to raise the risk of tumors forming — likely triggered during childhood, when the body is still developing.
They also detected traces of colibactin, a cancer-linked toxin produced by certain strains of E. Coli, lurking in tumors from patients under 40.
The most common source of E. Coli is undercooked ground beef, where bacteria can spread during processing.
But leafy greens like romaine and spinach are another major culprit, often contaminated in the field through tainted water or contact with livestock.
Raw milk and other unpasteurized dairy products also pose a risk, along with raw produce like apples, cucumbers, and especially sprouts — which provide the perfect warm, moist environment for bacteria to thrive.
E. Coli can also sneak in through contaminated water, which may be used to irrigate crops or clean equipment, and poor kitchen hygiene can help it spread to other foods like poultry.
Ludmil Alexandrov, senior study author and professor of cellular and molecular medicine at the University of California San Diego, said: ‘These mutation patterns are a kind of historical record in the genome, and they point to early-life exposure to colibactin as a driving force behind early-onset disease.
‘This reshapes how we think about cancer. It might not be just about what happens in adulthood—cancer could potentially be influenced by events in early life, perhaps even the first few years.
‘Sustained investment in this type of research will be critical in the global effort to prevent and treat cancer before it’s too late.’
The number of under-50s being diagnosed with bowel cancer is increasing worldwide, according to a major global study published last year.
An increase in rates was reported in 27 of the 50 countries examined by US researchers, with the greatest annual increases seen in New Zealand (4 percent), Chile (4 percent) and England (3.6 percent).
According to the latest data, early-onset colon cancer diagnoses in the US are expected to rise by 90 percent in people 20 to 34 years old between 2010 and 2030.
In teens, rates have surged 500 percent since the early 2000s.
The American Cancer Society estimates 154,270 Americans will be diagnosed with colon cancer this year, and 52,900 will die.
In the UK, 44,063 cases are diagnosed per year, and the nation sees 16,808 deaths every year.
The latest study, published Wednesday in the journal Nature, looked at the DNA of 981 colon cancer tumors in patients who were either under 40 or over 70.
Patients were spread across 11 countries, including the US and UK.
They found colibactin leaves behind specific patterns of DNA mutations that were 3.3 times more common in early-onset cases than in those diagnosed after the age of 70.
These mutations were also most common in countries with high rates of early-onset colon cancer, such as the US and UK.
While earlier research has linked colibactin-related mutations to around 10 to 15 percent of all colorectal cancer cases, those studies mostly looked at older patients or didn’t separate early-onset from late-onset disease.
This new study is the first to show that these cancer-driving mutations are significantly more common in younger patients, suggesting a unique link between childhood exposure and early-onset colon cancer.
Dr Marcos Diaz-Gay, first study author and former postdoctoral researcher in Alexandrov’s lab, said: ‘When we started this project, we weren’t planning to focus on early-onset colorectal cancer.
‘Our original goal was to examine global patterns of colorectal cancer to understand why some countries have much higher rates than others. But as we dug into the data, one of the most interesting and striking findings was how frequently colibactin-related mutations appeared in the early-onset cases.’
The team also found colibactin-related mutations start early in colon tumor development, with is consistent with previous research suggesting these mutations occur in the first 10 years of life.
They found colibactin-related mutations account for 15 percent of APC driver mutations, which are some of the earliest genetic alterations directly linked to cancer, in colon cancer.
Alexandrov said: ‘If someone acquires one of these driver mutations by the time they’re 10 years old, they could be decades ahead of schedule for developing colorectal cancer, getting it at age 40 instead of 60.’
Most strands of E. coli are harmless, though six strains produce toxins like colibactin. Toxin-producing strains include siga toxin-producing (STEC), enterotoxigenic (ETEC), enteropathogenic (EPEC), enteroinvasive (EIEC), enteroaggregative (EAEC) and diffusely adherent (DAEC).
Toxin-producing E. coli can cause bloody diarrhea, stomach cramps, vomiting and fever. In severe cases, it can lead to dehydration and hemolytic uremic syndrome, a kidney injury.
The researchers also found despite the notable rises in the US and UK, the researchers found colon cancers in Argentina, Brazil, Colombia, Russia and Thailand were had the largest increases in colibactin-related mutations.
Diaz-Gay said: ‘It’s possible that different countries have different unknown causes. That could open up the potential for targeted, region-specific prevention strategies.’
The researchers plan to investigate how children are being exposed to colibactin-producing bacteria and if medications like probiotics can eliminate harmful strains of bacteria.
The team also plans to look into how environmental exposures later in life can increase the risk of colon cancer.
Alexandrov said: ‘Not every environmental factor or behavior we study leaves a mark on our genome.
‘But we’ve found that colibactin is one of those that can. In this case, its genetic imprint appears to be strongly associated with colorectal cancers in young adults.’