Food bug linked to rise in colon cancers in the young

What’s been causing the sudden upsurge in cases of colon (colorectal) cancer in young people?  Scientists think that getting food poisoning when you’re a child could be a culprit—but they’ve left something unanswered.

They have pinpointed the bacterial toxin, colibactin, which is produced by strains of E.coli, the common cause of food poisoning, as the likely cause.  Long after the food poisoning has passed, colibactin sits in the colon and rectum, and starts to alter DNA.  Young children under the age of 10 could be primed for the cancer that happens years later.

It’s vital for science to understand this sudden surge.  Colorectal cancer is on the rise among young people in at least 27 countries, and rates in the under-50s has roughly doubled every decade for the past 20 years. If current trends continue, colorectal cancer is projected to become the leading cause of cancer-related death among young adults by 2030.

The scientists, from the University of California at San Diego, believe that exposure to colibactin in early childhood imprints a distinct genetic signature on the DNA of colon cells, and increases the risk of developing colorectal cancer before the age of 50.

They analysed 981 colorectal cancer genomes from patients with both early- and late-onset disease across 11 countries and found that colibactin leaves behind specific patterns of DNA mutations that were 3.3 times more common in early-onset cases among the under-40s than in those diagnosed after the age of 70.

But their findings leave many questions unanswered.  How are children being exposed to colibactin-producing bacteria, and what can be done to prevent or mitigate that exposure? Are certain environments, diets or lifestyle behaviours more conducive to colibactin production? How can people find out if they already have these mutations?

And most pressing of all: why are we seeing the alarming rise in cases right now when many of the possible culprits—food poisoning and environment factors for instance—have been around a long time and haven’t had the impact we’re seeing today.

While none of these have been answered, the scientists think that taking probiotics after a bout of food poisoning could mitigate against colibactin’s mutations in the gut.

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