The Centers for Disease Control and Prevention (CDC) deem colorectal cancer the third most common type of cancer to be diagnosed, as well as the second most common cause of cancer-related mortality in the United States.
And, according to data from the National Cancer Institute (NCI), there were an estimated 135,430 new cases of colorectal cancer in 2017.
Survival rates following treatment for this type of cancer are generally encouraging; 64.9 percent of patients have a long-term survival rate.
However, in the more advanced stages of the disease, the outcomes following treatment are less optimistic, and the likelihood of tumor recurrence also increases.
Now, Dr. Chun-Loong Ho, Prof. Matthew Chang, and colleagues, from the Yong Loo Lin School of Medicine at the National University of Singapore in Clementi, are investigating new ways to treat colorectal cancer and to prevent its recurrence.
The researchers have started experimenting with a mix of engineered probiotics and substances derived from cruciferous vegetables — such as broccoli, cauliflower, and Brussels sprouts — to, ultimately, devise an effective anti-cancer "cocktail" from readily available ingredients.
Their results were reported earlier this week in the journal Nature Biomedical Engineering.
At the core, a genetically engineered microbe
Dr. Ho and his colleagues focused on Escherichia coli Nissle, which is a non-pathogenic (meaning non-disease-causing) microbe. They genetically engineered this E. coli strain into a probiotic that would be able to bind to a protein found in colorectal cancer cells. Thus, an enzyme called myrosinase would be produced.
Myrosinase can then be used to convert glucosinolate, which is a component found in cruciferous vegetables, into a by-product called sulphoraphane, which, researchers have shown, can have a protective effect against cancer cells.
Dr. Ho and colleagues were hoping that the sulphoraphane thus produced would interact with the cancer cells surrounding it and annihilate them.
Since regular, non-cancerous cells cannot convert glucosinolates — and since they are not affected by sulphoraphane — the researchers believed that only colorectal cancer cells would be targeted by the substance.
In vitro, as well as in vivo, experiments confirmed Dr. Ho and colleagues' hypothesis. Adding the engineered E. coli together with either broccoli extract or a solution of glucosinolates to a petri dish containing colorectal cancer cells resulted in the suppression of more than 95 percent of these cells.
This was true for colorectal cancer cells sourced from both human and mice tumors, as well as for colorectal cancer cell lines produced in the laboratory.
But experiments on other types of cancer cell — including breast and stomach cancer — showed that the experimental cocktail had no perceivable impact on cancers other than colorectal.
'Mothers are right after all'
When tested on mice with colon cancer tumors, the experimental mix was seen to decrease the number of tumors by 75 percent.
The researchers also note that the remaining tumors had diminished in size — they were three times smaller than those detected in the animals' control counterparts, which had not been administered the probiotic and cruciferous veg combination.
Dr. Ho and colleagues hope that the newly engineered probiotics, used alongside the substance extracted from broccoli, could play a double role in the fight against colon cancer.
For one, the new mix might help to prevent colorectal cancer tumors from forming. Then, it could be useful in killing any remaining cancer cells in the aftermath of treatment or surgery, thus also reducing the chance of tumor recurrence.
"One exciting aspect of our strategy is that it just capitalizes on our lifestyle, potentially transforming our normal diet into a sustainable, low-cost therapeutic regimen. We hope that our strategy can be a useful complement to current cancer therapies."
Prof. Matthew Chang
In a more lighthearted vein, as Dr. Ho puts it, the current study's findings emphasize that "[m]others are right after all, eating vegetables is important."