Zhifei Zeng ’23
Diet and nutrition are considered to be key factors in the development of colorectal cancer. Previous experiments have shown that a Western diet—with high intake of red and processed meats, sugar, and refined grains, and low intake of vegetables—can induce systemic and intestinal inflammation. These intestinal inflammations may alter populations of intestinal microorganisms. Many intestinal bacteria have been found to cause colorectal cancer; for example, pks island-carrying E. coli can secrete colibactin that causes mutation in somatic cells. pks island is a pathogenic DNA sequence that can induce DNA double-strand breaks. However, it remains unclear whether the relationship between Western diet and colorectal cancer incidence varies among different gut microbiomes. A research group led by Dr. Shuji Ogino of Harvard University investigated whether the correlation between Western diet and colorectal cancer incidence is influenced by the population of pks+ E. coli (pks island carrying E. coli).
The researchers used survey data from 134,775 participants collected over a 38-year period. Study participants reported dietary information and colorectal cancer diagnoses via questionnaires every 2 years. The researchers also used data from food frequency questionnaires to determine the Western-style diet frequency of participants, and in addition, examined pks+ E. coli levels in samples from participants with colorectal cancer. The Cox proportional hazards model was used to analyze the relationship between Western-style diets and the incidence of various subtypes of colorectal cancer. The researchers found that for colorectal cancer patients with high pks+ E. coli, Western-style diets comprised a large portion of their diet. The researchers then inferred that the Western diet may promote the proliferation and activity of pks+ E. coli or enhance the carcinogenic effect of pks+ E. coli by altering the local tissue microenvironment.
Colorectal cancer is influenced by a variety of factors including diet, lifestyle, and intestinal microorganisms. The study shows that people who regularly consume large amounts of meat and processed foods have a higher risk of pks+ subtype colorectal cancer. This study provides important information for research efforts to modify diet and further understand gut microbiomes in pursuit of cancer prevention strategies.
 K. Arima, et al., Western-style diet, pks island-carrying Escherichia coli, and colorectal cancer: analyses from two large prospective cohort studies. Gastroenterology 4, (2022). doi: doi.org/10.1053/j.gastro.2022.06.054
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