Imbalance of Gut Microbiota Contributes to the Development of Colorectal Cancer
Thu, September 29, 2022

Imbalance of Gut Microbiota Contributes to the Development of Colorectal Cancer

Colorectal or bowel cancer is the development of cancer from the colon or rectum / Photo Credit: Kateryna Kon via 123rf


An imbalance in gut microbiota, also called dysbiosis, contributes to the pathogenesis of colorectal cancer (CRC). This is according to a new study, which appeared in the multidisciplinary scientific journal Proceedings of the National Academy of Sciences of the United States of America.

Dysbiosis promotes the development of CRC

Gastroenterology researchers from the University Paris-Est Créteil, Henri-Mondor AP-HP Hospital, Institut Pasteur Molecular Microbial Pathogenesis Unit, and research institute Inserm demonstrated their work by transplanting the human fecal flora from patients with colon cancer into germ-free laboratory mice. It was found that the procedure caused lesions and epigenetic alterations, which are characteristics of the onset of a malignant tumor in the body. In biology, epigenetics is the study of heritable phenotype changes that do not involve alterations in the DNA sequence.

Healthy controls vs. CRC patients

The 136 germ-free mice they used were transplanted with either fresh stools from nine patients with no colon disorders (the healthy controls) or fresh stools from nine patients with CRC to advance their understanding and appreciation of the role of colon dysbiosis in the development of CRC. They carried out their procedure at the Hendri-Mondor AP-HP Hospital in Créteil, France.

Seven and 14 weeks after the procedure, the researchers examined the colon of the mice and found the development of aberrant crypt foci (ACF), which are clusters of abnormal tube-like glands in the lining of the rectum and the colon. The group likewise examined the extent of damage to the colon DNA and the microbial profile and took into consideration the blood indicators, weight, and food intake of the animals.

The team’s study led to the creation of a non-invasive blood test, which determines the epigenetic phenomenon linked with gut microbiota imbalance. Research head Professor Iradj Sobhani and team, who operated under the group name Oncomix since April 2016, then validated their study in 1,000 human subjects and 1,000 consecutive colonoscopies. They wrote that when the mice received fresh feces from CRC patients, the animals developed increased tissue, colon epithelial renewals, and blood DNA methylation in the intestinal tissue.


About 1 in 21 men and 1 in 23 women in the US will develop colorectal cancer during their lifetime, acording to the American Cancer Society / Photo Credit: Vasily Gronskiy via 123rf


Sporadic colorectal cancer - how it develops

Sporadic CRC is the term given to patients affected with the disease, but have no family history of such a condition and no risk factors. The researchers added that sporadic CRC is the result of a complex interaction between the environment and the host. An increased incidence of the said condition mirrors the negative environmental developments that trigger changes to the epigenetic and genetic DNA of the host cells, thus, promoting the development of sporadic CRC. 

Their findings may be used to determine the adherence to and effectiveness of probiotics and prebiotic therapies.

Before Oncomix’s study, other studies investigated the role of microbiota in the interactions between the environment and the individuals that result in sporadic CRC. A microbiota includes the millions of tiny living organisms and bacteria in the body. 

Microbiome, advancing the research field in the study of human cancers

In a 2018 study about dysbiosis of the gut microbiota and CRC, Keisuke Kosumi from the Dana-Farber Cancer Institute Department of Oncologic Pathology and group pointed out how the microbiome has helped advance the research field in the study of human cancers. They believe that dysbiosis of the gut microbiota is linked with other disorders, including inflammatory bowel diseases, diabetes, obesity, and other cancer types, especially CRC.



Cancer: statistics

Our World in Data, a platform that provides data and research on global problems, shared that colon and rectal cancer has the second-highest number of deaths annually from cancer across all ages and both sexes. In the list of the deadliest cancers in the world in 2017, tracheal, bronchus, and lung cancer ranked first with 1.88 million deaths worldwide. Second is colon and rectum cancer with 896,040 deaths, followed by stomach cancer with 864,989 deaths annually. 

Other types of cancers recorded in 2017 were: liver cancer with 819,435 deaths, breast cancer with 611,625 deaths, pancreatic cancer with 441,083 deaths, esophageal cancer with 435,959 deaths, prostate cancer with 415,910 deaths, leukemia with 347,583 deaths, cervical cancer with 259,671, brain and nervous system cancer with 247,143 deaths, bladder cancer with 196,546 deaths, lip and oral cavity cancer with 193,696 deaths, ovarian cancer with 175,982 deaths, gallbladder and biliary tract cancer with 173,974 deaths, kidney cancer with 138,526 deaths, and larynx cancer with 126,471 deaths.

In 2018, oncologist-approved cancer information platform Cancer.Net shared that survival rates for colon cancer and rectal cancer are separate. For colon cancer, the overall 5-year survival rate is 64 percent, but if the cancer was diagnosed at a localized stage, it would be a 90 percent survival rate. For rectal cancer, the overall 5-year survival rate is 67 percent, but if diagnosed at a localized stage, it would be an 89 percent survival rate.



While there’s no sure way to prevent CRC, the recent findings by Professor Sobhani and colleagues show how the public can protect their colorectal health or lower their risk. It also points out how changes in the gut microbiota may serve as biomarkers for cancer screening before the condition turns into cancer.