Specific strains of bacteria in the gut are significantly associated with colorectal cancer, according to a new study by researchers at The University of Texas Health Science Center at Houston (UTHealth) School of Public Health. The study, which also identified a less invasive and less expensive way to screen for colorectal cancer, was recently published in the journal Gut.
Colorectal cancer is the second leading cause of cancer-associated death in the U.S., according to the American Cancer Society. Previous studies have found associations between gut bacteria and colorectal cancer, but this is the first to link several studies to identify specific strains and species that are associated with the disease: Parvimonas micra ATCC 33270, Streptococcus anginosus and multiple members of the phylum proteobacteria.
First author Manasi Shah, Ph.D., examined the raw data from nine previous studies of colorectal cancer and the gut. The study cohorts were ethnically diverse, recruited between 2012 and 2016 and the scientists conducting each study used non-uniform laboratory methods. Despite these challenges, Shah established that across the cohorts, specific bacteria were frequently and significantly found in stool samples from patients with colorectal cancer.
"Although previous studies have found associations between the gut microbiome and colorectal cancer, there was little agreement between the results. To our knowledge, our study is the first attempt to gather existing microbial marker gene data and reprocess it uniformly. Despite differences in cohort demographics, laboratory protocols and downstream analysis, which are known to influence microbiome outcomes, it is encouraging that we found bacterial signals that are consistently and significantly associated with colorectal cancer," said Shah, who completed the research while she was a doctoral student at UTHealth School of Public Health.
Identifying the bacteria that could serve as biomarkers for the disease is a new method that could be used to screen for colorectal cancer using stool samples, Shah said. This new approach could be less invasive and less expensive than a colonoscopy, which is the most commonly used screening method.
"Microbiome studies offer tremendous potential for advancing diagnostics and therapeutics. For some diseases and conditions, identifying microbiome-based associations has been relatively simple. For the majority, however, the research community is still sifting through a lot of data and a lot of noise as we seek to understand how the microbiome contributes to disease onset, progression and our ability to provide rapid, accurate diagnoses," said Emily Hollister, Ph.D., senior author and assistant professor of pathology and immunology at Baylor College of Medicine. "The identification of consistent patterns across studies of the colorectal cancer-associated microbiome represents a big step forward in these efforts."
Microbial markers by themselves could accurately detect colorectal cancer 80 percent of the time. For a subset of the data, when combined with a home-based diagnostic fecal occult to test for blood in the stool, as well as a patient's age and gender, the new biomarker method could accurately detect colorectal cancer 91 percent of the time.
"In order to discover improved biomarkers and therapeutics based on the microbiome, you must have a strain-focused computational platform able to detect changes in abundance as a disease progresses," said Todd DeSantis, co-author and vice president of informatics at Second Genome. "This study demonstrated that our platform was unique in that it enabled the identification of important microbiome-based biomarkers."