Colorectal cancer is the fourth most common cancer in the UK and the second leading cause of cancer-related death. The new findings may help clinicians better understand how the disease develops, how aggressive it may become, and how patients might respond to different treatments.

The team analyzed whole genome sequencing (WGS) data from more than 9,000 cancer patients. Their results, published in Science Translational Medicine, also challenge a widely held assumption that every cancer type has its own unique microbial signature.

"This study changes how we think about the role of microbes in cancer," said lead researcher Dr. Abraham Gihawi, from UEA's Norwich Medical School.

How scientists analyzed tumor microbes

To carry out the study, researchers examined Genomics England DNA sequence data from 11,735 cancer samples spanning 22 different cancer types.

"When you collect cancer DNA sequences, you also gain information from the DNA of microbes contained within the samples," said Dr. Gihawi.

"We wanted to determine the precise DNA composition of microbes present in each sample. So, we developed computer programs to remove human DNA and analyse the remaining microbe DNA.

"We then correlated this information with clinical data from the patients about their cancer type and clinical outcome.

"What we found challenges previous claims that each cancer type has a distinct microbiological signature or fingerprint.

"But importantly, as whole genome sequencing becomes more common in hospitals, we show that looking at the microbes in tumor samples could become a powerful tool for improving cancer care at little extra cost.

Colorectal cancer shows a distinct microbial signature

The analysis revealed a clear pattern. Among all cancers studied, only colorectal tumors consistently showed a unique and identifiable microbial community.

"Our results show that only colorectal tumors possess distinctly identifiable microbial communities.

"We found that these microbial signatures were so specific that they could accurately distinguish colorectal tumors from other tumors. We hope that this could help doctors diagnose the disease more precisely and researchers to study the microbes found in colorectal cancer."

The study also points to broader clinical uses. In oral cancers, researchers found that certain viruses such as HPV (human papillomavirus) could be detected more accurately than with some current diagnostic tests.

They also identified rare but dangerous viruses, including Human T-Lymphotropic Virus-1 (HTLV-1), which can remain dormant in the body and later contribute to cancer development.

Microbes linked to survival and treatment response

The findings suggest that microbes may do more than simply exist alongside cancer. In some cases, they appear to be linked to how patients fare.

"We found that certain types of bacteria were associated with poorer survival rates in some cases of sarcoma. This might lead to additional research and treatment options for these types of cancer," said Dr. Gihawi.

"One of the most exciting things we found was that in some sarcoma cases, the presence of specific bacteria was linked to better survival rates.

"This suggests that microbes might one day help doctors predict how well a patient will respond to treatment and open up new approaches to treatment," he added.

Whole genome sequencing as a clinical tool

Experts say the work highlights the growing importance of genome sequencing in modern medicine.

Prof Daniel Brewer, from UEA's Norwich Medical School, said: "This study highlights the growing clinical value of whole genome sequencing in identifying pathogenic organisms such as HTLV-1 and papillomavirus, which may otherwise go undetected.

"By revealing these hidden infections and providing insight into cancer prognosis -- particularly in sarcomas -- it demonstrates how genomic analysis is becoming an indispensable tool in precision medicine.

"The findings also suggest that oral cancer, in some cases, may be a close diagnostic consideration, further emphasizing the importance of comprehensive genomic profiling in clinical decision-making."

Collaboration and funding

The project was led by UEA and involved researchers from multiple institutions, including the University of Leeds, the Quadram Institute, Oxford Nanopore Technologies, the Institute of Cancer Research, London, the University of Manchester, National Institute for Health and Care Research (NIHR) Manchester Biomedical Research Centre, the University of Athens (Greece) the University of Liverpool, Cambridge University Hospitals NHS Foundation Trust, University College London, the University of Southampton, the University of North Carolina (US) and the Earlham Institute.

Funding for the study was provided by the Big C Cancer Charity and Prostate Cancer UK.