Determining whether a tumor began in its current location or spread from another organ is crucial for diagnosis and treatment. However, when the primary tumor cannot be identified, doctors face challenges in selecting the best treatment approach.
UC San Diego Researchers Discover Microbial DNA Marker
Researchers at the University of California San Diego have now identified a microbial DNA signature in blood plasma that reliably distinguishes primary liver cancer from colorectal cancer that has metastasized to the liver. Their findings were recently published in eGastroenterology.
“The use of microbial DNA signatures could open up a new diagnostic pathway, especially in situations where radiographic imaging is ambiguous or not accessible,” said Amir Zarrinpar, MD, Ph.D., professor of Gastroenterology & Hepatology at UC San Diego School of Medicine.
Study Design and Methodology
As reported by medicalxpress, the research team isolated cell-free DNA (cfDNA)—fragments shed by dead cells into bodily fluids—from the blood plasma of 16 patients with primary liver cancer and 11 patients with metastatic colorectal cancer. They then conducted a metagenomic analysis to identify distinct microbial patterns.
Key Findings
The microbial cfDNA classifier demonstrated 90% accuracy in distinguishing between the two cancers.
- Primary liver cancer patients had higher levels of:
- Pseudomonas aeruginosa
- Corynebacterium accolens
- Corynebacterium glucuronolyticum
- Metastatic colorectal cancer patients had higher levels of:
- Acinetobacter tandoii
- Acinetobacter tianfuensis
- Acinetobacter septicus
- Acinetobacter parvus
- Pseudomonas asiatica
- Bifidobacterium faecale
Microbes associated with primary liver cancer are often linked to immunocompromised patients, liver transplant complications, and antimicrobial defense, while microbes in metastatic colorectal cancer patients are linked to hospital-acquired infections, bloodstream infections, and gastrointestinal inflammation.
Significance of the Research
“This is one of the first studies to show that microbial DNA in blood may be used to noninvasively distinguish tumor origin without the use of machine learning or artificial intelligence, particularly between two common liver pathologies,” Zarrinpar noted.
Potential Clinical Applications
The findings strengthen evidence of microbial involvement in cancer biology. If validated in larger studies, this approach could:
- Improve early cancer detection
- Aid in monitoring high-risk patients
- Support the development of microbial DNA-based biomarkers
- Pave the way for microbiome-based cancer therapies
By using microbial signatures, clinicians may soon have a powerful, noninvasive tool to determine tumor origin and tailor treatments more effectively.