Blood Test May Help Detect Lung Cancer Using Microbial DNA, Indian Researchers Find

Reported By Akshata Pawar
Mumbai, 20th June 2025: A team of Indian scientists has uncovered a promising way to detect lung cancer by analyzing tiny fragments of microbial DNA in blood, offering hope for a non-invasive cancer diagnosis shortly.

In a groundbreaking study published in Nature Computational Science, researchers from Homi Bhabha National Institute, Tata Memorial Centre, and collaborating institutes explored how microbial traces found in plasma—known as cell-free DNA (cfDNA)—could be used to identify lung cancer. Their approach, known as a “liquid biopsy”, could help replace painful and risky tissue biopsies with a simple blood test.

The study involved 261 blood samples from 50 patients diagnosed with lung cancer. Scientists used two cutting-edge DNA sequencing techniques to analyze the samples:
-Targeted ultra-deep sequencing (10,000× coverage) of cancer-related genes.
-Whole-exome sequencing (WES) captures all protein-coding genes in the human genome.
-Using this genetic data, they screened for microbial DNA signatures—bacteria, viruses, and other tiny organisms—in the blood.

Key Findings
A wide variety of microbes were detected in patients’ blood samples, including Pseudomonas, Toxoplasma, and Streptomyces—some of which are known to be linked with lung infections and immune responses in cancer.

Two computer tools were used to identify microbial DNA: Kraken 2 and IPD2. Kraken 2 found more microbes but was more prone to errors. IPD2 was more accurate due to better filtering of human DNA.

Researchers noted that microbial DNA signatures in blood often matched patterns found in lung tumor tissues, suggesting that blood-based microbial analysis could reflect the tumor’s biological environment.

Importance Of the Study:
Lung cancer is the leading cause of cancer-related deaths globally. Diagnosing it often requires invasive procedures like needle biopsies or scans that may not detect early-stage tumors. This study shows that analyzing non-human DNA in the blood—especially microbial DNA—may provide a faster, safer, and less painful way to detect cancer.

The presence of certain microbes in the bloodstream could even help identify the primary site of cancer in cases where the origin is unknown, called “cancers of unknown primary”, which account for 2–5% of all cancer cases.

The research team emphasizes the need for better data analysis tools and larger clinical studies to confirm these findings. However, the results pave the way for developing cost-effective and accurate liquid biopsy tests that could be widely used in the future.