Microbial Signatures in GI Tumors Linked to Prognosis and Treatment Response

Microbes residing inside gastrointestinal (GI) tumors may help explain why some patients respond differently to treatment or are more prone to metastasis, according to new research. A team from Nankai University in Tianjin, China, has identified core microbial communities that correlate with prognosis across several GI cancers. These findings may inform future tools to stratify risk and improve treatment planning.

Core microbiota found across six cancer types

The study, published in Microbiology Spectrum, analyzed 1,602 tumor samples and 116 adjacent normal tissue samples from public datasets. The researchers identified 15 bacterial genera that were consistently associated with prognosis in six types of GI tumors. This shared microbial signature was found to predict survival outcomes and metastasis risk across the tumor types.

Age-shifting incidence underscores need for new approaches

GI cancers currently account for about half of all new cancer diagnoses worldwide and are responsible for roughly one-third of global cancer deaths. Incidence rates are rising among younger adults, adding urgency to efforts to identify early markers of risk and therapeutic response.

Previous studies have documented that GI tumors harbor diverse microbial communities. Some individual microbial species have been linked to the growth and progression of certain cancers. For example, Escherichia coli has been shown to reduce the effectiveness of treatment in colon cancer, and other species such as Staphylococcus and Lactobacillus have been implicated in metastatic activity in breast cancer.

The new study sought to broaden this perspective by identifying microbial patterns that apply across multiple GI tumor types. According to the researchers, these microbial signatures may function as additional indicators of risk when considered alongside current clinical staging and genetic markers.

Microbiota-based risk score developed

The team found that certain bacteria were associated with either protective or high-risk immune responses. Granulicella, for instance, was associated with reduced levels of CD8+ T cells and a higher likelihood of metastasis. In contrast, Dorea bacteria were linked to a more robust immune response and a lower risk of disease spread.

Using these microbial indicators, the researchers constructed a microbiota-based risk score. This score was able to predict poorer survival and an increased likelihood of metastasis in high-risk patients. It was also found to correlate with differential responses to some immunotherapies.

The score is not intended to replace existing risk assessment tools but may serve as a complementary approach to identify patients who might benefit from different therapeutic strategies, particularly in cases where immunotherapy is less effective.

Next steps

Further research is needed to validate the risk score in prospective clinical studies and to explore the biological mechanisms that underlie the relationships between microbial composition and tumor behavior.

Reference: Liu J, Wei D, Chen Y, Liu X. Intratumoral core microbiota predicts prognosis and therapeutic response in gastrointestinal cancers. Microbiol Spectr. 2025. doi: 10.1128/spectrum.00390-25

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