Intratumoural microbiota—the microbial populations residing within solid tumours—have emerged as pivotal components of the tumour microenvironment (TME), influencing tumour initiation, progression, and therapeutic outcomes.

In a comprehensive review published in Med Research, researchers from Southern Medical University and collaborating institutions systematically examine the heterogeneity of these microorganisms and their multifaceted roles in cancer biology.

The authors categorise microbial heterogeneity at three distinct levels: among different tumour types, within individual tumours, and between tumours and adjacent non-tumorous tissues.

Tumours such as colorectal, breast, gastric, and pancreatic cancers exhibit distinct microbial profiles, with notable diversity in both species composition and spatial localisation.

These microbial communities may be shaped by tumour subtype, anatomical location, stage of progression, or patient-specific factors such as age, diet, or comorbidities.

Functionally, the intratumoural microbiota exert a broad spectrum of effects on the TME, ranging from immunostimulatory to immunosuppressive and from antitumor to protumor.

Some microbes enhance immune surveillance and cytotoxic T cell responses, while others promote immune evasion, stromal remodelling, and metabolic reprogramming.

The review also discusses how microbial metabolites and signalling pathways interface with host immune regulation and tumour cell behaviour, highlighting both supportive and inhibitory roles in cancer progression.

Importantly, the authors emphasise that these functional effects are context-dependent and may vary across tumour types and clinical settings.

Beyond mechanistic insights, the review underscores the methodological challenges of characterising intratumoural microbiota, particularly in distinguishing live microbes from microbial fragments and contaminants.

To address this, the authors advocate for the integration of advanced technologies—such as single-cell and spatial transcriptomics, metagenomics, and high-resolution imaging—to refine our understanding of microbial localisation, viability, and host–microbe interactions at the microscale.

By summarising emerging evidence across diverse tumour types, this work provides a conceptual framework for interpreting intratumoural microbiota as active participants in tumour biology.

It also lays the groundwork for future investigations into microbiota-informed diagnostic strategies and therapeutic interventions in precision oncology.

Source: FAR Publishing Limited