Singapore's A*STAR Genome Institute of Singapore (GIS) has taken a leading role in addressing a critical challenge in cancer research. In a perspective piece published in the prestigious journal Nature Cancer on February 19, 2026, an international team led by Associate Professor Niranjan Nagarajan from A*STAR GIS and the National University of Singapore (NUS) Yong Loo Lin School of Medicine urges the scientific community to adopt stronger standards for studying the tumor microbiome. This call comes amid growing concerns that many reported microbial presences in human tumors may be artifacts of contamination or analytical errors, leading to false discoveries that could mislead future research and therapeutic development.
The tumor microbiome refers to the community of bacteria, fungi, viruses, and other microorganisms residing within cancerous tissues. Over the past decade, sequencing technologies have revealed intriguing microbial signatures in tumors across various cancer types, sparking hopes that these microbes could influence tumor growth, metastasis, immune evasion, or responses to therapies like immunotherapy. However, the low biomass nature of these microbial communities—often dwarfed by the host's own DNA—makes detection prone to errors. Contaminants from lab reagents, sample handling, or even outdated reference databases can produce misleading signals, as highlighted by recent retractions and critiques in the field.
This publication, titled "Setting higher standards for reports of microbial species in human cancers," co-authored by GIS Fellow Dr. Minghao Chia and experts from Johns Hopkins University, the University of Western Australia, Leiden University Medical Center, Dana-Farber Cancer Institute, University of Copenhagen, and others, provides a comprehensive roadmap to enhance rigor. By drawing parallels to the ancient DNA field, which overcame similar contamination pitfalls through stringent protocols, the authors emphasize the need for systematic quality controls to distinguish true tumor-resident microbes from spurious ones.
🌡️ The Rise and Pitfalls of Tumor Microbiome Research
The excitement around the tumor microbiome began with landmark studies sequencing tumor tissues and identifying distinct microbial profiles associated with specific cancers. For instance, certain bacteria have been linked to colorectal cancer progression, while fungal signatures appear enriched in pancreatic tumors. These findings suggest microbes could serve as diagnostic biomarkers, prognostic indicators, or even therapeutic targets—potentially explaining why some immunotherapies succeed in 'hot' tumors rich in immune-modulating microbes.
Yet, skepticism has mounted. High-profile re-analyses, such as a 2023 bioRxiv preprint critiquing a large-scale pan-cancer study, revealed that many microbial correlations were likely false positives driven by bioinformatics artifacts. Human DNA fragments were misclassified as microbial due to incomplete reference genomes contaminated with human sequences. Similarly, environmental contaminants like skin bacteria or lab reagents introduce signals indistinguishable from true tumor residents without proper controls.
In Singapore, where precision medicine initiatives like the National Precision Medicine (NPM) program generate vast genomic datasets, such issues are particularly relevant. A*STAR GIS, with its expertise in computational genomics and metagenomics, has been at the forefront of developing tools to deconvolute host-microbe signals accurately. Assoc Prof Nagarajan notes, “Not all microbes reported in tumours are real residents. Some could be the result of contamination or errors in data analysis.” This perspective underscores the urgency for standardized practices to salvage the field's credibility.
Key Challenges Identified in Current Practices
The paper systematically dissects four major hurdles: sample handling, internal controls, bioinformatics pipelines, and validation methods.
- Sample Handling Contamination: Tumors from internal organs like the brain or pancreas are expected to be microbe-poor due to immune surveillance. Yet, studies report abundant microbes there. Nucleic acids can infiltrate during surgery, storage, or processing—much like ancient DNA contamination from modern handlers.
- Lack of Controls: Few studies include negative controls (e.g., blank extraction kits, adjacent non-tumor tissue) or replicate across labs, failing to flag batch effects or kitome (microbes in reagents).
- Bioinformatics Pitfalls: Relying solely on microbial databases ignores human DNA chimerism. Low-quality genomes cause read misalignments; without host depletion or stringent filtering, false positives abound.
- Insufficient Validation: Bioinformatics alone cannot confirm viability or localization. Spatial techniques like fluorescence in situ hybridization (FISH) or immunohistochemistry (IHC) for microbial markers (e.g., LPS for Gram-negatives) are rarely used.
Dr. Minghao Chia likens it to a contaminated crime scene: “By adopting more rigorous standards and confirming results with multiple approaches, scientists can avoid false discoveries and focus on real connections between microbes and cancer.” In Singapore's humid climate and advanced labs, adopting cleanroom protocols or BSL-2 facilities could mitigate these risks effectively.
The Proposed Checklist: A 26-Point Roadmap to Reliability
Central to the publication is a comprehensive 26-item checklist (Table 1 in the paper), adapted from ancient DNA standards, tailored for tumor microbiomes. It spans the entire workflow:
- Acquisition (Q1-5): Aseptic techniques, multiple controls per batch (e.g., >1 sampling control per environment).
- Processing (Q6-12): Clean/BSL-2 labs, UV irradiation, independent replication.
- Sequencing (Q13-18): Negative controls per batch, host depletion, high-depth coverage.
- Bioinformatics (Q19-25): Host-inclusive databases, contaminant subtraction, read alignment QC, environmental filtering.
- Reporting (Q26): Transparent limitations, raw data deposition.
Validation demands orthogonal methods: RT-qPCR for abundance, culture for viability, and spatial IHC/FISH for localization. The authors stress multi-line evidence, cautioning that microbial DNA alone proves neither community nor causality. For Singapore researchers, this aligns with GIS's metagenomic pipelines, already used in NPM for precise host-microbe separation.
Adopting this checklist could standardize the field, much like MIAME for microarrays revolutionized genomics. Early adopters, including GIS, demonstrate its feasibility without excessive cost.
Singapore's Leadership in Computational Genomics and Microbiome Research
A*STAR GIS, established in 2003, pioneers computational biology for Singapore's biomedical ecosystem. Assoc Prof Nagarajan's group excels in metagenomics, developing tools like GEMINI for decontaminating blood microbiomes. Collaborations with NUS and NTU position Singapore as a hub for precision oncology.
The paper's international authorship reflects GIS's global reach: Steven Salzberg (Johns Hopkins, bioinformatics pioneer), Barry Marshall (Nobel laureate, H. pylori discoverer), and others. Singapore's investment in AI-compute at GIS enables re-analysis of public datasets, exposing field-wide issues.
Locally, this bolsters initiatives like the Cancer Science Institute of Singapore (CSI) at NUS, integrating microbiome data into multi-omics cancer atlases. For aspiring researchers, opportunities abound in computational biology roles at GIS and universities.
Implications for Global Cancer Research and Precision Medicine
False tumor microbiome discoveries divert resources from genuine leads, like microbe-modulated immunotherapy responses. Rigorous standards could validate biomarkers for early detection or predict drug resistance, accelerating Singapore's Smart Nation precision medicine goals.
In colorectal cancer, validated Fusobacterium nucleatum enrichment informs screening; similar rigor might unlock brain tumor insights. The checklist prevents 'kitome' biases, ensuring reproducible findings across cohorts.
Stakeholders—from funders like NRF to clinicians—must prioritize these standards. Transparent reporting via public repositories fosters collaboration, benefiting Singapore's NPM with 100,000+ genomes.
Read the full Nature Cancer perspective for the checklist.Expert Perspectives and Stakeholder Views
Barry Marshall praises the framework: “Validating microbes requires multiple evidence lines, as with H. pylori.” Salzberg, a sequencing skeptic, stresses bioinformatics conservatism.
Singapore oncologists welcome it, noting immunotherapy variability. GIS's track record—e.g., debunking blood microbiomes—builds trust. Challenges include cost for small labs, but open-source tools mitigate this.
Future studies must address causality: do microbes drive cancer or vice versa? Longitudinal sampling and functional assays are next.
Singapore's Thriving Microbiome Research Ecosystem
Beyond GIS, NUS's Mechanobiology Institute and NTU's Lee Kong Chian School of Medicine advance host-microbe interactions. A*STAR's SIgN explores immune-microbiome crosstalk.
Government support via RIE2025 funds AI-metagenomics. Collaborations with global leaders position Singapore for breakthroughs, attracting talent via postdoc positions.
Students can pursue microbiome PhDs at NUS, gaining skills in NGS analysis—vital for careers in biotech. Explore academic CV tips for applications.
Future Outlook: From Standards to Discoveries
Implementing these standards promises a mature field, uncovering true tumor-microbe roles. Spatial multi-omics, single-cell sequencing, and AI validation will dominate.
In Singapore, this supports Cancer 2030 goals, potentially yielding diagnostics. Researchers should audit pipelines against the checklist, prioritizing controls.
For higher ed, it highlights computational biology's rise—enroll in NUS GIS programs for hands-on training. Check Singapore academic opportunities.
Career Insights and Actionable Advice for Aspiring Researchers
This publication spotlights demand for metagenomics experts. GIS hires computational biologists; NUS offers fellowships. Key skills: R/BioPython, Kraken2/MetaPhlAn, QC visualization.
- Master aseptic techniques via lab courses.
- Practice with public TCGA data, applying checklist.
- Collaborate internationally for replication.
- Publish with full methods transparency.
Visit research assistant jobs or Rate My Professor for mentors. Singapore's ecosystem offers PhD stipends, postdocs at S$5,000+/month.
In conclusion, A*STAR GIS's Nature Cancer perspective is a pivotal step toward trustworthy tumor microbiome science. By embracing the checklist, researchers worldwide—and especially in Singapore's vibrant academic scene—can sidestep pitfalls, unlocking microbes' true cancer roles. This not only advances knowledge but paves the way for innovative diagnostics and therapies. Stay informed via higher education news, explore higher ed jobs, university jobs, and career advice to join this frontier.
