Bacteria May Promote Breast Cancer, Study Finds

Researchers discover how certain pathogenic bacteria can fuel tumor growth and metastasis.

Published on Feb. 18, 2026

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Researchers at the Johns Hopkins Kimmel Cancer Center have discovered that exposure to certain pathogenic bacteria, such as Bacteroides fragilis, Fusobacterium nucleatum, and Escherichia coli, can significantly increase the activity of an enzyme called spermine oxidase (SMOX), leading to DNA damage, tumor growth, and metastasis in breast cancer. The study, published in Cancer Research, reveals a novel link between microbial imbalance and breast cancer, and identifies SMOX as a potential therapeutic target.

Why it matters

This research establishes a direct connection between the presence of specific pathogenic bacteria and the development and progression of breast cancer. By understanding how these bacteria can hijack a key metabolic enzyme to promote cancer, the findings open up new avenues for prevention and treatment, particularly by targeting SMOX activity.

The details

The researchers found that when breast cancer cells or mouse mammary tissue were exposed to the toxin-producing Bacteroides fragilis strain (ETBF) or other pathogenic bacteria like Fusobacterium nucleatum and toxin-producing E. coli, SMOX levels surged. This triggered a self-perpetuating loop of increased oxidative stress, inflammation, and genomic instability that fueled tumor growth and metastasis. Treating breast cancer cells and mouse models with SMOX inhibitors effectively suppressed this bacterial-driven cancer progression.

  • The study was published on February 15, 2026.
  • The research was led by Dipali Sharma, Ph.D., a professor of oncology at the Johns Hopkins Kimmel Cancer Center.

The players

Dipali Sharma

A professor of oncology and a Fetting Fund scholar at the Johns Hopkins Kimmel Cancer Center, who led the research.

Deeptashree Nandi

A postdoctoral fellow working with Sharma and the first author on the study.

Bacteroides fragilis

A strain of pathogenic bacteria that secretes a potent toxin and can remodel bacterial communities to promote cancer.

Fusobacterium nucleatum

A pathogenic bacteria that was found to have similar cancer-promoting effects as Bacteroides fragilis.

Escherichia coli

A pathogenic strain of E. coli that produces a toxin and was also shown to increase SMOX activity and fuel tumor growth.

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What they’re saying

“Microbes don't just reside in our gut. They can directly influence cancer behavior.”

— Dipali Sharma, Professor of Oncology (Cancer Research)

“This establishes a self-perpetuating loop. Inflammatory cytokines stimulate SMOX, SMOX generates oxidative stress, and the resulting DNA damage helps tumors grow and spread.”

— Deeptashree Nandi, Postdoctoral Fellow (Cancer Research)

What’s next

The researchers are now exploring SMOX inhibitors as potential adjuncts to standard breast cancer therapies and investigating how microbe-induced inflammation affects tumor immune responses.

The takeaway

This groundbreaking research reveals a direct link between microbial imbalance and breast cancer development, identifying the enzyme SMOX as a key mediator. By targeting SMOX, the findings suggest new opportunities to disrupt the cancer-promoting effects of pathogenic bacteria and potentially improve outcomes for breast cancer patients.