Triple-negative breast cancer gets its name from what it does not have: the estrogen receptor, the progesterone receptor, and excess HER2 protein. Because none of these three drivers are present, the standard hormonal therapies and HER2-directed antibodies that transformed outcomes for many breast cancer patients simply do not work. Treatment therefore relies heavily on chemotherapy, and when tumors evolve resistance to those drugs, options narrow dramatically. It is precisely this critical gap in the treatment landscape that the new research program is designed to address, using Salmonella bacteria that have been genetically tamed and reprogrammed to serve as delivery vehicles and therapeutic agents in their own right.

The idea of using bacteria against cancer is not entirely new to science. Certain bacterial species, including Salmonella, have a natural affinity for tumors: they colonize the hostile, oxygen-poor cores of solid tumors where many conventional therapies struggle to penetrate, and they can be engineered to be nontoxic while retaining this tumor-homing behavior. What the new grant makes possible is a systematic, multi-pronged effort to turn that biological quirk into a suite of clinical tools, with the team designing nontoxic Salmonella strains capable of delivering three distinct treatment options against drug-resistant disease.

Dr. Cheal, an assistant professor of biological chemistry in radiology at Weill Cornell Medicine and a member of the Sandra and Edward Meyer Cancer Center, will receive $2.7 million of the funding to adapt the Salmonella delivery system for radiopharmaceutical therapy, often abbreviated RPT. Radiopharmaceutical therapy is one of the most elegant concepts in modern cancer medicine: rather than bathing the body in external radiation beams, it delivers radioactive metals directly to tumor cells, concentrating the cancer-killing dose at the disease site while sparing healthy tissue, which translates into far less toxicity than traditional radiation. The catch has always been delivery. The radioactive metals themselves cannot distinguish tumor from healthy tissue, and getting them to find the cancer has been the field’s central challenge.

This is where the bacteria come in, and the logic is delightfully counterintuitive. The Salmonella cannot physically carry the radioactive metals, but they can carry substances that attract them. In effect, the engineered bacteria seed themselves within the tumor and then raise a molecular flag, creating a homing beacon that draws the cancer-killing radioactivity to exactly where it is needed. The bacteria act as an address label for the lethal payload, converting a delivery problem that has limited radiopharmaceutical therapy into a two-step targeting strategy that exploits the bacteria’s own tumor-seeking instincts.

The same beacon strategy has a second life beyond treatment. The researchers will design their Salmonella to carry metals that emit a non-damaging form of beta radiation known as positrons, the signature signal detected by positron emission tomography, or PET, scanning. In practical terms, the bacterial colonies inside a tumor could light up on a PET image, giving physicians a real-time, noninvasive view of where the therapy vehicles have settled and how much of the tumor they have colonized. A single engineered platform that can both guide therapy and report on its own location represents exactly the kind of dual-purpose tool that imaging scientists have been pursuing for years.

The grant funds several complementary efforts beyond the radiopharmaceutical work, reflecting the breadth of the collaboration. In one arm, the team will use genetically engineered bacteria to decorate the surface of cancer cells with a protein derived from the virus that causes COVID-19. The goal is immunological sleight of hand: by stamping a familiar viral marker onto tumors that the immune system would otherwise ignore or tolerate, the approach essentially tricks the immune system into recognizing the cancer as infected tissue and mounting an attack against it, harnessing the potent memory and specificity of antiviral immunity for an entirely different target.

Another line of research builds on the team’s previous work combining bacteria and viruses to fight cancer in a new way. Instead of delivering drugs, the Salmonella will ferry cancer-killing viruses directly into tumors, unleashing them where they can infect and destroy malignant cells. The strategy is aimed squarely at the problem of resistance: tumors are remarkably adept at evolving defenses against any single drug, but a viral assault delivered from within the tumor microenvironment presents a fundamentally different challenge that resistant cells may not be equipped to survive. Alongside these therapeutic arms, the program will create a massive library of Salmonella genetics, a resource intended to enable the precise tailoring of the bacteria as vehicles for different therapies, and will refine light-emitting molecules that allow researchers to watch, in real time, how immune cells behave in response to the various Salmonella-based treatments.

Behind the science stands a deep bench of collaborators. Dr. Cheal is working with UMass Amherst investigators Dr. Neil Forbes, a professor of chemical and biomolecular engineering; Dr. Lisa M. Minter, a professor of veterinary and animal sciences; Dr. Lauren Andrews, an associate professor of chemical and biomolecular engineering; Dr. Ashish Kulkarni, a professor of chemical and biomolecular engineering; and Dr. Joseph Jerry, a professor emeritus of veterinary and animal sciences. The pairing of a radiopharmaceutical specialist at a major cancer center with a team of bacterial engineers and immunologists at a flagship public research university reflects how modern cancer research increasingly crosses disciplinary and institutional boundaries, pooling expertise in microbiology, immunology, radiochemistry, and tumor biology around a single engineered platform.

For patients with triple-negative breast cancer that has stopped responding to chemotherapy, the stakes of this work could hardly be higher, and the NIH’s decision to fund bacterial cancer therapies at this scale signals a growing institutional confidence that engineered microbes are ready to move from promising curiosities toward serious therapeutic candidates. Much work remains between the laboratory and the clinic, and the five-year timeline of the grant reflects the deliberate pace of turning nontoxic bacterial strains into reliable medical tools. But the vision animating the program is clear: bacteria that home in on tumors, flag them for radioactive destruction, illuminate themselves for imaging, disguise them for the immune system, and smuggle in cancer-killing viruses, all built from the same programmable biological chassis. If the team succeeds, one of medicine’s oldest enemies, the pathogenic bacterium, may be rewritten into one of its most versatile allies against one of its most difficult cancers.

Subject of Research: Engineered Salmonella bacteria as delivery vehicles for radiopharmaceutical, viral, and immune-based therapies against drug-resistant triple-negative breast cancer

Article Title: NIH grant awarded to treat breast cancer with bacteria

Article References: NIH grant awarded to treat breast cancer with bacteria. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: Salmonella, triple-negative breast cancer, radiopharmaceutical therapy, NIH grant, bacterial cancer therapy, PET imaging, immunotherapy, oncolytic viruses, Weill Cornell Medicine, UMass Amherst, drug resistance, genetic engineering

The appeal of bacteria as anti-cancer agents rests on a quirk of tumor physiology. Solid tumors are riddled with regions of hypoxia, necrosis, and poor perfusion — conditions that starve conventional chemotherapies of access but that many anaerobic and facultative anaerobic bacteria actively seek out. Once there, engineered strains can colonize selectively, produce therapeutic payloads in situ, remodel the tumor microenvironment, and recruit the immune system against the malignancy. This is a capability no small molecule or antibody can replicate: a living factory that navigates to its target, senses its surroundings, and manufactures its drug on site.

The review organizes the genetic control layer around three classes of regulatory circuits. Hypoxia-responsive promoters switch payload expression on only in the oxygen-poor depths of a tumor, sparing healthy, well-oxygenated tissue. Quorum-sensing circuits tie gene expression to bacterial population density, so that therapeutic output scales with the degree of colonization rather than with the administered dose alone. Externally responsive systems, meanwhile, give clinicians an external handle — for example, near-infrared light or high-intensity focused ultrasound can trigger payload release at a chosen time and place, converting an autonomous microbe into a remotely controllable device. Together, these gating strategies address one of the field’s oldest problems: keeping a potent payload silent until the bacterium has arrived where it is needed.

But the authors are careful to emphasize that bacterial activity cuts both ways. Engineered microbes act on four compartments of the tumor at once — malignant cells, stromal cells, immune cells, and the resident microbiome — and every one of those interactions can be therapeutic or counterproductive. A strain that lyses tumor cells may also provoke inflammatory toxicity; a payload that converts a prodrug such as 5-fluorocytosine into the cytotoxic 5-fluorouracil locally may leak into circulation; a bacterium that activates antitumor immunity may also, in some contexts, recruit immunosuppressive cells. The review’s framework therefore insists that designers map these effects explicitly rather than assume that colonization equals benefit.

The clinical record to date is instructive precisely because it is mixed. Attenuated Salmonella strains have been tested intravenously and shown the ability to seed tumors, but heterogeneous colonization and dose-limiting toxicity have constrained their use. Clostridium spores exploit the anaerobic necrotic core of tumors but leave the oxygenated rim untouched, which is why combination strategies with radiotherapy or chemotherapy have been explored. Listeria-based platforms have been pursued for their potent ability to stimulate cell-mediated immunity, while Bifidobacterium offers an inherently safe, non-pathogenic chassis for payload delivery. E. coli Nissle 1917, a probiotic strain with a long safety history, has emerged as a particularly versatile chassis, and intratumoral injection — as in the approved use of Bacille Calmette–Guérin for non-muscle-invasive bladder cancer — demonstrates that local bacterial therapy can already be standard of care when the indication is chosen correctly.

From these experiences, the authors extract a set of design rules that read like a checklist for the next generation of trials. Route selection matters: intravenous delivery demands strains that survive blood-borne clearance, while intratumoral delivery trades systemic reach for control and tolerability. Quantitative colonization assessment — measuring colony-forming units or imaging bacterial presence — must replace anecdotal evidence that a strain has homed to the tumor. Payload gating must be tight enough that measurable bacterial products appear only where intended. Treatment sequencing must consider how bacteria interact with checkpoint inhibitors, chemotherapy, and radiotherapy, since the immune context created by one modality can determine whether the next succeeds. Rescue planning — antibiotics, in effect a kill switch at the level of the whole patient — must be defined before dosing begins. And indication choice should favor tumors whose ecology is permissive: hypoxic, immunologically accessible, and anatomically reachable.

The review also positions bacterial platforms alongside oncolytic viruses, the other major class of living therapeutics, arguing that the two are complementary rather than competing. Oncolytic viruses such as talimogene laherparepvec are optimized for direct tumor lysis and antigen release, while bacteria offer larger payload capacity, deeper penetration into hypoxic and necrotic regions that viruses find hostile, and a distinct immunostimulatory profile driven by pathogen-associated molecular patterns engaging Toll-like receptors. A rational combination might use a virus to inflame the tumor and a bacterium to colonize its necrotic core and sustain payload production — a sequencing question the framework explicitly addresses.

Manufacturing and pharmacology emerge as the quiet determinants of whether any of this reaches patients. Living products resist the standard chemistry, manufacturing, and controls logic of the pharmaceutical industry: batch-to-batch consistency, stability, and product release testing all become harder when the drug is alive and dividing. The authors stress that reproducible development strategies, good manufacturing practice frameworks adapted to living organisms, and honest pharmacodynamic modeling — how many bacteria arrive, how long they persist, and how much payload they produce — are as important to translation as any genetic innovation. Uncertain pharmacology and host clearance, they note, have limited clinical translation as much as any scientific failure.

The conclusion the authors reach is a deliberate reorientation of the field’s ambitions. Rather than maximizing circuit complexity — building bacteria with ever more layers of sensing, logic, and actuation — the priority should be simplicity that can be measured, controlled, and reproduced. A strain expressing a single well-characterized payload under a validated hypoxia-responsive promoter, delivered by a route matched to the tumor, quantitatively tracked, and paired with a clear rescue plan, is more likely to advance the field than a marvel of genetic engineering whose behavior in a patient cannot be predicted or verified. In that sense, the resurrection of bacterial cancer therapy is less a technological triumph than a discipline: the tumors, the microbes, and the clinic must all agree before the therapy works.

For a field that has oscillated between enthusiasm and abandonment since the days of Coley’s toxins, the framework offers something rare — a sober synthesis that treats past clinical disappointments as data rather than dead ends. With synthetic biology now supplying the control layer that earlier generations lacked, and with early studies across six bacterial genera providing the empirical grounding, engineered bacteria may finally be positioned to take their place among living therapeutics, not as a replacement for existing oncology tools but as a complement designed around the one environment cancer drugs have never fully reached: the hypoxic, necrotic, immunologically complicated interior of a solid tumor.

Subject of Research: Synthetic biology approaches to engineered bacterial cancer therapeutics

Article Title: Synthetic biology resurrects bacterial cancer therapy

Article References: Regmi, M., Kong, B., Xiong, Y., Liu, S., Liu, J., Xia, Q., & Yang, C. (2026). Synthetic biology resurrects bacterial cancer therapy. BMC Medicine. https://doi.org/10.1186/s12916-026-05272-2

Image Credits: AI Generated

DOI: 10.1186/s12916-026-05272-2

Keywords: synthetic biology, bacterial cancer therapy, living therapeutics, tumor microenvironment, tumor microbiome, Salmonella, E. coli Nissle, oncolytic viruses, hypoxia-responsive circuits, quorum sensing, translational design, BMC Medicine

Historically, the application of bacteria in cancer therapy can be traced back to the 1860s, a time when early medical practitioners noted that some patients exhibited cancer regression following bacterial infections. Despite these initial observations, the journey toward clinically viable bacterial immunotherapy has encountered numerous hurdles, particularly concerning safety and efficacy. As researchers have ventured forward, they have been met with the daunting challenge of ensuring that therapeutic bacteria are not only effective against tumors but also pose minimal risk to healthy tissues.

Fast forward to the present, recent strides in synthetic biology have catalyzed the engineering of advanced bacterial strains with antitumor properties. These developments offer promising new pathways in the burgeoning field of immuno-oncology, yet practical applications of such engineered bacteria remain encumbered by their enigmatic mechanisms. Central to this complexity is the ability of modified bacteria to circumvent the host immune defenses while simultaneously eliciting vigorous antitumor responses—a conundrum that has left researchers scrambling for answers.

In their pioneering study, the research team introduced the attenuated strain known as DB1. This engineered bacterium demonstrates a remarkable ability to not only survive and proliferate within tumor microenvironments but also to be efficiently cleared from normal tissues. This duality offers an elegant solution to the ever-present challenge of achieving tumor specificity. The researchers were keen to decode the underlying mechanisms allowing DB1 to manifest this desired "tumor-targeting" effect along with its concomitant "tumor-clearing" properties.

As part of their inquiry, the research team began investigating the intricate interactions between DB1 and the tumors it targets. Their studies unveiled a fascinating relationship between the antitumor efficacy of DB1 and the activation of tissue-resident memory (TRM) CD8+ T cells within the tumor microenvironment. Following treatment with DB1, an observable rejuvenation and expansion of these T cells occurred, suggesting that the bacteria play a pivotal role in bolstering immune responses against tumors.

Central to the activation of these immune cells was the cytokine interleukin-10 (IL-10), which emerged as a key mediator in orchestrating the therapeutic effects of DB1. The research demonstrated that the efficacy of this bacterial therapy hinges on the high expression levels of the interleukin-10 receptor (IL-10R) found on the CD8+ TRM cells. This crucial insight opens the door to potential strategies aimed at enhancing the specificity and effectiveness of bacterial immunotherapy by carefully modulating IL-10R expression.

In a more detailed exploration of the molecular mechanisms governing the heightened expression of IL-10R on CD8+ TRM cells, the researchers conducted a series of sophisticated computational and quantitative experiments. These investigations illuminated the pathway through which IL-10 binds to IL-10R, consequently activating the STAT3 protein. The activation of STAT3 not only bolstered IL-10R expression but also established a positive feedback loop, enhancing the ability of CD8+ TRM cells to ‘remember’ prior IL-10 stimulation. This mechanism of IL-10R hysteresis represents a nonlinear response where the memory of immune stimulation is crucial for sustaining a therapeutic effect during tumor progression.

Moreover, the study meticulously examined how the IL-10 within the tumor microenvironment is influenced following DB1 therapy. It was discovered that tumor-associated macrophages (TAMs) upregulate IL-10 expression in response to DB1 via the Toll-like Receptor 4 (TLR4) signaling pathway. This finding underscores the intricate interplay between bacterial therapy and the innate immune components within the tumor, revealing ways TAMs may enhance the therapeutic index of DB1.

Interestingly, the study also uncovered a previously unappreciated aspect of the tumor microenvironment. The presence of IL-10 was shown to alter the migration dynamics of tumor-associated neutrophils (TANs), effectively slowing their migration. This inhibition assists DB1 in evading rapid immune clearance, illustrating yet another layer of complexity in its therapeutic efficacy. The dependence on high IL-10R expression among immune cells associated with tumors further emphasizes the importance of IL-10 dynamics in realizing effective bacterial therapies.

Howard Liu reflected on the significance of their findings, stating, "Our research illuminates a crucial, yet previously unresolved mechanism in bacterial cancer therapy. The elucidated IL-10R hysteresis mechanism not only provides valuable insights but also serves as a guiding principle for the design of engineered bacteria, enhancing safety and efficacy."

The implications of this study ripple across the landscape of cancer treatment, offering a glimmer of hope to those contending with the disease. The advancement in our understanding of bacterial immunotherapy and its multifaceted interactions with the immune system represents a significant leap towards more effective and safer cancer treatments. Future explorations may further define how engineered bacterial strains can be tailored to exploit these mechanisms, ultimately paving the way for novel therapeutic interventions.

With this study, the combined efforts of Liu and Xiao not only highlight the essential role of understanding host-pathogen interactions in therapeutic context but also galvanize the pursuit of integrating synthetic biology into the realm of personalized cancer treatments. As this domain continues to evolve, it is poised to redefine our approach to combating one of humanity’s most formidable foes—cancer.

Ultimately, this trailblazing research not only signifies a monumental advancement in our fight against cancer, but also opens up numerous avenues for further studies and interventions. The findings serve as a powerful reminder of the potential held within engineered biological solutions, especially as we uncover more about the intricate dance between immune responses and pathogenic strategies.

Subject of Research: Bacterial cancer therapy mechanisms
Article Title: Bacterial immunotherapy leveraging IL-10R hysteresis for both phagocytosis evasion and tumor immunity revitalization
News Publication Date: March 3, 2025
Web References: N/A
References: N/A
Image Credits: N/A
Keywords: Cancer therapy, bacterial immunotherapy, IL-10, TRM cells, immuno-oncology.