Japanese Researchers Make Cancer Cells Produce Their Own Anticancer Drugs

Researchers in Japan have developed an experimental cancer treatment technique that turns a chemical byproduct produced by cancer cells into an anticancer compound inside the cells themselves. The research team, led by Katsunori Tanaka at the RIKEN Pioneering Research Institute, developed a system that uses excess carbon monoxide (CO) produced by certain cancer cells to trigger the synthesis of potentially cancer-killing molecules.

The approach could eventually offer a new way to target tumours while reducing damage to healthy cells, one of the major challenges associated with conventional chemotherapy. The research was published in Nature Communications on September 17, 2026. However, the technique has so far been tested only in laboratory-grown cells and has not yet been evaluated in animals or humans.

How Japanese Researchers Are Turning Cancer Cells Against Themselves

The research focuses on carbon monoxide, a poisonous gas commonly associated with vehicle emissions and incomplete combustion.

Although carbon monoxide is toxic at high concentrations, the human body also naturally produces small amounts of it. Certain cancer cells produce higher levels of this molecule than normal cells, creating a chemical environment that researchers believe can be exploited.

The RIKEN team used this difference to develop a chemical reaction that converts carbon monoxide inside cancer cells into phenanthridinone derivatives, compounds that can have anticancer properties.

Instead of delivering a fully formed toxic drug directly into the body, the researchers developed a system that carries a chemical catalyst into cells and uses the cancer cells’ own carbon monoxide to produce the active compound.

This approach could potentially make cancer treatment more selective by generating toxic molecules where they are needed.

How the Experimental Cancer Treatment Works

The technology relies on three important components: carbon monoxide, a palladium-based catalyst and albumin, a protein naturally found in human blood.

Each component plays a different role in producing the anticancer compound.

1. Cancer Cells Produce Excess Carbon Monoxide

The researchers focused on carbon monoxide because certain cancer cells produce more of it than healthy cells.

This difference provides a potential chemical trigger for selectively generating therapeutic compounds inside tumours.

Rather than treating carbon monoxide only as a harmful byproduct, the scientists explored whether it could serve as a raw material for a chemical reaction.

2. Palladium Catalysts Convert Carbon Monoxide Into Anticancer Compounds

The team used organometallic compounds called palladacycles, which contain palladium and can participate in chemical reactions involving carbon monoxide.

The catalyst captures and activates carbon monoxide, helping convert it into phenanthridinone derivatives.

Some members of this chemical family have demonstrated anticancer activity and can interfere with processes required for cancer cell survival.

However, using palladium catalysts inside the human body presents a significant challenge.

Cells naturally contain glutathione, a molecule that can deactivate metal-based catalysts and prevent them from performing their intended reactions.

3. Albumin Protects the Catalyst Inside Cells

To overcome this problem, researchers placed the palladium catalyst inside a protective pocket within albumin.

Albumin is a protein naturally present in blood and is widely studied for its potential as a drug-delivery carrier.

The protein helps protect the palladium catalyst from glutathione, allowing it to retain its chemical activity inside cells.

Once the complex enters cancer cells, the catalyst can use the available carbon monoxide to produce the intended compound.

The researchers also modified the system so that the newly generated anticancer molecule could detach from the carrier and move freely inside the cell.

Laboratory Tests Showed Selective Activity Against Cancer Cells

The researchers tested their technology using several human cancer cell lines.

These included:

• Liver cancer cells.
• Cervical cancer cells.
• Breast cancer cells.
• Lung cancer cells.

They also included a non-cancerous cell line to investigate whether the reaction occurred selectively.

During the experiments, researchers incubated the albumin-palladium complex with the different cell lines for 48 hours.

They detected the intended chemical product in the four cancer cell lines but not in the normal cells at detectable levels under the initial experimental conditions.

The team subsequently modified the system to generate a more potent anticancer compound.

In tests involving liver cancer cells, the researchers observed that the compound was produced inside the cells and caused toxic effects.

The experiments provided proof that the cancer cells’ own carbon monoxide could be used as a chemical trigger for producing anticancer molecules.

However, the researchers described the therapeutic effect as modest, and the difference between cancer and normal cells still needs further improvement.

Why This Approach Could Be Different From Traditional Chemotherapy

Conventional chemotherapy often affects rapidly dividing cells throughout the body. Although it can destroy cancer cells, it can also damage healthy tissues, resulting in side effects such as hair loss, fatigue and nausea.

The Japanese research team is exploring a different strategy.

Instead of administering the active toxic compound directly, the researchers want to deliver a catalyst that produces the drug only after reaching the targeted cellular environment.

Feature	Conventional Chemotherapy	Experimental RIKEN Approach
Drug delivery	Administers an active anticancer drug	Delivers a protected chemical catalyst
Drug activation	Drug is already active or activated through biological processes	Cancer-cell carbon monoxide triggers chemical synthesis
Targeting strategy	Depends on drug distribution and biological selectivity	Uses elevated carbon monoxide as a chemical trigger
Healthy cell exposure	Can cause damage to healthy tissues	Designed to reduce unintended drug production
Research stage	Established clinical treatments	Laboratory proof of concept

The new approach is not yet proven to be safer or more effective than conventional chemotherapy. Its main potential advantage is the possibility of generating toxic compounds selectively inside cancer cells.

Researchers Investigate Whether the Reaction Could Occur in Blood

One potential safety concern was whether carbon monoxide circulating in the bloodstream could trigger the reaction before the catalyst reached a tumour.

If the anticancer compound were produced prematurely, it could potentially damage healthy blood cells.

The researchers investigated this possibility using blood samples.

They found no detectable production of the intended toxic compound during the test.

The team suggested that this was because carbon monoxide in blood is largely bound to haemoglobin, the protein responsible for transporting oxygen in red blood cells.

When carbon monoxide is bound to haemoglobin, it is less available to participate in the palladium-catalysed reaction.

This is an encouraging laboratory observation, but it does not establish that the treatment will be safe when administered to a living organism.

The Research Could Open a New Direction in Cancer Drug Development

The RIKEN team describes its broader research strategy as therapeutic in vivo synthetic chemistry.

The concept involves using chemical substances already present in the body to manufacture therapeutic compounds directly at the location of a disease.

Cancer cells often have different metabolic characteristics from healthy cells.

Researchers may therefore be able to use these differences as chemical triggers for producing medicines where they are needed.

For example, certain tumours produce elevated levels of specific metabolites that could potentially serve as raw materials for chemical reactions.

If this approach can be developed successfully, it could provide a new platform for targeted drug development beyond the carbon monoxide-based system demonstrated in the latest study.

The research also builds on earlier work from Katsunori Tanaka’s team, which explored synthesising anticancer compounds inside living organisms using metal catalysts.

In a separate 2022 study, RIKEN researchers demonstrated the possibility of assembling anticancer substances inside mice using a different chemical strategy.

However, the latest carbon monoxide-based technique remains at an earlier experimental stage.

What Happens Next?

The next major step is testing the carbon monoxide-based system in animal models.

Researchers will need to establish whether the albumin-palladium complex can reach tumours efficiently, generate sufficient quantities of the anticancer compound and avoid damaging healthy tissues.

Several important questions remain:

• Can the catalyst selectively accumulate inside tumours?
• Will the reaction work effectively in living organisms?
• Can researchers improve its cancer-killing effectiveness?
• What are the long-term safety implications of introducing palladium-based catalysts?
• Can the approach work across different cancer types?

The answers will determine whether the laboratory findings can eventually lead to a practical cancer treatment.

The researchers have not announced a clinical trial or a timeline for human testing.

The Bigger Picture

The Japanese research demonstrates an unusual approach to cancer treatment: instead of simply delivering a drug to destroy cancer cells, scientists are exploring ways to make cancer cells produce their own toxic compounds.

The technology uses elevated carbon monoxide as a chemical trigger and a protected palladium catalyst to manufacture anticancer molecules inside targeted cells. This could eventually provide another route towards more selective cancer therapies.

However, the findings should not be confused with a treatment breakthrough that is ready for patients. The experiments were conducted in laboratory-grown cells, the observed therapeutic effect was modest, and animal testing remains the next major milestone. The study is scientifically promising, but substantial research is still required before its potential medical benefits can be established.

Looking Ahead

The next phase of research will focus on evaluating the technology in animal models and determining whether it can safely produce sufficient quantities of anticancer compounds inside tumours. Improving the effectiveness of the chemical reaction and reducing its potential impact on healthy tissues will be essential before researchers can consider clinical development.

If successful, the approach could contribute to a broader category of cancer therapies that manufacture active medicines directly at disease sites. For now, the RIKEN team’s work represents an early proof of concept that shows how the chemical environment created by cancer cells could potentially be turned against them.