Scientists Discover How to Turn Cancer Cells Against Themselves Using a Poisonous Gas

Cancer cells may have a weakness hiding inside them, and scientists in Japan have found a way to exploit it. Researchers have developed an experimental technique that uses carbon monoxide produced inside certain cancer cells to trigger the creation of a toxic compound capable of killing them. The unusual approach essentially turns a substance already present inside the tumor into part of its own destruction, potentially opening a new direction for targeted cancer treatment.

The research was conducted by Katsunori Tanaka and his team at the RIKEN Pioneering Research Institute in Japan. Their findings, published in the peer-reviewed journal Nature Communications, demonstrate how a specially designed chemical system can manufacture an anti-cancer compound inside cultured cancer cells. The technique could eventually help researchers develop treatments that limit damage to healthy tissue, although it remains an early laboratory discovery and must undergo animal testing before its potential can be properly assessed.

Scientists Discover a Way to Use Cancer’s Own Chemistry

The researchers focused on carbon monoxide, a poisonous gas commonly associated with vehicle exhaust and accidental poisoning. Although most people recognize it as a dangerous substance, scientists have also discovered that certain types of cancer cells produce excess amounts of this gas. This unusual characteristic gave Tanaka’s team an opportunity to develop a chemical reaction that could take place inside the cancer cells themselves.

Their approach involved introducing a specially designed compound into cells, where the presence of carbon monoxide could trigger the production of a toxic substance. Instead of delivering the finished cancer-killing drug directly, the researchers wanted to transport the ingredients needed to manufacture it. The idea was to take advantage of differences in the chemical environments of cancerous and healthy cells, allowing the reaction to occur primarily where the excess carbon monoxide was present.

The strategy addresses one of the longstanding difficulties associated with conventional chemotherapy. Many chemotherapy drugs can damage healthy cells alongside cancerous ones, producing side effects that can make treatment difficult for patients. A system capable of producing its active drug mainly inside tumors could potentially reduce this unwanted exposure. However, the researchers still need to establish whether the selectivity observed in laboratory cells can be maintained inside a living organism.

Carbon Monoxide Helps Produce a Cancer-Killing Compound

Carbon monoxide became central to the experiment because of the way it interacts with specialized chemical compounds called palladacycles. These organometallic complexes contain palladium and can use carbon monoxide in a reaction that produces an organic compound known as phenanthridinone. Certain phenanthridinone derivatives have cytotoxic properties, meaning they can damage or kill cells, and some have already been used in anti-cancer drug development.

The researchers saw a possibility of combining these chemical properties with the excess carbon monoxide found in certain cancer cells. By introducing a palladacycle into the cell, they could potentially trigger the production of phenanthridinone precisely where the gas was available. This would allow the cell’s own chemical environment to help determine where the toxic compound was manufactured, creating a possible route toward more selective treatment.

The experimental process relied on three important stages:

• Chemical detection: Excess carbon monoxide inside certain cancer cells provides the conditions needed for the reaction.
• Catalyst activation: The palladacycle uses the available carbon monoxide to help manufacture phenanthridinone.
• Drug production: The reaction generates a cytotoxic compound that can damage the cancer cell from within.

The researchers needed to overcome several chemical challenges before this approach could work reliably. Simply introducing palladacycles into cancer cells was insufficient because substances naturally present inside cells could rapidly destroy the metal catalyst. Solving that problem became one of the most important parts of the project.

Scientists Found a Way to Protect the Catalyst Inside Cells

One major obstacle involved glutathione, a molecule naturally present inside cells that can deactivate palladium catalysts. This meant the researchers needed a protective system that would allow the palladacycle to survive long enough to complete its intended reaction. Without that protection, the catalyst could become inactive before producing the desired cancer-killing compound.

Tanaka’s laboratory had previously worked on in vivo metal-catalyzed reactions, giving the team experience with chemical reactions involving metal catalysts inside biological systems. Building on that research, they placed the palladacycle inside albumin, a protein commonly found in blood. The resulting albumin-palladacycle complex acted as a carrier, protecting the catalyst while allowing it to travel through the bloodstream and enter cells.

This development helped address the problem of catalyst destruction inside the cellular environment. The albumin structure protected the palladium component, allowing it to remain functional long enough to participate in the reaction. The researchers also adjusted the system so that the resulting phenanthridinone could detach from the carrier and move freely inside the cell, where it could exert its toxic effects.

Laboratory Tests Showed the Reaction Worked in Cancer Cells

After developing the delivery system, the researchers began testing whether it could produce phenanthridinone in different types of human cancer cells. They first screened a collection of palladacycles to identify which compounds generated the greatest amount of the desired product. Once they identified a suitable candidate, they combined it with albumin and examined its performance across several cell lines.

The experiments involved human liver, cervical, breast, and lung cancer cell lines, alongside a non-cancerous cell line used for comparison. Researchers incubated the albumin-palladacycle complex with the cells for 48 hours before examining whether phenanthridinone had been produced. The results showed that the desired compound appeared in the cancer cell lines, while it was not detected in the non-cancerous cells.

This was an important demonstration because it suggested that the reaction could take advantage of differences between cancerous and healthy cellular environments. The team then made additional adjustments to ensure that the manufactured compound could separate from its carrier and move around inside the cell. These modifications helped prepare the system for the next stage, which involved producing a more specifically selected toxic derivative.

The Experimental Drug Damaged Liver Cancer Cells

Once the researchers had established that the chemical reaction could occur inside cancer cells, they modified the albumin-palladacycle complex to produce a particular phenanthridinone derivative with strong cytotoxic properties. This version was designed to manufacture a compound used in anti-cancer drug development, allowing the team to examine whether the system could do more than simply generate a detectable chemical product.

The researchers tested the modified system using a liver cancer cell line. Their experiments showed that the intended toxic compound was produced inside the cells, which subsequently experienced its damaging effects. This demonstrated that the approach could combine targeted chemical production with the ability to harm cancer cells, at least under controlled laboratory conditions.

The distinction between this finding and an actual cancer treatment remains significant. The experiments demonstrated activity in cultured cells, not the elimination of tumors inside patients. Researchers still need to establish whether the chemical system can reach tumors effectively, remain stable inside the body, and produce enough of the desired compound without causing harmful reactions elsewhere.

Researchers Investigated Whether the Reaction Could Harm Blood Cells

Another concern involved what might happen if the chemical reaction accidentally occurred inside the bloodstream. If carbon monoxide circulating through the body could activate the palladacycle before it reached a tumor, the system might produce its toxic compound in the wrong location. That could potentially damage blood cells and create serious complications, undermining the very selectivity the researchers were trying to achieve.

The team therefore examined whether carbon monoxide in blood could trigger the same chemical process. Their experiments found that the blood remained free of the toxic drug. The researchers suggested that this was likely because carbon monoxide in the bloodstream is bound to hemoglobin, the protein responsible for transporting oxygen in red blood cells. When bound to hemoglobin, the gas was unavailable for the reaction that produced phenanthridinone.

This result addressed one potential concern surrounding the delivery system, although it does not establish that the treatment would be safe in humans. The behavior of the compound inside a living organism could differ from what researchers observed in controlled experiments. Further investigations will need to examine its distribution, stability, possible toxicity, and ability to reach cancerous tissue without affecting healthy organs.

Animal Testing Will Determine Whether the Discovery Can Advance

The next major step for Tanaka’s team is moving beyond cultured cancer cells and investigating the technique in animal models. This stage will help researchers determine whether the albumin-palladacycle complex can travel through the body, reach tumors, and produce the desired compound under real biological conditions. It will also provide an opportunity to investigate potential side effects that cannot be fully assessed using isolated cells.

Researchers will need to answer several important questions before the approach can be considered for human treatment. They must establish whether enough of the catalyst reaches the tumor, whether the reaction remains selective across different tissues, and whether the manufactured compound can damage cancer cells without producing unacceptable harm elsewhere. The team will also need to determine whether different cancer types produce sufficient carbon monoxide to make the technique effective.

Tanaka described the broader idea behind the research as a way of using substances naturally present or generated inside the body to manufacture therapeutic molecules at the site of disease. He explained: “In our therapeutic strategy, molecules naturally present or generated within the body, including disease-associated metabolites, are used as endogenous chemical feedstocks to synthesize therapeutic molecules directly at the site of disease.”

The discovery offers researchers a different way to think about cancer treatment, using a chemical characteristic of the disease as part of the treatment itself. For now, the results remain limited to laboratory experiments, and animal testing will determine whether the approach has potential beyond cultured cells. If future research confirms that the system can work safely inside living organisms, the poisonous gas produced by certain cancer cells could become an unexpected tool in the fight against them.

Sources:

1. Research News | RIKEN. (n.d.). https://www.riken.jp/en/news_pubs/research_news/?
2. Nature Communications. (2026, August 26). Nature. https://www.nature.com/ncomms/?