Light-activated compound destroys cancer cells' energy source

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EPSRC-funded researchers use light to activate a cancer-killing compound which attacks the NADH co-enzyme – a vital energy-producing machinery in the cancer cells.

Scientists at the University of Warwick in collaboration with colleagues in China, France, Switzerland and Heriot-Watt University have developed a technique that uses light to activate a cancer-killing compound of Iridium. While current treatment methods mainly rely on the presence of oxygen, this compound will kill cancer cells in culture even when oxygen concentration is low (hypoxia).

The technique is detailed in a paper published in Nature Chemistry and could lead to another tool for clinicians to use in the fight against cancer, and potentially even vaccinate patients against future cancers. The research was supported by the Engineering and Physical Sciences Research Council, part of UK Research and Innovation.

Photodynamic therapy (PDT) uses light to kill cancer tumours in the body by activating a chemical compound called a photosensitiser, which creates species that can attack cancer cells in the presence of light. Using this method, clinicians can direct the light to specific regions of the cancer tumour and spare normal tissue from damage.

The technique can treat any tumours where light can be administered, and would be particularly suited to treat bladder, lung, oesophageal, brain and skin cancers. There are around 10,000 bladder cancer cases in the UK per year, of which about 5,000 might potentially benefit from this kind of treatment.

Once light-activated, the Iridium compound attacks the energy-producing machinery in the cancer cells - a vital co-enzyme called nicotinamide adenine dinucleotide (NADH) - and catalytically destroys that co-enzyme or changes it into its oxidised form. Cancer cells have a very high requirement for NADH, because they need a lot of energy to divide and multiple rapidly.

Professor Peter Sadler from the University of Warwick’s Department of Chemistry said: “There is an increasing interest in reducing the side effects of cancer treatment as much as possible and anything that can be selective in what it targets will help with that. The compound that we have developed would not be very toxic at all, we would give it to the cancer cells, allow a little time for it to be taken up, then we would irradiate it with light and activate it in those cells. We would expect killing of those cancer cells to occur very quickly compared with current methods.”

The team of scientists also noted that as the cancer cells die, they change their chemistry in such a way that they will generate an immune reaction in the body, what is known as an immunotherapeutic response. This suggests that those treated by this technique might be immunised against attack by that cancer, and will be investigated further in future research.