Irish scientists have discovered that a drug used to treat alcohol addiction may have a role to play in combatting chemotherapy resistance among patients being treated for the most common type of lung cancer.

Over 1,800 people die every year in Ireland from lung cancer. Chemotherapy is a key part of treatment for many patients, however treatment resistance is a major challenge.

While chemotherapy kills the majority of tumour cells within a tumour, some types of cancer cells, called cancer stem cells, continue to grow and divide and these contribute to the development of drug resistance. This can lead to the tumour recurring, or a secondary tumour developing, which can prove fatal.

Scientists from Trinity College Dublin, St James's Hospital and the Coombe Hospital have found that lung cancer cells that have high levels of ALDH activity - a recently identified marker of cancer stem cells - become resistant to chemotherapy.

However, they also found that the alcohol aversion drug, Disulfiram (Antabuse), which is approved by the US Food and Drug Administration (FDA) and has been used to treat alcohol addiction for over 60 years, works against ALDH by restricting its activity.

With alcohol addiction, it works by preventing the body from metabolising alcohol, which means when a person drinks, they feel sick. With non-small cell lung cancer - the most common type of lung cancer - the drug inhibits the activity of ALDH. This results in decreased tumour cell growth and increased killing of lung cancer stem cells.

The scientists found that use of the drug with chemotherapy was much more effective at killing drug-resistant lung cancer stem cells than use of chemotherapy on its own.

"Disulfiram is an already approved drug with well tolerated side-effects which can be taken orally. Its potential use may give chemotherapeutic drugs a new lease of life in the treatment of resistant lung tumours.

"We believe that our research findings show that this is a really important option that warrants further investigation and clinical testing," commented Dr Martin Barr, a lead investigator in the Thoracic Oncology Research Group at St James's Hospital and Trinity.

The researchers pointed out that the development of new drugs is time-consuming and expensive, therefore finding new uses for existing drugs, which is known as ‘repurposing', may allow for ‘new uses of an old drug'.

"Such repurposing is a proven short cut between the research laboratory and the clinic," explained Dr Lauren MacDonagh, who carried out this study as part of her PhD at Trinity.

Details of these findings are published in the journal, Oncotarget.