Irish scientists have discovered a way to make certain breast cancer cells respond to treatment, where previously they had become resistant.

The discovery centres on HER2-positive breast cancer, which accounts for around one in five breast cancers. Some 500 women are newly diagnosed with this every year in Ireland.

Women with this type of cancer are usually treated with chemotherapy and the drug trastuzumab, commonly known as Herceptin. However, many become resistant to this drug over time.

Now, a team at St Vincent's University Hospital in Dublin has found a way to change these resistant cancer cells, so that they again respond to treatment.

According to the team, which is headed up by Dr Patricia McGowan, it is already known that a specific protein, known as Notch, drives the growth of cancer cells.

The scientists' research is aiming to block Notch in order to improve the patients' response to Herceptin.

Early findings indicate that it is possible to turn off Notch or other pathways that the cancer needs to become Herceptin-resistant. Furthermore, this is possible using a combination of commercially available drugs.

In other words, cancer cells that initially fail to respond to treatment can be targeted again.

It is hoped that in the future, it will be possible to identify those women who are going to show resistance to Herceptin. In such cases, other drugs could be offered as soon as possible.

For women who are initially successfully treated with the drug, but then become resistant, it may be possible to reverse this resistance so that they again respond to the drug.

Dr McGowan said she and the team are ‘very excited' by these results.

"Our results also apply to resistance to certain chemotherapies and other drugs and so there are a number of different avenues that we are exploring at the moment," she explained.

She also emphasised the importance of research and thanked the Irish Cancer Society (ICS), which provided a €230,000 grant to fund this investigation.

"Every cent that is invested in breast cancer research brings us closer to finding better treatments and ultimately a cure. The funding from the ICS has been central to our investigation of Notch inhibition and without their support we would not have been able to make this exciting discovery," Dr McGowan added.

Details of this research are due to be presented at the 24th Annual Symposium on Molecular Targets and Cancer Therapeutics, which will take place in Dublin from November 6-9.