The team in the Breakthrough Breast Cancer Research Centre at The Institute of Cancer Research, London, studied samples from 58 patients with HER2-positive breast cancer.
By looking at genes which were commonly over-expr essed in these tumours, they identified one called TFAP2C which appeared to be critical for the survival of cancer cells within some tumours.
The work showed that even tumours classified as HER2 positive could be very different from each other and suggests that only a proportion of these tumours actually rely on the HER2 receptor for their survival. This explains why treatments targeted at HER2 can sometimes be ineffective, because the tumours are able to survive without it.
Study co-author Dr Chris Lord, senior scientist in the Breakthrough Breast Cancer Research Centre at The Institute of Cancer Research, said:
“We know that some patients with HER2-positive breast cancer don’t respond to treatment, and others stop doing so after time. This research uncovers some of the reasons why that might be, and allows us to start investigating genes involved in helping tumours to survive. While this work shows that HER2-positive breast cancers are without doubt much more complex than we first thought, our new understanding gives us the opportunity to find new ways to combat them.
“We now need to study how these genes respond to treatments and then work out strategies to overcome drug resistance in these patients.”
HER2-positive breast cancer accounts for about one in seven of all breast cancer cases, or about 7,000 cases in the UK each year. It is an aggressive form of the disease, and despite the positive impact of the drug Herceptin (trastuzumab) is still associated with lower survival than for the disease overall.
The results are published in the journal Oncogene.