New breast cancer hope
J Nat Cancer Institute 2014 doi: 10.1093/jnci/dju169
Breast cancer encompasses at least four main subtypes (Nature 2012 490:61-70). Around one in five breast cancers express a gene called HER2. HER2-positive cancers grow and spread especially aggressively.
Trastuzumab (Herceptin), the first line treatment for HER2-positive cancers, blocks signals promoting growth sent from protein encoded by HER2. However, up to 70% of patients do not respond to or develop resistance to trastuzumab. Researchers,, have shown that a protein called avß6 helps breast cancer cells grow and spread.
Researchers analysed breast cancer samples from 2992 patients. Normal breast tissue did not express avß6. However, 40% of tumours from HER2-positive patients expressed avß6. After adjusting for other tumour features, patients with high levels of avß6 in their tumour were 60% more likely to die within five years of diagnosis than those with low levels. Those overexpressing both HER2 and avß6 were 97% more likely to die. In a subgroup of 1026 people, 30.9% of patients without avß6 had distant metastases, a statistically significant difference, compared with 39.5% of those who overexpressed the integrin.