New protein with 'anti-tumor factor' for breast cancer discovered

Scientists have discovered a new protein called Erbin, which is believed to be an anti-tumour factor in aggressive breast cancer.

One of the first-known oncogenes has a protein partner that helps breast cancer proliferate and when it's blocked, so is the cancer. The gene ErbB2, commonly called HER2, is highly expressed in about 25 percent of breast cancers. Scientists have now found the protein, which is highly expressed in these cancers and essential to ErbB2's support of breast cancer.

When scientists interfered with the interaction between the two in mice, it inhibited tumor development and the usual spread to the lungs. The team documented the over expression of both in 171 cases of mostly aggressive human breast cancer as well.

The findings pointed towards a new therapeutic target for aggressive breast cancer and potentially an adjunct for women who become resistant to Herceptin, or trastuzumab, the drug commonly given to ErbB2-positive patients, said corresponding author Dr. Lin Mei. Additionally, Erbin could be a diagnostic biomarker that physicians look for in breast tissue biopsies.

Mei said that Erbin itself could be a novel target: disrupt the interaction and it would be therapeutic. Secondly, when a patient became Herceptin-resistant because the extracellular domain of ErbB2 was lost, this approach should still be effective because of the critical interaction of the two.

The Food and Drug Administration approved Herceptin for women with metastatic breast cancer who overexpress ErbB2, or HER2, in 1998 and, in 2006, as an adjuvant treatment in early stage HER2- positive breast cancer.

The study is published in the journal PNAS.