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An international research team has discovered a novel target for treating aggressive breast cancers.

Researchers studied interaction between an oncogene ErbB2 and a protein Erbin, which binds to it to stabilize it, to determine if this interaction can be modulated to reduce proliferation of aggressive ErbB2 positive breast cancer. According to findings of the study published in the journal PNAS, researchers found that when Ebrin levels were lowered the rate of cancer growth and its spread declined.

"The findings point toward 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. Erbin could be a diagnostic biomarker that physicians look for in breast tissue biopsies," said Dr. Lin Mei, corresponding author of the study, in a news release.

ErbB2 is present both inside and outside tumor cells as a protrusion. While medications target the protrusions outside, tumors cells can mutate and avoid the protrusion.

"Breast cancer cells can mutate so they no longer have an external protrusion of ErbB2, leaving Herceptin and other breast cancer medication without a place to bind. While getting inside the cells can be more difficult, the ability to target intracellular Erbin could one day make a difference for these patients," Mei said.

In such cases, disrupting interaction between Erbin and ErbB2 still prevents cancer proliferation. "Erbin itself could be a novel target: you disrupt the interaction, and it will be therapeutic. Secondly, when a patient becomes Herceptin-resistant because the extracellular domain of ErbB2 is lost, this approach should still be effective because of the critical interaction of the two," Mei said.

The findings were reported based on mice studies but also found over expression of gene and the protein in 171 cases of aggressive human breast cancer.