HER2 Mutation Status in Japanese HER2-negative Breast Cancer Patients

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Abstract

Objective

Human epidermal growth factor receptor 2 (HER2) gene amplification is a major therapeutic target in breast cancer, and has been introduced as a predictive biomarker to identify patients who may benefit from therapy with anti-human epidermal growth factor receptor 2 agents. Human epidermal growth factor receptor 2 somatic mutations have been reported in patients without human epidermal growth factor receptor 2 gene amplification. Since these are activating mutations, these patients may also benefit from human epidermal growth factor receptor 2-targeted drugs.

Methods

In this study, we searched for human epidermal growth factor receptor 2 mutations in a group of 286 Japanese breast cancer patients with human epidermal growth factor receptor 2-negative tumors. The activating mutations of human epidermal growth factor receptor 2 identified were analyzed by direct Sanger sequencing of two major areas: the extracellular domain at 309–310 and the kinase domain between 755 and 781.

Results

Two tumors were found to have a human epidermal growth factor receptor 2 somatic mutation; one with I767M mutation and another with D769Y. No mutation was observed in the extracellular domain. One of these patients with human epidermal growth factor receptor 2 mutation recurred early with liver metastasis.

Conclusions

Better knowledge of human epidermal growth factor receptor 2 mutation status will help us to choose personalized molecular targeted therapy for use in human epidermal growth factor receptor 2-negative Japanese breast cancer patients.

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