HER2 (ERBB2) Gene: Oncogenic Signaling and Clinical Testing

HER2 (ERBB2) is a clinically significant proto-oncogene that regulates cell proliferation, differentiation, and survival. Its aberrant activation is a primary driver in multiple malignancies, making it a cornerstone of precision oncology.

I Molecular Definition of the HER2 Gene

HER2 encodes a transmembrane receptor tyrosine kinase belonging to the epidermal growth factor receptor (EGFR/ERBB) signaling axis. This family includes four key members:

• EGFR (HER1)
• HER2 (ERBB2)
• HER3 (ERBB3)
• HER4 (ERBB4)

Unlike other ERBB receptors, HER2 lacks a known soluble ligand. It is unique because it is constitutively poised for heterodimerization, allowing it to pair with other ERBB members to initiate potent downstream signals. While expression is tightly regulated in healthy tissues, pathological gene amplification leads to sustained oncogenic activity.

II Oncogenic Impact of HER2 Dysregulation

Abnormal HER2 activation is a hallmark of tumor aggressiveness. In breast cancer, approximately 20%–30% of cases exhibit HER2 amplification.

Despite these challenges, HER2 has emerged as a highly actionable biomarker. The identification of HER2 gene amplification provides the essential molecular basis for precision treatment selection, allowing patients to benefit from targeted therapies like monoclonal antibodies and ADCs (Antibody-Drug Conjugates).