Amplification or over-expression of which oncogene plays an important role in the development and progression of certain aggressive breast cancers?

• A. KRAS
• B. HER2
• C. EGFR
• D. MYC

Answer: (B)

Amplification or over-expression of a receptor tyrosine kinase can drive aggressive tumor growth, and in a subset of breast cancers this is due to increased HER2 protein on the cancer cell surface. When the HER2 gene is amplified, the cell sends more growth signals through pathways like MAPK and PI3K-AKT, fueling rapid proliferation and a more aggressive course. This biology also makes these tumors responsive to targeted therapies that specifically inhibit HER2, such as trastuzumab and pertuzumab, which has improved outcomes for patients with HER2-positive breast cancer. Other genes like KRAS, EGFR, and MYC can be involved in cancers or contexts other than this breast cancer subset, but the hallmark driver for these aggressive cases is HER2 amplification.