Final answer:
The overexpression of the HER2 gene in breast cancer cells leads to an excessive number of HER2 receptors which promotes unregulated cell growth and division, making the cancer more aggressive. Treatments such as Herceptin have been developed to target these receptors and improve patient outcomes.
Step-by-step explanation:
Approximately 25% of breast cancers exhibit overexpression of the HER2 gene. HER2 is a receptor tyrosine kinase, and its overexpression results in the presence of an excessive number of HER2 receptors on the cell surface. This overabundance can lead to unregulated cell division, as HER2 is a key regulator of cell growth and replication. The overexpression of HER2 thus contributes to the aggressiveness of certain breast cancer tumors.
Therapies targeting HER2, such as Herceptin (trastuzumab), have been developed for the treatment of these HER2-positive breast cancers. Herceptin is a monoclonal antibody that specifically binds to the HER2 receptors, marking them for destruction by the immune system and interfering with their growth-promoting signals. When used in combination with chemotherapy, this treatment approach has improved the survival rate in patients with metastatic breast cancer.