Transtuzumab is targeted against-
**Core Concept**
Transtuzumab, also known as Trastuzumab, is a monoclonal antibody used in the treatment of certain types of breast cancer. It targets a specific protein on the surface of cancer cells, which is involved in their growth and survival.
**Why the Correct Answer is Right**
Trastuzumab specifically binds to the human epidermal growth factor receptor 2 (HER2), a receptor tyrosine kinase that promotes cell proliferation and survival. Overexpression of HER2 is found in approximately 20% of breast cancer cases. By binding to HER2, Trastuzumab inhibits the receptor's activity, leading to decreased cell proliferation and increased apoptosis (programmed cell death). This results in reduced tumor growth and improved patient outcomes.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as Trastuzumab does not target the epidermal growth factor receptor (EGFR), which is a different protein involved in cell signaling pathways.
**Option B:** This option is incorrect as Trastuzumab does not target the vascular endothelial growth factor receptor (VEGFR), which is involved in angiogenesis (formation of new blood vessels).
**Option C:** This option is incorrect as Trastuzumab does not target the programmed death ligand 1 (PD-L1), which is a protein involved in immune evasion by cancer cells.
**Clinical Pearl / High-Yield Fact**
Trastuzumab is often used in combination with other chemotherapy agents, such as paclitaxel or docetaxel, to improve treatment outcomes in patients with HER2-positive breast cancer. It is essential to identify patients with HER2 overexpression through diagnostic testing, such as immunohistochemistry or fluorescence in situ hybridization (FISH), to determine eligibility for Trastuzumab treatment.
**Correct Answer:** C. HER2.