Bevacizumab is used in metastatic colorectal cancer. It exerts its antitumour effect by:
- A Binding VEGFR-2 on tumour cells, blocking intracellular tyrosine kinase signalling
- B Inducing ADCC against VEGFR-expressing cancer cells via its Fc region and NK cell activation
- C Binding circulating VEGF-A, preventing it from binding to VEGFR-1 and VEGFR-2 on endothelial cells, thereby inhibiting tumour angiogenesis ✓
- D Blocking EGFR dimerisation on colorectal cancer cells, reducing RAS-MAPK proliferation signals
Correct answer: C. Binding circulating VEGF-A, preventing it from binding to VEGFR-1 and VEGFR-2 on endothelial cells, thereby inhibiting tumour angiogenesis
Explanation
Bevacizumab is a humanised monoclonal antibody (IgG1) that binds all isoforms of VEGF-A with high affinity. By sequestering circulating VEGF-A, it prevents VEGF from binding its receptors (VEGFR-1 and VEGFR-2) on tumour vascular endothelial cells, inhibiting new vessel formation (angiogenesis) and normalising existing tumour vasculature. It does not target VEGFR directly (receptor kinase inhibitors like sunitinib/sorafenib do). EGFR-targeting antibodies include cetuximab and panitumumab.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
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