Monoclonal antibodies can block tumor growth using many mechanisms.
1. Monoclonal antibody bound to antigen activates complement components (small ring between the two antibody molecules), leading to opsonization of cancer cells by phagocytic cells expressing complement receptors (orange half-circles), direct lysis of tumor cells and inflammation with recruitment of inflammatory cells.
2. Monoclonal antibody binds to activating Fc receptors on the effector cells, leading to antibody-dependent cellular cytotoxicity (ADCC) or release of cytokines.
3. Monoclonal antibody binds to inhibitory Fc receptors (or to both activation and inhibitory Fc receptors), inhibiting effector cell activation.
4. Monoclonal antibody binds directly to growth factor receptors or other signaling molecules on the cancer cell, leading to cell death.
References
Weiner LM. Building better magic bullets—improving unconjugated monoclonal antibody therapy for cancer. Nat Rev Cancer. 2007 Sep;7(9):701-6. PMID: 17721434
Imai K, Takaoka A. Comparing antibody and small-molecule therapies for cancer. Nat Rev Cancer. 2006 Sep;6(9):714-27. PMID: 16929325
Monoclonal antibody therapies−a ’constant’ threat to cancer. Alan N. Houghton & David A. Scheinberg. Nature Medicine 6, 373 - 374 (2000)