Receptor PTKs can be targeted by two classes of drugs [26]: in the first class, monoclonal antibodies (mAbs) target the extracellular binding domain (Fig. 1) [27], and inhibit cancer cell growth via several direct processes such as interrupting PTK signaling in most cases by blockage of their ligand binding, inhibiting cell cycle progression or DNA repair, reducing angiogenesis, and inducing apoptosis, and via indirect processes mediated by the immune system such as complement-dependent cytotoxicity (CDC) and antibody-dependent cellular cytotoxicity (ADCC) [26] . The gene discussed is PTK2B; the disease is cancer.