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. 2013 Jun 7;5:91–101. doi: 10.2147/CMAR.S32973

Figure 1.

Figure 1

(A and B) Strategies to overcome acquired epidermal growth-factor receptor (EGFR)-tyrosine kinase inhibitor (TKI) resistance in non-small-cell lung cancer (NSCLC). (A) The T790M secondary mutation in exon 20 of EGFR is present in 50%–70% of NSCLC patients who acquire resistance to EGFR-TKIs, such as gefitinib or erlotinib. In such patients, gefitinib is not able to compete with adenosine triphosphate (ATP) for binding to the ATP-binding cleft of EGFR because of an increased affinity of this site for ATP. Treatment with irreversible EGFR-TKIs or EGFR-TKIs selective for EGFR harboring T790M is thus thought to represent a potential approach to overcome the resistance conferred by this mutation. (B) Amplification of MET is apparent in 5%–15% of NSCLC patients who acquire EGFR-TKI resistance. In this situation, MET signaling through ErbB3 (HER3) is activated in addition to EGFR signaling, with the result that both gefitinib and a MET inhibitor (such as PHA665752) are necessary to overcome the resistance conferred by MET amplification. The combination of inhibitors that block molecules that function downstream of both EGFR and MET, such as a phosphoinositide 3-kinase (PI3K) inhibitor combined with an MEK (ERK kinase) inhibitor, might also be an alternative approach to overcome the resistance induced by MET amplification.