The Role of MET Activation in Determining the Sensitivity to Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitors

Abstract

The development of resistance to epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKI) seems almost inevitable, even in patients with lung cancer that initially respond well to EGFR-TKIs. MET amplification was recently found to be a mechanism of escape from the anticancer effect of EGFR inhibitors. In the present study, we investigated the means whereby MET affects sensitivity to EGFR-TKIs in PC-9 cells. Gefitinib-or erlotinib-resistant sublines were established by exposing the parental PC-9 cell line to chronic, repeated treatments with these drugs. These resistant sublines showed more than 100-fold more resistance to gefitinib and erlotinib and acquired cross-resistance to other EGFR-TKIs. The T790M EGFR mutation was found by pyrosequencing, and this seemed to be the cause of drug resistance. Resistant cells also showed MET activation, although gene amplification was not detected. Furthermore, the induction of MET activity was not found to be associated with sensitivity to EGFR-TKIs. Interestingly, increased passage number without exposure to gefitinib or erlotinib caused MET activation, but this did not affect sensitivity to EGFR-TKIs. In addition, hepatocyte growth factor was found to block the ability of EGFR-TKIs to inhibit MET activation. However, sustained MET activation by hepatocyte growth factor did not modulate the cellular effects of gefitinib or erlotinib. Rather, activated MET enhanced migration and invasion abilities. Summarizing, MET activation may be acquired during cancer cell proliferation and enhances migratory and invasive abilities without affecting cellular sensitivity to EGFR-TKIs. Accordingly, the present study suggests that MET activation caused by factors other than MET gene amplification is not a suitable surrogate marker of resistance to EGFR-TKIs.

Potential Advantages of CUDC-101, a Multitargeted HDAC, EGFR, and HER2 Inhibitor, in Treating Drug Resistance and Preventing Cancer Cell Migration and Invasion

“…Very low levels of the T790M EGFR mutation were detected in clones TR13, TR19, and TR24 compared with H1975 NSCLC cells (Fig. 1D), in which the T790M mutant represents 69% of EGFR transcripts (16). This observation suggests that these clones acquired a few copies of the T790M-mutant EGFR gene while still expressing a large amount of erlotinib-sensitive E19-deleted EGFR protein.…”

“…14), and most recently overexpression of AXL (15). Notably, EGFR inhibitor-resistant tumor cell lines generated in vitro have shown cross-resistance to other receptor tyrosine kinase inhibitors (16), suggesting that combination therapy or inhibitors targeting multiple oncogenic pathways may be advantageous in overcoming resistance to EGFR inhibitors.…”

A Phase I/II Trial of Pazopanib in Combination with Lapatinib in Adult Patients with Relapsed Malignant Glioma

“…Additional factors that may have contributed to the low activity of these agents include the overall complexity of aberrant cell signaling in malignant glioma (3,41,42), deficiency of critical tumor suppressor molecules such as PTEN (43), and activation of alternative pathway mediators (44)(45)(46). Finally, although the antitumor activity of EGFRinhibiting agents may be enhanced by combination with VEGFR-targeting agents in some glioblastoma models (28), it is also possible that anti-VEGF therapy may have diminished lapatinib delivery to the tumor microenvironment (47).…”

Combined Treatment with Silibinin and Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitors Overcomes Drug Resistance Caused by T790M Mutation

“…Western blotting was done as described previously (20). The membrane was probed with antibody against p-EGFR, EGFR, ErbB2, ErbB3, p-Akt, Akt, and Erk (all from Santa Cruz Biotechnology), and p-ErbB2, p-ErbB3, p-Erk, and b-actin (all from Cell Signaling Technology) as the first antibody, and then the membrane was treated with horseradish peroxidase-conjugated secondary antibody.…”

“…These resistant cells acquired the T790M mutation (20). To evaluate whether addition of silibinin to EGFR-TKIs could overcome resistance caused by the T790M mutation, viability, and 3-D assays were done.…”