A Novel SND1-BRAF Fusion Confers Resistance to c-Met Inhibitor PF-04217903 in GTL16 Cells though MAPK Activation

Nathan V Lee,Samuel Aparicio,James G Christensen,Shubha Bagrodia,Dana Buckman,Jingjing Ye,Sreesha P Srinivasa,Adam Pavlicek,Paul A Rejto,Maruja E Lira,Keith A Ching,Yongjun Zhao

doi:10.1371/journal.pone.0039653

Abstract

Targeting cancers with amplified or abnormally activated c-Met (hepatocyte growth factor receptor) may have therapeutic benefit based on nonclinical and emerging clinical findings. However, the eventual emergence of drug resistant tumors motivates the pre-emptive identification of potential mechanisms of clinical resistance. We rendered a MET amplified gastric cancer cell line, GTL16, resistant to c-Met inhibition with prolonged exposure to a c-Met inhibitor, PF-04217903 (METi). Characterization of surviving cells identified an amplified chromosomal rearrangement between 7q32 and 7q34 which overexpresses a constitutively active SND1-BRAF fusion protein. In the resistant clones, hyperactivation of the downstream MAPK pathway via SND1-BRAF conferred resistance to c-Met receptor tyrosine kinase inhibition. Combination treatment with METi and a RAF inhibitor, PF-04880594 (RAFi) inhibited ERK activation and circumvented resistance to either single agent. Alternatively, treatment with a MEK inhibitor, PD-0325901 (MEKi) alone effectively blocked ERK phosphorylation and inhibited cell growth. Our results suggest that combination of a c-Met tyrosine kinase inhibitor with a BRAF or a MEK inhibitor may be effective in treating resistant tumors that use activated BRAF to escape suppression of c-Met signaling.

Highlights

Aberrant receptor tyrosine kinase (RTK) activity provides growth and survival signals crucial for the development and progression of many cancers
GTL16R1 and GTL16R3 did not respond to growth inhibition by METi at concentrations up to 10 mM, while GTL16 were sensitive with an IC50 of 10 nM (Figure 1B)
Acquired resistance is a significant concern for single agent therapy based on precedence with agents like imatinib in CML and erlotinib in lung adenocarcinoma [48]

Summary

Introduction

Aberrant receptor tyrosine kinase (RTK) activity provides growth and survival signals crucial for the development and progression of many cancers. Treatment of patients with targeted inhibitors of key oncogenic kinase drivers such as sunitinib, erlotinib, gefitinib, and imatinib have demonstrated clinical success [1]. Despite successful clinical outcomes in select patient populations, the development of resistance to targeted inhibitors can result in disease progression and limit therapeutic effectiveness. The c-Met/HGFR receptor tyrosine kinase is a promising therapeutic target as mutations of c-Met (in papillary renal cell carcinoma, childhood hepatocellular carcinoma) and focal amplifications of the MET gene locus (in NSCLC, GBM, esophageal and gastric cancers) may indicate an oncogenic dependence on cMet signaling [6,7,8]. The activation of EGFR/ERBB family receptors [2,11,12], KRAS, BRAF, or AKT [13] can overcome c-Met inhibition

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Conclusion