Evaluation of c-Met FISH on Non-Small Cell Lung Cancer Samples with Known EGFR Mutational Status
Kenneth J Bloom, Tommy Ha, Lisa Uyeda, Paul Choppa. Clarient, A GE Healthcare Company, Aliso Viejo, CA
Background: c-MET is a proto-oncogene that encodes hepatocyte growth factor receptor, a member of the receptor tyrosine kinase family. Activation of the signaling pathway results in a variety of cellular responses including proliferation, decreased apoptosis, angiogenesis and increased motility. c-MET can be over-expressed or amplified in a number of epithelial cancers including lung cancer. C-MET amplification has been associated with advanced stage, high histologic grade and EGFR amplification but not activating EGFR mutations and has been observed in less than 5% of non-small cell lung cancer (NSCLC) patients not exposed to EGFR tyrosine kinase inhibitors. We sought to assess MET gene status in a series of NSCLC patients with known EGFR mutational status.
Design: Ninety-one formalin fixed paraffin embedded tissue samples were tested for EGFR mutations using an allele specific PCR which targets the most common mutations in the tyrosine kinase domain of EGFR, (QIAGEN). A subset of samples containing non-mutated, exon 19 deletions, L858R and T790M mutations was selected for c-Met analysis by FISH, (c-MET (7q31)/SE 7 probe, Poseidon/Kreatech Diagnostics, diluted 1:10 with tDenHyb-2 buffer, Insitus Biotechnologies). A cut-off value of c-MET:CEN 7 ratio of 2.0 was used to define amplification. Aneusomy was called when both average c-Met and average CEN 7 counts were greater than 3.8. Deletion of c-MET was called when the c-MET:CEN 7 ratio was ≤ 0.5.
Results: Of the 46 non-mutated samples tested, 3 (6.52%) were amplified, 7 (15.2%) were aneuploid and 3 (6.52%) had a deletion involving the c-MET locus. Of the 21 samples tested with an exon 19 deletion, 1 (4.76%) was amplified and 5 (23.8%) were aneuploid. Of the 20 samples tested with L858R mutations, 0 were amplified, 11 (55%) were aneuploid and 1 (5%) had a deletion involving the c-Met locus. Only 4 T790M mutated samples were tested and 1 (25%) was aneuploidy. Overall amplification, aneuploidy and a deletion involving the c-Met locus was identified in 4.4%, 26.4% and 4.4% of the NSCLC samples tested, respectively.
Conclusions: We confirmed that amplification of c-MET is seen in slightly less than 5% of patients with NSCLC, 6.5% of those without an EGFR mutation and 2.2% of those with harboring an EGFR mutation. Deletion of c-MET was equally as common as c-MET amplification, also seen in 4.4% of samples tested. Aneusomy was significantly more common being present in 26.4% of the samples tested. Further analysis of MET is warranted given its potential as a therapeutic target in lung cancer.
Tuesday, March 20, 2012 9:30 AM
Poster Session III # 301, Tuesday Morning