Detection of amplification in gastroesophageal tumor specimens using IQFISH.

Background: The gene mesenchymal epithelial transition factor () is a proto-oncogene that encodes a transmembrane receptor with intrinsic tyrosine kinase activity known as Met or cMet. is found to be amplified in several human cancers including gastroesophageal cancer.

Methods: Here we report the amplification prevalence data from 159 consecutive tumor specimens from patients with gastric (G), gastroesophageal junction (GEJ) and esophageal (E) adenocarcinoma, using a novel fluorescence in situ hybridization (FISH) assay, /CEN-7 IQFISH Probe Mix [an investigational use only (IUO) assay]. amplification was defined as a /CEN-7 ratio ≥2.0. Furthermore, the link between the MET signal distribution and amplification status was investigated.

Results: The prevalence of amplification was found to be 6.9%. The FISH assay demonstrated a high inter-observer reproducibility. The inter-observer results showed a 100% overall agreement with respect to the status (amplified/non-amplified). The inter-observer CV was estimated to 11.8% (95% CI: 10.2-13.4). For the signal distribution, the inter-observer agreement was reported to be 98.7%. We also report an association of amplification and a unique signal distribution pattern in the G/GEJ/E tumor specimens. We found that the prevalence of amplification was markedly higher in tumors specimens with a heterogeneous (66.7%) versus homogeneous (2.0%) signal distribution. Furthermore, specimens with a heterogeneous signal distribution had a statically significantly higher median /CEN-7 ratio (2.35 versus 1.04; P<0.0001).

Conclusions: The novel FISH assay showed a high inter-observer reproducibility both with respect to amplification status and signal distribution. Based on the finding in the study it is suggested that amplification mainly is associated with tumor cells that is represented by a heterogonous growth pattern.