C-MET gene copy number variation (CNV) analysis by quantitative PCR (qPCR) assay in Caucasian patients with gastric cancer (GC).

Background: Activation of the c-MET oncogene promotes tumor growth, invasion and metastasis. It has been shown that c-MET mutations are almost lacking in GC, while there is limited information on c-MET activation by CNV in caucasians. We investigated c-MET CNV in GC patients in Italy. Methods: A single-institution surgical database was used for this retrospective analysis. High risk stage II-III consecutive patients who underwent gastrectomy (R0 with D2 lymphadenectomy) between 1998 and 2007 were selected. For each case, formalin-fixed paraffin-embedded tumor specimens were used for DNA extraction and c-MET CNV detection by the TaqMan Gene Copy Number Assay (Applied Biosystem). The relative number of copies of three c-MET regions (Hs01602615 in exon 3, Hs05027935 in exon 12, Hs02884964 in exon 21) was determined. A sample was defined as c-MET CNV>2 when this status was found in at least two of the three studied c-MET regions. Results were analyzed for association with clinico-pathologic features and survival outcomes. Results: In 214 gastric carcinomas 98 cases (45%) showed c-MET CNV>2. No significant association with clinico-pathologic features was detected except for tumor histotype according to Lauren’s classification (p=0.01). c-MET CNV>2 occurred in 63/98 (64%) and 35/98 (36%) cases of intestinal and non-intestinal subtypes, respectively, while c-MET CNV<2 occurred in 64/116 (55%) and 52/116 (45%) cases of intestinal and non-intestinal subtypes, respectively. After a minimun follow-up time of three years, there were 87 relapses (40%). Log-rank tests showed significantly worse relapse-free survival (p=0.0008) and overall survival (p=0.0001) in patients with c-MET CNV>2. In multivariate models, these associations remained significant together with tumor stage. Conclusions: qPCR showed c-MET CNV in GC caucasian patients with impact on clinical outcomes. This finding is relevant to the current development of anti-MET therapeutics in this lethal disease. Ongoing analyses are refining the prognostic role of c-MET CNV considering CNV subgroups within the >2 copies group.