Copy number gains of chromosome 17 identified by dual in situ hybridization in non-small cell lung cancer tissue correlate with overexpression of c-Myc

Abstract

Background c-Myc regulates multiple genes involved in cell proliferation in various cancer types including non-small cell lung cancer (NSCLC). Copy number gains of cytoband 17q25.3, along with chromosome 17, have been reported in NSCLC patients, emphasizing the clinical significance as a potential molecular target for therapy. The upregulation of c-Myc has been found to accelerate tumor development associated with duplication of the syntenic human cytoband 17q25.3. This study aimed to explore and compare the correlations of chromosome 17 copy number and c-Myc expression in NSCLC with the paired-normal respiratory epithelium and to examine their role as potential molecular targets for NSCLC therapy. Methods A total of 66 NSCLC tissue samples with paired-normal respiratory epithelium were examined. The copy number of chromosome 17 was determined by human epidermal growth factor receptor 2 ( HER2 )/centromeric enumeration probe of chromosome 17 (CEP17) dual in situ hybridization (DISH). Results Copy number gains of chromosome 17 were identified in 8 of 60 (13.3%) available NSCLC specimens. No copy number gains of chromosome 17 were demonstrated in the paired-normal respiratory epithelium. The mean HER2 (1.2±0.3) and CEP17 (1.4±0.3) copy numbers of the normal respiratory epithelium were significantly lower than those of the NSCLC tissue [1.8±1.0 vs. 2.0±0.8, respectively (P<0.001)]. Twelve of 66 (18.2%) NSCLC patients had overexpression of c-Myc. Five (41.7%) of the patients whose tumors positive for c-Myc had HER2 gene amplification [1] or copy number gain of chromosome 17 [4]. HER2 gene amplification or copy number gain of chromosome 17 and high expression of c-Myc were associated with decreased overall survival. Conclusions Both biomarkers deserve further investigation to identify NSCLC patients with poorer survival outcomes requiring better therapeutic approaches.