Assessment of the clinical relevance of 17q25.3 copy number and three-dimensional telomere organization in non-small lung cancer patients

Abstract

Purpose: To identify potential biomarkers that may provide new therapeutic targets or prognostic indicators for non-small cell lung cancer (NSCLC), we investigated the three-dimensional (3D) organization of telomeres and cytoband 17q25.3 copy number in NSCLC tissues.

Methods: NSCLC paraffin-embedded tissue specimens from 18 patients were assessed for 3D telomere organization by 3D nuclear telomere imaging followed by quantitative analysis. Patients were stratified by smoking, histology, and EGFR status. Cytoband 17q25.3 was examined by fluorescent in situ hybridization. Data from comparative genomic hybridization and/or single nucleotide polymorphism arrays for cytoband 17q25.3 were obtained and correlated with Q-FISH and 3D telomere results.

Results: 3D telomeric profiling demonstrated that the smokers, EGFR-negative, and squamous cell carcinoma subgroups tended to have higher numbers of lower-intensity telomeres, indicative of shorter telomeres, as well as higher numbers of telomeric aggregations compared to non-smokers, EGFR-positive, and adenocarcinomas, respectively. Gains of cytoband 17q25.3 in conjunction with an increase in the control region 17p11.2 were observed in 7 of 18 (38.9 %) patients, reflecting a gain of chromosome 17. Clonal gains of cytoband 17q25.3 were observed in 11 of 18 (61 %) patients, highlighting a potential biological significance for the genes in this region in NSCLC tumourigenesis.

Conclusions: The 3D telomere profiles may differentiate NSCLC patients with different histologies, EGFR, and smoking statuses, rendering them a potential biomarker for distinguishing these clinically relevant histological and molecular subtypes of lung cancer. Highly frequent clonal gain of cytoband 17q25.3 was also demonstrated, suggesting an important biological role for the genes in this region.

Keywords: (non)Smoking; 3D telomere profiles; Chromosome 17q gain; EGFR; Non-small cell lung cancer.

Fig. 1

NSCLC cells underwent Q-FISH for PNA probe depicting: a telomeres (red signals). A representative nucleus is outlined in white and enlarged in b–d, c, d. Telomeres in 3D view (63×, objective)

Fig. 2

Telomere numbers against telomere intensities for: a non-smoking and smoking; b histology; c EGFR mutation subgroups of the NSCLC patients

Fig. 3

17q25.3 (red) and 17p11.2 (green) signals in NSCLC cells acquired from Q-FISH: a view from a distance. The scale bar represents 5 μm; b normal signals of both cytobands, 2 per each cell; c–e copy number gains of both cytobands, 5 of 17q25.3 and 6 of 17p11.2 (c), 6 of 17q25.3 and 5 of 17p11.2 (d), 4 of 17q25.3 and 5 of 17p11.2, with 4 pairs of signals demonstrating co-localization of 17q25.3 and 17p11.2 in yellow (e); f amplification of cytoband 17q25.3 (7 red signals) with normal 17p11.2 (2 green signals) (63×, objective)