Integrative identification by Hi-C revealed distinct advanced structural variations in Lung Adenocarcinoma tissue

Advanced three-dimensional structure variations of chromatin in large genome fragments, such as conversion of A/B compartment, topologically associated domains (TADs) and chromatin loops are related closely to occurrence of malignant tumors. However, the structural characteristics of lung cancer still remain uncovered. In this study, we used high-throughput chromosome (HiC) confirmation capture to detect 2 non-smoking female lung adenocarcinoma (LUAD) tumor and paired normal tissues. The results indicated that significant chromatin variations were detected in tumor tissues compared with normal tissues. At compartment scale, the main conversion type of compartment is A[->]B in tumor tissues, which concentrated mainly on chromosome 3 (33.6%). Total of 216 tumor-specific TADs were identified in tumor tissues, which distributed mainly in chr1 (19), chr2 (15) and chr3(17). Finally we observed 41 distinct enhancer-promoter loops in tumor tissue, which associated closely to tumor-related pathways including MAPK, PI3K-AKT, Ras, Wnt and Ras1. The most important observation in this study was that we identified 5 important genes (SYT16, NCEH1, NXPE3, MB21D2, and DZIP1L), which were detected in both A[->]B compartment, TADs and chromatin loops. Four of these genes (NCEH1, NXPE3, MB21D2, and DZIP1L) located on q arm of chromosome 3, which also revealed the importance of chr3 in occurrence of structural variations in LUAD.