Detection of gene copy number alterations in DCIS and invasive breast cancer by QM-FISH.

The exact roles of copy number alteration (CNA) in initiation, progression and immunotherapy of breast cancer and the genomic alterations behind progression from ductal carcinoma in situ (DCIS) to invasive carcinoma remain unknown. Quantitative multi-gene fluorescence in situ hybridization (QM-FISH) opens a possibility of large scale genomic analysis of specific deletions and amplifications with high-resolution at one cell level. We detected CNAs of 30 genes using QM-FISH and analyzed their association with clinicopathological parameters and patients' outcomes in 66 breast cancers with synchronous invasive carcinoma and DCIS. The copy numbers of 30 genes in DCIS and the invasive area in all tumors were compared. The results revealed some recurrent CNAs including amplifications of MDMx, CCNE2, HER2 and deletions in Chek1, p53, Rb1 with a frequency of over 20%. By comparing the CNAs in invasive tumors and co-occurring DCIS, the similarity of chromosomal instability (CIN) in both components was visualized. Some co-occurrence patterns of CNAs of 30 genes were observed. The study also demonstrated higher frequencies of occurrence of CNAs in aneuploidy tumors, high grade tumors and tumors with high proliferation index. Higher CNAs were also found in death patients. Overall, we uncovered some frequently occurring gene aberrations out of 30 genes and synchronous pre-invasive lesions share majority of CNAs with invasive breast cancer. Moreover QM-FISH is a powerful technique to detect CNAs of multi-genes and give more information on co-occurrence of CNAs.