Nature. 2024 Nov 20. IF: 50.5Normal breast tissues harbour rare populations of aneuploid epithelial cells.Yiyun Lin, Junke Wang, Kaile Wang, Shanshan Bai, Aatish Thennavan, Runmin Wei, Yun Yan, Jianzhuo Li, Heba Elgamal, Emi Sei, Anna Casasent, Mitchell Rao, Chenling Tang, Asha S. Multani, Jin Ma, Jessica Montalvan, Chandandeep Nagi, Sebastian Winocour, Bora Lim, Alastair Thompson, Nicholas Navin.University of Texas MD Anderson Cancer Center, Houston, TX, USA; Baylor College of Medicine, Houston, TX, USA.Aneuploid epithelial cells are common in breast cancer; however, their presence in normal breast tissues is not well understood. To address this question, we applied single-cell DNA sequencing to profile copy number alterations in 83,206 epithelial cells from the breast tissues of 49 healthy women, and we applied single-cell DNA and assay for transposase-accessible chromatin sequencing co-assays to the samples of 19 women. Our data show that all women harboured rare aneuploid epithelial cells (median 3.19%) that increased with age. Many aneuploid epithelial cells (median 82.22%) in normal breast tissues underwent clonal expansions and harboured copy number alterations reminiscent of invasive breast cancers (gains of 1q; losses of 10q, 16q and 22q). Co-assay profiling showed that the aneuploid cells were mainly associated with the two luminal epithelial lineages, and spatial mapping showed that they localized in ductal and lobular structures with normal histopathology. Collectively, these data show that even healthy women have clonal expansions of rare aneuploid epithelial cells in their breast tissues.DOI: 10.1038/s41586-024-08129-x Nat Genet. 2024 Nov 20. IF: 31.7Luminal breast epithelial cells of BRCA1 or BRCA2 mutation carriers and noncarriers harbor common breast cancer copy number alterations.Marc J. Williams, Michael U. J. Oliphant, Vinci Au, Cathy Liu, Caroline Baril, Ciara O’Flanagan, Daniel Lai, Sean Beatty, Michael Van Vliet, Jacky CH Yiu, Lauren O’Connor, Walter L. Goh, Alicia Pollaci, Adam C. Weiner, Diljot Grewal, Andrew McPherson, Klarisa Norton, McKenna Moore, Vikas Prabhakar, Shailesh Agarwal, Judy E. Garber, Deborah A. Dillon, Sohrab P. Shah, Joan S. Brugge, Samuel Aparicio.Memorial Sloan Kettering Cancer Center, New York City, NY, USA; Harvard Medical School (HMS), Boston, MA, USA; Dana-Farber Cancer Institute (DFCI), Boston, MA, USA; Brigham and Women’s Hospital (BWH), Boston, MA, USA; British Columbia Cancer Research Centre, Vancouver, British Columbia, Canada; University of British Columbia, Vancouver, British Columbia, Canada.The prevalence and nature of somatic copy number alterations (CNAs) in breast epithelium and their role in tumor initiation and evolution remain poorly understood. Using single-cell DNA sequencing (49,238 cells) of epithelium from BRCA1 and BRCA2 carriers or wild-type individuals, we identified recurrent CNAs (for example, 1q-gain and 7q, 10q, 16q and 22q-loss) that are present in a rare population of cells across almost all samples (n = 28). In BRCA1/BRCA2 carriers, these occur before loss of heterozygosity (LOH) of wild-type alleles. These CNAs, common in malignant tumors, are enriched in luminal cells but absent in basal myoepithelial cells. Allele-specific analysis of prevalent CNAs reveals that they arose by independent mutational events, consistent with convergent evolution. BRCA1/BRCA2 carriers contained a small percentage of cells with extreme aneuploidy, featuring loss of TP53, BRCA1/BRCA2 LOH and multiple breast cancer-associated CNAs. Our findings suggest that CNAs arising in normal luminal breast epithelium are precursors to clonally expanded tumor genomes.DOI: 10.1038/s41588-024-01988-0
