Abstract 780: Normal breast tissues harbor rare populations of aneuploid epithelial cells

Abstract

Abstract Although aneuploidy is a hallmark of invasive breast cancers, the presence of aneuploid cells in breast tissues of disease-free women is poorly understood. Furthermore, the expansion of aneuploid cells and the specific copy number events that they harbor, as well as their relationship to invasive breast cancers has not been characterized in large cohorts of women. In this study, we obtained viable cell suspensions from 31 disease-free women that underwent reduction mammoplasty surgeries and fresh tissue collection in the HBCA project along with the collection of clinical metadata. The viable cell suspensions from 31 women were enriched for epithelial cells and used to perform high-thoughput nanowell scDNA-seq. In total, 55,321 cells were analyzed. The normal breast tissue samples were also embedded into OCT and frozen to perform Spatial Transcriptomics (Visium 10X Genomics) profiling and embedded into FFPE to perform histopathological analysis. Our data shows that all women harbored rare populations of aneuploid epithelial cells (mean 4.3%) that increased in frequency and their number of copy number aberrations with age. Many aneuploid epithelial cells (mean 79%) in normal breast tissues underwent clonal expansions of their genomes and harbored chromosomal aberrations detected in invasive breast cancers (gain of 1q and loss of 7q, 10q, 16q). Spatial mapping showed that aneuploid cells are localized in focal regions of ductal and lobular epithelial structures with normal histopathological features. Collectively, these data show that aneuploid epithelial cells exist in the normal breast tissues of disease-free women and increase with age. In many women, the aneuploid cells expand and harbor CNA events associated with invasive breast cancer. Citation Format: 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, Jessica Montalvan, Chandandeep Nagi, Sebastrian Winocour, Bora Lim, Alastair Thompson, Nicholas Navin. Normal breast tissues harbor rare populations of aneuploid epithelial cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 780.