Abstract P1-03-11: Harnessing the distinctive properties of tumor-adjacent tissues to develop ethnicity-dependent biomarkers of breast cancer

Abstract

Abstract Recent data demonstrating a correlation between lymph node positivity at the time of detection, and the probability of disease recurrence even decades post detection only solidifies the principle that the detection of breast cancer prior to lymph node metastasis can appreciably better clinical outcomes. Although radiologic methods have greatly improved early detection and remain the mainstay for detection, molecular assays to complement existing strategies will reduce number of false positives as well as enhance detection in cases that preclude conclusive diagnosis with radiologic techniques. Normal breast biology is routinely studied using tissues from reduction mammoplasty or normal tissues adjacent to tumor (NATs). However, studies have shown histologic abnormalities in reduction mammoplasty samples and DNA methylation and gene expression abnormalities in NATs due to “field” effects of the tumor. To interrogate the differences between normal breast and NATs as potential early detection markers, we created a tissue microarray (TMA) comprising breast tissues of 100 age-matched healthy women from the Komen Tissue Bank (KTB) and tumor-NAT pairs from 100 women (a total of 300 samples). Approximately 50% of women in each set were of African American (AA) ancestry and the remaining was of European decent. The TMAs was curated as such, because of our recent findings on ethnicity-dependent differences in breast stem-luminal progenitor-mature cell hierarchy. TMA was analyzed for ZEB1, an oncogenic transcription factor that is central to cell fate and stemness, and estrogen receptor alpha (ERα) and FOXA1, which are expressed predominantly in hormone-responsive mature luminal cells. ZEB1 expressing cells were localized to surrounding ductal structures of the normal breast, whereas ERα+ and FOXA1+ cells were located within the ductal compartment. KTB-normal of AA women contained significantly higher levels of ZEB1+ cells compared to KTB-normal of Caucasian women (CA). We observed only marginal increases in ZEB1+ cells in NATs or tumors of AA women. By contrast, in CA women, both NATs and tumors compared to KTB-normal contained higher levels of ZEB1+ cells. The unique localization pattern external to the ductal structures, as well as intrinsically higher expression in AA women suggest that ZEB1+ cells serve not only as stem cells from which cancers may originate but could also contribute to the microenvironment conducive for ductal tumor progression leading to aggressive and early onset of breast cancer as observed in AA women. Conversely, KTB-normal of AA showed modestly higher FOXA1 expression compared to CA women, and further, FOXA1 levels were declined in NATs of AA but not CA women. ERα levels did not change in any of our analyses, pointing to the specificity of ethnicity-dependent changes in this TMA. We also noted ethnicity-dependent variations in the levels of CD8+ T cells, PD-1+ immune cells and PD-L1+ cells but not CD68+ macrophages in NATs, suggesting distinctive immune environment in NATs. This comprehensive approach will not only serve as a platform to develop tumor-adjacent “normal” tissues as molecular markers for early detection but also provides a molecular basis for aggressive breast tumor in AA women. Citation Format: Nakshatri H, Kumar B, Burney H, Cox ML, Jacobson M, Sandusky G, D'Souza-Schorey C, Storniolo AM. Harnessing the distinctive properties of tumor-adjacent tissues to develop ethnicity-dependent biomarkers of breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-03-11.