Abstract 6116: Rs2363956, a coding variant of ANKLE1, drives triple-negative breast cancer disparity by altering DNA damage response
Authors: Guerra Yanira , Martini Rachel , Elemento Olivier , Davis Melissa B. 
Published: March 2024

Abstract
African American women have a 42% higher breast cancer mortality rate than European American women and are over twice as likely to develop triple-negative breast cancer (TNBC). We have previously demonstrated that this higher incidence of TNBC is tied to ancestry-related biological determinants of TNBC tumor biology, including possible novel genetic drivers that may result in reduced treatment efficacy.
Within the TCGA BRCA cohort, we have previously found that high ANKLE1 gene expression significantly improves survival in European Americans but not in African Americans. This difference may be attributed to the presence of a polymorphic variant of ANKLE1, rs2363956. The minor G allele of rs2363956 leads to a structural alteration in ANKLE1, potentially changing its functionality. Interestingly, among our International Center for the Study of Breast Cancer Subtypes (ICSBCS) patient cohort, we observed that 41-53% of European Americans with TNBC were homozygous for the G allele as compared to only ~14% of African American patients. These observations suggest that the presence of the rs2363956 polymorphic variant may drive differences between European American and African American patients.
ANKLE1 is a conserved gene among eukaryotic organisms and has been reported as an endonuclease implicated in DNA damage repair. Among our patient cohort (n=62) we have observed that patients homozygous for the G allele (n=13) are enriched for COSMIC mutational signatures 2 and 13 (P≤.05 and P≤.001, respectively), that denote overactivity of APOBEC deaminases, as compared to patients homozygous for the T allele (n=19). Therefore, the increased mutational burden present in those patients caused by APOBEC overactivity may sensitize those cancer cells to chemotherapeutics or other therapies.
Alternatively, the patients homozygous for the T allele may have an increased capacity for DNA damage repair that does not involve APOBEC activity. Using the MDA-MB-231 cell line, which is homozygous for the T allele, we performed an ANKLE1 knockdown with siRNA in order to examine the impact of ANKLE1 loss on DNA damage repair. Upon treatment with 25 μM, 10 μM, and 5 μM of Cisplatin we observe increased γ-H2AX and cell shrinkage in the ANKLE1 knockdowns as compared to cells treated with control siRNA, denoting increased DNA damage and apoptosis. Additionally, after knocking down ANKLE1 we observed decreased proliferation.
Based on these observations, ANKLE1 is critical for DNA damage response in TNBC cells and may be implicated in the genomic stability of TNBC. The polymorphic variants observed may impact this function and in part explain why European American patients have improved survival, as compared to African American patients.
Citation Format: Yanira Guerra, Rachel Martini, Olivier Elemento, Melissa B. Davis. Rs2363956, a coding variant of ANKLE1, drives triple-negative breast cancer disparity by altering DNA damage response [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 6116.