Characterisation of a male and female breast cancer predisposition locus at 14q24.1

Genome wide association studies of male and female breast cancer have identified a predisposition locus at 14q24.1. Analysis of interacting chromatin fragments using proximity ligation-based chromatin conformation capture analysis in cell-line models of female breast cancer has implicated ZFP36L1 as a putative target-gene of the predisposition SNPs. Here we demonstrate, using chromatin conformation capture in a novel cell-line model derived from normal male breast epithelial cells, that ZFP36L1 is also a candidate target-gene at 14q24.1 in male breast cancer. ZFP36L1 is a member of a family of early response genes, which include the closely related genes ZFP36 and ZFP36L2. ZFP36-family genes encode RNA binding proteins that bind to the 3’ UTRs of target mRNAs to regulate their expression and ZFP36L1 has been found to be recurrently somatically mutated in breast cancer, providing support for an aetiological role. In order to illuminate the mechanisms via which ZFP36L1 might influence breast cancer risk, we created ZFP36L1 CRISPR-knockout models in MCF10a cells. In the absence of ZFP36L1 expression these cells demonstrated increased proliferation in both complete and depleted media, relative to wild-type MCF10a cells. Increased expression of ZFP36L2 was observed after either CRISPR or siRNA mediated knockdown of ZFP36L1 in MCF10a cells suggesting genetic compensation. In order to compare and contrast the biological functions of ZFP36L1 and ZFP36L2 we performed a series of tethered function assays in MCF10a cells which suggested that while ZFP36L1 can influence both mRNA translation and stability, ZFP36L2 affects only stability. These observations suggest that perturbation of translational efficiency and stability of target-mRNAs by varying ratios of ZFP36L1 and ZFP36L2 expression might contribute to the underlying mechanism of breast cancer predisposition at the 14q24.1 risk locus.