ODP441 NErbB-2 and Androgen Receptor Regulate a Gene Signature Involved in Immune Response and Favorable Outcome in TNBC

Abstract

Abstract Triple negative breast cancer (TNBC) has poor prognosis and neither established biomarkers nor therapeutic targets. On the one hand, the androgen receptor (AR), a steroid hormone receptor (SR) which is expressed in 10-53% of TNBC and proved to be critical for BC proliferation, has been proposed as a new target in TNBC. On the other, we and others have shown that membrane ErbB-2 migrates to the nucleus (nuclear ErbB-2, NErbB-2) where it binds DNA at HER-2 associated sequences (HAS) to regulate BC proliferation and migration. Since we have previously shown a functional interplay between growth factors and SR signaling pathways in BC, we propose the existence of an interaction between AR and ErbB-2 which is involved in NErbB-2+/AR+ BC growth. The experimental model used was the human TNBC cell line MDA-MB-453 which displays high expression levels of AR and NErbB-2. We have previously shown that dihydrotestosterone (DHT)-activated AR induces Src-mediated ErbB-2 rapid activation and its migration to the nucleus where it binds to HAS sites in the DNA. By coimmunoprecipitation and WB studies, we have now shown that this crosstalk involves ErbB-2 and AR physical association which is inhibited by the AR antagonist enzalutamide. By microarray and bioinformatics analysis we have also previously identified a set of differentially expressed genes (DEGs) in the presence of DHT and NErbB-2 eviction to define an independent predictor of better clinical outcome in TNBC. By using the Tumor Immune Estimation Resource (TIMER) we found a significant association of the expression of the gene signature and the abundance of tumor immune infiltrates, in accordance with the involvement of the gene signature in the immune response and interferon pathways. We have validated the regulation of the gene signature in MDA-MB-453 cells and found that in the presence of DHT, eviction of NErbB-2 significantly induces the mRNA expression of the genes CXCL10, HLA-A, NMI, STAT1 and TAP1, members of said gene signature. We have also identified AREs and HAS sites in STAT1, NMI and TAP1 and studied AR and ErbB-2 recruitment to the chromatin by ChIP assays. We found that DHT induces ErbB-2 binding to its HAS sites in STAT1 in regulatory regions. Our findings evidence that DHT-activated AR induces ErbB-2 rapid activation and its migration to the nucleus where it binds to HAS sites in regulatory regions of a set of genes involved in the immune response in TNBC. Presentation: No date and time listed