Androgen signaling connects short isoform production to breakpoint formation at Ewing sarcoma breakpoint region 1

Abstract

Ewing sarcoma breakpoint region 1 (EWSR1) encodes a multifunctional protein that can cooperate with the transcription factor ERG to promote prostate cancer. The EWSR1 gene is also commonly involved in oncogenic gene rearrangements in Ewing sarcoma. Despite the cancer relevance of EWSR1, its regulation is poorly understood. Here we find that in prostate cancer, androgen signaling upregulates a 5′ EWSR1 isoform by promoting usage of an intronic polyadenylation site. This isoform encodes a cytoplasmic protein that can strongly promote cell migration and clonogenic growth. Deletion of an Androgen Receptor (AR) binding site near the 5′ EWSR1 polyadenylation site abolished androgen-dependent upregulation. This polyadenylation site is also near the Ewing sarcoma breakpoint hotspot, and androgen signaling promoted R-loop and breakpoint formation. RNase H overexpression reduced breakage and 5′ EWSR1 isoform expression suggesting an R-loop dependent mechanism. These data suggest that androgen signaling can promote R-loops internal to the EWSR1 gene leading to either early transcription termination, or breakpoint formation.

Enzalutamide Induces Cytotoxicity in Desmoplastic Small Round Cell Tumor Independent of the Androgen Receptor

“…A similar process could occur in the DSRCT cell of origin to initiate EWSR1::WT1 translocation. This hypothesis is bolstered by recent findings from Nicholas et al showing that AR binds to introns 5 and 8 of EWSR1 in prostate cancer and further, that R1881 treatment can increase chromosomal breakage at this site in an R-loop dependent manner 31 . In fact, intron 7 of EWSR1, located between the two AR binding sites, is the most common breakpoint location in DSRCT.…”

Identification of Novel/Rare EWSR1 Fusion Partners in Undifferentiated Mesenchymal Neoplasms

“…It has been reported that highly active transcription of the EWSR1 locus could induce the formation of R-loops that in turn favor double-strand breaks. Nicholas et al [29], using prostate cancer cell lines, reported that androgen receptors promoted breakpoint generation in an intronic polyadenylation site of EWSR1 near the Ewing sarcoma breakpoint hotspot, which was dependent on the formation of R-loops. Indeed, persistent R-loops are a direct cause of chromosomal rearrangements [30].…”