BRCA2 abrogation triggers innate immune responses potentiated by treatment with PARP inhibitors

Timo Reisländer,Madalena Tarsounas,Benjamin Wright,Florian J Groelly,Serena Di Vito,Arturo Londoño-Vallejo,Ana Miar,Manuela Porru,Helen Lockstone,Emilia Puig Lombardi,Adrian Harris,Annamaria Biroccio

doi:10.1038/s41467-019-11048-5

Abstract

Heterozygous germline mutations in BRCA2 predispose to breast and ovarian cancer. Contrary to non-cancerous cells, where BRCA2 deletion causes cell cycle arrest or cell death, tumors carrying BRCA2 inactivation continue to proliferate. Here we set out to investigate adaptation to loss of BRCA2 focusing on genome-wide transcriptome alterations. Human cells in which BRCA2 expression is inhibited for 4 or 28 days are subjected to RNA-seq analyses revealing a biphasic response to BRCA2 abrogation. The early, acute response consists of downregulation of genes involved in cell cycle progression, DNA replication and repair and is associated with cell cycle arrest in G1. Surprisingly, the late, chronic response consists predominantly of upregulation of interferon-stimulated genes (ISGs). Activation of the cGAS-STING-STAT pathway detected in these cells further substantiates the concept that BRCA2 abrogation triggers cell-intrinsic immune signaling. Importantly, we find that treatment with PARP inhibitors stimulates the interferon response in cells and tumors lacking BRCA2.

Highlights

Heterozygous germline mutations in BRCA2 predispose to breast and ovarian cancer
BRCA2 expression was effectively suppressed by DOX exposure in the short term (4 days), as well as in the long-term (28 days), as indicated by immunoblotting of cell extracts prepared at these time points (Fig. 1b)
Consistent with the concept that cGAS-STING activation and interferon signaling triggers JAK/STAT-dependent gene expression, we found that siRNA-mediated STAT1 depletion decreased the mRNA levels of interferon-stimulated genes (ISGs) (Supplementary Fig. 9c)

Summary

Introduction

Heterozygous germline mutations in BRCA2 predispose to breast and ovarian cancer. Contrary to non-cancerous cells, where BRCA2 deletion causes cell cycle arrest or cell death, tumors carrying BRCA2 inactivation continue to proliferate. BRCA2 tumor suppressor plays key roles in cell physiology by promoting DNA replication and DNA double-strand breaks (DSBs) repair via homologous recombination[1]. The latter is well-characterized biochemically and relies on BRCA2 loading the RAD51 recombinase at sites of DSBs that have been processed by resection. In the long-term, we find that cell cycle reentry occurs concomitantly with ISG upregulation These are genes involved in the innate immune response and controlled by interferon signaling[14]. An ISG subset is upregulated in BRCA2deleted primary ovarian tumors These results support the concept that inducible BRCA2 inactivation in cultured cells recapitulates cellular changes associated with loss of BRCA2 during tumorigenesis and could provide clues to mechanisms of cellular adaptation in tumors or tumor vulnerabilities. Treatment with PARP inhibitors (olaparib, talazoparib) stimulates upregulation of the interferon signaling genes in vitro and in vivo

Methods

Results

Conclusion