Elsevier

Neoplasia

Volume 20, Issue 7, July 2018, Pages 697-709
Neoplasia

BRCA1 Mutation Status and Follicular Fluid Exposure Alters NFκB Signaling and ISGylation in Human Fallopian Tube Epithelial Cells1,2

https://doi.org/10.1016/j.neo.2018.05.005Get rights and content
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open access

Abstract

Germline BRCA1 or BRCA2 mutations (mtBRCA1 and mtBRCA2) increase risk for high-grade serous ovarian cancer (HGSOC), the most commonly diagnosed epithelial ovarian cancer histotype. Other identified risk factors for this cancer, which originates primarily in the distal fallopian tube epithelium (FTE), implicate ovulation, during which the FTE cells become transiently exposed to follicular fluid (FF). To test whether mtBRCA1 or mtBRCA2 nonmalignant FTE cells respond differently to periovulatory FF exposure than control patient FTE cells, gene expression profiles from primary FTE cultures derived from BRCA1 or BRCA2 mutation carriers or control patients were compared at baseline, 24 hours after FF exposure, and 24 hours after FF replacement with culture medium. Hierarchical clustering revealed both FF exposure and BRCA mutation status affect gene expression, with BRCA1 mutation having the greatest impact. Gene set enrichment analysis revealed increased NFκB and EGFR signaling at baseline in mtBRCA1 samples, with increased interferon target gene expression, including members of the ISGylation pathway, observed after recovery from FF exposure. Gene set enrichment analysis did not identify altered pathway signaling in mtBRCA2 samples. An inverse relationship between EGFR signaling and ISGylation with BRCA1 protein levels was verified in an immortalized FTE cell line, OE-E6/E7, stably transfected with BRCA1 cDNA. Suppression of ISG15 and ISGylated protein levels by increased BRCA1 expression was found to be mediated by decreased NFκB signaling. These studies indicate that increased NFκB signaling associated with decreased BRCA1 expression results in increased ISG15 and protein ISGylation following FF exposure, which may be involved in predisposition to HGSOC.

Abbreviations

ACHP
2-amino-6-[2-(cyclopropylmethoxy)-6-hydroxyphenyl]-4-(4-piperidinyl)-3-pyridinecarbonitrile
BRCA1
breast cancer 1, early onset
BRCA2
breast cancer 2, early onset
EGFR
epidermal growth factor receptor
FBS
fetal bovine serum
FDR
false discovery rate
FF
follicular fluid
FTE
fallopian tube epithelium
GO
Gene Ontology
GSEA
gene set enrichment analysis
HGSOC
high-grade serous ovarian cancer
mtBRCA1
BRCA1 mutation
mtBRCA2
BRCA2 mutation

Cited by (0)

1

Funding: This work was supported by the Canadian Institute of Health Research (grant number MOP106679, 2017). J. H. was supported by a Kristi Piia Callum Memorial Fellowship in Ovarian Cancer.

2

Declarations of Interest: None.

3

Contributed equally to the work.

4

Present affiliation: Trillium Health Partners; Mississauga, ON, Canada.

5

Present affiliation: Beaumont Health System; Royal Oak, MI, USA.