Oncogenic FOXL2C134W has gain-of-function chromatin remodeling activity that reprograms glucocorticoid receptor occupancy to promote ovarian granulosa cell tumor growth

Adult type ovarian granulosa cell tumors (AGCTs) are rare malignancies with near universal somatic mutation c.C402G (p.Cys134Trp) in FOXL2, a forkhead box-family transcription factor important for ovarian function. Relapsed AGCT is incurable and the mechanism of the unique FOXL2 mutation remains incompletely understood. To identify FOXL2C134W-dependent pharmacologic synergies, we created and characterized endogenous FOXL2 isogenic AGCT cells and an AGCT tumoroid biobank. A drug screen identified that glucocorticoids promote FOXL2C134W-dependent AGCT growth. Epigenetic investigation revealed that the Cys134Trp mutation exposes latent DNA sequence-specific pioneering activity in FOXL2, a unique oncogenic mechanism. FOXL2C134W pioneering activity redirects glucocorticoid receptor chromatin occupancy to drive hyaluronan synthase 2 gene expression and increase extracellular hyaluronan secretion. Treatment of AGCT models with hyaluronidase reduces viability and this effect can be rescued by dexamethasone. Thus, gain-of-function pioneering activity contributes to the oncogenic mechanism of FOXL2C134W and creates a potentially targetable synergy with glucocorticoid signaling.

Type: Cancer Genomics
Archiver: European Genome-Phenome Archive (EGA)

1 Dataset

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Dataset ID	Description	Technology	Samples
EGAD50000000880	This dataset contains bam files from the whole exome sequencing performed on granulosa cell tumors and 7 sequencing experiments performed on human-derived KGN granulosa cell tumor cells and isogenic cell lines. The latter include transcription factor ChIP-seq for Foxl2 as well as transcription factor ChIP-seq for Foxl2 and GR under dexamethasone treatment and untreated conditions, two ATAC-seq data sets, two RNA-seq data sets, and Histone marks ChIP-seq.	Illumina NovaSeq 6000 NextSeq 500	133