Eleonora Y. Khlebus

Multiplexed Imaging Mass Cytometry Reveals Tumor-immune Microenvironment–dependent Hormone Receptor Expression in Adult-Type Ovarian Granulosa Cell Tumors

Abstract Adult-type granulosa cell tumors (AGCT) are rare ovarian tumors with few effective treatments for recurrent disease. To elucidate spatial features and cellular interactions within the AGCT tumor microenvironment, we applied imaging mass cytometry using a 34-marker panel on 130 regions from 24 AGCT samples, profiling more than 900,000 single cells. Analysis confirmed the immune “cold” phenotype of AGCTs and showed higher macrophage abundance in recurrent compared with primary tumors. We observed substantial heterogeneity in tissue architecture across samples, including variable presence of FOXL2+ cells embedded in collagen-rich regions (FOXL2+COL1A1+ cells). Based on tumor microenvironment composition, we defined two AGCT subtypes: AGCT-1 and AGCT-2 with distinct FOXL2+ cell distributions, differences in progesterone receptor expression, and unique transcriptomic profiles. Our findings highlight the role of macrophages, Foxl2+ subpopulations, and the extracellular matrix in AGCT progression and suggest AGCT subtype–specific vulnerabilities that could inform personalized therapies for this rare malignancy. Significance: We discovered two histologically and molecularly distinct forms of AGCTs that differ in cell composition, immune activity, and hormone signals. These findings point to new opportunities for more personalized treatment of this rare ovarian cancer.

Comparative Tumor Microenvironment Analysis of Primary and Recurrent Ovarian Granulosa Cell Tumors

Abstract Adult-type granulosa cell tumors (aGCT) are rare ovarian sex cord tumors with few effective treatments for recurrent disease. The objective of this study was to characterize the tumor microenvironment (TME) of primary and recurrent aGCTs and to identify correlates of disease recurrence. Total RNA sequencing (RNA-seq) was performed on 24 pathologically confirmed, cryopreserved aGCT samples, including 8 primary and 16 recurrent tumors. After read alignment and quality-control filtering, DESeq2 was used to identify differentially expressed genes (DEG) between primary and recurrent tumors. Functional enrichment pathway analysis and gene set enrichment analysis was performed using “clusterProfiler” and “GSVA” R packages. TME composition was investigated through the analysis and integration of multiple published RNA-seq deconvolution algorithms. TME analysis results were externally validated using data from independent previously published RNA-seq datasets. A total of 31 DEGs were identified between primary and recurrent aGCTs. These included genes with known function in hormone signaling such as LHCGR and INSL3 (more abundant in primary tumors) and CYP19A1 (more abundant in recurrent tumors). Gene set enrichment analysis revealed that primarily immune-related and hormone-regulated gene sets expression was increased in recurrent tumors. Integrative TME analysis demonstrated statistically significant depletion of cancer-associated fibroblasts in recurrent tumors. This finding was confirmed in multiple independent datasets. Implications: Recurrent aGCTs exhibit alterations in hormone pathway gene expression as well as decreased infiltration of cancer-associated fibroblasts, suggesting dual roles for hormonal signaling and TME remodeling underpinning disease relapse.

Gain-of-Function Chromatin Remodeling Activity of Oncogenic FOXL2C134W Reprograms Glucocorticoid Receptor Occupancy to Drive Granulosa Cell Tumors

Abstract Adult type ovarian granulosa cell tumors (AGCT) are rare malignancies with the near universal c.C402G (p.Cys134Trp) somatic mutation in FOXL2, a forkhead box family transcription factor important for ovarian function. Relapsed AGCT is incurable, but the mechanism of the unique FOXL2 mutation could confer therapeutic vulnerabilities. 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 chromatin remodeling activity in FOXL2. FOXL2C134W-dependent chromatin remodeling activity redirected glucocorticoid receptor chromatin occupancy to drive hyaluronan synthase 2 gene expression and increase extracellular hyaluronan secretion. Treatment of AGCT models with hyaluronidase reduced viability, and dexamethasone rescued this effect. Combinatorial drug–drug interaction experiments demonstrated that dexamethasone antagonizes the potency of paclitaxel, a chemotherapy agent frequently used in the treatment of AGCT. Thus, gain-of-function pioneering activity contributes to the oncogenic mechanism of FOXL2C134W and creates a potentially targetable synergy with glucocorticoid signaling. Significance: Glucocorticoids promote granulosa cell tumor growth via epigenetic coregulation with the disease driver FOXL2C134W, providing mechanistic insight into disease oncogenesis and uncovering a potential treatment strategy.