Aged and BRCA mutated stromal cells drive epithelial cell transformation

The fundamental steps in high-grade serous ovarian cancer (HGSOC) initiation are unclear presenting critical barriers in prevention and early detection of this deadly disease. Current models propose that fallopian tube epithelial (FTE) cells transform into serous tubal intraepithelial carcinoma (STIC) precursor lesions and subsequently HGSOC. Here we report that an epigenetically altered mesenchymal stem cell niche, termed high risk MSC (hrMSC), exists prior to STIC lesion formation. hrMSCs are enriched in STIC stroma and contribute to a stromal 'field effect' extending beyond the borders of STIC lesion. hrMSCs promote DNA damage in FTE cells while also fostering FTE cell survival. hrMSCs induce malignant transformation of FTE resulting in metastatic cancer in vivo, indicating hrMSCs promote cancer initiation. hrMSCs are significantly enriched in BRCA1/2 mutation carriers and increase with age. Combined, these findings indicate that hrMSCs can incite ovarian cancer initiation and have important implications for ovarian cancer detection and prevention. Overall design: FFPE embedded fallopian tube samples were sectioned onto slides. Samples were stained with CD105, CD90, CD73, p53, CD45, and PanCk and processed through the Nanostring GeoMx Digital Spatial Profiler. Using morphology stains, ROI categories were called according to staining combinations. The (v1.0) Human NGS Whole Transcriptome Atlas RNA was used for all samples.