Introduction/Background SCCOHT is a rare malignancy affecting young women, with 5-year survival of 10–20%. SCCOHT is caused by inherited and acquired mutations in the SMARCA4 gene, which encodes the BRG1 protein that participates in SWI/SNF chromatin remodeling. There are few established cell-lines and no models of SCCOHT to test new therapeutics.

Methodology We obtained fresh ovarian surface epithelial cells (OSE) from 2 unique cases: 1) A 14-year-old familial carrier of a SCCOHT-associated SMARCA4 mutation (SMARCA4 c.30821+1G>T) who underwent prophylactic bilateral salpingo-oophorectomy, and 2) A 29-year-old with late recurrence of stage IA SCCOHT (SMARCA4 c.189,2dupC). OSE were passaged in vitro. In Case 1, the experiments aimed to determine if the OSE harboring a pathogenic SMARCA4 mutation will spontaneously immortalize. We interrogated loss of contact-dependent inhibition, ability of the cells to grow independently and form spheroids, and measured senescence-associated beta-galactosidase, cell necrosis and apoptosis. Analyses were conducted in parallel with age-matched benign ovarian cyst OSE. In Case 2, Next-Generation Sequencing for a panel of cancer genes, RNAtranscriptome and Nanostring Digital Spatial Profiling (DSP) were performed. Tumour cells in culture were prepared for injection into immunodeficient mice.

Results SMARCA4 mutant ovarian cells were passaged 12 times and continue to proliferate in culture, spontaneously formed foci of multi-cell aggregates and spheroids, while non-mutant control cells failed to propagate and expand (Case 1). In Case 2, the mutant SMARCA4 allele was present in tumor tissue, with a heterozygous germline. There were no additional mutations/gene fusions. Tumor cells were injected subcutaneously in 3 NOD/Scid mice with measurable tumor growth within 4 weeks in all.

Conclusion SMARCA4 mutant cells associated with familial SCCOHT show characteristics of early neoplastic transformation and represent a unique tool to study pathogenesis of SCCOHT. A PDX model of advanced SCCOHT (Case 2) provides a novel tool for developing therapeutic approaches for SCCOHT.