Abstract LB311: Multimodal spatial profiling reveals the emergence of an immune suppressive microenvironment at the initial stages of high-grade serous ovarian cancer development

Abstract Introduction: Despite the clear genetic evidence linking serous tubal intraepithelial carcinoma (STIC) and high-grade serous ovarian carcinoma (HGSOC), the specific conditions and events that promote the progression of STIC lesions into invasive disease remain poorly understood. Method: As a critical initial step, we have assembled a cohort of incidental p53 signatures, STIC lesions, and STIC with concurrent HGSOC. We have performed extensive multi-modal analysis using multiplexed tissue imaging and spatial transcriptomics that identify features of the immune system that play a vital role in the early steps of HGSOC development. We have processed 43 specimens using highly multiplexed tissue imaging at single-cell resolution (cyclic immunofluorescence, CyCIF), and 35 specimens for micro-regional spatial transcriptomics using the GeoMx (Whole Transcriptome, Nanostring) on over 450 pathologist-annotated regions of interest. Results: Our data suggests an immune-cold environment and T-cell dysfunction in STIC lesions, including incidental STIC. One of the significant immune populations identified was CD103+ tissue-resident memory T cells (TRM). In incidental p53 signatures, activation of TRM was rare, similar to FT, which may indicate the absence of sensing “tumor antigen” by these TRM. CyCIF analysis also revealed that most incidental STIC lesions (7/9 cases) overexpress major histocompatibility complex (MHC) class I compared to the normal epithelium, especially both HLA complex, HLA-A and HLA-E. Most STICs showed extensive intra-lesion heterogeneity, with some STICs remaining HLA-A and HLA-E negative. Incidental p53 signatures, on the other hand, were mostly HLA-A and HLA-E negative and, when positive, had only a few cells expressing HLA. We hypothesized that there might be a natural selection of HLA-E-positive clones as STICs progress to HGSOC. Consistent with this, HGSOC showed further overexpression of HLA-E. However, HLA-E heterogeneity was still observed in the invasive tumor, with both positive and negative clones co-existing. Geomx data suggested that the interferon signaling pathway is upregulated in the epithelial of HLA-E positive STIC and cancer clones compared to HLA-E negative clones. In turn, both HLA-A and HLA-E might be overexpressed in the epithelial of HLA-E-positive STICs. Overall, we showed that the response in interferon (IFN) α and γ, NF-KB, and IL-6-induced STAT-3 pathways were upregulated in both STIC lesions and carcinoma. The role of these pathways, especially STAT-3 pathway, has been shown in other aneuploid cancers in promoting immune escape, cell proliferation and migration, chemoresistance and inhibiting apoptosis. We have shown the co-localization of cGAS and BAF, a marker for micronuclei rupture, by super-resolution 3D imaging to confirm one of the mechanisms of IFN activation. Conclusion: Taken together, these data may indicate chromosomal instability is one of the mechanisms that is driving the IFN-signaling pathway and, hence, a potential selective advantage for HLA-E-positive clones in tumorigenesis, leading to inhibiting NK cell surveillance followed by reducing T cell infiltration. Citation Format: Tanjina Kader, Jia-Ren Lin, Shannon Coy, Clemens Hug, Yu-An Chen, Roxanne J. Pelletier, Mariana Leon, John Lee, Yi-Lin Xu, Clarence Yapp, Natalie Shih, Gabriel Mingo, Euihye Jung, Srishti Rathore, Judith Agudo, Charles Drescher, Peter K. Sorger, Ronny Drapkin, Sandro Santagata. Multimodal spatial profiling reveals the emergence of an immune suppressive microenvironment at the initial stages of high-grade serous ovarian cancer development abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (7Suppl): Abstract nr LB311.