Spatial oriented single-cell proteomic assay of low grade serous ovarian carcinoma identifies tumor oncogenic pathways associated with brain metastases (233)

Abstract

Objectives: As the systemic treatment of epithelial ovarian cancer (EOC) has improved, and the survival is longer, the incidence of brain metastases (BM) in EOC patients has increased to about 2-6% and invariably results in death. In order to better understand the molecular mechanisms involved in the development of EOC BM and to characterize the BM architecture and heterogeneity, we recently used multiplex cyclic-immunofluorescence (Cyc-IF) to characterize a set of matched samples from a single ovarian cancer patient. Methods: The samples included a primary tumor, a peritoneal tumor collected at recurrence, and a BM. Cyc-IF is a spatial oriented single-cell proteomic assay that allows the quantification of over 60 proteins in a single FFPE slide. Results: Our analyses indicated that tumor architecture and heterogeneity were highly altered in the BM compared to the primary and recurrent tumors in this patient. Indeed, the primary and recurrent intraperitoneal tumors showed extensive heterogeneity with cancer cells in different cell states related to the cell cycle (cyclins), hormone receptors (PR and ER) and signaling pathways. In contrast, the BM was overall more homogeneous, with no PR receptor expression and low expression of cyclins. EOC cells from the BM harbor higher oncogenic MAPK and PI3K-AKT signaling pathway activity, higher estrogen receptor expression and displayed immunosuppressive properties including increased expression of PD1 and the presence of tumor-associated macrophages (TAM) and regulatory T cells (Tregs). Importantly, we were able to identify cell populations in the primary tumor that had phenotypes similar to that of cells found in the BM. Conclusions: These findings are consistent with the concept that EOC cells with a predilection for BM are present early during the disease course. Therefore, this represents an opportunity to develop a molecular signature for BM prevention and treatment. Objectives: As the systemic treatment of epithelial ovarian cancer (EOC) has improved, and the survival is longer, the incidence of brain metastases (BM) in EOC patients has increased to about 2-6% and invariably results in death. In order to better understand the molecular mechanisms involved in the development of EOC BM and to characterize the BM architecture and heterogeneity, we recently used multiplex cyclic-immunofluorescence (Cyc-IF) to characterize a set of matched samples from a single ovarian cancer patient. Methods: The samples included a primary tumor, a peritoneal tumor collected at recurrence, and a BM. Cyc-IF is a spatial oriented single-cell proteomic assay that allows the quantification of over 60 proteins in a single FFPE slide. Results: Our analyses indicated that tumor architecture and heterogeneity were highly altered in the BM compared to the primary and recurrent tumors in this patient. Indeed, the primary and recurrent intraperitoneal tumors showed extensive heterogeneity with cancer cells in different cell states related to the cell cycle (cyclins), hormone receptors (PR and ER) and signaling pathways. In contrast, the BM was overall more homogeneous, with no PR receptor expression and low expression of cyclins. EOC cells from the BM harbor higher oncogenic MAPK and PI3K-AKT signaling pathway activity, higher estrogen receptor expression and displayed immunosuppressive properties including increased expression of PD1 and the presence of tumor-associated macrophages (TAM) and regulatory T cells (Tregs). Importantly, we were able to identify cell populations in the primary tumor that had phenotypes similar to that of cells found in the BM. Conclusions: These findings are consistent with the concept that EOC cells with a predilection for BM are present early during the disease course. Therefore, this represents an opportunity to develop a molecular signature for BM prevention and treatment.