Abstract 2591: The interaction of pericytes and brain metastasizing cancer cells in the <i>in vitro</i> co-culture system

Abstract Introduction: Brain metastasis significantly reduces the patients’ quality of life and survival, but there are only a few choices of treatment for brain metastasis. The research for brain metastasis is difficult because of its complex and unique microenvironment, including blood-brain barrier (BBB). As the role of pericytes in maintaining the BBB function has become clearer, the reconstituted models of the BBB in which endothelial cells (ECs), pericytes, and astrocytes are seeded on the front and back of the insert membrane have gotten our attention. We previously applied a reconstituted BBB model (Ito R, et al. Mol Pharm 2019) to develop a co-culture system for the evaluation of brain metastatic cells. This in vitro brain metastasis model mimics the brain vascular microenvironment, and successfully reproduces the invasive ability of brain metastatic cell lines. In this study, we figured out the role of pericytes in promoting cancer invasion and elucidated the interaction between pericytes and metastasizing cancer cells. Methods: Using our in vitro co-culture system, we compared the migration ability of MDA231 and Ex3LL in several BBB models: EPA model (ECs, pericytes, and astrocytes), E0A model (ECs and astrocytes), EP0 model (ECs and pericytes), and E00 model (ECs only). To figure out how pericytes promote the migration of Ex3LL, we analyzed the morphology, transcriptome and migration ability of the parental and brain metastatic (BrM) cell lines of Ex3LL with and without pericytes. Results: Though the migration of MDA231 was inhibited when co-cultured with pericytes or astrocytes, the migration of Ex3LL was promoted by the co-culture with pericytes. BrM cells of Ex3LL showed further increased migration ability when co-cultured with pericytes, compared to the parental cells. The transcriptome analysis of BrM cells of Ex3LL showed upregulated signaling pathway of the cell-cell and cell-matrix interactions, which implied the direct interaction between pericytes and cancer cells. The migration analysis using EP0 model (pericytes were seeded on the back of the insert membrane and had a direct interaction with cancer cells) and E0P model (pericytes were seeded on the bottom surface of the well and only secreted factors affected the cancer cells), also suggested the direct interaction of pericytes promoting the migration of Ex3LL. Conclusion: Using our BBB reconstituted model, we showed that the role of pericytes in promoting cancer invasion depended on cancer cell types. Our results suggested that the direct interaction between pericytes and cancer cells, and assumedly ECs, was indispensable for the mechanism in which pericytes promote the Ex3LL migration. We need further investigation to elucidate the molecular mechanism underlying the interaction between pericytes and brain metastasizing cancer cells. Citation Format: Shoko Noda-Narita, Atsu Aiba. The interaction of pericytes and brain metastasizing cancer cells in the in vitro co-culture system [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 2591.