TMIC-22. WNT5A promotes angiotropism and perivascular colonization in melanoma brain metastasis

Abstract Melanoma metastasizes hematogenously and exhibits strong tropism for the brain. We previously identified WNT5A as a key regulator of melanoma invasiveness and dormancy in extracranial sites, and we hypothesize that WNT5A similarly promotes melanoma invasion and dormancy within the brain. To investigate, we used experimental brain metastasis models with validation in clinical specimens. WNT5A-overexpression (WNT5A-OE) enhanced transwell migration toward endothelial cell-derived conditioned media and increased endothelial engagement, as quantified by motility coefficient and confinement ratio on live-cell imaging. Adhesion to vascular basal lamina components fibronectin, laminin, and collagen increased with WNT5A-OE. Conversely, WNT5A silencing or integrin β1 blockade attenuated this effect, indicating WNT5A-dependent ligand-receptor interactions. In organotypic brain explant co-cultures, a higher proportion of WNT5A-OE cells localized in the vicinity of vessels within 2 hours after engraftment compared to controls. At 72-hours, WNT5A-OE melanoma exhibited slower growth and perivascular distribution, while WNT5A-silenced cells formed proliferative clusters. Confocal imaging revealed infiltration of WNT5A-OE cells along tissue-penetrating vascular laminin, supporting a role for WNT5A driving invasion and mediating angiotropic interactions. To further assess the impact of the vascular basement membrane on tumor behavior, we cultured FUCCI-transduced melanoma cells on laminin matrices and observed increased G1 cell-cycle arrest and reduced proliferation. Together, these findings suggest that while WNT5A promotes melanoma brain invasion and angiotropism, interactions with extracellular matrix may facilitate tumor quiescence. A clinical correlate was identified in autopsy brain, where singly infiltrative melanoma cells co-opted parenchymal microvasculature adjacent to leptomeningeal spread. Immunohistochemical analyses of surgically resected brain metastatic lesions further revealed close spatial association between invasive melanoma cells and intratumoral vasculature, demonstrated by co-expressions of WNT5A-associated invasive markers (AXL, CD31) in these cells. Ongoing transcriptomic and proteomic profiling of primary and brain metastatic melanoma specimens aims to identify key regulatory and signaling factors that mediate WNT-associated pathways governing dormancy and vascular interaction.