McMullen, T. P. | Search bioRxiv

bioRxiv2025

PHLDA2 promotes breast cancer metastasis by co-opting a developmental program for placental vascular remodeling

Identifying drivers of metastasis is essential for developing new treatments for patients with advanced disease. Here, we identify PHLDA2 as a robust driver of breast cancer metastasis. Previous work established PHLDA2 as an imprinted gene expressed by trophoblasts which are critical for vascular remodeling during placental development. We find that hypomethylation of PHLDA2 in breast tumors correlates with increased gene expression, which is associated with metastasis and poor survival in breast cancer patients. RNA-sequencing showed that PHLDA2 overexpression results in upregulation of genes that control invasion, extracellular matrix assembly, and vascular remodeling, consistent with trophoblast functions in placental development. Using an in vitro vascularized microtumor (VMT) system, we find that PHLDA2 functions through SPARC, which promotes metastasis by inducing vascular permeability and enhancing tumor dissemination. These data suggest that increased expression of PHLDA2 through hypomethylation promotes metastasis by ectopic expression of a developmental program for vascular remodeling.

cancer biology↗

bioRxiv2024

Microglia are not required for maintenance of blood-brain barrier properties in health, but PLX5622 alters brain endothelial cholesterol metabolism

Microglia are resident immune cells of the central nervous system, yet their functions far exceed those related to immunology. From pruning neural synapses during development to preventing excessive neural activity throughout life, microglia are intimately involved in the brains most basic processes. Studies have reported a close interaction between microglia and endothelial cells, as well as both helpful and harmful roles for microglia at the blood-brain barrier (BBB) in the context of disease. However, much less work has been done to understand microglia-endothelial cell interactions in the healthy brain. Here, we aim to determine the role of microglia at the healthy BBB. We used the colony-stimulating factor 1 receptor (CSF1R) inhibitor PLX5622 to deplete microglia and analyzed BBB ultrastructure, permeability, and transcriptome. Interestingly, we found that, despite their direct contact with endothelial cells, microglia are not necessary for maintenance of BBB structure, function, or gene expression in the healthy brain. However, we found that PLX5622 treatment alters brain endothelial cholesterol metabolism, and this effect was independent from microglial depletion, suggesting PLX5622 has off-target effects on brain vasculature.

neuroscience↗