# Proangiogenic Properties of Extracellular Vesicles Secreted by Endothelial Cells Reversibly Primed for Anoikis: A Possible Autocrine Mechanism Induced by Astrocytoma Extracellular Matrix

## TL;DR

Tumor extracellular matrix causes endothelial cell death but also triggers pro-angiogenic signals through extracellular vesicles, possibly aiding tumor growth.

## Contribution

Discovery of an EV-mediated autocrine mechanism linking tumor ECM-induced endothelial apoptosis to proangiogenic effects.

## Key findings

- Apoptotic endothelial cells attract and guide migrating endothelial cells through extracellular vesicles.
- EVs from tumor-ECM-stimulated cells enhance TDEC migration but not those from TN-C-depleted matrices.
- TDECs undergo metabolic and structural reprogramming, including upregulation of glycolytic enzymes and vesicle-trafficking regulators.

## Abstract

Altered extracellular matrix (ECM), a hallmark of solid tumors, affects cellular survival, migration and differentiation. Typically viewed as tumor-suppressive, evidence suggests that apoptosis can also generate pro-tumoral signals. We previously showed that ECM from high-grade astrocytomas induces extensive endothelial anoikis, while a surviving subpopulation fails to form tubular structures (tubulogenesis-defective endothelial cells, or TDECs). We combined functional assays with whole-cell proteomics to investigate this response. Using real-time video microscopy, we found that apoptotic endothelial cells induced by tumor ECM attracted migrating endothelial cells and guided sprouting. Conditioned media from apoptotic endothelial cells contained a 2.8-fold increase in extracellular vesicles (EVs) relative to autologous ECM-primed endothelial cells. Although both EV populations improved TDEC tubulogenesis, only EVs produced upon tumor-ECM stimulation induced TDEC migration—a property lost when using EVs secreted by endothelial cells growing on TN-C-depleted matrices. Proteomic profiling revealed that TDECs shift from an adhesion-anchored to a microtubule-rich and glycolytically rewired phenotype, with upregulation of vesicle-trafficking regulators (ARF1/3/4, ANXA2/5), migration drivers (RAC1/3, RHOA/C, WDR1, FSCN1) and glycolytic enzymes (ENO1, ALDOA, PKM, LDHA), alongside the suppression of integrin- and cytoskeletal-anchoring proteins. Collectively, these findings indicate that tumor-ECM-driven endothelial apoptosis generates reversible reprogramming and an EV-mediated autocrine mechanism that may favor angiogenic balance.