Estudio de la fase perivascular de la enfermedad metastásica cerebralefecto de la sobreexpresión tumoral de her2 en la regulación del endotelio cerebrovascular por astrocitos

Abstract

Brain metastasis is an important cause of death in patients with advanced cancer, and its development begins in a functional microenvironment regulated by cerebrovascular endothelium (CVD) and astrocytes of the blood-brain barrier (BBB). However, its molecular pathogenesis is largely unknown, and there are no molecular biomarkers alerting us on the risk of suffering brain metastasis, or that might represent good targets for therapy. The aim of the project was to study the neurovascular microenvironment and the growth pattern of brain metastasis and, more specifically, the transcriptional activity and the secretome of the ECV in response to soluble factors from - astrocytes activated by breast cancer cell with or without HER2 overexpression, exposed or not to tumor microenvironment factors. Results showed that initial growth of both experimental and clinical brain metastases occurred in the perivascular space, with the original blood-brain barrier (BHE) being split into two new barriers, an internal hematotumoral (between blood and metastatic tissue), and another external neurotumoral (between metastatic tissue and unaffected brain tissue). Next, in vitro models recapitulating the functional interrelationship operating in the brain metastasis microenvironment among cancer cells, perivascular astrocytes and ECV cells, demonstrated for first time an alteration in gene expression and composition of the ECV secretome induced by tumor-activated astrocytes. More specifically, we showed that the tumor microenvironment (MAT) in conditions of oxygen deprivation (hypoxia), oxidative stress, mechanical stimulation and inflammation, activated the production of astrocyte stimulating factors from Her2-overexpressing tumors, inducing CVE cell passage to a proinflammatory neuro-specific state, defined by increased gene expression of Clau1, Vcam-1 and Pecam-1 (involved in the regulation of intercellular relationships), Vegfr-2, Rage and Col-IV (involved in the regulation of endothelial differentiation) and Pgp (involved in the regulation of transcellular molecular exchanges); and production of a secretome enriched in proteins involved in the processes of neural development, neurovascular and BHE regulation, neuroinflammation, neuroprotection and neurotrophism, neurodegeneration and tumor development. Therefore, we verified the hypothesis raised in the project, and conclude that early metastatic growth in the perivascular microenvironment of the brain altered the function of the astrocytes that regulate the BBB endothelium, contributing the overexpression of Her2 to the functional response of the tumor to the perivascular microenvironment, with respect to regulating CVE via perivascular astrocytes.