Modulatory activity of ADNP on the hypoxia-induced angiogenic process in glioblastoma

Glioblastoma multiforme (GBM) is a brain cancer with a poor prognosis that affects adults. This is a solid tumor characterized by a high rate of cell migration and invasion. The uncontrolled cell proliferation creates hypoxic niches in the tumor mass, which leads to the overexpression of hypoxia-inducible factors (HIFs). This induces the activation of the vascular endothelial growth factor (VEGF), which is responsible for uncontrolled neoangiogenesis. Recent studies have demonstrated the anti-invasive effect of pituitary adenylate cyclase-activating peptide (PACAP) in GBM. PACAP effects on the central nervous system are also mediated through the activity-dependent neuroprotective protein (ADNP) activation. To date, no evidence exists regarding its role in GBM. Therefore, the ADNP involvement in GBM was investigated. By analyzing ADNP expression in a human GBM sample through confocal microscopy, a high ADNP immunoreactivity was detected in most glial cells and its predominant expression in hypoxic areas overexpressing HIF-1 alpha was highlighted. To investigate the role of ADNP on the HIF-VEGF axis in GBM, a human U87MG GBM cell line was cultured with a hypoxic mimetic agent, deferoxamine, and cells were treated with the smallest active fragment of ADNP, known as NAP. The protein expression and distribution of HIF-1 alpha and VEGF was detected using western blot analysis and immunofluorescence assay. Results demonstrated that ADNP modulates the hypoxic-angiogenic pathway in GBM cells by reducing VEGF secretion, detected through ELISA assay, as well as modulating their migration, assessed through wound healing assay. Although deeper investigation is necessary, the present study suggested that ADNP could be involved in PACAP anti-invasive effects in GBM.