Anales RANF

S12-04 CONFLICTING EFFECTS OF GUANOSINE, GUANINE AND THEIR METABOLIZING ENZYMES ON NEUROPROTECTION AND TUMOR CELL PROLIFERATION Zuccarini M 1 , Giuliani P 1 , Carluccio M 1 , D’Orazio A 1 , Ciccarelli R 1 , Caciagli F 1 and Di IorioP 1 1 “G. d’Annunzio” University of Chieti-Pescara, Chieti, Italy Guanine-based purines and their converting enzymes stand out as key player in cell metabolism and in signaling pathways involved in neurodegenerative disorders and cancer. Guanosine (GUO) and guanine (GUA) are extracellular signaling molecules derived from the breakdown of GTP. GUA is generated from GUO in a reaction catalyzed by the purine nucleoside phosphorylase (PNP). Since several polymorphisms in the PNP gene as well as epigenetic mechanisms involving microRNAs expression have been reported in tumors, we investigated whether GUO-PNP-GUA system affected the expression of several markers involved in glioma cell proliferation and metastasis. To this aim, human glioma cell lines U87 were transfected with miR-200b or miR-133a mimics, and evaluated for EGFR, ZEB1, SNAIL, α -SMA, Fibronectin and PNP mRNA expression levels. GUA, but not GUO, dose-dependently inhibited glioma cell proliferation and triggered a moderate up- regulation of Fibronectin, α -SMA, PNP and EGFR. A different trend was observed for ZEB1 and SNAIL expression. The hyper-phosphorylation of EGFR was restrained by a GUA-induced and AMPK1-mediated ubiquitination leading to receptor degradation. The administration of miR-200b or miR-133a in association with GUA reduced the effects caused by GUA alone on marker expression. Moreover, cell pre-treatment with a selective PKG inhibitor, KT5823, reverted GUA-mediated effects, suggesting the involvement of this kinase in GUA-evoked signaling. Collectively, our data demonstrated that GUO activity is aimed at producing neuroprotective effects, whereas the nucleobase GUA inhibits the proliferation of glioma cells. Importantly, as glioma progression is driven by aberrant signaling of growth factor receptors such as EGFR, GUA, alone or in association with EGFR targeted therapies, might be a promising antitumor therapeutic tool.