c-Src inhibitors pyrozolo[3,4-d]pyrimidines, Si306 and pro-Si306, evade multidrug resistant phenotype and suppress invasion in glioblastoma

Abstract

Background: Glioblastoma multiforme (GBM) are the most frequent and aggressive (WHO grade IV) brain tumors in adults. GBM have high expression of c-Src tyrosine kinase involved in survival, migration and invasiveness of tumor cells. Thus, c-Src emerged as a potential target for GBM therapy. Materials and methods: Antiproliferative effect of c-Src inhibitors pyrozolo[3,4-d] pyrimidines, Si306 and its prodrug pro-Si306, was assessed in human GBM cell line U87, multidrug resistant (MDR) U87-TxR, and primary GBM cells by MTT assay. Anti-migratory and anti-invasive effects of c-Src inhibitors were evaluated by gelatin degradation and transwell invasion assays. Their effect on c-Src, extracellular signal-related kinase (ERK), and focal adhesion kinase (FAK) expression was analyzed by western-blot and flow-cytometry. Zebrafish model was used to evaluate anti-invasive potential of pro-Si306 in U87 xenografts in vivo. Results and conclusions: c-Src inhibitors were more efficient in cell growth inhibition compared to dasatinib, a well-known tyrosine kinase inhibitor. The potency of Si306 and pro-Si306 was not affected by the MDR phenotype. Migratory potential of U87, U87-TxR, and primary GBM cells was significantly decreased by both inhibitors. Si306 and pro-Si306 also compromised cells’ ability to degrade the matrix and invade through basement membrane. Both compounds reduced phosporylation of c-Src, and its downstream signaling components, ERK and FAK, in GBM cell lines. In vivo, pro-Si306 showed anti-invasive effect against U87 xenografts in zebrafish model. Considering their ability to suppress migration and invasion and overcome MDR, Si306 and pro-Si306 could be considered in GBM treatment alone or in combination with other chemotherapeutics.