SAHA (Vorinostat) imparts anti-neoplastic effects against Glioblastoma Multiforme via IGF-1R signaling pathway

Background: Glioblastoma Multiforme (GBM) is the most common primary malignant tumor that arises from astrocytes/glial cells which are known as supportive tissue of brain. GBM is aggressive, highly invasive, angiogenic in nature; however it rarely spreads elsewhere in the body. Median survival time of patients has not improved greatly even after current GBM treatments and demands new targeted therapies to evolve. SAHA; a HDAC inhibitor has been recently identified as a promising candidate to treat various neoplasms including Cutaneous T-cell lymphoma, lung and colon cancers. Hence, SAHA may prove to be a potential drug against highly invasive Glioblastoma. Insufficiency of classical GBM targets like endothelial growth factor receptor (EGFR)/Platelet derived growth factor receptor (PDGFR) in GBM therapy impose necessity of new targets. The Insulin-like growth factor IGFR is a glial growth factor. It is highly overexpressed in most malignant tissues where it functions as an anti-apoptotic agent by enhancing cell survival. It promotes cell proliferation and migration. IGFR also interacts with EGFR and PDGFR. Downregulation of IGF-IR expression or inhibition of its function results in the reversion of the transformed phenotype and massive apoptosis. Inhibition of IGFR by SAHA may prove to be a promising therapy in current scenario of GBM treatment by reversing the classical anti-apoptotic effect of IGF-1R overexpression leading to cell death, growth arrest and ceasing cancer cell proliferation.;Objective: The present study investigated the anti-neoplastic effects of SAHA (HDACi) using U-87MG cell line (Human Primary Glioblastoma cell line) and elucidated probable mechanism of action via IGF1R pathway in GBM.;Methods: U-87MG cells were treated with different doses of SAHA and cell viability was assessed by MTT Assay. Effect of the SAHA on the expression of total-IGF1Rbeta, Akt, Erk and c-Myc in U-87MG cells was determined by western blot analysis. The apoptotic effect was investigated by Caspase-3 calorimetric assay. Wound Healing Assay was performed to evaluate the effect of SAHA on migratory properties of U-87cells. SAHA was also tested in PC-12 cells (neuronal cell model) using MTT assay to validate the selectivity of SAHA towards cancer cells over the normal brain cells.;Results: Results demonstrated that SAHA decreased the U-87MG cell viability as compared to control in a dose dependent manner. SAHA significantly inhibited the overexpression of total IGF1Rbeta, PI3-kinases like Akt, MAPK-kinases like Erk and proto-oncogene c-Myc in a dose dependent manner. Cells treated with SAHA showed increased expression of Caspase-3. In addition to induction of Caspase-3; it showed inhibitory effect on migration of tumor cells treated with SAHA compared to control cancer cells. This cytotoxic effect of SAHA was significantly lower in neuronal PC-12 cells compared to U-87MG cells.;Conclusion: This study evaluated the pharmacological action of SAHA against Glioblastoma Multiforme. Treatment with SAHA showed reduction in viability of Glioblastoma cells (U-87MG) by down-regulating IGF-1R signaling pathway. Hence SAHA can be used as a potential anti-neoplastic agent in Glioblastoma Multiforme either as a single agent or as combination/adjuvant therapy.