Glioblastoma, the most malignant and lethal of brain tumors, remains incurable despite aggressive chemotherapy and surgical interventions. Few new chemotherapeutics for glioblastoma therapy have been explored in preclinical models, and some agents approved for have reached the clinical setting. However success rates are not significant. Previous investigations involving diallyl trisulfide (DATS), a garlic constituent, have indicated significant anti-cancer effects in vitro, including: glioblastoma growth inhibition, extrinsic and intrinsic apoptotic pathway activation, and cell death. DATS has also been shown to inhibit histone deacetylase activity and impede glioblastoma tumor progression. We hypothesized that DATS would block ectopic U87MG induced tumors by inhibiting multiple pro-apoptotic pathways via HDAC. To this end, ectopic tumors were developed in SCID mice and subsequently treated with daily intraperitoneal injections of DATS. Results indicate that a range of DATS doses (10μg/kg-10mg/kg) dose-dependently reduced tumor volume and number of mitotic cells within tumors after seven days. Our histological and biochemical assays demonstrate that DATS reduces mitosis in tumors, decreases HDAC activity, increases in acetylation of H3 and H4, inhibits cell cycle progression, promotes apoptotic cascade activation (m-calpian, Bax, caspase-3) and decreases pro-survival markers (Survivin, Bcl-2, p-Akt, c-Myc, mTOR, EGFR, VEGF). Our data also demonstrates an increase in p21/WAF1 expression, which correlates with increased p53 expression and MDM2 degradation following DATS treatment. Finally, histological assessment and enzyme assays suggest that even the highest dose of DATS administered in this study did not negatively impact hepatic function. These in vivo findings strongly support orthotopic investigation into the therapeutic potential of DATS and further review of the epigenetic mechanisms behind its anti-cancer activities.

Glioblastoma is the most common aggressive, highly glycolytic, and lethal brain tumor. In fact, it is among the most commonly diagnosed lethal malignancies, with thousands of new cases reported in the United States each year. Glioblastoma's lethality is derived from a number of factors including highly active pro-mitotic and pro-metastatic pathways. Two factors increasingly associated with the intracellular signaling and transcriptional machinery required for such changes are anaplastic lymphoma kinase (ALK) and the hepatocyte growth factor receptor (HGFR or, more commonly MET). Both receptors are members of the receptor tyrosine kinase (RTK) family, which has itself gained much attention for its role in modulating mitosis, migration, and survival in cancer cells. ALK was first described as a vital oncogene in lymphoma studies, but it has since been connected to many carcinomas, including non-small cell lung cancer and glioblastoma. As the receptor for HGF, MET has also been highly characterized and regulates numerous developmental and wound healing events which, when upregulated in cancer, can promote tumor progression. The wealth of information gathered over the last 30 years regarding these RTKs suggests three downstream cascades that depend upon activation of STAT3, Ras, and AKT. This review outlines the significance of ALK and MET as they relate to glioblastoma, explores the significance of STAT3, Ras, and AKT downstream of ALK/MET, and touches on the potential for new chemotherapeutics targeting ALK and MET to improve glioblastoma patient prognosis.

Radiation-induced necrosis (RN) is a relatively common side effect of radiation therapy for glioblastoma. However, the molecular mechanisms involved and the ways RN mechanisms differ from regulated cell death (apoptosis) are not well understood. Here, we compare the molecular mechanism of cell death (apoptosis or necrosis) of C6 glioma cells in both in vitro and in vivo (C6 othotopically allograft) models in response to low and high doses of X-ray radiation. Lower radiation doses were used to induce apoptosis, while high-dose levels were chosen to induce radiation necrosis. Our results demonstrate that active caspase-8 in this complex I induces apoptosis in response to low-dose radiation and inhibits necrosis by cleaving RIP1 and RI. When activation of caspase-8 was reduced at high doses of X-ray radiation, the RIP1/RIP3 necrosome complex II is formed. These complexes induce necrosis through the caspase-3-independent pathway mediated by calpain, cathepsin B/D, and apoptosis-inducing factor (AIF). AIF has a dual role in apoptosis and necrosis. At high doses, AIF promotes chromatinolysis and necrosis by interacting with histone H2AX. In addition, NF-κB, STAT-3, and HIF-1 play a crucial role in radiation-induced inflammatory responses embedded in a complex inflammatory network. Analysis of inflammatory markers in matched plasma and cerebrospinal fluid (CSF) isolated from in vivo specimens demonstrated the upregulation of chemokines and cytokines during the necrosis phase. Using RIP1/RIP3 kinase specific inhibitors (Nec-1, GSK'872), we also establish that the RIP1-RIP3 complex regulates programmed necrosis after either high-dose radiation or TNF-α-induced necrosis requires RIP1 and RIP3 kinases. Overall, our data shed new light on the relationship between RIP1/RIP3-mediated programmed necrosis and AIF-mediated caspase-independent programmed necrosis in glioblastoma.

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