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Monotherapies have proven largely ineffective for the treatment of glioblastomas, suggesting that increased patient benefit may be achieved by combining therapies. Two protumorigenic pathways known to be active in glioblastoma include RAS/RAF/mitogen-activated protein kinase and phosphatidylinositol 3-kinase/AKT/target of rapamycin (TOR). We investigated the efficacy of a combination of novel low molecular weight inhibitors LBT613 and RAD001 (everolimus), which were designed to target RAF and TOR, respectively. LBT613 decreased phosphorylation of extracellular signal-regulated kinase 1 and 2, downstream effectors of RAF, in a human glioma cell line. RAD001 resulted in decreased phosphorylation of the TOR effector S6. To determine if targeting RAF and TOR activities could result in decreased protumorigenic glioma cellular behaviors, we evaluated the abilities of LBT613 and RAD001 to affect the proliferation, migration, and invasion of human glioma cells. Treatment with either LBT613 or RAD001 alone significantly decreased the proliferation of multiple human glioma cell lines. Furthermore, LBT613 and RAD001 in combination synergized to decrease glioma cell proliferation in association with G1 cell cycle arrest. Glioma invasion is a critical contributor to tumor malignancy. The combination of LBT613 and RAD001 inhibited the invasion of human glioma cells through Matrigel to a greater degree than treatment with either drug alone. These data suggest that the combination of LBT613 and RAD001 reduces glioma cell proliferation and invasion and support examination of the combination of RAF and TOR inhibitors for the treatment of human glioblastoma patients. [Mol Cancer Ther 2007;6(9):2449–57]

Glioblastomas are highly lethal cancers that resist current therapies. Novel therapies under development target molecular mechanisms that promote glioblastoma growth. In glioblastoma patient specimens, the non-receptor tyrosine kinase focal adhesion kinase (FAK) is overexpressed. Upon growth factor receptor stimulation or integrin engagement, FAK is activated by phosphorylation on critical tyrosine residues. Activated FAK initiates a signal transduction cascade which promotes glioma growth and invasion by increasing cellular adhesion, migration, invasion, and proliferation. We find that human glioma cell lines express different levels of total FAK protein and activating phosphorylation of tyrosine residues Tyr397, Tyr861, and Tyr925. As all glioma cell lines examined expressed phosphorylated FAK, we examined the efficacy of a novel low-molecular weight inhibitor of FAK, TAE226, against human glioma cell lines. TAE226 inhibited the phosphorylation of FAK as well as the downstream effectors AKT, extracellular signal-related kinase, and S6 ribosomal protein in multiple glioma cell lines. TAE226 induced a concentration-dependent decrease in cellular proliferation with an associated G(2) cell cycle arrest in every cell line and an increase in apoptosis in a cell-line-specific manner. TAE226 also decreased glioma cell adhesion, migration, and invasion through an artificial extracellular matrix. Together, these data demonstrate the potential benefit of TAE226 for glioma therapy.

11505 Background: Glioblastomas are highly lethal cancers that resist current therapies. Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase overexpressed in glioblastoma patient specimens that may promote glioma growth and invasion by increasing cellular adhesion, migration, invasion, proliferation. TAE226 is a novel low molecular weight inhibitor of several kinases that demonstrates in vitro activity primarily against FAK with activity against insulin-like growth factor-1 receptor (IGF1R) at higher concentrations. Methods: As FAK and IGF1R are potential molecular targets in glioblastomas, we examined the efficacy of TAE226 against human glioma cell lines and xenografts. Results: TAE226 inhibited the activating phosphorylation of FAK at submicromolar concentrations with residue specific preference. Downstream effectors (Akt and ERK) were inhibited at slightly higher concentrations. TAE226 demonstrated a concentration-dependent decrease in cellular proliferation with an associated G2 cell cycle arrest in multiple glioma cell lines, whereas TAE226 potently induced apoptosis in a concentration-dependent manner in only one of four cell lines tested. TAE226 also induced a concentration-dependent decrease in cellular adhesion, migration, and invasion. In preliminary animal studies, a limited course of orally administered TAE226 (100 mg/kg qd 5 days on/2 days off/5 days) was well tolerated with minimal weight loss. TAE226 induced a modest growth delay of human glioma xenografts grown in a subcutaneous location in athymic mice (3 to 4 days delay, p < 0.001). In addition, mice bearing orthotopic intracranial human glioma xenografts demonstrated a modest increase in median survival (3.5 days, p = 0.078). Despite the modest degree of the tumor responses, these results are superior to other low molecular weight inhibitors, such as epidermal growth factor receptor (EGFR) inhibitors. As glioma xenografts often grow without invasion, these results may underestimate the efficacy of targeting FAK as FAK plays a major role in tumor invasion. Conclusion: TAE226 demonstrates modest activity as monotherapy against malignant gliomas and warrants further investigation, potentially in combination with other therapies. [Table: see text]