Lithium inhibits invasion of glioma cells; possible involvement of glycogen synthase kinase-3

Abstract

Therapies targeting glioma cells that diffusely infiltrate normal brain are highly sought after. Our aim was to identify novel approaches to this problem using glioma spheroid migration assays. Lithium, a currently approved drug for the treatment of bipolar illnesses, has not been previously examined in the context of glioma migration. We found that lithium treatment potently blocked glioma cell migration in spheroid, wound-healing, and brain slice assays. The effects observed were dose dependent and reversible, and worked using every glioma cell line tested. In addition, there was little effect on cell viability at lithium concentrations that inhibit migration, showing that this is a specific effect. Lithium treatment was associated with a marked change in cell morphology, with cells retracting the long extensions at their leading edge. Examination of known targets of lithium showed that inositol monophosphatase inhibition had no effect on glioma migration, whereas inhibition of glycogen synthase kinase-3 (GSK-3) did. This suggested that the effects of lithium on glioma cell migration could possibly be mediated through GSK-3. Specific pharmacologic GSK-3 inhibitors and siRNA knockdown of GSK-3alpha or GSK-3beta isoforms both reduced cell motility. These data outline previously unidentified pathways and inhibitors that may be useful for the development of novel anti-invasive therapeutics for the treatment of brain tumors.

The Pivotal Roles of GSK3β in Glioma Biology

“…Recently, 3 independent research groups, including our group, simultaneously reported that GSK3 is a key promoter of malignant GBM phenotypes and is thus a promising candidate for molecular-targeted therapy (Kotliarova et al, 2008;Nowicki et al, 2008;Miyashita et al, 2009a).…”

“…The cytotoxic effects are directly correlated with decreased enzymeactivating phosphorylation of GSK3 (Tyr216) (Kotliarova et al, 2008). Furthermore, specific pharmacologic GSK3 inhibitors and siRNA knockdown of GSK3 reduced glioma cell motility (Nowicki et al, 2008). Importantly, administration of a highly specific GSK3 inhibitor, AR-A014418 (Bhat et al, 2003), at a low dose sensitized GBM cells to chemotherapeutic agents such as temozolomide and ionizing radiation, resulting in reduced cell viability (Miyashita et al, 2009a …”

“…The effects are dose dependent and reversible (Nowicki et al, 2008). However, the mechanisms underlying the effect of GSK3 on glioma cell migration and invasion required further study.…”

“…In contrast, collapse of actin stress fiber formation by the inhibition of RhoA promotes migration (Salhia et al, 2005). As LiCl treatment is associated with a marked change in GBM cell morphology, with cells retracting their long extensions at their leading edge and losing lamellipodia formation (Nowicki et al, 2008), GSK3 signaling may involve small GTPases such as Rac1 and RhoA.…”

“…Recent studies suggest a conflicting role of GSK3 in various human cancers, either as a tumor suppressor or tumor promoter. Emerging evidence suggests that GSK3 is a tumor promoter in glioma, acting to regulate and link key players that control proliferation, resistance to radiochemotherapy, activation of invasion, and anti-apoptosis (Kotliarova et al, 2008;Miyashita et al, 2009a;Nowicki et al, 2008). The combined anti-proliferative and anti-invasive properties of small molecule GSK3 inhibitors make them an attractive treatment modality for controlling GBM.…”