Targeting the MAP kinase pathway in astrocytoma cells using a recombinant anthrax lethal toxin as a way to inhibit cell motility and invasion

Abstract

Malignant astrocytomas are highly invasive into adjacent and distant regions of the normal brain. Understanding and targeting cancer cell invasion is an important therapeutic approach. Cell invasion is a complex process that replies on many signaling pathways including the mitogen-activated protein (MAP) kinase (MAPK). In many cell lines, the use of MAPK-targeted drugs proved to be a potential method to inhibit cancer cell motility. In the present study, we use a recombinant anthrax lethal toxin (LeTx), which selectively inhibits the MAPK pathway, in order to target invasion. LeTx proved ineffective on cell survival in astrocytoma (as well as normal cells). However, astrocytoma cells that were treated with LeTx showed a significant decrease in cell motility as seen by wound healing as well as random 2D motility in serum. The cells also showed a decrease in invasion across a collagen matrix. The effect of LeTx on cell migration was mediated though the deregulation of Rho GTPases, which play a role in cell motility. Finally, the effect of LeTx on cell migration and Rho GTPases was mimicked by the inhibition of the MAPK pathway. In this study, we describe for the first time the effect of the LeTx on cancer cell motility and invasion not cell survival making it a potentially selective brain tumor invasion inhibitor.

Hypoxia and EGF Stimulation Regulate VEGF Expression in Human Glioblastoma Multiforme (GBM) Cells by Differential Regulation of the PI3K/Rho-GTPase and MAPK Pathways

“…Pull-down assays were performed using the RhoACdc42/Rac Activation Assay Combo Kit (Cell BioLabs) as previously described [65] and following the manufacturer’s instructions. Briefly, cell lysates were incubated with GST-RBD (Rhotekin binding domain) for 1 h at 4 °C with gentle agitation.…”

The Role of Rho GTPases in VEGF Signaling in Cancer Cells

“…Finally, we noticed the complexity and interconnectedness between VEGF and Rho-related pathways which benefit cancer cells in multiple aspects which include but are not limited to angiogenesis, migration, and invasion. Due to the complications associated with the untargeted cancer therapies (chemo-and radiotherapy), approaches targeting specific characteristics and pathways of tumors must be explored [80,[125][126][127][128][129]. Therefore, targeting these interaction factors that are produced and secreted by the tumor cells might exhibit promising therapeutic potential.…”

“…Our lab has further demonstrated that targeting the MAP kinase pathway in astrocytoma cells by using a recombinant anthrax lethal toxin inhibits cell motility and invasion by deregulating the Rho GTPases. In this context, cells treated with the toxin revealed a higher density of stress fibers, potentially indicating an increase in the activity of RhoA [80]. Upon inspection, treated cells did in fact exhibit a higher expression of activated RhoA as well as a higher tendency to adhere properly [80].…”

“…In this context, cells treated with the toxin revealed a higher density of stress fibers, potentially indicating an increase in the activity of RhoA [80]. Upon inspection, treated cells did in fact exhibit a higher expression of activated RhoA as well as a higher tendency to adhere properly [80].…”

Recombinant anthrax lethal toxin inhibits cell motility and invasion in breast cancer cells through the dysregulation of Rho GTPases

“…For example, several studies have shown that melanoma cells that carry N-Ras mutations are not sensitive to the LF-mediated inhibition of the MAPK pathway, while those carrying a V600E B-Raf mutation are sensitive to the inhibition of this pathway (25,27). Previously, it was also demonstrated that LeTx successfully decreased cellular motility and invasion of glioblastoma cells by increasing their adhesion via an increase in RhoA activity (28).…”