A role for activated Cdc42 in glioblastoma multiforme invasion

Abstract

Cdc42 is a Rho-GTPase which plays a major role in regulating cell polarity and migration by specifying the localization of filopodia. However, the role of Cdc42 in GBM invasion has not been thoroughly investigated. We generated stable doxycycline-inducible clones expressing wild type (WT)-, constitutively active (CA)-, and dominant negative (DN)-Cdc42 in three different human glioma cell lines. Expression of CA-Cdc42 significantly increased the migration and invasive properties of malignant glioma cells compared to WT and DN-Cdc42 cell clones, and this was accompanied by a greater number of filopodia and focal adhesion structures which co-localize with phosphorylated focal adhesion kinase (FAK). By mass spectrometry and immunoprecipitation studies, we demonstrated that activated Cdc42 binds to IQGAP1. When implanted orthotopically in mice, the CA-Cdc42 expressing glioma cells exhibited enhanced local migration and invasion, and led to larger tumors, which significantly reduced survival. Using the Cancer Genome Atlas dataset, we determined that high Cdc42 expression is associated with poorer progression free survival, and that Cdc42 expression is highest in the proneural and neural subgroups of GBM. In summary, our studies demonstrate that activated Cdc42 is a critical determinant of the migratory and invasive phenotype of malignant gliomas, and that its effect may be mediated, at least in part, through its interaction with IQGAP1 and phosphorylated FAK.

Cytoplasmic cyclin D1 regulates glioblastoma dissemination

“…Of note, the importance of these downstream targets in GBM invasion has also been reported by different authors . For example, in GBM cell lines, loss of FAK inhibits EGF‐induced invasion , whereas Rac1 hyperactivation correlates with an elevated invasive phenotype .…”

Identifying conserved molecular targets required for cell migration of glioblastoma cancer stem cells

“…Of these PDZ genes, plus related genes such as small GTPases with validated functions in border cells 30 , we identified a number of conserved genes whose elevated expression correlated with decreased GBM patient survival. The results presented here, as well as recent results by others, indicate that the small GTPases Cdc42 and Rap1A are needed for the migration of both border cells and GBM CSCs 54,55,57,58 . Further work will be needed to determine the roles, if any, of the additional identified genes on GBM tumor growth, migration, and/or invasion.…”

“…Our results are consistent with recent work by Okura et al 54 , which found that knockdown of Cdc42 by siRNA decreased GBM invasion. Further, constitutively active Cdc42 reduced survival in a PDX model of glioma, while increasing the invasive capacity in sphere exit assays 54 . Thus, high Cdc42 correlates with GBM progression through increased invasion.…”

“…For example, the high-confidence hit LIMK1 is downstream of Rac (human Rac1 and Rac2), which promotes membrane protrusions in migrating cells 49,50 . Similarly, Cdc42 stimulates actinrich protrusions and can polarize migrating cells through direct binding to Par-6 (human PARD6B/PARD6G), one of the strongest hits from the border cell screen 51,52,53 , and has a welldescribed role in GBM invasion 54 .…”

The Role of Rho GTPases in Motility and Invasion of Glioblastoma Cells

“…Findings regarding the role of Rac1 in glioma cell migration and invasion parallel those of Cdc42, for both, promote these two processes, bind to similar domains, are activated by common GEFs, and have the same intracellular location (at the front edge of the cell). High expression of Cdc42 in GBM is correlated with lower survival rates, since it was found to promote the highly invasive characteristics of GBM in vivo [75].…”