MOB2 suppresses GBM cell migration and invasion via regulation of FAK/Akt and cAMP/PKA signaling

Mps one binder 2 (MOB2) regulates the NDR kinase family, however, whether and how it is implicated in cancer remain unknown. Here we show that MOB2 functions as a tumor suppressor in glioblastoma (GBM). Analysis of MOB2 expression in glioma patient specimens and bioinformatic analyses of public datasets revealed that MOB2 was downregulated at both mRNA and protein levels in GBM. Ectopic MOB2 expression suppressed, while depletion of MOB2 enhanced, the malignant phenotypes of GBM cells, such as clonogenic growth, anoikis resistance, and formation of focal adhesions, migration, and invasion. Moreover, depletion of MOB2 increased, while overexpression of MOB2 decreased, GBM cell metastasis in a chick chorioallantoic membrane model. Overexpression of MOB2-mediated antitumor effects were further confirmed in mouse xenograft models. Mechanistically, MOB2 negatively regulated the FAK/Akt pathway involving integrin. Notably, MOB2 interacted with and promoted PKA signaling in a cAMP-dependent manner. Furthermore, the cAMP activator Forskolin increased, while the PKA inhibitor H89 decreased, MOB2 expression in GBM cells. Functionally, MOB2 contributed to the cAMP/PKA signaling-regulated inactivation of FAK/Akt pathway and inhibition of GBM cell migration and invasion. Collectively, these findings suggest a role of MOB2 as a tumor suppressor in GBM via regulation of FAK/Akt signaling. Additionally, we uncover MOB2 as a novel regulator in cAMP/PKA signaling. Given that small compounds targeting FAK and cAMP pathway have been tested in clinical trials, we suggest that interference with MOB2 expression and function may support a theoretical and therapeutic basis for applications of these compounds.