Concurrent activation of ?2-adrenergic receptor and blockage of GPR55 disrupts pro-oncogenic signaling in glioma cells.

ABSTRACT: Activation of ?2-adrenergic receptor (?2AR) and deorphanized GPR55 has been shown to modulate cancer growth in diverse tumor types in vitro and in xenograft models in vivo. (R,R')-4'-methoxy-1-naphthylfenoterol [(R,R')-MNF] is a bivalent compound that agonizes ?2AR but inhibits GPR55-mediated pro-oncogenic responses. Here, we investigated the molecular mechanisms underlying the anti-tumorigenic effects of concurrent ?2AR activation and GPR55 blockade in C6 glioma cells using (R,R')-MNF as a marker ligand. Our data show that (R,R')-MNF elicited G1-phase cell cycle arrest and apoptosis, reduced serum-inducible cell motility, promoted the phosphorylation of PKA target proteins, and inhibited constitutive activation of ERK and AKT in the low nanomolar range, whereas high nanomolar levels of (R,R')-MNF were required to block GPR55-mediated cell motility. siRNA knockdown and pharmacological inhibition of ?2AR activity were accompanied by significant upregulation of AKT and ERK phosphorylation, and selective alteration in (R,R')-MNF responsiveness. The effects of agonist stimulation of GPR55 on various readouts, including cell motility assays, were suppressed by (R,R')-MNF. Lastly, a significant increase in phosphorylation-mediated inactivation of ?-catenin occurred with (R,R')-MNF, and we provided new evidence of (R,R')-MNF-mediated inhibition of oncogenic ?-catenin signaling in a C6 xenograft tumor model. Thus, simultaneous activation of ?2AR and blockade of GPR55 may represent a novel therapeutic approach to combat the progression of glioblastoma cancer.

SUBMITTER: Wnorowski A 

PROVIDER: S-EPMC5512002 | biostudies-literature | 2017 Aug

REPOSITORIES: biostudies-literature