Protein Kinase C Inhibitor AEB071 Targets Ocular Melanoma Harboring GNAQ Mutations via Effects on the PKC/Erk1/2 and PKC/NF-κB Pathways

Abstract

Somatic GNAQ mutations at codon 209 have been identified in approximately 50% of uveal melanomas (UM) and have been reported to be oncogenic through activating PLCβ-PKC-Erk1/2 pathways. We hypothesized that PKC may provide new opportunities for therapeutic targeting of UM carrying GNAQ mutations. To test this hypothesis, UM cells harboring wild type or mutant GNAQ were treated with the PKC inhibitor AEB071 (sotrastaurin) or infected with lentivirus expressing shRNAs targeting PKC isoforms. Notably, AEB071 at low micromolar concentrations significantly inhibited the growth of UM cells harboring GNAQ mutations through induction of G1 arrest and apoptosis. However, AEB071 had little effect on UM cells carrying wild type GNAQ. AEB071-mediated cell inhibition in the GNAQ mutated UM was accompanied by inhibition of Erk1/2 phosphorylation, NF-κB, decreased expression of cyclin D1, survivin, Bcl-xL and XIAP, and increased expression of cyclin-dependent kinase inhibitor p27Kip1. AEB071 suppressed the expression of PKC α, β, δ, ε and θ in GNAQ mutated UM cells. Our findings from shRNA-mediated knockdown studies revealed that these PKC isoforms are functionally important for UM cells harboring GNAQ mutations. Furthermore, inhibitors of Erk1/2 and NF-κB pathways reduced viability of UM cells. Together, our findings demonstrate that AEB071 exerts antitumor action on UM cells carrying GNAQ mutations via targeting PKC/Erk1/2 and PKC/NF-κB pathways. Targeted PKC inhibition with drugs such as AEB071 offers novel therapeutic potential for UM harboring GNAQ mutations.

Dual inhibition of protein kinase C and p53-MDM2 or PKC and mTORC1 are novel efficient therapeutic approaches for uveal melanoma

“…Only www.impactjournals.com/oncotarget a limited efficacy of LEE011 was observed and no clear evidence of increased efficacy combining it with AEB071 was detected, indicating that co-inhibition of PKC and CDK4/6 is not an optimal strategy for treating UM. The absence of increased efficacy after AEB071 + LEE011 combination could be in part explained by the fact that AEB071 decreases expression of cyclin D1 and Rb proteins and induces G1/S cell cycle arrest [16][17] [40], effects that are specific to CDK4/6 targeting.…”

Melanoma: Clinical Features and Genomic Insights

“…Although no treatment targets the G-protein a-subunits directly, targeted therapies directed at protein kinase C (PKC) in uveal melanoma cells harboring a GNAQ mutation inhibited the growth of uveal melanoma via PKC/Erk-1/2 and PCK/NK-kB pathways (Wu et al 2012). Another approach that has been studied in vitro is inhibition of MEK and AKT pathways; MEK inhibitor selumetinib and AKT inhibitor MK2206 decreased cell viability in a synergistic manner and may hold therapeutic promise (Ambrosini et al 2013).…”

Targeting protein kinase C in sarcoma

“…In pre-clinical studies AEB071 has been demonstrated to have at least two separate actions -suppression of autoimmunity and anti-cancer phenotypes. Studies of cancer have focused on uveal melanoma, a rare cancer that commonly has activating mutations of Gα which lead to the activation of PKC/Erk and NF-κB signal transduction, growth and survival [141]. Single agent AEB071 causes melanoma cells to undergo G1 arrest and apoptosis [141] and has synergistic effects with ionising radiation [142], with an inhibitor of PI3K α (BYL719) [143] and the MEK inhibitors PD0325901 and MEK162 [144].…”

“…Studies of cancer have focused on uveal melanoma, a rare cancer that commonly has activating mutations of Gα which lead to the activation of PKC/Erk and NF-κB signal transduction, growth and survival [141]. Single agent AEB071 causes melanoma cells to undergo G1 arrest and apoptosis [141] and has synergistic effects with ionising radiation [142], with an inhibitor of PI3K α (BYL719) [143] and the MEK inhibitors PD0325901 and MEK162 [144]. A number of phase II studies in patients requiring immune modulation (post-organ transplant, plaque psoriasis, uveitis and ulcerative colitis) have established that AEB071 doses of 200-300 mg twice daily are well tolerated but with sufficient followup there was a lack of significant activity as an immunosuppressant [145][146][147].…”