Somatic GNAQ mutations at
codon 209 have been identified in approximately 50% of uveal
melanomas and have been reported to be oncogenic through activating PLCβ/PKC/Erk1/2 pathways. We hypothesized that
protein kinase C (PKC) may provide new opportunities for therapeutic targeting of
uveal melanoma carrying GNAQ mutations. To test this hypothesis,
uveal melanoma cells harboring wild-type or mutant GNAQ were treated with the PKC inhibitor
AEB071 (
sotrastaurin) or infected with lentivirus-expressing short hairpin RNAs (
shRNA) targeting PKC
isoforms. Notably,
AEB071 at low micromolar concentrations significantly inhibited the growth of
uveal melanoma cells harboring GNAQ mutations through induction of G(1) arrest and apoptosis. However,
AEB071 had little effect on
uveal melanoma cells carrying wild-type GNAQ. AEB071-mediated cell inhibition in the GNAQ-mutated
uveal melanoma was accompanied by inhibition of
extracellular signal-regulated kinase (Erk)1/2 phosphorylation, NF-κB, decreased expression of
cyclin D1,
survivin, Bcl-xL, and XIAP, and increased expression of
cyclin-dependent kinase inhibitor p27(Kip1).
AEB071 suppressed the expression of PKC α, β, δ, ε, and θ in GNAQ-mutated
uveal melanoma cells. Our findings from
shRNA-mediated knockdown studies revealed that these PKC
isoforms are functionally important for
uveal melanoma cells harboring GNAQ mutations. Furthermore, inhibitors of Erk1/2 and NF-κB pathways reduced viability of
uveal melanoma cells. Together, our findings show that
AEB071 exerts antitumor action on
uveal melanoma 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
uveal melanoma harboring GNAQ mutations.