In uveal melanoma Gα-protein GNA11 mutations convey a shorter disease-specific survival and are more strongly associated with loss of BAP1 and chromosomal alterations than Gα-protein GNAQ mutations

Mutations in the Gα-genes GNAQ and GNA11 are found in 85-90% of uveal melanomas (UMs). We analyzed the association between GNAQ and GNA11 mutations with disease-specific survival, gene expression profiles, and cytogenetic alterations in 219 UMs. Our analysis showed a shorter disease-specific survival of GNA11-mutated cases as compared to those carrying a GNAQ mutation (HR=1.97 [95%CI 1.12-3.46], p=0.02). GNA11 mutated UMs displayed a shorter, but not significant, median months survival of 26.97 [95% CI 25.02-37.08] versus GNAQ patients median months survival of 31.5 [95% CI 30.97-53.51]. The GNA11 mutation was also associated with: i) an increased frequency of loss of BRCA1-associated protein 1 (BAP1) expression (p=0.0005), ii) monosomy of chromosome 3 (p<0.001), iii) amplification of chr8q (p=0.038), iv) the combination of the latter two (p=0.0002), and inversely with v) chr6p gain (p=0.003). We used tandem-affinity-purification and mass spectrometry to show that the two derived G-proteins have different protein interaction partners. Specifically, the Tet Methylcytosine Dioxygenase 2(TET2), a protein that is involved in DNA demethylation, physically interacts with the GNAQ protein but not with GNA11, as confirmed by immunoprecipitation analyses. High-risk UM cases show a clearly different DNA-methylation pattern, suggesting that a different regulation of DNA methylation by the two G-proteins might convey a different risk of progression. Eight different uveal melanoma cell lines MEL285, MEL290, OMM1, UPMM1, UPMM2, UPMM3, UPMD1, and UPMD2 (wild type or specifically mutated for GNAQ or GNA11 as indicated in the main text) were selected as cellular model for the α- protein signaling analysis. Cell were analyzed in triplicate