Conversely, the CB1 receptor was identified as having tumor-promoting effects in knockdown models of melanoma, as the CB1-silenced group demonstrated inhibition of ERK and Akt phosphorylation and cell cycle arrest; these findings lead to the hypothesis that CB1 expression alters communication and feedback loops in the endocannabinoid system, mediating the inhibition of migration and proliferation of melanoma cells in vitro [176]. This evidence concerns the gene CNR1 and melanoma.