CCND1 and melanoma: The observation that Perk+/- was permissive while Perk-/- was resistant to BrafV600E melanoma, suggested a model where tumors remained dependent upon Perk for its pro-survival activity, but that reduced Perk dosage permitted senescence bypass, through either lack of apoptosis (e.g. reduced CHOP induction) or cyclin D1 induction reflecting reduced inhibition of translation under Perk deficiency.