Genetic ablation of Prf1 in Cbx3/HP1γ-deficient animals led to uncontrolled B16 melanoma growth and decreased TUNEL positivity indicative of reduced tumor-cell apoptosis (Figures 4SG, H) while NBL tumor burden was incompletely inhibited and tumor-cell death was readily detected (Figures S4I, J). The gene discussed is CBX3; the disease is melanoma.