PRDM1α is a tumor suppressor in cHL. (A) PRDM1α is toxic to cHL cell lines. PRDM1α was ectopically expressed in cHL cell lines using the lentiviral SF-LV-cDNA-EGFP vector. Percentage of live GFP⁺ cells expressing PRDM1α or EV was measured by flow cytometry. Percentage on first day of measurement (day 0) was defined as 100%. The data are shown as mean of 3 independent experiments. P value was determined by a 2-sided Student t test, P < .05. (B) PRDM1α represses MYC in cHL cell lines. L428 and U-HO1 cells were transduced with lentiviral vector expressing PRDM1α or with EV and were sorted 4 to 5 days later. PRDM1α and MYC protein levels were analyzed by immunoblot.