Preliminary control experiments using lymphoma cells from Myc/+;Rosa26-CreERT2/+;Phgdh+/+ mice showed no overt evidence of Cre toxicity (Supplemental Figure 9), but they did show different lymphoma genicity, probably reflecting different cooperating mutations that had evolved to counterbalance the proapoptotic activity caused by enforced Myc expression (49). This evidence concerns the gene MYC and lymphoma.