BMI1 and lymphoma: IC50 and ED50 values of PTC-209 positively correlated with those of PTC596 [r = 0.94 (P = 0.0004) for IC50 and r = 0.85 (P = 0.015) for ED50], respectively, supporting the idea that the anti-lymphoma activities of PTC-209 and PTC596 primarily depend on inhibition of BMI-1 expression.