The mechanism of action of TGF-β in centroblasts and Burkitt's lymphoma lines involves the induction of an apoptotic program via transcriptional upregulation of the proapoptotic BH3-only proteins PUMA (our unpublished observations) and BIK, while also downregulating the prosurvival factor BCL-XL. Here, TGFB1 is linked to Burkitt lymphoma.