TGF-β signaling is defective in PEL. (A) Cell growth of PEL cell lines, BC1, BC3, and BCBL1, and TGF-β-sensitive, Burkitt lymphoma cell line, Ramos, over 4 days of treatment with TGF-β1. (B) Flow cytometric analysis of apoptosis 48 hours after TGF-β1 treatment. (C) TGF-β reporter, p3TP-Lux, activity in response to treatment with TGF-β1. Error bars represent SD. (D) Western blot detection of Smad2/3 phosphorylation (p-Smad2/3), Smad2/3 nuclear accumulation (n-Smad2/3), total Smad 2/3 (t-Smad2/3), and p21 expression on TGF-β1 treatment.