TGF- β1–mediated Apoptosis Associated With SMAD-dependent MitochondrialBcl-2 Expression

BackgroundTransforming growth factor (TGF) β1 can elicit various cellular responses, including inhibition of cell growth, migration, differentiation, and apoptosis. In addition, TGF-β1 is able to induce apoptosis in certain lymphomas.MethodsIn the present study, the role of SMADs, Bax, Bcl-xl, and Bcl2 was characterized in 2 B-lymphoma cell lines, Burkitt and pre–B cell.ResultsApoptosis was detected after exposure of TGF-β on Raji and Nalm 6 cell lines and was evaluated by flow cytometry by using annexin V, reverse transcriptase–polymerase chain reaction, and Western blot analysis. Flow Cytometry With Cell Sorting analysis showed that apoptosis could be observed after 24 hours of TGF-β treatment and was continued after 48 hours. TGF-β downregulated the Bcl-xl and Bcl-2, whereas the Bax was upregulated. Furthermore, messenger RNA of SMAD6 and SMAD7 showed the significant upregulation.ConclusionThe results indicated that alteration in gene expression and protein level may determine the induction of apoptosis pathway in these lymphoma cell lines exposed to TGF-β.