Resistance to transforming growth factor (TGF)-beta1-mediated growth suppression in tumor cells is often associated with the functional loss of TGF-beta receptors. Here we describe two B-cell lymphoma cell lines (DB and RL) that differ in their sensitivity to TGF-beta1-mediated growth suppression. The TGF-beta1-resistant cell line DB lacked functional TGF-beta receptor II (TbetaRII) in contrast to the TGF-beta-responsive cell line RL, whereas both cell lines had comparable levels of receptor I (TbetaRI). Lack of functional TbetaRII was correlated with the lack of TGF-beta1-induced nuclear translocation of phospho-Smad3 and phospho-Smad2, the lack of nuclear expression of p21(Cip1/WAF1), and the down-regulation of c-Myc in DB cells. Transfection of wild-type, but not a C-terminal-truncated, form of TbetaRII rendered the DB cell line responsive to TGF-beta1-mediated growth suppression. Analysis of the TbetaRII gene in DB cells revealed the absence of TbetaRII message, which was reversed upon 5'-azacytidine treatment, indicating that the promoter methylation might be the cause of gene silencing. Promoter analysis revealed CpG methylations at -25 and -140 that correlated with the gene silencing. These data suggest that promoter methylation plays an important role in TbetaRII gene silencing and subsequent development of a TGF-beta1-resistant phenotype by some B-cell lymphoma cells.