title: Resistance to TGF-beta 1 correlates with aberrant expression of TGF-beta receptor II in human B-cell lymphoma cell lines.
abstract: 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 (T beta RII) in contrast to the TGF-beta-responsive cell line RL, whereas both cell lines had comparable levels of receptor I (T beta RI). Lack of functional T beta RII 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 T beta RII rendered the DB cell line responsive to TGF-beta1-mediated growth suppression. Analysis of the T beta RII gene in DB cells revealed the absence of T beta RII 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 T beta RII gene silencing and subsequent development of a TGF-beta1-resistant phenotype by some B-cell lymphoma cells.
authors.affiliation: Lymphocyte Cell Biology Unit, Laboratory of Immunology, Gerontology Research Center, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA.
authors.forename: Gang
authors.initials: G
authors.lastname: Chen
authors.forename: Paritosh
authors.initials: P
authors.lastname: Ghosh
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Osawa
authors.forename: Carl Y
authors.initials: CY
authors.lastname: Sasaki
authors.forename: Louis
authors.initials: L
authors.lastname: Rezanka
authors.forename: Jiandong
authors.initials: J
authors.lastname: Yang
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: O'Farrell
authors.forename: Dan L
authors.initials: DL
authors.lastname: Longo
mesh_terms: D045744:Cell Line, Tumor; D019175:DNA Methylation; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D006801:Humans; D016393:Lymphoma, B-Cell / Q000235:genetics* / Q000473:pathology; D011401:Promoter Regions, Genetic / Q000235:genetics; D017346:Protein Serine-Threonine Kinases; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000172:deficiency / Q000235:genetics*; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology*
chemical_list: D018125:Receptors, Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D017346:Protein Serine-Threonine Kinases; D000077294:Receptor, Transforming Growth Factor-beta Type II