Transforming growth factor (
TGF)-beta strongly inhibits epithelial cell proliferation. Alterations of
TGF-beta signaling are thought to play a role in
tumorigenesis. We show in the present study that most
lung cancer cell lines have lost the growth-inhibitory response to
TGF-beta signal, and that those with
TGF-beta unresponsiveness can be divided into two major groups,
TGF-beta type II receptor (TGFbetaRII)(+)/Smad7(+) and TGFbetaRII(-)/Smad7(-), suggesting the heterogeneous mechanisms underlying the
TGF-beta responsiveness. The mechanism of the loss of TGFbetaRII expression of the latter group was further studied, identifying aberrant DNA methylation of the promoter region in a limited fraction of cell lines. Interestingly, we found that the alteration of
chromatin structure because of
histone deacetylation may also be involved, showing a good correlation with loss of TGFbetaRII expression. This notion was supported by the findings of a restriction
enzyme accessibility assay, of a
chromatin immunoprecipitation assay with anti-acetyl
histone antibodies, and of an in vivo induction of TGFbetaRII expression by
histone deacetylase inhibitors including
trichostatin A (
TSA) and
sodium butyrate. In vitro induction of TGFbetaRII promoter reporter activity by
TSA was also detected and found to require the CCAAT box within the -127/-75 region. A positive regulatory mechanism for TGFbetaRII expression in a
TGF-beta-expressing cell line was also investigated, and a TPA-responsive
element (TRE)-like motif, TRE2, was detected in addition to the previously reported TRE-like motif Y
element in the positive regulatory region. Alterations in two discrete
proteins interacting with these two TRE-like motifs were also suspected of being involved in the loss of TGFbetaRII expression. This is the first study to demonstrate that, in addition to the
TSA-responsive region and TRE2 motif in the TGFbetaRII promoter, the alteration of
histone deacetylation may be involved in the loss of TGFbetaRII expression in
lung cancer cell lines.