Identification of genetic alterations in the TGFbeta type II receptor gene promoter.

Modifications in the control sequences of tumor suppressor genes have been found to play a role in the activation or inactivation of these genes and may play an important role in tumorigenesis. For example, hypermethylation of CpG islands and promoter polymorphisms have been found to be involved in transcriptional repression. A decrease in the levels of expression of one such tumor suppressor gene, the TGFbeta type II receptor (TbetaR-II), has been associated with increased tumorigenicity in a number of human tumors. Genetic alterations have been described in several tumor types in the coding region of this gene. However, no comprehensive search for genetic alterations in the TbetaR-II promoter has been reported. Genetic alterations in the promoter of the TbetaR-II gene could inhibit binding of putative regulatory factors. For example, we have reported a A-364-G alteration in the TbetaR-II promoter, which results in decreased transcriptional activity. In this study, we analyzed the 1.0kb region upstream of the TbetaR-II transcriptional start site and found genetic alterations in 46% of the head and neck squamous cell carcinoma (SqCC) samples examined. The most frequent alteration was a G-875-A alteration, present in 41.6% of the samples. Analysis of normal healthy individuals showed a similar frequency of this alteration, suggesting that alterations within the TbetaR-II promoter are unlikely to account for the decreased expression of TbetaR-II in head and neck SqCC.