Mutational analysis of Smad7 in human cervical cancer.

Our aim was to carry out mutational analysis of Smad7 exon 4 that codes for the Smad7 MH2 domain in human cervical cancer tissues. This study is warranted since genetic abnormalities of components of the transforming growth factor-beta (TGF-beta)/Smad signaling system have been implicated in a variety of human cancers. Further, Smad7 is an important member of the Smad family that functions as a negative feedback regulator of TGF-beta responses. By direct sequencing, we screened 60 histopathologically confirmed human cervical carcinomas for mutations in exon 4 of Smad7 that encodes the MH2 domain of the protein, a region of the protein believed to be critical for receptor interaction. No mutations or aberrations could be identified in any of the 60 analyzed tumor samples. However, we identified a previously reported, heterozygous, silent G to C variant in codon 391 of Smad7 that was found twice in the set of 60 clinical samples. Thirty of the clinical samples analyzed in the study were positive for the presence of high-risk human papillomavirus (HPV) subtypes, while the rest were oncogenic HPV-negative. The two instances of the silent variant was found in oncogenic HPV-negative samples. We report mutational analysis of Smad7 in cervical cancer for the first time. Mutations and variants of Smad7 are unlikely to be of major significance to the pathogenesis of HPV-induced cervical cancer.