Analysis of specific gene mutations in the transforming growth factor-betasignal transduction pathway in human ovarian cancer

Several proteins, including transforming growth factor beta (TGF-P) recepto r type I(RI), TGF-beta receptor type II (RII), Smad2, Smad3, and Smad4/DPC4 , have been identified in the transduction pathway of the tumor suppressor TGF-P. Mutations in TGF-beta RI, TGF-beta RII, Smad2, and Smad(4)/DPC4 gene s are associated with several human cancers. The present study examines the se gene mutations in 32 human ovarian cancers and 14 patient-matched normal tissues. For the first time, mutations in the Smad2 and Smad4 genes were a nalyzed in relation to human ovarian cancer. Gene mutations of TGF-beta RI, TGF-beta RII, Smad2, and Smad4 were analyzed using specific primers by PCR -single-strand conformational polymorphism (SSCP), and the results revealed a frameshift mutation at codons 276-277 (CTCTGG-->CTGCGTGG) in exon 5 of T GF-beta RI in 10 of 32 tumor samples (31.3%). This mutation was associated with reduced or absent expression of TGF-beta RI protein and p53 protein in tumor tissues. We detected SSCP variants of TGF-beta RII in exon 2 in 20 o f 32 tumors. Sequence analysis of these variants revealed an A to G transit ion at the seventh band of intron 2, In this A to G polymorphism in intron 2, 12 samples (37.5%) had A/A alleles, 12 (37.5%) had A/G alleles, and 8 (2 5%) had G/G alleles, We detected Smad2 SSCP variants in exon 4 in 12 of 32 tumors (37.5%). Sequence analysis revealed a 2-bp deletion in the polypyrim idine tract of intron 3, which is located at position -39 to -56 in the spl ice acceptor site of the intron 3-exon 4 junction, No SSCP variants were de tected in the Smad4 gene. These findings suggest that mutations in the TGF- beta RI and in its signal transduction pathway are likely responsible for h uman ovarian carcinogenesis.