Loss of expression, and mutations of Smad 2 and Smad 4 in human cervical cancer.
Mutations in Smads, intermediates of transforming growth factor-beta signaling, are known to contribute to the loss of sensitivity to transforming growth factor-beta, a common feature of many neoplastic cells. However, not much information is available on Smad alterations in cervical cancer and so we probed, for the first time, for alterations in Smad 2 and Smad 4 genes using human cervical cancer cell lines and human cervical tissue samples. Using PCR/reverse transcription-PCR, single-stranded conformation polymorphism analysis and DNA sequencing, we observed a deletion of 'G' in the L3 loop (crucial in Smad-receptor interaction) in C-33A cells, and an insertion of 'A' in codon 122 (loss of MH2 domain) from a cervical tumor sample, both of which caused frame shift and pretermination in Smad 2. In addition, a G/A transition at 31 bp upstream-nontranslated regions of exon 8 of Smad 4 was found in Bu 25TK cells. Smad 2 expression was less in some of the cervical tumor samples than that of nonmalignant samples and six cancer samples showed C-terminal deletions that abolish Smad 2 phosphorylation sites. The loss of expression of Smad 4 found in some cervical tumor samples was due to transcription loss rather than deletion of the gene. Our results highlight an important role for Smad 2 and Smad 4 in human cervical tumors.
Maliekal
Tessy T
TT
Division of Cancer Biology, Rajiv Gandhi Center for Biotechnology, Thiruvananthapuram, Kerala 695 014, India.
Antony
Marie-Lue
ML
Nair
Asha
A
Paulmurugan
Ramasamy
R
Karunagaran
Devarajan
D
D000595:Amino Acid Sequence; D004252:DNA Mutational Analysis; D004273:DNA, Neoplasm / Q000235:genetics; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000172:deficiency / Q000235:genetics* / Q000502:physiology; D005260:Female; D016368:Frameshift Mutation; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000737:chemistry / Q000172:deficiency / Q000235:genetics* / Q000502:physiology; D010766:Phosphorylation; D018807:Polymorphism, Single-Stranded Conformational; D011499:Protein Processing, Post-Translational / Q000235:genetics; D017434:Protein Structure, Tertiary; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017384:Sequence Deletion; D051899:Smad2 Protein; D051901:Smad4 Protein; D015534:Trans-Activators / Q000737:chemistry / Q000172:deficiency / Q000235:genetics* / Q000502:physiology; D014158:Transcription, Genetic; D016212:Transforming Growth Factor beta / Q000502:physiology; D014407:Tumor Cells, Cultured / Q000378:metabolism; D002583:Uterine Cervical Neoplasms / Q000235:genetics* / Q000473:pathology
D004273:DNA, Neoplasm; D004268:DNA-Binding Proteins; D009363:Neoplasm Proteins; C497782:SMAD2 protein, human; C497796:SMAD4 protein, human; D051899:Smad2 Protein; D051901:Smad4 Protein; D015534:Trans-Activators; D016212:Transforming Growth Factor beta