Mutations in Smads, intermediates of transforming growth factor-β signaling, are known to contribute to the loss of sensitivity to transforming growth factor-β, 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 31bp 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.
Bibliographical noteFunding Information:
We thank Dr PK Shyamala Devi for providing fresh cervical tissues, and Dr Balaraman Nair, Ms Indu Ramachandran and Ms Sheela for technical advice and help. A research grant from the Department of Science and Technology (to DK), program support to the Rajiv Gandhi Center by the Department of Biotechnology, a Research Associate Fellowship (to AN) and a Senior Research Fellowship (to TTM) by the Council of Scientific and Industrial Research, Government of India are gratefully acknowledged.
Copyright 2008 Elsevier B.V., All rights reserved.
- Cervical cancer