Inactivation of the cystatin E/M tumor suppressor gene in cervical cancer

Mysore S. Veena, Grant Lee, Daniel Keppler, Marc S. Mendonca, J. Leslie Redpath, Eric J. Stanbridge, Sharon P. Wilczynski, Eri S. Srivatsan

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23 Scopus citations

Abstract

We have previously localized a cervical cancer tumor suppressor gene to a 300 kb interval of 11q13. Analysis of candidate genes revealed loss of expression of cystatin E/M, a lysosomal cysteine protease inhibitor, in 6 cervical cancer cell lines and 9 of 11 primary cervical tumors. Examination of the three exons in four cervical cancer cell lines, 19 primary tumors, and 21 normal controls revealed homozygous deletion of exon 1 sequences in one tumor. Point mutations were observed in six other tumors. Two tumors contained mutations at the consensus binding sites for cathepsin L, a lysosomal protease overexpressed in cervical cancer. Introduction of these two point mutations using site directed mutagenesis resulted in reduced binding of mutated cystatin E/M to cathepsin L. Although mutations were not observed in any cell lines, four cell lines and 12 of 18 tumors contained promoter hypermethylation. Reexpression of cystatin E/M was observed after 5′aza 2-deoxycytidiene and/or Trichostatin A treatment of cervical cancer cell lines, HeLa and SiHa, confirming promoter hypermethylation. Ectopic expression of cystatin E/M in these two cell lines resulted in growth suppression. There was also suppression of soft agar colony formation by HeLa cells expressing the cystatin E/M gene. Reexpression of cystatin E/M resulted in decreased intracellular and extracellular expression of cathepsin L. Overexpression of cathepsin L resulted in increased cell growth which was inhibited by the reintroduction of cystatin E/M. We conclude, therefore, that cystatin E/M is a cervical cancer suppressor gene and that the gene is inactivated by somatic mutations and promoter hypermethylation.

Original languageEnglish (US)
Pages (from-to)740-754
Number of pages15
JournalGenes Chromosomes and Cancer
Volume47
Issue number9
DOIs
StatePublished - Sep 1 2008

ASJC Scopus subject areas

  • Genetics
  • Cancer Research

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    Veena, M. S., Lee, G., Keppler, D., Mendonca, M. S., Redpath, J. L., Stanbridge, E. J., Wilczynski, S. P., & Srivatsan, E. S. (2008). Inactivation of the cystatin E/M tumor suppressor gene in cervical cancer. Genes Chromosomes and Cancer, 47(9), 740-754. https://doi.org/10.1002/gcc.20576