Cystatins are protease inhibitors active against lysosomal cysteine proteases. Cystatin M/E mapped to chromosome 11q13 is an important member of this family having significant role in the suppression of metastasis in breast cancer. Null mutation of the gene results in neonatal lethality, abnormal cornification and desquamation in mice. Previously we have shown that cervical cancers carry a chromosome 11q13 deletion indicating the localization of a tumor suppressor gene at this locus. Analysis of cervical cancer cell lines and primary tumors has shown loss of expression for the cystatin E/M in all the cell lines and in majority of tumors. Sequencing of the three exons coding for cystatin M/E did not show any mutations. Therefore, we analysed cystatin M/E promoter for hypermethylation. Methylation of the CpG sequences spanning the +2 to -148 region was observed in four of six cell lines and in one of four primary tumors confirming promoter hypermethylation. Treatment of two different cell lines cell lines, HeLa and SiHa, with the demethylating agent, 5’-aza 2’deoxycytidene resulted in reexpression of the gene in the HeLa cells. The gene was not reactivated in the SiHa cells that did not contain promoter hypermethylation. However, the gene was reactivated in this cell line with TSA, an inhibitor of histone deacetylase. Thus, the results suggest that cystatin M/E gene was inactivated in cervical cancer samples by promoter hypermethylation and/or by histone deacetylation.
98th AACR Annual Meeting-- Apr 14-18, 2007; Los Angeles, CA