Association of epigenetic inactivation of the WRN gene with anticancer drug sensitivity in cervical cancer cells

The Werner (WRN) gene codes for a DNA helicase that contributes to genomicstability and has been identified as the gene responsible for progeria. Recentstudies have shown reduced WRN expression due to aberrant DNA hypermethylationin cancer cells. Furthermore, WRN expression is thought to affect sensitivityto DNA topoisomerase I inhibitors in cancer therapy. In this study, we examinedthe relationship between aberrant DNA hypermethylation of WRN and the sensitivityof cervical cancer cells to anticancer drugs. DNA was extracted from samples from22 patients with primary cervical cancer and 6 human cervical cancer-derived celllines. Aberrant DNA hypermethylation was analyzed by methylation-specific PCR.WRN expression in cultured cells before and after addition of 5-aza-2-deoxycytidine,a demethylating agent, was examined using RT-PCR. The sensitivity of cells toanticancer drugs was determined using a collagen gel droplet embedded culturedrug sensitivity test (CD-DST). siRNA against WRN was transfected into a cervicalcancer-derived cell line with high WRN expression. Changes in drug sensitivityafter silencing WRN were determined by CD-DST. Aberrant DNA hypermethylation anddecreased expression of WRN were detected in 7/21 cases of primary cervical cancerand in two cervical cancer-derived cell lines. These two cell lines showed highsensitivity to CPT-11, a topoisomerase I inhibitor, but became resistant to CPT-11after treatment with 5-aza-2-deoxycytidine. Transfection of siRNA against WRNincreased the sensitivity of the cells to CPT-11. Aberrant DNA hypermethylationof WRN also increased the sensitivity of cervical cancer cells to CPT-11. Therefore,epigenetic inactivation of this gene may be a biomarker for selection of drugsfor the treatment of cervical cancer. This is the first report to show a relationshipbetween the methylation of the WRN gene and sensitivity to CPT-11 in gynecologicalcancers.