Re-expression of PTPRO following treatment with 5-AzaC. (a) Breast cancer cell lines MCF-7 and MDA-MB-231 were treated with 1 μM 5-AzaC for 72 h and 2.5 μM 5-AzaC for 96 h, respectively. Total RNA from cells was subjected to RT-PCR to amplify PTPRO mRNA. 18S rRNA was used for normalization; (b) MSP analysis of PTPRO methylation status in breast cancer cell lines with or without 5-AzaC treatment. M, methylated; U, unmethylated.