Methylation status: Methylation status in the selected genes will be evaluated on the bisulfite modified DNA. The assays will be performed employing primers selected according to published sequences (Hesselink AT et al. Mirabello L et al, Wentzensen N et al). When not available, primers will be designed using a specific software . Links with available Gene-banks will be set up for gene sequence references. A preliminary PCR reaction will be performed in a total volume of 35 microL containing 1X KCl, 2mM MgCl2 , 200 microM dNTPs, 0.5 microM of each primer (antisense biotinylated), 1.75U Taq polymerase and 6 microL modified DNA with the proper thermocycling profile. Amplification and real-time measurement was performed in the 7500 ABI system (Applied Biosystems, Foster City, CA, USA). Bisulfite modified controls for methylated and unmethylated status of cell and viral gene respectively will be included in each run.