We considered the promoters showing a ratio 0. 20 as methylated, while those with a ratio 0. 20 were regarded as unmethylated. The cut off was chosen on the basis of experiments performed on the bladder cancer cell line and on data from the literature. We have also performed the analysis on some samples from healthy tissues, to confirm that the background noise was inferior to 0. 20 cut off, such excluding false positive results due to experimental procedure. and water to the second. The samples were then incu bated at 49 C for 30 min. At the end of the ligation and ligation digestion reactions, samples were amplified by adding a mix of PCR buffer, dNTPs and Taq polymerase. The PCR reaction was performed under the following conditions, 37 cycles at 95 C for 30 sec, 60 C for 30 sec and 72 C for 60 sec.

The final incubation was performed at 73 C for 20 min. Amplification products were analyzed by ABI 3130 genetic Analyzer. Universally methylated and unmethylated genomic DNA was used as positive or negative control, respectively. selleck Electropherograms obtained were analyzed using Gene Mapper software and the peak areas of each probe were exported to a home made excel spreadsheet. In accordance with the manufacturers instructions, we carried out intrasample data normaliza tion by dividing the signal of each probe by the signal of every reference probe in the sample, thus creating as many ratios per probe as there were reference probes. We then calculated the median value of all probe ratios per probe, obtaining the normalization constant.

Finally, the methylation purchase (-)-p-Bromotetramisole Oxalate status of each probe was calculated by dividing the NC of a probe in the digested sample by the NC of the same probe in the undigested Statistical analysis Fishers exact test was used to compare the frequency of promoter methylation in the two subgroups, recurrent tumors versus non recurrent tumors. Methylation status was considered as a dichotomic variable and genes showing methylation 20% were classified as positive. A difference was considered significant if it showed a two tailed P value 0. 05. The genes showing a significant p value in Fishers exact test were used to analyze the methylator phenotype. Study endpoints were sensitivity and speci ficity, with their 95% confi dence intervals. We also evaluated overall accu racy, defined as the proportion of the total number of patients correctly identified by the test.

The students T test was used to assess the methylation index, which was considered as a continuous variable. Logistic regression analysis was performed using the Epicalc of R to evaluate the performance of a panel of gene promoters in discriminating between recurrent and non recurrent pa tients. We created logistic regression models with methylation levels of the three gene promoters.