DNA hypermethylation biomarkers to predict therapy response of antiangiogenic therapy in metastatic renal cell carcinoma patients

459 Background: Antiangiogenic therapy has demonstrated to increase progression-free (PFS) as well as overall survival (OS) in RCC patients. Clinical scoring systems like the Memorial Sloan Kettering Cancer Center (MSKCC) help to stratify patients for treatment options. However, identification of molecular phenotypes of RCC patients would improve stratification of specific targeted therapies. We investigated whether DNA hypermethylation based markers can predict the PFS following first-line therapy. Methods: We examined primary tumors from formalin-fixed paraffin embedded tissue specimens obtained from 18 patients receiving anti-VEGF based targeted therapy. Quantitative methylation-specific PCRs were carried out following bisulphite conversion of DNA for CpG island methylation analysis of the five candidate genes, CST6, GATA5, LAD1, hsa-miR124-3 and hsa-miR9.1 identified in advance as potential prognosticators for RCC. For Kaplan Meier survival analysis relative methylation values were uniformly dichotomized and logrank statistics calculated. The analyses of sensitivity and specificity were carried out using a cutoff of 6 months for PFS to categorize for therapy failure and response, as described in the literature. Results: Hypermethylation of CST6 and LAD1 shows a highly significant association with a shortened PFS following first-line therapy (p=0.009, p=0.004, logrank test). The median survival observed for the high and low methylation group was 2.0 and 11.4 months for CST6 and LAD1. Moreover, LAD1 methylation showed a specificity of 1.0 (0.65-1.0, 95%CI) and a sensitivity of 0.73 (0.43-0.90, 95%CI) for detection of therapy failure. For CST6 methylation analysis a specificity of 0.86 (0.49-0.97, 95%CI) and a sensitivity of 0.82 (0.52-0.95, 95%CI) was detected. Conclusions: The analysis of our discovery cohort revealed that CGI methylation of CST6 and LAD1 predicts a shortened PFS of patients after anti-VEGF therapy. Provided, these results can be confirmed in an independent larger evaluation cohort, detection of hypermethylated loci in primary RCC would allow, to our knowledge for the first time, a molecular-based clinical management of patients.