Prediction of therapy failure after VEGF-based first-line treatment of kidney cancer patients by DNA hypermethylation biomarkers.

Abstract

e22076 Background: Kidney Cancer (RCC) is one of the top ten causes of cancer dependent death. Anti-VEGF targeted therapy has demonstrated increased progression-free (PFS) and overall survival in RCC patients, though the clinical outcome is still poor overall. Stratification of patient treatment currently depends on different clinical scoring systems such as the Memorial Sloan Kettering Cancer Center score. However, identification of molecular phenotypes of RCC patients could improve stratification of targeted therapies and prediction of clinical course. We investigated whether DNA hypermethylation-based markers can predict the PFS following first-line therapy. Methods: We examined primary tumor tissues obtained from 18 patients receiving anti-VEGF targeted therapy. Quantitative methylation-specific PCRs were carried out for CpG island (CGI) methylation analysis of 5 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. 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 CST6a 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.