Predictive utility of circulating methylated DNA in serum of melanoma patients receiving biochemotherapy

Abstract

Purpose: Currently, no validated blood-based assays accurately predict treatment response or outcome in melanoma patients. We hypothesized that methylation of tumor-related genes detected in serum DNA could predict disease outcome and therapeutic response in patients receiving concurrent biochemotherapy (BC) for metastatic melanoma.

Patients and methods: American Joint Committee on Cancer stage IV melanoma patients (N = 50) had blood drawn before administration of BC. Patients (n = 47) were classified as BC responders or nonresponders. Responders (n = 23) demonstrated a complete or partial response following BC; nonresponders (n = 24) demonstrated progressive disease. Hypermethylation of Ras association domain family 1 (RASSF1A), retinoic acid receptor-beta2 (RAR-beta2), and O6-methylguanine DNA methyltransferase (MGMT) genes were assessed by methylation-specific polymerase chain reaction.

Results: Circulating methylated RASSF1A was significantly less frequent for responders (three of 23 patients; 13%) than nonresponders (10 of 24 patients; 42%; P = .028). Patients with RASSF1A, RAR-beta2, or at least one serum methylated gene had significantly worse overall survival than patients with no methylated genes (log-rank, P = .013, .021, and .01, respectively). Methylated RASSF1A was the only factor that significantly correlated with overall survival and BC response (risk ratio, 2.38; 95% CI, 1.16 to 4.86; P = .018; odds ratio = 0.21; 95% CI, 0.05 to 0.90; P = .036).

Conclusion: Detection of circulating methylated DNA in serum can predict response to BC and disease outcome.

Fig 1

DNA concentration in serum of responders and nonresponders to biochemotherapy (BC). Horizontal bar shows the mean DNA concentration (P = .03).

Fig 2

(A) Kaplan-Meier survival curves of biochemotherapy (BC) patients: Correlation of pre-BC serum RASSF1A methylation status with overall survival (log-rank test, P = .013). Methylated: Patients with serum methylation of RASSF1A. Nonmethylated: Patients with no serum methylation of RASSF1A. (B) Correlation of pre-BC serum RAR-β2 methylation status with overall survival (log-rank test, P = .02). Methylated: Patients with serum methylation of RAR-β2. Nonmethylated: Patients with no serum methylation of RAR-β2. (C) Correlation of pre-BC serum methylation of at least one marker with overall survival (log-rank test, P = .01). ≥ 1 methylated: Patients with serum methylation of at least one marker. Nonmethylated: Patients with no serum methylation of genes.