Targeted DNA methylation from cell-free DNA using hybridization probe capture.

Cell-free (cf)DNA signatures are quickly becoming the target of choice for non-invasive screening, diagnosis, treatment and monitoring of human tumors. DNA methylation changes occur early in tumorigenesis and are widespread, making cfDNA methylation an attractive cancer biomarker. Already a proven technology for targeted genome sequencing, hybridization probe capture is emerging as a method for high-throughput targeted methylation profiling suitable to liquid biopsy samples. However, to date there are no reports describing the performance of this approach in terms of reproducibility, scalability, and accuracy. In the current study we performed hybridization probe capture using the myBaits ® Custom Methyl-seq kit on 172 plasma samples and standards to evaluate its performance on cfDNA methylation analysis. The myBaits ® assay showed high target recovery (>90%), demonstrated excellent reproducibility between captures ( R 2  = 0.92 on average), and was unaffected by increasing the number of targets in a capture. Finally, myBaits ® accurately replicated 'gold standard' beta values from WGBS (average R 2  = 0.79). The results of this study show that custom targeted methylation sequencing with myBaits ® offers a cost-effective, reliable platform to profile DNA methylation at a set of discrete custom regions, with potential applicability to liquid biopsies for cancer monitoring.