DNA was extracted from the frozen tissue and urine samples using the AllPrep DNA Mini kit (Qiagen, Inc., Valencia, CA, USA) according to the manufacturer's protocol. The concentration and purity of DNA were assessed by determining the OD260/OD280 ratio using a Nanodrop 1000 spectrophotometer (Thermo Fisher Scientific, Inc., Waltham, MA, USA). DNA was treated by bisulfite using an EZ-96 DNA Methylation-Gold™ kit (Zymo Research, Irvine, CA, USA) according to the manufacturer's protocol, as well as the previously described protocol (20 (link)), and stored at −80°C until use.