As previously described by Voorham et al[12 (link)], the paraffin-embedded sections were incubated for five days in ATL lysis buffer (QIAmp DNA Micro Kit, Qiagen, Beijing, China). Proteinase K (10 μL from a 20 ng/μL solution) was added daily. DNA isolation was performed using a column-based technique (QIAmp DNA Micro Kit, Qiagen). A Beckman UV-vis spectrophotometer (Beckman, CA, United States) was used to measure DNA concentrations and purities.