2.3 DNA extraction
The tissue samples were ground to powder with liquid nitrogen and
diluted with three volumes of phosphate‐buffered saline. The samples (1
ml) were centrifuged at 12,000×g for 10 min at 4°C and the supernatants
were transferred into a 1.5 ml tube. Nucleic acids from tissues and
serum samples were extracted by using an EasyPure®Viral DNA/RNA Kit (TransGen Biotech, Beijing, China) according to the
manufacturer’s instructions. The extracted genomic DNA was stored at
-20°C before use.