2.4. Cell culture and DNA Isolation
SK-N-BE2, SK-N-AS, SH-SY5Y and HUVEC cell lines were culture in DMEM supplemented with 10% FBS, penicillin (100 μg/mL) and streptomycin (100 μg/mL) in 5% CO2 at 37 °C. Total extraction kit DP304 purchased from Tiangen Biotech (Beijing China) was used to extract the total DNA in cell lines NB tissue samples and plasma specimens.