A sample consisted of a 200 mg biopsy. Specimens were ground separately with mortar and pestle in liquid nitrogen. The frozen powder was transferred to a 2 mL eppendorf tube and 800 mL of extraction solution (50 mM Tris-HCL, pH8.0; 25 mM EDTA and 400 mM NaCl), 100 mL 10% SDS, and 20 mL Proteinase K (10 mg/mL) were added. The extract was homogenized and incubated at 65 °C for 3 h. After incubation, proteins and cellular debris were precipitated by adding a 300 mL 6 M NaCl, kept at 4 °C for 15 min. Centrifugation was done at 25,000 g for 20 min. 500 mL of the supernatant were transferred to a new eppendorf, with 500 mL 8 M guanidine hydrochloride (pH 8.0), and 0.49 M ammonium acetate solution, and kept in mild agitation for 90 min. Nucleic acids were precipitated by adding 800 mL of cold 100% isopropyl alcohol, followed by centrifugation at 8,000 g for 5 min. Pellets were washed with 400 mL of 70% isopropyl alcohol. After drying, pellets were resuspended in 150 mL TE buffer (10 mM Tris-HCl, pH 8.0; 1 mM EDTA and 50 mg/mL RNAse). DNA samples were stored at 4 °C.