Whole blood was obtained from corresponding HCC patients and controls except in one case without an available blood sample in the alcohol-HCC group. Mitochondria isolation and mtDNA extraction were carried out using the Blood Mitochondrial DNA Extraction Kit (Genmed Scientific Inc.). All mtDNA was stored at -20°C. Table 1 Clinical data in HBV-HCC, alcohol-HCC patients and controls HBV-HCC (n = 49) Alcohol-HCC (n = 11) Control (n = 38) Age (years) 52.20 ± 9.86 58.36 ± 8.11 53.08 ± 10.98 Sex (M/F) 43/6 10/1 18/20 selleck Child-Pugh Grade SIS3 mw (B/A) 2/47 0/11 – Alcohol abuse 1 11 0 Positive HBV surface antigen 49 0 0 Positive HBV anti-surface
antibody 0 0 0 Tumor stage (I/II/III) 13/36/0 2/5/3a – aOne alcohol-HCC patient did not have sufficient tissues for
stage classification. PCR amplification and sequence analysis The forward primer 5′-CCCCATGCTTACAAGCAAGT-3′ (nucleotide 16190-16209) and reverse primer 5′-GCTTTGAGGAGGTAAGCTAC-3′ (nucleotide 602-583) were used for amplification of a 982 bp product from mtDNA D-Loop region as described previously [27]. PCR was performed according to the protocol of PCR Master Mix Kit (Promega, Madison, WI) and purified prior to sequencing. Cycle sequencing was carried out with the Dye Terminator Cycle Sequencing Ready Reaction Kit (Applied Biosystem, Navitoclax Foster City, CA) and the products were then separated on the ABIPRISM Genetic Analyzer 3100 (Applied Biosystem). Mutations and polymorphisms were confirmed by repeated analyses from both strands. SNPs were identified directly from blood mitochondria. Statistical analysis Paired and unpaired Student’s t-test were used as appropriate to determine the differences SNP distribution within the D-Loop region and the number of SNPs per patient among groups. Fisher’s exact test and chi-square were used accordingly
to analyze dichotomous values, such as presence or absence of an individual SNP in each patient group. A p value of less than 0.05 was considered statistically significant. The Wilcoxon rank sum test was used to determine statistical differences among age, sex and Child-Pugh grade. Pairwise linkage disequilibrium AMP deaminase between SNPs was done using GENEPOP http://wbiomed.curtin.edu.au/genepop Results SNPs in reference to GenBank accession AC_000021 were detected in 92 sites of the 982-bp mitochondria D-Loop region from blood samples. The minor allele frequency ranged from 1.0% (1/98) to 46.90 (46/98). Of these, 13 SNPs (16A/T, 44C/CC, 56A/G, 245T/C, 275G/A, 310T/G, 368A/G, 449T/C, 454T/C, 570C/G, 16259C/G, 16267C/G, and 16445T/C) were new, as they were not reported in a mitochondria database http://www.mitomap.org. SNP numbers ranged from 3 to 13 for individuals, no statistical difference for SNP numbers in each individual referring to sex was observed.