Ined sections were reviewed by a senior pathologist to mark out representative areas. Using a tissue arraying instrument (Beecher Instruments, Sliver Spring, MD), each tissue core with a diameter of 0.6 mm was punched from the marked areas and re-embedded.Immunohistochemistry (IHC)Formalin-fixed and paraffin-embedded HCC sections with a Fexinidazole thickness of 4 mm were dewaxed in xylene and graded alcohols, hydrated, and washed in phosphatebuffered saline (PBS). After pretreatment in a microwave oven, endogenous peroxidase was inhibited by 3 hydrogen peroxide in methanol for 20 min, followed by avidin-biotin blocking using a biotin-blocking kit (DAKO, Germany). Slides were then incubated with SIRT3 antibody, overnight in a moist chamber at 4uC, washed in PBS, and incubated with biotinylated goat anti-rabbit/mouse antibodies. Slides were developed with the Dako Liquid 3, ‘3diaminobenzidine tetrahydrochloride (DAB)+Substrate Chromogen System and counterstained with 22948146 hematoxylin.Western BlotCell or tissue lysates were boiled with 6X sodium dodecyl sulfate (SDS) loading buffer and then fractionated by SDS-PAGE. The proteins were transferred to PVDF membrane which was then incubated with a primary specific antibody for SIRT3 in 5 of non-fat milk, followed by a horse radish peroxidase (HRP)conjugated anti-rabbit second antibody. ECL detection reagent (Amersham Life Science, Piscataway, NJ, USA) was used to demonstrate the results.SIRT3 as a Prognostic Biomarker in HCCTable 1. Correlation between the clinicopathologic variables and SIRT3 expression in HCC.VariableSIRT3 protein All cases 
Low expression High expression x2 0.021 130 118 87 (66.9 ) 80 (67.8 ) 43 (33.1 ) 38 (32.8 ) 0.842 28 220 21 (75.0 ) 146 (66.4 ) 7 (25.0 ) 74 (33.6 ) 0.096 215 33 144 (67.0 ) 23 (69.7 ) 71 (33.0 ) 10 (30.3 ) 16.521 102 146 54 (52.9 ) 113 (77.4 ) 48 (47.1 ) 33 (22.6 ) 0.004 180 68 121 (67.2 ) 46 (67.6 ) 59 (32.8 ) 22 (32.4 ) 0.889 121 127 78 (64.5 ) 88 (69.3 ) 43 (35.5 ) 39 (30.7 ) 4.936 131 117 80 (61.1 ) 87 (74.4 ) 51 (38.9 ) 30 (25.6 ) 6.224 150 98 92 (61.3 ) 75 (76.5 ) 58 (38.7 ) 23 (23.5 ) 8.048 109 139 63 (57.8 ) 104 (74.8 ) 46 (42.2 ) 35 (25.2 ) 0.300 73 175 51 (69.9 ) 116 (66.3 ) 22 (30.1 ) 59 (33.7 ) 4.864 101 147 76 (75.2 ) 91 (61.9 ) 25 (24.8 ) 56 (38.1 ) 0.028 0.584 0.005 0.013 0.026 0.346 0.949 0.000 0.756 0.P valuea0.Age (years)b ,47.8 47.8 Gender Female Male HBsAg Positive Negative AFP (ng/ml) ,20 20 Cirrhosis Yes No Tumor size (cm) ,5 5 Tumor multiplicity Single Multiple Differentiation Well-Moderate Poor-Undifferentiation Stage I I III V Vascular invasion Yes No Relapse Yes NoaChi-square test; Mean age; AFP, alpha-fetoprotein; HBsAg, hepatitis B surface antigen. doi:10.1371/journal.pone.0051703.tbIHC EvaluationSemi-quantitative IHC detection was used to determine the SIRT3 protein levels. A brown particle in nuclei was considered as positive labeling. Immunostain was scored using a 4-point scale (0?4) system according to the intensity of Pentagastrin custom synthesis staining and the percentage of positive cells. IHC evaluation was performed according to the method described before [21]. For each case, 1000 cells were randomly selected and scored. HCC sections were observed under light microscopy and the staining intensities scores were independently assessed by 2 pathologists (Dr. JP Yun and Dr. MF Zhang).Selection of Cutoff ScoreReceiver operating characteristic (ROC) curve analysis was employed to determine the cutoff score for tumor with low SIRT3 expression by using the 0,1-cr.Ined sections were reviewed by a senior pathologist to mark out representative areas. Using a tissue arraying instrument (Beecher Instruments, Sliver Spring, MD), each tissue core with a diameter of 0.6 mm was punched from the marked areas and re-embedded.Immunohistochemistry (IHC)Formalin-fixed and paraffin-embedded HCC sections with a thickness of 4 mm were dewaxed in xylene and graded alcohols, hydrated, and washed in phosphatebuffered saline (PBS). After pretreatment in a microwave oven, endogenous peroxidase was inhibited by 3 hydrogen peroxide in methanol for 20 min, followed by avidin-biotin blocking using a biotin-blocking kit (DAKO, Germany). Slides were then incubated with SIRT3 antibody, overnight in a moist chamber at 4uC, washed in PBS, and incubated with biotinylated goat anti-rabbit/mouse antibodies. Slides were developed with the Dako Liquid 3, ‘3diaminobenzidine tetrahydrochloride (DAB)+Substrate Chromogen System and counterstained with 22948146 hematoxylin.Western BlotCell or tissue lysates were boiled with 6X sodium dodecyl sulfate (SDS) loading buffer and then fractionated by SDS-PAGE. The proteins were transferred to PVDF membrane which was then incubated with a primary specific antibody for SIRT3 in 5 of non-fat milk, followed by a horse radish peroxidase (HRP)conjugated anti-rabbit second antibody. ECL detection reagent (Amersham Life Science, Piscataway, NJ, USA) was used to demonstrate the results.SIRT3 as a Prognostic Biomarker in HCCTable 1. Correlation between the clinicopathologic variables and SIRT3 expression in HCC.VariableSIRT3 protein All cases Low expression High expression x2 0.021 130 118 87 (66.9 ) 80 (67.8 ) 43 (33.1 ) 38 (32.8 ) 0.842 28 220 21 (75.0 ) 146 (66.4 ) 7 (25.0 ) 74 (33.6 ) 0.096 215 33 144 (67.0 ) 23 (69.7 ) 71 (33.0 ) 10 (30.3 ) 16.521 102 146 54 (52.9 ) 113 (77.4 ) 48 (47.1 ) 33 (22.6 ) 0.004 180 68 121 (67.2 ) 46 (67.6 ) 59 (32.8 ) 22 (32.4 ) 0.889 121 127 78 (64.5 ) 88 (69.3 ) 43 (35.5 
) 39 (30.7 ) 4.936 131 117 80 (61.1 ) 87 (74.4 ) 51 (38.9 ) 30 (25.6 ) 6.224 150 98 92 (61.3 ) 75 (76.5 ) 58 (38.7 ) 23 (23.5 ) 8.048 109 139 63 (57.8 ) 104 (74.8 ) 46 (42.2 ) 35 (25.2 ) 0.300 73 175 51 (69.9 ) 116 (66.3 ) 22 (30.1 ) 59 (33.7 ) 4.864 101 147 76 (75.2 ) 91 (61.9 ) 25 (24.8 ) 56 (38.1 ) 0.028 0.584 0.005 0.013 0.026 0.346 0.949 0.000 0.756 0.P valuea0.Age (years)b ,47.8 47.8 Gender Female Male HBsAg Positive Negative AFP (ng/ml) ,20 20 Cirrhosis Yes No Tumor size (cm) ,5 5 Tumor multiplicity Single Multiple Differentiation Well-Moderate Poor-Undifferentiation Stage I I III V Vascular invasion Yes No Relapse Yes NoaChi-square test; Mean age; AFP, alpha-fetoprotein; HBsAg, hepatitis B surface antigen. doi:10.1371/journal.pone.0051703.tbIHC EvaluationSemi-quantitative IHC detection was used to determine the SIRT3 protein levels. A brown particle in nuclei was considered as positive labeling. Immunostain was scored using a 4-point scale (0?4) system according to the intensity of staining and the percentage of positive cells. IHC evaluation was performed according to the method described before [21]. For each case, 1000 cells were randomly selected and scored. HCC sections were observed under light microscopy and the staining intensities scores were independently assessed by 2 pathologists (Dr. JP Yun and Dr. MF Zhang).Selection of Cutoff ScoreReceiver operating characteristic (ROC) curve analysis was employed to determine the cutoff score for tumor with low SIRT3 expression by using the 0,1-cr.