Methods Tumor cells suspension was prepared by in vitro culture of liver cancer McA-RH7777 cells, and 50 clean SD rats were injected intrahepatically to establish a liver cancer model. One week after modeling, 40 liver cancer model rats were randomly selected and divided into an experimental group (n=26) and a control group (n=14) according to the simple sampling method. The liver tumors of the experimental group rats were treated with electrical pulses at a field intensity of 2 000 V/cm, while the tumors of the control group rats were treated with pulses at a field intensity of 0, frequency of 1 Hz and pulse width of 100 μs. Blood samples were collected from tail vein on 3 and 1 d before operation and 1, 7, 14, 21 and 30 d after operation, and serum biochemical indexes [alanine aminotransferase (ALT), aspartate aminotransferase (AST), creatinine, urea nitrogen, creatine kinase (CK), lactate dehydrogenase (LDH)] and the tumor marker alpha-fetoprotein (AFP) were monitored. The changes of tumor length was recorded at 1 d before operation and 7, 14, and 21 d after operation in the two groups of rats, and the survival time was recorded at 60 d after operation, in the two groups of rats, respectively, and the related complications were recorded during the treatment process. Two rats in the experimental group and the control group were randomly sacrificed 30 d after operation. The expression levels of cysteine aspartic acid protease-3 (Caspase-3), B-cell lymphoma-2 proto oncogene (Bcl-2), Bcl-2 related X protein (Bax) in the tumor tissues of the target area of the ablation of the rats in the two groups were detected. Lignin-eosin staining, vascular endothelial growth factor (VEGF) immunohistochemical observation of histomorphological changes, KI67 staining, TUNEL staining, cell proliferation rate and cell apoptosis rate were calculated. Data were analyzed by t test, repeated measures, Kaplan-Meier curves and chi-square test.
Results ALT, AST, CK, LDH level were compared at different time points in the experimental group at 3, 1 d before operation and 1, 7, 14, 21, 30 d after operation, the differences were statistically significant (F=41.458, 39.842, 33.343, 52.335; with P values above 0.05), there were no differences in creatinine and blood urea nitrogen at different time points in rats (F=0.702, 2.429; with P values above 0.05). ALT and AST were compared at 3, 1 d before operation and 1, 7, 14, 21, 30 d after operation in the control group, the differences were statistically significant (F=12.267, 3.646; with P values below 0.05), and there were no statistically significant differences in creatinine, blood urea nitrogen, CK and LDH at different time points(F=0.885, 1.100, 1.773, 1.338; with P values above 0.05). There were no statistically significant differences in the levels of ALT, AST, creatinine, blood urea nitrogen, CK, and LDH between the experimental group and the control group at 1 and 3 d before operation (with P values above 0.05). There were obvious differences in ALT and AST at 1, 21, and 30 d after operation between the experimental group and the control group and the differences were statistically significant (t=5.414, -9.993, -9.362; 4.345, -4.802, -7.159; with P values below 0.05). There were no statistically significant differences in creatinine and blood urea nitrogen at 1, 7, 14, 21, and 30 d after operation between the two groups (t=0.651, 0.322, 0.045, -0.760, -0.741; 4.345, 0.784, -1.835, -4.802, -6.415; with P values above 0.05). CK and LDH were compared between the experimental group and the control group at 1 and 7 d after operatio, the differences were statistically significant (t=5.613, 4.437, 7.817, 5.183; with P values below 0.05). The tumor marker AFP levels were (4.63±0.53), (4.84±1.63), (5.54±1.96), (3.87±2.19), (2.34±0.28), (1.61±0.51), (1.18±0.36) ng/L at 3, 1 d before operation and 1, 7, 14, 21, 30 d after operation in the experimental group, the difference was statistically significant (F=44.339, P<0.05). The tumor marker AFP levels of the control group at each time point were (4.44±0.91), (4.61±0.91), (4.86±0.95), (5.55±1.08), (6.10±1.42), (6.93±1.80), (6.70±2.686) ng/L, the difference was statistically significant (F=6.184, P<0.05). At 3 and 1 d before operation, there were no significant differences in AFP levels between the experimental group and the control group (t=0.862, 0.501; P=0.414, 0.619); at 7, 14, 21, and 30 d after operation, the difference between the experimental group and the control group were statistically significant (t=-2.682, -9.004, -10.809, -7.762; with P values below 0.05). The tumor length diameter of the experimental group were (11.2±3.1), (8.1±2.3), (5.3±1.6), (3.5±1.1) mm at 1 d before operation and 7, 14, 21 d after operation, respectively, while the tumor length diameter of the control group were (9.8±2.1), (14.1±2.7), (17.8±3.7), (14.4±2.7) mm at each time point. There was no statistically significant difference in tumor length diameter between the two groups at 1 d before operation(t=1.526, P=0.135). At 7, 14, and 21 d after operation, the differences in the length diameter between the experimental group and the control group were statistically significant (t=-7.330, -14.800, -18.244; with P values below 0.05). Compared with the control group 30 d after operation, the results of protein blotting showed that the expression levels of Caspase-3 and Bax increased and Bcl-2 decreased in the experimental group. Thirty days after surgery, hematoxylin-eosin staining was performed on tumor tissue. In the experimental group, a large number of tissue necrosis and obvious apoptotic areas were observed, while the cell duct results remained intact. No obvious destruction of tumor cells was observed in the control group. Thirty days after surgery, immunohistochemical staining of VEGF was performed on tumor tissues. In the experimental group, the cell structure arrangement was still clear, no obvious cell destruction was observed, and only a small amount of brown-yellow positive staining (1+ , moderate staining) was observed. In the control group, the arrangement of cells was disordered, with a large amount of brown-yellow positive staining (4+ , strong staining). Thirty days after surgery, the tumor tissues were stained with KI67 immunohistochemistry. In the experimental group, the cell structure arrangement was intact, no obvious damage was observed, and only a small amount of brown-yellow positive staining (1+ , weak staining) was observed. In the control group, the tissue structure was disordered, and the cells showed a large number of brown-yellow positive staining (4+ , strong staining). TUNEL staining was performed on tumor tissue 30 days after surgery. In the experimental group, the cell arrangement was slightly disordered and the structure of the pipeline was unclear. In the control group, the tissues were neatly arranged with only a small amount of brown-yellow positive staining. The tumor cell proliferation rates of the experimental group and the control group were (2.8±0.8)% and (43.1±3.8)%, respectively, and the difference was statistically significant (t=3.765, P<0.05). TUNEL staining showed strong staining in the experimental group and weak staining or no staining in the control group, the apoptosis rate of tumor cells in the experimental group and the control group were (76.85±10.27)% and (2.56±1.67)%, respectively, and the difference was statistically significant (t=4.456, P<0.05).