A dynamic study of correlation between the MR diffusion weighted imaging findings and the expression of proliferation-related and metastasis-related genes in rabbit models of liver VX₂ tumor before and after chemoembolization

Objective: To investigate the correlation between the apparent diffusion coefficient (ADC) values and the expression of proliferating cell nuclear antigen (PCNA), Bax, non-metastasis 23(nm23) and E-cadherin (E-cad) genes in rabbit models of liver VX₂ tumor before and after chemoembolization. Methods: Forty rabbit models of liver VX₂ tumor were divided into four groups with 10 rabbits in each group. The first group was the control group which didn't undergo chemoembolization. The second, third and fourth groups underwent chemoembolization, and diffusion weighted imaging (DWI) was performed at 16 h, 32 h and 48 h after chemoembolization respectively. The pathological and immunohistological examinations were carried out right after DWI. The sampling areas included the normal liver parenchyma around the tumor, the outer- layer area, the peripheral area, and the central area. The expression indices of PCNA, Bax, nm23, E-cad in all the samples were recorded and their correlation with corresponding ADC value were analyzed. Results: (1) PCNA expression indices in the outer layer area, the peripheral area and central area of VX₂ tumors(65.1%, 74.7%, and 59.0% respectively) were higher than that in the area of normal parenchyma around tumor (8.3%) (X²=19.08, P<0.01). The nm23, Bax or E-cad expression indices in the the outer layer area, the peripheral area and the central area of VX₂ tumors (nm 23: 1.7%, 0.4% , and 6.2% respectively; Bax: 2. 0%, 1.2% , and 2. 2% respectively; E-cad:6.2%, 2.0%, and 1.6% respectively) were lower than that in the area of normal parenchyma around tumor (nm23 16.5%; Bax 40.0%; E-cad 78.0%. χ²=12.86, 20.17, and 22.20 respectively; P<0.01). (2) The PCNA expression indices in the area of VX₂ tumor periphery were 83.0%, 92.6% and 85.7% in 16 h group, 32 h group and 48 h group respectively after chemoembolization and those of nm23 expression indices were 2.3%, 7.4%, 4.2% and those of Bax expression index were 0.8%, 0.5%, 0.9% and those of E-cad expression indices were 2.8%, 1.0%, 1.1%. The PCNA and nm23 expression in the area of VX₂ tumor periphery increased at the beginning and then decreased (χ²=14.37, 8.94; P< 0.05). The difference of Bax and E-cad expression before and after chemoembolization was insignificant (χ²=1.98, 3.88; P>0.05). (3) When b-value was 100 s/mm², ADC values of VX₂ tumor periphery were respectively(1.71 ± 0.27) x 10^-3, (1.24 ± 0.22) x 10^-3 (1.48 ± 0.37) x 10^-3 and (1.57 ± 0.23) x 10^-3 mm²/s in control group, 16 h group, 32 h group and 48 h group after chemoembolization. There was a correlation between PCNA expression indices and ADC values in the area of VX₂ tumor periphery (r=-0.68, P=0.000). There was no correlation between nm23, Bax or E-cad expression indices and ADC values in the areas of VX₂ tumor periphery (r=-0.20, 0.17, and -0.10 respectively; P>0.05). Conclusions: The potential of VX₂ tumor infiltration and metastasis will decrease after chemoembolization in the long-run, while the proliferation ability will increase within a short period of time. The ADC may reflect the proliferation of VX₂ tumor cells. (authors)