[Experimental study on monitoring gene expression by noninvasive method in rabbit VX2 liver tumor model].

Objective: To investigate the feasibility of monitoring therapeutic effect of adenovirus vector containing IL12-IRES-CKb gene on a rabbit VX2 liver tumor model by using phosphorous-31 magnetic resonance spectroscopy (31P MRS).

Methods: A total of 18 healthy New Zealand White rabbits were used to generate animal models by implanting VX2 tumor chips into livers through laparotomy. Tumor-bearing animals were randomly divided into three groups and were injected with AdCMVIL12-IRES-CKb, AdCMV-Empty and saline respectively via ear veins. 31P MRS scan was performed after animals were fed with creatine solution for five days. Animals were euthanized thereafter and tumors were removed for pathological examination, immunohistochemistry (IHC) staining and protein analysis (Western blot).

Results: The intrahepatic and seral expressions of creatine kinase (CKb) and IL-12 were detected only in AdCMVIL12-IRES-CKb group. Tumor diameters pre- and post- treatment in three groups were 1.63+/-0.04 vs 1.62+/-0.03 in AdCMVIL12-IRES-CKb group (P = 0.229), 1.59+/-0.05 vs 1.84+/-0.11 in AdCMV-Empty group (P = 0.003) and 1.60+/-0.02 vs 2.07+/-0.12 in saline group (P = 0.001), respectively. Pcr Changes between pre- and post- treatment among the three groups were compared (F = 6.235, P value is less than 0.05). PCr increased significantly in AdCMVIL12-IRES-CKb group as compared to AdCMV-Empty (P = 0.004) and saline group (P = 0.049), whereas no change found between AdCMV-Empty and saline group (P = 0.153).

Conclusion: 31P MRS, an effective and non-invasive functional imaging method, can be used to monitor the therapeutic effect of adenovirus vector containing IL12-IRES-CKb gene on rabbit VX2 liver tumor model through detecting metabolic product of imaging reporter gene CKb (pCr).