Nude mice multi-drug resistance model of orthotopic transplantation of liver neoplasm and Tc-99m MIBI SPECT on p-glycoprotein

Abstract

Aim: To establish a model of drug-resistant neoplasms using a nude mice model, orthotopic transplantation of liver neoplasm and sporadic abdominal chemotherapy.

Methods: Hepatocellular carcinoma cells HepG2 were cultured and injected subdermally to form the tumor-supplying mice. The orthotopic drug-resistant tumors were formed by implanting the tumor bits under the envelope of the mice liver and induced by abdominal chemotherapy with Pharmorubicin. Physical examination, ultrasonography, spiral CT and visual inspection were used to examine tumor progression. RT-PCR and immunohistochemistry were used to detect expression of mdr1 mRNA and its encoded protein p-glycoprotein (p-gp). Tc-99m sestamibi scintigraphy was performed by obtaining planar abdominal images at 20 min after injection, and the liver/heart ratios were calculated.

Results: Post-implantation mortality was 0% (0/25), tumor implantation success was 90% (22/25), and the rate of implanting successfully for the second time was 100% (3/3). Tumor induction using Pharmorubicin was 80% (16/20). The mdr1 mRNA expression of the induced group was 23 times higher than that of the control group, and p-gp protein expression was 13-fold higher compared to the control group. The liver/heart ratio (as assessed in vivo, using Tc-99m radiography) was decreased significantly in the induced group as compared to the control group.

Conclusion: We have established an in vivo model of mdr1 in nude mice by orthotopic transplantation of liver neoplasm coupled to chemotherapy. We propose that identification of drug resistance as characterized by decreased 99mTc-ppm radiography due to enhanced clearance by p-gp may be useful in detecting in vivo drug resistance, as well as a useful tool in designing more effective therapies.

Figure 1

The specimen and images by Doppler and CT. A: Specimen of tumor model after 15 d of implantation; B: specimen of tumor model after 25 d of implantation; C: color Doppler image of tumor model after 25 d of implantation; D: contrast-enhanced abdominal CT image of tumor model after 20 d of implantation.

Figure 2

Mdr1 mRNA expression. lane A: Control group; lane B: induced group; lane C: 100-bp marker.

Figure 3

Expression of p-gp by using immunohistochemistry (SABC ×200).

Figure 4

SPECT images of the nude mice model. A: SPECT of control group showing dense radioactivity; B: SPECT of control group showing deficiency radioactivity.