[Treatment of hepatocellular carcinoma by transfecting interleukin-12 and interleukin-2 fusion gene intrasplenically, an experimental study]

Abstract

Objective: To study the inhibitory effect of retroviral packaging cells injected intrasplenically encoding mouse interleukin-12 (mIL-12) and human interleukin-2 (hIL-2) fusion gene on the growth of hepatocellular carcinoma.

Methods: The retroviral vectors encoding mIL-12 gene, hIL-2 gene, and mIL-12 and hIL-2 genes, GCIL12EXPN, GCXEIL2PN, and GCIL12EIL2PN were constructed and then transfected into the retroviral packaging cells PA317 to construct cells PA317-GCIL12EXPN, PA317-GCXEIL2PN, and PA317-GCIL12EIL2PN. Rat hepatocellular carcinoma cells CBRH3 were implanted into the livers of Wistar rats to establish hepatoma animal model. Then the rats were divided into 5 groups to be injected intrasplenically with normal saline one day after the implantation (0.8 ml/rat, group I, n = 10), blank vector PA317-GCXEXPN one day after the implantation (10(7) cells/rat, group II, n = 10), PA317-GCIL12EXPN containing IL-2 gene (1 x 10(7) cells/rat 1, 3, 5, or 7 days after the implantation, group III, n = 40), PA317-GCXEIL2PN containing mIL-12 gene (1 x 10(7) cells/rat 1, 3, 5, or 7 days after the implantation, group IV, n = 40), and PA317-GCIL12EIL2PN containing IL-12-IL-2 fusion gene (1 x 10(7) cells/rat 1, 3, 5, or 7 days after the implantation, group V, n = 40) respectively. The rats surviving longer than 2 months were re-injected with hepatocellular carcinoma cells. The therapeutic effect, immune function and toxic effect were evaluated. CT was conducted on the liver before and after the experiment. Laparotomy was performed 3 and 7 days after treatment to resect some of the carcinoma tissues to undergo pathological examination and OX8 immunohistostaining. Serum mIL-12 and hIL-2 were detected one day before and 3, 7, 30, and 60 days after treatment.

Results: The average survival times of the rats treated with IL-12-IL-2 fusion gene at the first, third, fifth and seventh day after tumor implantation were 53.3 +/- 3.7 days, 49.3 +/- 4.2 days, 31.0 +/- 2.1 days, and 24.3 +/- 1.4 days respectively, longer than those treated with IL-2 gene (25.0 +/- 2.5 days, 23.5 +/- 2.0 days, 18.3 +/- 2.4 days, and 12.0 +/- 1.8 days respectively, P < 0.001), and those treated with IL-12 gene (39.0 +/- 4.8 days, 32.0 +/- 3.9 days, 23.0 +/- 2.5 days, and 19.4 +/- 2.1 days respectively, P < 0.001). Long survival (>or= 60 days) rate in the rats treated with IL-12-IL-2 fusion gene on the first and third day was 30%. The serum mIL-12 and hIL-2 levels in these rats remained high on the 60th day after treatment. The pathological study showed that the number of infiltrating lymphocytes in liver tumor tissues was increased in the IL-12-IL-2 fusion gene treatment group.

Conclusion: The retroviral packaging cell line injected intrasplenically encoding mIL-12 and hIL-2 fusion gene inhibits the growth of hepatocellular carcinoma significantly in rats. The therapeutical efficacy of early administration is superior to that of late one.