| Objective It has been shown that interleukin-12(IL-12) canstimulate the proliferation, activity and cytotoxicity of T cells and NK cells. This cytokine has the ability to augment activity of macrophages, induce them to produce many cytokines. It can also regulate the development of Thl cells from ThO cells, which result in the improvement of cellular immune response. These results indicate that IL-12 plays an important role in anti-tumor immune response. However, the toxicities caused by systemic delivery of IL-12 protein limit the application of IL-12 in clinic. After local delivery of IL-12 plasmid, IL-12 can be expressed and secreted by the cells of local tissues. A large amount of IL-12 in local tissues can improve the micro-circumstance of tumor and enhance anti-tumor immune response. Moreover, the level of IL-12 in serum is so low that can prevent the toxicities caused by systemic delivery of IL-12 protein. Although many of chemotherapy drugs are immuno-suppressive, some drugs such as CY%DOX>Mit-C can result in immunopotentiating activity in low dose. To investigatethe therapeutic efficiency of combining IL-12 plasmid plus low dose CY on mice melanoma, the cytotoxicity of peritoneal macrophages and NK cell activity of splenic cells were abserved.Materials and Methods Male C57BL/6 mice between 6-8 wk of age; L12HK Yac-K Bl6 cells were maintained in RPMI 1640 containing 10% PCS and 2 mM glutamine; plasmids were maintained in 4"C-. plasmids was extracted with alkaline lysis and purified with hydroxybenzene, chloroform precipitation; For tumor implantation,1X105 tumor cells were injected in a 0.1-ml volume in PBS s.c. on the left leg of mice. They were given various treatment after twenty-four hours: plasmids were given by i.m. injection in O.lml of PBS, lOOfig, once every other day for three total injections; CY were given at a single dose of 20mg/kg in 0.1 ml of saline via s.c. injection. The mice of control group were given equal volume of saline correspondingly. The cytotoxicity of peritoneal macrophages and NK cell activity of splenic cells were observed with MTT and the NO concentration were measured, with Gress.Results: K The tumor weight of control, CY and combination group reached 1.15 ?0.18, 0.47 ?0.16 and 0.21 ?0.08 gram respectively, there is significant difference in the CY, combination group with the control group(p<0.05 and p<0.01), it also showed that application of pCmIL-12 plus CY had synergetic effect on anti-tumor.2> The NK activity and M(p cytotoxicity of group pCmIL-12 and combination (52.05 ?0.18%, 64.46 ?.40%;56.75?3.06%, 70.79 ?.13%, standard deviation SD) are higher than that of control group (31.52 ?.75%, 34.46 ?.60%), there is significant difference between them, it showed that there is interaction between the CY and pCmIL-12 theraputic group, the cytotoxicity of peritoneal macrophage were increased, the NK cell activity of splenic cells were significantly augmented..3 -. The NO concentration of combination and pCmIL-12 group are( 21.19 ?.26, 22.85 + 1.58 [imol/L) respectively, there is a significant difference between the control group which NO concentration is (13.48 ?1.57 n mol/L)(p<0.05), but it didn't show that there is interaction which increases the NO releasing in the CY and pCmIL-12 theraputic group.Conclusions 1 ^ The administration of pCmIL-12 plus CY cansignificantly inhibit the growth of transplant melanoma;2^ The cytotoxicity of NK cells and peritoneal macrophages can be significantly augmented synergeticalty by intramuscular (i.m.) and intradermal (i.d.) delivery of pCmIL-12 and CY;3* It has not been defined whether it has synergetic effects on NO production after treatment with pCmIL-12 plus CY. |
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