[Specific immune against pancreatic cancer induced by dendritic cells pulsed with mutant K-ras peptide]

To investigate whether dendritic cells (DCs) pulsed with mutant K-ras peptide (12-Val) can induce efficiently specific anti-tumor immune response against pancreatic cancer.

Immature DCs were isolated from the peripheral blood of a volunteer and were pulsed with synthesized mutant K-ras peptide (YKLVVVGAV). When the DCs were matured the expression rate of Kras antigen epitope on the DC's surface was detected by mono antibody (K-ras-12-Val). Autogeneic and homologous T cells were mixed with the mutant K-ras peptide-pulsed DCs. Human pancreatic cancer cells of the line Patu8988 were mixed with cytotoxic T lymphocytes (CTLs) cultured for 5 days, and the killing effects of the CTLs on the cells was assessed by MTT method. Patu8988 cells were injected subcutaneously into nude mice, cancer cells were obtained from the tumor masses and injected subcutaneously into other nude mice to establish mice models of pancreatic cancer. Then 32 mice with pancreatic cancer were randomly divided into 4 equal groups: control group, K-ras specific CTL intra-tumor injection group, CTL caudal vein injection group, and IL-2 activated non-specific CTL intra-tumor injection group. The tumor size was measure regularly. Immunohistochemistry was used to detect the pathological analysis of the transplanted tumors.

The mutational epitope (K-ras-12-Val) induced by mutant peptide could be found on the DCs'surface efficiently. After co-incubation with the mature DCs pulsed with tumor antigen the autogeneic T cells were activated, the CD8 T cells accounted for (44.8 +/- 2.1)%. Without damage the normal tissue cells, the killing rate of activated K-ras specific CTLs to the tumor cell when the ratios of CTL: Patu8988 cells were 10:1, 20:1, and 50:1 were (21.2 +/- 1.9)%, (32.4 +/- 2.1)%, and (45.7 +/- 5.3)% respectively, all while the killing efficiency significantly superior to those of the non-specific activated T lymphocyte (all P < 0.05). Eight days after CTL injection into the nude mice the tumor size of the intratumor injection group was (68 +/- 13) mm3, significantly smaller than those of the control group and IL-2 activated non-specific CTL intra-tumor injection group [(87 +/- 14) mm3 and (79 +/- 19) mm3, both P < 0.05]. The survival rates of the nude mice of the K-ras specific CTL intra-tumor injection group, CTL caudal vein injection group, and IL-2 activated non-specific CTL intra-tumor injection group were all significantly higher than that of the control group (all P < 0.05), and the survival rate of the K-ras specific CTL intra-tumor injection group was significantly higher than that of the IL-2 activated non-specific CTL intra-tumor injection group (P < 0.05). Immunohistochemical staining confirmed that K-ras specific CTL had the ability to move toward tumor.

DCs pulsed with mutant K-ras peptide (12-Val) induces specific anti-tumor immune response in pancreatic cancer efficiently.