Induction of CTLs by DCs pulsed with K-ras mutant peptide on the surface of nanoparticles in the treatment of pancreatic cancer.

The aim of this study was to investigate the role of specific cytotoxic T lymphocytes (CTLs) activated by dendritic cells (DCs) presenting cationic nanoparticles with the K-ras (12-Val) mutant peptide in the killing of different pancreatic cancer cell lines in vivo and in vitro. Peripheral blood DCs were induced by rhGM-CSF and IL-4 and cultured. DCs were sensitized by whole antigen of PANC-1 with expression of K-ras mutant, K-ras mutant peptide (K-ras+peptide) and cationic nanoparticles with K-ras mutant peptide (K-ras+peptide-CNP), respectively. Cell surface markers were measured by flow cytometry. Lymphocyte proliferation was detected by the 3H-TdR test, and IL-12 and IFN‑γ secretion was detected by ELISA. 125I-UdR was used to measure the killing effect of CTLs. The antitumor activity of CTLs in tumor-bearing nude mouse models prepared with PANC-1 and SW1990 cells was evaluated. Results showed that, compared with K-ras+peptide, low concentrations of K-ras+peptide-CNP were effectively presented by DCs (P<0.05). CTLs induced by DCs pulsed with whole tumor antigen had a significantly greater killing effect (P<0.05) on PANC-1 and SW1990 pancreatic cancer cells compared with K-ras+peptide- and K-ras+peptide-CNP-induced CTLs. CTLs induced by DCs pulsed with K-ras+peptide and K-ras+peptide- CNP had a specific killing effect (P<0.05) on PANC-1 cells and no effect (P>0.05) on SW1990 cells. In conclusion, cationic nanoparticles with the K-ras (12-Val) mutant peptide can be effectively presented by DCs at a low concentration. CTLs induced by K-ras+peptide-CNP had specific killing activity for the pancreatic cancer cell line with the K-ras mutant and significantly inhibited tumor growth and increased the survival time of tumor-bearing nude mice. Although this study confirmed that whole cell antigen induced a good antitumor immune response, the possibility of immune tolerance and autoimmunity which has been previously proven contribute to the difficulty in the application of this DC vaccine.