[Induction of prostate cancer-specific CTLs with dendritic cells pulsed by different types of tumor antigens].

OBJECTIVE: To study the effectiveness of freeze-thaw antigens and acid eluted peptide antigens extracted from tumor cell-pulsed dendritic cells (DC) in inducing prostate cancer-specific cytotoxic T lymphocytes (CTL) in vitro. METHODS: Tumor antigens were extracted from the prostate cancer cell line PC-3 with the repeated freeze-thaw and weak acid elution methods. Peripheral blood mononuclear cells were cultured with recombinant human GM-CSF and IL-4 for inducing DCs in vitro. Then the DCs were pulsed with the two kinds of prostate cancer tumor antigens respectively and cultured with T cells for inducing CTLs. The activity of the tumor-specific CTLs were detected by LDH release assay. RESULTS: The protein content in the tumor antigens obtained from PC-3 (2 x 10(7)) by citric acid-phosphate buffer elution and that by the repeated freeze-thaw method were (212.2 +/- 7.9) microg and (963.0 +/- 25.3) microg, respectively. The two kinds of prostate cancer antigens-pulsed DCs had a significant role in inducing the PC-3 cell-specific CTLs, and the CTLs induced by acid-eluted peptide antigen-pulsed DCs exhibited an even more significant tumor-specific cytotoxicity than those induced by repeated freeze-thaw ([60.4 +/- 5.52]% vs. [43.7 +/- 4.11]%, P < 0.01). CONCLUSION: Both the weak acid elution and repeated freeze-thaw methods for extracting prostate cancer antigens can be used for in vitro sensitization of DCs. The DCs pulsed by either of the two kinds of antigens can activate CTLs, and the antigens extracted by weak acid elution are even more effective.

Progression of Large Lymphoma Is Significantly Impeded with a Combination of Gemcitabine Chemotherapy and Dendritic Cells Intra-Tumor Vaccination.

Relapsed, refractory lymphoma remains to be a challenge and lacks efficient treatment. Some tumor cells escape from treatment, become resistant to chemotherapeutic agents, and rapidly regenerate into large tumors. Lymphoma cells induce accumulation of Gr-1(+-)CD11b(+) myeloid derived suppressor cells (MDSCs) in lymphatic organs and their vicinity. MDSCs enable tumor cells to escape from immune cells mediated surveillance and attack. Gemcitabine is a chemotherapeutic agent that eliminates both tumor cells and MDSCs, improving the immune environment favorable for subsequent treatment. We evaluated the effects of low dose gemcitabine combined with intra-tumorally delivered dendritic cells (DCs) for the treatment of A20 large-size lymphoma. We showed that MDSCs increased markedly in lymphoma-bearing mice, and that gemcitabine significantly increased the apoptosis of MDSCs. Treatment of lymphoma with either gemcitabine or intra-tumoral DCs alone could not inhibit tumor growth or rescue lymphoma-bearing mice. Treatment of lymphoma with small dose gemcitabine followed by intra-tumorally injected DCs significantly improved the efficacy of either individual treatment by reducing MDSCs, inducing onsite DCs maturation, eliminating tumor cells, inhibiting tumor growth and relapse, and extending the survival of the lymphoma-bearing mice, partly through the induction of the IFNγ secreting cells and the activation of cytotoxic lymphocytes. We showed that NK cells and CD8(+ )T cells were the major effectors to mediate the inhibition of tumor growth. Thus, the observation that gemcitabine synergizes DCs mediated immunotherapy to improve the efficacy of large size lymphoma treatment provides an experimental basis for the combination of chemotherapy and immunotherapy for the efficient treatment of relapsed or refractory lymphoma.