OBJECTIVETo 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.

METHODSTumor 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.

RESULTSThe 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).

CONCLUSIONBoth 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.