Study on anti-tumor effects of murine dendritic cells pulsed with PEP3-KLH peptide on prostate cancers

Abstract

Objective To explore the effects of anti-tumor immunity induced by dendritic cells (DCs) vaccine pulsed with PEP3-KLH (keyhole limpet hemocyanin) on induction of specific immunity against prostate cancers. Methods DCs were propagated from bone marrow of C57BL/6 mice in vitro with granulocyte-macrophage colony stimulating factor (GM-CSF) and interleukin-4 (IL-4). On day 5 of culture, DCs were harvested and incubated with PEP3-KLH or KLH. Then the DC vaccine was inoculated into C57BL/6 mice by subcutaneous injection for three times with an interval of two weeks. One week after the last vaccination, the levels of IL-2, IL-12, and interferon (IFN)-γ were measured with enzyme-linked immunosorbent assay (ELISA) kit. The aforementioned immunized mice with DC vaccines were challenged with transgenic adenocarcinoma of mouse prostate (TRAMP)-C2 tumor cells, the tumor growth curve was drawn, and survival rate was checked and compared. The cytotoxic T lymphocyte (CTL) activity induced by DCs was tested with lactate dehydrogenase (LDH) release method. The percentages of CD3+ , CD4+ , or CD8+ T cells in tumor-infiltrating lymphocytes (TILs) were determined with flow cytometry. Results PEP3-KLH-DC group stimulated the body and induced higher levels of secreted IL-2, IL-12, and IFN-γ compared to DCs control and KLH-DC groups (P<0.01). The tumor of mice vaccinated with PEP3-KLH-DC grew significantly slower than that injected with DCs or KLH-DC (P<0.01). Compared to the others, the survival rate in PEP3-KLH-DC group raised remarkably (P<0.01). PEP3-KLH-DC group induced more outstanding specific CTL activities of killing tumor cells than DCs control group and KLH-DC group(P<0.01), and the cytotoxicities of TILs in PEP3-KLH-DC group was significantly enhanced (P<0.01). The percentages of CD3+ , CD4+ , or CD8+ T cells in TILs (40.9%, 34.1%) in PEP3-KLH-DC group were significantly higher than those in DC-KLH (27.3%, 5.2%) or DCs (26.2%, 5.1%) group. Conclusions PEP3-KLH-DC vaccine can inhibit effectively tumor growth, enhance long-term survival in mice, intensify the local immunologic function of tumor, and elicit and promote profound specific anti-prostate cancer cellular immune responses. Key words: Receptor, epidermal growth factor/BI; Dendritic cells; Vaccines/BI/PD; Prostatic neoplasms/IM/TH