Cellular immunotherapy using irradiated lung cancer cell vaccine co-expressing GM-CSF and IL-18 can induce significant antitumor effects.

Hongwei Tian,Lei Dai,Lin Cheng,Hongxin Deng,Yiming Li,Gang Shi,Tao Du,Guoyou Yang,Yuquan Wei,Jianzhou Wang,Dechao Yu,Junfeng Zhang,Shuang Zhang,Xiaomei Zhang,Yang Yang,Fen Xu,Xiaolei Chen

doi:10.1186/1471-2407-14-48

Abstract

BackgroundAlthough the whole tumor cell vaccine can provide the best source of immunizing antigens, there is still a limitation that most tumors are not naturally immunogenic. Tumor cells genetically modified to secrete immune activating cytokines have been proved to be more immunogenic. IL-18 could augment proliferation of T cells and cytotoxicity of NK cells. GM-CSF could stimulate dendritic cells, macrophages and enhance presentation of tumor antigens. In our study, we used mouse GM-CSF combined with IL-18 to modify Lewis lung cancer LL/2, then investigated whether vaccination could suppress tumor growth and promote survival.MethodsThe Lewis lung cancer LL/2 was transfected with co-expressing mouse GM-CSF and IL-18 plasmid by cationic liposome, then irradiated with a sublethal dose X ray (100 Gy) to prepare vaccines. Mice were subcutaneously immunized with this inactivated vaccine and then inoculated with autologous LL/2 to estimate the antitumor efficacy.ResultsThe studies reported here showed that LL/2 tumor cell vaccine modified by a co-expressing mouse GM-CSF and IL-18 plasmid could significantly inhibit tumor growth and increased survival of the mice bearing LL/2 tumor whether prophylactic or adoptive immunotherapy in vivo. A significant reduction of proliferation and increase of apoptosis were also observed in the tumor treated with vaccine of co-expressing GM-CSF and IL-18. The potent antitumor effect correlated with higher secretion levels of pro-inflammatory cytokines such as IL-18, GM-CSF, interferon-γ in serum, the proliferation of CD4+ IFN-γ+, CD8+ IFN-γ+ T lymphocytes in spleen and the infiltration of CD4+, CD8+ T in tumor. Furthermore, the mechanism of tumor-specific immune response was further proved by 51Cr cytotoxicity assay in vitro and depletion of CD4, CD8, NK immune cell subsets in vivo. The results suggested that the antitumor mechanism was mainly depended on CD4+, CD8+ T lymphocytes.ConclusionsThese results provide a new insight into therapeutic mechanisms of IL-18 plus GM-CSF modified tumor cell vaccine and provide a potential clinical cancer immunotherapeutic agent for improved antitumor immunity.

Highlights

The whole tumor cell vaccine can provide the best source of immunizing antigens, there is still a limitation that most tumors are not naturally immunogenic
Preparation of irradiated LL/2 tumor cell vaccine co-expression IL-18 and GM-CSF Three eukaryotic expression plasmids expressing IL-18 alone, GM-CSF alone, or IL-18 and GM-CSF were generated as described in Methods
Taken together, we showed that vaccination with irradiated, autologous Lewis lung cancer cell LL/2 engineered by combination of IL-18 and GM-CSF improved the immunogenicity

Summary

Introduction

The whole tumor cell vaccine can provide the best source of immunizing antigens, there is still a limitation that most tumors are not naturally immunogenic. Tumor cells genetically modified to secrete immune activating cytokines have been proved to be more immunogenic. GM-CSF could stimulate dendritic cells, macrophages and enhance presentation of tumor antigens. Researchers have found that genetically modified tumor cell with secreted immune activating cytokines has the ability to enhance the immunogenic and induce systemic antitumor immune responses [9]. IL-18, IFN-γ-inducing factor, is secreted mainly by activated macrophages and DCs [10]. It could induce the proliferation and enhance the cytotoxicity of both T and NK cells [11]. Combination of IL-12 and IL-18 can play an important role in progression and metastasis of gastric cancer [19]

Methods

Results

Discussion

Conclusion