Potent systemic antitumor immunity induced by vaccination with chemotactic-prostate tumor associated antigen gene-modified tumor cell and blockade of B7-H1

Therapeutic Cancer Vaccines

Cancer is one of the major leading death causes of diseases. Prevention and treatment of cancer is an important way to decrease the incidence of tumorigenesis and prolong patients' lives. Subversive achievements on cancer immunotherapy have recently been paid much attention after many failures in basic and clinical researches. Based on deep analysis of genomics and proteomics of tumor antigens, a variety of cancer vaccines targeting tumor antigens have been tested in preclinical and human clinical trials. Many therapeutic cancer vaccines alone or combination with other conventional treatments for cancer obtained spectacular efficacy, indicating the tremendously potential application in clinic. With the illustration of underlying mechanisms of cancer immune regulation, valid, controllable, and persistent cancer vaccines will play important roles in cancer treatment, survival extension and relapse and cancer prevention. This chapter mainly summarizes the recent progresses and developments on cancer vaccine research and clinical application, thus exploring the existing obstacles in cancer vaccine research and promoting the efficacy of cancer vaccine.

Reprogramming the tumor microenvironment: tumor-induced immunosuppressive factors paralyze T cells

It has become evident that tumor-induced immuno-suppressive factors in the tumor microenvironment play a major role in suppressing normal functions of effector T cells. These factors serve as hurdles that limit the therapeutic potential of cancer immunotherapies. This review focuses on illustrating the molecular mechanisms of immunosuppression in the tumor microenvironment, including evasion of T-cell recognition, interference with T-cell trafficking, metabolism, and functions, induction of resistance to T-cell killing, and apoptosis of T cells. A better understanding of these mechanisms may help in the development of strategies to enhance the effectiveness of cancer immunotherapies.

Chemokines as Cancer Vaccine Adjuvants

We are witnessing a new era of immune-mediated cancer therapies and vaccine development. As the field of cancer vaccines advances into clinical trials, overcoming low immunogenicity is a limiting step in achieving full success of this therapeutic approach. Recent discoveries in the many biological roles of chemokines in tumor immunology allow their exploitation in enhancing recruitment of antigen presenting cells (APCs) and effector cells to appropriate anatomical sites. This knowledge, combined with advances in gene therapy and virology, allows researchers to employ chemokines as potential vaccine adjuvants. This review will focus on recent murine and human studies that use chemokines as therapeutic anti-cancer vaccine adjuvants.

Chemokine-based immunotherapy: delivery systems and combination therapies

A major role of chemokines is to mediate leukocyte migration through interaction with G-protein-coupled receptors. Various delivery systems have been developed to utilize the chemokine properties for combating disease. Viral and mutant viral vectors expressing chemokines, genetically modified dendritic cells with chemokine or chemokine receptors, engineered chemokine-expressing tumor cells and pDNA encoding chemokines are among these methods. Another approach for inducing a targeted immune response is fusion of a targeting antibody or antibody fragment to a chemokine. In addition, chemokines induce more effective antitumor immunity when used as adjuvants. In this regard, chemokines are codelivered along with antigens or fused as a targeting unit with antigenic moieties. In this review, several chemokines with their role in inducing immune response against different diseases are discussed, with a major emphasis on cancer.

Dendritic cell transfected with secondary lymphoid-tissue chemokine and/or interleukin-2 gene-enhanced cytotoxicity of T-lymphocyte in human bladder tumor cell S in vitro

OBJECTIVES

The aim of this study was to investigate whether dendritic cells (DCs) transfected with human secondary lymphoid-tissue chemokine (hSLC) and human interleukin-2 (hIL-2) genes are capable of improving DC's proliferation and to produce a marked antitumor effect in vitro combined with T-lymphocyte (TC).

METHODS

SLC gene primer was designed based on the corresponding gene sequence in GenBank. The Kpn I site was introduced into the upstream of the primer and Xho I site into the downstream. The SLC gene was amplified with the template of pET32a(+)-SLC by polymerase chain reaction. SLC was cloned into pBudCE4.1/IL-2 (TRAIL was cut from pBudCE4.1/TRAIL- IL-2 before) to construct recombinant plasmid pBudCE4.1/SLC-IL-2(PSI). DCs were transfected with pBudCE4.1/SLC-IL-2 by gene electric transfection. Protein expression was determined with Western blot and enzyme-linked immunosorbent assays. Cytotoxicity of TC and DC against the human bladder tumor cell were examined by chromium release assay. Flow cytometric analyses were performed to determine the apoptosis of tumor cells and the percentage of Treg.

RESULTS

A high level of expression of SLC and IL-2 was observed in DCs transfected with SLC and IL-2 genes. The mean production of IL-2 was 19.8 +/- 2.5, 511.10 +/- 52.36, and 541.3 +/- 62.04 ng/10(6) cells/24 hours in the DC/vector, DC/IL-2, and DC/SLC-IL-2, respectively. The mean SLC production was 29.8 +/- 4.43, 506.10 +/- 42.36, and 567.34 +/- 52.05 ngs/10(6)cells/24 hours in the DC/ vector, DC/SLC, and DC/SLC-IL-2, respectively. Cytotoxicity to bladder cancer cells was increased. The mean cytotoxicity (the effector/target ratio, 40:1) of TC-DC/parental, TC-DC/IL-2, TC-DC/SLC, and TC-DC/SLC-IL-2(TDSI) to the human bladder cancer cells was 32.1 +/- 5.5%, 63.5 +/- 6.6%, 78.1 +/- 9.63%, respectively. The apoptotsis rate of bladder cancer cells treated with TDSI was 18.6% by flow cytometry. Treg cells' percentage was very small in the DC medium.

CONCLUSIONS

SLC and IL-2 were produced by autocrine in DCs transfected with SLC and IL-2 genes. DC/SLC-IL-2 can promote DC proliferation, while TC-DC/SLC-IL-2 and TC-DC/SLC could strongly enhance significant cytotoxicity against bladder cancer cell that was induced by the coculture of DCs (transfected with SLC and IL-2) and TC.

Novel chemotactic-antigen DNA vaccine against cancer

Dendritic cells play a pivotal role in immune induction. Dendritic cells perform antigen uptake, processing and presentation to T cells only when they are matured and in the functional state. In the development of a vaccine, it is of utmost importance to consider how to make dendritic cells' functions immunologically adequate. In this paper, we report the development of a series of antitumor DNA vaccines with similar structural framework, in which a gene encoding tumor-associated antigenic peptide is ligated upstream to the gene coding secondary lymphoid-tissue chemokine and downstream to the gene encoding the Fc portion of IgG (named chemotactic-antigen DNA vaccine [CADV]). CCR7(+) T, B, natural killer and dendritic cells can be attracted by secondary lymphoid-tissue chemokine, and Fc facilitates antigen uptake via Fc receptors expressed on dendritic cells. In a series of experiments in mice vaccinated by CADV with such tumor-associated antigenic specificities as HPV-16 E7, PSA-PSM-PAP, HER-2/neu, p53 and hTERT, CADV can attract immune cells to the vaccine inoculation site, remarkably inhibit tumor growth and extend survival time in tumor-bearing mice. The antitumor effect is more efficacious than that in mice treated with SLC-Ag or Ag-Fc hybrid gene. Tumor-associated antigenic-specific cytotoxic T lymphocytes can be induced by in vitro experiment in a human system. When combined with measures blocking the negative immune feedback circuits, the therapeutic effect of the vaccine can be further enhanced. Large-scale production of CADV is possible for clinical application.

Inhibition of dendritic cell generation and function by serum from prostate cancer patients: correlation with serum-free PSA

Tumor produces a number of immunosuppressive factors that block maturation of dendritic cells (DCs). Here, we demonstrated that endogenous factors presented in the serum of patients with prostate cancer (CaP) inhibited the generation of functionally active DCs from CD14+ monocytes in vitro. We have shown a significant inhibitory potential of serum obtained from patients with CaP and benign prostate hyperplasia benign prostatic hyperplasia (BPH) when compared with serum from healthy volunteers. As assessed by flow cytometry, expression of CD83, CD86, and CD40 molecules was strongly inhibited by CaP and BPH serum. In addition, these DCs were weak stimulators of allogeneic T cell proliferation when compared with DCs produced in the presence of healthy volunteer serum. Statistical analysis of the results revealed a positive relationship between the inhibition of expression of DC markers CD83 and CD80 and the levels of serum-free prostate-specific antigen (PSA). These data suggest that the DC system may be impaired in CaP patients.