5.1　Whole-Cell Vaccine

The whole-cell vaccine contains all tumor cells and cell lysates, contains a full range of tumor-associated antigens, and simultaneously expresses MHC class I and II-restricted antigens,activates CD8+T cells and CD4+ helper T cells, and induces a comprehensive anti-tumor immune response.The use of tumor cells as vectors to prepare tumor vaccines is currently a means of preparing vaccines.Early studies have found that inactivated tumor cells can effectively activate the immune response of mice, which is just the origin of the development of tumor cell vaccines.For whole cell cancer vaccines, retroviral or adenoviral transduction of tumor cells to express molecules relevant for immune activation has been explored as another strategy to improve tumor immunogenicity.Mice could be immunized with tumor cells that were killed and engineered to express immune stimulatory cytokines [2].Tumor cell vaccines can be divided into autologous tumor cell vaccines and allogeneic tumor cell vaccines [3].Of many immunostimulatory mediators evaluated in the context of gene-modified tumor cell vaccines, GM-CSF emerged as the most potent in generating protective antitumor immunity [4].

A variety of whole-cell vaccines have been explored in human studies historically but with generally limited efficacy.Vaccination using irradiated, GM-CSF producing tumor cells (GVAX)consistently induced antitumor immunity in Phase 1/2 clinical trials for a number of tumors.22 patients with advanced chronic lymphocytic leukemia (CLL) whom received up to vaccine consisted of irradiated autologous tumor cells admixed with GM-CSF-secreting bystander cells,which induced significant expansion of tumor-reactive T cells [5].GVAX have shown the promising results in preclinical and phase II clinical trials.However, it’s failed to show better results in the phase III clinical trial [6].One recent research shown that preexisting melanoma with whole cell vaccines expressing alpha(1,3)-galactosyl epitopes effectively treated preexisting s.c.and pulmonary alpha Gal-negative melanoma (B16Null) tumors in the alpha(1,3)-galactosyltransferase knockout mouse model [7].AVAX Technologies (MO, USA) company has devised a novel approach to the immunotherapy of cancer based on modification of autologous tumor cells with the hapten,dinitrophenyl (DNP) and application together with BCG, and approved by FDA in 2005 for the treatment of melanoma.The clinical study shown that M-vax vaccine against grade III advanced melanoma.In 214 Stage III patients the 5-year overall survival rate was 44%, which compares favorably with the reported surgical rate of 20%-25% [8].

DCs are exceptional with respect to their ability to capture even small amounts of antigen for presentation.This is particularly true for “cross presentation”, whereby antigens captured from the extracellular space can be converted into peptides loaded onto MHC class I molecules; classically,MHC class I is associated with the presentation of peptides derived from antigens synthesized endogenously (e.g., viral antigens presented by MHC class I on the surface of infected cells) [9].DC vaccines are in the same category as whole-cell vaccines.As the most powerful full-time APC, DC is the key to initiating and regulating immune response.However, DCs in tumor patients have defects in activation or maturation, are unable to effectively initiate an immune response, and induce immune tolerance.Therefore, through the transformation of DC to make it play its ability to help overcome the state of immunosuppression.(https://www.daowen.com)

The first DC vaccine clinical trial was published in 1995.In this trial, patients with metastatic melanoma were injected with anautologous APCs pulsed with a synthetic MAGE-1 nonapeptide [10].This trial reveals that peptide-pulsed APC can induce response of tumor peptide-specific CTL in situ.Afterwards, a great number of research teams began to investigate the DC vaccines.Study advocated that loaded DC with tumor lysate as a DC vaccine showing objective responses in some metastatic melanoma patients [11].Besides, a phase II vaccine trials from 2003 to 2009 demonstrated a clinical benefit of melanoma patients treated with a DC based vaccine that mature-DCs were pulsed with autologous tumor lysate.This indicates DC vaccines pulsed with whole tumor antigens would be able to improve clinical responses of cancer patients [12].

It is an effective strategy to stimulate a strong immune response by in vitro incubation of autologous DCs loaded with TAA to prepare DC vaccines for reinfusion into patients.Sipuleucel-T(Provenge) was approved by the US FDA in April 2010.As the first approved therapeutic DC vaccine, Provenge expresses a recombinant fusion protein that produces prostatic acid phosphatase(PAP) and GMCSF for use in asymptomatic or mildly metastatic castration-resistant prostate cancer.The treatment has three parts.Patient cells are collected and a leukapheresis method is used to extract the antigen-presenting DC.The cell preparation is then sent to a corporate production facility where they are co-incubated with the fusion protein, which is taken up, processed, and presented on the cell surface.The PAP antigen is nearly universally expressed in prostate cancer cells, and the GM-CSF provides a maturation factor for the DC.In this activated antigen-presenting state, the DCs are then returned to the infusion center where they are readministered to the patient.Three courses of treatment are administered over a period of 6 weeks to trigger an immune response against PAP positive prostate cancer cells.A clinical study of 512 patients showed an OS of 25.8 months in the Provenge group and 21.7 months in the control group.Although the OS was only extended by 4.1 months compared to the control group, this result made Provenge to be an important milestone in the treatment of cancer vaccines [13].

In 2105, a research reported the results of DC vaccine targeting tumor stem cells.Five to 10%ALDHhigh CSCs were first isolated from squamous cell carcinoma SCC7 cells and melanoma D5 cells.The ALDHhigh CSCs were then lysed and loaded to DCs to generate CSC-DC vaccine.Control DC vaccine was prepared with lysates from unsorted, ALDHlow D5 cells and SCC7 cells.After local radiotherapy of mice, CSC-DC vaccine treatment effectively inhibited tumor growth and lung metastasis compared with control DC vaccine, indicating that CSC-DC vaccine could induce stronger immunoreaction.Thus, DC vaccine targeting CSC may hopefully be used for prevention of relapse.This study provides a new way for cancer vaccine targeting cancer stem cells.However, the effective method for the isolation and amplification of tumor stem cells for the cancer vaccines targeting CSC is rare [14].