Intratumoral administration of immature dendritic cells following the adenovirus vector encoding CD40 ligand elicits significant regression of established myeloma

ER-Targeting PDT Converts Tumors into In Situ Therapeutic Tumor Vaccines

A therapeutic tumor vaccine is a promising approach to cancer treatment. One of its strategies is to treat patient-derived tumor cells in vitro and then administer them in vivo to induce an adaptive immune response and achieve cancer treatment. Here, we want to explore the possibility of converting cancer tissue into a therapeutic tumor vaccine through induced immunogenic cell death (ICD) in situ. We loaded indocyanine green (ICG) into liposomes (ICG-Lipo) and modified it with the pardaxin peptide to realize an endoplasmic reticulum (ER)-targeting function (Par-ICG-Lipo). A microfluidic technique was developed for loading ICG, a water-soluble molecule, into liposomes with a high encapsulation efficiency (greater than 90%). Under near-infrared (NIR) irradiation, ER-targeting photodynamic therapy (PDT) induced by Par-ICG-Lipo could promote the release of danger-signaling molecules (DAMPs) and tumor antigens (TAAs) in vivo, which significantly enhanced the immunogenicity in vivo and thus stimulates a strong antitumor immune response. This process would be further amplified by adopting dendritic cells. In general, our strategy transformed in situ tumor cells into therapeutic vaccines by ER-targeting PDT, which could provide a clinically applicable and effective approach for cancer treatment.

Programming CAR T cells to enhance anti-tumor efficacy through remodeling of the immune system

Chimeric antigen receptor (CAR) T cells have been indicated effective in treating B cell acute lymphoblastic leukemia and non-Hodgkin lymphoma and have shown encouraging results in preclinical and clinical studies. However, CAR T cells have achieved minimal success against solid malignancies because of the additional obstacles of their insufficient migration into tumors and poor amplification and persistence, in addition to antigen-negative relapse and an immunosuppressive microenvironment. Various preclinical studies are exploring strategies to overcome the above challenges. Mobilization of endogenous immune cells is also necessary for CAR T cells to obtain their optimal therapeutic effect given the importance of the innate immune responses in the elimination of malignant tumors. In this review, we focus on the recent advances in the engineering of CAR T cell therapies to restore the immune response in solid malignancies, especially with CAR T cells acting as cellular carriers to deliver immunomodulators to tumors to mobilize the endogenous immune response. We also explored the sensitizing effects of conventional treatment approaches, such as chemotherapy and radiotherapy, on CAR T cell therapy. Finally, we discuss the combination of CAR T cells with biomaterials or oncolytic viruses to enhance the anti-tumor outcomes of CAR T cell therapies in solid tumors.

In situ antitumor vaccination: Targeting the tumor microenvironment

Tumor microenvironment is known to play important roles in tumor progression. Many therapies, targeting the tumor microenvironment, are designed and applied in the clinic. One of these approaches is in situ antitumor therapy. This way, bacteria, antibodies, plasmid DNA, viruses, and cells are intratumorally delivered into the tumor site as "in-situ antitumor vaccine," which seeks to enhance immunogenicity and generate systemic T cell responses. In addition, this intratumoral therapy can alter the tumor microenvironment from immunosuppressive to immunostimulatory while limiting the risk of systemic exposure and associated toxicity. Contemporarily, promising preclinical results and some initial success in clinical trials have been obtained after intratumoral therapy.

A novel agent SL-401 induces anti-myeloma activity by targeting plasmacytoid dendritic cells, osteoclastogenesis and cancer stem-like cells

Novel therapies for multiple myeloma (MM) can target mechanism(s) in the host-MM bone marrow (BM) microenvironment mediating MM progression and chemoresistance. Our studies showed increased numbers of tumor-promoting, immunosuppressive and drug-resistant plasmacytoid dendritic cells (pDCs) in the MM BM microenvironment. pDC-MM cell interactions upregulate interleukin-3 (IL-3), which stimulates both pDC survival and MM cell growth. Since IL-3 R is highly expressed on pDCs in the MM BM milieu, we here targeted pDCs using a novel IL-3 R-targeted therapeutic SL-401. In both in vitro and in vivo models of MM in its BM milieu, SL-401 decreases viability of pDCs, blocks pDC-induced MM cell growth, and synergistically enhances anti-MM activity of bortezomib and pomalidomide. Besides promoting pDC survival and MM cell growth, IL-3 also mediates progression of osteolytic bone disease in MM. Osteoclast (OCL) progenitor cells express IL-3 R, and we show that SL-401 abrogates monocyte-derived OCL formation and bone resorption. Finally, we show that SL-401 also decreases the viability of IL-3 R-expressing cancer stem-like cells in MM. Overall, our study provides the preclinical basis for clinical trials of SL-401 to block pDC-induced MM cell growth, inhibit osteoclastogenesis and target MM stem-like cell subpopulations to improve patient outcome in MM.

Role of CD154 in cancer pathogenesis and immunotherapy

Many factors and molecules have been investigated as potential players in the pathogenesis or immunosurveillance of cancer. Among these, CD154 has been recognized as a co-stimulatory molecule with high potential for treating cancer, in addition to its contribution in the development of the disease. CD154 was initially described for its pivotal role in T cell-dependent humoral responses via an interaction with its classical receptor, CD40. Subsequent studies showed that CD154 is also implicated in cell-mediated immunity and inflammation via an interaction with CD40 alone or in combination with newly identified receptors, members of the integrin family, leading to the development of chronic inflammatory and autoimmune diseases. In the current article, we present an overview of the role of CD154 as a potential etiological factor in tumors inducing proliferation of malignant cells, their rescue from apoptosis and their invasiveness. In addition, this review describes the immuno-regulatory functions of CD154 against cancer reflected by its stimulation of antigen-presenting cells and the subsequent activation of effector cells, its enhancement of malignant cells' immunogenicity, its modulation of immune settings around tumors, and its initiation of proliferation inhibiting effects in malignant cells. In vitro as well as in vivo studies are outlined and a particular attention is given to clinical studies and progress reached at this point. Findings reviewed herein will improve our knowledge of the role of the CD154 system in cancers from causative to immunotherapeutic functions, paving the way for the identification of new targets for prevention and/or treatment of malignant disorders.

Targeting the tumor microenvironment to enhance antitumor immune responses

The identification of tumor-specific antigens and the immune responses directed against them has instigated the development of therapies to enhance antitumor immune responses. Most of these cancer immunotherapies are administered systemically rather than directly to tumors. Nonetheless, numerous studies have demonstrated that intratumoral therapy is an attractive approach, both for immunization and immunomodulation purposes. Injection, recruitment and/or activation of antigen-presenting cells in the tumor nest have been extensively studied as strategies to cross-prime immune responses. Moreover, delivery of stimulatory cytokines, blockade of inhibitory cytokines and immune checkpoint blockade have been explored to restore immunological fitness at the tumor site. These tumor-targeted therapies have the potential to induce systemic immunity without the toxicity that is often associated with systemic treatments. We review the most promising intratumoral immunotherapies, how these affect systemic antitumor immunity such that disseminated tumor cells are eliminated, and which approaches have been proven successful in animal models and patients.

Construction of the HBV S-ecdCD40L fusion gene and effects of HBV S-ecdCD40L modification on function of dendritic cells

We examined the effect of dendritic cells engineered to express an HBV S antigen CD40L fusion gene (HBV S-ecdCD40L). The DNA of HBV S gene and the cDNA of the extracellular domain of human CD40 ligand were linked by cloning. Peripheral blood mononuclear cells (PBMC) from healthy adults were incubated and induced into dendritic cells (DC) in presence of granulocyte/macrophage colony-stimulating factor (GM-CSF) and interleukin-4(IL-4). The DCs were transfected the novel construct, and the impact of the expressed clone assessed. We find that, compared with control groups, modification of DCs with HBV S-ecdCD40L fusion gene resulted in the activation of DCs with upregulated expression of immunologically important cell surface molecules (CD80, CD86 and HLA-DR) and proinflammatory cytokines (IL-12). The DCs modified with HBV S-ecdCD40L are able to stimulate enhanced allogeneic T-cell proliferation in vitro. Thus, the fusion gene HBV S-ecdCD40L can promote DC's activation and enhance its function and may prove to be the foundation for a new type of hepatitis B vaccine.

Adenoviral vaccination combined with CD40 stimulation and CTLA-4 blockage can lead to complete tumor regression in a murine melanoma model

Therapeutic vaccination with replication deficient adenovirus expressing a viral antigen linked to invariant chain was recently found to markedly delay the growth of B16.F10 melanomas expressing the same antigen; however, complete regression of the tumors was never observed. Here we show that the delay in tumor growth can be converted to complete regression and long-term survival in 30-40% of the mice by a booster vaccination plus combinational treatment with agonistic anti-CD40 monoclonal antibodies (mAb) and anti-CTLA-4 mAb. Regarding the mechanism underlying the improved clinical effect, analysis of the tumor-specific response revealed a significantly prolonged tumor-specific CD8 T cell response in spleens of the mice receiving the combinational treatment compared with mice receiving either treatment individually. Matching this, CD8 T cell depletion completely prevented tumor control. These results indicate that even with a strong tumor vaccine candidate, combinatorial treatment may be required to obtain clinically relevant results.

CD40 ligand induced cytotoxicity in carcinoma cells is enhanced by inhibition of metalloproteinase cleavage and delivery via a conditionally-replicating adenovirus

Background

CD40 and its ligand (CD40L) play a critical role in co-ordinating immune responses. CD40 is also expressed in lymphoid malignancies and a number of carcinomas. In carcinoma cells the physiological outcome of CD40 ligation depends on the level of receptor engagement with low levels promoting cell survival and high levels inducing cell death. The most profound induction of cell death in carcinoma cells is induced by membrane-bound rather than recombinant soluble CD40L, but like other TNF family ligands, it is cleaved from the membrane by matrix metalloproteinases.

Results

We have generated a replication-deficient adenovirus expressing a mutant CD40L that is resistant to metalloproteinase cleavage such that ligand expression is retained at the cell membrane. Here we show that the mutated, cleavage-resistant form of CD40L is a more potent inducer of apoptosis than wild-type ligand in CD40-positive carcinoma cell lines. Since transgene expression via replication-deficient adenovirus vectors in vivo is low, we have also engineered a conditionally replicating E1A-CR2 deleted adenovirus to express mutant CD40L, resulting in significant amplification of ligand expression and consequent enhancement of its therapeutic effect.

Conclusions

Combined with numerous studies demonstrating its immunotherapeutic potential, these data provide a strong rationale for the exploitation of the CD40-CD40L pathway for the treatment of solid tumours.

CD40 ligation converts TGF-beta-secreting tolerogenic CD4-8- dendritic cells into IL-12-secreting immunogenic ones

CD40L, the ligand for CD40 on dendritic cells (DCs), plays an important role in maturation and activation of DCs leading to induction of immune responses. Our previous studies showed that the mouse splenic CD4(-)8(-) DCs are tolerogenic and capable of stimulating suppressive type 1 CD4(+) regulatory T (Tr1) cell responses via TGF-beta secretion. In this study, we investigated whether CD40 ligation is able to convert tolerogenic CD4(-)8(-) DCs into immunogenic ones by in vitro treatment of DCs with anti-CD40 antibody. Our data showed that in vitro CD40 ligation with anti-CD40 antibody converted TGF-beta-secreting tolerogenic CD4(-)8(-) DCs into IL-12-secreting immunogenic ones capable of stimulating type 1 CD4(+) helper T (Th1) and CD8(+) cytotoxic T lymphocyte (CTL) responses leading to induction of antitumor immunity. In addition, in vivo CD40 ligation by intratumoral injection of adenoviral vector AdVCD40L expressing CD40 ligand also induced tumor growth inhibition and regression of established P815 tumors with infiltration of tolerogenic CD4(-)8(-) DCs. Therefore, our data provide new information for and may thus have useful impacts in CD40 ligation-based immunotherapy of cancer.

Transgene expression of alpha tumor necrosis factor with mutations D142N and A144R under control of human telomerase reverse transcriptase promoter eradicates well-established tumors and induces long-term antitumor immunity

Recombinant adenoviral vectors (AdVTNF-alpha) expressing alpha tumor necrosis factor (TNF-alpha) under control of cytomegalovirus (CMV) promoter have been used in cancer gene therapy. To reduce its cytotoxicity, we constructed a recombinant AdV(TERT)mTNF-alpha expressing a mutant TNF-alpha (mTNF-alpha) with mutations at D142N and A144R under control of human telomerase reverse transcriptase (hTERT) promoter for treatment of well-established ovalbumin (OVA)-expressing murine B16 melanoma (BL6-10(OVA)) (6 mm in diameter). We demonstrated that the mTNF-alpha with mutations at D142N and A144R has less in vitro cytotoxicity, but maintains its functional effect in the stimulation of T-cell proliferation. The in vitro and in vivo transgene expressions under control of hTERT promoter are highly restricted in tumor cells compared with those under the control of the CMV promoter. AdV(TERT)mTNF-alpha gene therapy by intratumoral injection of AdV(TERT)mTNF-alpha vector (2 x 10(9) PFU) expressing the mutant mTNF-alpha under control of hTERT promoter reduces its in vivo toxicity, eradicates well-established BL6-10(OVA) tumors in 4/10 tumor-bearing mice, and induces OVA-specific CD8(+) T-cell-mediated long-term antitumor immunity. Therefore, AdV(TERT)mTNF-alpha gene therapy may be very useful in the immunotherapy of cancer.

Adenovirus-mediated CD40L gene therapy induced both humoral and cellular immunity against rat model of hepatocellular carcinoma

Adenoviral-vector expressing CD40L (AxCAmCD40L)-mediated gene therapy was studied for treatment of hepatocellular carcinoma (HCC) using CD40 ligand (CD40L) complementary DNA in rats. The particular focus was whether humoral immunity took part in antitumor effect. When tumor cells transduced by AxCAmCD40L were implanted into the subcutaneous tissues of syngeneic rats, the tumor growth was suppressed. Intratumoral injection of AxCAmCD40L to pre-existing tumor in rats also led to significant reduction of tumor size. When tumor cells were re-implanted to prevention model rats and treatment model rats, no tumor growth was observed. Many studies to date have reported that cellular immunity induces antitumor immunity. However, the present study demonstrated that not only cellular immunity but also humoral immunity plays an essential role in a HCC model. These observations suggested that CD40L-mediated immune gene therapy for HCC was very effective treatment by activation of both cellular and humoral immune system.

Vaccination of fiber-modified adenovirus-transfected dendritic cells to express HER-2/neu stimulates efficient HER-2/neu-specific humoral and CTL responses and reduces breast carcinogenesis in transgenic mice

HER-2/neu transgene-modified dendritic cell (DC)-based vaccines are potent at eliciting HER-2/neu-specific antitumor immunity. In this study, we constructed a recombinant adenovirus (RGD)AdVneu with fiber gene modified by RGD insertion into the viral knob's H1 loop. We transfected DCs with (RGD)AdVneu, and assessed/compared HER-2/neu-specific humoral and cytotoxic T lymphocyte (CTL) responses and antitumor immunity derived from the original AdVneu-transfected DCs (DCneu1) and (RGD)AdVneu-transfected DCs (DCneu2). We demonstrated that DCneu2 displayed increased HER-2/neu expression by 8.3-fold compared to DCneu1. We also demonstrated that DCneu2 vaccination induced stronger HER-2/neu-specific humoral and CTL immune responses than DCneu1 vaccination. DCneu2 vaccination protected all the mice from HER-2/neu-expressing Tg1-1 tumor cell challenge in wild-type FVB/NJ mice, compared to a partial protection in DCneu1-immunized mice. In addition, DCneu2 vaccination also significantly delayed tumor growth than DCneu1 immunization (P<0.05) in Tg FVBneuN mice. Three immunizations of DCneu2 starting at the mouse age of 2 months also significantly delayed breast cancer development in Tg mice compared to DCneu2 vaccine (P<0.05). Importantly, DCneu2 vaccine reduced breast carcinogenesis by 9% in Tg mice with self HER-2/neu tolerance. Therefore, vaccination of fiber-modified adenovirus-transfected DCs to enhance expression of tumor antigens such as HER-2/neu is likely representative of a new direction in DC-based vaccine of breast cancer.

Therapeutic vaccination against murine lymphoma by intratumoral injection of recombinant fowlpox virus encoding CD40 ligand

The interaction between CD40 ligand (CD40L, CD154) and its receptor CD40 on antigen-presenting cells is essential for the initiation of cell-mediated and humoral immune responses. Malignant B cells also express CD40 and respond to CD40L by enhancing expression of costimulatory molecules. In this study, we investigated the therapeutic antitumor effect of intratumoral administration of recombinant fowlpox virus encoding murine CD40L (rF-mCD40L) in a murine B-cell lymphoma model. BALB/c mice with established s.c. and widely metastatic A20 lymphoma tumors were treated with intratumoral injections of rF-mCD40L together with systemic chemotherapy. This combined chemoimmunotherapy resulted in complete tumor regression and long-term survival of the mice. Some tumor cells in the injected sites expressed the CD40L transgene and had increased expression of the CD80 and CD86 costimulatory molecules. The therapeutic effect was dependent on CD8 but not on CD4 T cells. Moreover, there was a requirement that the recombinant CD40L virus be injected directly into the tumor, as opposed to peritumoral or distant sites. Thus, rF-mCD40L injected directly into the tumor microenvironment enhances the immunogenicity of tumor B cells. The results support future plans for intratumoral injection of rF-mCD40L in patients with lymphoma.

Nasal inoculation of an adenovirus vector encoding 11 tandem repeats of Abeta1-6 upregulates IL-10 expression and reduces amyloid load in a Mo/Hu APPswe PS1dE9 mouse model of Alzheimer's disease

BACKGROUND

One of the pathological hallmarks of Alzheimer's disease (AD) is deposits of amyloid beta-peptide (Abeta) in neuritic plaques and cerebral vessels. Immunization of AD mouse models with Abeta reduces Abeta deposits and improves memory and learning deficits. Because recent clinical trials of immunization with Abeta were halted due to brain inflammation that was presumably induced by a T-cell-mediated autoimmune response, vaccination modalities that elicit predominantly humoral immune responses are currently being developed.

METHODS

We have nasally immunized a young AD mouse model with an adenovirus vector encoding 11 tandem repeats of Abeta1-6 fused to the receptor-binding domain (Ia) of Pseudomonas exotoxin A (PEDI), AdPEDI-(Abeta1-6)(11), in order to evaluate the efficacy of the vector in preventing Abeta deposits in the brain. We also have investigated immune responses of mice to AdPEDI-(Abeta1-6)(11).

RESULTS

Nasal immunization of an AD mouse model with AdPEDI-(Abeta1-6)(11) elicited a predominant IgG1 response and reduced Abeta load in the brain. The plasma IL-10 level in the AD mouse model was upregulated after immunization and, upon the stimulation with PEDI-(Abeta1-6)(11), marked IL-10 responses were found in splenic CD4(+) T cells from C57BL/6 mice that had been immunized with AdPEDI-(Abeta1-6)(11).

CONCLUSIONS

These results suggest that the induction of Th2-biased responses with AdPEDI-(Abeta1-6)(11) in mice is mediated in part through the upregulation of IL-10, which inhibits activation of dendritic cells that dictate the induction of Th1 cells.

Combinational adenovirus-mediated gene therapy and dendritic cell vaccine in combating well-established tumors

Recent developments in tumor immunology and biotechnology have made cancer gene therapy and immunotherapy feasible. The current efforts for cancer gene therapy mainly focus on using immunogenes, chemogenes and tumor suppressor genes. Central to all these therapies is the development of efficient vectors for gene therapy. By far, adenovirus (AdV)-mediated gene therapy is one of the most promising approaches, as has confirmed by studies relating to animal tumor models and clinical trials. Dendritic cells (DCs) are highly efficient, specialized antigen-presenting cells, and DC-based tumor vaccines are regarded as having much potential in cancer immunotherapy. Vaccination with DCs pulsed with tumor peptides, lysates, or RNA, or loaded with apoptotic/necrotic tumor cells, or engineered to express certain cytokines or chemokines could induce significant antitumor cytotoxic T lymphocyte (CTL) responses and antitumor immunity. Although both AdV-mediated gene therapy and DC vaccine can both stimulate antitumor immune responses, their therapeutic efficiency has been limited to generation of prophylactic antitumor immunity against re-challenge with the parental tumor cells or to growth inhibition of small tumors. However, this approach has been unsuccessful in combating well-established tumors in animal models. Therefore, a major strategic goal of current cancer immunotherapy has become the development of novel therapeutic strategies that can combat well-established tumors, thus resembling real clinical practice since a good proportion of cancer patients generally present with significant disease. In this paper, we review the recent progress in AdV-mediated cancer gene therapy and DC-based cancer vaccines, and discuss combined immunotherapy including gene therapy and DC vaccines. We underscore the fact that combined therapy may have some advantages in combating well-established tumors vis-a-vis either modality administered as a monotherapy.

Conversion of Tolerogenic CD4¯8¯ Dendritic Cells to Immunogenic Ones Inducing Efficient Antitumor Immunity

Culturing conditions may affect dendritic cell (DC) maturation status and functional effects. We have previously demonstrated that different DC subsets play distinct roles in immune responses. The splenic CD4-8- DC subset that secretes transforming growth factor (TGF)-beta stimulates CD4+ regulatory T type 1 (Tr1) cell responses, and this leads to antitumor immune tolerance. In this study, we investigated the potential effect of culturing conditions, namely: (1) duration of culturing and (2) the dose of antigen ovalbumin (OVA) for DC pulsing, respectively, in the conversion of tolerogenic CD4-8- DC into immunogenic DCs. Our data showed that isolated CD4-8- DCs cultured for an additional 18 hours in medium containing 15-20 ng/mL granulocyte macrophage colony-stimulating factor (GM-CSF) became more mature compared to the freshly isolated CD4-8- DCs. When pulsed with OVA at the relatively high concentration of 1 mg/mL, but not at 0.1 mg/mL, the CD4-8- DCs could be converted into immunogenic CD4-8- DCs, which stimulated CD4+ T-cell differentiation into type 1 helper T (Th1) cells. Vaccination of mice with converted CD4-8- DCs induced strong OVA-specific cytotoxic T-lymphocyte (CTL) responses and protective immunity against OVA-expressing BL6-10OVA B16 melanoma. Taken together, our findings indicate that the conversion of DCs from a tolerogenic to an immunogenic state can be achieved by the elongation of DC culturing time in combination with a high-dose antigen for DC pulsing. Therefore, our results may have a significant impact in designing DC-based antitumor vaccines.

Vaccine strategies to treat lymphoproliferative disorders

Lymphoproliferative disorders, including follicular lymphoma (FL), multiple myeloma (MM) and chronic lymphatic leukaemia (CLL), are slowly progressive malignancies which remain incurable despite advances in therapy. Harnessing the immune system to recognise and destroy tumours is a promising new approach to treating these diseases. Dendritic cells (DC) are unique antigen-presenting cells that play a central role in the initiation and direction of immune responses. DC loaded ex vivo with tumour-associated antigens and administered as a vaccine have already shown promise in early clinical trials for a number of lymphoproliferative disorders, but the need for improvement is widely agreed. Recent advances in the understanding of basic DC biology and lessons from early clinical trials have provided exciting new insights into the generation of anti-tumour immune responses and the design of vaccine strategies. In this review we provide an overview of our current understanding of DC biology and their function in patients with lymphoproliferative disorders. We discuss the current status of clinical trials and new approaches to exploit the antigen presenting capacity of DC to design vaccines of the future.