Intratumoral injection of interferon-gamma gene-modified dendritic cells elicits potent antitumor effects: effective induction of tumor-specific CD8+ CTL response

Intratumoral immunotherapy for melanoma

Selection of suitable tumor-associated antigens is a major challenge in the development of effective cancer vaccines. Intratumoral (i.t.) immunotherapy empowers the immune system to mount T cell responses against tumor-associated antigens which are most immunogenic. To mediate systemic tumor regression, i.t. immunotherapy must generate systemic T cell responses that can target distant metastases beyond the initially treated tumor mass. Now that promising preclinical results and some initial success in clinical trials have been obtained, we here review i.t. immunotherapy-related preclinical and clinical studies, their mechanisms of action and future prospects.

Tumor stroma engraftment of gene-modified mesenchymal stem cells as anti-tumor therapy against ovarian cancer

BACKGROUND AIMS

Many ovarian cancers originate from ovarian surface epithelium, where they develop from cysts intermixed with stroma. The stromal layer is critical to the progression and survival of the neoplasm and consequently is recruited into the tumor microenvironment.

METHODS

Using both syngeneic mouse tumors (ID8-R) and human xenograft (OVCAR3, SKOV3) tumor models, we first confirmed that intraperitoneally injected circulating mesenchymal stem cells (MSCs) could target, preferentially engraft and differentiate into α-smooth muscle actin-positive myofibroblasts, suggesting their role as "reactive stroma" in ovarian carcinoma development and confirming their potential as a targeted delivery vehicle for the intratumoral production of interferon-β (IFN-β). Mice with ovarian carcinomas then received weekly intraperitoneal injections of IFN-β expressing MSCs.

RESULTS

Intraperitoneal injections of IFN-β expressing MSCs resulted in complete eradication of tumors in 70% of treated OVCAR3 mice (P = 0.004) and an increased survival of treated SKOV3 mice compared with controls (P = 0.01). Similar tumor growth control was observed using murine IFN-β delivered by murine MSCs in ID8-R ovarian carcinoma. As a potential mechanism of tumor killing, MSCs produced IFN-β-induced caspase-dependent tumor cell apoptosis.

CONCLUSIONS

Our results demonstrate that ovarian carcinoma engrafts MSCs to participate in myofibrovascular networks and that IFN-β produced by MSCs intratumorally modulates tumor kinetics, resulting in prolonged survival.

Gene transfer of AIMP1 and B7.1 into epitope-loaded, fibroblasts induces tumor-specific CTL immunity, and prolongs the survival period of tumor-bearing mice

T helper type 1 (Th1) cell-mediated immune responses play various roles in cellular immunity, including inducing cytotoxic T lymphocytes (CTLs) and they have been shown to be crucial in cancer immunotherapy. Previously, we found that aminoacyl-tRNA synthetase-interacting multifunctional protein 1 (AIMP1) stimulated antigen-presenting cells to secrete IL-12, leading to enhanced Th1 cell responses. In this study, as a way of enhancing antigen-specific Th1 responses, mouse fibroblasts (H-2(b)) were genetically modified to express an AIMP1 and a costimulatory B7.1 (Fb/AIMP1/B7.1). Fb/AIMP1/B7.1 cells were then loaded with an ovalbumin epitope as a model antigen (Fb/AIMP1/B7.1/OVA), and tested to determine if they induced OVA-specific CTLs in C57BL/6 mice (H-2(b)). Immunization with Fb/AIMP1/B7.1/OVA cells induced strong cytotoxic activities against OVA-expressing EG7 tumor cells, but not against other H-2(b) tumor cells. The levels of the cytotoxic response in the immunized mice with Fb/AIMP1/B7.1/OVA cells were significantly higher than the responses in mice immunized with other cell constructs. CD8(+) T cells were a major cell-type of OVA-specific antitumor immunity induced by Fb/AIMP1/B7.1/OVA cells. Furthermore, treatment with Fb/AIMP1/B7.1/OVA cells significantly prolonged the survival period of EG7 tumor-bearing mice. These results indicate that AIMP1-secreting, epitope-loaded fibroblasts efficiently induce antigen-specific CTL responses in mice.

Anti-angiogenic active immunotherapy: a new approach to cancer treatment

Tumor angiogenesis plays an important role in tumor growth, aggression and metastasis. Many molecules have been demonstrated as positive regulators of angiogenesis, including vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF), epidermal growth factor (EGF), and others. In recent years, significant progress has been made in the research on anti-angiogenic strategies for tumor therapies. In this review, anti-angiogenic active immunotherapies for tumors based on vaccination with xenogeneic homologous molecules and non-xenogeneic homologous molecules are discussed.

Elevated maternal corticosterone during lactation hinders the neonatal adaptive immune response to herpes simplex virus (HSV) infection

The neonate's immune system is relatively immature. For short-term protection against pathogens the neonate is reliant primarily on maternally derived antibodies delivered via the mother's milk. However, neonates soon acquire the ability to generate adaptive immune responses for long-term protection. Products of the nervous and endocrine systems that are elicited by psychological stress are known to modulate a variety of immune responses. Additionally, psychological stressors are well recognized for their ability to increase corticosterone levels. The studies described herein examined the effects of increases in maternally derived corticosterone on the neonatal cell-mediated immune response to, and pathogenicity of, herpes simplex virus (HSV) infection. Water containing corticosterone was made available to nursing mothers for a period of 6 consecutive days beginning on either the day of or 6 days post-delivery. At 12 days of age, neonates were infected with HSV-1 in the rear footpads. These neonates exhibited a decrease in the proliferative ability of splenic-derived cells due to the reduction of IL-2 production and IL-2 receptor alpha subunit (IL-2R alpha) expression by these cells. These neonates also exhibited a decrease in the number and function of popliteal lymph node-resident HSV-1 gB(498-505) peptide-specific CD8(+) T cells as measured by tetramer analysis, CTL lytic activity, expression of CD107a, cytokine production, and proliferation. Additionally, these HSV-infected neonates exhibited increased morbidity and mortality. Together, these studies indicate that exposure of neonates to maternally derived corticosterone via the milk hinders their ability to generate an adaptive cell-mediated immune response to a viral infection and illustrate the potential importance of maternal stress in neonatal resistance to infectious pathogens.

Enhancement of immunologic tumor regression by intratumoral administration of dendritic cells in combination with cryoablative tumor pretreatment and Bacillus Calmette-Guerin cell wall skeleton stimulation

PURPOSE

We developed an effective immunotherapy, which could induce antitumor immune responses against shared and unique tumor antigens expressed in autologous tumors.

EXPERIMENTAL DESIGN

Intratumoral administration of dendritic cells is one of the individualized immunotherapies; however, the antitumor activity is relatively weak. In this study, we attempted to enhance the antitumor efficacy of the i.t. dendritic cell administration by combining dendritic cells stimulated with Bacillus Calmette-Guerin cell wall skeleton (BCG-CWS) additionally with cryoablative pretreatment of tumors and analyzed the therapeutic mechanisms.

RESULTS

These two modifications (cryoablation of tumors and BCG-CWS stimulation of dendritic cells) significantly increases the antitumor effect on both the treated tumor and the untreated tumor, which was distant at the opposite side, in a bilateral s.c. murine CT26 colon cancer model. Further analysis of the augmented antitumor effects revealed that the cryoablative pretreatment enhances the uptake of tumor antigens by the introduced dendritic cells, resulting in the induction of tumor-specific CD8(+) T cells responsible for the in vivo tumor regression of both treated and remote untreated tumors. This novel combination i.t. dendritic cell immunotherapy was effective against well-established large tumors. The antitumor efficacy was further enhanced by depletion of CD4(+)CD25(+)FoxP3(+) regulatory T cells.

CONCLUSIONS

This novel dendritic cell immunotherapy with i.t. administration of BCG-CWS-treated dendritic cells following tumor cryoablation could be used for the therapy of cancer patients with multiple metastases.

IFN-gamma and T-bet expression in human dendritic cells from normal donors and cancer patients is controlled through mechanisms involving ERK-1/2-dependent and IL-12-independent pathways

Dendritic cells (DC) play a major role in priming naive T cells and modulating the immune response. We have previously reported that bryostatin-1, a potent immune modulator with antitumor activity, activates monocytes and lymphocytes to produce cytokines. Studies have shown that tumor-bearing hosts have a Th1/Th2 cytokine pattern that is associated with decreased production of IFN-gamma. We investigated the expression of IFN-gamma in bryostatin-1-treated human DC. Bryostatin-1 induced both IFN-gamma and T-bet mRNA expression in a dose- and time-dependent manner. As little as 1 ng/ml bryostatin-1 induced IFN-gamma and T-bet transcripts within 3 h and protein at 12 h. Treatment of DC with cycloheximide revealed that bryostatin-1-induced T-bet expression requires de novo protein synthesis, but bryostatin-1-induced IFN-gamma expression is independent of protein synthesis. Furthermore, dexamethasone inhibits bryostatin-1-induced IFN-gamma mRNA expression but increases bryostatin-1-induced T-bet mRNA expression. Experiments with ERK-1/2 inhibitors demonstrated that bryostatin-1 induction of IFN- gamma and T-bet was ERK-dependent and IL-12-independent. Similar results were obtained from both normal donors and cancer patients. In summary, our results suggest that bryostatin-1-induced IFN-gamma expression is T-bet independent. They also suggest for the first time that IFN- gamma and T-bet can be induced in human DC through an ERK-dependent pathway. Bryostatin-1-induced IFN- gamma may play a crucial role in the initiation of the immune response, before specific recognition by T cells that could be beneficial in the treatment of cancer.