Tumor cell lysate-pulsed dendritic cells induce a T cell response against colon cancer in vitro and in vivo

RAD001-mediated mTOR targeting in human monocyte-derived dendritic cells shifts them toward an immunogenic phenotype

Dendritic cells (DCs) are essential for promoting T lymphocyte responses since they are specialist antigen-presenting cells. In order to maintain tolerance or initiate immune responses, DCs must be activated in a balanced and regulated manner via diverse signaling pathways. By using a variety of pharmacological components, we can interfere with their different signaling pathways such as the mammalian target of rapamycin (mTOR) to appropriately modulate DC activity. In the current study, we administered RAD001 to DCs to examine the impact of mTOR inhibition on both the maturation stage and the expression of inflammatory and anti-inflammatory molecules in DCs. Pure monocytes were cultivated and stimulated with GM-CSF and IL-4 to generate immature DCs, which were then treated with RAD001. The phenotype of the DCs was determined by labeling surface markers and analyzing them using flow cytometry. Afterward, real-time PCR was carried out to evaluate the expression of inflammatory and anti-inflammatory genes. The administration of RAD001 to DCs led to a significant upregulation in the gene expression of inflammatory molecules such as IL-12, IL-1β, tumor necrosis factor (TNF)-α, and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-KB). Conversely, RAD001 treatment resulted in a decrease in the gene expression of anti-inflammatory factors IL-10 and indoleamine 2,3-dioxygenase (IDO). However, the expression of differentiation and antigen presentation-related markers CD11c and human leukocyte antigens (HLA)-DR in RAD001-treated DCs was lower and higher compared to the control group that did not receive the treatment, respectively. Taken together, our findings indicated that RAD001 treatment of DCs can be a promising therapeutic approach for the generation of immunogenic DCs in order to barricade tumor growth. However, there is a need for further investigation to evaluate the impacts of mTOR inhibition by RAD001 in DCs on cellular immune responses in vitro and in vivo.

Boosting immunotherapy efficacy: Empowering the Potency of Dendritic cells loaded with breast cancer lysates through CTLA-4 suppression

Anticancer immunotherapies with a dendritic Cell (DC) basis are becoming more popular. However, it has been suggested that the tumor's immunosuppressive mechanisms, such as inhibitory immunological checkpoint molecules, reduce the effectiveness of anticancer immunogenicity mediated by DC. Thus, overcoming immune checkpoints and inducing effective antigen-specific T-cell responses uniquely produced with malignant cells represent the key challenges. Among the inhibitory immune checkpoints, DCs' ability to mature and present antigens is decreased by CTLA-4 expression. Consequently, we hypothesized that by expressing CTLA-4 cells on DCs, the T cells' activation against tumor antigens would be suppressed when confronted with these antigens presented by DCs. In this research, by loading cell lysate of breast cancer (BC) on DCs and the other hand by inhibiting the induction of CTLA-4 using small interfering RNA (siRNA), we assessed the functional activities and phenotypes of DCs, and also the responses associated with T-cells following co-culture DC/T cell. Our research has shown that the suppression of CTLA-4 enhanced the stimulating capabilities of DCs. Additionally, CTLA-4-suppressed BC cell lysate-loaded DCs produced more IL-4 and IFN-ϒ and increased T cell induction in contrast to DCs without CTLA-4 suppression. Together, our data point to CTLA-4-suppressed DCs loaded with BC cell lysate as a potentially effective treatment method. However, further research is required before employing this method in therapeutic contexts.

Boron Derivatives Inhibit the Proliferation of Breast Cancer Cells and Affect Tumor-Specific T Cell Activity In Vitro by Distinct Mechanisms

Breast cancer is the most frequently diagnosed cancer among women worldwide. Despite the initial clinical response obtained with the widely used conventional chemotherapy, an improved prognosis for breast cancer patients has been missing in the clinic because of the high toxicity to normal cells, induction of drug resistance, and the potential immunosuppressive effects of these agents. Therefore, we aimed to investigate the potential anti-carcinogenic effect of some boron derivatives (sodium pentaborate pentahydrate (SPP) and sodium perborate tetrahydrate (SPT)), which showed a promising effect on some types of cancers in the literature, on breast cancer cell lines, as well as immuno-oncological side effects on tumor-specific T cell activity. These findings suggest that both SPP and SPT suppressed proliferation and induced apoptosis in MCF7 and MDA-MB-231 cancer cell lines through downregulation of the monopolar spindle-one-binder (MOB1) protein. On the other hand, these molecules increased the expression of PD-L1 protein through their effect on the phosphorylation level of Yes-associated protein (Phospho-YAP (Ser127). In addition, they reduced the concentrations of pro-inflammatory cytokines such as IFN-γ and cytolytic effector cytokines such as sFasL, perforin, granzyme A, Granzyme B, and granulysin and increased the expression of PD-1 surface protein in activated T cells. In conclusion, SPP, SPT, and their combination could have growth inhibitory (antiproliferative) effects and could be a potential treatment for breast cancer. However, their stimulatory effects on the PD-1/PD-L1 signaling pathway and their effects on cytokines could ultimately account for the observed repression of the charging of specifically activated effector T cells against breast cancer cells.

CTLA-4 silencing in dendritic cells loaded with colorectal cancer cell lysate improves autologous T cell responses in vitro

Dendritic cell (DC)-based immunotherapy has increased interest among anti-cancer immunotherapies. Nevertheless, the immunosuppressive mechanisms in the tumor milieu, e.g., inhibitory immune checkpoint molecules, have been implicated in diminishing the efficacy of DC-mediated anti-tumoral immune responses. Therefore, the main challenge is to overcome inhibitory immune checkpoint molecules and provoke efficient T-cell responses to antigens specifically expressed by cancerous cells. Among the inhibitory immune checkpoints, cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) expression on DCs diminishes their maturation and antigen presentation capability. Accordingly, we hypothesized that the expression of CTLA-4 on DCs inhibits the T cell-mediated anti-tumoral responses generated following the presentation of tumor antigens by DCs to T lymphocytes. In this study, we loaded colorectal cancer (CRC) cell lysate on DCs and inhibited the expression of CTLA-4 by small interfering RNA (siRNA) in them to investigate the DCs’ functional and phenotypical features, and T-cell mediated responses following DC/T cell co-culture. Our results demonstrated that blockade of CTLA-4 could promote stimulatory properties of DCs. In addition, CTLA-4 silenced CRC cell lysate-loaded DCs compared to the DCs without CTLA-4 silencing resulted in augmented T cell proliferation and cytokine production, i.e., IFN-γ and IL-4. Taken together, our findings suggest CTLA-4 silenced CRC cell lysate-loaded DCs as a promising therapeutic approach however further studies are needed before this strategy can be used in clinical practice.

Target Reprogramming Lysosomes of CD8+ T Cells by a Mineralized Metal-Organic Framework for Cancer Immunotherapy

T cell immunotherapy holds significant challenges in solid tumors, mainly due to the T cells' low activation and the decreased synthesis-release of therapeutic proteins, including perforin and granzyme B, which are present in lysosomes. In this study, a lysosome-targeting nanoparticle (LYS-NP) is developed by way of a mineralized metal-organic framework (MOF) coupled with a lysosome-targeting aptamer (CD63-aptamer) to enhance the antitumor effect of T cells. The MOF synthesized from Zn2+ and dimethylimidazole has good protein encapsulation and acid sensitivity, and is thus an ideal lysosomal delivery vector. Calcium carbonate (CaCO3 ) is used to induce MOF mineralization, improve the composite material's stability in encapsulating therapeutic protein, and provide calcium ions with synergistic effects. Before mineralization, perforin and granzyme B-T cell-needed therapeutic proteins for tumors-are preloaded with the MOF. Moreover, T cells are pretreated with processed tumor-specific antigens to activate or produce memory before reprogramming the lysosomes, facilitating the T cell receptor (TCR) for release of the therapeutic proteins. Using T cells recombined by LYS-NPs, a significant enhancement of breast cancer control is confirmed.

Targeting stemness of cancer stem cells to fight colorectal cancers

Cancer initiating/ stem cells (CSCs) undergo self-renewal and differentiation that contributes to tumor initiation, recurrence and metastasis in colorectal cancer (CRC). Targeting of colorectal cancer stem cells (CCSCs) holds significant promise in eradicating cancer cells and ultimately curing patients with cancer. In this review, we will introduce the current progress of CCSC studies, including the specific surface markers of CCSCs, the intrinsic signaling pathways that regulate the stemness and differentiation characteristics of CCSCs, and the tumor organoid model for CCSC research. We will focus on how these studies will lead to the progress in targeting specific surface markers or signaling pathways on CCSCs by monoclonal antibodies, or by natural or synthetic compounds, or by immunotherapy. As CSCs are highly heterogeneous and plastic, we suggest that combinatory approaches that target the stemness network may represent an important strategy for eradicating cancers.

Role of the Cyclooxygenase Pathway in the Association of Obstructive Sleep Apnea and Cancer

The objective of this review is to examine the findings that link obstructive sleep apnea (OSA) with cancer and the role played by the cyclooxygenase (COX) pathway in this association. Epidemiological studies in humans suggest a link between OSA and increased cancer incidence and mortality. Studies carried out in animal models have shown that intermittent hypoxia (IH) induces changes in several signaling pathways involved in the regulation of host immunological surveillance that results in tumor establishment and invasion. IH induces the expression of cyclooxygenase 2 (COX-2) that results in an increased synthesis of prostaglandin E2 (PGE2). PGE2 modulates the function of multiple cells involved in immune responses including T lymphocytes, NK cells, dendritic cells, macrophages, and myeloid-derived suppressor cells. In a mouse model blockage of COX-2/PGE2 abrogated the pro-oncogenic effects of IH. Despite the fact that aspirin inhibits PGE2 production and prevents the development of cancer, none of the epidemiological studies that investigated the association of OSA and cancer included aspirin use in the analysis. Studies are needed to investigate the regulation of the COX-2/PGE2 pathway and PGE2 production in patients with OSA, to better define the role of this axis in the physiopathology of OSA and the potential role of aspirin in preventing the development of cancer.

The surface dominant antigen MUC1 is required for colorectal cancer stem cell vaccine to exert anti-tumor efficacy

Colorectal cancer (CRC), initiated and maintained by colorectal cancer stem cells (CCSCs), ranks the third most common cancers and has drawn wide attentions worldwide. Therefore, targeting clearance of CCSCs has become an important strategy of CRC immunotherapy. Mucin1 (MUC1) is a tumor-associated cell surface antigen of CRC, but its role in CCSC vaccine remains unclear. In the study, we demonstrated that MUC1 may be a dominant antigen to exert antitumor immunity in CCSC vaccine. First, CCSCs were enriched from CT26 cell line via a serum-free sphere formation approach, and were identified by detecting expression of CD133, ALDH, and ALCAM. Then, the isolated CCSCs were frozen for 30 min and thawed for 30 min to prepare the cell lysate. The specific anti-MUC1 antibody was added to the cell lysate to neutralize the dominant antigen MUC1. Finally, mice were subcutaneously immunized with the cell lysate, followed by a challenge with CT26 cells at one week after final vaccination. Attractively, CCSC vaccine significantly activated the NK cells, T cells, and B cells, resulting in inhibiting the tumor growth via a target killing of CCSCs as evidenced by a decrease of CD133⁺cells in tumor compared to CCSC vaccine with specific anti-MUC1 antibody. In addition, CCSC vaccine reduced expression of inflammatory factors in vaccinated mice. As expected, neutralizing antibody against MUC1 significantly impaired the antitumor efficacy of CCSC vaccine. Overall, CCSC vaccine could serve as a potent vaccine for CRC immunotherapy. The surface dominant antigen MUC1 may play a key role in regulating immunogenicity of CCSCs.

Cytolytic Activity of Effector T-lymphocytes Against Hepatocellular Carcinoma is Improved by Dendritic Cells Pulsed with Pooled Tumor Antigens

Cellular immunotherapy is a promising new therapeutic approach for hepatocellular carcinoma (HCC), which has a high recurrence rate, irrespective of the treatment administered. In this study, we attempted to improve the cytolytic activity of effector T-lymphocytes against HCC. T-lymphocytes were activated by monocyte-derived dendritic cells (DCs) pulsed with cell lysate or RNA prepared from HCC cell lines. Monocytes were activated for differentiation into DCs by treatment with the IL4 and GM-CSF. DCs were pulsed with cell lysate or RNA prepared from a single cell line or combinations of two or three HCC cell lines, and then co-cultured with autologous T-lymphocytes with the intent of creating specific cytotoxicity. We discovered that DCs pulsed with total RNA effectuated greater T-lymphocyte function than DCs pulsed with total cell lysate, as evidenced by greater cytolytic activities against HCC target cells. The percentage of Huh7, HepG2, and SNU449 cell apoptosis at effector:target ratio of 10:1 was 42.6 ± 4.5% (p = 0.01), 33.6 ± 3.1% (p = 0.007), and 21.4 ± 1.4% (p < 0.001), respectively. DCs pulsed with pools of antigens prepared from three cell lines improved the cytolytic function of effector T-lymphocytes by approximately two-fold (p < 0.001), which suggests that this approach be further developed and applied for adoptive transfer treatment of HCC.

Gut Microbiota Influences Experimental Outcomes in Mouse Models of Colorectal Cancer

Colorectal cancer (CRC) is a leading cause of cancer-related deaths worldwide. Mouse models are a valuable resource for use throughout the development and testing of new therapeutic strategies for CRC. Tumorigenesis and response to therapy in humans and mouse models alike are influenced by the microbial communities that colonize the gut. Differences in the composition of the gut microbiota can confound experimental findings and reduce the replicability and translatability of the resulting data. Despite this, the contribution of resident microbiota to preclinical tumor models is often underappreciated. This review does the following: (1) summarizes evidence that the gut microbiota influence CRC disease phenotypes; (2) outlines factors that can influence the composition of the gut microbiota; and (3) provides strategies that can be incorporated into the experimental design, to account for the influence of the microbiota on intestinal phenotypes in mouse models of CRC. Through careful experimental design and documentation, mouse models can continue to rapidly advance efforts to prevent and treat colon cancer.

Dendritic cells loaded with CD44+ CT-26 colon cell lysate evoke potent antitumor immune responses

Increasing evidence supports the concept that cancer stem cells (CSCs) are responsible for cancer progression and metastasis, therapy resistance and relapse. In addition to conventional therapies for colon cancer, the development of immunotherapies targeting cancer stem cells appears to be a promising strategy to suppress tumor recurrence and metastasis. In the present study, dendritic cells (DCs) were pulsed with whole-tumor cell lysates or total RNA of CD44⁺ colon cancer stem cells (CCSCs) isolated from mouse colon adenocarcinoma CT-26 cell cultures and investigated for their antitumor immunity against CCSCs in vivo and in vitro. In a model of colon adenocarcinoma using BALB/c mice, a sequential reduction in tumor volume and weight was associated with an extended survival in tumor-bearing mice vaccinated with DCs pulsed with RNA or CCSC lysate. In addition, a lactate dehydrogenase assay indicated that cytotoxic T-cells derived from the treated mice exhibited strong cytotoxic activity. Additionally, an enzyme-linked immunosorbent assay revealed that the cytotoxic T-cells of the treated mice released higher levels of interferon-γ against CCSCs compared with those of the control group. In all experiments, the antitumor efficacy of the lysate-pulsed DC-treated and RNA-pulsed DC-treated groups were significantly higher compared with that of the DC-treated and control groups. The results of the present study indicated the potential use of DCs pulsed with cancer stem cell lysates as a potent therapeutic antigen to target CSCs in colon cancer. Additionally, the results provided a rationale for using lysate-pulsed DCs in vivo to eliminate residual tumor deposits in post-operative patients.

Honokiol-enhanced cytotoxic T lymphocyte activity against cholangiocarcinoma cells mediated by dendritic cells pulsed with damage-associated molecular patterns

BACKGROUND

Cholangiocarcinoma or biliary tract cancer has a high mortality rate resulting from late presentation and ineffective treatment strategy. Since immunotherapy by dendritic cells (DC) may be beneficial for cholangiocarcinoma treatment but their efficacy against cholangiocarcinoma was low. We suggest how such anti-tumor activity can be increased using cell lysates derived from an honokiol-treated cholangiocarcinoma cell line (KKU-213L5).

AIM

To increase antitumour activity of DCs pulsed with cell lysates derived from honokiol-treated cholangiocarcinoma cell line (KKU-213L5).

METHODS

The effect of honokiol, a phenolic compound isolated from Magnolia officinalis, on choangiocarcinoma cells was investigated in terms of the cytotoxicity and the expression of damage-associated molecular patterns (DAMPs). DCs were loaded with tumour cell lysates derived from honokiol-treated cholangiocarcinoma cells their efficacy including induction of T lymphocyte proliferation, proinflammatory cytokine production and cytotoxicity effect on target cholangiocarcinoma cells were evaluated.

RESULTS

Honokiol can effectively activate cholangiocarcinoma apoptosis and increase the release of damage-associated molecular patterns. DCs loaded with cell lysates derived from honokiol-treated tumour cells enhanced priming and stimulated T lymphocyte proliferation and type I cytokine production. T lymphocytes stimulated with DCs pulsed with cell lysates of honokiol-treated tumour cells significantly increased specific killing of human cholangiocarcinoma cells compared to those associated with DCs pulsed with cell lysates of untreated cholangiocarcinoma cells.

CONCLUSION

The present findings suggested that honokiol was able to enhance the immunogenicity of cholangiocarcinoma cells associated with increased effectiveness of DC-based vaccine formulation. Treatment of tumour cells with honokiol offers a promising approach as an ex vivo DC-based anticancer vaccine.

Review on the immunotherapy strategies against metastatic colorectal carcinoma

Colorectal cancer (CRC) is one of the most common malignancies throughout the world and the leading cause of cancer-related mortality in Western countries. Recent progress in CRC treatment options, such as surgery, chemotherapy, radiotherapy and target therapy, has improved the prognosis, but advanced disease with recurrence or distant metastasis is usually incurable and has an unfavorable prognosis. The introduction of immunotherapy-associated strategies, both active and passive, to the treatment of CRC aims to overcome the limits of classical treatments. We review the state of the art for CRC with respect to different immunotherapeutic approaches, such as the use of cancer vaccines and/or adoptive cellular therapy, their most current advances and limitations and perspectives for further improvements.

Targeting breast cancer stem cells by dendritic cell vaccination in humanized mice with breast tumor: preliminary results

Background

Breast cancer (BC) is one of the leading cancers in women. Recent progress has enabled BC to be cured with high efficiency. However, late detection or metastatic disease often renders the disease untreatable. Additionally, relapse is the main cause of death in BC patients. Breast cancer stem cells (BCSCs) are considered to cause the development of BC and are thought to be responsible for metastasis and relapse. This study aimed to target BCSCs using dendritic cells (DCs) to treat tumor-bearing humanized mice models.

Materials and methods

NOD/SCID mice were used to produce the humanized mice by transplantation of human hematopoietic stem cells. Human BCSCs were injected into the mammary fat pad to produce BC humanized mice. Both hematopoietic stem cells and DCs were isolated from the human umbilical cord blood, and immature DCs were produced from cultured mononuclear cells. DCs were matured by BCSC-derived antigen incubation for 48 hours. Mature DCs were vaccinated to BC humanized mice with a dose of 10⁶ cells/mice, and the survival percentage was monitored in both treated and untreated groups.

Results

The results showed that DC vaccination could target BCSCs and reduce the tumor size and prolong survival.

Conclusion

These results suggested that targeting BCSCs with DCs is a promising therapy for BC.

Designing effective vaccines for colorectal cancer

Achieving long-term control of colorectal cancers with therapeutic vaccines that generate potent anti-tumor T cell and antibody responses has been a goal for more than two decades. To date, clinical trials of these vaccines have demonstrated induction of immune responses, but clinical benefit has been limited. Improved vector delivery systems with enhanced immunostimulatory properties, decreased immunogenicity against vector and improved antigen presentation are some of the key features of modern tumor vaccines. Furthermore, an improved understanding of the various immunosuppressive factors in the tumor microenvironment and regional lymph nodes, coupled with a burgeoning ability to impair inhibitory immune synapses, highlights a growing opportunity to induce beneficial antigen-specific responses against tumor. The combination of improved antigenic delivery systems, coupled with therapeutic immune activation, represents state-of-the-art colorectal vaccine design concepts with the goal of augmenting immune responses against tumor and improving clinical outcomes.

Generation of tumor-specific cytotoxic T-lymphocytes from the peripheral blood of colorectal cancer patients for adoptive T-cell transfer

This study designs a strategy for an adoptive cellular therapy (ACT) protocol based on the ex-vivo selection of autologous peripheral blood-derived CD8-enriched T-cells, stimulated with dendritic cells (DCs) that had been pulsed with apoptotic tumor cells to generate cytotoxic T lymphocytes (CTLs) with anti-tumor activity. Seventy-eight colorectal cancer (CRC) patients were enrolled in this study. Tumor tissues and peripheral blood (PB) were obtained at surgery. Tissues were mechanically dissociated and cultured to obtain a primary tumor cell line from each patient. DCs were derived from peripheral blood mononuclear cells (PBMCs) using magnetic positive selection of CD14+ monocytes. Anti-tumor CTLs were elicited in co-/micro-cultures using DCs as antigen-presenting cells, autologous apoptotic tumor cells as a source of antigens, and CD8+ T lymphocytes as effectors. Interferon-γ (IFN-γ) secretion was assessed by ELISpot assays to evaluate the activation of the CTLs against the autologous tumor cells. Primary tumor cell lines were obtained from 20 of 78 patients (25.6%). DCs were generated from 26 patients, and of them, corresponding tumor cell lines were derived from six patients. ELISpot results showed that significant IFN-γ secretion was detected after different numbers of stimulations for two patients, whereas weak secretion was observed for three patients. Despite difficulties due to contamination of several primary tumor cell lines with gut intestinal flora, the results suggest that the generation of tumor-specific CTLs is feasible from patients with CRC, and could be useful for supporting an ACT approach in CRC.

Affinity proteomics led identification of vimentin as a potential biomarker in colon cancers: insights from serological screening and computational modelling

Proteomic analysis using multiplex affinity reagents is perhaps the most reliable strategy to capture differentially expressed proteins that are slightly or immensely modified. In addition to expressional variation, it is comprehensively evident that the immunogenicity of a protein can be a deciding factor for instigating an inflammation afflicted-carcinogenesis. Considering both these factors, a simple and systematic strategy was designed to capture the immunogenic cancer biomarkers from sera of colorectal cancer patients. The affinity reagent, in the form of an antibody repertoire against the secretome of the HT29 cell line was used to grade the sera samples on the basis of the degree of immuno-reactivity and to capture differentially expressed antigens from the patient sera. Following affinity based 2DE-MALDI-TOF; the proteins were identified as (1) soluble vimentin; and (2) TGF-beta-inhibited membrane-associated protein (PP16B), in colon cancer sera and (3) keratin, type II cytoskeletal protein in rectal cancer sera. Pathway reconstruction and protein-protein networking of identified proteins predicted only Vimentin to be physically and genetically engaged in close proximity with the most established colorectal cancer associated tumorigenic pathways. Furthermore, our findings suggest that a possible surface stoichiometric shift in the structure of protein could be due to mutations in the coding sequence of Vimentin that may elicit its enhanced secretion possibly due to protein-hyperphosphorylation. Of the three proteins identified, only Vimentin showed higher expression in sera of colon cancer patients alone. Thus, it could be argued that vimentin might help in predicting individuals at higher risk of developing colon cancers. Our data are therefore suggestive of using vimentin as an antigen for tumor vaccination in an autologous set-up for colon cancers.

Autologous tumor cell vaccines for post-operative active-specific immunotherapy of colorectal carcinoma: long-term patient survival and mechanism of function

Colorectal cancer (CRC) is one of the leading causes of cancer-related deaths worldwide. Surgery remains the primary curative treatment but nearly 50% of patients relapse as consequence of micrometastatic or minimal residual disease (MRD) at the time of surgery. Spontaneous T-cell-mediated immune responses to CRC tumor-associated antigens (TAAs) in tumor-draining lymph nodes and in the bone marrow (BM) lead to infiltration of the tumors by lymphocytes. Certain types of such tumor-infiltrating lymphocytes (TILs) have a positive and others a negative impact on the patients' prognosis. This review focuses on advances in CRC active-specific immunotherapy (ASI), in particular on results from randomized controlled clinical studies employing therapeutic autologous tumor cell vaccines. The observed improvement of long-term survival is explained by activation and mobilization of a pre-existing repertoire of tumor-reactive memory T cells which, according to recent discoveries, reside in distinct niches of patients' bone marrow in neighborhood with hematopoietic (HSC) and mesenchymal (MSC) stem cells. Interestingly, memory T cells also contain a subset of stem memory T cells (SMTs) in addition to effector (EMTs) and central memory T cells (CMTs). The mechanism of function of a therapeutic vaccine in a chronic disease is distinct from that of prophylactic vaccines which have to generate de novo protective immune responses. The advantage of autologous vaccines for mobilization of a broad and highly individual repertoire of memory T cells will be discussed.

An inflammatory mediator, prostaglandin E2, in colorectal cancer

It is widely accepted that intake of dietary fats and chronic inflammation are risk factors for developing colorectal cancer. Arachidonic acid is a major component of animal fats, and the bioactive lipids produced from this substrate play critical roles in a variety of biologic processes, including cancer. Cyclooxygenase-derived prostaglandin E2 is a known proinflammatory lipid mediator that promotes tumor progression. Metabolism of arachidonic acid by the cyclooxygenase pathway provides one mechanism for the contribution of dietary fats and chronic inflammation to carcinogenesis. In this review, we highlight recent advances in our understanding of how a proinflammatory mediator prostaglandin E2 promotes colorectal cancer immune evasion. These findings may provide a rationale for the development of new therapeutic approaches to subvert tumor-induced immunosuppression.

Tandem therapy for retinoblastoma: immunotherapy and chemotherapy enhance cytotoxicity on retinoblastoma by increasing apoptosis

PURPOSE

The goal of this study was to provide an experimental basis for the clinical application of cell immunotherapy on RB in combination with chemotherapy treatment and to explore the mechanism of their combined cytotoxicity.

METHODS

We investigated the antitumor effect of cytokine-induced killer cells (CIK), co-cultivated with dendritic cells pulsed with tumor antigens (DC-Ag) and/or with carboplatin. Cytotoxicity was evaluated on a retinoblastoma cell line (RB-Y79) by FCM and immunofluorescence microscopy. Time-lapse video microscopy was used to follow the sequence of events during the carboplatin and CIK cytotoxicity.

RESULTS

Our results showed that a small proportion of RB-Y79 cells died after a low-dose carboplatin application. The cell population recovered 5 days after carboplatin was removed from the culture medium. Three times fewer normal epithelium retina cell lines (hTERT-RPE1) died at the same carboplatin dose. CIK achieved 5 times more cytotoxicity against RB cells pre-treated with low dose of carboplatin, showing the highest antitumor activity in the tandem carboplatin-DC-Ag-CIK-carboplatin treatment. Time-lapse video microscopy revealed that carboplatin-preconditioned RB cells are more avidly engaged by CIK cells, increasing RB mortality and resulting in an overall increment in apoptosis.

CONCLUSION

This study provides evidence that carboplatin combined with cell immunotherapy is superior to carboplatin alone to kill RB cells in vitro. We propose that a primary application of a low dose of a chemotherapeutic drug that is able to attack the tumor, and a subsequent treatment with highly effective immunotherapy based on DC-Ag-CIK cells could be a safe and selective treatment for RB.

Recombinant mammaglobin A adenovirus-infected dendritic cells induce mammaglobin A-specific CD8+ cytotoxic T lymphocytes against breast cancer cells in vitro

Mammaglobin A (MGBA) is a novel breast cancer-associated antigen almost exclusively over-expressed in primary and metastatic human breast cancers, making it a potential therapeutic target for breast cancer. The development of dendritic cell (DC)-induced tumor antigen specific CD8⁺ cytotoxic T lymphocytes (CTLs) may hold promise in cancer immunotherapy. In this study we constructed recombinant replication-defective adenoviral (Ad) vectors encoding MGBA and evaluated their ability to trigger anti-tumor immunity in vitro. DCs were isolated from the human peripheral blood monocyte cells (PBMCs) of two HLA-A33⁺ healthy female volunteers, and infected with adenovirus carrying MGBA cDNA (Ad-MGBA). After that, the Ad-MGBA-infected DCs were used to stimulate CD8⁺ CTLs in vitro and the latter was used for co-culture with breast cancer cell lines. The data revealed that infection with Ad-MGBA improved DC maturation and up-regulated the expression of co-stimulatory molecules and the secretion of interleukin-12 (IL-12), but down-regulated interleukin-10 (IL-10) secretion from DCs. Ad-MGBA-infected DC-stimulated CD8⁺CTLs displayed the highest cytotoxicity towards HLA-A33⁺/MGBA⁺ breast cancer MDA-MB-415 cells compared with other CD8⁺CTL populations, and compared with the cytotoxicity towards HLA-A33⁻/MGBA⁺ breast cancer HBL-100 cells and HLA-A33⁻/MGBA⁻ breast cancer MDA-MB 231 cells. In addition, Ad-MGBA-infected DC-stimulated CD8⁺ CTLs showed a high level of IFNγ secretion when stimulated with HLA-A33⁺/MGBA⁺ breast cancer MDA-MB-415 cells, but not when stimulated with HLA-A33⁻/MGBA⁺ HBL-100 and HLA-A33⁻/MGBA⁻MDA-MB-231 cells. In addition, killing of CD8⁺CTLs against breast cancer was in a major histocompability complex (MHC)-limited pattern. Finally, the data also determined the importance of TNF-α in activating DCs and T cells. These data together suggest that MGBA recombinant adenovirus-infected DCs could induce specific anti-tumor immunity against MGBA⁺ breast cancers, which could provide a novel strategy in the immunotherapy of breast cancer.

Cytokine-induced killer cells co-cultured with complete tumor antigen-loaded dendritic cells, have enhanced selective cytotoxicity on carboplatin-resistant retinoblastoma cells

Retinoblastoma (RB) is a challenging disease that affects mostly young children. Chemical therapy has been shown to have limitations during clinical practice, principally because of the ability of RB to become resistant to the treatment. Nevertheless, chemotherapy is still the main treatment for RB, and immunotherapy has become a promising treatment for most solid tumors with fewer side effects than traditional therapies. In this study, we explored the antitumor effects of cytokine-induced killer (CIK) cells co-cultured with dendritic cells (DCs) pulsed with complete tumor antigens (DC-Ag). Cytotoxicity and specificity were evaluated on an RB cell line (RB-Y79), on a human normal retina cell line (hTERT-RPE1) and a carboplatin-resistant RB cell line. Our results showed that CIK differentiation and cytotoxicity were enhanced by co-culturing CIKs with DC-Ag. Moreover, the co-culture improved the CIK proliferation rate by increasing IL-6 and decreasing IL-10 levels in the culture medium. Furthermore, the use of DC-Ag-CIK cells had little effect on normal retinal cells but high cytotoxicity on RB cells even on carboplatin-resistant retinoblastoma cells. This is the first study showing that DC cells pulsed with the complete tumor antigen improve proliferation, differentiation and cytotoxic activity of CIKs specific not only for RB but also for the chemotherapy-resistant form of the malady. Thus highly efficient immunotherapy based on DC-Ag-CIK cells may be a potential effective and safe mean of treating RB especially to patients where traditional chemical therapy has failed.

15 kDa granulysin causes differentiation of monocytes to dendritic cells but lacks cytotoxic activity

Granulysin is expressed as two isoforms by human cytotoxic cells: a single mRNA gives rise to 15 kDa granulysin, a portion of which is cleaved to a 9 kDa protein. Studies with recombinant 9 kDa granulysin have demonstrated its cytolytic and proinflammatory properties, but much less is known about the biologic function of the 15 kDa isoform. In this study, we show that the subcellular localization and functions of 9 and 15 kDa granulysin are largely distinct. Nine kilodalton granulysin is confined to cytolytic granules that are directionally released following target cell recognition. In contrast, 15 kDa granulysin is located in distinct granules that lack perforin and granzyme B and that are released by activated cytolytic cells. Although recombinant 9 kDa granulysin is cytolytic against a variety of tumors and microbes, recombinant 15 kDa granulysin is not. The 15 kDa isoform is a potent inducer of monocytic differentiation to dendritic cells, but the 9 kDa isoform is not. In vivo, mice expressing granulysin show markedly improved antitumor responses, with increased numbers of activated dendritic cells and cytokine-producing T cells. Thus, the distinct functions of granulysin isoforms have major implications for diagnosis and potential new therapies for human disease.

Chemokine-mediated distribution of dendritic cell subsets in renal cell carcinoma

Background

Renal cell carcinoma (RCC) represents one of the most immunoresponsive cancers. Antigen-specific vaccination with dendritic cells (DCs) in patients with metastatic RCC has been shown to induce cytotoxic T-cell responses associated with objective clinical responses. Thus, clinical trials utilizing DCs for immunotherapy of advanced RCCs appear to be promising; however, detailed analyses concerning the distribution and function of DC subsets in RCCs are lacking.

Methods

We characterized the distribution of the different immature and mature myeloid DC subsets in RCC tumour tissue and the corresponding normal kidney tissues. In further analyses, the expression of various chemokines and chemokine receptors controlling the migration of DC subsets was investigated.

Results

The highest numbers of immature CD1a+ DCs were found within RCC tumour tissue. In contrast, the accumulation of mature CD83+/DC-LAMP+ DCs were restricted to the invasive margin of the RCCs. The mature DCs formed clusters with proliferating T-cells. Furthermore, a close association was observed between MIP-3α-producing tumour cells and immature CCR6+ DC recruitment to the tumour bed. Conversely, MIP-3β and SLC expression was only detected at the tumour border, where CCR7-expressing T-cells and mature DCs formed clusters.

Conclusion

Increased numbers of immature DCs were observed within the tumour tissue of RCCs, whereas mature DCs were found in increased numbers at the tumour margin. Our results strongly implicate that the distribution of DC subsets is controlled by local lymphoid chemokine expression. Thus, increased expression of MIP-3α favours recruitment of immature DCs to the tumour bed, whereas de novo local expression of SLC and MIP-3β induces accumulation of mature DCs at the tumour margin forming clusters with proliferating T-cells reflecting a local anti-tumour immune response.

The tumor microenvironment in colorectal carcinogenesis

Colorectal cancer is the second leading cause of cancer-related mortality in the United States. Therapeutic developments in the past decade have extended life expectancy in patients with metastatic disease. However, metastatic colorectal cancers remain incurable. Numerous agents that were demonstrated to have significant antitumor activity in experimental models translated into disappointing results in extending patient survival. This has resulted in more attention being focused on the contribution of tumor microenvironment to the progression of a number of solid tumors including colorectal cancer. A more complete understanding of interactions between tumor epithelial cells and their stromal elements will enhance therapeutic options and improve clinical outcome. Here we will review the role of various stromal components in colorectal carcinogenesis and discuss the potential of targeting these components for the development of future therapeutic agents.