Pattern recognition receptors of innate immunity and their application to tumor immunotherapy

Tolerogenic dendritic cells in radiation-induced lung injury

Radiation-induced lung injury is a common complication associated with radiotherapy. It is characterized by early-stage radiation pneumonia and subsequent radiation pulmonary fibrosis. However, there is currently a lack of effective therapeutic strategies for radiation-induced lung injury. Recent studies have shown that tolerogenic dendritic cells interact with regulatory T cells and/or regulatory B cells to stimulate the production of immunosuppressive molecules, control inflammation, and prevent overimmunity. This highlights a potential new therapeutic activity of tolerogenic dendritic cells in managing radiation-induced lung injury. In this review, we aim to provide a comprehensive overview of tolerogenic dendritic cells in the context of radiation-induced lung injury, which will be valuable for researchers in this field.

Identification of an Immune-Related Gene Signature Associated with Prognosis and Tumor Microenvironment in Esophageal Cancer

Background

Esophageal cancer (EC) is a common malignant tumor of the digestive system with high mortality and morbidity. Current evidence suggests that immune cells and molecules regulate the initiation and progression of EC. Accordingly, it is necessary to identify immune-related genes (IRGs) affecting the biological behaviors and microenvironmental characteristics of EC.

Methods

Bioinformatics methods, including differential expression analysis, Cox regression, and immune infiltration prediction, were conducted using R software to analyze the Gene Expression Omnibus (GEO) dataset. The Cancer Genome Atlas (TCGA) cohort was used to validate the prognostic signature. Patients were stratified into high- and low-risk groups for further analyses, including functional enrichment, immune infiltration, checkpoint relevance, clinicopathological characteristics, and therapeutic sensitivity analyses.

Results

A prognostic signature was established based on 21 IRGs (S100A7, S100A7A, LCN1, CR2, STAT4, GAST, ANGPTL5, TRAV39, F2RL2, PGLYRP3, KLRD1, TRIM36, PDGFA, SLPI, PCSK2, APLN, TICAM1, ITPR3, MAPK9, GATA4, and PLAU). Compared with high-risk patients, better overall survival rates and clinicopathological characteristics were found in low-risk patients. The areas under the curve of the two cohorts were 0.885 and 0.718, respectively. Higher proportions of resting CD4⁺ memory T lymphocytes, M2 macrophages, and resting dendritic cells and lower proportions of follicular helper T lymphocytes, plasma cells, and neutrophils were found in the high-risk tumors. Moreover, the high-risk group showed higher expression of CD44 and TNFSF4, lower expression of PDCD1 and CD40, and higher TIDE scores, suggesting they may respond poorly to immunotherapy. High-risk patients responded better to chemotherapeutic agents such as docetaxel, doxorubicin, and gemcitabine. Furthermore, IRGs associated with tumor progression, including PDGFA, ITPR3, SLPI, TICAM1, and GATA4, were identified.

Conclusion

Our immune-related signature yielded reliable value in evaluating the prognosis, microenvironmental characteristics, and therapeutic sensitivity of EC and may help with the precise treatment of this patient population.

IL-27 Improves Prophylactic Protection Provided by a Dead Tumor Cell Vaccine in a Mouse Melanoma Model

The protocol used to induce cell death for generating vaccines from whole tumor cells is a critical consideration that impacts vaccine efficacy. Here we compared how different protocols used to induce cell death impacted protection provided by a prophylactic whole tumor cell vaccine in a mouse melanoma model. We found that melanoma cells exposed to γ-irradiation or lysis combined with UV-irradiation (LyUV) provided better protection against tumor challenge than lysis only or cells exposed to UV-irradiation. Furthermore, we found that the immunoregulatory cytokine, IL-27 enhanced protection against tumor growth in a dose-dependent manner when combined with either LyUV or γ-irradiated whole tumor cell vaccine preparations. Taken together, this data supports the use of LyUV as a potential protocol for developing whole tumor cell prophylactic cancer vaccines. We also showed that IL-27 can be used at low doses as a potent adjuvant in combination with LyUV or γ-irradiation treated cancer cells to improve the protection provided by a prophylactic cancer vaccine in a mouse melanoma model.

TLR3/TICAM-1 signaling in tumor cell RIP3-dependent necroptosis

The engagement of Toll-like receptor 3 (TLR3) leads to the oligomerization of the adaptor TICAM-1 (TRIF), which can induces either of three acute cellular responses, namely, cell survival coupled to Type I interferon production, or cell death, via apoptosis or necrosis. The specific response elicited by TLR3 determines the fate of affected cells, although the switching mechanism between the two cell death pathways in TLR3-stimulated cells remains molecularly unknown. Tumor necrosis factor α (TNFα)-mediated cell death can proceed via apoptosis or via a non-apoptotic pathway, termed necroptosis or programmed necrosis, which have been described in detail. Interestingly, death domain-containing kinases called receptor-interacting protein kinases (RIPs) are involved in the signaling pathways leading to these two cell death pathways. Formation of the RIP1/RIP3 complex (called necrosome) in the absence of caspase 8 activity is crucial for the induction of necroptosis in response to TNFα signaling. On the other hand, RIP1 is known to interact with the C-terminal domain of TICAM-1 and to modulate TLR3 signaling. In macrophages and perhaps tumor cell lines, RIP1/RIP3-mediated necroptotic cell death can ensue the administration of the TLR agonist polyI:C. If this involved the TLR3/TICAM-1 pathway, the innate sensing of viral dsRNA would be linked to cytopathic effects and to persistent inflammation, in turn favoring the release of damage-associated molecular patterns (DAMPs) in the microenvironment. Here, we review accumulating evidence pointing to the involvement of the TLR3/TICAM-1 axis in tumor cell necroptosis and the subsequent release of DAMPs.

Cross-priming for antitumor CTL induced by soluble Ag + polyI:C depends on the TICAM-1 pathway in mouse CD11c(+)/CD8α(+) dendritic cells

PolyI:C is a nucleotide pattern molecule that induces cross-presentation of foreign Ag in myeloid dendritic cells (DC) and MHC Class I-dependent proliferation of cytotoxic T lymphocytes (CTL). DC (BM or spleen CD8α⁺) have sensors for dsRNA including polyI:C to signal facilitating cross-presentation. Endosomal TLR3 and cytoplasmic RIG-I/MDA5 are reportedly responsible for polyI:C sensing and presumed to deliver signal for cross-presentation via TICAM-1 (TRIF) and IPS-1 (MAVS, Cardif, VISA) adaptors, respectively. In fact, when tumor-associated Ag (TAA) was simultaneously taken up with polyI:C in DC, the DC cross-primed CTL specific to the TAA in a syngenic mouse model. Here we tested which of the TICAM-1 or IPS-1 pathway participate in cross-presentation of tumor-associated soluble Ag and retardation of tumor growth in the setting with a syngeneic tumor implant system, EG7/C57BL6, and exogenously challenged soluble Ag (EG7 lysate) and polyI:C. When EG7 lysate and polyI:C were subcutaneously injected in tumor-bearing mice, EG7 tumor growth retardation was observed in wild-type and to a lesser extent IPS-1^−/− mice, but not TICAM-1^−/− mice. IRF-3/7 were essential but IPS-1 and type I IFN were minimally involved in the polyI:C-mediated CTL proliferation. Although both TICAM-1 and IPS-1 contributed to CD86/CD40 upregulation in CD8α⁺ DC, H2K^b-SL8 tetramer and OT-1 proliferation assays indicated that OVA-recognizing CD8 T cells predominantly proliferated in vivo through TICAM-1 and CD8α⁺ DC is crucial in ex vivo analysis. Ultimately, tumor regresses > 8 d post polyI:C administration. The results infer that soluble tumor Ag induces tumor growth retardation, i.e., therapeutic potential, if the TICAM-1 signal coincidentally occurs in CD8α⁺ DC around the tumor.

Development of a novel TLR8 agonist for cancer immunotherapy

Toll-like receptors (TLRs) are a family of proteins that recognize pathogen associated molecular patterns (PAMPs). Their primary function is to activate innate immune responses while also involved in facilitating adaptive immune responses. Different TLRs exert distinct functions by activating varied immune cascades. Several TLRs are being pursued as cancer drug targets. We discovered a novel, highly potent and selective small molecule TLR8 agonist DN052. DN052 exhibited strong in vitro cellular activity with EC50 at 6.7 nM and was highly selective for TLR8 over other TLRs including TLR4, 7 and 9. DN052 displayed excellent in vitro ADMET and in vivo PK profiles. DN052 potently inhibited tumor growth as a single agent. Moreover, combination of DN052 with the immune checkpoint inhibitor, selected targeted therapeutics or chemotherapeutic drugs further enhanced efficacy of single agents. Mechanistically, treatment with DN052 resulted in strong induction of pro-inflammatory cytokines in ex vivo human PBMC assay and in vivo monkey study. GLP toxicity studies in rats and monkeys demonstrated favorable safety profile. This led to the advancement of DN052 into phase 1 clinical trials.

Self-assembled nanovehicle-mediated co-encapsulation of inactivated EV71 virus and CpG oligonucleotides elicits potent anti-EV71 humoral and cellular immune protective responses

Inactivated vaccines are widely used for prevention of viral disease. Both humoral and cellular immune responses have been shown to play important roles in the control and clearance of virus infections. CpG motif containing oligodeoxynucleotides (ODN) have recently gained considerable interest and been used as vaccine adjuvant due to their potent abilities to modulate host immune response. In this study, CpG-ODN adjuvant and inactivated viral particles of enterovirus 71 (EV71) were co-encapsulated into nanoparticles (NP) generated by using protamine sulfate (PS) and carboxymethyl β-glucan (CMG) through a self-assembly approach. The administration of EV71 nanovaccine elicited not only specific anti-EV71 neutralizing antibody response, but also cellular immune response characterized by strong productions of IFN-α and IFN-γ. The results suggest that CMG/PS-based nanovehicles hold a great potential to be a novel platform for nanovaccine development against viral disease.

Polymeric Caffeic Acid Is a Safer Mucosal Adjuvant That Augments Antigen-Specific Mucosal and Systemic Immune Responses in Mice

Infections remain a major threat to human lives. To overcome the threat caused by pathogens, mucosal vaccines are considered a promising strategy. However, no inactivated and/or subunit mucosal vaccine has been approved for human use, largely because of the lack of a safe and effective mucosal adjuvant. Here, we show that enzymatically synthesized polymeric caffeic acid (pCA) can act as a potent mucosal adjuvant in mice. Intranasal administration of ovalbumin (OVA) in combination with pCA resulted in the induction of OVA-specific mucosal IgA and serum IgG, especially IgG1. Importantly, pCA was synthesized from caffeic acid and horseradish peroxidase from coffee beans and horseradish, respectively, which are commonly consumed. Therefore, pCA is believed to be a highly safe material. In fact, administration of pCA did not show distinct toxicity in mice. These data indicate that pCA has merit for use as a mucosal adjuvant for nasal vaccine formulations.

The kinase TBK1 functions in dendritic cells to regulate T cell homeostasis, autoimmunity, and antitumor immunity

Dendritic cells (DCs) are crucial for mediating immune responses but, when deregulated, also contribute to immunological disorders, such as autoimmunity. The molecular mechanism underlying the function of DCs is incompletely understood. In this study, we have identified TANK-binding kinase 1 (TBK1), a master innate immune kinase, as an important regulator of DC function. DC-specific deletion of Tbk1 causes T cell activation and autoimmune symptoms and also enhances antitumor immunity in animal models of cancer immunotherapy. The TBK1-deficient DCs have up-regulated expression of co-stimulatory molecules and increased T cell-priming activity. We further demonstrate that TBK1 negatively regulates the induction of a subset of genes by type I interferon receptor (IFNAR). Deletion of IFNAR1 could largely prevent aberrant T cell activation and autoimmunity in DC-conditional Tbk1 knockout mice. These findings identify a DC-specific function of TBK1 in the maintenance of immune homeostasis and tolerance.

Lack of Association Between Polymorphism rs4986791 in TLR4 and Primary Open-Angle Glaucoma in a Saudi Cohort

AIMS

To investigate whether single nucleotide polymorphism (SNP) rs4986791 (C>T) in the toll-like receptor 4 (TLR4) gene is a risk factor for primary open-angle glaucoma (POAG) in the Saudi population.

METHOD

A case-control study was performed to genotype a cohort of 85 POAG patients and 95 matched healthy controls utilizing TaqMan(®). The association between mutant genotypes and various POAG clinical indices were investigated.

RESULTS

The wild-type (C/C), heterozygous (C/T), and homozygous (T/T) genotypes were observed in 85.9%, 12.9%, and 1.2% POAG cases, respectively, compared to 91.6%, 8.4%, and none, respectively, among controls. The minor allele frequency was 0.076 in cases and 0.042 in controls. Both the genotype and allele frequency among POAG cases and controls did not vary significantly. With the exception of family history of glaucoma (p = 0.032), no significant association of genotypes was seen with age, intraocular pressure, cup/disc ratio, number of antiglaucoma medications, and other systemic comorbidities among the POAG cases.

CONCLUSION

We did not detect any direct association between genotypes or allele frequencies of SNP rs4986791 in the TLR4 gene and POAG.

Analysis of Toll-Like Receptor 2 Polymorphism (rs5743704) in Saudi Patients with Primary Open-Angle Glaucoma

AIMS

To investigate whether the single-nucleotide polymorphism (SNP) rs5743704 in the toll-like receptor 2 gene is associated with primary open-angle glaucoma (POAG) or any of its clinical indices in a Saudi cohort.

METHOD

Ninety-five unrelated POAG cases and 95 controls of Saudi origin were genotyped utilizing a TaqMan(®) assay. The association between genotypes and various clinical indices important for POAG were investigated.

RESULTS

The genotypic and allelic frequencies among cases were not significantly different when compared to controls. The minor allele frequency was 0.021 in cases and 0.011 in controls. No significant association was seen with intraocular pressure and cup/disc ratio. However, carriers of the C/A genotype had higher number of anti-glaucoma medications compared to controls (p = 0.04).

CONCLUSION

SNP rs5773704 is not associated with POAG in a Saudi population. Despite sample size limitation, the association of the minor allele A with higher number of anti-glaucoma medications suggests a possible indirect role for this SNP in predicting disease severity.

Modulation of APC Function and Anti-Tumor Immunity by Anti-Cancer Drugs

Professional antigen-presenting cells (APCs), such as dendritic cells (DCs), are central to the initiation and regulation of anti-cancer immunity. However, in the immunosuppressive environment within a tumor APCs may antagonize anti-tumor immunity by inducing regulatory T cells (Tregs) or anergy of effector T cells due to lack of efficient costimulation. Hence, in an optimal setting, anti-cancer drugs have the power to reduce tumor size and thereby may induce the release of tumor antigens and, at the same time, modulate APC function toward efficient priming of antigen-specific effector T cells. Selected cytotoxic agents may revert APC dysfunction either by directly maturing DCs or through induction of immunogenic tumor cell death. Furthermore, specific cytotoxic agents may support adaptive immunity by selectively depleting regulatory subsets, such as Tregs or myeloid-derived suppressor cells. Perspectively, this will allow developing effective combination strategies with novel immunotherapies to exert complementary pressure on tumors via direct toxicity as well as immune activation. We, here, review our current knowledge on the capacity of anti-cancer drugs to modulate APC functions to promote durable anti-cancer immune responses.

Myeloid-derived suppressor cells confer tumor-suppressive functions on natural killer cells via polyinosinic:polycytidylic acid treatment in mouse tumor models

Polyinosinic:polycytidylic acid (poly I:C), a synthetic double-stranded RNA, acts on myeloid cells and induces potent antitumor immune responses including natural killer (NK) cell activation. Myeloid-derived suppressor cells (MDSCs) systemically exist in tumor-bearing hosts and have strong immunosuppressive activity against antitumor effector cells, thereby dampening the efficacy of cancer immunotherapy. Here we tested what happened in MDSCs in poly I:C-treated mice. NK-sensitive syngenic tumor (B16)-bearing C57BL/6 mice were employed for this study. Intraperitoneal poly I:C treatment induced MDSC activation, driving CD69 expression and interferon (IFN)-γ production in NK cells. IFN-γ directly inhibited proliferation of B16 cells. This NK cell priming led to growth retardation of B16 tumors, although no direct tumoricidal activity was induced in NK cells. Mechanistic analysis using KO mice and function-blocking monclonal antibody revealed that MDSCs produced IFN-α via the mitochondrial antiviral signaling protein (MAVS) pathway after in vivo administration of poly I:C, and activated NK cells through the IFNAR pathway. MDSC-mediated NK cell priming was reconstituted by IFN-α in a coculture system. Either the MAVS or IFNAR signaling pathway was required for activation of MDSCs that led to growth retardation of B16 tumor in vivo. The results infer that MDSC is a target of poly I:C to prime NK cells, which exert antitumor activity to NK-sensitive tumor cells.

Correlation of Asp299Gly and Thr399Ile polymorphisms in toll-like receptor 4 gene with digestive cancer risk: A meta-analysis

The aim of this meta-analysis was to evaluate the correlation between the Asp299Gly and Thr399Ile polymorphisms in the toll-like receptor 4 (TLR4) gene and the risk of digestive cancer. A comprehensive search in PubMed, Web of Science (ISI), the China National Knowledge Infrastructure (CNKI), the Database of Chinese Scientific and Technical Periodicals (VIP) and the China Biology Medical (CBM) literature databases, including all the studies until May 25 2012, was conducted in order to investigate the abovementioned correlation. Statistical analysis was performed using STATA version 10.1. A total of 12 case-control studies were identified comprising 1,877 cancer patients and 3,181 controls for Asp299Gly polymorphism, and 8 case-control studies with 1,062 cancer patients and 1,867 controls for Thr399Ile polymorphism. Following sensitivity analysis and excluding studies that deviated from the Hardy-Weinberg equilibrium (HWE) in the controls, this meta-analysis demonstrated a significant correlation between the G allele of the Asp299Gly polymorphism and increased risk of gastric cancer in dominant [fixed-effect model (FEM): odds ratio (OR), 1.772; 95% confidence interval (CI), 1.340-2.343] and codominant (FEM: OR, 1.761, CI, 1.347-2.301) models. However, no significant correlation was detected for overall digestive and colorectal cancer. Furthermore, following the sensitivity analysis and exclusion of studies deviating from HWE in controls, no significant effect of the T allele of Thr399Ile polymorphism on overall digestive, gastric and colorectal cancer risk was demonstrated. This study suggests that the G allele of the TLR4 Asp299Gly polymorphism might be correlated with an increased risk of gastric cancer. However, this result needs to be further investigated by future studies.

Polymorphisms of the TLR2 and TLR4 genes are associated with risk of gastric cancer in a Brazilian population

AIM: To investigate toll-like receptor 2 (TLR2) -196 to -174 del, and TLR4 (+896A/G rs4986790 and +1196C/T rs4986791) polymorphisms at risk of chronic gastritis and gastric cancer in a Brazilian population and association of gastric lesions with risk factors such as smoking, alcohol intake and Helicobacter pylori infection.

METHODS: In this case-control study, polymorphism at TLR2 -196 to -174 del was investigated by using the allele-specific polymerase chain reaction (PCR) method, while the PCR-restriction fragment length polymorphism technique was carried out to identify the TLR4 (rs4986790 and rs4986791) genotypes in 607 Brazilian individuals (208 with chronic gastritis-CG, 174 with gastric cancer-GC and 225 controls -C).

RESULTS: The single nucleotide polymorphisms TLR4+1196C/T was not associated with risk of chronic gastritis or gastric cancer and the homozygous genotypes TLR4+896GG and TLR4+1196TT were absent in the studied population. However, the frequency of TLR2 -196 to -174 ins/del + del/del and TLR4+896AG genotypes was significantly higher (P < 0.01 and P = 0.01, respectively) in the cancer group (33.4% and 11.5%, respectively) than in the control group (16.9% and 4.5%, respectively). It was also observed that the G-C haplotype of the TLR4+896A/G+1196C/T (P = 0.02) and the combination of variant alleles of the TLR2/TLR4+896G (P = 0.02) are associated with susceptibility to gastric cancer. In addition, the multiple logistic regression showed that male gender [odds ratio (OR) = 2.70; 95% CI: 1.66-4.41; P < 0.01], alcohol intake (OR = 2.93; 95% CI: 1.76-4.87; P < 0.01), TLR2 -196 to -174 del (OR = 2.64; 95% CI: 1.56-4.44; P < 0.01) and TLR4+896G (OR = 3.19; 95% CI: 1.34- 7.61; P < 0.01) polymorphisms were associated with a higher susceptibility to developing this neoplasm.

CONCLUSION: Our data indicate that TLR2 -196 to -174 del and TLR4+896G may increase the risk of gastric cancer in a Brazilian population.

The effects of TLR activation on T-cell development and differentiation

Invading pathogens have unique molecular signatures that are recognized by Toll-like receptors (TLRs) resulting in either activation of antigen-presenting cells (APCs) and/or costimulation of T cells inducing both innate and adaptive immunity. TLRs are also involved in T-cell development and can reprogram Treg cells to become helper cells. T cells consist of various subsets, that is, Th1, Th2, Th17, T follicular helper (Tfh), cytotoxic T lymphocytes (CTLs), regulatory T cells (Treg) and these originate from thymic progenitor thymocytes. T-cell receptor (TCR) activation in distinct T-cell subsets with different TLRs results in differing outcomes, for example, activation of TLR4 expressed in T cells promotes suppressive function of regulatory T cells (Treg), while activation of TLR6 expressed in T cells abrogates Treg function. The current state of knowledge of regarding TLR-mediated T-cell development and differentiation is reviewed.

Evaluation of innate immune signaling pathways in transformed cells

Oncolytic viruses, the use of viruses to treat cancer, is emerging as a new option for cancer therapy. Oncolytic viruses, of both DNA and RNA origin, exhibit the ability to preferentially replicate in and kill cancer cells plausibly due to defects in innate immune signaling or translation regulation that are acquired during cellular transformation. Here, we review concepts and assays that describe how to analyze signaling pathways that govern the regulation of Type I IFN production as well as the induction of interferon-stimulated antiviral genes, events that are critical for mounting an effective antiviral response. The following procedures can be used to assess whether innate immune pathways that control antiviral host defense are defective in tumor cells - mechanisms that may help to explain viral oncolysis.

TRAIL/DR5 plays a critical role in NK cell-mediated negative regulation of dendritic cell cross-priming of T cells

Dendritic cells (DCs) are critical in initiating immune responses by cross-priming of tumor Ags to T cells. Previous results showed that NK cells inhibited DC-mediated cross-presentation of tumor Ags both in vivo and in vitro. In this study, enhanced Ag presentation was observed in draining lymph nodes in TRAIL(-/-) and DR5(-/-) mice compared with that of wild-type mice. NK cells inhibit DC cross-priming of tumor Ags in vitro, but not direct presentation of endogenous Ags. NK cells lacking TRAIL, but not perforin, were not able to inhibit DC cross-priming of tumor Ags. DCs that lack expression of TRAIL receptor DR5 were less susceptible to NK cell-mediated inhibition of cross-priming, and cross-linking of DR5 receptor led to reduced generation of MHC class I-Ag peptide complexes, followed by attenuated cross-priming of CD8(+) T cells. In addition, key molecules involved in the TRAIL/DR5 pathway during DC/NK cell interactions were determined. In summary, these data indicate a novel alternative pathway for DC/NK cell interactions in antitumor immunity and may reflect homeostasis of both DCs and NK cells for regulation of CD8(+) T cell function in physiological conditions.

Innate immunity and vaccine

Immune adjuvant is an artificial pathogen-associated molecular patterns (PAMP) for potentiating various immune responses. Vaccine represents one event that is capable of inducing immune response caused by antigen and PAMP stimuli, which act on antigen-presenting dendritic cells (mDCs). Here, we introduce the pathways by which CTL and NK cells are driven through mDC maturation in response to adjuvants.

The peptide sequence of diacyl lipopeptides determines dendritic cell TLR2-mediated NK activation

Natural killer (NK) cells are lymphocyte effectors that are activated to control certain microbial infections and tumors. Many NK-activating and regulating receptors are involved in regulating NK cell function. In addition, activation of naïve NK cells is fundamentally triggered by cytokines or myeloid dendritic cells (mDC) in various modes. In this study, we synthesized 16 S-[2,3-bis(palmitoyl)propyl]cysteine (Pam2Cys) lipopeptides with sequences designed from lipoproteins of Staphylococcus aureus, and assessed their functional properties using mouse (C57BL/6) bone marrow-derived DC (BMDC) and NK cells. NK cell activation was evaluated by three criteria: IFN-γ production, up-regulation of NK activation markers and cytokines, and NK target (B16D8 cell) cytotoxicity. The diacylated lipopeptides acted as TLR2 ligands, inducing up-regulation of CD25/CD69/CD86, IL-6, and IL-12p40, which represent maturation of BMDC. Strikingly, the Pam2Cys lipopeptides induced mouse NK cell activation based on these criteria. Cell-cell contact by Pam2Cys peptide-stimulated BMDC and NK cells rather than soluble mediators released by stimulated BMDC induced activation of NK cells. For most lipopeptides, the BMDC TLR2/MyD88 pathway was responsible for driving NK activation, while some slightly induced direct activation of NK cells via the TLR2/MyD88 pathway in NK cells. The potential for NK activation was critically regulated by the peptide primary sequence. Hydrophobic or proline-containing sequences proximal to the N-terminal lipid moiety interfered with the ability of lipopeptides to induce BMDC-mediated NK activation. This mode of NK activation is distinctly different from that induced by polyI:C, which is closely associated with type I IFN-inducing pathways of BMDC. These results imply that the MyD88 pathway of BMDC governs an alternative NK-activating pathway in which the peptide sequence of TLR2-agonistic lipopeptides critically affects the potential for NK activation.

Gemcitabine in combination with dendritic cell-induced immunoeffector cells inhibits the growth of BxPC-3 cells

AIM: To investigate the effect of gemcitabine (GEM) in combination with T lymphocytes activated by BxPC-3 cell whole lysate-pulsed dendritic cells (DCs) on the growth of BxPC-3 cells.

METHODS: After T lymphocytes were incubated with monocyte-derived DCs sensitized with whole lysate of BxPC-3 cells, the concentrations of IL-2, IFN-γ, TNF-α, IL-10 and TGF-β in cell supernatants were measured by enzyme-linked immunosorbent assay (ELISA). Subsequently, GEM and activated T lymphocytes, alone or in combination, were added into cultured BxPC-3 cells. After incubation for 24 h, BxPC-3 cell proliferation was measured by methyl thiazolyl tetrazolium (MTT) assay and colony formation assay, and early apoptosis of BxPC-3 cells was detected by flow cytometry.

RESULTS: After stimulation with sensitized DCs, the secretion of IL-2, IFN-γ and TNF-α by T lymphocytes was significantly enhanced (1 379 ng/L ± 307 ng/L vs 370 ng/L ± 64 ng/L, 1 269 ng/L ± 264 ng/L vs 420 ± 114 ng/L, and 1 062 ng/L ± 172 ng/L vs 515 ± 27 ng/L, all P < 0.01), while the production of IL-10 and TGF-β showed no significant changes (both P > 0.05). Compared with the negative control group, activated T lymphocytes and GEM, alone or in combination, could inhibit the growth of BxPC-3 cells. The death rate and apoptosis rate were highest, and the rate of colony formation was lowest in BxPC-3 cells treated with activated T lymphocytes and GEM in combination.

CONCLUSION: DCs sensitized with BxPC-3 cell whole lysate can induce the formation of tumor-killing cytotoxic T cells. Dendritic cell-induced immunoeffector cells in combination with gemcitabine have stronger tumor-killing activity than immunoeffector cells alone.