RNA interference-mediated silencing of Foxo3 in antigen-presenting cells as a strategy for the enhancement of DNA vaccine potency

Cancer biotherapy: review and prospect

Malignant tumors pose a grave threat to the quality of human life. The prevalence of malignant tumors in China is steadily rising. Presently, clinical interventions encompass surgery, radiotherapy, and pharmaceutical therapy in isolation or combination. Nonetheless, these modalities fail to completely eradicate malignant tumor cells, frequently leading to metastasis and recurrence. Conversely, tumor biotherapy has emerged as an encouraging fourth approach in preventing and managing malignant tumors owing to its safety, efficacy, and minimal adverse effects. Currently, a range of tumor biotherapy techniques are employed, including gene therapy, tumor vaccines, monoclonal antibody therapy, cancer stem cell therapy, cytokine therapy, and adoptive cellular immunotherapy. This study aims to comprehensively review the latest developments in biological treatments for malignant tumors.

A small interfering RNA (siRNA) database for SARS-CoV-2

Coronavirus disease 2019 (COVID-19) rapidly transformed into a global pandemic, for which a demand for developing antivirals capable of targeting the SARS-CoV-2 RNA genome and blocking the activity of its genes has emerged. In this work, we presented a database of SARS-CoV-2 targets for small interference RNA (siRNA) based approaches, aiming to speed the design process by providing a broad set of possible targets and siRNA sequences. The siRNAs sequences are characterized and evaluated by more than 170 features, including thermodynamic information, base context, target genes and alignment information of sequences against the human genome, and diverse SARS-CoV-2 strains, to assess possible bindings to off-target sequences. This dataset is available as a set of four tables, available in a spreadsheet and CSV (Comma-Separated Values) formats, each one corresponding to sequences of 18, 19, 20, and 21 nucleotides length, aiming to meet the diversity of technology and expertise among laboratories around the world. A metadata table (Supplementary Table S1), which describes each feature, is also provided in the aforementioned formats. We hope that this database helps to speed up the development of new target antivirals for SARS-CoV-2, contributing to a possible strategy for a faster and effective response to the COVID-19 pandemic.

The Expression Profile of mRNA and tRNA Genes in Splenocytes and Neutrophils after In Vivo Delivery of Antitumor Short Hairpin RNA of Indoleamine 2,3- Dioxygenase

RNA-based therapeutics are considered as novel treatments for human diseases. Our previous study demonstrated that treatment with short-hairpin RNA against Ido1 (IDO shRNA) suppresses tumor growth, detects Th1-bias immune responses, and elevates expression of tryptophan transfer RNA (tRNA^Trp) in total splenocytes. In addition, depletion of Ly6g⁺ neutrophils attenuates the effect of IDO shRNA. The aim of this study was to investigate the regulatory network and the expression profile of tRNAs and other non-coding RNAs in IDO shRNA-treated spleens. The total splenocytes and magnetic bead-enriched splenic neutrophils were collected from the lung tumor bearing mice, which were treated with IDO shRNA or scramble IDO shRNA, and the collected cells were subsequently subjected to RNA sequencing. The gene ontology analysis revealed the different enrichment pathways in total splenocytes and splenic neutrophils. Furthermore, the expression of tRNA genes was identified and validated. Six isoacceptors of tRNA, with different expression patterns between total splenocytes and splenic neutrophils, were observed. In summary, our findings not only revealed novel biological processes in IDO shRNA-treated total splenocytes and splenic neutrophils, but the identified tRNAs and other non-coding RNAs may contribute to developing a novel biomarker gene set for evaluating the clinical efficiency of RNA-based cancer immunotherapies.

The transcription factor Foxp1 regulates the differentiation and function of dendritic cells

Dendritic cells (DCs) are the sentinels of the immune system and play a critical role in initiating adaptive immune responses against pathogens. As the most powerful antigen presenting cells, DCs are also important in maintaining immune homeostasis and participating in the development of autoimmune diseases. How the maturation and function of DCs is regulated in these conditions and what is the function of various transcription factors is still unclear. In this study, we found that the expression of the transcription factor Foxp1 gradually increased during the maturation of DCs. Then, we constructed a recombinant adenovirus carrying Foxp1-interfering RNA (Ad-simFoxp1) and transfected murine bone marrow-derived DCs in vitro. DCs transfected with Ad-simFoxp1 exhibited markedly lower costimulatory molecules, and decreased cytokines. And Ad-simFoxp1 greatly inhibited mature DC-induced T cell responses. Moreover, in vivo infusion with Ad-simFoxp1-modified DCs significantly delayed the onset of experimental autoimmune encephalomyelitis (EAE). Therefore, adoptive transfection of Ad-simFoxp1 in DCs may be a potential treatment strategy against autoimmune diseases.

Cancer Immunotherapy: Silencing Intracellular Negative Immune Regulators of Dendritic Cells

Dendritic cells (DCs) are capable of activating adaptive immune responses, or inducing immune suppression or tolerance. In the tumor microenvironment, the function of DCs is polarized into immune suppression that attenuates the effect of T cells, promoting differentiation of regulatory T cells and supporting tumor progression. Therefore, blocking negative immune regulators in DCs is considered a strategy of cancer immunotherapy. Antibodies can target molecules on the cell surface, but not intracellular molecules of DCs. The delivery of short-hairpin RNAs (shRNA) and small-interfering RNAs (siRNA) should be a strategy to silence specific intracellular targets in DCs. This review provides an overview of the known negative immune regulators of DCs. Moreover, a combination of shRNA/siRNA and DC vaccines, DNA vaccines in animal models, and clinical trials are also discussed.

Unravelling the role of fatty acid metabolism in cancer through the FOXO3-FOXM1 axis

Obesity and cachexia represent divergent states of nutritional and metabolic imbalance but both are intimately linked to cancer. There is an extensive overlap in their signalling pathways and molecular components involved such as fatty acids (FAs), which likely play a crucial role in cancer. Forkhead box (FOX) proteins are responsible of a wide range of transcriptional programmes during normal development, and the FOXO3-FOXM1 axis is associated with cancer initiation, progression and drug resistance. Free fatty acids (FFAs), FA synthesis and β-oxidation are associated with cancer development and progression. Meanwhile, insulin and some adipokines, that are up-regulated by FAs, are also involved in cancer development and poor prognosis. In this review, we discuss the role of FA metabolism in cancer and how FA metabolism integrates with the FOXO3-FOXM1 axis. These new insights may provide leads to better cancer diagnostics as well as strategies for tackling cancer development, progression and drug resistance.

A short hairpin RNA-based adjuvant targeting NF-κB repressor IκBα promotes migration of dermal dendritic cells to draining lymph nodes and antitumor CTL responses induced by DNA vaccination

DNA vaccination is an attractive approach to elicit tumor-specific cytotoxic CD8⁺ T lymphocytes (CTL), which can mediate protective immunity against tumors. To initiate CTL responses, antigen-encoding plasmids employed for DNA vaccination need to activate dendritic cells (DC) through the stimulation of DNA-sensing innate immune receptors that converge in the activation of the master transcription factor NF-κB. To this end, NF-κB repressor IκBα needs to be degraded, allowing NF-κB to translocate to the nucleus and transcribe proinflammatory target genes, as well as its repressor IκBα. Therefore, NF-κB activation is self-limited by de novo synthesis of IκBa, which sequesters NF-κB in the cytosol. Hence, we tested whether co-delivering a shRNA-based adjuvant able to silence IκBα expression would further promote DNA-induced NFκB activation, DC activation and tumor-protective CTL responses induced by DNA vaccination in a preclinical model. First, an IκBα-targeting shRNA plasmid (shIκBα) was shown to reduce IκBα expression and promote NFκB-driven transcription in vitro, as well as up-regulate inflammatory target genes in vivo. Then, we showed that intradermal DNA electroporation induced the migration of skin migratory dendritic cells to draining lymph nodes and maturation of dermal dendritic cells (dDC). Interestingly, shIκBα further promoted the migration of mature skin migratory dendritic cells, in particular dDC, which are specialized in antigen cross-presentation and activation of CD8⁺ T cells. Consistently, mice vaccinated with a plasmid encoding the melanoma-associated antigen tyrosinase-related protein 2 (TRP2) in combination with shIκBα enhanced TRP2-specific CTL responses and reduced the number of lung melanoma foci in mice challenged with intravenous injection of B16F10 cells. Moreover, therapeutic vaccination with pTRP2 and shIκBα delayed the growth of B16F10 melanoma subcutaneous tumors. Our data suggest that adjuvants promoting NF-κB activation represent an attractive strategy to boost DC activation and promote the generation of tumor-protective CTL responses elicited by DNA vaccines.

Future directions in bladder cancer immunotherapy: towards adaptive immunity

The clinical management of bladder cancer has not changed significantly in several decades. In particular, intravesical bacillus Calmette-Guérin (BCG) immunotherapy has been a mainstay for high-risk nonmuscle invasive bladder cancer since the late 1970s/early 1980s. This is despite the fact that bladder cancer has the highest recurrence rates of any cancer and BCG immunotherapy has not been shown to induce a tumor-specific immune response. We and others have hypothesized that immunotherapies capable of inducing tumor-specific adaptive immunity are needed to impact bladder cancer morbidity and mortality. This article summarizes the preclinical and clinical development of bladder cancer immunotherapies with an emphasis on the last 5 years. Expected progress in the near future is also discussed.

Molecular mechanisms for enhanced DNA vaccine immunogenicity

In the two decades since their initial discovery, DNA vaccines technologies have come a long way. Unfortunately, when applied to human subjects inadequate immunogenicity is still the biggest challenge for practical DNA vaccine use. Many different strategies have been tested in preclinical models to address this problem, including novel plasmid vectors and codon optimization to enhance antigen expression, new gene transfection systems or electroporation to increase delivery efficiency, protein or live virus vector boosting regimens to maximise immune stimulation, and formulation of DNA vaccines with traditional or molecular adjuvants. Better understanding of the mechanisms of action of DNA vaccines has also enabled better use of the intrinsic host response to DNA to improve vaccine immunogenicity. This review summarizes recent advances in DNA vaccine technologies and related intracellular events and how these might impact on future directions of DNA vaccine development.

Modulating APOBEC expression enhances DNA vaccine immunogenicity

DNA vaccines have failed to induce satisfactory immune responses in humans. Several mechanisms of double-stranded DNA (dsDNA) sensing have been described, and modulate DNA vaccine immunogenicity at many levels. We hypothesized that the immunogenicity of DNA vaccines in humans is suppressed by APOBEC (apolipoprotein B (APOB) mRNA-editing, catalytic polypeptide)-mediated plasmid degradation. We showed that plasmid sensing via STING (stimulator of interferon (IFN) genes) and TBK-1 (TANK-binding kinase 1) leads to IFN-β induction, which results in APOBEC3A mRNA upregulation through a mechanism involving protein kinase C signaling. We also showed that murine APOBEC2 expression in HEK293T cells led to a 10-fold reduction in intracellular plasmid levels and plasmid-encoded mRNA, and a 2.6-fold reduction in GFP-expressing cells. A bicistronic DNA vaccine expressing an immunogen and an APOBEC2-specific shRNA efficiently silenced APOBEC2 both in vitro and in vivo, increasing the frequency of induced IFN-γ-secreting T cells. Our study brings new insights into the intracellular machinery involved in dsDNA sensing and how to modulate it to improve DNA vaccine immunogenicity in humans.

Antihelminthic niclosamide modulates dendritic cells activation and function

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Effect of niclosamide on the activation of LPS-stimulated BMDCs was investigated.

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Niclosamide decreased ability to stimulate antigen specific T cell proliferation.

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Niclosamide attenuated hapten induced contact hypersensitivity (CHS) in vivo.

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Blocking the MAPK and NF-κB contribute to the inhibitory effect of niclosamide.

Dendritic cells (DCs) link the sensing of the environment by the innate immune system to the initiation of adaptive immune responses. Accordingly, DCs are considered to be a major target in the development of immunomodulating compounds. In this study, the effect of niclosamide, a Food and Drug Administration-approved antihelminthic drug, on the activation of lipopolysaccharide (LPS)-stimulated murine bone marrow-derived DCs was examined. Our experimental results show that niclosamide reduced the pro-inflammatory cytokine and chemokine expression of LPS-activated DCs. In addition, niclosamide also affected the expression of MHC and costimulatory molecules and influenced the ability of the cells to take up antigens. Therefore, in mixed cell cultures composed of syngeneic OVA-specific T cells and DCs, niclosamide-treated DCs showed a decreased ability to stimulate T cell proliferation and IFN-γ production. Furthermore, intravenous injection of niclosamide also attenuated contact hypersensitivity (CHS) in mice during sensitization with 2,4-dinitro-1-fluorobenzene. Blocking the LPS-induced activation of MAPK-ERK, JNK and NF-κB may contribute to the inhibitory effect of niclosamide on DC activation. Collectively, our findings suggest that niclosamide can manipulate the function of DCs. These results provide new insight into the immunopharmacological role of niclosamide and suggest that it may be useful for the treatment of chronic inflammatory disorders or DC-mediated autoimmune diseases.

Clitocybe nuda Activates Dendritic Cells and Acts as a DNA Vaccine Adjuvant

This work represents the first evaluation of the effects of water extract of C. nuda (WE-CN), an edible mushroom, on murine bone marrow-derived dendritic cells (BMDCs) and the potential pathway through which the effects are mediated. Our experimental results show that WE-CN could induce phenotypic maturation of DCs, as shown by the increased expression of MHC and costimulatory molecules. In addition, it also induced the proinflammatory cytokines expression on DCs and enhanced both the proliferation and IFN- γ secretion of allogenic T cells. Therefore, since WE-CN did not induce maturation of DCs generated from mice with mutated TLR-4 or TLR-2, suggesting that TLR4 and TLR2 might function as membrane receptors for WE-CN. Moreover, the mechanism of action of WE-CN may be mediated by increased phosphorylation of ERK, p38, and JNK mitogen-activated protein kinase (MAPK) and increased NF- κ B p65 activity, which are important signaling molecules downstream of TLR-4 and TLR-2. Finally, coimmunization of mice with WE-CN and a HER-2/neu DNA vaccine induced a HER-2/neu-specific Th1 response that resulted in significant inhibition of HER-2/neu overexpressing mouse bladder tumor (MBT-2) growth. These data suggest that WE-CN induces DC maturation through TLR-4 and/or TLR-2 and that WE-CN can be used as an adjuvant in cancer vaccine immunotherapy.

Dextromethorphan inhibits activations and functions in dendritic cells

Dendritic cells (DCs) play an important role in connecting innate and adaptive immunity. Thus, DCs have been regarded as a major target for the development of immunomodulators. In this study, we examined the effect of dextromethorphan (DXM), a common cough suppressant with a high safety profile, on the activation and function of DCs. In the presence of DXM, the LPS-induced expression of the costimulatory molecules in murine bone marrow-derived dendritic cells (BMDCs) was significantly suppressed. In addition, DXM treatment reduced the production of reactive oxygen species (ROS), proinflammatory cytokines, and chemokines in maturing BMDCs that were activated by LPS. Therefore, DXM abrogated the ability of LPS-stimulated DCs to induce Ag-specific T-cell activation, as determined by their decreased proliferation and IFN-γ secretion in mixed leukocyte cultures. Moreover, the inhibition of LPS-induced MAPK activation and NF-κB translocation may contribute to the suppressive effect of DXM on BMDCs. Remarkably, DXM decreased the LPS-induced surface expression of CD80, CD83, and HLA-DR and the secretion of IL-6 and IL-12 in human monocyte-derived dendritic cells (MDDCs). These findings provide a new insight into the impact of DXM treatment on DCs and suggest that DXM has the potential to be used in treating DC-related acute and chronic diseases.

An HDAC inhibitor enhances cancer therapeutic efficiency of RNA polymerase III promoter-driven IDO shRNA

Histone deacetylase (HDAC) inhibitors are used in treating certain human malignancies. Our laboratories demonstrated their capability in enhancing antitumor effect of DNA vaccine driven by an RNA polymerase II (RNA pol II) promoter. However, it is unknown whether HDAC inhibitors enhance the therapeutic short hairpin RNA (shRNA) expressed by an RNA polymerase III (RNA pol III) promoter. We investigated whether HDAC inhibitors augmented antitumor effect of indoleamine 2,3 dioxygenase (IDO) shRNA. HDAC inhibitor OSU-HDAC42 and suberoylanilide hydroxamic acid enhanced RNA pol III-driven U6 and H1 promoter activity in three different cell types in vitro: 293, NIH3T3 and dendritic cell line DC2.4. Subcutaneous injection of OSU-HDAC42 enhanced U6 and H1 promoter activity on abdominal skin of mice in vivo. Combination of IDO shRNA and OSU-HDAC42 increased antitumor effect of IDO shRNA in MBT-2 murine bladder tumor model. IDO shRNA induced tumor-infiltrating CD8⁺ and CD4⁺ T cells, whereas OSU-HDAC42 treatment induced tumor-infiltrating CD4⁺ T cells. Combination of OSU-HDAC42 and IDO shRNA further induced tumor-infiltrating natural killer cells and enhanced interferon-γ in lymphocytes, but suppressed interleukin (IL)-4 expression of lymphocytes. In addition, OSU-HDAC42 treatment did not alter mRNA expression of IL-12 and tumor necrosis factor-α. In conclusion, HDAC inhibitor OSU-HDAC42 may serve as adjuvant of the therapeutic shRNA expressed by an RNA pol III promoter.

miR-451 regulates dendritic cell cytokine responses to influenza infection

MicroRNAs (miRNAs) are important posttranscriptional regulators in immune cells, but how viral infection regulates miRNA expression to shape dendritic cell (DC) responses has not been well characterized. We identified 20 miRNAs that were differentially expressed in primary murine DCs in response to the dsRNA agonist polyinosinic-polycytidylic acid, a subset of which were modestly regulated by influenza infection. miR-451 was unique because it was induced more strongly in primary splenic and lung DCs by live viral infection than by purified agonists of pattern recognition receptors. We determined that miR-451 regulates a subset of proinflammatory cytokine responses. Three types of primary DCs treated with antisense RNA antagomirs directed against miR-451 secreted elevated levels of IL-6, TNF, CCL5/RANTES, and CCL3/MIP1α, and these results were confirmed using miR-451(null) cells. miR-451 negatively regulates YWHAZ/14-3-3ζ protein levels in various cell types, and we measured a similar inhibition of YWHAZ levels in DCs. It is known that YWHAZ can control the activity of two negative regulators of cytokine production: FOXO3, which is an inhibitory transcription factor, and ZFP36/Tristetraprolin, which binds to AU-rich elements within 3'-untranslated regions to destabilize cytokine mRNAs. Inhibition of miR-451 expression correlated with increased YWHAZ protein expression and decreased ZFP36 expression, providing a possible mechanism for the elevated secretion of IL-6, TNF, CCL5/RANTES, and CCL3/MIP1α. miR-451 levels are themselves increased by IL-6 and type I IFN, potentially forming a regulatory loop. These data suggest that viral infection specifically induces a miRNA that directs a negative regulatory cascade to tune DC cytokine production.

A FOXO3-IRF7 gene regulatory circuit limits inflammatory sequelae of antiviral responses

Antiviral responses must be tightly regulated to rapidly defend against infection while minimizing inflammatory damage. Type 1 interferons (IFN-I) are crucial mediators of antiviral responses¹ and their transcription is regulated by a variety of transcription factors²; principal amongst these is the family of interferon regulatory factors (IRFs)³. The IRF gene regulatory networks are complex and contain multiple feedback loops. The tools of systems biology are well suited to elucidate the complex interactions that give rise to precise coordination of the interferon response. Here we have used an unbiased systems approach to predict that a member of the forkhead family of transcription factors, FOXO3, is a negative regulator of a subset of antiviral genes. This prediction was validated using macrophages isolated from Foxo3-null mice. Genome-wide location analysis combined with gene deletion studies identified the Irf7 gene as a critical target of FOXO3. FOXO3 was identified as a negative regulator of Irf7 transcription and we have further demonstrated that FOXO3, IRF7 and IFN-I form a coherent feed-forward regulatory circuit. Our data suggest that the FOXO3-IRF7 regulatory circuit represents a novel mechanism for establishing the requisite set points in the interferon pathway that balances the beneficial effects and deleterious sequelae of the antiviral response.

The future of human DNA vaccines

DNA vaccines have evolved greatly over the last 20 years since their invention, but have yet to become a competitive alternative to conventional protein or carbohydrate based human vaccines. Whilst safety concerns were an initial barrier, the Achilles heel of DNA vaccines remains their poor immunogenicity when compared to protein vaccines. A wide variety of strategies have been developed to optimize DNA vaccine immunogenicity, including codon optimization, genetic adjuvants, electroporation and sophisticated prime-boost regimens, with each of these methods having its advantages and limitations. Whilst each of these methods has contributed to incremental improvements in DNA vaccine efficacy, more is still needed if human DNA vaccines are to succeed commercially. This review foresees a final breakthrough in human DNA vaccines will come from application of the latest cutting-edge technologies, including "epigenetics" and "omics" approaches, alongside traditional techniques to improve immunogenicity such as adjuvants and electroporation, thereby overcoming the current limitations of DNA vaccines in humans.

MMP-9 increases HER2/neu expression and alters apoptosis levels in human mammary epithelial cells (HMEC)

HER2/neu overexpression leads to poorer prognosis and higher risk of disease reoccurrence in breast cancer patients. The causative factors responsible for increasing HER2/neu expression levels on mammary cells are not known. We investigated whether factors associated with inflammation or metastasis could induce HER2/neu expression on human mammary epithelial cells (HMECs). Human mammary epithelial cells and several human breast cancer cell lines used in our studies were treated with several agents, including estrogen and matrix metalloproteinase-9 (MMP-9), either alone or in various combinations. Relative expression of HER2/neu on the surface of target cells was assessed using fluorochrome-tagged antibodies and a fluorescence cytometer. HER2/neu gene expression was also determined by Western blot analysis and PCR. Apoptosis levels were also determined. MMP-9, administered either alone or in combination with interleukin-7 and estrogen, caused a significant rise in HER2/neu expression on the surface of HMECs. The induction in HER2/neu protein expression was suppressed using a MMP-9 inhibitor. Similar results were obtained for breast cancer cells treated with the estrogen in combination with MMP-9. MMP-9 treatment significantly decreased apoptotic levels in HMECs. Our results indicate that MMP-9 is a regulator of HER2/neu expression on human mammary epithelial cells and suggest that upregulation of HER2/neu by MMP-9 may be relevant to altering the characteristics of normal mammary cells toward a transformed phenotype.