Inhibition of cervical cancer cell growth in vitro and in vivo with lentiviral-vector delivered short hairpin RNA targeting human papillomavirus E6 and E7 oncogenes

Resolution of oncogene-induced senescence markers in HPV-infected cervical cancer tissue

BACKGROUND

Oncogene-Induced Senescence (OIS) is a form of senescence that occurs as a consequence of oncogenic overstimulation and possibly infection by oncogenic viruses. Whether senescence plays a role in the pathogenesis of cervical cancer (CC) is not well understood. Moreover, whether cervical epithelial cells that are part of the premalignant cervical intraepithelial neoplasia (CIN), exhibit markers of OIS in Human Papillomavirus (HPV)-infected tissue, has not been investigated.

METHODS

We utilized a set of patient-derived premalignant and malignant tissue samples to investigate the protein (Ki67 and Lamin B1) and gene (TP53, IL1A, CCL2, and MMP9) expression of several OIS-associated biomarkers using immunohistochemistry (IHC) and qRT-PCR, respectively. Furthermore, we characterized the HPV status of all tissue samples.

RESULTS

Most of the CC samples (34/37) were positive for HPV, mainly HPV-16 which was observed in 62.2% of the CC samples. Among CINs, HPV infection was found in 60.2% of the 32 samples with HPV-16 as the dominant genotype in 58.5% of the CINs. IHC analysis revealed a significant increase in the expression levels of both Ki67 and Lamin B1 proteins in CC tissue compared to CIN. On average, 93% of tumor cells were positive for Ki67 in comparison to only 25% of premalignant cells in CIN samples. Similarly, Lamin B1 expression was observed in 89% of tumor cells in malignant tissue on average, compared to 60% in CIN samples. Importantly, Lamin B1 expression was elevated in nonmalignant cervical tissue suggesting that its downregulation is more predominant in the premalignant state. Furthermore, RT-PCR revealed a significant decrease in the expression of TP53, IL1a, CCL2, and MMP9 markers in CC samples compared to CINs. Specifically, 84% of CC samples showed reduced TP53 expression, 90% showed reduced IL1a expression, 74% showed reduced CCL2 expression, and 76% showed reduced MMP9 expression when compared with their premalignant baseline. Infection of HPV was confirmed in 61% of the tumor tissues while only 25% of the CINs were positive for HPV.

CONCLUSION

This work shall provide an opportunity to further examine the role of OIS in the process of HPV-driven CC development.

Genome-Wide Analysis of p53 Targets Reveals SCN2A as a Novel Player in p53-Induced Cell Arrest in HPV-Positive Cells

The host transcription factor p53 is a critical tumor suppressor in HPV-induced carcinogenesis, regulating target genes involved in cell cycle arrest and apoptosis. However, the p53 targets have not been thoroughly analyzed in HPV-infected cells. In this study, p53 signaling in HPV16 and HPV18 cells was activated by depleting the viral oncoprotein E6. Subsequently, p53-regulated genes were identified by comparing them with genes altered in p53-silenced cells. True p53 targets were defined as genes with at least one overlapping p53 binding site and ChIP peak near their locus. Our analysis revealed that while some p53 targets were common to both the HPV16 and HPV18 cells, the majority of the targets differed between these two types, potentially contributing to the varying prevalence of HPV16 and HPV18 in cervical cancer. Additionally, we identified SCN2A as a novel p53 target involved in p53-induced cell cycle arrest in HPV-related carcinogenesis. This study provides new insights into the mechanisms by which p53 inhibits HPV-induced carcinogenesis.

Evaluation of the anti-cancer efficacy of lipid nanoparticles containing siRNA against HPV16 E6/E7 combined with cisplatin in a xenograft model of cervical cancer

OBJECTIVE

To investigate the anti-cancer efficacy of ENB101-LNP, an ionizable lipid nanoparticles (LNPs) encapsulating siRNA against E6/E7 of HPV 16, in combination therapy with cisplatin in cervical cancer in vitro and in vivo.

METHODS

CaSki cells were treated with ENB101-LNP, cisplatin, or combination. Cell viability assessed the cytotoxicity of the treatment. HPV16 E6/E7 gene knockdown was verified with RT-PCR both in vitro and in vivo. HLA class I and PD-L1 were checked by flow cytometry. A xenograft model was made using CaSki cells in BALB/c nude mice. To evaluate anticancer efficacy, mice were grouped. ENB101-LNP was given three times weekly for 3 weeks intravenously, and cisplatin was given once weekly intraperitoneally. Tumor growth was monitored. On day 25, mice were euthanized; tumors were collected, weighed, and imaged. Tumor samples were analyzed through histopathology, immunostaining, and western blot.

RESULTS

ENB101-LNP and cisplatin synergistically inhibit CaSki cell growth. The combination reduces HPV 16 E6/E7 mRNA and boosts p21 mRNA, p53, p21, and HLA class I proteins. In mice, the treatment significantly blocked tumor growth and promoted apoptosis. Tumor inhibition rates were 29.7% (1 mpk ENB101-LNP), 29.6% (3 mpk), 34.0% (cisplatin), 47.0% (1 mpk ENB101-LNP-cisplatin), and 68.8% (3 mpk ENB101-LNP-cisplatin). RT-PCR confirmed up to 80% knockdown of HPV16 E6/E7 in the ENB101-LNP groups. Immunohistochemistry revealed increased p53, p21, and HLA-A expression with ENB101-LNP treatments, alone or combined.

CONCLUSION

The combination of ENB101-LNP, which inhibits E6/E7 of HPV 16, with cisplatin, demonstrated significant anticancer activity in the xenograft mouse model of cervical cancer.

Optimal delivery of RNA interference by viral vectors for cancer therapy

In recent years, there has been a surge in the innovative modification and application of the viral vector-based gene therapy field. Significant and consistent improvements in the engineering, delivery, and safety of viral vectors have set the stage for their application as RNA interference (RNAi) delivery tools. Viral vector-based delivery of RNAi has made remarkable breakthroughs in the treatment of several debilitating diseases and disorders (e.g., neurological diseases); however, their novelty has yet to be fully applied and utilized for the treatment of cancer. This review highlights the most promising and emerging viral vector delivery tools for RNAi therapeutics while discussing the variables limiting their success and suitability for cancer therapy. Specifically, we outline different integrating and non-integrating viral platforms used for gene delivery, currently employed RNAi targets for anti-cancer effect, and various strategies used to optimize the safety and efficacy of these RNAi therapeutics. Most importantly, we provide great insight into what challenges exist in their application as cancer therapeutics and how these challenges can be effectively navigated to advance the field.

Human papillomavirus in the setting of immunodeficiency: Pathogenesis and the emergence of next-generation therapies to reduce the high associated cancer risk

Human papillomavirus (HPV), a common sexually transmitted virus infecting mucosal or cutaneous stratified epithelia, is implicated in the rising of associated cancers worldwide. While HPV infection can be cleared by an adequate immune response, immunocompromised individuals can develop persistent, treatment-refractory, and progressive disease. Primary immunodeficiencies (PIDs) associated with HPV-related disease include inborn errors of GATA, EVER1/2, and CXCR4 mutations, resulting in defective cellular function. People living with secondary immunodeficiency (e.g. solid-organ transplants recipients of immunosuppression) and acquired immunodeficiency (e.g. concurrent human immunodeficiency virus (HIV) infection) are also at significant risk of HPV-related disease. Immunocompromised people are highly susceptible to the development of cutaneous and mucosal warts, and cervical, anogenital and oropharyngeal carcinomas. The specific mechanisms underlying high-risk HPV-driven cancer development in immunocompromised hosts are not well understood. Current treatments for HPV-related cancers include surgery with adjuvant chemotherapy and/or radiotherapy, with clinical trials underway to investigate the use of anti-PD-1 therapy. In the setting of HIV co-infection, persistent high-grade anal intraepithelial neoplasia can occur despite suppressive antiretroviral therapy, resulting in an ongoing risk for transformation to overt malignancy. Although therapeutic vaccines against HPV are under development, the efficacy of these in the setting of PID, secondary- or acquired- immunodeficiencies remains unclear. RNA-based therapeutic targeting of the HPV genome or mRNA transcript has become a promising next-generation therapeutic avenue. In this review, we summarise the current understanding of HPV pathogenesis, immune evasion, and malignant transformation, with a focus on key PIDs, secondary immunodeficiencies, and HIV infection. Current management and vaccine regimes are outlined in relation to HPV-driven cancer, and specifically, the need for more effective therapeutic strategies for immunocompromised hosts. The recent advances in RNA-based gene targeting including CRISPR and short interfering RNA (siRNA), and the potential application to HPV infection are of great interest. An increased understanding of both the dysregulated immune responses in immunocompromised hosts and of viral persistence is essential for the design of next-generation therapies to eliminate HPV persistence and cancer development in the most at-risk populations.

Senolytic Therapy: A Potential Approach for the Elimination of Oncogene-Induced Senescent HPV-Positive Cells

Senescence represents a unique cellular stress response characterized by a stable growth arrest, macromolecular alterations, and wide spectrum changes in gene expression. Classically, senescence is the end-product of progressive telomeric attrition resulting from the repetitive division of somatic cells. In addition, senescent cells accumulate in premalignant lesions, in part, as a product of oncogene hyperactivation, reflecting one element of the tumor suppressive function of senescence. Oncogenic processes that induce senescence include overexpression/hyperactivation of H-Ras, B-Raf, and cyclin E as well as inactivation of PTEN. Oncogenic viruses, such as Human Papilloma Virus (HPV), have also been shown to induce senescence. High-risk strains of HPV drive the immortalization, and hence transformation, of cervical epithelial cells via several mechanisms, but primarily via deregulation of the cell cycle, and possibly, by facilitating escape from senescence. Despite the wide and successful utilization of HPV vaccines in reducing the incidence of cervical cancer, this measure is not effective in preventing cancer development in individuals already positive for HPV. Accordingly, in this commentary, we focus on the potential contribution of oncogene and HPV-induced senescence (OIS) in cervical cancer. We further consider the potential utility of senolytic agents for the elimination of HPV-harboring senescent cells as a strategy for reducing HPV-driven transformation and the risk of cervical cancer development.

Repositioning Fenofibrate to Reactivate p53 and Reprogram the Tumor-Immune Microenvironment in HPV+ Head and Neck Squamous Cell Carcinoma

Simple Summary

A critical need for optimal management of human papillomavirus-associated head and neck squamous cell carcinoma (HPV+ HNSCC) patients is the development of therapeutic strategies to exploit the inherent vulnerabilities of this unique disease. We identified fenofibrate, an FDA-approved drug, as a potent anti-cancer agent for HPV+ HNSCC. Fenofibrate induced the accumulation of the p53 tumor suppressor and re-programmed the tumor microenvironment to drive immune cell infiltration. We provide compelling evidence to reposition fenofibrate as a single agent or in combination with standard therapies for the HPV+ HNSCC setting.

Abstract

Human papillomavirus-associated head and neck squamous cell carcinoma (HPV+ HNSCC) is recognized as a distinct disease with unique etiology and clinical features. Current standard of care therapeutic modalities are identical for HPV+ and HPV− HNSCC and thus, there remains an opportunity to develop innovative pharmacologic approaches to exploit the inherent vulnerabilities of HPV+ HNSCC. In this study, using an inducible HPVE6E7 knockdown system, we found that HPV+ HNSCC cells are addicted to HPVE6E7, such that loss of these viral oncogenes impaired tumorigenicity in vitro and in vivo. A number of druggable pathways, including PPAR and Wnt, were modulated in response to HPVE6E7 loss. Fenofibrate showed significant anti-proliferative effects in a panel of HPV+ cancer cell lines. Additionally, fenofibrate impaired tumor growth as monotherapy and potentiated the activity of cisplatin in a pre-clinical HPV+ animal model. Systemic fenofibrate treatment induced p53 protein accumulation, and surprisingly, re-programmed the tumor-immune microenvironment to drive immune cell infiltration. Since fenofibrate is FDA-approved with a favorable long-term safety record, repositioning of this drug, as a single agent or in combination with cisplatin or checkpoint blockade, for the HPV+ HNSCC setting should be prioritized.

RNA-based gene targeting therapies for human papillomavirus driven cancers

While platinum-based chemotherapy, radiation therapy and or surgery are effective in reducing human papillomavirus (HPV) driven cancer tumours, they have some significant drawbacks, including low specificity for tumour, toxicity, and severe adverse effects. Though current therapies for HPV-driven cancers are effective, severe late toxicity associated with current treatments contributes to the deterioration of patient quality of life. This warrants the need for novel therapies for HPV derived cancers. In this short review, we examined RNA-based therapies targeting the major HPV oncogenes, including short-interfering RNAs (siRNAs) and clustered regularly interspaced short palindromic repeats (CRISPR) as putative treatment modalities. We also explore other potential RNA-based targeting approaches such as microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and mRNA vaccines as future treatment modalities for HPV cancers. Some of these technologies have already been approved for clinical use for a range of other human diseases but not for HPV cancers. Here we explore the emerging evidence supporting the effectiveness of some of these gene-based therapies for HPV malignancies. In short, the evidence sheds promising light on the feasibility of translating these technologies into a clinically relevant treatment modality for HPV derived cancers and potentially other virally driven human cancers.

HPVE6-USP46 Mediated Cdt2 Stabilization Reduces Set8 Mediated H4K20-Methylation to Induce Gene Expression Changes

E6 from high-risk strains of HPV is well known to transform cells by deregulating p53. We reported that in HPV transformed cell-lines E6 from high-risk HPV can recruit the USP46 deubiquitinase to substrates such as Cdt2 and stabilize the latter, and that USP46 is important for growth of HPV induced tumors in xenografts. Here we show that in cervical cancer biopsies the stabilization of Cdt2 in the HPV-induced cancers leads to the decrease of a CRL4-Cdt2 substrate, the histone H4K20 mono-methyltransferase Set8, and decrease in H4K20me1 or H4K20me3 that can be detected by immunohistochemistry. In HPV-transformed cancer cell lines in vitro, knockdown of E6 decreases Cdt2 and increases Set8. Co-knockdown of Set8 shows that some of the gene expression changes produced by E6 knockdown is due to the increase of Set8. EGFR and EGFR regulated genes were identified in this set of genes. Turning to the mechanism by which E6 stabilizes Cdt2, we find that a purified E6:USP46 complex has significantly more de-ubiquitinase activity in vitro than USP46 alone, demonstrating that E6 can directly interact with USP46 in the absence of other proteins and that it can substitute for the known activators of USP46, UAF1 and WDR20. Deletion mapping of Cdt2 shows that there are three discrete, but redundant, parts of the substrate that are essential for stabilization by E6: USP46. The helix-loop-helix region or the WD40 repeat driven beta-propeller structure of Cdt2 are dispensable for the stabilization implying that interaction with DDB1 (and the rest of the CRL4 complex) or with the substrate of the CRL4-Cdt2 E3 ligase is not necessary for E6:USP46 to interact with and stabilize Cdt2. The identification of 50 amino acid stretches in the 731 amino acid Cdt2 protein as being important for the stabilization by E6 underlines the specificity of the process. In summary, E6 activates the deubiquitinase activity of USP46, stabilizes Cdt2 utilizing multiple sites on Cdt2, and leads to degradation of Set8 and changes in gene-expression in HPV-transformed cells.

MAGT1 is required for HeLa cell proliferation through regulating p21 expression, S-phase progress, and ERK/p38 MAPK MYC axis

Magnesium transporter subtype 1 (MAGT1) is known to participate in animal development and cell differentiation. Thus far, MAGT1 studies have mainly focused on its role in cardiomyocyte regulation and differentiation; only a few studies have demonstrated its role in cell proliferation. To investigate the underlying mechanism of MAGT1 in cell proliferation, HeLa and SiHa cells were transiently knocked down with different siRNAs. We showed that cell proliferation was substantially restricted by S-phase arrest and apoptosis in the MAGT1-knocked down cells, which was further confirmed by the increased expression of p21, cyclin-A1, and cyclin-B1, as well as the decreased expression of MYC, cyclin-D1, cyclin-E1, and CDK2. MAGT1 knockdown also resulted in significant changes in the transcriptional expression of 1,598 genes that were analyzed by RNA sequencing. Bioinformatics analysis showed that MAGT1 was related to the MAPK signaling pathway. Western blot analysis confirmed that the phosphorylation of extracellular signal-related protein kinase 1/2 (ERK1/2) and p38 was remarkably reduced in MAGT1 down-regulated groups. Additionally, MAGT1 was required for the function of viral proteins E6/E7 during cell proliferation and G1/S cell-cycle progression. Therefore, MAGT1 plays a crucial role in the proliferation of HPV-positive cervical cancer cells, S-phase progression, and the ERK/p38 MAPK signaling pathway. These results indicate the potential of MAGT1 as a novel target for anticancer research.Abbreviations: MAGT1: Magnesium transporter subtype 1; MAPK: Mitogen-activated protein kinase; XMEN: X-linked immunodeficiency with Magnesium defect, Epstein-Barr virus infection and Neoplasia; BMMSCs: Bone Marrow Mesenchymal Stem Cells; Dpp: Decapentaplegic; CDKIs: CDK inhibitors; GPCR: G-protein coupled receptor; GO: Gene Ontology; KEGG: Kyoto Encyclopedia of Genes and Genomes; RTK: Receptor Tyrosine Kinase; PTK: Protein Tyrosine Kinase; FGFR: Fibroblast Growth Factor Receptor; BMP: Bone Morphogenetic Protein; HPV18 E6/E7: Human Papillomavirus 18 Early protein 6/ early protein 7; FACS: Fluorescence Activated Cell Sorting; PI: Propidium Iodide.

Immunotherapy and Gene Therapy for Oncoviruses Infections: A Review

Immunotherapy has been shown to be highly effective in some types of cancer caused by viruses. Gene therapy involves insertion or modification of a therapeutic gene, to correct for inappropriate gene products that cause/may cause diseases. Both these types of therapy have been used as alternative ways to avoid cancers caused by oncoviruses. In this review, we summarize recent studies on immunotherapy and gene therapy including the topics of oncolytic immunotherapy, immune checkpoint inhibitors, gene replacement, antisense oligonucleotides, RNA interference, clustered regularly interspaced short palindromic repeats Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-based gene editing, transcription activator-like effector nucleases (TALENs) and custom treatment for Epstein-Barr virus, human T-lymphotropic virus 1, hepatitis B virus, human papillomavirus, hepatitis C virus, herpesvirus associated with Kaposi's sarcoma, Merkel cell polyomavirus, and cytomegalovirus.

IRF-1 Inhibits Angiogenic Activity of HPV16 E6 Oncoprotein in Cervical Cancer

HPV16 E6 oncoprotein is a member of the human papillomavirus (HPV) family that contributes to enhanced cellular proliferation and risk of cervical cancer progression via viral infection. In this study, interferon regulatory factor-1 (IRF-1) regulates cell growth inhibition and transcription factors in immune response, and acts as an HPV16 E6-binding cellular molecule. Over-expression of HPV16 E6 elevated cell growth by attenuating IRF-1-induced apoptosis and repressing p21 and p53 expression, but activating cyclin D1 and nuclear factor kappa B (NF-κB) expression. The promoter activities of p21 and p53 were suppressed, whereas NF-κB activities were increased by HPV16 E6. Additionally, the cell viability of HPV16 E6 was diminished by IRF-1 in a dose-dependent manner. We found that HPV16 E6 activated vascular endothelial growth factor (VEGF)-induced endothelial cell migration and proliferation as well as phosphorylation of VEGFR-2 via direct interaction in vitro. HPV16 E6 exhibited potent pro-angiogenic activity and clearly enhanced the levels of hypoxia-inducible factor-1α (HIF-1α). By contrast, the loss of function of HPV16 E6 by siRNA-mediated knockdown inhibited the cellular events. These data provide direct evidence that HPV16 E6 facilitates tumour growth and angiogenesis. HPV16 E6 also activates the PI3K/mTOR signalling cascades, and IRF-1 suppresses HPV16 E6-induced tumourigenesis and angiogenesis. Collectively, these findings suggest a biological mechanism underlying the HPV16 E6-related activity in cervical tumourigenesis.

Mdm2-P53 Interaction Inhibitor with Cisplatin Enhances Apoptosis in Colon and Prostate Cancer Cells In-Vitro

OBJECTIVE

To study the effect of RITA (MDM2-p53 interaction inhibitor) and its action along with genotoxic drug cisplatin was evaluated on COLO-205 colon cancer and PC-3 prostate cancer cells.

METHOD

Various in-vitro parameters to determine cytotoxic and apoptotic potential of RITA with genotoxic drug cisplatin were evaluated. The potentiation of cytotoxic effect was evaluated using MTT assay and colony forming assay, mechanism of cell death by Etbr/AcO assay and the mechanism of apoptosis was determined by caspase-3 release assay.

RESULTS

The findings from MTT confirmed the best possible potent combination of 5+5µM and 10+10µM concentration of Cisplatin and RITA respectively. These combinations were further evaluated for its chemo sensitizing effect which confirmed the significant reduction in number of colonies in combination as compared to monotherapy. Also, the results of Etbr/AcO assay were in line with the colony forming assay. For apoptotic activity, it was noted that increasing the concentration of cisplatin and RITA (10µM), did not affect much to apoptotic activity and was found to be equally effective to that of low dose (5µM) concentration. The same results were seen in Caspase-3 release effect on both the cell lines.

CONCLUSION

Our present study provides compelling evidence that pharmacological activation of the p53 by blocking the MDM2-p53 interaction is a promising cancer therapeutic strategy and using RITA in combination with Cisplatin not only decrease the toxic effect of Cisplatin by decreasing its dose but also increasing the apoptotic effect, warrants clinical evaluation on both colon and prostate cancer.

Tissue-Specific Gene Expression during Productive Human Papillomavirus 16 Infection of Cervical, Foreskin, and Tonsil Epithelium

Epidemiological data confirm a much higher incidence of high-risk human papillomavirus 16 (HPV16)-mediated carcinogenesis of the cervical epithelium than for other target sites. In order to elucidate tissue-specific responses to virus infection, we compared gene expression changes induced by productive HPV16 infection of cervical, foreskin, and tonsil organotypic rafts. These rafts closely mimic persistent HPV16 infection, long before carcinogenesis sets in. The total number of gene expression changes varied considerably across the tissue types, with only 32 genes being regulated in common. Among them, we confirmed the Kelch-like family protein KLHL35 and the laminin-5 complex to be upregulated and downregulated, respectively, in all the three tissues. HPV16 infection induces upregulation of genes involved in cell cycle control, cell division, mitosis, DNA replication, and DNA damage repair in all the three tissues, indicative of a hyperproliferative environment. In the cervical and tonsil epithelium, we observe significant downregulation of genes involved in epidermis development, keratinocyte differentiation, and extracellular matrix organization. On the other hand, in HPV16-positive foreskin (HPV16 foreskin) tissue, several genes involved in interferon-mediated innate immunity, cytokine signaling, and cellular defenses were downregulated. Furthermore, pathway analysis and experimental validations identified important cellular pathways like STAT1 and transforming growth factor β (TGF-β) to be differentially regulated among the three tissue types. The differential modulation of important cellular pathways like TGF-β1 and STAT1 can explain the sensitivity of tissues to HPV cancer progression.IMPORTANCE Although the high-risk human papillomavirus 16 infects anogenital and oropharyngeal sites, the cervical epithelium has a unique vulnerability to progression of cancer. Host responses during persistent infection and preneoplastic stages can shape the outcome of cancer progression in a tissue-dependent manner. Our study for the first time reports differential regulation of critical cellular functions and signaling pathways during productive HPV16 infection of cervical, foreskin, and tonsil tissues. While the virus induces hyperproliferation in infected cells, it downregulates epithelial differentiation, epidermal development, and innate immune responses, according to the tissue type. Modulation of these biological functions can determine virus fitness and pathogenesis and illuminate key cellular mechanisms that the virus employs to establish persistence and finally initiate disease progression.

Single-Domain Antibodies Represent Novel Alternatives to Monoclonal Antibodies as Targeting Agents against the Human Papillomavirus 16 E6 Protein

Approximately one fifth of all malignancies worldwide are etiologically associated with a persistent viral or bacterial infection. Thus, there is a particular interest in therapeutic molecules which use components of a natural immune response to specifically inhibit oncogenic microbial proteins, as it is anticipated they will elicit fewer off-target effects than conventional treatments. This concept has been explored in the context of human papillomavirus 16 (HPV16)-related cancers, through the development of monoclonal antibodies and fragments thereof against the viral E6 oncoprotein. Challenges related to the biology of E6 as well as the functional properties of the antibodies themselves appear to have precluded their clinical translation. Here, we addressed these issues by exploring the utility of the variable domains of camelid heavy-chain-only antibodies (denoted as VHHs). Through construction and panning of two llama, immune VHH phage display libraries, a pool of potential VHHs was isolated. The interactions of these with recombinant E6 were further characterized using an enzyme-linked immunosorbent assay (ELISA), Western blotting under denaturing and native conditions, and surface plasmon resonance. Three VHHs were identified that bound recombinant E6 with nanomolar affinities. Our results lead the way for subsequent studies into the ability of these novel molecules to inhibit HPV16-infected cells in vitro and in vivo.

Silencing PD-1 and PD-L1 with nanoparticle-delivered small interfering RNA increases cytotoxicity of tumor-infiltrating lymphocytes

AIM

To determine if silencing PD-1 on tumor-infiltrating lymphocytes (TILs) and its ligand-1 (PD-L1) on cancer cells will enhance the cytotoxicity of TILs.

MATERIALS & METHODS

Lipid-coated calcium phosphate nanoparticles were synthesized to deliver siRNAs against PD-1 and PD-L1 to TILs and breast cancer MCF-7 cells. The downregulation of PD-1/PD-L1 expressions was determined by real-time PCR and western blotting assays. The killing efficacy of TILs to MCF-7 cells was determined by cytotoxic T lymphocyte assay.

RESULTS

Lipid-coated calcium phosphate nanoparticles effectively delivered siRNAs and silenced PD-1 and PD-L1sh expression. The knockdown of either gene or both greatly improved the cytotoxicity of TILs.

CONCLUSION

Silencing PD-1 and PD-L1 is an effective approach to increase TIL cytotoxicity to cancer cells.

Cervical cancer cell lines are sensitive to sub-erythemal UV exposure

High risk human papillomavirus (HPV) infections are the causative agent in virtually every cervical cancer as well as a host of other anogenital and oropharyngeal malignancies. These viruses must activate DNA repair pathways to facilitate their replication, while avoiding the cell cycle arrest and apoptosis that can accompany DNA damage. HPV oncoproteins facilitate each of these goals, but also reduce genome stability. Our data dissect the cytotoxic and cytoprotective characteristics of HPV oncogenes in cervical cancer cells. These data show that while the transformation of keratinocytes by HPV oncogene leaves these cells more sensitive to UV, the oncogenes also protect against UV-induced apoptosis. Cisplatin and UV resistant cervical cancer cell lines were generated and probed for their sensitivity to genotoxic agents. Cervical cancer cells can acquire resistance to one DNA crosslinking agent (UV or cisplatin) without gaining broad tolerance of crosslinked DNA. Further, cisplatin resistance may or may not result in sensitivity to PARP1 inhibition.

Effect of Productive Human Papillomavirus 16 Infection on Global Gene Expression in Cervical Epithelium

Human papillomavirus (HPV) infection is the world's most common sexually transmitted infection and is responsible for most cases of cervical cancer. Previous studies of global gene expression changes induced by HPV infection have focused on the cancerous stages of infection, and therefore, not much is known about global gene expression changes at early preneoplastic stages of infection. We show for the first time the global gene expression changes during early-stage HPV16 infection in cervical tissue using 3-dimensional organotypic raft cultures, which produce high levels of progeny virions. cDNA microarray analysis showed that a total of 594 genes were upregulated and 651 genes were downregulated at least 1.5-fold with HPV16 infection. Gene ontology analysis showed that biological processes including cell cycle progression and DNA metabolism were upregulated, while skin development, immune response, and cell death were downregulated with HPV16 infection in cervical keratinocytes. Individual genes were selected for validation at the transcriptional and translational levels, including UBC, which was central to the protein association network of immune response genes, and top downregulated genes RPTN, SERPINB4, KRT23, and KLK8 In particular, KLK8 and SERPINB4 were shown to be upregulated in cancer, which contrasts with the gene regulation during the productive replication stage. Organotypic raft cultures, which allow full progression of the HPV life cycle, allowed us to identify novel gene modulations and potential therapeutic targets of early-stage HPV infection in cervical tissue. Additionally, our results suggest that early-stage productive infection and cancerous stages of infection are distinct disease states expressing different host transcriptomes.IMPORTANCE Persistent HPV infection is responsible for most cases of cervical cancer. The transition from precancerous to cancerous stages of HPV infection is marked by a significant reduction in virus production. Most global gene expression studies of HPV infection have focused on the cancerous stages. Therefore, little is known about global gene expression changes at precancerous stages. For the first time, we measured global gene expression changes at the precancerous stages of HPV16 infection in human cervical tissue producing high levels of virus. We identified a group of genes that are typically overexpressed in cancerous stages to be significantly downregulated at the precancerous stage. Moreover, we identified significantly modulated genes that have not yet been studied in the context of HPV infection. Studying the role of these genes in HPV infection will help us understand what drives the transition from precancerous to cancerous stages and may lead to the development of new therapeutic targets.

Aurora kinases are a novel therapeutic target for HPV-positive head and neck cancers

OBJECTIVES

Human papilloma virus (HPV) is the main culprit in cancers of the cervix, penis, anus, skin, eye and head and neck. Current treatments for HPV cancers have not altered survival outcomes for 30 years and there is a significant lack of targeted therapeutic agents in the management of advanced HPV-related HNSCC. Here we show that survival and maintenance of HPV-positive HNC cells relies on the continuous expression of the major HPV oncogene, E7, and that Aurora kinases are critical for survival of high-risk HPV-positive HNC cells.

MATERIALS AND METHODS

To assess the role of HPV E7 on HNC cell survival, RNA interference (RNAi) of the E7 gene was initially performed. Using an Aurora kinase inhibitor, Alisertib, the role of Aurora kinases in the carcinogenesis of HPV E7 positive HNC tumour lines was then investigated. An in vivo HNC xenograft model was also utilised to assess loss of tumour volume in response to RNAi E7 gene silencing and Alisertib treatment.

RESULTS

RNAi silencing of the HPV E7 gene inhibited the growth of HPV-positive HNC cells and in vivo tumour load. We show that HPV E7 oncogene expression confers sensitivity to Alisertib on HNC cells where Alisertib-mediated loss in in vitro cell viability and in vivo tumour load is dependent on E7 expression. Moreover, Aurora kinase inhibition induced degradation of MCL-1 in HPV E7-expressing HNC cells.

CONCLUSION

Overall, we show that Aurora kinases are a novel therapeutic target for HPV-positive HNCs. It might be feasible to combine Aurora kinase and MCL-1 inhibitors for future HNC therapies.

Roles of APOBEC3A and APOBEC3B in Human Papillomavirus Infection and Disease Progression

The apolipoprotein B messenger RNA-editing, enzyme-catalytic, polypeptide-like 3 (APOBEC3) family of cytidine deaminases plays an important role in the innate immune response to viral infections by editing viral genomes. However, the cytidine deaminase activity of APOBEC3 enzymes also induces somatic mutations in host genomes, which may drive cancer progression. Recent studies of human papillomavirus (HPV) infection and disease outcome highlight this duality. HPV infection is potently inhibited by one family member, APOBEC3A. Expression of APOBEC3A and APOBEC3B is highly elevated by the HPV oncoproteins E6 and E7 during persistent virus infection and disease progression. Furthermore, there is a high prevalence of APOBEC3A and APOBEC3B mutation signatures in HPV-associated cancers. These findings suggest that induction of an APOBEC3-mediated antiviral response during HPV infection may inadvertently contribute to cancer mutagenesis and virus evolution. Here, we discuss current understanding of APOBEC3A and APOBEC3B biology in HPV restriction, evolution, and associated cancer mutagenesis.

The Potential Value of the PI3K/Akt/mTOR Signaling Pathway for Assessing Prognosis in Cervical Cancer and as a Target for Therapy

Cervical cancer is a common gynecological cancer and a leading cause of cancer-related death in women globally. There is a need for the identification of prognostic and predictive biomarker for risk stratification. The phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/Akt/mTOR) pathway is often dysregulated in cervical cancer, indicating that it may be a potential therapeutic target in the treatment of this malignancy, and could perhaps be used as a novel biomarker in the assessment of risk of developing cervical cancer. We aimed to provide an overview of the potential applications of the PI3K/Akt/mTOR pathway as biomarker for risk stratification, in predicting the prognosis of cervical cancer, and for developing new therapeutic approaches in patients with cervical cancer. J. Cell. Biochem. 118: 4163-4169, 2017. © 2017 Wiley Periodicals, Inc.

The Therapeutic Potential of CRISPR/Cas9 Systems in Oncogene-Addicted Cancer Types: Virally Driven Cancers as a Model System

The field of gene editing is undergoing unprecedented growth. The first ex vivo human clinical trial in China started in 2016, more than 1000 US patents have been filed, and there is exponential growth in publications. The ability to edit genes with high fidelity is promising for the development of new treatments for a range of diseases, particularly inherited conditions, infectious diseases, and cancers. For cancer, a major issue is the identification of driver mutations and oncogenes to target for therapeutic effect, and this requires the development of robust models with which to prove their efficacy. The challenge is that there is rarely a single critical gene. However, virally driven cancers, in which cells are addicted to the expression of a single viral oncogene in some cases, may serve as model systems for CRISPR/Cas therapies, as they did for RNAi. These models and systems offer an excellent opportunity to test both preclinical models and clinical conditions to examine the effectiveness of gene editing, and here we review the options and offer a way forward.

Can gene editing and silencing technologies play a role in the treatment of head and neck cancer?

Conventional treatment strategies have done little to improve the prognosis or disease-free survival in head and neck cancer (HNC) patients. Recent progress in our understanding of molecular aspects of head and neck squamous cell carcinoma (HNSCC) has provided insights into the potential use of molecular targeted therapies in combination with current treatment strategies. Here we review the current understanding of treatment modalities for both HPV-positive and HPV-negative HNSCCs with the potential to use gene editing and silencing technologies therapeutically. The development of sequence-specific RNA interference (RNAi) with its strong gene-specific silencing ability, high target specificity, greater potency and reduced side effects, has shown it to be a promising therapeutic candidate for treating cancers. CRISPR/Cas gene editing is the newest technology with the ability to delete, mutate or replace genes of interest and has great potential for treating HNSCCs. We also discuss the major challenge in using these approaches in HNSCC; that being the choice of target and the ability to deliver the payload. Finally, we highlight the potential combination of RNAi or CRIPSR/Cas with current treatment strategies and outline the possible path to the clinic.

E6 and E7 gene silencing results in decreased methylation of tumor suppressor genes and induces phenotype transformation of human cervical carcinoma cell lines

In SiHa and CaSki cells, E6 and E7-targeting shRNA specifically and effectively knocked down human papillomavirus (HPV) 16 E6 and E7 at the transcriptional level, reduced the E6 and E7 mRNA levels by more than 80% compared with control cells that expressed a scrambled-sequence shRNA. E6 and E7 repression resulted in down-regulation of DNA methyltransferase mRNA and protein expression, decreased DNA methylation and increased mRNA expression levels of tumor suppressor genes, induced a certain apoptosis and inhibited proliferation in E6 and E7 shRNA-infected SiHa and CaSki cells compared with the uninfected cells. Repression of E6 and E7 oncogenes resulted in restoration of DNA methyltransferase suppressor pathways and induced apoptosis in HPV16-positive cervical carcinoma cell lines. Our findings suggest that the potential carcinogenic mechanism of HPV16 through influencing DNA methylation pathway to activate the development of cervical cancer exist, and maybe as a candidate therapeutic strategy for cervical and other HPV-associated cancers.

Gamma tocotrienol targets tyrosine phosphatase SHP2 in mammospheres resulting in cell death through RAS/ERK pathway

Background

There is increasing evidence supporting the concept of cancer stem cells (CSCs), which are responsible for the initiation, growth and metastasis of tumors. CSCs are thus considered the target for future cancer therapies. To achieve this goal, identifying potential therapeutic targets for CSCs is essential.

Methods

We used a natural product of vitamin E, gamma tocotrienol (gamma-T3), to treat mammospheres and spheres from colon and cervical cancers. Western blotting and real-time RT-PCR were employed to identify the gene and protein targets of gamma-T3 in mammospheres.

Results

We found that mammosphere growth was inhibited in a dose dependent manner, with total inhibition at high doses. Gamma-T3 also inhibited sphere growth in two other human epithelial cancers, colon and cervix. Our results suggested that both Src homology 2 domain-containing phosphatase 1 (SHP1) and 2 (SHP2) were affected by gamma-T3 which was accompanied by a decrease in K- and H-Ras gene expression and phosphorylated ERK protein levels in a dose dependent way. In contrast, expression of self-renewal genes TGF-beta and LIF, as well as ESR signal pathways were not affected by the treatment. These results suggest that gamma-T3 specifically targets SHP2 and the RAS/ERK signaling pathway.

Conclusions

SHP1 and SHP2 are potential therapeutic targets for breast CSCs and gamma-T3 is a promising natural drug for future breast cancer therapy.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1614-1) contains supplementary material, which is available to authorized users.

Human Papillomavirus E6/E7-Specific siRNA Potentiates the Effect of Radiotherapy for Cervical Cancer in Vitro and in Vivo

The functional inactivation of TP53 and Rb tumor suppressor proteins by the HPV-derived E6 and E7 oncoproteins is likely an important step in cervical carcinogenesis. We have previously shown siRNA technology to selectively silence both E6/E7 oncogenes and demonstrated that the synthetic siRNAs could specifically block its expression in HPV-positive cervical cancer cells. Herein, we investigated the potentiality of E6/E7 siRNA candidates as radiosensitizers of radiotherapy for the human cervical carcinomas. HeLa and SiHa cells were transfected with HPV E6/E7 siRNA; the combined cytotoxic effect of E6/E7 siRNA and radiation was assessed by using the cell viability assay, flow cytometric analysis and the senescence-associated β-galactosidase (SA-β-Gal) assay. In addition, we also investigated the effect of combined therapy with irradiation and E6/E7 siRNA intravenous injection in an in vivo xenograft model. Combination therapy with siRNA and irradiation efficiently retarded tumor growth in established tumors of human cervical cancer cell xenografted mice. In addition, the chemically-modified HPV16 and 18 E6/E7 pooled siRNA in combination with irradiation strongly inhibited the growth of cervical cancer cells. Our results indicated that simultaneous inhibition of HPV E6/E7 oncogene expression with radiotherapy can promote potent antitumor activity and radiosensitizing activity in human cervical carcinomas.

Human Papillomavirus: Current and Future RNAi Therapeutic Strategies for Cervical Cancer

Human papillomaviruses (HPVs) are small DNA viruses; some oncogenic ones can cause different types of cancer, in particular cervical cancer. HPV-associated carcinogenesis provides a classical model system for RNA interference (RNAi) based cancer therapies, because the viral oncogenes E6 and E7 that cause cervical cancer are expressed only in cancerous cells. Previous studies on the development of therapeutic RNAi facilitated the advancement of therapeutic siRNAs and demonstrated its versatility by siRNA-mediated depletion of single or multiple cellular/viral targets. Sequence-specific gene silencing using RNAi shows promise as a novel therapeutic approach for the treatment of a variety of diseases that currently lack effective treatments. However, siRNA-based targeting requires further validation of its efficacy in vitro and in vivo, for its potential off-target effects, and of the design of conventional therapies to be used in combination with siRNAs and their drug delivery vehicles. In this review we discuss what is currently known about HPV-associated carcinogenesis and the potential for combining siRNA with other treatment strategies for the development of future therapies. Finally, we present our assessment of the most promising path to the development of RNAi therapeutic strategies for clinical settings.

Construction and detection of the tissue-specific pINV-HPV16 E6/7 vector

A tissue-specific promoter can control downstream gene expression in tissues or organs. The human involucrin (hINV) promoter (pINV) that contains 2474 bp of hINV upstream sequence is able to regulate tissue-specific gene expression. This tissue specificity may be important for the prevention and treatment of human papilloma virus infections. pINV was cloned by polymerase chain reaction and the human papillomavirus (HPV)16 E6/7 gene was obtained from the cancer tissue samples of patients with cervical carcinoma at the Yangzhou Maternal and China Health-Care Center of Jinagsu Province (Yangzhou, China). First, specific primers were designed according to the genomic DNA sequence of the HPV16-type standard strain that has been reported and the E6/7 gene was acquired by PCR. The carcinogenic fraction of the E6/7 gene was removed and the remaining section was cloned into T vectors, sequenced correctly and then cloned into the eukaryotic expression vector pCEP4, which was lacking the CMV promoter. The positive recombinants were identified using blue-white screening and endonuclease digestion, subsequent to sequencing and analysis, and the tissue-specific recombinant pINV-HPV16E6/7 plasmids was detected.

Emerging drugs for the treatment of cervical cancer

INTRODUCTION

Worldwide, most cervical cancer (CC) patients require the use of drug therapy either adjuvant, concurrent with radiation or palliative.

AREAS COVERED

This review briefly discusses the current achievements in treating CC with an emphasis in emerging agents.

EXPERT OPINION

Concurrent cisplatin with radiation and lately, gemcitabine-cisplatin chemoradiation has resulted in small but significant improvements in the treatment of locally advanced and high-risk early-stage patients. So far, only antiangiogenic therapy with bevacizumab added to cisplatin chemoradiation has demonstrated safety and encouraging results in a Phase II study. In advanced disease, cisplatin doublets yield median survival rates not exceeding 14 months. The first Phase III study of bevacizumab, added to standard chemotherapy cisplatin- or non-cisplatin-containing doublet, has shown significant increase in both overall survival and progression-free survival. Further studies are needed before bevacizumab plus chemotherapy can be considered the standard of care for advanced disease. The characterization of the mutational landscape of CC and developments of novel targeted therapies may result in more effective and individualized treatments for CC. The potential efficacy of knocking down the key alterations in CC, E6 and E7 human papilloma virus oncoproteins must not be overlooked.

Silencing of E6/E7 expression in cervical cancer stem-like cells

Accumulating evidence supports the concept that cancer stem cells (CSCs) are responsible for the tumor recurrence and metastasis, the two major causes of cancer-related death. Therefore, CSC-targeted cancer therapy is important for the future development of more effective and advanced cancer therapy. One of the approaches is to specifically silence oncogene expression in CSCs and inhibit their growth. The significance of this approach is its specificity and ability to avoid multi-drug resistance of CSCs. In this chapter, we will describe a method of silencing HPV oncogenes E6/E7 in human cervical CSCs using HeLa cells as a model system.

New molecular targets against cervical cancer

Cervical cancer is the third most commonly diagnosed cancer worldwide and the fourth leading cause of cancer death in women. Major advances but still insufficient achievements in the treatment of locally advanced and high-risk early stage patients have occurred in the last decade with the incorporation of concurrent cisplatin with radiation and, lately, gemcitabine added to cisplatin chemoradiation. Despite a number of clinical studies incorporating molecular-targeted therapy as radiosensitizers being in progress, so far, only antiangiogenic therapy with bevacizumab added to cisplatin chemoradiation has demonstrated safety and shown encouraging results in a Phase II study. In advanced disease, cisplatin doublets do not have a great impact on the natural history of the disease with median survival rates not exceeding 13 months. The first Phase III study of bevacizumab, added to cisplatin or a non-cisplatin-containing doublet, showed significant increase in both overall survival and progression-free survival. Further studies are needed before bevacizumab plus chemotherapy can be considered the standard of care for advanced disease. Characterization of the mutational landscape of cervical cancer has already been initiated, indicating that, for now, few of these targetable alterations match with available agents. Progress in both the mutational landscape knowledge and developments of novel targeted therapies may result in more effective and individualized treatments for cervical cancer. The potential efficacy of knocking down the key alterations in cervical cancer - E6 and E7 human papillomavirus oncoproteins - must not be overlooked.

Host cell factor-1 recruitment to E2F-bound and cell-cycle-control genes is mediated by THAP11 and ZNF143

Host cell factor-1 (HCF-1) is a metazoan transcriptional coregulator essential for cell-cycle progression and cell proliferation. Current models suggest a mechanism whereby HCF-1 functions as a direct coregulator of E2F proteins, facilitating the expression of genes necessary for cell proliferation. In this report, we show that HCF-1 recruitment to numerous E2F-bound promoters is mediated by the concerted action of zinc finger transcription factors THAP11 and ZNF143, rather than E2F proteins directly. THAP11, ZNF143, and HCF-1 form a mutually dependent complex on chromatin, which is independent of E2F occupancy. Disruption of the THAP11/ZNF143/HCF-1 complex results in altered expression of cell-cycle control genes and leads to reduced cell proliferation, cell-cycle progression, and cell viability. These data establish a model in which a THAP11/ZNF143/HCF-1 complex is a critical component of the transcriptional regulatory network governing cell proliferation.

IGF axis and other factors in HPV-related and HPV-unrelated carcinogenesis (review)

The insulin-like growth factor (IGF) axis promotes the growth of cells, tissues and organs. IGF-1 is mainly produced in the liver but is also secreted from local tissues. In the circulation, IGF-1 is bound to insulin-like binding proteins (IGFBPs), and when released it activates the insulin-like growth factor receptor (IGF-1R). The signal is further transmitted by intracellular signaling pathways leading to gene expression that regulates, among others, cell proliferation and survival. This review presents the IGF axis in the context of cell transformation and cancer development. Aspects involving IGF-1 deficiency and protection from cancer are also briefly described. Furthermore, human papillomaviruses (HPVs) interplaying with IGF axis components in cervical cancer development are described. These small dsDNA viruses are divided into low-risk and high-risk HPVs with regard to the potency of their oncogenic actions; they mainly infect epithelial or mucosal cells. Special attention is drawn to expression of two major HPV oncogenes (E6 and E7) initiating and maintaining cervical carcinogenesis, which is a multistep and multifactorial process; therefore, involvement of additional factors such as mitochondrial DNA changes, sex hormones, retinoic and folic acids are also discussed. Finally, IGF axis components and HPV oncogenes as targets in anticancer treatment are presented which include IGF-1R downregulation, RNA interference and anti-HPV therapeutic vaccines. The review concludes that despite an enormous advancement in research on IGF and HPV-related cancers, more molecular studies and clinical trials are needed before commercialized therapies are widely available for oncology patients.

RNA interference technology used for the study of aquatic virus infections

Aquaculture is one of the most important economic activities in Asia and is presently the fastest growing sector of food production in the world. Explosive increases in global fish farming have been accompanied by an increase in viral diseases. Viral infections are responsible for huge economic losses in fish farming, and control of these viral diseases in aquaculture remains a serious challenge. Recent advances in biotechnology have had a significant impact on disease reduction in aquaculture. RNAi is one of the most important technological breakthroughs in modern biology, allowing us to directly observe the effects of the loss of specific genes in living systems. RNA interference technology has emerged as a powerful tool for manipulating gene expression in the laboratory. This technology represents a new therapeutic approach for treating aquatic diseases, including viral infections. RNAi technology is based on a naturally occurring post-transcriptional gene silencing process mediated by the formation of dsRNA. RNAi has been proven widely effective for gene knockdown in mammalian cultured cells, but its utility in fish remains unexplored. This review aims to highlight the RNAi technology that has made significant contributions toward the improvement of aquatic animal health and will also summarize the current status and future strategies concerning the therapeutic applications of RNAi to combat viral disease in aquacultured organisms.

In vitro and in vivo growth suppression of human papillomavirus 16-positive cervical cancer cells by CRISPR/Cas9

Deregulated expression of high-risk human papillomavirus oncogenes (E6 and E7) is a pivotal event for pathogenesis and progression in cervical cancer. Both viral oncogenes are therefore regarded as ideal therapeutic targets. In the hope of developing a gene-specific therapy for HPV-related cancer, we established CRISPR/Cas9 targeting promoter of HPV 16 E6/E7 and targeting E6, E7 transcript, transduced the CRISPR/Cas9 into cervical HPV-16-positive cell line SiHa. The results showed that CRISPR/Cas9 targeting promoter, as well as targeting E6 and E7 resulted in accumulation of p53 and p21 protein, and consequently remarkably reduced the abilities of proliferation of cervical cancer cells in vitro. Then we inoculated subcutaneously cells into nude mice to establish the transplanted tumor animal models, and found dramatically inhibited tumorigenesis and growth of mice incubated by cells with CRISPR/Cas9 targeting (promoter+E6+E7)-transcript. Our results may provide evidence for application of CRISPR/Cas9 targeting HR-HPV key oncogenes, as a new treatment strategy, in cervical and other HPV-associated cancer therapy.

In vivo comparison of local versus systemic delivery of immunostimulating siRNA in HPV-driven tumours

Small interfering RNAs (siRNAs) to inhibit oncogene expression and also to activate innate immune responses via Toll-like receptor (TLR) recognition have been shown to be beneficial as anti-cancer therapy in certain cancer models. In this study, we investigated the effects of local versus systemic delivery of such immune-stimulating Dicer-substrate siRNAs (IS-DsiRNAs) on a human papillomavirus (HPV)-driven tumour model. Localized siRNA delivery using intratumour injection of siRNA was able to increase siRNA delivery to the tumour compared with intravenous (IV) delivery and potently activated innate immune responses. However, IV injection remained the more effective delivery route for reducing tumour growth. Although IS-DsiRNAs activated innate immune cells and required interferon-α (IFNα) for full effect on tumour growth, we found that potent silencing siRNA acting independently of IFNα were overall more effective at inhibiting TC-1 tumour growth. Other published work utilising IS-siRNAs have been carried out on tumour models with low levels of major histocompatibility complex (MHC)-class 1, a target of natural killer cells that are potently activated by IS-siRNA. As TC-1 cells used in our study express high levels of MHC-class I, the addition of the immunostimulatory motifs may not be as beneficial in this particular tumour model. Our data suggest that selection of siRNA profile and delivery method based on tumour environment is crucial to developing siRNA-based therapies.

Functional regulatory role of STAT3 in HPV16-mediated cervical carcinogenesis

Signal transducer and activator of transcription 3 (STAT3) is an oncogenic transcription factor constitutively active and aberrantly expressed in cervical cancer. However, the functional role of STAT3 in regulation of HPV's viral oncogene expression and downstream events associated with cervical carcinogenesis is not known. Our present study performed on HPV16-positive cervical cancer cell lines (SiHa and CaSki) and primary tumor tissues revealed a strong positive correlation of constitutively active STAT3 with expression of HPV16 E6 and E7 oncoproteins and a negative association with levels of p53 and pRB. Pharmacologic targeting of STAT3 expression in cervical cancer cell lines either by STAT3-specific siRNA or blocking its tyrosine phosphorylation by AG490 or curcumin led to dose-dependent accumulation of p53 and pRb in cervical cancer cells. Interestingly, the suppression of STAT3 expression or activation was associated with the gradual loss of HPV16 E6 and E7 expression and was accompanied by loss of cell viability. The viability loss was specifically high in HPV16-positive cells as compared to HPV negative C33a cells. These findings substantiate the regulatory role of STAT3 in HPV16-mediated cervical carcinogenesis. Leads obtained from the present study provide a strong rationale for developing novel STAT3-based approaches for therapeutic interventions against HPV infection to control cervical cancer.

Inhibition of cervical cancer cell growth in vitro and in vivo by lentiviral-vector mediated shRNA targeting the common promoter of HPV16 E6 and E7 oncogenes

Deregulated expression of high-risk human papillomavirus oncogenes (E6 and E7) is a pivotal event for pathogenesis and progression in cervical cancer. Both viral oncogenes are therefore regarded as ideal therapeutic targets. Small interfering RNAs (siRNA) or double-stranded RNAs can knock down target genes effectively through siRNA-induced transcriptional gene silencing (TGS). Here, we established lentiviral-vector mediated shRNA (LV-shRNA) targeting common promoter of HPV16 E6/E7 and targeting E6 transcript, transduced the lentiviral construct into cervical HPV16-positive cell lines Siha and Caski, then selected and established stably transduced monoclonal cell lines. The results showed that LV-shRNA targeting promoter, as well as targeting E6 transcript, effectively knocked down E6 and E7 expression, resulted in accumulation of p53 and pRB protein and decrease of MCM7 and p16 protein, and consequently remarkably reduced the abilities of proliferation and invasiveness of cervical cancers cells in vitro. Then we inoculated subcutaneously those monoclonal cells into nude mice to establish the transplanted tumor animal models, and found dramatically inhibited tumorigenesis and growth, as well as prolonged survival time of mice incubated by cells with LV-shRNA targeting promoter and E6 transcript. Our results may provide evidence for application of LV-shRNA targeting HR-HPV key oncogenes, as a new treatment strategy, in cervical and other HPV-associated cancer therapy.

Cell growth inhibition in HPV 18 positive uveal melanoma cells by E6/E7 siRNA

Uveal melanoma (UM) is the most common primary intraocular malignancy in adults. However, the molecular development of UM is not fully understood and current therapeutic modalities result in poor outcomes. Increasingly, data have shown that human papillomaviruses (HPVs) contribute to the development of cervical cancer and other malignancies, and the key viral oncoprotein E6/E7 has become the target of gene therapy in HPV-related cancers. In this study, we identified HPV 18 infection in the UM cell line, VUP, for the first time and silenced HPV 18 E6/E7 expression using siRNA. Our results demonstrated that down regulation of HPV 18E6/E7 led to growth inhibition and cell cycle block in VUP cells by activation of the p53 and Rb pathways. We propose that HPV is possibly involved in the development of UM, and provide a novel target for the development of therapeutic strategies for UM.

Liberation of functional p53 by proteasome inhibition in human papilloma virus-positive head and neck squamous cell carcinoma cells promotes apoptosis and cell cycle arrest

Human papilloma virus (HPV) infection represents an emerging risk factor in head and neck squamous cell carcinoma (HNSCC). In contrast to HPV-negative HNSCC, most cases of HPV-positive HNSCC encode wild-type p53, although the p53 protein in these cells is rapidly degraded via HPV E6-mediated ubiquitination and subsequent proteasomal degradation. This unique feature of HPV-positive HNSCC has raised hope that liberation of wild-type p53 from the E6 protein may have therapeutic benefit in this disease. Indeed, suppression of E6 expression promotes apoptosis in HPV-positive HNSCC cell lines. However, the role of p53 in mediating this cell death has not been determined. Here, we demonstrate that siRNAs targeting the E6/E7 RNA, or treatment with the proteasome inhibitor bortezomib, resulted in upregulation of functional p53 and p53 gene targets in three HPV-positive HNSCC cell lines, but not in HPV-negative HNSCC cells. Apoptosis induced by E6/E7 siRNA in HPV-positive cells was found to be dependent on p53, while bortezomib-induced cell death was modestly p53-dependent. Treatment with subtoxic doses of bortezomib led to cell cycle arrest in HPV-positive, but not HPV-negative HNSCC cells. Moreover, this cell cycle arrest was mediated by p53 and the cell cycle inhibitor p21, the product of a p53 target gene. Collectively, these findings establish that wild-type p53 encoded by HPV-positive HNSCC cells, once liberated from HPV E6, can play important roles in promoting apoptosis and cell cycle arrest.

RNA interference for the treatment of papillomavirus disease

Human Papillomavirus (HPV)-induced diseases are a significant burden on our healthcare system and current therapies are not curative. Vaccination provides significant prophylactic protection but effective therapeutic treatments will still be required. RNA interference (RNAi) has great promise in providing highly specific therapies for all HPV diseases yet this promise has not been realised. Here we review the research into RNAi therapy for HPV in vitro and in vivo and examine the various targets and outcomes. We discuss the idea of using RNAi with current treatments and address delivery of RNAi, the major issue holding back clinical adoption. Finally, we present our view of a potential path to the clinic.

RNA interference with special reference to combating viruses of crustacea

RNA interference has evolved from being a nuisance biological phenomenon to a valuable research tool to determine gene function and as a therapeutic agent. Since pioneering observations regarding RNA interference were first reported in the 1990s from the nematode worm, plants and Drosophila, the RNAi phenomenon has since been reported in all eukaryotic organisms investigated from protozoans, plants, arthropods, fish and mammals. The design of RNAi therapeutics has progressed rapidly to designing dsRNA that can specifically and effectively silence disease related genes. Such technology has demonstrated the effective use of short interfering as therapeutics. In the absence of a B cell lineage in arthropods, and hence no long term vaccination strategy being available, the introduction of using RNA interference in crustacea may serve as an effective control and preventative measure for viral diseases for application in aquaculture.

Progress toward in vivo use of siRNAs-II

RNA interference (RNAi) has been extensively employed for in vivo research since its use was first demonstrated in mammalian cells 10 years ago. Design rules have improved, and it is now routinely possible to obtain reagents that suppress expression of any gene desired. At the same time, increased understanding of the molecular basis of unwanted side effects has led to the development of chemical modification strategies that mitigate these concerns. Delivery remains the single greatest hurdle to widespread adoption of in vivo RNAi methods. However, exciting advances have been made and new delivery systems under development may help to overcome these barriers. This review discusses advances in RNAi biochemistry and biology that impact in vivo use and provides an overview of select publications that demonstrate interesting applications of these principles. Emphasis is placed on work with synthetic, small interfering RNAs (siRNAs) published since the first installment of this review which appeared in 2006.

Transcriptional gene silencing of HPV16 E6/E7 induces growth inhibition via apoptosis in vitro and in vivo

OBJECTIVE

Transcriptional silencing of HPV oncogenes using short interfering RNA (siRNA) blocks E6/E7 expression. Our objective was to estimate the effective value of E6/E7 specific siRNA-induced transcriptional gene silencing as a potential therapeutic strategy for cervical cancer.

METHODS

In vitro studies were performed by employing two categories of siRNA targeting promoter of E6/E7 gene and E7 transcript, respectively, and inhibitory effect of both siRNAs was further observed in vitro and on xenograft in BALB/c mice that were inoculated with siRNA transfected SiHa cells and parental SiHa cells followed by siRNA intratumoral injection in vivo. Tumor volume and growth curves were assessed. Furthermore, cellular proliferation and apoptosis of inoculated tumors were determined by immunohistochemistry staining and TUNEL assay.

RESULTS

The two most active siRNA sequences specifically knockdown E6/E7 expressions at mRNA level in HPV16 positive Siha cells, increased p53 and decreased p16 expressions at protein level, inhibited cell proliferation, and induced cell apoptosis in vitro. Furthermore, both siRNAs effectively inhibited tumor formation and growth no matter in mice with siRNA transfected cells in vitro or with siRNA intratumoral injection in vivo. TUNEL staining and FCM assay consistently showed that tumor retardation was through induction of cellular apoptosis.

CONCLUSION

RNAi targeting the promoter of HPV16 E6/E7 acts effectively in vitro and in vivo, especially through intratumoral delivery, and may be a candidate therapeutic strategy for cervical cancer.