Inhibition of growth, transformation, and expression of human papillomavirus type 16 E7 in human keratinocytes by alpha interferons

The Micro-Immunotherapy Medicine 2LPAPI® Displays Immune-Modulatory Effects in a Model of Human Papillomavirus Type-16 L1-Protein Capsid-Treated Human Peripheral Blood Mononuclear Cells and Antiproliferative Effects in a Model of Cervical Cancer Cells

Human papillomavirus (HPV) is the second most common infectious agent causing cancer. Persistent infection with high-risk (HR)-HPV can lead to cervical intra-epithelial neoplasia and cervical carcinomas (CC). While host immune response is necessary for viral clearance, chronic immune activation contributes to a low-grade inflammation that can ultimately lead to carcinogenesis. The micro-immunotherapy medicine (MIM) 2LPAPI® could be a valuable tool to manage the clearance of the virus and reduce the risk of developing CC. In this in vitro study, we aimed to investigate its mode of action. We showed that actives from the MIM increased the IL-6, IFN-γ, and IP-10 secretion in human peripheral blood mononuclear cells (PBMCs) exposed to peptides derived from the HPV-16 capsid (HPV16(L1)). This could reflect an increase in the immune activity toward HPV-16. At the same time, some active substances reduced the lympho-proliferation and the expression of T-cell activation markers. Finally, some of the MIM actives displayed antiproliferative effects in CC-derived HeLa cells under serum-starvation conditions. Altogether, this body of data highlighted for the first time the dual effect of MIM in the framework of HR-HPV infections as a potential (i) immune modulator of HPV16(L1)-treated PBMCs and (ii) antiproliferative agent of HPV-positive CC cells.

Viral Modulation of TLRs and Cytokines and the Related Immunotherapies for HPV-Associated Cancers

The modulation of the host innate immune system is a well-established carcinogenesis feature of several tumors, including human papillomavirus- (HPV-) related cancers. This virus is able to interrupt the initial events of the immune response, including the expression of Toll-like receptors (TLRs), cytokines, and inflammation. Both TLRs and cytokines play a central role in HPV recognition, cell maturation and differentiation as well as immune signalling. Therefore, the imbalance of this sensitive control of the immune response is a key factor for developing immunotherapies, which strengthen the host immune system to accomplish an efficient defence against HPV and HPV-infected cells. Based on this, the review is aimed at exposing the HPV immune evasion mechanisms involving TLRs and cytokines and at discussing existing and potential immunotherapeutic TLR- and cytokine-related tools.

The human papillomavirus E7 oncoprotein as a regulator of transcription

High-risk human papillomaviruses (HPVs) encode oncoproteins which manipulate gene expression patterns in the host keratinocytes to facilitate viral replication, regulate viral transcription, and promote immune evasion and persistence. In some cases, oncoprotein-induced changes in host cell behavior can cause progression to cancer, but a complete picture of the functions of the viral oncoproteins in the productive HPV life cycle remains elusive. E7 is the HPV-encoded factor most responsible for maintaining cell cycle competence in differentiating keratinocytes. Through interactions with dozens of host factors, E7 has an enormous impact on host gene expression patterns. In this review, we will examine the role of E7 specifically as a regulator of transcription. We will discuss mechanisms of regulation of cell cycle-related genes by E7 as well as genes involved in immune regulation, growth factor signaling, DNA damage responses, microRNAs, and others pathways. We will also discuss some unanswered questions about how transcriptional regulation by E7 impacts the biology of HPV in both benign and malignant conditions.

Interferon-Tau has Antiproliferative effects, Represses the Expression of E6 and E7 Oncogenes, Induces Apoptosis in Cell Lines Transformed with HPV16 and Inhibits Tumor Growth In Vivo

Interferon tau (IFN-τ) is a promising alternative antiviral and immunotherapeutic agent in a wide variety of diseases including infectious, neurodegenerative, autoimmune and cancer due to its low toxicity in comparison with other type I interferon´s. The objective of our study was established the effect of the bovine IFN-τ on human (SiHa) and murine (BMK-16/myc) cells transformed with HPV 16 and evaluates the antitumor effect in a murine tumor model HPV 16 positive. We determine that bovine IFN-τ has antiproliferative effects, pro-apoptotic activity and induces repression of viral E6 and E7 oncogenes (time- and dose-dependent) on human and murine cells transformed with HPV 16 similar to the effects of IFN-β. However, IFN-τ induces greater antiproliferative effect, apoptosis and repression of both oncogenes in BMK-16/myc cells compared to SiHa cells. The differences were explained by the presence and abundance of the type I interferon receptor (IFNAR) in each cell line. On the other hand, we treated groups of tumor-bearing mice (HPV16 positive) with IFN-τ and showed the inhibition tumor growth effect in vivo. Our finding indicates that bovine IFN-τ may be a good candidate for immunotherapy against cervical cancer.

The inhibitory action of P56 on select functions of E1 mediates interferon's effect on human papillomavirus DNA replication

The interferon (IFN)-induced protein P56 inhibits human papillomavirus (HPV) DNA replication by binding to HPV E1, which has several distinct functions in initiating viral DNA replication. Here, we determined that P56 inhibited HPV type 18 (HPV18) E1's DNA helicase activity, E2 binding, and HPV Ori sequence-specific DNA binding but not nonspecific DNA binding. We observed that deletion of a single amino acid, F399, produced an E1 mutant that could not bind P56. This E1 mutant retained its ability to support Ori DNA replication, but this activity was not inhibited by IFN, demonstrating that P56 is the principal executor of the anti-HPV action of IFN.

Local expression of interferon-alpha and interferon receptors in cervical intraepithelial neoplasia

PURPOSE

The present study evaluated mRNA expression of interferon-alpha (IFN-alpha), IFN-alpha receptor subunits (IFNAR-1 and IFNAR-2) and an IFN-stimulated gene encoding the enzyme 2',5'-oligoadenylate synthetase (2'5'OAS) in biopsies on patients with varying grades of cervical intraepithelial neoplasia (CIN I, II and III).

METHODS

Uterine cervix biopsies were collected from women with CIN I, II and III (n = 28) and controls without CIN lesions or human papilloma virus (HPV) infection (n = 17). The presence of high and low-risk HPV DNA was determined using hybrid capture. The mRNA levels of IFNAR-1, IFNAR-2, IFN-alpha and 2'5'OAS were determined by RT-PCR with specific primers.

RESULTS

The control group exhibited a greater frequency of IFNAR-1 expression (10/17; 58.3%) than the CIN samples (4/28; 14.2%) (P = 0.0018), while, the expression of IFNAR-2 was also greater in the control samples (11/17; 64.7%) than in the patients with lesions (2/28; 7.1%) (P = 0.0018). Importantly, simultaneous expression of both receptors was observed only in the control group (8/17; 47.0%) (P = 0.0001). Among the CIN samples, there was one case of low expression of mRNA of IFNAR-1 and IFNAR-2. IFN-alpha was present in 14.2% (4/28) of the CIN samples but was not expressed in the control group. mRNA 2'5'OAS were expressed in 28.5% (8/28) of the CIN samples and 11.7% (2/17) of the control samples (not statistically significant). Fifty percent (14/28) of the CIN samples were positive for HPV DNA.

CONCLUSIONS

Cervical biopsy samples from control women or those without neoplasia or HPV infection displayed higher IFN-alpha receptor expression than those with CIN, while simultaneous expression of both IFN-alpha receptor subunits was found only in the control group. There was no significant difference in mRNA expression of IFN-alpha and 2'5'OAS between the control and CIN groups. Then we concluded that the samples obtained from patients with CIN present low levels of the IFN-alpha receptor mRNA.

Interferon-inducible protein, P56, inhibits HPV DNA replication by binding to the viral protein E1

Type I interferon (IFN) inhibits, by an unknown mechanism, the replication of human papillomaviruses (HPV), which are major human pathogens, Here, we present evidence that P56 (a protein), the expression of which is strongly induced by IFN, double-stranded RNA and viruses, mediates the anti-HPV effect of IFN. Ectopic expression of P56 inhibited HPV DNA replication and its ablation in IFN-treated cells alleviated the inhibitory effect of IFN on HPV DNA replication. Protein-protein interaction and mutational analyses established that the antiviral effect of P56 was mediated by its direct interaction with the DNA replication origin-binding protein E1 of several strains of HPV, through the tetratricopeptide repeat 2 in the N-terminal region of P56 and the C-terminal region of E1. In vivo, the interaction with P56, a cytoplasmic protein, caused translocation of E1 from the nucleus to the cytoplasm. In vitro, recombinant P56, or a small fragment derived from it, inhibited the DNA helicase activity of E1 and E1-mediated HPV DNA replication. These observations delineate the molecular mechanism of IFN's antiviral action against HPV.

Interferon-alpha inhibits proliferation and induces apoptosis of merkel cell carcinoma in vitro

Merkel cell carcinoma is a tumor with aggressive biological behavior and limited response to chemotherapy. The present study investigated the effect of interferon (IFN)-alpha on growth and apoptosis of Merkel carcinoma cells in vitro. Proliferation of MCC-1 cell line was reduced dose-dependently by IFN-alpha and diminished when higher IFN-alpha concentrations were used. Additionally, IFN-alpha potently decreased DNA-synthesis and Ki67/MIB-1 proliferation index of MCC-1 cultures. Furthermore, IFN-alpha induced dose-dependently apoptosis of MCC-1 cells as shown by caspase-3 activation, and detection of apoptotic DNA strand breaks and fragmented nuclei. These findings suggest that IFN-alpha may have antitumor activity against Merkel cell carcinoma.

Immune responses to human papillomavirus in genital tract of women with cervical cancer

OBJECTIVES

To address a question whether immune responses to HPV infection play a role in control of cervical cancer, we analyzed systemic and mucosal immune responses to HPV in women who underwent radical hysterectomy for cervical cancer (HCC) or loop conization due to cervical dysplasia (LOOP), or had hysterectomy for other reasons (HNN).

METHODS

HPV-specific antibodies in sera and vaginal washes were determined by ELISA using recombinant HPV 16 E7 oncoprotein. Cytokines in vaginal washes were assayed by Linco cytokine multiplex method using Luminex technology. Differential gene expression profiling in cervical tumor was determined by microarray analysis and Real-time RT-PCR.

RESULTS

While levels of HPV-16 E7-specific IgG in vaginal wash were significantly higher in women undergoing HCC and HNN, the levels of the HPV-16 E7-specific IgA in vaginal wash of women with cervical cancer and cervical dysplasia were lower as compared to patients in HNN. Proinflammatory cytokines, such as IL-6 and IL-8, were dominant in vaginal washes of all subjects studied. However, no pattern of Th1-type and Th2-type cytokine induction was observed as demonstrated by protein analysis as well as differential gene expression profiling in cervical tumor.

CONCLUSIONS

These results suggest a selective down-regulation of local HPV-specific IgA responses in women with cervical cancer.

NFI-Ski interactions mediate transforming growth factor beta modulation of human papillomavirus type 16 early gene expression

Human papillomaviruses (HPVs) are present in virtually all cervical cancers. An important step in the development of malignant disease, including cervical cancer, involves a loss of sensitivity to transforming growth factor beta (TGF-beta). HPV type 16 (HPV16) early gene expression, including that of the E6 and E7 oncoprotein genes, is under the control of the upstream regulatory region (URR), and E6 and E7 expression in HPV16-immortalized human epithelial cells is inhibited at the transcriptional level by TGF-beta. While the URR contains a myriad of transcription factor binding sites, including seven binding sites for nuclear factor I (NFI), the specific sequences within the URR or the transcription factors responsible for TGF-beta modulation of the URR remain unknown. To identify potential transcription factors and binding sites involved in TGF-beta modulation of the URR, we performed DNase I footprint analysis on the HPV16 URR using nuclear extracts from TGF-beta-sensitive HPV16-immortalized human keratinocytes (HKc/HPV16) treated with and without TGF-beta. Differentially protected regions were found to be located around NFI binding sites. Electrophoretic mobility shift assays, using the NFI binding sites as probes, showed decreased binding upon TGF-beta treatment. This decrease in binding was not due to reduced NFI protein or NFI mRNA levels. Mutational analysis of individual and multiple NFI binding sites in the URR defined their role in TGF-beta sensitivity of the promoter. Overexpression of the NFI family members in HKc/HPV16 decreased the ability of TGF-beta to inhibit the URR. Since the oncoprotein Ski has been shown to interact with and increase the transcriptional activity of NFI and since cellular Ski levels are decreased by TGF-beta treatment, we explored the possibility that Ski may provide a link between TGF-beta signaling and NFI activity. Anti-NFI antibodies coimmunoprecipitated endogenous Ski in nuclear extracts from HKc/HPV16, confirming that NFI and Ski interact in these cells. Ski levels dramatically decreased upon TGF-beta treatment of HKc/HPV16, and overexpression of Ski eliminated the ability of TGF-beta to inhibit the URR. Based on these studies, we propose that TGF-beta inhibition of HPV16 early gene expression is mediated by a decrease in Ski levels, which in turn dramatically reduces NFI activity.

Disturbance of tumor necrosis factor alpha-mediated beta interferon signaling in cervical carcinoma cells

In the present study we show that malignant human papillomavirus (HPV)-positive cells lost their ability to synthesize endogenous beta interferon (IFN-beta) upon tumor necrosis factor alpha (TNF-alpha) treatment. IFN-beta transcription, however, was reinducible in nonmalignant HPV-positive cells, which was confirmed in functional protection assays against encephalomyocarditis virus or vesicular stomatitis virus infections. Addition of neutralizing antibodies against IFN-beta blocked the antiviral effect, excluding the possibility that other IFN types were involved. Conversely, both malignant and immortalized cells could be protected against viral cytolysis when either IFN-beta, IFN-alpha, or IFN-gamma was added exogenously. This indicates that only the cross talk between TNF-alpha and the IFN-beta pathways, and not IFN-alpha/beta and IFN-gamma signaling in general, is perturbed in cervical carcinoma cells. Notably, full virus protection was restricted exclusively to nonmalignant cells, indicating that the antiviral effect correlates with the growth-inhibitory and virus-suppressive properties of TNF-alpha. The IFN-regulatory factors IRF-1 and p48 (ISGF3gamma) emerged as key regulatory molecules in the differential IFN-beta response, since their transcription was either absent or only inefficiently enhanced in tumorigenic cells upon treatment with TNF-alpha. Inducibility of both genes, however, became reestablished in cervical carcinoma cells, which were complemented to nontumorigenicity after somatic cell hybridization. Complementation was paralleled by the entire reconstitution of cytokine-mediated IFN-beta expression and the ability of TNF-alpha to exert an antiviral state. In contrast, under conditions where tumor suppression was not accomplished upon somatic cell hybridization, neither expression of IRF-1, p48, and IFN-beta nor antiviral activity could be restored.

Enhanced Antiviral Benefit of Combination Therapy with Lamivudine and Alpha Interferon against WHV Replication in Chronic Carrier Woodchucks

Cell culture studies in our laboratory previously demonstrated synergistic antiviral activity for the combinations of lamivudine and a novel recombinant hybrid human alpha B/D interferon (rHuαB/D IFN) against hepatitis B virus (HBV) replication. Based on these results, a study was designed to determine if an enhanced antiviral effect with this drug combination could be demonstrated in vivo using the woodchuck hepatitis virus (WHV)/woodchuck experimental model of chronic HBV infection. Both antiviral agents have been shown to be effective against WHV replication in WHV chronic carriers during previous studies by our laboratories. Two combination treatment regimens were compared to matched monotherapies in a placebo-controlled trial. The first used simultaneous administration of rHuαB/D IFN and lamivudine for 24 weeks. The other combination treatment regimen used a staggered dosing schedule of 12 weeks of administration of lamivudine alone, followed by 12 weeks of simultaneous dosing with both drugs, followed by 12 weeks of therapy with rHuαB/D IFN alone. Both treatment regimens with combinations of lamivudine and rHuαB/D IFN were more effective at reducing WHV replication in chronically infected wood-chucks than the corresponding monotherapies. Both combination treatments produced antiviral effects that were at least equal to that expected for additive activity based on estimations generated by Bliss Independence calculations. The staggered treatment regimen reduced viraemia and intrahepatic WHV replication significantly more than that expected for additive interactions, indicating synergistic antiviral effects. These studies demonstrate that combination therapy of chronic WHV infection has enhanced antiviral benefit over corresponding monotherapies and indicate that combination treatment of chronic HBV infection can be superior to therapies using a single antiviral agent.

IFN-tau exhibits potent suppression of human papillomavirus E6/E7 oncoprotein expression

The effects of interferon-tau (IFN-tau) on tumor suppressor factors and virus oncoprotein expression were compared with two other type I IFN in human papillomavirus (HPV-16)-transformed cells. Nontumorigenic human keratinocytes, HuKc/HPV-16d-2C (d-2C), treated with recombinant human IFN-alpha2a (Roferon), a human recombinant alpha IFN hybrid, alpha B/D (IFN-alphaB/D), or ovine IFN-tau were evaluated for their effects on the levels of E6 and E7 expression. IFN-tau was comparable to IFN-alpha2a in decreasing intracellular levels of E6 and E7, and IFN-alphaB/D was more effective than IFN-a2a in suppressing E7 levels. All three IFN were capable of increasing the cellular concentration of wild-type p53 tumor suppressor with the magnitude IFN-tau > IFN-alpha2a > IFN-alphaB/D. Increases in p53 concentrations correlated with the observed decreases in E6 mRNA and protein levels. The antiviral effects observed in this study reveal that IFN-tau has potent antipapillomavirus activity. Sequences/structures unique to IFN-tau could allow for alternative IFN/receptor interactions and may explain the differences in biologic function.

Monocyte-chemo-attractant-protein-1 (MCP-1)-gene expression in cervical intra-epithelial neoplasias and cervical carcinomas

Chemokines play a central role in the chemotactic activation of immunological effector cells. One of the currently best characterized chemokines is the monocyte-chemo-attractant protein-1 (MCP-1), which is involved in the cross-talk with cells of the monocyte-macrophage lineage. Since macrophages and macrophage-derived cytokines appear to be important in the transcriptional regulation of "high-risk" types of human papillomaviruses (HPV), we monitored MCP-1 expression by in situ hybridization (ISH) in histologically distinct stages of cervical intra-epithelial neoplasms (CIN), cervical cancer and non-HPV-associated cases of erosive endocervicitis. Here, we demonstrate that high-grade dysplasia (CIN III, n = 9) completely lacks both MCP-1 expression and CD68+-macrophage infiltration, while MCP-1-specific signals were occasionally detectable in one out of 5 CIN-II and in one out of 3 CIN-I lesions. Inspection of hyperplastic squamous epithelium adjacent to cervical carcinomas reveals high MCP-1 expression and accumulation of infiltrating macrophages. In contrast, no macrophages could be detected in corresponding hyperplastic tissue areas surrounding CIN-II and CIN-III lesions, although MCP-1 was found to be highly expressed. Finally, in agreement with our earlier in vitro data, invasive carcinomas of the cervix uteri showed MCP-1-specific hybridization signals and macrophage infiltration only in the stroma surrounding the carcinoma cells and in endothelial cells of capillaries, especially at the invasion front of the tumor, while the inner mass of the carcinomas was completely negative. On the other hand, ISH and histochemical evaluation of inflammatory, non-HPV-associated cases of erosive endocervicitis indicate strong MCP-1 expression, which is regularly accompanied by chemotactic appearance of macrophages. These observations indicate that dysregulation of MCP-1-gene expression may represent an important step during HPV-linked carcinogenesis, allowing the escape of virus-positive cells from local immune response.

Glucocorticoids stimulate growth of human papillomavirus type 16 (HPV16)-immortalized human keratinocytes and support HPV16-mediated immortalization without affecting the levels of HPV16 E6/E7 mRNA

We investigated the effects of the glucocorticoids hydrocortisone and dexamethasone on human papillomavirus type 16 (HPV16)-mediated human cell carcinogenesis using normal human keratinocytes (HKc) and HKc immortalized by transfection with HPV16 DNA (HKc/HPV16). Normal HKc did not require glucocorticoids for proliferation. In contrast, growth of early passage HKc/HPV16 strictly required these hormones, although glucocorticoid dependence became less stringent during in vitro progression. Glucocorticoid dependence was acquired by HKc early after immortalization with HPV16 DNA, and glucocorticoids were required for efficient HKc immortalization. However, treatment of HKc/HPV16 with hydrocortisone or dexamethasone did not increase the steady-state levels of HPV16 E6/E7 mRNA or protein. Firefly luciferase activity expressed under the control of the HPV16 upstream regulatory region and P97 promoter increased by about fourfold following dexamethasone treatment of HeLa, but only twofold in HKc/HPV16, and less than twofold in SiHa. However, all of these cell lines expressed sufficient endogenous glucocorticoid receptors to allow for a dexamethasone response of the mouse mammary tumor virus promoter. These results indicate that mechanisms other than a direct influence by glucocorticoids on HPV16 early gene expression may contribute to the striking biological effects of these steroids on HPV16-mediated human cell carcinogenesis.

Effect of interferon therapy on human papillomavirus copy number in patients with Condyloma acuminatum

Interferons exert antiviral, antiproliferative, and immunomodulatory effects on target cells. The effectiveness of interferon treatment can be followed by measuring parameters involved in interferon action. The clinical effectiveness of interferons has been proved in the human papillomavirus (HPV)-associated disease condyloma acuminatum. Because one of the most important goals in the treatment of this condition is the elimination of recurrences, it was asked whether clinically effective interferon therapy was associated with elimination of HPV DNA. The authors used a polymerase chain reaction-based method to detect the HPV from minute amounts of clinical biopsies. Human papillomavirus-transformed cell lines or cloned HPV genomes served as different copy number controls. The intensity ratio of L1 HPV and the human beta-globin (which served as an internal control) fragments was determined and used for estimation of HPV copy number in different biopsies. A direct effect of interferon treatment on HPV viral genome copies was observed in a group of responder patients, but not in the clinically resistant group. With these data, a correlation was found between virologic data and clinical findings. This method also can be used in other lesions to determine the HPV copy number and HPV type and may have value in determining the antiviral activities of other agents used in the treatment of HPV-related lesions.

HPV replication in experimental models: effects of interferon

Preclinical evaluation of the effectiveness of interferon (IFN) therapy on human papillomaviruses (HPV) has been hampered by the inability to propagate these viruses in cell culture. Nonetheless, interferon is used extensively in the treatment of HPV infections. Alpha interferons in particular have found a place in the treatment of anogenital disease, plantar warts, and laryngeal papillomas. While their is significant clinical evidence to suggest that interferon is useful in therapy of disease, the cellular mechanism(s) (i.e., antiviral, antiproliferative, immunomodulatory) by which IFN is able to control HPV-induced pathology is not well understood. This review focuses on experimental animal and cell culture models which are currently being used to help identify the antiviral, antiproliferative and immunomodulatory effects of IFN on HPV infection.