In Vitro Antiviral and Anticancer Effects of Tanacetum sinaicum Essential Oil on Human Cervical and Breast Cancer

BACKGROUND

Cervical cancer has been linked to human papillomavirus (HPV) types 16 and 18. Essential oils (EOs) are vital natural products of plants with various therapeutic and biological properties.

OBJECTIVES

The purpose of this study is to investigate and assess Tanacetum sinaicum essential oil's possible antiviral and anticancer properties, with a focus on its in vitro effects on human cervical cancer and human breast adenocarcinoma cell lines.

MATERIALS AND METHODS

Tanacetum sinaicum EO was extracted via hydrodistillation (HD) and characterized using gas chromatography-mass spectrometry (GC-MS). MTT assay was used to determine the cell viability of Hela (a human epithelial cervical cancer) and MCF-7 (human breast adenocarcinoma) cell lines. Quantitative real-time polymerase chain reaction (PCR) was utilized to assess the antiviral efficacy of EO against HPV-16 and 18, and anti-metastatic characteristics. The biological activity of EO was assessed using Autophage and Cell genotoxicity via the comet assay.

RESULTS

EO is mostly composed of chrysanthenyl acetate, thujone, and verbenol. The cell viability was reduced after 24 hours of incubation at doses from 100 to 400 µg/ml. Concentrations of 800 to 3,200 µg/ml significantly inhibit cell growth. After a 24-hour incubation period, doses ranging from 100 to 400 µg/ml reduced cell viability from 62 to 72%. Concentrations of 800 to 3,200 µg/ml significantly suppress cell growth by over 95%. In MCF7 and HeLa cell lines, EO lowered virus copy numbers in a dose-dependent manner, with higher concentrations of the oil inhibiting virus replication more effectively. EO treatment increased the number of autophagosomes/autolysosomes and acidic vesicular organelles in both cell lines. On the HeLa and MCF7 cell lines, EO demonstrated antiproliferative and antimetastatic effects. The results demonstrated that EO had dose-dependent genotoxic effects on both cancer cell lines, as evidenced by DNA damage.

CONCLUSION

Tanacetum sinaicum EO is a prospective source of natural bioactive compounds that can be employed in pharmaceutical and medicinal applications due to its antiviral, antiproliferative, anti-metastatic and genotoxic properties.

Development of DNA Vaccine Targeting E6 and E7 Proteins of Human Papillomavirus 16 (HPV16) and HPV18 for Immunotherapy in Combination with Recombinant Vaccinia Boost and PD-1 Antibody

Immunotherapy for cervical cancer should target high-risk human papillomavirus types 16 and 18, which cause 50% and 20% of cervical cancers, respectively. Here, we describe the construction and characterization of the pBI-11 DNA vaccine via the addition of codon-optimized human papillomavirus 18 (HPV18) E7 and HPV16 and 18 E6 genes to the HPV16 E7-targeted DNA vaccine pNGVL4a-SigE7(detox)HSP70 (DNA vaccine pBI-1). Codon optimization of the HPV16/18 E6/E7 genes in pBI-11 improved fusion protein expression compared to that in DNA vaccine pBI-10.1 that utilized the native viral sequences fused 3' to a signal sequence and 5' to the HSP70 gene of Mycobacterium tuberculosis Intramuscular vaccination of mice with pBI-11 DNA better induced HPV antigen-specific CD8+ T cell immune responses than pBI-10.1 DNA. Furthermore, intramuscular vaccination with pBI-11 DNA generated stronger therapeutic responses for C57BL/6 mice bearing HPV16 E6/E7-expressing TC-1 tumors. The HPV16/18 antigen-specific T cell-mediated immune responses generated by pBI-11 DNA vaccination were further enhanced by boosting with tissue-antigen HPV vaccine (TA-HPV). Combination of the pBI-11 DNA and TA-HPV boost vaccination with PD-1 antibody blockade significantly improved the control of TC-1 tumors and extended the survival of the mice. Finally, repeat vaccination with clinical-grade pBI-11 with or without clinical-grade TA-HPV was well tolerated in vaccinated mice. These preclinical studies suggest that the pBI-11 DNA vaccine may be used with TA-HPV in a heterologous prime-boost strategy to enhance HPV 16/18 E6/E7-specific CD8+ T cell responses, either alone or in combination with immune checkpoint blockade, to control HPV16/18-associated tumors. Our data serve as an important foundation for future clinical translation.IMPORTANCE Persistent expression of high-risk human papillomavirus (HPV) E6 and E7 is an obligate driver for several human malignancies, including cervical cancer, wherein HPV16 and HPV18 are the most common types. PD-1 antibody immunotherapy helps a subset of cervical cancer patients, and its efficacy might be improved by combination with active vaccination against E6 and/or E7. For patients with HPV16+ cervical intraepithelial neoplasia grade 2/3 (CIN2/3), the precursor of cervical cancer, intramuscular vaccination with a DNA vaccine targeting HPV16 E7 and then a recombinant vaccinia virus expressing HPV16/18 E6-E7 fusion proteins (TA-HPV) was safe, and half of the patients cleared their lesions in a small study (NCT00788164). Here, we sought to improve upon this therapeutic approach by developing a new DNA vaccine that targets E6 and E7 of HPV16 and HPV18 for administration prior to a TA-HPV booster vaccination and for application against cervical cancer in combination with a PD-1-blocking antibody.

A Phase 1 Trial Assessing the Safety and Tolerability of a Therapeutic DNA Vaccination Against HPV16 and HPV18 E6/E7 Oncogenes After Chemoradiation for Cervical Cancer

PURPOSE

This study assessed the safety and tolerability of therapeutic immunization against the human papillomavirus (HPV) viral oncoproteins E6 and E7 in patients with cervical cancer after chemoradiation.

METHODS AND MATERIALS

MEDI0457 (INO-3112) is a DNA-based vaccine targeting E6 and E7 of HPV-16/18 that is coinjected with an IL-12 plasmid followed by electroporation with the CELLECTRA 5P device. At 2 to 4 weeks after chemoradiation, patients with newly diagnosed stage IB1-IVA (cohort 1) or persistent/recurrent (cohort 2) cervical cancers were treated with 4 immunizations of MEDI0457 every 4 weeks. The primary endpoints were incidence of adverse events and injection site reactions. Immune responses against HPV antigens were measured by ELISpot for interferon-γ (IFNγ), enzyme-linked immunosorbent assay for antibody responses and multiplexed immunofluorescence for immune cells in cervical biopsy specimens.

RESULTS

Ten patients (cohort 1, n = 7; cohort 2, n = 3) with HPV16 (n = 7) or HPV18 (n = 3) cervical cancers received MEDI0457 after chemoradiation. Treatment-related adverse events were all grade 1, primarily related to the injection site. Eight of 10 patients had detectable cellular or humoral immune responses against HPV antigens after chemoradiation and vaccination: 6 of 10 patients generated anti-HPV antibody responses and 6 of 10 patients generated IFNγ-producing T cell responses. At the completion of chemoradiation and vaccination, cervical biopsy specimens had detectable CD8⁺ T cells and decreased PD-1⁺CD8⁺, PD-L1⁺CD8⁺, and PD-L1⁺CD68⁺ subpopulations. All patients cleared detectable HPV DNA in cervical biopsies by completion of chemoradiation and vaccination.

CONCLUSIONS

Adjuvant MEDI0457 is safe and well tolerated after chemoradiation for locally advanced or recurrent cervical cancers, supporting further investigation into combining tumor-specific vaccines with radiation therapy.

Design and statistical considerations for studies evaluating the efficacy of a single dose of the human papillomavirus (HPV) vaccine

Cervical cancer is a leading cause of cancer mortality in women worldwide. Human papillomavirus (HPV) types 16 and 18 cause about 70% of all cervical cancers. Clinical trials have demonstrated that three doses of either commercially available HPV vaccine, Cervarix ® or Gardasil ®, prevent most new HPV 16/18 infections and associated precancerous lesions. Based on evidence of immunological non-inferiority, 2-dose regimens have been licensed for adolescents in the United States, European Union, and elsewhere. However, if a single dose were effective, vaccine costs would be reduced substantially and the logistics of vaccination would be greatly simplified, enabling vaccination programs in developing countries. The National Cancer Institute (NCI) and the Agencia Costarricense de Investigaciones Biomédicas (ACIB) are conducting, with support from the Bill & Melinda Gates Foundation and the International Agency for Research on Cancer (IARC), a large 24,000 girl study to evaluate the efficacy of a 1-dose regimen. The first component of the study is a four-year non-inferiority trial comparing 1- to 2-dose regimens of the two licensed vaccines. The second component is an observational study that estimates the vaccine efficacy (VE) of each regimen by comparing the HPV infection rates in the trial arms to those in a contemporaneous survey group of unvaccinated girls. In this paper, we describe the design and statistical analysis for this study. We explain the advantage of defining non-inferiority on the absolute risk scale when the expected event rate is near 0 and, given this definition, suggest an approach to account for missing clinic visits. We then describe the problem of estimating VE in the absence of a randomized placebo arm and offer our solution.

Novel recombinant papillomavirus genomes expressing selectable genes

Papillomaviruses infect and replicate in keratinocytes, but viral proteins are initially expressed at low levels and there is no effective and quantitative method to determine the efficiency of infection on a cell-to-cell basis. Here we describe human papillomavirus (HPV) genomes that express marker proteins (antibiotic resistance genes and Green Fluorescent Protein), and can be used to elucidate early stages in HPV infection of primary keratinocytes. To generate these recombinant genomes, the late region of the oncogenic HPV18 genome was replaced by CpG free marker genes. Insertion of these exogenous genes did not affect early replication, and had only minimal effects on early viral transcription. When introduced into primary keratinocytes, the recombinant marker genomes gave rise to drug-resistant keratinocyte colonies and cell lines, which maintained the extrachromosomal recombinant genome long-term. Furthermore, the HPV18 "marker" genomes could be packaged into viral particles (quasivirions) and used to infect primary human keratinocytes in culture. This resulted in the outgrowth of drug-resistant keratinocyte colonies containing replicating HPV18 genomes. In summary, we describe HPV18 marker genomes that can be used to quantitatively investigate many aspects of the viral life cycle.

Significantly Reduced Genoprevalence of Vaccine-Type HPV-16/18 Infections among Vaccinated Compared to Non-Vaccinated Young Women 5.5 Years after a Bivalent HPV-16/18 Vaccine (Cervarix®) Pilot Project in Uganda

The objective of this study was to determine the prevalence and some predictors for vaccine and non-vaccine types of HPV infections among bivalent HPV vaccinated and non-vaccinated young women in Uganda. This was a comparative cross sectional study 5.5 years after a bivalent HPV 16/18 vaccination (Cervarix®, GlaxoSmithKline, Belgium) pilot project in western Uganda. Cervical swabs were collected between July 2014-August 2014 and analyzed with a HPV genotyping test, CLART^® HPV2 assay (Genomica, Madrid Spain) which is based on PCR followed by microarray for determination of genotype. Blood samples were also tested for HIV and syphilis infections as well as CD4 and CD8 lymphocyte levels. The age range of the participants was 15–24 years and mean age was 18.6(SD 1.4). Vaccine-type HPV-16/18 strains were significantly less prevalent among vaccinated women compared to non-vaccinated women (0.5% vs 5.6%, p 0.006, OR 95% CI 0.08(0.01–0.64). At type-specific level, significant difference was observed for HPV16 only. Other STIs (HIV/syphilis) were important risk factors for HPV infections including both vaccine types and non-vaccine types. In addition, for non-vaccine HPV types, living in an urban area, having a low BMI, low CD4 count and having had a high number of life time sexual partners were also significant risk factors. Our data concurs with the existing literature from other parts of the world regarding the effectiveness of bivalent HPV-16/18 vaccine in reducing the prevalence of HPV infections particularly vaccine HPV- 16/18 strains among vaccinated women. This study reinforces the recommendation to vaccinate young girls before sexual debut and integrate other STI particularly HIV and syphilis interventions into HPV vaccination packages.

Gene- and protein-delivered zinc finger-staphylococcal nuclease hybrid for inhibition of DNA replication of human papillomavirus

Previously, we reported that artificial zinc-finger proteins (AZPs) inhibited virus DNA replication in planta and in mammalian cells by blocking binding of a viral replication protein to its replication origin. However, the replication mechanisms of viruses of interest need to be disentangled for the application. To develop more widely applicable methods for antiviral therapy, we explored the feasibility of inhibition of HPV-18 replication as a model system by cleaving its viral genome. To this end, we fused the staphylococcal nuclease cleaving DNA as a monomer to an AZP that binds to the viral genome. The resulting hybrid nuclease (designated AZP–SNase) cleaved its target DNA plasmid efficiently and sequence-specifically in vitro. Then, we confirmed that transfection with a plasmid expressing AZP–SNase inhibited HPV-18 DNA replication in transient replication assays using mammalian cells. Linker-mediated PCR analysis revealed that the AZP–SNase cleaved an HPV-18 ori plasmid around its binding site. Finally, we demonstrated that the protein-delivered AZP–SNase inhibited HPV-18 DNA replication as well and did not show any significant cytotoxicity. Thus, both gene- and protein-delivered hybrid nucleases efficiently inhibited HPV-18 DNA replication, leading to development of a more universal antiviral therapy for human DNA viruses.

Integrating clinical, community, and policy perspectives on human papillomavirus vaccination

Infection with genital human papillomavirus (HPV) may cause anogenital cancers, oropharyngeal cancers, anogenital warts, and respiratory papillomas. Two prophylactic vaccines (a bivalent and a quadrivalent vaccine) are now licensed and currently in use in a number of countries. Both vaccines prevent infection with HPV-16 and HPV-18, which together cause approximately 70% of cervical cancers, and clinical trials have demonstrated 90%-100% efficacy in preventing precancerous cervical lesions attributable to HPV-16 and HPV-18. One vaccine also prevents HPV-6 and HPV-11, which cause 90% of genital warts. A growing literature describes psychosocial, interpersonal, organizational, and societal factors that influence HPV vaccination acceptability. This review summarizes the current literature and presents an integrated perspective, taking into account these diverse influences. The resulting integrated framework can be used as a heuristic tool for organizing factors at multiple levels to guide intervention development and future research.

Baseline demographic characteristics of subjects enrolled in international quadrivalent HPV (types 6/11/16/18) vaccine clinical trials

BACKGROUND

In Phase II/III trials, administration of quadrivalent human papillomavirus (HPV) (types 6/11/16/18) L1 virus-like-particle vaccine was highly effective in preventing HPV6/11/16/18-related cervical intraepithelial neoplasia and non-invasive cervical cancer in women aged 16-26 years who were naïve to these HPV types at enrollment. However, the makeup and extent of catch-up vaccination programs among young women is unclear, because a proportion of this population will likely already have been exposed to one or more vaccine-HPV-types.

OBJECTIVE

Herein we analyze baseline data from the quadrivalent HPV vaccine clinical trial program to investigate variables which may help shape catch-up vaccine implementation policies.

METHODS

Female adolescents and young adults aged 16-26 years were randomized into five clinical trials. Baseline data regarding demographics, sexual history, pregnancy history, and other characteristics were collected at enrollment. At the baseline gynecological examination during enrollment, specimens were obtained for Pap testing. Swabs of external genital, lateral vaginal, and cervical sites for HPV polymerase chain reaction (PCR) testing were taken, and serum samples were obtained for HPV serology testing. Regional analyses of data were conducted.

RESULTS

Overall, 72% of subjects enrolled worldwide were naïve by both serology and PCR to all four vaccine HPV types. Few subjects were seropositive and/or PCR positive for more than two vaccine-related HPV types. Of all subjects with HSIL at enrollment, 78% were positive to at least one vaccine-related HPV type at enrollment. Regional differences in HPV and STD prevalence were evident. Study limitations included under-representation of women with >/=4 sexual partners and possible underestimation of prior HPV exposure.

CONCLUSIONS

Our findings demonstrate that sexually active 16-26 year-old women with </=4 life time sex partners (LSP) in North America, Europe, Latin America, and Asia Pacific are generally naïve to most or all types targeted by the quadrivalent HPV6/11/16/18 vaccine and that they are at subsequent risk for infection and disease caused by these types.

Efficacy of a prophylactic adjuvanted bivalent L1 virus-like-particle vaccine against infection with human papillomavirus types 16 and 18 in young women: an interim analysis of a phase III double-blind, randomised controlled trial

BACKGROUND

The aim of this interim analysis of a large, international phase III study was to assess the efficacy of an AS04 adjuvanted L1 virus-like-particle prophylactic candidate vaccine against infection with human papillomavirus (HPV) types 16 and 18 in young women.

METHODS

18,644 women aged 15-25 years were randomly assigned to receive either HPV16/18 vaccine (n=9319) or hepatitis A vaccine (n=9325) at 0, 1, and 6 months. Of these women, 88 were excluded because of high-grade cytology and 31 for missing cytology results. Thus, 9258 women received the HPV16/18 vaccine and 9267 received the control vaccine in the total vaccinated cohort for efficacy, which included women who had prevalent oncogenic HPV infections, often with several HPV types, as well as low-grade cytological abnormalities at study entry and who received at least one vaccine dose. We assessed cervical cytology and subsequent biopsy for 14 oncogenic HPV types by PCR. The primary endpoint--vaccine efficacy against cervical intraepithelial neoplasia (CIN) 2+ associated with HPV16 or HPV18--was assessed in women who were seronegative and DNA negative for the corresponding vaccine type at baseline (month 0) and allowed inclusion of lesions with several oncogenic HPV types. This interim event-defined analysis was triggered when at least 23 cases of CIN2+ with HPV16 or HPV18 DNA in the lesion were detected in the total vaccinated cohort for efficacy. Analyses were done on a modified intention-to-treat basis. This trial is registered with the US National Institutes of Health clinical trial registry, number NCT00122681.

FINDINGS

Mean length of follow-up for women in the primary analysis for efficacy at the time of the interim analysis was 14.8 (SD 4.9) months. Two cases of CIN2+ associated with HPV16 or HPV18 DNA were seen in the HPV16/18 vaccine group; 21 were recorded in the control group. Of the 23 cases, 14 (two in the HPV16/18 vaccine group, 12 in the control group) contained several oncogenic HPV types. Vaccine efficacy against CIN2+ containing HPV16/18 DNA was 90.4% (97.9% CI 53.4-99.3; p<0.0001). No clinically meaningful differences were noted in safety outcomes between the study groups.

INTERPRETATION

The adjuvanted HPV16/18 vaccine showed prophylactic efficacy against CIN2+ associated with HPV16 or HPV18 and thus could be used for cervical cancer prevention.

Effect of prophylactic human papillomavirus L1 virus-like-particle vaccine on risk of cervical intraepithelial neoplasia grade 2, grade 3, and adenocarcinoma in situ: a combined analysis of four randomised clinical trials

BACKGROUND

Cervical cancer and its obligate precursors, cervical intraepithelial neoplasia grades 2 and 3 (CIN2/3), and adenocarcinona in situ (AIS), are caused by oncogenic human papillomavirus (HPV). In this combined analysis of four clinical trials we assessed the effect of prophylactic HPV vaccination on these diseases.

METHODS

20,583 women aged 16-26 years were randomised to receive quadrivalent HPV6/11/16/18 vaccine (n=9087), its HPV16 vaccine component (n=1204), or placebo (n=10 292). They underwent periodic Papanicolaou testing, with colposcopy or biopsy for detected abnormalities. The primary composite endpoint was the combined incidence of HPV16/18-related CIN2/3, AIS, or cervical cancer. These trials are registered at ClinicalTrials.gov, numbers NCT00365378, NCT00365716, NCT00092521, and NCT00092534.

FINDINGS

Mean follow-up was 3.0 years (SD 0.66) after first dose. In women negative for HPV16 or HPV18 infection during the vaccination regimen (n=17 129, per protocol), vaccine efficacy was 99% for the primary endpoint (95% CI 93-100), meeting the statistical criterion for success. In an intention-to-treat analysis of all randomised women (including those who were HPV16/18 naive or HPV16/18-infected at day 1), efficacy was 44% (95% CI 31-55); all but one case in vaccine recipients occurred in women infected with HPV16 or HPV18 before vaccination. In a second intention-to-treat analysis we noted an 18% reduction (95% CI 7-29) in the overall rate of CIN2/3 or AIS due to any HPV type.

INTERPRETATION

Administration of HPV vaccine to HPV-naive women, and women who are already sexually active, could substantially reduce the incidence of HPV16/18-related cervical precancers and cervical cancer.

Interference with energy metabolism by 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside induces HPV suppression in cervical carcinoma cells and apoptosis in the absence of LKB1

Carcinogenesis is a dynamic and stepwise process, which is accompanied by a variety of somatic and epigenetic alterations in response to a changing microenvironment. Hypoxic conditions will select for cells that have adjusted their metabolic profile and can maintain proliferation by successfully competing for scarce nutritional and oxygen resources. In the present study we have investigated the effects of energy depletion in the context of HPV (human papillomavirus)-induced pathogenesis. We show that cervical carcinoma cell lines are susceptible to undergoing either growth arrest or cell death under conditions of metabolic stress induced by AICAR (5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside), a known activator of the AMPK (AMP-activated protein kinase). Our results reveal that AICAR treatment leads to a reduced binding affinity of the transcription factor AP-1 (activator protein-1) and in turn to a selective suppression of HPV transcription. Moreover, the outcome of AICAR on proliferation and survival was dependent on p53 activation and the presence of LKB1, the major upstream kinase of AMPK. Using non-malignant LKB1-expressing somatic cell hybrids, which lose expression after tumorigenic segregation, as well as small interfering RNA LKB1 knockdown approaches, we could further demonstrate that expression of LKB1 protects cells from cytotoxicity induced by agents which modulate the ATP/AMP ratio. Since simulation of low energy status can selectively eradicate LKB1-negative cervical carcinoma cells, AICAR may represent a novel drug in the treatment of cervical cancer.

[Transcriptional inhibition of human papilloma virus in cervical carcinoma cells reactivates functions of the tumor suppressor p53]

Inactivation of tumor suppressor p53 accompanies the majority of malignant diseases in humans. Restoration of p53 functions in tumor results in death of cancer cells, which can be used in cancer therapy. In cervical cancer a product of E6 gene of the human papilloma virus promotes accelerated degradation of p53 in proteasome system. Therefore, one of the approaches to reactivation of p53 in cervical carcinoma cells could be the use of small molecules that inhibit functions of viral proteins. By using as a test system human cervical carcinoma cells (HeLa cell line bearing human papilloma virus type 18, HPV-18) with introduced reporter construct that expresses beta-galactosidase under control of a p53-dependent promoter we carried out screening of a library of small molecules to select small molecules capable of reactivating transcriptional activity of p53. We then characterized the effects of two most active compounds in cell lines that differ in the status of p53-dependent signaling pathway. Both of the compounds caused specific activation of p53 in the cell lines expressing HPV-18, to a lesser extent--HPV-16, and do not cause any effect in control p53 negative cells, or in the cells with undisrupted p53 pathway. Activation of p53 in cervical carcinoma cells was accompanied by the induction of the p53-dependent gene CDKN1 (p21), by inhibition of proliferation, and by the induction of apoptosis. Both of the compounds were capable of deep inhibition of transcription from the HPV genome, which apparently was the cause for p53 reactivation in response to decreased expression of the E6 protein. The observed low toxicity for normal cells allows considering these chemical compounds as prototypes for future anticancer drugs.

Heparin (GAG-hed) inhibits LCR activity of human papillomavirus type 18 by decreasing AP1 binding

BACKGROUND

High risk HPVs are causative agents of anogenital cancers. Viral E6 and E7 genes are continuously expressed and are largely responsible for the oncogenic activity of these viruses. Transcription of the E6 and E7 genes is controlled by the viral Long Control Region (LCR), plus several cellular transcription factors including AP1 and the viral protein E2. Within the LCR, the binding and activity of the transcription factor AP1 represents a key regulatory event in maintaining E6/E7 gene expression and uncontrolled cell proliferation. Glycosaminoglycans (GAGs), such as heparin, can inhibit tumour growth; they have also shown antiviral effects and inhibition of AP1 transcriptional activity. The purpose of this study was to test the heparinoid GAG-hed, as a possible antiviral and antitumoral agent in an HPV18 positive HeLa cell line.

METHODS

Using in vivo and in vitro approaches we tested GAG-hed effects on HeLa tumour cell growth, cell proliferation and on the expression of HPV18 E6/E7 oncogenes. GAG-hed effects on AP1 binding to HPV18-LCR-DNA were tested by EMSA.

RESULTS

We were able to record the antitumoral effect of GAG-hed in vivo by using as a model tumours induced by injection of HeLa cells into athymic female mice. The antiviral effect of GAG-hed resulted in the inhibition of LCR activity and, consequently, the inhibition of E6 and E7 transcription. A specific diminishing of cell proliferation rates was observed in HeLa but not in HPV-free colorectal adenocarcinoma cells. Treated HeLa cells did not undergo apoptosis but the percentage of cells in G2/M phase of the cell cycle was increased. We also detected that GAG-hed prevents the binding of the transcription factor AP1 to the LCR.

CONCLUSION

Direct interaction of GAG-hed with the components of the AP1 complex and subsequent interference with its ability to correctly bind specific sites within the viral LCR may contribute to the inhibition of E6/E7 transcription and cell proliferation. Our data suggest that GAG-hed could have antitumoral and antiviral activity mainly by inhibiting AP1 binding to the HPV18-LCR.