A Reverse Structure-based Design of HPV E7 Inhibitor.

BACKGROUND: Human papillomavirus (HPV) is a small, non-enveloped double-stranded circular DNA virus. The high-risk types of HPV are claimed to be responsible for over 99% of cervical cancers. One of the essential HPV oncoproteins, E7, is responsible for escaping from G1/S cell cycle arrest in HPV-infected cells by binding to the retinoblastoma protein (pRb) through its LXCXE binding site. OBJECTIVE: To design a peptide inhibitor targeting HPV E7 through an in silico approach. METHODS: In this study, the LXCXE binding domain of pRb is used as a target to design peptide inhibitors using a reverse structure-based approach. The designed amino acid sequence from the B pocket of pRb, named peptide Y, was further investigated in vitro analysis. The cytotoxicity of the peptide was analysed in two cell lines, namely, CaSki, containing an integrated HPV16 genome, and HaCaT, an immortalized keratinocyte cell. Cell cycle analysis was also carried out in both cell lines treated with peptides. RESULTS: In the in silico approach, a 9-amino acids peptide sequence formed 4 conventional hydrogen bonds with LXCXE motif was selected for in vitro assay. Based on the cytotoxicity analysis, the peptide showed low toxicity in both cell lines, where the cell viability remained over 74% when treated with peptide Y. The peptide also caused an accumulation of cells in G0/G1 (+5.4%) and S phase (+10.2%) and a reduction of cells in the G2/M phase (-14.9%) in the CaSki cells with no significant effect on normal cells, indicating it is a potential HPV inhibitor. CONCLUSION: A peptide inhibitor, peptide Y, that was designed from the LXCXE binding motif in pRb can inhibit HPV E7 by causing a cell accumulation effect in G0/G1, and S phases of the cell cycle in the HPV transformed cell lines. These findings could contribute to HPV E7 peptide inhibitor in the future.

Attenuated Salmonella carrying plasmid co-expressing HPV16 L1 and siRNA-E6 for cervical cancer therapy.

Human papillomavirus (HPV) infection is the major etiological factor for cervical cancer. HPV prophylactic vaccines based on L1 virus-like particles have been considered as an effective prevention method. However, existing recombination vaccines are too expensive for developing countries. DNA vaccines might be a lower-cost and effective alternative. In this study, a plasmid (pcDNA3.1-HPV16-L1) and a co-expressing plasmid (pcDNA3.1-HPV16-L1-siE6) carried by attenuated Salmonella were constructed and their prevention and treatment effect on cervical cancer were observed, respectively. The results showed that pcDNA3.1-HPV16-L1 carried by attenuated Salmonella could induce the production of HPV16-L1 antibodies, IL-2 and INF-γ in mice serum, which presented its prevention effect on HPV. Subsequently, E6 and E7 gene silencing by pCG-siE6 inhibited the growth of cervical cancer both in vitro and in vivo. Furthermore, L1 up-regulation and E6/E7 down-regulation caused by co-expressing plasmid (pcDNA3.1-HPV16-L1-siE6) contributed to a significant anti-tumor effect on the mice. This study suggests that pcDNA3.1-HPV16-L1-siE6 carried by attenuated Salmonella has a synergistic effect of immune regulation and RNA interference in cervical cancer treatment.

A therapeutic HPV16 E7 vaccine in combination with active anti-FGF-2 immunization synergistically elicits robust antitumor immunity in mice.

FGF-2 accumulates in many tumor tissues and is closely related to the development of tumor angiogenesis and the immunosuppressive microenvironment. This study aimed to investigate whether active immunization against FGF-2 could modify antitumor immunity and enhance the efficacy of an HPV16 E7-specific therapeutic vaccine. Combined immunization targeting both FGF-2 and E7 significantly suppressed tumor growth, which was accompanied by significantly increased levels of IFN-γ-expressing splenocytes and effector CD8 T cells and decreased levels of immunosuppressive cells such as regulatory T cells (Tregs) and myeloid-derived suppressor cells(MDSCs) in both the spleen and tumor; in addition, the levels of FGF-2 and neovascularization in tumors were decreased in the mice receiving the combined immunization, and tumor cell apoptosis was promoted. The combination of an HPV16 E7-specific vaccine and active immunization against FGF-2 significantly enhances antitumor immune responses in mice with TC-1 tumors, indicating a promising strategy for tumor immunotherapy.

Structural dynamic studies on identification of EGCG analogues for the inhibition of Human Papillomavirus E7.

High risk human papillomaviruses are highly associated with the cervical carcinoma and the other genital tumors. Development of cervical cancer passes through the multistep process initiated from benign cyst to increasingly severe premalignant dysplastic lesions in an epithelium. Replication of this virus occurs in the fatal differentiating epithelium and involves in the activation of cellular DNA replication proteins. The oncoprotein E7 of human papillomavirus expressed in the lower epithelial layers constrains the cells into S-phase constructing an environment favorable for genome replication and cell proliferation. To date, no suitable drug molecules exist to treat HPV infection whereas anticipation of novel anti-HPV chemotherapies with distinctive mode of actions and identification of potential drugs are crucial to a greater extent. Hence, our present study focused on identification of compounds analogue to EGCG, a green tea molecule which is considered to be safe to use for mammalian systems towards treatment of cancer. A three dimensional similarity search on the small molecule library from natural product database using EGCG identified 11 potential small molecules based on their structural similarity. The docking strategies were implemented with acquired small molecules and identification of the key interactions between protein and compounds were carried out through binding free energy calculations. The conformational changes between the apoprotein and complexes were analyzed through simulation performed thrice demonstrating the dynamical and structural effects of the protein induced by the compounds signifying the domination. The analysis of the conformational stability provoked us to describe the features of the best identified small molecules through electronic structure calculations. Overall, our study provides the basis for structural insights of the identified potential identified small molecules and EGCG. Hence, the identified analogue of EGCG can be potent inhibitors against the HPV 16 E7 oncoprotein.

Effects of the antifungal agent ciclopirox in HPV-positive cancer cells: Repression of viral E6/E7 oncogene expression and induction of senescence and apoptosis.

The malignant growth of human papillomavirus (HPV)-positive cancer cells is dependent on the continuous expression of the viral E6/E7 oncogenes. Here, we examined the effects of iron deprivation on the phenotype of HPV-positive cervical cancer cells. We found that iron chelators, such as the topical antifungal agent ciclopirox (CPX), strongly repress HPV E6/E7 oncogene expression, both at the transcript and protein level. CPX efficiently blocks the proliferation of HPV-positive cancer cells by inducing cellular senescence. Although active mTOR signaling is considered to be critical for the cellular senescence response towards a variety of prosenescent agents, CPX-induced senescence occurs under conditions of severely impaired mTOR signaling. Prolonged CPX treatment leads to p53-independent Caspase-3/7 activation and induction of apoptosis. CPX also eliminates HPV-positive cancer cells under hypoxic conditions through induction of apoptosis. Taken together, these results show that iron deprivation exerts profound antiviral and antiproliferative effects in HPV-positive cancer cells and suggest that iron chelators, such as CPX, possess therapeutic potential as HPV-inhibitory, prosenescent and proapoptotic agents in both normoxic and hypoxic environments.

VERU-111 suppresses tumor growth and metastatic phenotypes of cervical cancer cells through the activation of p53 signaling pathway.

In this study, we investigated the therapeutic efficacy of VERU-111 in vitro and in vivo model systems of cervical cancer. VERU-111 treatment inhibited cell proliferation and, clonogenic potential, induce accumulation of p53 and down regulated the expression of HPV E6/E7 expression in cervical cancer cells. In addition, VERU-111 treatment also decreased the phosphorylation of Jak2(Tyr1007/1008) and STAT3 at Tyr705 and Ser727. VERU-111 treatment arrested cell cycle in the G2/M phase and modulated cell cycle regulatory proteins (cyclin B1, p21, p34cdc2 and pcdk1). Moreover, VERU-111 treatment induced apoptosis and modulated the expression of Bid, Bcl-xl, Survivin, Bax, Bcl2 and cleavage in PARP. In functional assays, VERU-111 markedly reduced the migratory and invasive potential of cervical cancer cells via modulations of MMPs. VERU-111 treatment also showed significant (P < 0.05) inhibition of orthotopic xenograft tumor growth in athymic nude mice. Taken together, our results demonstrate the potent anti-cancer efficacy of VERU-111 in experimental cervical cancer models.Thus, VERU-111 can be explored as a promising therapeutic agent for the treatment of cervical cancer.

Cervical cancer and HPV infection: ongoing therapeutic research to counteract the action of E6 and E7 oncoproteins.

Cervical cancer is the fourth most common cancer among women worldwide and its development is mainly associated with human papillomavirus infection, a highly sexually transmissible virus. The expression of E6 and E7 viral oncoproteins deregulates cell repairing mechanisms through impairment of tumor suppressor protein functions, such as p53 or retinoblastoma protein. Although the implementation of new preventive vaccines has decreased the infection rate and cervical cancer progression, there are still many women who are affected by this pathology. Nowadays, the main treatment often requires the use of invasive techniques. From well-established strategies, like DNA vaccines and gene therapy, to innovative gene silencing technologies; different methodologies are currently under scrutiny that target the E6 and E7 oncoproteins and/or their modes of action.

REBACIN® as a noninvasive clinical intervention for high-risk human papillomavirus persistent infection.

The development of highly sensitive HPV-genotyping tests has opened the possibility of treating HPV-infected women before high-grade lesions appear. The lack of efficient intervention for persistent high-risk HPV infection necessitates the need for development of novel therapeutic strategy. Here we demonstrate that REBACIN®, a proprietary antiviral biologics, has shown potent efficacy in the clearance of persistent HPV infections. Two independent parallel clinical studies were investigated, which a total of 199 patients were enrolled and randomly divided into a REBACIN®-test group and a control group without treatment. The viral clearance rates for the REBACIN® groups were 61.5% (24/39) and 62.5% (35/56), respectively, for the two independent parallel studies. In contrast, the nontreatment groups showed self-clearance rates at 20.0% (8/40) and 12.5% (8/64). We further found that REBACIN® was able to significantly repress the expression of HPV E6 and E7 oncogenes in TC-1 and Hela cells. The two viral genes are well known for the development of high-grade premalignancy lesion and cervical cancer. In a mouse model, REBACIN® was indicated to notably suppress E6/E7-induced tumor growth, suggesting E6 and E7 oncogenes as a potential target of REBACIN®. Taken together, our studies shed light into the development of a novel noninvasive therapeutic intervention for clearance of persistent HPV infection with significant efficacy.

Nanobody against the E7 oncoprotein of human papillomavirus 16.

The persistent infection of high-risk human papillomavirus (HPV) is one of the most common causes of cervical cancer. It is well documented that expression of two oncogenes (E6/E7) plays a key role in tumor progression. HPV16E7 -targeting via nanobody (Nb) therefore could be beneficial for HPV16-associated cancer diagnosis and therapy. In this work, phage-display approach was employed to select the high affinity HPV16E7-specific Nb. Firstly; a high-quality immune library was constructed. After three round of biopanning, high-affinity HPV16 E7-specific nanobodies were retrieved. By phage ELISA and sequencing, four different sequences of anti- HPV16E7 nanobodies were selected. Then recombinant nanobody Nb2 was cloned and expressed in E. coli, and the specificity and thermal stability of purified Nb2 was evaluated. To examine the potential of Nb2 as an inhibitor of E7 function, Nb2 was expressed within HPV16 positive cells. Proliferation assay showed that the intracellular expressed Nb2 as an intrabody can decrease the growth of HPV16-positive cells. The results indicate that Nb2 as an intracellular antibody directed towards HPV oncoprotein E7 has great promise in applications for the therapy of HPV16-associated disease.

Immunotherapy Targeting HPV16/18 Generates Potent Immune Responses in HPV-Associated Head and Neck Cancer.

PURPOSE: Clinical responses with programmed death (PD-1) receptor-directed antibodies occur in about 20% of patients with advanced head and neck squamous cell cancer (HNSCCa). Viral neoantigens, such as the E6/E7 proteins of HPV16/18, are attractive targets for therapeutic immunization and offer an immune activation strategy that may be complementary to PD-1 inhibition. PATIENTS AND METHODS: We report phase Ib/II safety, tolerability, and immunogenicity results of immunotherapy with MEDI0457 (DNA immunotherapy targeting HPV16/18 E6/E7 with IL12 encoding plasmids) delivered by electroporation with CELLECTRA constant current device. Twenty-two patients with locally advanced, p16+ HNSCCa received MEDI0457. RESULTS: MEDI0457 was associated with mild injection site reactions, but no treatment-related grade 3-5 adverse events (AE) were noted. Eighteen of 21 evaluable patients showed elevated antigen-specific T-cell activity by IFNγ ELISpot, and persistent cellular responses surpassing 100 spot-forming units (SFUs)/106 peripheral blood mononuclear cells (PBMCs) were noted out to 1 year. Induction of HPV-specific CD8+ T cells was observed. MEDI0457 shifted the CD8+/FoxP3+ ratio in 4 of 5 post immunotherapy tumor samples and increased the number of perforin+ immune infiltrates in all 5 patients. One patient developed metastatic disease and was treated with anti-PD-1 therapy with a rapid and durable complete response. Flow-cytometric analyses revealed induction of HPV16-specific PD-1+ CD8+ T cells that were not found prior to MEDI0547 (0% vs. 1.8%). CONCLUSIONS: These data demonstrate that MEDI0457 can generate durable HPV16/18 antigen-specific peripheral and tumor immune responses. This approach may be used as a complementary strategy to PD-1/PD-L1 inhibition in HPV-associated HNSCCa to improve therapeutic outcomes.

Nanoparticles Based on Poly (ß-Amino Ester) and HPV16-Targeting CRISPR/shRNA as Potential Drugs for HPV16-Related Cervical Malignancy.

Persistent high-risk HPV infection is the main cause of cervical cancer. The HPV oncogene E7 plays an important role in HPV carcinogenesis. Currently, HPV vaccines do not offer an effective treatment for women who already present with cervical disease, and recommended periodical cervical screenings are difficult to perform in countries and areas lacking medical resources. Our aim was to develop nanoparticles (NPs) based on poly (ß-amino ester) (PBAE) and HPV16 E7-targeting CRISPR/short hairpin RNA (shRNA) to reduce the levels of HPV16 E7 as a preliminary form of a drug to treat HPV infection and its related cervical malignancy. Our NPs showed low toxicity in cells and mouse organs. By reducing the expression of HPV16 E7, our NPs could inhibit the growth of cervical cancer cells and xenograft tumors in nude mice, and they could reverse the malignant cervical epithelium phenotype in HPV16 transgenic mice. The performance of NPs containing shRNA is better than that of NPs containing CRISPR. HPV-targeting NPs consisting of PBAE and CRISPR/shRNA could potentially be developed as drugs to treat HPV infection and HPV-related cervical malignancy.

A novel HPV16 E7-affitoxin for targeted therapy of HPV16-induced human cervical cancer.

Cervical cancer, the second most common cause of cancer death in women worldwide, is significantly associated with infection of high-risk human papillomaviruses (HPVs), especially the most common genotype, HPV 16. To date, there is no established noninvasive therapy to treat cervical cancer. Methods: Here, we report a novel affitoxin that targets HPV16 E7 protein, one of the primary target proteins in molecular targeted therapy for HPV-induced cervical cancer. The affitoxin, ZHPV16E7 affitoxin384 was generated by fusing the modified Pseudomonas Exotoxin A (PE38KDEL) to the HPV16 E7-specific affibody. The expressed and purified ZHPV16E7 affitoxin384 was characterized using numerous methods. SPR assay, indirect immunofluorescence assay, and near-infrared (NIR) optical imaging were respectively performed to assess the targeting ability of ZHPV16E7 affitoxin384 to HPV16 E7 protein both in vitro and in vivo. Cell viability assays and SiHa tumor-bearing nude mice were used to evaluate the efficacy of ZHPV16 E7 affitoxin384 in vitro and in vivo, respectively. Results: Using in vitro methods the SPR assay and indirect immunofluorescence assay showed that ZHPV16E7 affitoxin384 targeted HPV16 E7 with high binding affinity and specificity. Significant reduction of cell viability in HPV16 positive cells was observed in the presence of ZHPV16 E7 affitoxin384. By NIR optical imaging, ZHPV16 E7 affitoxin384 specifically targeted HPV16 positive tumors in vivo. ZHPV16E7 affitoxin384 showed significant in vivo antitumor efficacy in two kinds of tumor-bearing nude mouse models. Conclusions: ZHPV16E7 affitoxin384 is a potent anti-cervical cancer therapeutic agent that could be effective against HPV16 positive tumors in humans.

Adenovirus-mediated transfer of HPV 16 E6/E7 antisense RNA combined with cisplatin inhibits cellular growth and induces apoptosis in HPV-positive head and neck cancer cells.

Human papillomavirus (HPV) infection has been identified as an etiologic factor of head and neck cancers (HNCs). We explored the potential use of antisense HPV RNA transcripts for gene therapy and its effect in combination with cisplatin (CDDP) for HPV-positive HNCs. We introduced the antisense RNA transcripts of the E6 and E7 genes of HPV type 16 into UM-SCC-47 cells harboring HPV 16 and YCU-T892 cells that were HPV-negative using a recombinant adenoviral vector, Ad-E6/E7-AS. We then analyzed the effects of the introduction of Ad-E7-AS on cell and tumor growth and the synergistic effect with CDDP in vitro and in vivo. After infection of Ad-E6/E7-AS, the cellular growth of UM-SCC-47 cells were suppressed, but not that of YCU-T892 cells. E7 protein expression was suppressed, and p53 and pRb protein expression increased after infection of Ad-E7-AS. Cell growth and tumorigenicity were greatly suppressed in combination with CDDP compared with Ad-E7-AS or CDDP treatment alone in vitro. Ad-E7-AS combined with CDDP treatment significantly reduced the volumes of established subcutaneous tumors. Transfection with HPV 16 E7 antisense RNA combined with CDDP treatment might be a potentially useful approach to the therapy of HPV 16-positive HNC.

E7 oncoprotein of human papillomavirus: Structural dynamics and inhibitor screening study.

Human papillomavirus (HPV) has been the primary causative agent of cervical cancer, the most threatening cancer affecting millions of women worldwide. HPV, a small non enveloped DNA virus of high and low risk types contain intrinsically disordered region and it also plays significant role in the development of cervical cancer. HPV E7 contains an ordered Zinc finger motif that binds to pRB and alters its function. It utilizes both disordered N-terminal and structured C-terminal regions for cellular transformation. In this study, we have focused extensively on the evolutionary relationships of E7 among various HPV types and generated a 3D homology model of full length HPV 16 E7, since the structure have not been solved till date. We also analysed the stable conformation and atomic flexibility of modelled E7 through molecular dynamics simulation at 100 ns. To understand the disordered based binding sites of E7 oncoprotein, Molecular recognition features (MoRFs) analysis was carried out on the E7 oncoprotein. The validated model was taken forward for the identification of potential lead compounds and the most prominent compounds were selected for the molecular dynamics simulation of the 100 ns for the stability analysis. Overall, this study highlights the holistic E7 regions including important disordered based binding sites analysed through the MoRFs. The potential inhibitor compound that targets the structured C-terminal region of E7 oncoprotein were subjected for the pharmacological properties analysis and further validated for the binding modes of the compounds with the target structure. This study helps in providing a better intuition to develop a potent anti-HPV agent.

3-(2-Chloropropyl amide)-4-methoxy-N-phenylbenzamide inhibits expression of HPV oncogenes in human cervical cancer cell.

BACKGROUND: Human papillomaviruses (HPVs) are the primary causative agents for cervical cancer, and HPV oncoproteins E6 and E7 are known to be the main reason for the onset and maintenance of the malignancies. Therefore, inhibition of viral E6 and E7 oncoproteins expression represents a viable strategy to cervical cancer therapies. This study is to evaluate the antiviral effect of a novel N-Phenylbenzamide derivative, 3-(2-Chloropropyl amide)-4-methoxy-N-phenylbenzamide (L17), against HPV16 in vitro and identify its associated mechanism of action in cervical cancer cells. METHODS: The cytotoxic effect of L17 was assessed by MTT assay. The mRNA and protein levels of E6 and E7 oncogenes were analyzed by quantitative real-time reverse transcription PCR (qRT-PCR) and Western blot, respectively. p53 and Rb protein levels were also detected by Western blot. The effect of L17 on cell cycle was analyzed by flow cytometry. RESULTS: The cytotoxic effect of L17 was greater in cervical carcinoma cells than in normal cells. L17 significantly reduced the expression of HPV16 E6 and E7 mRNA and protein, at least partly by enhancing degradation of HPV16 E6 and E7 mRNA. Moreover, reduced expression of E6 and E7 induced by L17 resulted in the up-regulation of p53 and Rb expression, which subsequently induced CaSki cells arrest at G0/G1 phase. CONCLUSIONS: L17 has antiviral activity through suppressing E6 and E7 oncogene expression and could inhibit CaSki cell proliferating by inducing cells arrest at G0/G1 phase at nontoxic concentration, implying that L17 might be exploited as a candidate agent for HPV-associated cervical cancer prevention and treatment.

Human papillomavirus oncoproteins differentially modulate epithelial-mesenchymal transition in 5-FU-resistant cervical cancer cells.

Etiological role of viral proteins E6 and E7 of high-risk HPV in cervical carcinogenesis is well established. However, their contribution in chemoresistance and epithelial-mesenchymal transition (EMT) that leads to advanced metastatic lesions and chemoresistance is poorly defined. In the present study, contribution of viral oncoproteins in acquisition of EMT character during onset of chemoresistance was assessed. A chemoresistant cell line (SiHaCR) was developed from an established HPV16-positive cervical cancer cell line, SiHa, by escalating selection pressure of 5-fluorouracil (5-FU). Expression of Survivin, ABCG2, Snail, Slug, Twist, and Vimentin was examined in SiHa and SiHaCR cells by reverse transcriptase-PCR (RT-PCR) and immunoblotting assays. Mesenchymal phenotype in SiHaCR cells was confirmed by assessment of migration and invasion potentials. SiHaCR cells displayed elevated level of functional and molecular markers associated with chemoresistance (Survivin, ABCG2) and EMT (Snail, Slug, Twist, Vimentin) and reduced E-cadherin. SiHaCR also showed increased levels of HPV16 E6 and E7 transcripts. Specific silencing of HPV16 E6, but not E7 using corresponding siRNA, demonstrated a differential involvement of HPV oncogenes in manifestation of EMT. HPV16 E6 silencing resulted in reduction of Slug and Twist expression. However, the expression of Snail and Vimentin was only marginally affected. In contrast, there was an increase in the expression of E-cadherin. A reduced migration and invasion capabilities were observed only in E6-silenced SiHaCR cells, which further confirmed functional contribution of HPV16 E6 in manifestation of EMT. Taken together, our study demonstrated an active involvement of HPV16 E6 in regulation of EMT, which promotes chemoresistance in cervical cancer.

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 ß-galactosidase (SA-ß-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.

Disruption of HPV16-E7 by CRISPR/Cas system induces apoptosis and growth inhibition in HPV16 positive human cervical cancer cells.

High-risk human papillomavirus (HR-HPV) has been recognized as a major causative agent for cervical cancer. Upon HPV infection, early genes E6 and E7 play important roles in maintaining malignant phenotype of cervical cancer cells. By using clustered regularly interspaced short palindromic repeats- (CRISPR-) associated protein system (CRISPR/Cas system), a widely used genome editing tool in many organisms, to target HPV16-E7 DNA in HPV positive cell lines, we showed for the first time that the HPV16-E7 single-guide RNA (sgRNA) guided CRISPR/Cas system could disrupt HPV16-E7 DNA at specific sites, inducing apoptosis and growth inhibition in HPV positive SiHa and Caski cells, but not in HPV negative C33A and HEK293 cells. Moreover, disruption of E7 DNA directly leads to downregulation of E7 protein and upregulation of tumor suppressor protein pRb. Therefore, our results suggest that HPV16-E7 gRNA guided CRISPR/Cas system might be used as a therapeutic strategy for the treatment of cervical cancer.

Novel action modality of the diterpenoid anisomelic acid causes depletion of E6 and E7 viral oncoproteins in HPV-transformed cervical carcinoma cells.

Cervical cancer, the second most common malignancy among women, is mainly caused by human papilloma virus (HPV) infection. In HPV-positive cervical cancer cells, the activity of p53 and the induction of p21 are inhibited by the HPV oncoproteins E6 and E7. Therefore, blocking the activity of E6 and E7 would serve as an important therapeutic target in these cancer cells. In this study, anisomelic acid (AA), a natural compound belonging to the same diterpenoid family of bioactive compounds as taxol, was found to deplete the E6 and E7 proteins in HPV-positive cervical cancer cells. Consequently, p53 and the p53-responsive gene, p21, were dramatically induced, leading to G2/M-phase cell cycle arrest. AA-mediated cell cycle arrest and p21 expression were canceled when p53 was down-regulated by p53-shRNA. AA also induced p53-independent intrinsic apoptosis by depletion of the cellular inhibitor of apoptosis protein 2 (cIAP2) whose proteosomal degradation is inhibited by E6. The in ovo chick embryo chorioallantoic membrane (CAM) assay showed that anisomelic acid inhibited the tumor growth of the cervical cancer SiHa cells. AA is revealed to hold a novel action modality based on specific targeting of the HPV oncoproteins, which restores p53-mediated growth arrest and induces apoptosis by terminating E6-mediated cIAP2 stabilization.

In vivo antitumor effect of an intracellular single-chain antibody fragment against the E7 oncoprotein of human papillomavirus 16.

Human papillomavirus (HPV)-associated tumors still represent an urgent problem of public health in spite of the efficacy of the prophylactic HPV vaccines. Specific antibodies in single-chain format expressed as intracellular antibodies (intrabodies) are valid tools to counteract the activity of target proteins. We previously showed that the M2SD intrabody, specific for the E7 oncoprotein of HPV16 and expressed in the endoplasmic reticulum of the HPV16-positive SiHa cells, was able to inhibit cell proliferation. Here, we showed by confocal microscopy that M2SD and E7 colocalize in the endoplasmic reticulum of SiHa cells, suggesting that the E7 delocalization mediated by M2SD could account for the anti-proliferative activity of the intrabody. We then tested the M2SD antitumor activity in two mouse models for HPV tumors based respectively on TC-1 and C3 cells. The M2SD intrabody was delivered by retroviral vector to tumor cells before cell injection into C57BL/6 mice. In both models, a marked delay of tumor onset with respect to the controls was observed in all the mice injected with the M2SD-expressing tumor cells and, importantly, a significant percentage of mice remained tumor-free permanently. This is the first in vivo demonstration of the antitumor activity of an intrabody directed towards an HPV oncoprotein. We consider that these results could contribute to the development of new therapeutic molecules based on antibodies in single-chain format, to be employed against the HPV-associated lesions even in combination with other drugs.