The synergistic therapeutic effect of cisplatin with Human papillomavirus E6/E7 short interfering RNA on cervical cancer cell lines in vitro and in vivo

Probing the Effects of Retinoblastoma Binding Protein 6 (RBBP6) Knockdown on the Sensitivity of Cisplatin in Cervical Cancer Cells

Cervical cancer is a major cause of death in women despite the advancement of current treatment modalities. The conventional therapeutic agent, cisplatin (CCDP), is the standard treatment for CC; however, resistance often develops due to the cancer's heterogeneity. Therefore, a detailed elucidation of the specific molecular mechanisms driving CC is crucial for the development of targeted therapeutic strategies. Retinoblastoma binding protein 6 (RBBP6) is a potential biomarker associated with cell proliferation and is upregulated in cervical cancer sites, exhibiting apoptosis and dysregulated p53 expression. Furthermore, RBBP6 has been demonstrated to sensitize cancer cells to radiation and certain chemotherapeutic agents by regulating the Bcl-2 gene, thus suggesting a crosstalk among RBBP6/p53/BCL-2 oncogenic signatures. The present study, therefore, investigated the relationship between cisplatin and RBBP6 expression in CC cells. Herein, we first explored bioinformatics simulations and identified that the RBBP6/p53/BCL-2 signaling pathway is overexpressed and correlated with CC. For further analysis, we explored the Genomics of Drug Sensitivity in Cancer (GDSC) and found that most of the CC cell lines are sensitive to CCDP. To validate these findings, RBBP6 was silenced in HeLa and Vero cells using RNAi technology, followed by measurement of wild-type p53 and Bcl-2 at the mRNA level using qPCR. Cells co-treated with cisplatin and siRBBP6 were subsequently analyzed for apoptosis induction and real-time growth monitoring using flow cytometry and the xCELLigence system, respectively. Cancer cells in the co-treatment group showed a reduction in apoptosis compared to the cisplatin-treated group. Moreover, the real-time growth monitoring revealed a reduced growth rate in RBBP6 knockdown cells treated with cisplatin. Although wild-type p53 remained unchanged in the co-treatment group of cancer cells, Bcl-2 was completely repressed, suggesting that RBBP6 is necessary for sensitizing cervical cancer cells to cisplatin treatment by downregulating Bcl-2. The Vero cell population, which served as a non-cancerous control cell line in this study, remained viable following treatment with both siRBBP6 and cisplatin. Findings from this study suggest that RBBP6 expression promotes cisplatin sensitivity in HeLa cells through Bcl-2 downregulation. Knockdown of RBBP6 limits apoptosis induction and delays cell growth inhibition in response to cisplatin. The knowledge obtained here has the potential to help improve cisplatin efficacy through personalized administration based on the expression profile of RBBP6 among individual patients.

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.

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.

The Antitumor Efficiency of Zinc Finger Nuclease Combined with Cisplatin and Trichostatin A in Cervical Cancer Cells

BACKGROUND

Persistent infection with the high-risk of human papillomavirus (HR-HPVs) is the primary etiological factor of cervical cancer; HR-HPVs express oncoproteins E6 and E7, both of which play key roles in the progression of cervical carcinogenesis. Zinc Finger Nucleases (ZFNs) targeting HPV E7 induce specific shear of the E7 gene, weakening the malignant biological effects, hence showing great potential for clinical transformation.

OBJECTIVE

Our aim was to develop a new comprehensive therapy for better clinical application of ZFNs. We here explored the anti-cancer efficiency of HPV targeted ZFNs combined with a platinum-based antineoplastic drug Cisplatin (DDP) and an HDAC inhibitor Trichostatin A (TSA).

METHODS

SiHa and HeLa cells were exposed to different concentrations of DDP and TSA; the appropriate concentrations for the following experiments were screened according to cell apoptosis. Then cells were grouped for combined or separate treatments; apoptosis, cell viability and proliferation ability were measured by flow cytometry detection, CCK-8 assays and colony formation assays. The xenograft experiments were also performed to determine the anti-cancer effects of the combined therapy. In addition, the HPV E7 and RB1 expressions were measured by western blot analysis.

RESULTS

Results showed that the combined therapy induced about two times more apoptosis than that of ZFNs alone in SiHa and HeLa cells, and much more inhibition of cell viability than either of the separate treatment. The colony formation ability was inhibited more than 80% by the co-treatment, the protein expression of HPV16/18E7 was down regulated and that of RB1 was elevated. In addition, the xenografts experiment showed a synergistic effect between DDP and TSA together with ZFNs.

CONCLUSION

Our results demonstrated that ZFNs combined with DDP or TSA functioned effectively in cervical cancer cells, and it provided novel ideas for the prevention and treatment of HPV-related cervical malignancies.

Novel Affibody Molecules Targeting the HPV16 E6 Oncoprotein Inhibited the Proliferation of Cervical Cancer Cells

Despite prophylactic vaccination campaigns, high-risk human papillomavirus (HPV)-induced cervical cancer remains a significant health threat among women, especially in developing countries. The initial occurrence and consequent progression of this cancer type primarily rely on, E6 and E7, two key viral oncogenes expressed constitutively, inducing carcinogenesis. Thus, E6/E7 have been proposed as ideal targets for HPV-related cancer diagnosis and treatment. In this study, three novel HPV16 E6-binding affibody molecules (Z_HPV16E61115, Z_HPV16E61171, and Z_HPV16E61235) were isolated from a randomized phage display library and cloned for bacterial production. These affibody molecules showed high binding affinity and specificity for recombinant and native HPV16 E6 as determined by surface plasmon resonance, indirect immunofluorescence, immunohistochemistry, and near-infrared small animal optical imaging in vitro and in vivo. Moreover, by binding to HPV16 E6 protein, Z_HPV16E61235 blocked E6-mediated p53 degradation, which increased the expression of some key p53 target genes, including BAX, PUMA and p21, and thereby selectively reduced the viability and proliferation of HPV16-positive cells. Importantly, Z_HPV16E61235 was applied in combination with HPV16 E7-binding affibody Z_HPV16E7384 to simultaneously target the HPV16 E6/E7 oncoproteins, and this combination inhibited cell proliferation more potently than either modality alone. Mechanistic studies revealed that the synergistic antiproliferative activity depends primarily on the induction of cell apoptosis and senescence but not cell cycle arrest. Our findings provide strong evidence that three novel HPV16 E6-binding affibody molecules could form a novel basis for the development of rational strategies for molecular imaging and targeted therapy in HPV16-positive preneoplastic and neoplastic lesions.

PPI Modulators of E6 as Potential Targeted Therapeutics for Cervical Cancer: Progress and Challenges in Targeting E6

Advanced cervical cancer is primarily managed using cytotoxic therapies, despite evidence of limited efficacy and known toxicity. There is a current lack of alternative therapeutics to treat the disease more effectively. As such, there have been more research endeavors to develop targeted therapies directed at oncogenic host cellular targets over the past 4 decades, but thus far, only marginal gains in survival have been realized. The E6 oncoprotein, a protein of human papillomavirus origin that functionally inactivates various cellular antitumor proteins through protein–protein interactions (PPIs), represents an alternative target and intriguing opportunity to identify novel and potentially effective therapies to treat cervical cancer. Published research has reported a number of peptide and small-molecule modulators targeting the PPIs of E6 in various cell-based models. However, the reported compounds have rarely been well characterized in animal or human subjects. This indicates that while notable progress has been made in targeting E6, more extensive research is needed to accelerate the optimization of leads. In this review, we summarize the current knowledge and understanding of specific E6 PPI inhibition, the progress and challenges being faced, and potential approaches that can be utilized to identify novel and potent PPI inhibitors for cervical cancer treatment.

Chapter XX Antiviral Treatment and Cancer Control

Hepatitis B virus (HBV), hepatitis C virus (HCV), human papilloma virus (HPV), Epstein-Barr virus (EBV), human T-cell lymphotropic virus type 1 (HTLV-1), Kaposi's sarcoma-associated herpesvirus (KSHV), and Merkel cell polyomavirus (MCV) contribute to about 10-15% global burden of human cancers. Conventional chemotherapy or molecular target therapies have been used to treat virus-associated cancers. However, a more proactive approach would be the use of antiviral treatment to suppress or eliminate viral infections to prevent the occurrence of cancer in the first place. Antiviral treatments against chronic HBV and HCV infection have achieved this goal, with significant reduction in the incidence of hepatocellular carcinoma in treated patients. Antiviral treatments for EBV, KSHV, and HTLV-1 had limited success in treating refractory EBV-associated lymphoma and post-transplant lymphoproliferative disorder, KSHV-associated Kaposi's sarcoma in AIDS patients, and HTLV-1-associated acute, chronic, and smoldering subtypes of adult T-cell lymphoma, respectively. Therapeutic HPV vaccine and RNA interference-based therapies for treating HPV-associated infection or cervical cancers also showed some encouraging results. Taken together, antiviral therapies have yielded promising results in cancer prevention and treatment. More large-scale studies in a real-world setting are necessary to confirm the efficacy of antiviral therapy. Further investigation for more effective and convenient antiviral regimens warrants more attention.

Metallodrugs are unique: opportunities and challenges of discovery and development

Metals play vital roles in nutrients and medicines and provide chemical functionalities that are not accessible to purely organic compounds. At least 10 metals are essential for human life and about 46 other non-essential metals (including radionuclides) are also used in drug therapies and diagnostic agents. These include platinum drugs (in 50% of cancer chemotherapies), lithium (bipolar disorders), silver (antimicrobials), and bismuth (broad-spectrum antibiotics). While the quest for novel and better drugs is now as urgent as ever, drug discovery and development pipelines established for organic drugs and based on target identification and high-throughput screening of compound libraries are less effective when applied to metallodrugs. Metallodrugs are often prodrugs which undergo activation by ligand substitution or redox reactions, and are multi-targeting, all of which need to be considered when establishing structure-activity relationships. We focus on early-stage in vitro drug discovery, highlighting the challenges of evaluating anticancer, antimicrobial and antiviral metallo-pharmacophores in cultured cells, and identifying their targets. We highlight advances in the application of metal-specific techniques that can assist the preclinical development, including synchrotron X-ray spectro(micro)scopy, luminescence, and mass spectrometry-based methods, combined with proteomic and genomic (metallomic) approaches. A deeper understanding of the behavior of metals and metallodrugs in biological systems is not only key to the design of novel agents with unique mechanisms of action, but also to new understanding of clinically-established drugs.

Is viral E6 oncoprotein a viable target? A critical analysis in the context of cervical cancer

An understanding of the pathology of cervical cancer (CC) mediated by E6/E7 oncoproteins of high-risk human papillomavirus (HPV) was developed by late 80's. But if we look at the present scenario, not a single drug could be developed to inhibit these oncoproteins and in turn, be used specifically for the treatment of CC. The readers are advised not to presume the "viability of E6 protein" as mentioned in the title relates to just druggability of E6. The viability aspect will cover almost everything a researcher should know to develop E6 inhibitors until the preclinical stage. Herein, we have analysed the achievements and shortcomings of the scientific community in the last four decades in targeting HPV E6 against CC. Role of all HPV proteins has been briefly described for better perspective with a little detailed discussion of the role of E6. We have reviewed the articles from 1985 onward, reporting in vitro inhibition of E6. Recently, many computational studies have reported potent E6 inhibitors and these have also been reviewed. Subsequently, a critical analysis has been reported to cover the in vitro assay protocols and in vivo models to develop E6 inhibitors. A paragraph has been devoted to the role of public policy to fight CC employing vaccines and whether the vaccine against HPV has quenched the zeal to develop drugs against it. The review concludes with the challenges and the way forward.

The Targeting of RNA Polymerase I Transcription Using CX-5461 in Combination with Radiation Enhances Tumour Cell Killing Effects in Human Solid Cancers

An increased rate of cellular proliferation is a hallmark of cancer and may be accompanied by an increase in ribosome biogenesis and dysregulation in rRNA synthesis. In this regard, CX-5461 has been developed as a novel RNA polymerase I inhibitor and is currently in Phase I/II clinical trials for solid and hematological malignancies. In the present study, interactions between CX-5461 and single-dose X-ray exposure were assessed using isobologram analysis using MTS assay and drug-induced cell death was assessed using flow cytometric, confocal microscopy and Western blot analysis. Combination treatments involving CX-5461 and single-dose X-ray exposure highlighted increased effectiveness compared to individual treatment alone in the CaSki cervical cancer line, with marked synergistic interaction occurring within the low-drug (50 nM) and low-dose radiation range (2–6 Gy). Cell lines challenged with CX-5461 demonstrated the presence of DNA damage, induction of apoptosis, autophagy and senescence alongside high percentages of G2/M cell cycle arrest. In addition, we report preferential sensitivity of ovarian cancer cells with BRCA2 mutation to this novel agent. Taken together, CX-5461 displayed a broad spectrum of activity in a panel of solid cancer cell lines with IC₅₀ values ranging from 35 nM to >1 µM. The work described herein identifies the synergistic effects of CX-5461 in combination with X-rays in solid cancers and may also aid in the design of clinical trials involving this novel agent.

The combinational effect of E6/E7 siRNA and anti-miR-182 on apoptosis induction in HPV16-positive cervical cells

In the present research, we assumed that reducing the amounts of E6 and E7 oncoproteins by a specific siRNA sequence and recovering p53 and RB proteins, along with the recovery of the FOXO1 protein by applying anti-miR-182, would increase apoptosis and reduce proliferation rate in cancer cells. The HPV16-positive CaSki cervical cancer cell line was used. 48 hours after transfection of siRNA for targeting E6 and E7 oncoproteins and anti-miR-182, expression of its cellular targets p53, p21 and FOXO1 was assessed by real-time PCR, western blot analysis and immunocytofluorescence staining. In all treatments, apoptosis rate and viability were evaluated using Annexin-V-FITC apoptosis detection kits and MTT assays, respectively. Among the designed siRNAs, E6-1 and E7-2 proved the most effective in reducing E6 and E7 expressions by increasing the apoptotic rates to 12.4% and 16%, respectively, after 48 hours. Also, using anti-miR-182 increased apoptotic rate to 12.7% 48 hours after transfection of cervical cancer cells. The combinational use of either E6-1 or E7-2 siRNAs with anti-miR-182 resulted in a rise in apoptosis to 19.3% and 26%, respectively, higher than those obtained from the individual application of either without anti-miR-182. The simultaneous use of siRNA E6-1 and siRNA E7-2 with cisplatin increased sensitivity to cisplatin and reduced the viability of the cancer cells as compared to the use of cisplatin alone. The simultaneous use of cisplatin and anti-miR-182 had no considerable effect on viability or apoptosis rate compared to cisplatin alone.

Comparison of Nedaplatin- and Cisplatin-Based Concurrent Chemoradiotherapy in Locally Advanced Cervical Cancer Patients: A Propensity Score Analysis

Purpose

The aim of this study was to evaluate the efficacy of using nedaplatin to replace cisplatin for concurrent chemoradiotherapy (CCRT) in patients with newly diagnosed locally advanced cervical cancer.

Methods

The medical records of 155 patients with cervical cancer who had undergone CCRT with cisplatin (n = 85) or nedaplatin (n = 70) between January 2012 and January 2017 were retrospectively reviewed. Propensity score analysis with 1:1 matching with the nearest neighbor matching method was performed to assess response rates, progression-free survival, overall survival, and toxicity between 2 groups.

Results

Propensity score matching identified 63 patients in each group. After matching, compared with patients treated with cisplatin-based concurrent chemoradiotherapy (CisRT), we found that patients treated with nedaplatin-based concurrent chemoradiotherapy (NedaRT) had a significant higher recurrence rate (25.4% vs 42.9%; P = 0.04). In addition, the 3-year progression-free survival rate for NedaRT group was also worse than that for the CisRT group (52.2% vs 63.4%, P = 0.03). There was no difference in the overall response rates between the CisRT and NedaRT groups (87.3% and 90.5%, respectively; P = 0.57). The rates of 3-year overall survival and grades 3 to 4 toxicities were similar between the 2 groups.

Conclusions

The clinical outcome of this cohort of patients with locally advanced cervical cancer treated with CCRT did in no way provide support for the use of nedaplatin in place of cisplatin in chemoradiation and demonstrated no equivalence of the 2 drugs. Cautions should be taken for the replacement among platinum complexes in cancer treatment.

Synthetic siRNA targeting human papillomavirus 16 E6: a perspective on in vitro nanotherapeutic approaches

High-risk human papillomaviruses infect skin and mucosa, causing approximately 5% of cancers worldwide. In the search for targeted nanotherapeutic approaches, siRNAs against the viral E6 transcript have been molecules of interest but have not yet seen successful translation into the clinic. By reviewing the past approximately 15 years of in vitro literature, we identify the need for siRNA validation protocols which concurrently evaluate ranges of key treatment parameters as well as characterize downstream process restoration in a methodical, quantitative manner and demonstrate their implementation using our own data. We also reflect on the future need for more appropriate cell culture models to represent patient lesions as well as the application of personalized approaches to identify optimal treatment strategies.

siAbasic: a comprehensive database for potent siRNA-6Ø sequences without off-target effects

Small interfering RNA (siRNA) is widely used to specifically silence target gene expression, but its microRNA (miRNA)-like function inevitably suppresses hundreds of off-targets. Recently, complete elimination of the off-target repression has been achieved by introducing an abasic nucleotide to the pivot (position 6; siRNA-6Ø), of which impaired base pairing destabilizes transitional nucleation (positions 2–6). However, siRNA-6Ø varied in its conservation of on-target activity (∼80–100%), demanding bioinformatics to discover the principles underlying its on-target efficiency. Analyses of miRNA–target interactions (Ago HITS-CLIP) showed that the stability of transitional nucleation correlated with the target affinity of RNA interference. Furthermore, interrogated analyses of siRNA screening efficiency, experimental data and broadly conserved miRNA sequences showed that the free energy of transitional nucleation (positions 2–5) in siRNA-6Ø required the range of stability for effective on-target activity (−6 ≤ ΔG[2:5] ≤ −3.5 kcal mol⁻¹). Taking into consideration of these features together with locations, guanine-cytosine content (GC content), nucleotide stretches, single nucleotide polymorphisms and repetitive elements, we implemented a database named ‘siAbasic’ that provided the list of potent siRNA-6Ø sequences for most of human and mouse genes (≥ ∼95%), wherein we experimentally validated some of their therapeutic potency. siAbasic will aid to ensure potency of siRNA-6Ø sequences without concerning off-target effects for experimental and clinical purposes.

Polyamidoamine-Decorated Nanodiamonds as a Hybrid Gene Delivery Vector and siRNA Structural Characterization at the Charged Interfaces

Nanodiamonds have been discovered as a new exogenous material source in biomedical applications. As a new potent form of nanodiamond (ND), polyamidoamine-decorated nanodiamonds (PAMAM-NDs) were prepared for E7 or E6 oncoprotein-suppressing siRNA gene delivery for high risk human papillomavirus-induced cervical cancer, such as types 16 and 18. It is critical to understand the physicochemical properties of siRNA complexes immobilized on cationic solid ND surfaces in the aspect of biomolecular structural and conformational changes, as the new inert carbon material can be extended into the application of a gene delivery vector. A spectral study of siRNA/PAMAM-ND complexes using differential scanning calorimetry and circular dichroism spectroscopy proved that the hydrogen bonding and electrostatic interactions between siRNA and PAMAM-NDs decreased endothermic heat capacity. Moreover, siRNA/PAMAM-ND complexes showed low cell cytotoxicity and significant suppressing effects for forward target E6 and E7 oncogenic genes, proving functional and therapeutic efficacy. The cellular uptake of siRNA/PAMAM-ND complexes at 8 h was visualized by macropinocytes and direct endosomal escape of the siRNA/PAMAM-ND complexes. It is presumed that PAMAM-NDs provided a buffering cushion to adjust the pH and hard mechanical stress to escape endosomes. siRNA/PAMAM-ND complexes provide a potential organic/inorganic hybrid material source for gene delivery carriers.

Sensitization of glycoengineered interferon-β1a-resistant cancer cells by cFLIP inhibition for enhanced anti-cancer therapy

In this study, we examined the molecular mechanism underlying the resistance of cancer cells to R27T, a glycoengineered version of recombinant human interferon (IFN)-β1a, and sought to overcome R27T resistance through combination therapy. R27T has been shown to induce anti-proliferation and apoptosis in human OVCAR-3 and MCF-7 cells, but not in HeLa cells. R27T treatment increased caspase-8 activity and the consequent cleavage of caspase-8 and -3 in R27T-sensitive OVCAR-3 cells, but not in R27T-resistant HeLa cells. Conversely, R27T increased the expression of cellular FLICE-like inhibitory protein (cFLIP) in HeLa cells, but not in OVCAR-3 cells. The sensitization of HeLa cells with cFLIP small interfering RNA or 4,5,6,7-tetrabromobenzotriazole (TBB, an inhibitor of casein kinase-2) facilitated R27T-induced caspase activation, and consequently apoptosis. In OVCAR-3-xenografted mice, intraperitoneal administration of R27T showed 2.1-fold higher anti-tumor efficacy than did the control vehicle. The combined administration of R27T and TBB showed the greatest anti-tumor effect in HeLa tumor-bearing mice, reducing the relative tumor volume by 35.7% compared to that in R27T-treated mice. Taken together, our results suggest that R27T has potential as an anti-cancer drug, and combination therapy with cFLIP inhibitors may be an effective strategy for overcoming R27T resistance.

Effect of HPV E6/E7 siRNA with Chemotherapeutic Agents on the Regulation of TP53/E2F Dynamic Behavior for Cell Fate Decisions

Toxicity and resistance remain major challenges for advanced or recurrent cervical cancer therapies, as treatment requires high doses of chemotherapeutic agents. Restoration of TP53 and hypophosphorylated-retinoblastoma (pRB) proteins by human papillomavirus (HPV) E6/E7 siRNA sensitizes HPV-positive cervical cancer cells toward chemotherapeutic agents. Here, we investigated the therapeutic effects of E6/E7 siRNA on the dynamic behavior of TP53 and RB/E2F signaling networks in deciding the cell fate. The synergistic effect of HPV E6/E7 siRNA pool (SP) with chemotherapeutic agents on TP53 and RB/E2F signaling, proliferation, and apoptosis was analyzed in vitro and in vivo. Compared to the E6/E7 SP alone, E6/E7 SP with cisplatin treatment effectively restored TP53 and RB/E2F signaling and contributes to differences in cell fate, such as apoptosis or cell cycle arrest. We also developed a cellular dynamics model that includes TP53-RB/E2F dynamics and cell proliferation profiles, and confirmed its utility for investigating E6/E7 siRNA-based combination regimens. Using a dual reporter system, we further confirmed the cross talk between TP53 and RB/E2F signaling mechanisms. Treatment of E6/E7 SP cationic liposome (i.v.) with cisplatin and paclitaxel (i.p.) potentially inhibited tumor growth in BALB/c-nude mice. Altogether, our findings suggest that stabilization of TP53 and the RB/E2F repressor complex by E6/E7 SP combined with low-dose chemotherapy can effectively suppress tumor growth.

Targeting HPV-infected cervical cancer cells with PEGylated liposomes encapsulating siRNA and the role of siRNA complexation with polyethylenimine

The greatest obstacle to clinical application of cancer gene therapy is lack of effective delivery tools. Gene delivery vehicles must protect against degradation, avoid immunogenic effects and prevent off target delivery which can cause harmful side effects. PEGylated liposomes have greatly improved tumor localization of small molecule drugs and are a promising tool for nucleic acid delivery as the polyethylene glycol (PEG) coating protects against immune recognition and blood clearance. In this study, small interfering RNA (siRNA) was fully encapsulated within PEGylated liposomes by complexing the siRNA with a cationic polymer, polyethyleneimine (PEI), before encapsulation. Formation methods and material compositions were then investigated for their effects on encapsulation. This technology was translated for protective delivery of siRNA designed for human papillomavirus (HPV) viral gene silencing and cervical cancer treatment. PEGylated liposomes encapsulating siRNA were functionalized with the AG86 targeting peptide-amphiphile which binds to the α6β4 integrin, a cervical cancer biomarker. It was found that both targeting and polymer complexation before encapsulation were critical components to effective transfection.

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.

Detection of E6-AP as a potential therapeutic target in cervical specimen of HPV-infected women

PURPOSE

Silencing of HPV oncogenes or their human host client proteins using topically applied small interfering RNA (siRNA) may be an attractive nonsurgical strategy for CIN treatment. An exploratory clinical investigation was designed to evaluate E6-AP mRNA expression levels in different stages of cervical intraepithelial neoplasia and during the menstrual cycle.

METHODS

In 38 premenopausal women aged 18-45 years referred to colposcopy clinic, analysis of serum hormones, cervical smears for cytology and HPV DNA, cervical biopsy, p16 immunohistochemistry and E6-AP mRNA expression levels in cervical smears and biopsies were performed. The intra-subject variability in E6-AP mRNA expression of vaginal smears was assessed and compared to cervical biopsy specimens.

RESULTS

RNA of sufficient quantity and quality was available for E6-AP expression analysis from 97 % of the collected cervical smears and from 56 % of the collected biopsy samples. The normalized RNA levels from cervical smears were approximately tenfold higher compared to biopsies. There was little influence by the phase of the menstrual cycle or by CIN stage. Real-time PCR showed that the expression level of E6-AP is in a range (<28 C t) that would allow for detection of at least 100-fold modulation by a therapeutic agent (based on an assay LOD of C t = 36).

CONCLUSIONS

Our findings suggest a potential therapeutic approach using E6-AP siRNA as a specific molecular target in cervical intraepithelial neoplasia.

Treatment response of HPV-positive and HPV-negative head and neck squamous cell carcinoma cell lines

OBJECTIVES

Infection with the human papillomavirus (HPV) is an important risk factor for development of head and neck squamous cell carcinoma (HNSCC). Strikingly, HPV-positive HNSCCs have a more favorable prognosis than their HPV-negative counterparts. The current study was designed to explain this favorable prognosis of HPV-positive HNSCC.

MATERIALS AND METHODS

This was performed by investigating the response of four HPV-positive and fourteen HPV-negative HNSCC cell lines to cisplatin, cetuximab and radiation.

RESULTS

Analysis of the responses of this cell line panel indicated that HPV-positive cells are more resistant to cisplatin treatment than the HPV-negative HNSCCs, whereas the response to radiation and cetuximab did not differ.

CONCLUSIONS

The current study suggests that the favorable prognosis for patients with HPV-positive HNSCC does not seem to be related to an intrinsic sensitivity of these tumor cells to chemotherapy or radiation in vitro.

Plasmid-based E6-specific siRNA and co-expression of wild-type p53 suppresses the growth of cervical cancer in vitro and in vivo

The E6 protein of the oncogenic HPV-16 functions by interfering with the normal cell cycle control mechanisms, particularly those controlled by p53. In this study, we developed a dual expression plasmid that coexpressed-E6-specific siRNA and wild type p53, and to evaluate its effects on cervical cancer growth. We found that simultaneous expression of pSi-E6-P53 caused a robust suppression of tumor growth when compared to the controls either E6-specific siRNA or p53 alone. In conclusion, our findings demonstrate that a combined strategy of co-expressed E6-specific siRNA and p53 synergistically and more effectively suppressed cervical tumor growth when compared with single treatment.

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.

Tob1 induces apoptosis and inhibits proliferation, migration and invasion of gastric cancer cells by activating Smad4 and inhibiting β‑catenin signaling

Transducer of ErbB-2.1 (Tob1), a tumor suppressor protein, is inactivated in a variety of cancers including stomach cancer. However, the role of Tob1 in gastric carcinogenesis remains elusive. The present study aimed to investigate whether Tob1 could inhibit gastric cancer progression in vitro, and to elucidate its underlying molecular mechanisms. We found differential expression of Tob1 in human gastric cancer (MKN28, AGS and MKN1) cells. The overexpression of Tob1 induced apoptosis in MKN28 and AGS cells, which was associated with sub-G1 arrest, activation of caspase-3, induction of Bax, inhibition of Bcl-2 and cleavage of poly (ADP-ribose) polymerase (PARP). In addition, Tob1 inhibited proliferation, migration and invasion, which were reversed in MKN1 and AGS cells transfected with Tob1 siRNA. Overexpression of Tob1 in MKN28 and AGS cells induced the expression of Smad4, leading to the increased expression and the promoter activity of p15, which was diminished by silencing of Tob1 using specific siRNA. Tob1 decreased the phosphorylation of Akt and glycogen synthase kinase-3β (GSK3β) in MKN28 and AGS cells, resulting in the reduced protein expression and the transcriptional activity of β‑catenin, which in turn decreased the expression of cyclin D1, cyclin-dependent kinase-4 (CDK4), urokinase plasminogen activator receptor (uPAR) and peroxisome proliferator and activator receptor-δ (PPARδ). Conversely, silencing of Tob1 induced the phosphorylation of Akt and GSK-3β, and increased the expression of β‑catenin and its target genes. Collectively, our study demonstrates that the overexpression of Tob1 inhibits gastric cancer progression by activating Smad4- and inhibiting β‑catenin-mediated signaling pathways.