Selective targeting of HPV-16 E6/E7 in cervical cancer cells with a potent oncolytic adenovirus and its enhanced effect with radiotherapy in vitro and vivo

Developing Oncolytic Viruses for the Treatment of Cervical Cancer

Cervical cancer represents one of the most important malignancies among women worldwide. Current therapeutic approaches for cervical cancer are reported not only to be inadequate for metastatic cervical cancer, but are also considered as cytotoxic for several patients leading to serious side effects, which can have negative implications on the quality of life of women. Therefore, there is an urgent need for the development of innovative and effective treatment options. Oncolytic viruses can eventually become effective biological agents, since they preferentially infect and kill cancer cells, while leaving the normal tissue unaffected. Moreover, they are also able to leverage the host immune system response to limit tumor growth. This review aims to systematically describe and discuss the different types of oncolytic viruses generated for targeting cervical cancer cells, as well as the outcome of the combination of virotherapy with conventional therapies. Although many preclinical studies have evaluated the therapeutic efficacy of oncolytic viruses in cervical cancer, the number of clinical trials so far is limited, while their oncolytic properties are currently being tested in clinical trials for the treatment of other malignancies.

Gene Therapy for Malignant and Benign Gynaecological Disorders: A Systematic Review of an Emerging Success Story

Simple Summary

This review discusses all the major advances in gene therapy of gynaecological disorders, highlighting the novel and potentially therapeutic perspectives associated with such an approach. It specifically focuses on the gene therapy strategies against major gynaecological malignant disorders, such as ovarian, cervical, and endometrial cancer, as well as benign disorders, such as uterine leiomyomas, endometriosis, placental, and embryo implantation disorders. The above therapeutic strategies, which employ both viral and non-viral systems for mutation compensation, suicide gene therapy, oncolytic virotherapy, antiangiogenesis and immunopotentiation approaches, have yielded promising results over the last decade, setting the grounds for successful clinical trials.

Abstract

Despite the major advances in screening and therapeutic approaches, gynaecological malignancies still present as a leading cause of death among women of reproductive age. Cervical cancer, although largely preventable through vaccination and regular screening, remains the fourth most common and most lethal cancer type in women, while the available treatment schemes still pose a fertility threat. Ovarian cancer is associated with high morbidity rates, primarily due to lack of symptoms and high relapse rates following treatment, whereas endometrial cancer, although usually curable by surgery, it still represents a therapeutic problem. On the other hand, benign abnormalities, such as fibroids, endometriosis, placental, and embryo implantation disorders, although not life-threatening, significantly affect women’s life and fertility and have high socio-economic impacts. In the last decade, targeted gene therapy approaches toward both malignant and benign gynaecological abnormalities have led to promising results, setting the ground for successful clinical trials. The above therapeutic strategies employ both viral and non-viral systems for mutation compensation, suicide gene therapy, oncolytic virotherapy, antiangiogenesis and immunopotentiation. This review discusses all the major advances in gene therapy of gynaecological disorders and highlights the novel and potentially therapeutic perspectives associated with such an approach.

Virus against virus: strategies for using adenovirus vectors in the treatment of HPV-induced cervical cancer

Although most human papillomavirus (HPV) infections are harmless, persistent infection with high-risk types of HPV is known to be the leading cause of cervical cancer. Following the infection of the epithelium and integration into the host genome, the oncogenic proteins E6 and E7 disrupt cell cycle control by inducing p53 and retinoblastoma (Rb) degradation. Despite the FDA approval of prophylactic vaccines, there are still issues with cervical cancer treatment; thus, many therapeutic approaches have been developed to date. Due to strong immunogenicity, a high capacity for packaging foreign DNA, safety, and the ability to infect a myriad of cells, adenoviruses have drawn attention of researchers. Adenovirus vectors have been used for different purposes, including as oncolytic agents to kill cancer cells, carrier for RNA interference to block oncoproteins expression, vaccines for eliciting immune responses, especially in cytotoxic T lymphocytes (CTLs), and gene therapy vehicles for restoring p53 and Rb function.

Delivery of cancer therapies by synthetic and bio-inspired nanovectors

BACKGROUND

As a complement to the clinical development of new anticancer molecules, innovations in therapeutic vectorization aim at solving issues related to tumor specificity and associated toxicities. Nanomedicine is a rapidly evolving field that offers various solutions to increase clinical efficacy and safety. MAIN: Here are presented the recent advances for different types of nanovectors of chemical and biological nature, to identify the best suited for translational research projects. These nanovectors include different types of chemically engineered nanoparticles that now come in many different flavors of 'smart' drug delivery systems. Alternatives with enhanced biocompatibility and a better adaptability to new types of therapeutic molecules are the cell-derived extracellular vesicles and micro-organism-derived oncolytic viruses, virus-like particles and bacterial minicells. In the first part of the review, we describe their main physical, chemical and biological properties and their potential for personalized modifications. The second part focuses on presenting the recent literature on the use of the different families of nanovectors to deliver anticancer molecules for chemotherapy, radiotherapy, nucleic acid-based therapy, modulation of the tumor microenvironment and immunotherapy.

CONCLUSION

This review will help the readers to better appreciate the complexity of available nanovectors and to identify the most fitting "type" for efficient and specific delivery of diverse anticancer therapies.

Cellular Functions of HPV16 E5 Oncoprotein during Oncogenic Transformation

The human papillomavirus (HPV) is recognized as the main etiologic agent associated with cervical cancer. HPVs are epitheliotropic, and the ones that infect the mucous membranes are classified into low-risk (LR) and high-risk (HR) types. LR-HPVs produce benign lesions, whereas HR-HPVs produce lesions that may progress to cancer. HR-HPV types 16 and 18 are the most frequently found in cervical cancer worldwide. E6 and E7 are the major HPV oncogenic proteins, and they have been profusely studied. Moreover, it has been shown that the HPV16 E5 (16E5) oncoprotein generates transformation, although the molecular mechanisms through which it carries out its activity have not been well defined. In contrast to E6 and E7, the E5 open reading frame is lost during the integration of the episomal HPV DNA into the cellular genome. This suggests that E5 acts at the early stages of the transformation process. In this review, we focused on the biochemical characteristics and functions of the HPV E5 oncoprotein, mainly on its association with growth factor receptors and other cellular proteins. Knowledge of the HPV E5 biology is important to understand the role of this oncoprotein in maintaining the viral cycle through the modulation of proliferation, differentiation, and apoptosis, as well as the alteration of other processes, such as survival, adhesion, migration, and invasion during early carcinogenesis. Finally, we summarized recent research that uses the E5 oncoprotein as a therapeutic target, promising a novel approach to the treatment of cervical cancer in its early stages.

Ready for Repair? Gene Editing Enters the Clinic for the Treatment of Human Disease

We present an overview of clinical trials involving gene editing using clustered interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein 9 (Cas9), transcription activator-like effector nucleases (TALENs), or zinc finger nucleases (ZFNs) and discuss the underlying mechanisms. In cancer immunotherapy, gene editing is applied ex vivo in T cells, transgenic T cell receptor (tTCR)-T cells, or chimeric antigen receptor (CAR)-T cells to improve adoptive cell therapy for multiple cancer types. This involves knockouts of immune checkpoint regulators such as PD-1, components of the endogenous TCR and histocompatibility leukocyte antigen (HLA) complex to generate universal allogeneic CAR-T cells, and CD7 to prevent self-destruction in adoptive cell therapy. In cervix carcinoma caused by human papillomavirus (HPV), E6 and E7 genes are disrupted using topically applied gene editing machinery. In HIV infection, the CCR5 co-receptor is disrupted ex vivo to generate HIV-resistant T cells, CAR-T cells, or hematopoietic stem cells. In β-thalassemia and sickle cell disease, hematopoietic stem cells are engineered ex vivo to induce the production of fetal hemoglobin. AAV-mediated in vivo gene editing is applied to exploit the liver for systemic production of therapeutic proteins in hemophilia and mucopolysaccharidoses, and in the eye to restore splicing of the CEP920 gene in Leber's congenital amaurosis. Close consideration of safety aspects and education of stakeholders will be essential for a successful implementation of gene editing technology in the clinic.

Targeted Gene Delivery Therapies for Cervical Cancer

Despite being largely preventable through early vaccination and screening strategies, cervical cancer is the most common type of gynecological malignancy worldwide and constitutes one of the leading causes of cancer deaths in women. Patients with advanced or recurrent disease have a very poor prognosis; hence, novel therapeutic modalities to improve clinical outcomes in cervical malignancy are needed. In this regard, targeted gene delivery therapy is presented as a promising approach, which leads to the development of multiple strategies focused on different aspects. These range from altered gene restoration, immune system potentiation, and oncolytic virotherapy to the use of nanotechnology and the design of improved and enhanced gene delivery systems, among others. In the present manuscript, we review the current progress made in targeted gene delivery therapy for cervical cancer, the advantages and drawbacks and their clinical application. At present, multiple targeted gene delivery systems have been reported with encouraging preclinical results. However, the translation to humans has not yet shown a significant clinical benefit due principally to the lack of efficient vectors. Real efforts are being made to develop new gene delivery systems, to improve tumor targeting and to minimize toxicity in normal tissues.

Preclinical development of peptide vaccination combined with oncolytic MG1-E6E7 for HPV-associated cancer

Human papilloma virus (HPV)-associated cancer is a significant global health burden and despite the presence of viral transforming antigens within neoplastic cells, therapeutic vaccinations are ineffective for advanced disease. HPV positive TC1 cells are susceptible to viral oncolysis by MG1-E6E7, a custom designed oncolytic Maraba virus. Epitope mapping of mice vaccinated with MG1-E6E7 enabled the rational design of synthetic long peptide (SLP) vaccines against HPV16 and HPV18 antigens. SLPs were able to induce specific CD8+ immune responses and the magnitude of these responses significantly increased when boosted by MG1-E6E7. Logically designed vaccination induced multi-functional CD8+ T cells and provided complete sterilising immunity of mice challenged with TC1 cells. In mice bearing large HPV-positive tumours, SLP vaccination combined with MG1-E6E7 was able to clear tumours in 60% of mice and these mice were completely protected against a long term aggressive re-challenge with the TC1 tumour model. Combining conventional SLPs with the multi-functional oncolytic MG1-E6E7 represents a promising approach against advanced HPV positive neoplasia.

O-linked N-acetylglucosamine transferase promotes cervical cancer tumorigenesis through human papillomaviruses E6 and E7 oncogenes

O-linked N-acetylglucosamine (O-GlcNAc) transferase (OGT) increases O-GlcNAc modification (O-GlcNAcylation), and transcriptional co-regulator host cell factor 1 (HCF-1) is one of OGT targets. High-risk Human Papillomaviruses (HPVs) encode E6 and E7 oncoproteins, which promote cervical cancer. Here, we tested whether O-GlcNAc modification of HCF-1 affects HPV E6 and E7 expressions and tumorigenesis of cervical cancer. We found that depleting OGT with OGT-specific shRNA significantly decreased levels of E6 and E7 oncoproteins, and cervical cancer tumorigenesis, while OGT overexpression greatly increased levels of E6 and E7 oncoproteins. Notably, OGT overexpression caused dose-dependent increases in the transcriptional activity of E6 and E7, and this activity was decreased when HCF-1 was depleted with HCF-1-specific siRNA. Moreover, OGT depletion reduced proliferation, invasion, and metastasis in cervical cancer cells. Further, high glucose enhanced the interaction between OGT and HCF-1, paralleling increased levels of E6 and E7 in cervical cancer cells. Most importantly, we found that reducing OGT in HeLa cells caused decreased tumor growth in vivo. These findings identify OGT as a novel cellular factor involved in E6 and E7 expressions and cervical cancer tumorigenesis, suggesting that targeting OGT in cervical cancer may have potential therapeutic benefit.

O-linked-N-acetylglucosamine transferase is associated with metastatic spread of human papillomavirus E6 and E7 oncoproteins to the lungs of mice

High-risk human papilloma virus (HPV) 16/18 infections are often found in lung cancer. The cellular mechanisms involved in the metastatic spread of HPV-infected cervical cancer cells remain largely elusive. High O-linked-N-acetylglucosamine (O-GlcNAc) modification has also been observed in lung cancer. In the present study, we assessed the relationship between O-GlcNAc transferase (OGT) and HPV 16/18 E6/E7, or C-X-C chemokine receptor type 4 (CXCR4), in HeLa cells and in lungs of xenografted mice. Depleting OGT with an OGT-specific shRNA significantly decreased levels of E6 and E7 oncoproteins in HeLa cells and xenograft tumors, and reduced tumor formation in vivo. Western blotting and immunofluorescence analysis showed significantly decreased expression levels of E6, E7, and HCF-1 in the lungs of xenografted mice treated with an OGT-specific shRNA compared to those treated with non-targeting shRNA. Additionally, levels of E7 or OGT co-localized with Ki-67 were significantly decreased in the lungs of xenografted mice treated with OGT-specific shRNA compared to those treated with non-targeting shRNA. Moreover, levels of CXCR4 were significantly decreased in HeLa cells and in the lungs of xenografted mice treated with OGT-specific shRNA compared to those treated with non-targeting shRNA; this may be related to reduced adhesion or invasion of circulating HPV-positive tumor cells. These findings provide novel evidence that OGT functions in metastatic spread of HPV E6/E7-positive tumor cells to the lungs through E6/E7, HCF-1 and CXCR4, suggesting OGT might be a therapeutic target for HPV-positive lung cancer.

The antitumor efficacy of a novel adenovirus-mediated anti-p21Ras single chain fragment variable antibody on human cancers in vitro and in vivo

Activated ras genes are found in a large number of human tumors, and therefore are one of important targets for cancer therapy. This study investigated the antitumor effects of a novel single chain fragment variable antibody (scFv) against ras protein, p21Ras. The anti-p21Ras scFv gene was constructed by phage display library from hybridoma KGHR1, and then subcloned into replication-defective adenovirus vector to obtain recombinant adenovirus KGHV100. Human tumor cell lines with high expression of p21Ras SW480, MDA-MB‑231, OVCAR-3, BEL-7402, as well as tumor cell line with low expression of p21Ras, SKOV3, were employed to investigate antitumor effects in vitro and in vivo. Fluorescence microscopy demonstrated that KGHV100 was able to express intracellularly anti-p21Ras scFv antibody in cultured tumor cells and in transplantation tumor cells. MTT, Transwell, colony formation, and flow cytometry analysis showed that KGHV100 led to significant growth arrest in tumor cells with high p21Ras expression, and induced G0/G1 cell cycle arrest in the studied tumor cell lines. In vivo, KGHV100 significantly inhibited tumor growth following intratumoral injection, and the survival rates of the mice were higher than the control group. These results indicate that the adenovirus-mediated intracellular expression of the novel anti-p21Ras scFv exerted strong antitumoral effects, and may be a potential method for therapy of cancers with p21Ras overexpression.

KIF1B promotes glioma migration and invasion via cell surface localization of MT1-MMP

Malignant glioma is notorious for its aggressiveness and poor prognosis, and the invasiveness of glioma cells is the major obstacle. Accumulating evidence indicates that kinesin superfamily proteins (KIFs) may play key roles in tumor invasiveness, but the mechanisms remained unresolved. Our previous study demonstrated that membrane type 1-matrix metalloproteinase (MT1-MMP) was involved in Kinesin family member 1B (KIF1B)-modulated invasion of gastric cancer cells. Therefore, the role of KIF1B in glioma cell invasion and its relationship with MT1-MMP were explored in the present study. We found that aberrantly increased expression of KIF1B was associated with worse WHO pathological classification and Karnofsky performance status (KPS), which also showed a trend towards worse prognosis. In the transwell assay, knockdown of KIF1B using siRNA repressed U87MG and A172 glioma cell migration and invasion. Silencing KIF1B inhibited expression of membranal MT1-MMP; however, the amount of MT1-MMP in the whole cell lysate was not affected. In conclusion, targeting KIF1B may be an option for anti-invasive therapies targeting glioma.

Synergistic combination of histone deacetylase inhibitor suberoylanilide hydroxamic acid and oncolytic adenovirus ZD55-TRAIL as a therapy against cervical cancer

Oncolytic adenoviruses (OA) have been investigated as virotherapeutic agents for the treatment of cervical cancer and thus far results are promising. However, the cytotoxicity of the viruses requires improvement. The present study demonstrated that this can be achieved by combining ZD55-TRAIL, an OA containing the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) gene, with the histone deacetylase inhibitor suberoylanilide hydroxamic acid (SAHA). It was demonstrated that these agents act synergistically to kill HeLa cells by inducing G2 growth arrest and apoptosis. Notably, in a mouse xenograft model, ZD55-TRAIL/SAHA combination inhibited tumor growth. At the molecular level, it was found that upregulation of IκBα and the p50 and p65 subunits of nuclear factor-κB induced by ZD55-TRAIL, can be abrogated by SAHA treatment. These data strongly suggested that ZD55-TRAIL/SAHA co-treatment may serve as an effective therapeutic strategy against cervical cancer.

TALEN-mediated targeting of HPV oncogenes ameliorates HPV-related cervical malignancy

Persistent HPV infection is recognized as the main etiologic factor for cervical cancer. HPV expresses the oncoproteins E6 and E7, both of which play key roles in maintaining viral infection and promoting carcinogenesis. While siRNA-mediated targeting of E6 and E7 transcripts temporarily induces apoptosis in HPV-positive cells, it does not eliminate viral DNA within the host genome, which can harbor escape mutants. Here, we demonstrated that specifically targeting E6 and E7 within host DNA with transcription activator-like effector nucleases (TALENs) induces apoptosis, inhibits growth, and reduces tumorigenicity in HPV-positive cell lines. TALEN treatment efficiently disrupted E6 and E7 oncogenes, leading to the restoration of host tumor suppressors p53 and retinoblastoma 1 (RB1), which are targeted by E6 and E7, respectively. In the K14-HPV16 transgenic mouse model of HPV-driven neoplasms, direct cervical application of HPV16-E7-targeted TALENs effectively mutated the E7 oncogene, reduced viral DNA load, and restored RB1 function and downstream targets transcription factor E2F1 and cycling-dependent kinase 2 (CDK2), thereby reversing the malignant phenotype. Together, the results from our study suggest that TALENs have potential as a therapeutic strategy for HPV infection and related cervical malignancy.

Leptin-mediated regulation of MT1-MMP localization is KIF1B dependent and enhances gastric cancer cell invasion

Leptin overexpression is closely correlated with gastric cancer (GC) invasion, but its exact effect and the underlying mechanism in tumorigenesis remain poorly understood. Membrane type 1-matrix metalloproteinase (MT1-MMP), a surface-anchored 'master switch' proteinase, is overexpressed and plays crucial roles in tumor invasion. Here, we characterized the influence of leptin on the generation and surface localization of MT1-MMP in GC and elucidated its molecular mechanisms. Our results revealed that leptin promoted GC cell invasion in vitro by upregulating MT1-MMP expression. Furthermore, cell surface biotinylation assay and flow cytometry demonstrated that the surface expression of MT1-MMP was also enhanced by leptin, and knockdown of kinesin family member 1B (KIF1B, a microtubule plus end-directed monomeric motor protein) by small interference RNA inhibited this process. Notably, coimmunoprecipitation analysis indicated that leptin enhanced the interaction of MT1-MMP with KIF1B in a time-dependent manner, which consequently contributed to GC cell invasion. Moreover, leptin increased MT1-MMP or KIF1B expression by the protein kinase B (AKT) pathway and extracellular signal-regulated kinase 1/2 partially participated in this process. However, only AKT was implicated in the leptin-mediated membrane localization of MT1-MMP. Immunohistochemistry analysis revealed that leptin, MT1-MMP and KIF1B are overexpressed in GC tissues, and they positively correlated with clinical stage and lymph node metastasis. These observations indicate that this regulatory network exists in vivo. Taken together, our findings suggest that leptin is an effective intracellular stimulator of MT1-MMP and that leptin-enhanced cell surface localization of MT1-MMP is dependent on KIF1B, which consequently plays a critical role in GC invasion.

Antitumor effects of bladder cancer-specific adenovirus carrying E1A-androgen receptor in bladder cancer

The high frequency of recurrence and poor survival rate of bladder cancer demand exploration of novel strategies. Gene therapy via adenovirus has shown promising potential for the treatment of tumors. We constructed a bladder cancer-specific adenovirus carrying E1A-androgen receptor (AR) under the control of UPII promoter and prostate stem cell antigen enhancer (PSCAE), designated as Ad/PSCAE/UPII/E1A-AR, and investigated its antitumor effects in vitro and in vivo. We demonstrated that Ad/PSCAE/UPII/E1A-AR could be selectively replicated in bladder tumor cell lines (5637, BIU87, EJ and T24) when compared with control adenovirus Ad/PSCAE/UPII/Luc. However, there was no evidence of cytotoxicity for normal human bladder cell line SV-HUC-1 and hepatoma cell line SMMC7721. AR agonist R1881 could strengthen the oncolytic effect of Ad/PSCAE/UPII/E1A-AR in bladder cancer cells. In addition, we demonstrated that intratumoral injection of Ad/PSCAE/UPII/E1A-AR into established subcutaneous human EJ tumors in nude mice could significantly regress the growth of tumor and markedly prolong survival for tumor-bearing mice; on the other hand, saline-treated tumors continued to grow rapidly. Our studies indicate that Ad/PSCAE/UPII/E1A-AR could effectively treat bladder cancer in vitro and in vivo. Furthermore, our findings provide a promising therapeutic modality for the treatment of bladder cancer.

Papillomavirus E5: the smallest oncoprotein with many functions

Papillomaviruses (PVs) are established agents of human and animal cancers. They infect cutaneous and mucous epithelia. High Risk (HR) Human PVs (HPVs) are consistently associated with cancer of the uterine cervix, but are also involved in the etiopathogenesis of other cancer types. The early oncoproteins of PVs: E5, E6 and E7 are known to contribute to tumour progression. While the oncogenic activities of E6 and E7 are well characterised, the role of E5 is still rather nebulous. The widespread causal association of PVs with cancer makes their study worthwhile not only in humans but also in animal model systems. The Bovine PV (BPV) system has been the most useful animal model in understanding the oncogenic potential of PVs due to the pivotal role of its E5 oncoprotein in cell transformation. This review will highlight the differences between HPV-16 E5 (16E5) and E5 from other PVs, primarily from BPV. It will discuss the targeting of E5 as a possible therapeutic agent.

Targeting the human papillomavirus E6 and E7 oncogenes through expression of the bovine papillomavirus type 1 E2 protein stimulates cellular motility

Expression of the high-risk human papillomavirus (HPV) E6 and E7 oncogenes is essential for the initiation and maintenance of cervical cancer. The repression of both was previously shown to result in activation of their respective tumor suppressor targets, p53 and pRb, and subsequent senescence induction in cervical cancer cells. Consequently, viral oncogene suppression is a promising approach for the treatment of HPV-positive tumors. One well-established method of E6/E7 repression involves the reexpression of the viral E2 protein which is usually deleted in HPV-positive cancer cells. Here, we show that, surprisingly, bovine papillomavirus type 1 (BPV1) E2 but not RNA interference-mediated E6/E7 repression in HPV-positive cervical cancer cells stimulates cellular motility and invasion. Migration correlated with the dynamic formation of cellular protrusions and was dependent upon cell-to-cell contact. While E2-expressing migratory cells were senescent, migration was not a general feature of cellular senescence or cell cycle arrest and was specifically observed in HPV-positive cervical cancer cells. Interestingly, E2-expressing cells not only were themselves motile but also conferred increased motility to admixed HeLa cervical cancer cells. Together, our data suggest that repression of the viral oncogenes by E2 stimulates the motility of E6/E7-targeted cells as well as adjacent nontargeted cancer cells, thus raising the possibility that E2 expression may unfavorably increase the local invasiveness of HPV-positive tumors.

Leukemia inhibitory factor downregulates human papillomavirus-16 oncogene expression and inhibits the proliferation of cervical carcinoma cells

The constitutive proliferation and resistance to differentiation and apoptosis of neoplastic cervical cells depend on sustained expression of human papillomavirus oncogenes. Inhibition of these oncogenes is a goal for the prevention of progression of HPV-induced neoplasias to cervical cancer. SiHa cervical cancer cells were transfected with an HPV-16 promoter reporter construct and treated with leukemia inhibitory factor (LIF), a human cytokine of the interleukin 6 superfamily. SiHa and CaSki cervical cancer cells were also assessed for proliferation by MTT precipitation, programmed cell death by flow cytometry, and HPV E6 and E7 expression by real-time PCR. LIF-treated cervical cancer cells showed significantly reduced HPV LCR activation, reduced levels of E6 and E7 mRNA, and reduced proliferation. We report the novel use of LIF to inhibit viral oncogene expression in cervical cancer cells, with concomitant reduction in proliferation suggesting re-engagement of cell-cycle regulation.

Making sense of therapeutics using antisense technology

INTRODUCTION

Antisense oligonucleotides (ASOs) are short synthetic single-stranded DNA sequences that bind to and induce the cleavage of homologous stretches of mRNA sequences. These result in targeted destruction of mRNA and correction of genetic aberrations. ASOs thus can act as drug molecules and potentially rectify many disease conditions. The broad range of applications reported in the literature highlights the advances in the field.

AREAS COVERED

This review covers different areas in which use of ASOs has been shown to have therapeutic effects. Some drugs in different stages of preclinical and clinical trials are discussed in detail. The problems faced and the strategies to surmount them are also described. The readers will gain an understanding of the recent developments in the field of ASOs with emphasis on their therapeutic applications. They will also become aware of the different strategies used for targeted delivery of ASOs and their stabilization, which may be useful for their work in this field, or in the area of nucleic acid therapeutics in general.

EXPERT OPINION

The design and application of ASOs for recognition of target mRNA sequences have become a fairly straightforward protocol. The main problem lies in designing ASOs which are stable in in vivo milieu. The delivery and bioavailability of the oligonucleotide to the site of action continue to be hurdles in the development of ASOs and therapeutic molecules.

Adenoviral E4orf3 and E4orf6 proteins, but not E1B55K, increase killing of cancer cells by radiotherapy in vivo

PURPOSE

Radiotherapy is widely used for treatment of many tumor types, but it can damage normal tissues. It has been proposed that cancer cells can be selectively sensitized to radiation by adenovirus replication or by using radiosensitizing transgenes. Adenoviral proteins E1B55K, E4orf3, and E4orf6 play a role in radiosensitization, by targeting the Mre11, Rad50, and NBS1 complex (MRN) and inhibiting DNA double-strand break (DSB) repair. We hypothesize that combined with irradiation, these adenoviral proteins increase cell killing through the impairment of DSB repair.

METHODS AND MATERIALS

We assessed the radiosensitizing/additive potential of replication-deficient adenoviruses expressing E1B55K, E4orf3, and E4orf6 proteins. Combination treatments with low-dose external photon beam radiotherapy were studied in prostate cancer (PC-3MM2 and DU-145), breast cancer (M4A4-LM3), and head and neck cancer (UT-SCC8) cell lines. We further demonstrated radiosensitizing or additive effects in mice with PC-3MM2 tumors.

RESULTS

We show enhanced cell killing with adenovirus and radiation combination treatment. Co-infection with several of the viruses did not further increase cell killing, suggesting that both E4orf6 and E4orf3 are potent in MRN inhibition. Our results show that adenoviral proteins E4orf3 and E4orf6, but not E1B55K, are effective also in vivo. Enhanced cell killing was due to inhibition of DSB repair resulting in persistent double-strand DNA damage, indicated by elevated phospho-H2AX levels at 24 h after irradiation.

CONCLUSIONS

This knowledge can be applied for improving the treatment of malignant tumors, such as prostate cancer, for development of more effective combination therapies and minimizing radiation doses and reducing side effects.

Human papillomavirus type 16 E5 oncoprotein as a new target for cervical cancer treatment

Human papillomavirus (HPV) infection is considered to be the necessary cause of cervical cancer. E6 and E7 oncoproteins of HPV have been known to play major roles in malignant transformation of cervical cells, inhibiting the tumor suppressors p53 and Rb. However, the role of E5 oncoprotein has been relatively less defined. HPV 16 E5 is a hydrophobic membrane-bound protein which associates with the Golgi apparatus, endoplasmic reticulum and perinuclear membrane. Accumulating evidences have suggested that E5 oncoprotein may also contribute to cervical carcinogenesis through modulating cellular signaling pathways in addition to augmenting the immortalization potential of E6 and E7. Multiple mechanisms, including activation of EGFR or inflammatory cell signaling pathway, have been implicated in malignant transformation by HPV 16 E5. Therefore, targeting E5 may be a rational approach for chemoprevention and treatment of cervical cancer, and understanding its oncogenic processes may help us to design novel therapeutic strategies. In this review, we discussed the roles of HPV 16 E5 in cervical carcinogenesis, altering several cellular signaling pathways involved in cell proliferation, angiogenesis and apoptosis.