Gel-based application of siRNA to human epithelial cancer cells induces RNAi-dependent apoptosis

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.

Highlights in nanocarriers for the treatment against cervical cancer

Cervical cancer is the second most common malignant tumor in women worldwide and has a high mortality rate, especially when it is associated with human papillomavirus (HPV). In US, an estimated 12,820 cases of invasive cervical cancer and an estimated 4210 deaths from this cancer will occur in 2017. With rare and very aggressive conventional treatments, one sees in the real need of new alternatives of therapy as the delivery of chemotherapeutic agents by nanocarriers using nanotechnology. This review covers different drug delivery systems applied in the treatment of cervical cancer, such as solid lipid nanoparticles (SNLs), liposomes, nanoemulsions and polymeric nanoparticles (PNPs). The main advantages of drug delivery thus improving pharmacological activity, improving solubility, bioavailability to bioavailability reducing toxicity in the target tissue by targeting of ligands, thus facilitating new innovative therapeutic technologies in a too much needed area. Among the main disadvantage is the still high cost of production of these nanocarriers. Therefore, the aim this paper is review the nanotechnology based drug delivery systems in the treatment of cervical cancer.

Utility of microRNAs and siRNAs in cervical carcinogenesis

MicroRNAs and siRNAs belong to a family of small noncoding RNAs which bind through partial sequence complementarity to 3'-UTR regions of mRNA from target genes, resulting in the regulation of gene expression. MicroRNAs have become an attractive target for genetic and pharmacological modulation due to the critical function of their target proteins in several signaling pathways, and their expression profiles have been found to be altered in various cancers. A promising technology platform for selective silencing of cell and/or viral gene expression using siRNAs is currently in development. Cervical cancer is the most common cancer in women in the developing world and sexually transmitted infection with HPV is the cause of this malignancy. Therefore, a cascade of abnormal events is induced during cervical carcinogenesis, including the induction of genomic instability, reprogramming of cellular metabolic pathways, deregulation of cell proliferation, inhibition of apoptotic mechanisms, disruption of cell cycle control mechanisms, and alteration of gene expression. Thus, in the present review article, we highlight new research on microRNA expression profiles which may be utilized as biomarkers for cervical cancer. Furthermore, we discuss selective silencing of HPV E6 and E7 with siRNAs which represents a potential gene therapy strategy against cervical cancer.

Methylation of nucleolar and coiled-body phosphoprotein 1 is associated with the mechanism of tumorigenesis in hepatocellular carcinoma

Nucleolar and coiled-body phosphoprotein 1 (NOLC1) plays an essential role in the synthesis of rRNA and the biosynthesis of ribosomes. Previous studies suggest that NOLC1 is crucial for normal cell growth, and plays a role in the regulation of tumorigenesis of nasopharyngeal carcinoma (NPC) and demonstrate that both NOLC1 and tumor protein 53 work synergistically to activate the MDM2 promoter in NPC cells. Yet, the functioning of NOLC1 in liver cancer remains unknown. The aim of the present study was to understand how the NOLC1 gene is regulated in liver carcinogenesis. In this study, we showed that NOLC1 was silenced or downregulated in liver tumor tissues when compared with that in the matched non-cancer tissues. In addition, human hepatoma cells weakly expressed NOLC1, whereas cultured human normal liver cell lines expressed abundant levels. The hypermethylation status in the promoter CpG1 start region appeared to be correlated with the NOLC1 expression levels in liver cell lines or liver normal and tissue specimens. We found that four CpG dinucleotides were located at the CpG1 start region. Further molecular analysis of mutagenesis indicated that the four CpG dinucleotides play a role in the promoter activity of the NOLC1 gene. The expression of NOLC1 and DNA methylation of its promoter affected cell proliferation and apoptosis. The expression of NOLC1 in hepatoma cell lines was restored following exposure to the demethylation agent, 5-azacytidine. Low expression of NOLC1 in hepatoma cell lines and liver cancer tissues was associated with cyclin D3. In conclusion, our study demonstrated that DNA methylation is a key mechanism of silenced NOLC1 expression in human hepatocellular carcinoma cells, and NOLC1 gene hypermethylation of the four CpG dinucleotides is a potential biomarker for hepatocellular carcinoma.

Noninvasive delivery of siRNA and plasmid DNA into skin by fractional ablation: erbium:YAG laser versus CO₂ laser

The present study was conducted to evaluate the impacts of fractional erbium (Er):YAG and CO2 lasers on skin permeation of small interfering (si)RNA and plasmid (p)DNA vectors. In vitro skin delivery was determined with a Franz diffusion cell. In vivo absorption was investigated by observing fluorescence and confocal microscopic imaging. Fractional laser-mediated ablation of the skin resulted in significant enhancement of dextran and siRNA penetration. Respective fluxes of dextran (10 kDa) and siRNA, which had similar molecular size, with Er:YAG laser irradiation at 5 J/cm(2) were 56- and 11-fold superior to that of intact skin. The respective permeation extents of dextran and siRNA by the CO2 laser at 4 mJ/400 spots were 42- and 12-fold greater than that of untreated skin. Fluorescence and confocal images showed increased fluorescence intensities and penetration depths of siRNA and pDNA delivery. According to an examination of the follicular permeant amount and fluorescence microscopy, hair follicles were important deposition areas for fractional laser-assisted delivery, with the Er:YAG modality revealing higher follicular siRNA selectivity than the CO2 modality. This is the first report of siRNA and pDNA penetrating the skin with a sufficient amount and depth with the assistance of fractional lasers.

Percutaneous gene therapy heals cranial defects

Nonhealing bone defects are difficult to treat. As the bone morphogenic protein and transforming growth factor beta pathways have been implicated in bone healing, we hypothesized that percutaneous Smad7 silencing would enhance signaling through both pathways and improve bone formation. Critical sized parietal trephine defects were created and animals received percutaneous injection of: agarose alone or agarose containing nonsense or Smad7 small interfering RNA (siRNA). At 12 weeks, SMADs1, 2, 3, 5, 7 and 8 levels were assessed. Smad1/5/8 osteogenic target, Dlx5, and SMAD2/3 angiogenic target, plasminogen activator inhibitor-1 (Pai1), transcription levels were measured. Noncanonical signaling through TGFβ activated kinase-1 (Tak1) and target, runt-related transcription factor 2 (Runx2) and collagen1α1 (Col1α1), transcription were also measured. Micro-computed tomography and Gomori trichome staining were used to assess healing. Percutaneous injection of Smad7 siRNA significantly knocked down Smad7 mRNA (86.3 ± 2.5%) and protein levels (46.3 ± 3.1%). The SMAD7 knockdown resulted in a significant increase in receptor-regulated SMADs (R-SMAD) (Smad 1/5/8 and Smad2/3) nuclear translocation. R-SMAD nuclear translocation increased Dlx5 and Pai1 transcription. Additionally, noncanonical signaling through Tak1 increased Runx2 and Col1α1 target transcription. Compared with animals treated with agarose alone (33.9 ± 2.8% healing) and nonsense siRNA (31.5 ± 11.8% healing), animals treated Smad7 siRNA had significantly great (91.2 ± 3.8%) healing. Percutaneous Smad7 silencing increases signal transduction through canonical and noncanonical pathways resulting in significant bone formation. Minimally invasive gene therapies may prove effective in the treatment of nonhealing bone defects.

SIRT1 promotes proliferation and inhibits apoptosis of human malignant glioma cell lines

In mammalian cells, SIRT1 decreases PTEN acetylation and inactivates the AKT pathway in a SIRT1 deacetylase-dependent manner. However, the function of SIRT1 in glioma was unknown. SIRT1 reexpression or knockdown was induced in human glioma cell lines. The cell synchronization, BrdU labeling and mitotic index were detected. Subsequently, cell cycle, cell viability, apoptosis, cell growth and proliferation were analyzed. Our work identified that SIRT1-knockdown significantly delayed mitotic entry of glioma cells, inhibited its growth and proliferation, and promoted its apoptosis. The apoptosis was related to PTEN/PI3K/AKT signaling pathway. The results showed that SIRT1 might be a promoter factor on tumorigenesis of glioma through PTEN/PI3K/AKT signaling pathway.

Molecular Mechanism and Potential Targets for Blocking HPV-Induced Lesion Development

Persistent infection with high-risk HPV is the etiologic agent associated with the development of cervical cancer (CC) development. However, environmental, social, epidemiological, genetic, and host factors may have a joint influence on the risk of disease progression. Cervical lesions caused by HPV infection can be removed naturally by the host immune response and only a small percentage may progress to cancer; thus, the immune response is essential for the control of precursor lesions and CC. We present a review of recent research on the molecular mechanisms that allow HPV-infected cells to evade immune surveillance and potential targets of molecular therapy to inhibit tumor immune escape.

The role of Med19 in the proliferation and tumorigenesis of human hepatocellular carcinoma cells

AIM

To explore the role of Med19, a component of the Mediator complex that coactivates DNA-binding transcription factors, in the proliferation and tumorigenesis of human hepatocellular carcinoma cells.

METHODS

The human hepatocellular carcinoma cell lines HepG2 and Hep3B were infected with lentiviral vectors encoding interfering RNA (RNAi) targeting the Med19 gene. To further confirm the inhibitory effects of RNAi vectors on Med19 gene expression, quantitative real-time RT-PCR and Western blotting assays were used. The proliferation of HepG2 and Hep3B cells after transduction with the Med19-RNAi-Lentivirus vector was evaluated by MTT conversion, BrdU incorporation, colony formation, and cell-cycle assays in vitro. In addition, the ability of the Med19-RNAi-Lentivirus vector-infected Hep3B cells to form tumors after inoculation into nude mice was determined.

RESULTS

Recombinant lentiviral vectors expressing small interfering RNA (siRNA) against Med19 were constructed and were found to efficiently downregulate Med19 mRNA and protein levels in HepG2 and Hep3B cells. Furthermore, the inhibition of Med19 by RNAi dramatically reduced hepatocellular carcinoma cell proliferation, induced cell-cycle arrest in the G(0)/G(1) phase, and suppressed tumor formation.

CONCLUSION

These results provide new evidence of an important role for Med19 in the development of hepatocellular carcinomas, suggesting that lentivirus-mediated RNAi to target Med19 is a potential tool for inhibiting cancer cell proliferation and tumorigenesis.

Human papillomavirus: gene expression, regulation and prospects for novel diagnostic methods and antiviral therapies

Human papillomaviruses (HPVs) cause diseases ranging from benign warts to invasive tumors. A subset of these viruses termed 'high risk' infect the cervix where persistent infection can lead to cervical cancer. Although many HPV genomes have been sequenced, knowledge of virus gene expression and its regulation is still incomplete. This is due in part to the lack, until recently, of suitable systems for virus propagation in the laboratory. HPV gene expression is polycistronic initiating from multiple promoters. Gene regulation occurs at transcriptional, but particularly post-transcriptional levels, including RNA processing, nuclear export, mRNA stability and translation. A close association between the virus replication cycle and epithelial differentiation adds a further layer of complexity. Understanding HPV mRNA expression and its regulation in the different diseases associated with infection may lead to development of novel diagnostic approaches and will reveal key viral and cellular targets for development of novel antiviral therapies.

PDX-1 acts as a potential molecular target for treatment of human pancreatic cancer

OBJECTIVES

The purpose of this study was to investigate whether pancreatic and duodenal homeobox factor 1 (PDX-1) could serve as a potential molecular target for the treatment of pancreatic cancer.

METHODS

Cell proliferation, invasion capacity, and protein levels of cell cycle mediators were determined in human pancreatic cancer cells transfected with mouse PDX-1 (mPDX-1) alone or with mPDX-1 short hairpin RNA (shRNA) and/or human PDX-1 shRNA (huPDX-1 shRNA). Tumor cell growth and apoptosis were also evaluated in vivo in PANC-1 tumor-bearing severe combined immunodeficient mice receiving multiple treatments of intravenous liposomal huPDX-1 shRNA.

RESULTS

mPDX-1 overexpression resulted in the significant increase of cell proliferation and invasion in MIA PaCa2, but not PANC-1 cells. This effect was blocked by knocking down mPDX-1 expression with mPDX-1 shRNA. Silencing of huPDX-1 expression in PANC-1 cells inhibited cell proliferation in vitro and suppressed tumor growth in vivo which was associated with increased tumor cell apoptosis. PDX-1 overexpression resulted in dysregulation of the cell cycle with up-regulation of cyclin D, cyclin E, and Cdk2 and down-regulation of p27.

CONCLUSIONS

PDX-1 regulates cell proliferation and invasion in human pancreatic cancer cells. Down-regulation of PDX-1 expression inhibits pancreatic cancer cell growth in vitro and in vivo, implying its use as a potential therapeutic target for the treatment of pancreatic cancer.

siRNA and shRNA as anticancer agents in a cervical cancer model

We describe the protocols of using siRNAs, or shRNAs delivered by a lentiviral vector, as a means to silence cancer-causing genes. We use cervical cancer as a model to demonstrate the inhibition of the human papillomavirus (HPV) oncogenes E6 and E7 in cervical cancer cells by RNAi and inhibition of the cell growth in vitro and tumor growth in mouse models. The protocols include methods on siRNA and shRNA design, production of lentiviral-vectored shRNA, transfection or transduction of cervical cancer cells with siRNA or shRNA, and detection of the inhibitory effects of siRNA or shRNA both in vitro and in vitro.

RNAi-mediated downregulation of urokinase plasminogen activator receptor inhibits proliferation, adhesion, migration and invasion in oral cancer cells

RNA interference (RNAi) has emerged as an effective method to target specific genes for silencing. Overexpression of urokinase-type plasminogen activator receptor (uPAR) has been implicated in progression and metastasis of oral cancer. In our study, RNAi was introduced to downregulate the expression of uPAR in the highly malignant oral squamous cell carcinoma (OSCC) cells. Our data demonstrated that siRNA targeting of uPAR leads to the efficient and specific inhibition of endogenous uPAR mRNA and protein expression as determined by quantitative real-time RT-PCR and Western blotting. Furthermore, simultaneous silencing of uPAR resulted in a dramatic reduction of tumor cell proliferation activity, adhesion, migration and invasion in vitro compared to the controls. These findings provide further evidence for the involvement of uPAR in a variety of cancer key cellular events as a versatile signaling orchestrator, and suggest that RNAi-directed targeting of uPAR can be used as a potent and specific therapeutic tool for the treatment of oral cancer, especially in inhibiting and/or preventing cancer cell invasion and metastasis.

Biocompatibility of Agarose Gel as a Dermal Filler: Histologic Evaluation of Subcutaneous Implants

BACKGROUND

The search for safe and effective tissue fillers has been an ongoing effort in plastic and cosmetic surgery over recent decades. Biocompatibility is a prerequisite for any substance to be used as an implant material, and potential biomaterials need to be characterized by histologic evaluation of tissue responses. Collagen is a well-known tissue filler. Agarose gel is widely used in bioengineering. Both products are considered biocompatible. The purpose of this study was to evaluate the bioactivity of agarose gel as a dermal filler compared with collagen.

METHODS

Tissue responses to agarose gel and collagen were evaluated in a rat in vivo model (n = 96). Four groups were evaluated: group 1 (n = 24), rats with agarose gel implants; group 2 (n = 24), rats with collagen implants; group 3, a placebo group (n = 24); and group 4, a control group (n = 24). Responses and biocompatibility were assessed by histopathologic and histomorphometric evaluation at 1 week to 8 months after implantation.

RESULTS

Agarose gel showed marked bioactivity and biodegradation, although the implants integrated well into tissues: newly formed collagen bands were observed inside the implants and no granulomas were detected. Collagen implants showed low cell infiltration and a significant loss of product over time.

CONCLUSIONS

Agarose gel is a biocompatible product that can be considered for use as a tissue filler. Further investigation is required to assess its long-term efficacy and safety.

Topical matrix-based siRNA silences local gene expression in a murine wound model

The ability to affect gene expression via topical therapy has profound therapeutic implications for conditions characterized by open wounds including cutaneous neoplasms, thermal injury, skin disorders and dysfunctional wound healing. Specifically targeting local gene expression avoids systemic toxicity and simplifies treatment. We have developed a new method of topical matrix-based short interfering RNA application to precisely and effectively silence local gene expression in nondelimited wounds.

Environmental risk factors for prevention and molecular intervention of cervical cancer

Cervical cancer (CC) is potentially the most preventable and treatable cancer in human but it is a leading cause for cancer morbidity and mortality in women around the world. Therefore, more innovative prevention and treatment protocols need to be developed and implemented. With better understanding of the etiology of the disease, specific prevention protocols that involve life-style modifications to minimize the impact of environmental risk factors can be developed. It may be necessary to implement unique modification protocols for different countries. In addition, antiviral vaccine is a highly promising prevention approach. With respect to therapy, the development of more specific protocols that have fewer side effects is needed. With the availability of sophisticated molecular techniques, a new generation of targeted approach that has the potential to generate outstanding efficacy is being tested. Using the siRNA technology against the expression of human papillomavirus oncogenes, specific biological pathways that are essential to the growth and survival of the CC cells can be interrupted. Another promising approach is the molecular intervention of the estrogen pathway by blocking the expression of estrogen receptors. These molecular techniques may work by reactivating endogenous regulatory processes, e.g., the core apoptotic machinery, that can cause self-destruction of the CC cells, thus providing potentially effective molecular therapy. These topics are discussed in this review.

Inhibition of growth of cervical cancer cells using a dominant negative estrogen receptor gene

OBJECTIVE

Estrogen stimulates human papilloma virus oncogene expression, promotes cervical cancer (CC) cell proliferation and prevents apoptosis. Therefore, blockage of estrogen function may have therapeutic application to CC.

METHODS

CasKi CC cells were transfected with an adenovirus expressing a dominant negative estrogen receptor gene (Ad-ER-DN) and their responses were investigated by RT-PCR, Flow Cytometry and Western blot assays.

RESULT

Transfected cells showed disturbance of cell colony morphology, reduced HPV E6 and E7 mRNA, interruption of cell proliferation, reduced cyclin D1 protein and expression of apoptosis.

CONCLUSION

We report, for the first time, the use of Ad-ER-DN to block estrogen receptors which led to dramatic changes in CC cells that are consistent with the possible reactivation of cellular p53 and Rb function. Their reactivation most likely allowed the recognition of existing chromosome abnormalities as a serious stress signal and the initiation of a cascade of cellular events in response to the stress, including the activation of the core apoptotic machinery which led to self-destruction of the CC cells.

Targeting the heat shock factor 1 by RNA interference: a potent tool to enhance hyperthermochemotherapy efficacy in cervical cancer

Carcinoma of the uterine cervix is one of the highest causes of mortality in female cancer patients worldwide, and improved treatment options for this type of malignancy are highly needed. Local hyperthermia has been successfully used in combination with systemic administration of cisplatin-based chemotherapy in phase I/II clinical studies. Heat-induced expression of cytoprotective and antiapoptotic heat shock proteins (HSP) is a known complication of hyperthermia, resulting in thermotolerance and chemoresistance and hindering the efficacy of the combination therapy. Heat shock transcription factor 1 (HSF1) is the master regulator of heat-induced HSP expression. In the present report, we used small interfering RNA (siRNA) to silence HSF1 and to examine the effect of HSF1 loss of function on the response to hyperthermia and cisplatin-based chemotherapy in HeLa cervical carcinoma. We have identified the 322-nucleotide to 340-nucleotide HSF1 sequence as an ideal target for siRNA-mediated HSF1 silencing, have created a pSUPER-HSF1 vector able to potently suppress the HSF1 gene, and have generated for the first time human cancer cell lines with stable loss of HSF1 function. We report that, although it surprisingly does not affect cancer cell sensitivity to cisplatin or elevated temperatures up to 43 degrees C when administered separately, loss of HSF1 function causes a dramatic increase in sensitivity to hyperthermochemotherapy, leading to massive (>95%) apoptosis of cancer cells. These findings indicate that disruption of HSF1-induced cytoprotection during hyperthermochemotherapy may represent a powerful strategy to selectively amplify the damage in cancer cells and identify HSF1 as a promising therapeutic target in cervical carcinoma.

Innovative nanotechnologies for the delivery of oligonucleotides and siRNA

One way to reach intracellular therapeutic targets in cells consists in the use of short nucleic acids which will bind specifically to on targets thanks to either Watson-Crick base pairing or protein nucleic acids recognition rules. Among these short nucleic acids an important class of therapeutic agents is antisense oligonucleotides and siRNAs. However, the major problem of nucleic acids is their poor stability in biological media. One method, among others, to solve the stability problem is the use of colloïdal carriers such as nanoparticles. Nanoparticles have already been applied with success to in vitro drug delivery to particular types of cells and in vivo in several experimental models. Many membrane and intracellular processes deal with nanosized structure (typically 100 nm) which are processed further through the recognition sites of receptors and enzymes. Thus non-viral nanoparticles are interesting candidates to present biochemical molecules such as nucleic acids and proteins to cells as well as to protect them in vivo during delivery. This review focuses on the recent developments in the design of nanotechnologies to improve the delivery of antisense oligonucleotides and siRNAs.

Inhibition of cervical cancer cell growth in vitro and in vivo with lentiviral-vector delivered short hairpin RNA targeting human papillomavirus E6 and E7 oncogenes

In this study, we investigated the suppressive effect of a short hairpin RNA delivered by a lentiviral vector (LV-shRNA) against human papillomavirus (HPV) type 18 E6 on the expression of the oncogenes E6 and E7 in cervical cancer HeLa cells both in vitro and in vivo. The LV-shRNA effectively delivered the shRNA to HeLa cells and lead to a dose-dependent reduction of E7 protein and the stabilization of E6 target proteins, p53 and p21. Low-dose infection of HeLa cells with LV-shRNA caused reduced cell growth and the induction of senescence, whereas a high-dose infection resulted in specific cell death via apoptosis. Transplant of HeLa cells infected with a low dose of LV-shRNA into Rag-/- mice significantly reduced the tumor weight, whereas transplant of cells infected with a high dose resulted in a complete loss of tumor growth. Systemic delivery of LV-shRNA into mice with established HeLa cell lung metastases led to a significant reduction in the number of tumor nodules. Our data collectively suggest that lentiviral delivery is an effective way to achieve stable suppression of E6/E7 oncogene expression and induce inhibition of tumor growth both in vitro and in vivo. These results encourage further investigation of this form of RNA interference as a promising treatment for cervical cancer.

Cancer-specific functions of SIRT1 enable human epithelial cancer cell growth and survival

SIRT1 is a conserved NAD-dependent deacetylase that regulates life span in accord with nutritional provision. In mammalian cells, SIRT1 also down-regulates stress-induced p53 and FoxO pathways for apoptosis, thus favoring survival under stress. The functioning of SIRT1 under normal, nonstressed conditions of cell growth is unknown. Here we have asked if SIRT1 has the capacity to influence cell viability in the absence of applied stress. For this purpose we used synthetic small interfering RNA to silence SIRT1 gene expression by RNA interference (RNAi). We show that the process of RNAi, by itself, does not affect cell growth and is not sufficient to activate a cellular stress response (indicated by lack of activation of endogenous p53). We also show that, in the absence of applied stress, SIRT1 silencing induces growth arrest and/or apoptosis in human epithelial cancer cells. In contrast, normal human epithelial cells and normal human diploid fibroblasts seem to be refractory to SIRT1 silencing. Combined gene knockout with RNAi cosilencing experiments indicate that SIRT1 and Bcl-2 may suppress separable apoptotic pathways in the same cell lineage and that the SIRT1-regulated pathway is independent of p53, Bax, and caspase-2. Alternatively, SIRT1 may suppress apoptosis downstream from these apoptotic factors. In either case, we show that FoxO4 (but not FoxO3) is required as proapoptotic mediator. We further identify caspase-3 and caspase-7 as downstream executioners of SIRT1/FoxO4-regulated apoptosis. Our work identifies SIRT1 as a novel target for selective killing of cancer versus noncancer epithelial cells.

RNA interference: from gene silencing to gene-specific therapeutics

In the past 4 years, RNA interference (RNAi) has become widely used as an experimental tool to analyse the function of mammalian genes, both in vitro and in vivo. By harnessing an evolutionary conserved endogenous biological pathway, first identified in plants and lower organisms, double-stranded RNA (dsRNA) reagents are used to bind to and promote the degradation of target RNAs, resulting in knockdown of the expression of specific genes. RNAi can be induced in mammalian cells by the introduction of synthetic double-stranded small interfering RNAs (siRNAs) 21–23 base pairs (bp) in length or by plasmid and viral vector systems that express double-stranded short hairpin RNAs (shRNAs) that are subsequently processed to siRNAs by the cellular machinery. RNAi has been widely used in mammalian cells to define the functional roles of individual genes, particularly in disease. In addition, siRNA and shRNA libraries have been developed to allow the systematic analysis of genes required for disease processes such as cancer using high throughput RNAi screens. RNAi has been used for the knockdown of gene expression in experimental animals, with the development of shRNA systems that allow tissue-specific and inducible knockdown of genes promising to provide a quicker and cheaper way to generate transgenic animals than conventional approaches. Finally, because of the ability of RNAi to silence disease-associated genes in tissue culture and animal models, the development of RNAi-based reagents for clinical applications is gathering pace, as technological enhancements that improve siRNA stability and delivery in vivo, while minimising off-target and nonspecific effects, are developed.

RNA interference-directed knockdown of urokinase plasminogen activator and urokinase plasminogen activator receptor inhibits prostate cancer cell invasion, survival, and tumorigenicity in vivo

The invasive ability of tumor cells plays a key role in prostate cancer metastasis and is a major cause of treatment failure. Urokinase plasminogen activator-(uPA) and its receptor (uPAR)-mediated signaling have been implicated in tumor cell invasion, survival, and metastasis in a variety of cancers. This study was undertaken to investigate the biological roles of uPA and uPAR in prostate cancer cell invasion and survival, and the potential of uPA and uPAR as targets for prostate cancer therapy. uPA and uPAR expression correlates with the metastatic potential of prostate cancer cells. Thus, therapies designed to inhibit uPA and uPAR expression would be beneficial. LNCaP, DU145, and PC3 are prostate cancer cell lines with low, moderate, and high metastatic potential, respectively, as demonstrated by their capacity to invade the extracellular matrix. In this study we utilized small hairpin RNAs (shRNAs), also referred to as small interfering RNAs, to target human uPA and uPAR. These small interfering RNA constructs significantly inhibited uPA and uPAR expression at both the mRNA and protein levels in the highly metastatic prostate cancer cell line PC3. Our data demonstrated that uPA-uPAR knockdown in PC3 cells resulted in a dramatic reduction of tumor cell invasion as indicated by a Matrigel invasion assay. Furthermore, simultaneous silencing of the genes for uPA and uPAR using a single plasmid construct expressing shRNAs for both uPA and uPAR significantly reduced cell viability and ultimately resulted in the induction of apoptotic cell death. RNA interference for uPA and uPAR also abrogated uPA-uPAR signaling to downstream target molecules such as ERK1/2 and Stat 3. In addition, our results demonstrated that intratumoral injection with the plasmid construct expressing shRNAs for uPA and uPAR almost completely inhibited established tumor growth and survival in an orthotopic mouse prostate cancer model. These findings uncovered evidence of a complex signaling network operating downstream of uPA-uPAR that actively advances tumor cell invasion, proliferation, and survival of prostate cancer cells. Thus, RNA interference-directed targeting of uPA and uPAR is a convenient and novel tool for studying the biological role of the uPA-uPAR system and raises the potential of its application for prostate cancer therapy.

Clinical potential of inhibitors of survival pathways and activators of apoptotic pathways in treatment of cervical cancer: changing the apoptotic balance

Cervical cancer is the most common gynaecological malignant disorder worldwide. The best possible treatment of locally advanced cervical cancer is a combination of radiation and cisplatin-based chemotherapy. However, 5-year overall survival is still only 52%. To improve treatment results, research should focus on the discovery of innovative drug strategies. Drugs directed at inducing tumour-cell apoptosis are regarded as important treatment modalities. Here, we present an overview of the molecular options that can change the apoptotic balance in cervical cancer, through increasing death-receptor-mediated apoptosis, the use of proteasome inhibitors, short interfering RNAs, or non-steroidal anti-inflammatory drugs (NSAIDs). Furthermore, the potential of attacking prosurvival signalling through the epidermal-growth-factor receptor and insulin-like-growth-factor receptor to support the apoptotic process is discussed. Additional research is needed to elucidate the clinical potential of these compounds in the treatment of cervical cancer.

Sensitivity to Fas-mediated apoptosis in high-risk HPV-positive human cervical cancer cells: relationship with Fas, caspase-8, and Bid

OBJECTIVE

Binding of Fas ligand or agonistic anti-Fas antibody to the death receptor Fas can activate a caspase-cascade resulting in apoptosis. In the present study, the functionality of the Fas pathway was studied in human cervical cancer cells with different HPV and p53 status.

METHODS

HeLa (HPV-18 positive), CaSki, and SiHa (both HPV-16 positive) contain wild-type p53, while C33A (HPV negative) expresses mutant p53. Fas cell surface expression was determined by flow cytometry. Expression of proteins involved in the apoptotic pathway was analyzed by Western blotting and apoptosis was measured by acridine orange staining of nuclear chromatin.

RESULTS

Despite high Fas membrane expression in the HPV-positive cells, CaSki was highly sensitive, HeLa slightly sensitive, and SiHa and C33A were resistant for agonistic anti-Fas antibody. Almost undetectable Fas membrane levels can explain the non-responsiveness of C33A for anti-Fas. Although interferon-gamma (IFNgamma) strongly and cisplatin to a lesser extend enhanced Fas membrane expression in all HPV-positive cells, sensitization to anti-Fas by IFNgamma or cisplatin was only observed in HeLa. Analysis of the Fas apoptotic pathway showed that anti-Fas treatment induced caspase-8 activation and concomitantly Bid cleavage, caspase-9 and caspase-3 activation, PARP cleavage and apoptosis in HeLa and CaSki. IFNgamma plus anti-Fas treatment, in contrast to anti-Fas alone, facilitated caspase-8 activation in HeLa and SiHa, while an increase in Bid cleavage, caspase-9 activation and apoptosis was only observed in HeLa. Apoptotic failure in SiHa (even in the presence of IFNgamma) was probably due to low caspase-8, almost undetectable Bid protein levels and therefore lack of caspase-9 activation.

CONCLUSION

Sensitivity to anti-Fas depends on Fas, caspase-8, and Bid protein levels in cervical cancer cells. Additionally, IFNgamma and cisplatin can increase sensitivity to anti-Fas in a subset of HPV-positive cervical cancer cell lines by upregulation of Fas and caspase-8 expression without major changes in p53 levels.