Intravenous injection of siRNA directed against hypoxia-inducible factors prolongs survival in a Lewis lung carcinoma cancer model

Principle, application and challenges of development siRNA-based therapeutics against bacterial and viral infections: a comprehensive review

While significant progress has been made in understanding and applying gene silencing mechanisms and the treatment of human diseases, there have been still several obstacles in therapeutic use. For the first time, ONPATTRO, as the first small interfering RNA (siRNA) based drug was invented in 2018 for treatment of hTTR with polyneuropathy. Additionally, four other siRNA based drugs naming Givosiran, Inclisiran, Lumasiran, and Vutrisiran have been approved by the US Food and Drug Administration and the European Medicines Agency for clinical use by hitherto. In this review, we have discussed the key and promising advances in the development of siRNA-based drugs in preclinical and clinical stages, the impact of these molecules in bacterial and viral infection diseases, delivery system issues, the impact of administration methods, limitations of siRNA application and how to overcome them and a glimpse into future developments.

Small interference (RNAi) technique: Exploring its clinical applications, benefits and limitations

BACKGROUND

Small interference RNA (siRNA) has emerged as the most desired method for researchers and clinicians who wish to silence a specific gene of interest and has been extensively developed as a therapeutic agent. This review points to collecting all clinical trials on siRNA and understanding its benefits, pharmacokinetics and safety by reading articles published in the last 5 years.

MATERIALS AND METHODS

Searching in the PubMed database using 'siRNA' and 'in vivo' with limits to articles published in the previous 5 years, article type 'clinical trials' and language 'English' to acquire papers on in vivo studies on siRNA approaches. Features of siRNA clinical trials registered at https://clinicaltrials.gov/ were analysed.

RESULTS

So far, 55 clinical studies have been published on siRNA. Many published clinical trials on siRNA showed tolerability, safety and effectiveness in treating cancers like breast, lung, colon, and other organs and other diseases like viral infections and hereditary diseases. Many different routes of administration can silence many genes at the same time. Limitations and uncertainties associated with siRNA treatment include the effectiveness of cellular uptake, precise targeting of the intended tissue or cell and prompt elimination from the body.

CONCLUSIONS

The siRNA or RNAi method will be one of the most critical and influential techniques to fight against many different diseases. Although the RNAi approach has certain advantages, it also has limitations concerning clinical applications. Overcoming these limitations remains a daunting challenge.

Chronic Obstructive Pulmonary Disease and Lung Cancer: Underlying Pathophysiology and New Therapeutic Modalities

Chronic obstructive pulmonary disease (COPD) and lung cancer are major lung diseases affecting millions worldwide. Both diseases have links to cigarette smoking and exert a considerable societal burden. People suffering from COPD are at higher risk of developing lung cancer than those without, and are more susceptible to poor outcomes after diagnosis and treatment. Lung cancer and COPD are closely associated, possibly sharing common traits such as an underlying genetic predisposition, epithelial and endothelial cell plasticity, dysfunctional inflammatory mechanisms including the deposition of excessive extracellular matrix, angiogenesis, susceptibility to DNA damage and cellular mutagenesis. In fact, COPD could be the driving factor for lung cancer, providing a conducive environment that propagates its evolution. In the early stages of smoking, body defences provide a combative immune/oxidative response and DNA repair mechanisms are likely to subdue these changes to a certain extent; however, in patients with COPD with lung cancer the consequences could be devastating, potentially contributing to slower postoperative recovery after lung resection and increased resistance to radiotherapy and chemotherapy. Vital to the development of new-targeted therapies is an in-depth understanding of various molecular mechanisms that are associated with both pathologies. In this comprehensive review, we provide a detailed overview of possible underlying factors that link COPD and lung cancer, and current therapeutic advances from both human and preclinical animal models that can effectively mitigate this unholy relationship.

Evaluation of [18F]FDG/[18F]FLT/[18F]FMISO-based micro-positron emission tomography in detection of liver metastasis in human colorectal cancer

INTRODUCTION

Positron emission tomography (PET) is extensively used in clinical oncology for tumor detection. This study aimed to explore the application of the radiotracers [¹⁸F]fluorodeoxyglucose ([¹⁸F]FDG), 3'-deoxy-3'- [¹⁸F]fluorothymidine ([¹⁸F]FLT), and [¹⁸F]fluoromisonidazole ([¹⁸F]FMISO) in the diagnosis and monitoring of hepatic metastasis in human colorectal cancer (CRC).

METHODS

A mouse model of human CRC with hepatic metastasis was established by intrasplenic implantation of human CRC cell lines LoVo or HCT8. Metastatic potential of these two cell lines was evaluated by wound healing assay in vitro and survival analysis. Uptake of radiotracers between LoVo and HCT8 cells and uptake of radiotracers in the resulting mouse tumor models were examined by in vivo and in vitro experiments. Uptake of each radiotracer in hepatic metastatic lesions was quantified and expressed as standard uptake value (SUV). Protein expression of multiple tumor biomarkers was determined in metastatic lesions. The correlation between tracer uptake and tumor marker expression was evaluated using linear regression.

RESULTS

LoVo cells exhibited a stronger metastatic potential and a higher radiotracer uptake ability than HCT8 cells, as evidenced by significantly greater wound closure percentage, shorter survival, higher incidence of liver metastases, and higher cellular radiotracer levels in LoVo cells or LoVo cell-xenografted mice. SUV values of [¹⁸F]FLT and [¹⁸F]FMISO, but not [¹⁸F]FDG, in LoVo cell-derived metastatic lesions were significantly greater than those in HCT8 lesions. Mechanistically, the expression of MACC1, HIF-1α, and GLUT-1(metastasis associated in colon cancer 1, MACC1; hypoxia-inducible factor 1-alpha, HIF-1α; and glucose transporter 1, GLUT-1, respectively) in LoVo cell-derived metastatic lesions was more effectively induced than in HCT8-derived ones. A linear regression analysis demonstrated significant positive correlations between [¹⁸F]FLT/[¹⁸F]FMISO uptake and tumor biomarker expression in metastatic tissues.

CONCLUSIONS

[¹⁸F]FLT and [¹⁸F]FMISO-based PET imaging may serve as a promising method for early detection and monitoring of hepatic metastasis in patients with CRC.

Levobuipivacaine-Induced Dissemination of A549 Lung Cancer Cells

While anaesthetics are frequently used on cancer patients during surgical procedures, their consequence on cancer progression remains to be elucidated. In this study, we sought to investigate the influence of local anesthetics on lung cancer cell dissemination in vitro and in vivo. A549 human non-small lung cancer cells were treated with various local anaesthetics including ropivacaine, lidocaine, levobupivacaine and bupivacaine. Cell barrier property was assessed using an electric cell-substrate impedance sensing (ECIS) system. The epithelial-to-mesenchymal transition (EMT) of treated cells was studied by immunofluorescence staining. In vitro and in vivo cancer cell dissemination were investigated.Gene expression microarray and quantitative real-time PCR (qrt-PCR) assays were used to identify the genes responsible for levobupivacaine-mediated cancer cell dissemination.The results illustrated that only levobupivacaine induced EMT in the treated cells and also caused the dissemination of cancer cells in vitro. In addition, after intravenous injection, levobupivacaine encouraged cancer cell dissemination in vivo. Gene expression microarray, qrt-PCR and immunoblotting revealed that after levobupivacaine treatment, the hypoxia-inducible factor (HIF)- 2α gene was upregulated in cancer cells. Our findings suggest that levobupivacaine may induce A549 lung cancer cell dissemination both in vitro and in vivo. More specifically, HIF-2α signaling possibly contributes to levobupivacaine-mediated A549 lung cancer cell dissemination.

Correlation of HIF-1α/HIF-2α expression with FDG uptake in lung adenocarcinoma

OBJECTIVES

Hypoxia is a key element involved in the development and progression of tumors. HIF-1α may transiently induce and mediate the response to acute and severe hypoxia, while HIF-2α may induce a longer response and may control the response to chronic and moderate hypoxia. Hypoxia increases the cellular uptake of FDG. Therefore, HIF may play an important role in the process of the cellular uptake of FDG. The aim of this study was to compare HIF-1α/HIF-2α expression with FDG uptake, Glut-1 expression, and prognosis in the patients with lung adenocarcinoma and to investigate the role of HIF-1α/HIF-2α in the uptake of FDG in lung adenocarcinoma.

METHODS

In the current work, we compared the immunohistochemical expression of HIF-1α and HIF-2α in surgical specimens of 44 patients with lung adenocarcinoma. The relationships between HIF-α expression and Glut-1 expression, FDG uptake, and clinicopathological factors, including prognosis, were analyzed.

RESULTS

There was a marginal association between HIF-1α and HIF-2α expressions (P = 0.076). We found a significant correlation between HIF-2α expression and FDG uptake (P = 0.0001). HIF-1α expression showed a marginal association with FDG uptake (P = 0.066). FDG uptake correlated more significantly with HIF-2α expression than with HIF-1α expression. A significant correlation was noticed between Glut-1 expression and both HIF-1α and HIF-2α expressions (P = 0.005 and P = 0.003, respectively). Univariate analysis of disease-free survival demonstrated that FDG uptake and HIF-2α expression, but not HIF-1α expression, were related to recurrence (P < 0.0001).

CONCLUSION

FDG uptake correlated more significantly with HIF-2α expression than with HIF-1α expression, and both FDG uptake and HIF-2α expression, but not HIF-1α expression was correlated with post-operative recurrence in the patients with lung adenocarcinoma. These results suggest that both FDG uptake and HIF-2α expression may represent a more aggressive phenotype and that HIF-2α may play a more important role than HIF-1α in the uptake of FDG in lung adenocarcinoma.

Cancer cell motility is affected through 3D cell culturing and SCF/c-Kit pathway but not by X-irradiation

BACKGROUND AND PURPOSE

Success of radiotherapy is often limited by therapy resistance and metastasis resulting from cancer cell motility. It was tested in vitro whether this cancer cell motility is affected by growth condition, active SCF/c-Kit pathway or X-irradiation.

MATERIALS AND METHODS

Cell motility was measured with BioCoat™ Matrigel™ invasion chamber using four different cancer cell lines (NSCLC: H23, H520, H226 and PrCa: DU145). Cells were grown in 2D or 3D, SCF was knocked down by siRNA and cells were irradiated with 2 or 6Gy.

RESULTS

All cell lines except H520 showed a 2-3-fold increase in cell motility when grown in 3D. This effect was considered to result from the EMT-like change seen when cells were grown in 3D as indicated by the enhanced expression of vimentin and N-cadherin and reduction of E-cadherin. Just the opposite trends were found for H520 cells. Knockdown of SCF was found to result in reduced cell motility for both 2D and 3D. In contrast, X-irradiation did not modulate cell motility neither under 2D nor 3D. In line with this, X-irradiation did neither induce the expression of EMT-associated genes nor SCF.

CONCLUSION

X-irradiation affects neither the expression of important EMT genes such as vimentin, E-cadherin and N-cadherin nor SCF/c-Kit signaling and, as a consequence, does not alter cell motility.

Down-regulating HIF-1α by lentivirus-mediated shRNA for therapy of triple negative breast cancer

Hypoxia is associated with poor response to treatment in various cancers. Hypoxia inducible factor 1 (HIF-1) is a major transcription factor that mediates adaptation of cancer cells to a hypoxic environment and regulates many genes that are involved in key cellular functions, including cell immortalization, stem cell maintenance, autocrine growth/survival, angiogenesis, invasion/metastasis, and resistance to chemotherapy. HIF-1α has been considered as an attractive therapeutic target for cancer treatment, but there is limited success in this research field. In the present study, we designed a recombinant lentivirus containing HIF-1α siRNA, developed stably transfected cell lines, and tested the anticancer effects of the siRNA on cancer cells in vitro and in vivo. Our results indicated that the stable downregulation of HIF-1α reversed chemoresistance, inhibited proliferation, migration and invasion of cancer cells, and slowed down the tumor growth in breast cancer xenograft models. In conclusion, the recombinant lentivirus containing HIF-1α siRNA provides a new avenue for developing novel therapy for triple negative breast cancer.

Nanoparticle-mediated delivery of siRNA for effective lung cancer therapy

Lung cancer is one of the most lethal diseases worldwide, and the survival rate is less than 15% even after the treatment. Unfortunately, chemotherapeutic treatments for lung cancer are accompanied by severe side effects, lack of selectivity and multidrug resistance. In order to overcome the limitations of conventional chemotherapy, nanoparticle-mediated RNA interference drugs represent a potential new approach due to selective silencing effect of oncogenes and multidrug resistance related genes. In this review, we provide recent advancements on nanoparticle-mediated siRNA delivery strategies including lipid system, polymeric system and rigid nanoparticles for lung cancer therapies. Importantly, codelivery of siRNA with conventional anticancer drugs and recent theranostic agents that offer great potential for lung cancer therapy is covered.

Targeting hypoxia in the treatment of small cell lung cancer

Small cell lung cancer (SCLC) is an extremely aggressive disease for which minimal therapeutic improvements have been made over the last few decades. Patients still rely on non-targeted, chemotherapeutic drugs complemented by irradiation. Although initial response is very good, the majority of SCLC patients invariably relapse with therapy-resistant tumours. Despite the link between pathologically low oxygen levels and therapy resistant tumours, hypoxia has gained little attention in the development of novel therapies for SCLC. In contrast, the advantages of targeting hypoxic cells in many other cancer types have been studied extensively. This review describes the reasons for targeting hypoxia in SCLC and outlines strategies undertaken to enhance hypoxic tumour cell death, including the use of bioreductive prodrugs, the targeting of HIF-1α and the induction of cell death through acidosis. Therapy directed towards hypoxic tumour regions has the potential to greatly enhance the response of SCLC tumours to current treatment regimens and represents an area of research in need of greater attention. Such research could lead to the much sought after development of targeted drugs against SCLC tumours.

New basic approach to treat non-small cell lung cancer based on RNA-interference

BACKGROUND

To date the therapy for non-small cell lung cancer (NSCLC) is associated with severe side effects, frustrating outcomes, and does not consider different tumor characteristics. The RNA-interference (RNAi) pathway represents a potential new approach to treat NSCLC. With small interfering ribonucleic acids (siRNAs), it is possible to reduce the expression of proliferation-dependent proteins in tumor cells, leading to their apoptosis. We propose that siRNAs could be adapted to the tumor type and may cause fewer side effects than current therapy.

METHODS

Four NSCLC cell lines were cultured under standard conditions and transfected with three different concentrations of siRNAs targeted against the hypoxia-inducible factors 1α and 2α (HIF1α and HIF2α) and signal transducer and activator of transcription 3 (STAT3). The expression was observed by quantitative real-time polymerase chain reaction and western blots. For the analysis of cell growth three days after transfection, the cell number was detected using a CASY cell counter system.

RESULTS

The results of the silencing of the analyzed factors differ in each cell line. Cell growth was significantly reduced in all cell lines after transfection with HIF1α- and STAT3-siRNA. The silencing of HIF2α resulted in a significant effect on cell growth in squamous, and large-cell lung cancer.

CONCLUSIONS

This study shows that the knockdown and viability to siRNA transfection differ in each tumor type according to the used siRNA. This implies that the tumor types differ among themselves and should be treated differently. Therefore, the authors suggest a possible approach to a more personalized treatment of NSCLC.

Carbon ion radiotherapy of human lung cancer attenuates HIF-1 signaling and acts with considerably enhanced therapeutic efficiency

Carbon ion irradiation is an emerging therapeutic option for various tumor entities. Radiation resistance of solid tumors toward photon irradiation is caused by attenuation of DNA damage in less oxygenated tumor areas and by increased hypoxia-inducible factor (HIF)-1 signaling. Carbon ion irradiation acts independently of oxygen; however, the role of HIF-1 is unclear. We analyzed the effect of HIF-1 signaling after carbon ions in comparison to photons by using biological equivalent radiation doses in a human non-small-cell cancer model. The studies were performed in cultured A549 and H1299 cell lines and in A549 xenografts. Knockdown of HIF-1α in vivo combined with photon irradiation delayed tumor growth (23 vs. 13 d; P<0.05). Photon irradiation induced HIF-1α and target genes, predominantly in oxygenated cells (1.6-fold; P<0.05), with subsequent enhanced tumor angiogenesis (1.7-fold; P<0.05). These effects were not observed after carbon ion irradiation. Micro-DNA array analysis indicated that photons, but not carbon ions, significantly induced components of the mTOR (mammalian target of rapamycin) pathway (gene set enrichment analysis; P<0.01) as relevant for HIF-1α induction. After carbon ion irradiation in vivo, we observed substantially decreased HIF-1α levels (8.9-fold; P<0.01) and drastically delayed tumor growth (P<0.01), an important finding that indicates a higher relative biological effectiveness (RBE) than anticipated from the cell survival data. Taken together, the evidence showed that carbon ions mediate an improved therapeutic effectiveness without tumor-promoting HIF-1 signaling.

[Advances of hypoxia and lung cancer]

肺癌是我国发病率和死亡率增长最快, 对人群健康和生命威胁最大的恶性肿瘤, 其发生发展机制尚未完全清楚。肿瘤的低氧微环境发现于1955年, 而肺癌组织低氧直至2006年才被成功检测到。随着研究的深入, 低氧对肺癌的影响不仅限于对放疗的抵抗作用, 而且还会通过一个重要的促癌分子低氧诱导因子(hypoxia inducible factor, HIF)以及其调节蛋白脯氨酸羟化酶(prolyl hydroxylase domain, PHD)和希佩尔•林道病基因产物(product of von Hippel-Lindau gene, pVHL)对肺癌的发生发展、侵袭转移、化疗耐药以及预后等产生重要的调节作用。因此, 低氧、HIF、PHD和pVHL必将成为十分有潜力的肺癌治疗靶点。

Endotoxin induces proliferation of NSCLC in vitro and in vivo: role of COX-2 and EGFR activation

Lung cancer is frequently complicated by pulmonary infections which may impair prognosis of this disease. Therefore, we investigated the effect of bacterial lipopolysaccharides (LPS) on tumor proliferation in vitro in the non-small cell lung cancer (NSCLC) cell line A549, ex vivo in a tissue culture model using human NSCLC specimens and in vivo in the A549 adenocarcinoma mouse model. LPS induced a time- and dose-dependent increase in proliferation of A549 cells as quantified by MTS activity and cell counting. In parallel, an increased expression of the proliferation marker Ki-67 and cyclooxygenase (COX)-2 was detected both in A549 cells and in ex vivo human NSCLC tissue. Large amounts of COX-2-derived prostaglandin (PG)E(2) were secreted from LPS-stimulated A549 cells. Pharmacological interventions revealed that the proliferative effect of LPS was dependent on CD14 and Toll-like receptor (TLR)4. Moreover, blocking of the epidermal growth factor receptor (EGFR) also decreased LPS-induced proliferation of A549 cells. Inhibition of COX-2 activity in A549 cells severely attenuated both PGE(2) release and proliferation in response to LPS. Synthesis of PGE(2) was also reduced by inhibiting CD14, TLR4 and EGFR in A549 cells. The proliferative effect of LPS on A549 cells could be reproduced in the A549 adenocarcinoma mouse model with enhancement of tumor growth and Ki-67 expression in implanted tumors. In summary, LPS induces proliferation of NSCLC cells in vitro, ex vivo in human NSCLC specimen and in vivo in a mouse model of NSCLC. Pulmonary infection may thus directly induce tumor progression in NSCLC.

Biological characteristics of intratumoral [F-18]‑fluoromisonidazole distribution in a rodent model of glioma

Accurate imaging to identify hypoxic regions in tumors is key for radiotherapy planning. [F-18]‑fluoro-misonidazole ([F-18]-FMISO) is widely used for tumor hypoxia imaging and has the potential to optimize radiotherapy planning. However, the biological characteristics of intratumoral [F-18]-FMISO distribution have not yet been fully investigated. In hypoxic cells, the hypoxia-inducible factor-1 (HIF-1) target proteins that induce cellular proliferation and glucose metabolism, glucose transporter-1 (Glut-1) and hexokinase-II (HK-II), are upregulated. In this study, we determined the intratumoral distribution of [F-18]-FMISO by autoradiography (ARG) and compared it with pimonidazole uptake, expression of Glut-1, tumor proliferative activity (Ki-67 index) and glucose metabolism ([C-14]2-fluoro-2-deoxy-D-glucose uptake; [C-14]-FDG) in a glioma rat model. Five C6 glioma‑bearing rats were injected with [F-18]-FMISO and [C-14]-FDG. After 90 min, the rats were injected with pimonidazole and 60 min later, the rats were sacrificed and tumor tissues were sectioned into slices. The adjacent slices were used for ARG and immunohistochemical (IHC) analyses of pimonidazole, Glut-1 and Ki-67. [F-18]-FMISO ARG images were divided into regions of high [F-18]-FMISO uptake (FMISO+) and low [F-18]-FMISO uptake (FMISO-). Pimonidazole and Glut-1 expression levels, Ki-67 index and [C-14]-FDG distribution were evaluated in the regions of interest (ROIs) placed on FMISO+ and FMISO-. [F-18]-FMISO distribution was generally consistent with pimonidazole distribution. The percentage of positively stained areas (% positive) of Glut-1 in FMISO+ was significantly higher compared to FMISO- (24 ± 8% in FMISO+ and 9 ± 4% in FMISO-; P<0.05). There were no significant differences in Ki-67 index and [C-14]-FDG uptake between FMISO+ and FMISO- (for Ki-67, 10 ± 5% in FMISO+ and 12 ± 5% in FMISO-, P=ns; for [C-14]-FDG, 1.4 ± 0.3% ID/g/kg in FMISO+ and 1.3 ± 0.3% ID/g/kg in FMISO-, P = ns). Intratumoral [F-18]-FMISO distribution reflected tumor hypoxia and expression of the hypoxia‑related gene product Glut-1; it did not, however, reflect tumor proliferation or glucose metabolism. Our findings help elucidate the biological characteristics of intratumoral [F-18]-FMISO distribution that are relevant to radiotherapy planning.

Nonviral pulmonary delivery of siRNA

RNA interference (RNAi) is an important part of the cell's defenses against viruses and other foreign genes. Moreover, the biotechnological exploitation of RNAi offers therapeutic potential for a range of diseases for which drugs are currently unavailable. Unfortunately, the small interfering RNAs (siRNAs) that are central to RNAi in the cytoplasm are readily degradable by ubiquitous nucleases, are inefficiently targeted to desired organs and cell types, and are excreted quickly upon systemic injection. As a result, local administration techniques have been favored over the past few years, resulting in great success in the treatment of viral infections and other respiratory disorders. Because there are several advantages of pulmonary delivery over systemic administration, two of the four siRNA drugs currently in phase II clinical trials are delivered intranasally or by inhalation. The air-blood barrier, however, has only limited permeability toward large, hydrophilic biopharmaceuticals such as nucleic acids; in addition, the lung imposes intrinsic hurdles to efficient siRNA delivery. Thus, appropriate formulations and delivery devices are very much needed. Although many different formulations have been optimized for in vitro siRNA delivery to lung cells, only a few have been reported successful in vivo. In this Account, we discuss both obstacles to pulmonary siRNA delivery and the success stories that have been achieved thus far. The optimal pulmonary delivery vehicle should be neither cytotoxic nor immunogenic, should protect the payload from degradation by nucleases during the delivery process, and should mediate the intracellular uptake of siRNA. Further requirements include the improvement of the pharmacokinetics and lung distribution profiles of siRNA, the extension of lung retention times (through reduced recognition by macrophages), and the incorporation of reversible or stimuli-responsive binding of siRNA to allow for efficient release of the siRNAs at the target site. In addition, the ideal carrier would be biodegradable (to address difficulties with repeated administration for the treatment of chronic diseases) and would contain targeting moieties to enhance uptake by specific cell types. None of the currently available polymer- and lipid-based formulations meet every one of these requirements, but we introduce here several promising new approaches, including a biodegradable, nonimmunogenic polyester. We also discuss imaging techniques for following the biodistribution according to the administration route. This tracking is crucial for better understanding the translocation and clearance of nanoformulated siRNA subsequent to pulmonary delivery. In the literature, the success of pulmonary siRNA delivery is evaluated solely by relief from or prophylaxis against a disease; side effects are not studied in detail. It also remains unclear which cell types in the lung eventually take up siRNA. These are critical issues for the translational use of pulmonary siRNA formulations; accordingly, we present a flow cytometry technique that can be utilized to differentiate transfected cell populations in a mouse model that expresses transgenic enhanced green fluorescence protein (EGFP). This technique, in which different cell types are identified on the basis of their surface antigen expression, may eventually help in the development of safer carriers with minimized side effects in nontargeted tissues.

Small-molecule inhibitors of the HIF pathway and synthetic lethal interactions

INTRODUCTION

Activation of the hypoxia response pathway is a feature of many tumours and is one of the key mechanisms associated with tumour growth, chemoresistance and radioresistance. The major component of the hypoxia response pathway is the heterodimeric transcription factor, hypoxia-inducible factor (HIF), which is upregulated in many human cancers. Therefore, HIF is an attractive therapeutic target and several strategies have been developed to target it.

AREAS COVERED

Approaches used in targeting the hypoxia response pathway are discussed. Reviewed are agents that target upstream, directly and downstream of HIF, as well as some of the challenges in HIF-targeted therapy.

EXPERT OPINION

Many of the therapeutic agents that are in clinical use inhibit downstream HIF target genes, but ideally a molecule specific to HIF will have a more potent effect in inhibiting multiple HIF pathways. However, many anti-HIF molecules have multiple targets, which may increase non-specific cytotoxicity. In addition, many anti-HIF agents cannot discriminate between the different isoforms of HIF-α. So, it is important to assess whether targeting both HIF-1α and HIF-2α or each subunit selectively will provide better therapeutic effects.

Progress toward in vivo use of siRNAs-II

RNA interference (RNAi) has been extensively employed for in vivo research since its use was first demonstrated in mammalian cells 10 years ago. Design rules have improved, and it is now routinely possible to obtain reagents that suppress expression of any gene desired. At the same time, increased understanding of the molecular basis of unwanted side effects has led to the development of chemical modification strategies that mitigate these concerns. Delivery remains the single greatest hurdle to widespread adoption of in vivo RNAi methods. However, exciting advances have been made and new delivery systems under development may help to overcome these barriers. This review discusses advances in RNAi biochemistry and biology that impact in vivo use and provides an overview of select publications that demonstrate interesting applications of these principles. Emphasis is placed on work with synthetic, small interfering RNAs (siRNAs) published since the first installment of this review which appeared in 2006.

Comparison of the effects of carbon ion and photon irradiation on the angiogenic response in human lung adenocarcinoma cells

PURPOSE

Radiotherapy resistance is a commonly encountered problem in cancer treatment. In this regard, stabilization of endothelial cells and release of angiogenic factors by cancer cells contribute to this problem. In this study, we used human lung adenocarcinoma (A549) cells to compare the effects of carbon ion and X-ray irradiation on the cells' angiogenic response.

METHODS AND MATERIALS

A549 cells were irradiated with biologically equivalent doses for cell survival of either carbon ions (linear energy transfer, 170 keV/μm; energy of 9.8 MeV/u on target) or X-rays and injected with basement membrane matrix into BALB/c nu/nu mice to generate a plug, allowing quantification of angiogenesis by blood vessel enumeration. The expression of angiogenic factors (VEGF, PlGF, SDF-1, and SCF) was assessed at the mRNA and secreted protein levels by using real-time reverse transcription-PCR and enzyme-linked immunosorbent assay. Signal transduction mediated by stem cell factor (SCF) was assessed by phosphorylation of its receptor c-Kit. For inhibition of SCF/c-Kit signaling, a specific SCF/c-Kit inhibitor (ISCK03) was used.

RESULTS

Irradiation of A549 cells with X-rays (6 Gy) but not carbon ions (2 Gy) resulted in a significant increase in blood vessel density (control, 20.71 ± 1.55; X-ray, 36.44 ± 3.44; carbon ion, 16.33 ± 1.03; number per microscopic field). Concordantly, irradiation with X-rays but not with carbon ions increased the expression of SCF and subsequently caused phosphorylation of c-Kit in endothelial cells. ISCK03 treatment of A549 cells irradiated with X-rays (6 Gy) resulted in a significant decrease in blood vessel density (X-ray, 36.44 ± 3.44; X-ray and ISCK03, 4.33 ± 0.71; number of microscopic field). These data indicate that irradiation of A549 cells with X-rays but not with carbon ions promotes angiogenesis.

CONCLUSIONS

The present study provides evidence that SCF is an X-ray-induced mediator of angiogenesis in A549 cells, a phenomenon that could not be observed with carbon ion irradiation. Thus, in this model system evaluating angiogenesis, carbon ion irradiation may have a therapeutic advantage. This observation should be confirmed in orthotopic lung tumor models.

Glucose transporter-1 as a new therapeutic target in laryngeal carcinoma

Treatment options for laryngeal carcinoma, one of the most common head and neck malignancies, consist of radiotherapy, surgery, chemotherapy or a combination thereof. The functional treatment of laryngeal carcinoma poses a considerable challenge because of its resistance to chemotherapy and radiotherapy, and its tendency for local recurrence. Finding ways to inhibit the energy supply of malignant tumours is becoming an increasingly attractive proposition. Glucose transporter-1 (Glut-1; encoded by the SLC2A1 gene in humans) is the main transporter of glucose in solid carcinomas and has become a focus of cancer research. Recently, it was shown that the increased expression of SLC2A1 in head and neck carcinomas is correlated with lymph node metastasis, poor survival and clinical stage, and revealed that the suppression of SLC2A1 expression by antisense oligodeoxynucleotides decreased glucose uptake and inhibited the proliferation of Hep-2 cells. Thus, the authors propose the suppression of SLC2A1 expression as a new therapeutic target for laryngeal carcinoma.

Potential clinical applications of siRNA technique: benefits and limitations

BACKGROUND

RNA interference (RNAi) has become the method of choice for researchers wishing to target specific genes for silencing and has provided immense potential as therapeutic tools. This narrative review article aimed to understand potential benefits and limitations of RNAi technique for clinical application and in vivo studies through reading the articles published during the recent 3 years.

MATERIALS AND METHODS

Medline database was searched by using 'siRNA' or 'RNAi' and 'in vivo' with limits of dates 'published in the last 3 years', language 'English' and article type 'clinical trial' for obtaining articles on in vivo studies on the use of RNAi technique. Characteristics of clinical trials on siRNA registered at the http://www.ClinicalTrials.gov were analysed.

RESULTS

The only three clinical studies published so far and many in vivo studies in animals showed that the RNAi technique is safe and effective in treatment of cancers of many organ/systems and various other diseases including viral infection, arterial restenosis and some hereditary diseases with considerable benefits such as high specificity, many possible routes of administration and possibility of silencing multiple genes at the same time. Limitations and uncertainty include efficiency of cellular uptake, specific guidance to the target tissue or cell, long-term safety, sustained efficacy and rapid clearance from the body.

CONCLUSIONS

RNAi technique will become an important and potent weapon for fighting against various diseases. RNAi technique has benefits and limitations in its potential clinical applications. Overcoming the obstacles is still a formidable task.

Prognostic implications of hypoxia-inducible factor-1α in epidermal growth factor receptor-negative non-small cell lung cancer

Hypoxia-inducible factor (HIF)-1α is a regulatory subunit of HIF-1 that is stabilized and activated under hypoxic conditions. In non-small cell lung cancer (NSCLC), over-expression of HIF-1α has been associated with poor overall survival. However, there is conflicting data on the role of HIF-1α as a prognostic factor. Some studies have demonstrated close association between the HIF-1α signal pathways and epidermal growth factor receptors (EGFRs). We evaluated the prognostic significance of HIF-1α expression in 178 NSCLC patients using tissue microarray in the context of EGFR gene copy number and protein expression status. EGFR gene copy number was evaluated using fluorescent in situ hybridization (FISH), and EGFR protein expression was determined using immunohistochemistry (IHC). The difference in overall survival (OS) between HIF-1α-positive and HIF-1α-negative groups was statistically significant in patients with low EGFR gene copy number and negative EGFR expression (log-rank test, P = 0.03). In univariate and multivariate analyses, HIF-1α was a significant worse prognostic factor for OS in patients with low EGFR gene copy number and negative EGFR expression (hazard ratio = 2.992; 95% CI, 1.113-8.045; P = 0.03 in univariate analysis and hazard ratio = 8.127; 95% CI, 1.874-35.251; P < 0.01 in multivariate analysis). The results demonstrated that the prognostic significance of HIF-1α should be validated in the context of EGFR status in NSCLC patients, and the gene and protein status of EGFR and HIF-1α will be important to help select patients most likely to derive the greatest clinical benefit from EGFR or HIF-1α targeted therapies.

Irradiation-dependent effects on tumor perfusion and endogenous and exogenous hypoxia markers in an A549 xenograft model

PURPOSE

Hypoxia is a major determinant of tumor radiosensitivity, and microenvironmental changes in response to ionizing radiation (IR) are often heterogenous. We analyzed IR-dependent changes in hypoxia and perfusion in A549 human lung adenocarcinoma xenografts.

MATERIALS AND METHODS

Immunohistological analysis of two exogenously added chemical hypoxic markers, pimonidazole and CCI-103F, and of the endogenous marker Glut-1 was performed time dependently after IR. Tumor vessels and apoptosis were analyzed using CD31 and caspase-3 antibodies. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and fluorescent beads (Hoechst 33342) were used to monitor vascular perfusion.

RESULTS

CCI-103F signals measuring the fraction of hypoxic areas after IR were significantly decreased by approximately 50% when compared with pimonidazole signals, representing the fraction of hypoxic areas from the same tumors before IR. Interestingly, Glut-1 signals were significantly decreased at early time point (6.5 h) after IR returning to the initial levels at 30.5 h. Vascular density showed no difference between irradiated and control groups, whereas apoptosis was significantly induced at 10.5 h post-IR. DCE-MRI indicated increased perfusion 1 h post-IR.

CONCLUSIONS

The discrepancy between the hypoxic fractions of CCI-103F and Glut-1 forces us to consider the possibility that both markers reflect different metabolic alterations of tumor microenvironment. The reliability of endogenous markers such as Glut-1 to measure reoxygenation in irradiated tumors needs further consideration. Monitoring tumor microvascular response to IR by DCE-MRI and measuring tumor volume alterations should be encouraged.

Current concepts on the role of inflammation in COPD and lung cancer

Chronic obstructive pulmonary disease (COPD) and lung cancer are leading cause of death, and both are associated with cigarette smoke exposure. It has been shown that 50-70% of patients diagnosed with lung cancer suffer from COPD, and reduced lung function is an important event in lung cancer suggesting an association between COPD and lung cancer. However, a causal relationship between COPD and lung tumorigenesis is not yet fully understood. Recent studies have suggested a central role of chronic inflammation in the pathogenesis of both the diseases. For example, immune dysfunction, abnormal activation of NF-kappaB, epithelial-to-mesenchymal transition, altered adhesion signaling pathways, and extracellular matrix degradation/altered signaling are the key underlying mechanisms in both COPD and lung cancer. These parameters along with other processes, such as chromatin modifications/epigenetic changes, angiogenesis, and autophagy/apoptosis are altered by cigarette smoke, are crucial in the development of COPD and lung cancer. Understanding the cellular and molecular mechanisms underlying these processes will provide novel avenues for halting the chronic inflammation in COPD and devising therapeutic strategies against lung cancer.

Oxidative stress induced lung cancer and COPD: opportunities for epigenetic therapy

Reactive oxygen species (ROS) form as a natural by-product of the normal metabolism of oxygen and play important roles within the cell. Under normal circumstances the cell is able to maintain an adequate homeostasis between the formation of ROS and its removal through particular enzymatic pathways or via antioxidants. If however, this balance is disturbed a situation called oxidative stress occurs. Critically, oxidative stress plays important roles in the pathogenesis of many diseases, including cancer. Epigenetics is a process where gene expression is regulated by heritable mechanisms that do not cause any direct changes to the DNA sequence itself, and disruption of epigenetic mechanisms has important implications in disease. Evidence is emerging that histone deacetylases (HDACs) play decisive roles in regulating important cellular oxidative stress pathways including those involved with sensing oxidative stress and those involved with regulating the cellular response to oxidative stress. In particular aberrant regulation of these pathways by HDACs may play critical roles in cancer progression. In this review we discuss the current evidence linking epigenetics and oxidative stress and cancer, using chronic obstructive pulmonary disease and non-small cell lung cancer to illustrate the importance of epigenetics on these pathways within these disease settings.