Administration of PLK-1 small interfering RNA with atelocollagen prevents the growth of liver metastases of lung cancer

Phenylboronic Acid-Modified Polyamidoamine Mediated the Transfection of Polo-Like Kinase-1 siRNA to Achieve an Anti-Tumor Efficacy

Background

The construction of tumor-targeting carriers with favorable transfection efficiency was of great significance to achieve the tumor gene therapy. The phenylboronic acid-modified polyamidoamine (namely PP) was employed as a carrier for the delivery of Polo-like kinase-1 siRNA (siPlk-1), inducing an obvious anti-tumor response.

Materials and Methods

The interaction between PP and siPlk-1 was evaluated by gel retardation assay. The transfection efficiency and tumor-targeting ability were analyzed by flow cytometry and confocal laser scanning microscopy, using hepatocarcinoma cell line HepG2 as a model. The anti-proliferation effect of PP/siPlk-1 and related mechanism were studied using the strategies of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, cell apoptosis and cell cycle arrest. The anti-migration effect induced by PP/siPlk-1 delivery was assayed by wound healing and Transwell migration techniques. Finally, quantitative real-time PCR and Western blotting were performed to measure the expression level of Plk-1 and other key targets.

Results

The derivative PP could achieve the condensation of siPlk-1 into stable nanoparticles at nitrogen/phosphate groups ratio (N/P ratio) of >3.0, and it could facilitate the transfection of siPk-1 in a phenylboronic acid-dependent manner. The PP/siPlk-1 nanoparticles exhibited obvious anti-proliferation effect owing to the gene silence of Plk-1, which was identified to be associated with the cell apoptosis and cell cycle arrest at G2 phase. Meanwhile, PP/siPlk-1 transfection could efficiently suppress the migration and invasion of tumor cells.

Conclusion

The derivative PP has been demonstrated to be an ideal tumor-targeting carrier for the delivery of Plk-1 siRNA, exhibiting great potential in the gene therapy of malignant tumors.

Repurposing cationic amphiphilic drugs as adjuvants to induce lysosomal siRNA escape in nanogel transfected cells

Cytosolic delivery remains a major bottleneck for siRNA therapeutics. To facilitate delivery, siRNAs are often enclosed in nanoparticles (NPs). However, upon endocytosis such NPs are mainly trafficked towards lysosomes. To avoid degradation, cytosolic release of siRNA should occur prior to fusion of endosomes with lysosomes, but current endosomal escape strategies remain inefficient. In contrast to this paradigm, we aim to exploit lysosomal accumulation by treating NP-transfected cells with low molecular weight drugs that release the siRNA from the lysosomes into the cytosol. We show that FDA-approved cationic amphiphilic drugs (CADs) significantly improved gene silencing by siRNA-loaded nanogels in cancer cells through simple sequential incubation. CADs induced lysosomal phospholipidosis, leading to transient lysosomal membrane permeabilization and improved siRNA release without cytotoxicity. Of note, the lysosomes could be applied as an intracellular depot for triggered siRNA release by multiple CAD treatments.

Atelocollagen-mediated in vivo siRNA transfection in ovarian carcinoma is influenced by tumor site, siRNA target and administration route

Ovarian cancer is the leading cause of death from gynecological malignancies worldwide, and innate or acquired chemoresistance of ovarian cancer cells is the major cause of therapeutic failure. It has been demonstrated that the concomitant inhibition of Bcl-xL and Mcl-1 anti-apoptotic activities is able to trigger apoptosis in chemoresistant ovarian cancer cells. In this context, siRNA-mediated Bcl‑xL and Mcl-1 inhibition constitutes an appealing strategy by which to eliminate chemoresistant cancer cells. However, the safest and most efficient way to vectorize siRNAs in vivo is still under debate. In the present study, using in vivo bioluminescence imaging, we evaluated the interest of atelocollagen to vectorize siRNAs by intraperitoneal (i.p.) or intravenous (i.v.) administration in 2 xenografted ovarian cancer models (peritoneal carcinomatosis and subcutaneous tumors in nude mice). Whereas i.p. administration of atelocollagen-vectorized siRNA in the peritoneal carcinomatosis model did not induce any gene downregulation, a 70% transient downregulation of luciferase expression was achieved after i.v. injection of atelocollagen-vectorized siRNA in the subcutaneous (s.c.) model. However, the use of siRNA targeting Bcl-xL or Mcl-1 did not induce target-specific downregulation in vivo in nude mice. Our results therefore show that atelocollagen complex formulation, the administration route, tumor site and the identity of the siRNA target influence the efficiency of atelocollagen‑mediated siRNA delivery.

Performance of Pyridylthiourea-Polyethylenimine Polyplex for siRNA-Mediated Liver Cancer Therapy in Cell Monolayer, Spheroid, and Tumor Xenograft Models

Medical application of siRNAs relies on methods for delivering nucleic acids into the cytosol. Synthetic carriers, which assemble with nucleic acids into delivery systems, show promises for cancer therapy but efficiency remains to be improved. In here, the effectiveness of pyridylthiourea-polyethylenimine (πPEI), a siRNA carrier that favors both polyplex disassembly and endosome rupture upon sensing the acidic endosomal environment, in 3 experimental models of hepatocellular cancer is tested. The πPEI-assisted delivery of a siRNA targeting the polo-like kinase 1 into Huh-7 monolayer produces a 90% cell death via a demonstrated RNA interference mechanism. Incubation of polyplex with Huh-7 spheroids leads to siRNA delivery into the superficial first cell layer and a 60% reduction in spheroid growth compared to untreated controls. Administration of polyplexes into mice bearing subcutaneous implanted Huh-7Luc tumors results in a reduced tumor progression, similar to the one observed in the spheroid model. Altogether, these results support the in vivo use of synthetic and dedicated polymers for increasing siRNA-mediated gene knockdown, and their clinical promise in cancer therapeutics.

Silencing Myostatin Using Cholesterol-conjugated siRNAs Induces Muscle Growth

Short interfering RNAs (siRNAs) are a valuable tool for gene silencing with applications in both target validation and therapeutics. Many advances have recently been made to improve potency and specificity, and reduce toxicity and immunostimulation. However, siRNA delivery to a variety of tissues remains an obstacle for this technology. To date, siRNA delivery to muscle has only been achieved by local administration or by methods with limited potential use in the clinic. We report systemic delivery of a highly chemically modified cholesterol-conjugated siRNA targeting muscle-specific gene myostatin (Mstn) to a full range of muscles in mice. Following a single intravenous injection, we observe 85–95% knockdown of Mstn mRNA in skeletal muscle and >65% reduction in circulating Mstn protein sustained for >21 days. This level of Mstn knockdown is also accompanied by a functional effect on skeletal muscle, with animals showing an increase in muscle mass, size, and strength. The cholesterol-conjugated siRNA platform described here could have major implications for treatment of a variety of muscle disorders, including muscular atrophic diseases, muscular dystrophy, and type II diabetes.

Cross Talk between Wnt/β-Catenin and CIP2A/Plk1 Signaling in Prostate Cancer: Promising Therapeutic Implications

Aberrant activation of the Wnt/β-catenin pathway and polo-like kinase 1 (Plk1) overexpression represent two common events in prostate cancer with relevant functional implications. This minireview analyzes their potential therapeutic significance in prostate cancer based on their role as androgen receptor (AR) signaling regulators and the pivotal role of the tumor suppressor protein phosphatase 2A (PP2A) modulating these pathways.

Daphnetin inhibits invasion and migration of LM8 murine osteosarcoma cells by decreasing RhoA and Cdc42 expression

Daphnetin, 7,8-dihydroxycoumarin, present in main constituents of Daphne odora var. marginatai, has multiple pharmacological activities including anti-proliferative effects in cancer cells. In this study, using a Transwell system, we showed that daphnetin inhibited invasion and migration of highly metastatic murine osteosarcoma LM8 cells in a dose-dependent manner. Following treatment by daphnetin, cells that penetrated the Transwell membrane were rounder than non-treated cells. Immunofluorescence analysis revealed that daphnetin decreased the numbers of intracellular stress fibers and filopodia. Moreover, daphnetin treatment dramatically decreased the expression levels of RhoA and Cdc42. In summary, the dihydroxycoumarin derivative daphnetin inhibits the invasion and migration of LM8 cells, and therefore represents a promising agent for use against metastatic cancer.

Powering up the molecular therapy of RNA interference by novel nanoparticles

With more suitable for disease treatment due to reduced cellular toxicity, higher loading capacity, and better biocompatibility, nanoparticle-based siRNA delivery systems have proved to be more potent, higher specific and less toxic than the traditional drug therapy.

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.

Polo-like kinase 1 inhibitor BI2536 causes mitotic catastrophe following activation of the spindle assembly checkpoint in non-small cell lung cancer cells

Polo-like kinase 1 (PLK1), a critical kinase that regulates multiple steps in mitosis, is overexpressed in diverse human cancers; thus many PLK1 inhibitors have been developed as potential cancer therapeutic agents. One of these compounds, the PLK1-specific inhibitor BI2536, has been investigated as a cytotoxic drug in several cancers, including lung cancer; however, the detailed mechanism by which BI2536 induces defects in cell proliferation of non-small cell lung cancer (NSCLC) has not yet been determined. We found that BI2536 treatment resulted in mitotic arrest due to improper formation of the mitotic spindles and mitotic centrosomes. The unattached kinetochores in BI2536-treated NSCLC cells activated the spindle assembly checkpoint (SAC). The prolonged activation of the SAC led to a type of apoptotic cell death referred to as mitotic catastrophe. Finally, BI2536-treated NSCLC cells show a defect in cell proliferation. Overall, these data indicate that PLK1 inhibition via mitotic disruption represents a potential approach for the treatment of NSCLC.

Optimized effective charge density and size of polyglycerol amines leads to strong knockdown efficacy in vivo

The balance between core size, multiplicity and effective charge density plays an important role for the development of potent siRNA delivery systems.

Recent In Vivo Evidences of Particle-Based Delivery of Small-Interfering RNA (siRNA) into Solid Tumors

Small-interfering RNA (siRNA) is both a powerful tool in research and a promising therapeutic platform to modulate expression of disease-related genes. Malignant tumors are attractive disease targets for nucleic acid-based therapies. siRNA directed against oncogenes, and genes driving metastases or angiogenesis have been evaluated in animal models and in some cases, in humans. The outcomes of these studies indicate that drug delivery is a significant limiting factor. This review provides perspectives on in vivo validated nanoparticle-based siRNA delivery systems. Results of recent advances in liposomes and polymeric and inorganic formulations illustrate the need for mutually optimized attributes for performance in systemic circulation, tumor interstitial space, plasma membrane, and endosomes. Physiochemical properties conducive to efficient siRNA delivery are summarized and directions for future research are discussed.

Multimodality imaging of RNA interference

The discovery of small interfering RNAs (siRNAs) and their potential to knock down virtually any gene of interest has ushered in a new era of RNA interference (RNAi). Clinical use of RNAi faces severe limitations due to inefficiency delivery of siRNA or short hairpin RNA (shRNA). Many molecular imaging techniques have been adopted in RNAi-related research for evaluation of siRNA/shRNA delivery, biodistribution, pharmacokinetics, and the therapeutic effect. In this review article, we summarize the current status of in vivo imaging of RNAi. The molecular imaging techniques that have been employed include bioluminescence/fluorescence imaging, magnetic resonance imaging/ spectroscopy, positron emission tomography, single-photon emission computed tomography, and various combinations of these techniques. Further development of non-invasive imaging strategies for RNAi, not only focusing on the delivery of siRNA/shRNA but also the therapeutic efficacy, is critical for future clinical translation. Rigorous validation will be needed to confirm that biodistribution of the carrier is correlated with that of siRNA/shRNA, since imaging only detects the label (e.g. radioisotopes) but not the gene or carrier themselves. It is also essential to develop multimodality imaging approaches for realizing the full potential of therapeutic RNAi, as no single imaging modality may be sufficient to simultaneously monitor both the gene delivery and silencing effect of RNAi.

In vivo delivery of siRNA targeting vasohibin-2 decreases tumor angiogenesis and suppresses tumor growth in ovarian cancer

Vasohibin-2 (VASH2) is a homolog of vasohibin-1 and exhibits pro-angiogenic activity. We recently reported that VASH2 is expressed in certain ovarian cancers and promotes tumor growth through angiogenesis. To further demonstrate the effectiveness of molecular targeting of VASH2 for anticancer treatment, we applied in vivo delivery of siRNA targeting VASH2 (siVASH2) using atelocollagen to a xenograft model of ovarian cancer. We inoculated mice s.c. with DISS and SKOV-3, two representative human ovarian serous adenocarcinoma cell lines. When tumors were measurable, we initiated treatment with control or siVASH2 mixed with atelocollagen, which enveloped the whole tumor. Treatment with siVASH2 significantly inhibited s.c. tumor growth by abrogating tumor angiogenesis. We confirmed that expression of VASH2 mRNA in the tumor was downregulated by siVASH2 treatment. In addition, the siVASH2-treated tumor contained more blood vessels covered with pericytes, indicating that knockdown of VASH2 contributes to the normalization of tumor blood vessels. Based on these results, VASH2 may be a promising molecular target for ovarian cancer treatment.

Lentiviral-mediated RNA interference targeting the PLK1 gene inhibits invasion and metastasis of esophageal squamous cell carcinoma cells

AIM: To investigate the inhibitory effect of lentiviral-mediated RNA interference targeting the PLK1 gene on invasion and metastasis of esophageal squamous cell carcinoma (ESCC) cells.

METHODS: RT-PCR and Western blot were used to detect the expression of PLK1 mRNA and protein in different ESCC cells. Based on the mRNA sequence of human PLK1 gene, interference fragments were designed, and interference efficiency was detected by Western blot. The in vitro effect of PLK1 siRNA on migration and invasion of ESCC cells was assessed by wound-healing assay and Matrigel chemoinvasion assay. The most efficient interference fragment was cloned into the lentiviral vector pGLV/H1/GFP+Puro and sequenced. The resulting recombinant lentiviral vector and packaging plasmids were transfected into 293T cells, and packaged virus particles were used to infect ESCC cells. Interference efficiency was assessed using fluorescence quantitative PCR and Western blot. The in vivo effect of recombinant lentiviral vector on invasion and metastasis of ESCC cells was studied using a nude mouse model of pulmonary metastasis.

RESULTS: The ESCC cell line TE-8 overexpressed PLK1, and the most efficient PLK1 siRNA could obviously inhibit migration and invasion of TE-8 cells in vitro. The lentiviral vector for RNA interference targeting the PLK1 gene was successfully constructed. The prepared recombinant virus particles could infect TE-8 cells and significantly inhibit the metastasis of ESCC cells in vivo.

CONCLUSION: Lentiviral-mediated RNA interference targeting PLK1 could obviously inhibit invasion and metastasis of ESCC cells. PLK1 may promote the malignant development of ESCC.

Polycation-based nanoparticle delivery of RNAi therapeutics: adverse effects and solutions

Small interfering RNA (siRNA) that silence genes by the process of RNA interference offers a new therapeutic modality for disease treatment. Polycation-based nanoparticles termed polyplexes have been developed to maximise extracellular and intracellular siRNA delivery, a key requirement for enabling the clinical translation of RNAi-based drugs. Medical applications are dependent on safety; therefore, detailed investigation into potential toxicity to the cell or organism is required. This review addresses potential adverse effects arising from cellular and tissue interactions, immune stimulation and altered gene expression that can be associated with the assembled polyplex or the polycation and siRNA component parts. A greater understanding of the cellular mechanisms involved allows design-based solutions for rationale development of safe, effective and clinically relevant polyplex-based RNAi drugs.

RNAi-based nanomedicines for targeted personalized therapy

RNA interference (RNAi) has just made it through the pipeline to clinical trials. However, in order for RNAi to serve as an ideal personalized therapeutics and be clinically approved-safe, specific, and potent strategies must be devised for efficient delivery of RNAi payloads to specific cell types, which despite the immense potential, remains a challenge. Through evaluating the recent reported studies in this field, we introduce the progress in designing targeted nano-scaled strategies that are anticipated to overcome the delivery drawbacks and along with the exciting "omics" discipline to personalize RNAi-based therapeutics.

Influence of systemic administration of atelocollagen on mouse livers: an ideal biomaterial for systemic drug delivery

Atelocollagen (AC), a biomaterial with low antigenicity and high bioaffinity, has been widely used in implantable materials in clinical practice. Preclinical studies have demonstrated that AC is a potential drug carrier for local and systemic delivery of cytokines, growth factors, plasmid DNA, small interfering RNA, and microRNA. AC is also believed to have low systemic toxicity on the basis of the safety of implant usage; however, this is not enough determined. Therefore, we performed whole genome expression profiling in mouse liver after systemic administration of AC or the cationic liposome carrier DOTAP/cholesterol (LP) and compared the changes of gene expressions associated with hepatotoxicity. Microarray analysis revealed that systemic LP administration significantly increased expression of toxicity-related genes, i.e., those for lipocalin-2, cyclin-dependent kinase inhibitor 1A, serum amyloid A isoforms, chemokine ligands, and granzyme B. Alternatively, AC administration did not alter the expression of any of these genes. Further gene ontology (GO) enrichment analysis highlighted the characteristic annotations extracted from genes upregulated after LP administration, and most of them were related to toxicity annotations such as immune response, inflammatory response, and apoptosis induction. In contrast, GO enrichment analysis of genes induced after AC administration revealed that only three annotations, all of which were unrelated to toxicity. These findings indicate that AC is potentially far less hepatotoxic than LP after systemic administration, suggesting that AC may be an excellent biomaterial for nontoxic drug delivery system carriers.

Effects of atelocollagen formulation containing oligonucleotide on endothelial permeability

Atelocollagen is a major animal protein that is used as a highly biocompatible biomaterial. To date, atelocollagen has been used as an effective drug delivery technology to sustain the release of antitumor proteins and to enhance the antitumor activity of oligonucleotides in in vivo models. However, the biological effects of this technology are not fully understood. In the present study, we investigated the effects of atelocollagen on endothelial paracellular barrier function. An atelocollagen formulation containing oligonucleotides specifically increased the permeability of two types of endothelial cells, and the change was dependent on the molecular size, structure of the oligonucleotides used and the concentrations of the oligonucleotide and atelocollagen in the formulation. An immunohistochemical examination revealed that the formulation had effects on the cellular skeleton and intercellular structure although it did not affect the expression of adherens junction or tight junction proteins. These changes were induced through p38 MAP kinase signaling. It is important to elucidate the biological functions of atelocollagen in order to be able to exploit its drug delivery properties.

AV-65, a novel Wnt/β-catenin signal inhibitor, successfully suppresses progression of multiple myeloma in a mouse model

Multiple myeloma (MM) is a malignant neoplasm of plasma cells. Although new molecular targeting agents against MM have been developed based on the better understanding of the underlying pathogenesis, MM still remains an incurable disease. We previously demonstrated that β-catenin, a downstream effector in the Wnt pathway, is a potential target in MM using RNA interference in an in vivo experimental mouse model. In this study, we have screened a library of more than 100 000 small-molecule chemical compounds for novel Wnt/β-catenin signaling inhibitors using a high-throughput transcriptional screening technology. We identified AV-65, which diminished β-catenin protein levels and T-cell factor transcriptional activity. AV-65 then decreased c-myc, cyclin D1 and survivin expression, resulting in the inhibition of MM cell proliferation through the apoptotic pathway. AV-65 treatment prolonged the survival of MM-bearing mice. These findings indicate that this compound represents a novel and attractive therapeutic agent against MM. This study also illustrates the potential of high-throughput transcriptional screening to identify candidates for anticancer drug discovery.

Atelocollagen-mediated systemic delivery prevents immunostimulatory adverse effects of siRNA in mammals

Short interfering RNA (siRNA) is a potent activator of the mammalian innate immune system. When considering possible clinical applications of siRNA for humans, the adverse immunostimulatory effects must also be taken into account. Here, we show that atelocollagen-mediated systemic delivery of siRNA without chemical modifications did not cause any immunostimulation in both animals and human peripheral blood mononuclear cells (PBMCs), even if the siRNA harbored an interferon (IFN)-inducible sequence. In contrast, systemic delivery of immunostimulatory RNA (isRNA)-mediated by a cationic lipid (such as Invivofectamine) induced potent type-I IFNs and inflammatory cytokines. Regarding the mechanism by which the isRNA/atelocollagen complex avoided adverse effects on immunostimulation, we revealed that this complex was not incorporated into PBMCs. On the other hand, Invivofectamine delivered isRNA into PBMCs. The use of either atelocollagen or Invivofectamine as a vehicle elicited significant and undistinguishable therapeutic effects in a contact hypersensitivity (CHS) inflammatory model mouse, when we intravenously injected the siRNA targeting monocyte chemoattractant protein-1 as the complex. For the goal of realizing siRNA-based medicines for humans, atelocollagen is an excellent and promising delivery vehicle, and it has the useful advantage of evading detection by the "radar" of innate immunity.

Polo-like kinase 1 inhibitors and their potential role in anticancer therapy, with a focus on NSCLC

Cytotoxic platinum-doublet chemotherapy that includes antimitotic agents is a current standard of care in advanced non-small cell lung cancer (NSCLC). Microtubule-targeting antimitotics, taxanes, and Vinca alkaloids are effective anticancer therapeutics that affect both dividing and nondividing cells. A new generation of antimitotic agents that target regulatory proteins-mitotic kinases and kinesins-has the potential to overcome the limitations related to the role of tubulin in nondividing cells that are associated with traditional antimitotics. This review concentrates on Polo-like kinase 1, a key regulator of mitosis, outlines a rationale for its development as an anticancer target, and discusses data from preclinical and clinical studies of Plk1 inhibitors with a particular focus on NSCLC.

siRNA targeting Livin decreases tumor in a xenograft model for colon cancer

AIM: To evaluate the effect of silencing Livin gene expression with siRNA to apoptosis and proliferation in a colon cancer cell line.

METHODS: To investigate the anticancer effect of silencing Livin gene expression, we established an siRNA transfected cell line using the HCT116 colon cancer cell line. After confirming the successful transfection, MTT assay, flow cytometry and annexin V staining were employed to evaluate the antiapoptotic effect. To confirm the in vivo effect of Livin-siRNA, different doses of Livin-siRNA were injected into xenografted tumors in BALB/c nude mice model.

RESULTS: Livin expression was dramatically decreased after siRNA transfection, especially at 25 μmol/L of siRNA, but this suppression was not dose-dependent. The cell count at 18 h after transfection was significantly reduced as compared with controls (P < 0.01), but tended not to decrease proportionally depending on transfected dose or time. MTT assay revealed that silencing the Livin gene suppressed cellular proliferation at 18 h after transfection (P = 0.04); however, the inhibitory effect disappeared thereafter. Also, there was no significant difference in cellular proliferation depending on siRNA dose. The rate of apoptosis also increased with silencing of the Livin gene. In vivo, the tumor size significantly decreased after Livin-siRNA injection at 20 μmol/L concentration (P = 0.03). There were no significant body weight changes of mice after siRNA injection. Histologic examination revealed no significant toxic reaction in kidney, liver and brain of mice.

CONCLUSION: siRNA-mediated downregulation of Livin expression can induce apoptosis in colon cancer in vitro and in vivo, which suggests the possibility of new cancer therapeutics using siRNA.

Protein kinase D3 sensitizes RAF inhibitor RAF265 in melanoma cells by preventing reactivation of MAPK signaling

RAS mutations occur in more than 30% of all human cancers but efforts to directly target mutant RAS signaling as a cancer therapy have yet to succeed. As alternative strategies, RAF and MEK inhibitors have been developed to block oncogenic signaling downstream of RAS. As might be expected, studies of these inhibitors have indicated that tumors with RAS or BRAF mutations display resistance RAF or MEK inhibitors. In order to better understand the mechanistic basis for this resistance, we conducted a RNAi-based screen to identify genes that mediated chemoresistance to the RAF kinase inhibitor RAF265 in a BRAF (V600E) mutant melanoma cell line that is resistant to this drug. In this way, we found that knockdown of protein kinase D3 (PRKD3) could enhance cell killing of RAF and MEK inhibitors across multiple melanoma cell lines of various genotypes and sensitivities to RAF265. PRKD3 blockade cooperated with RAF265 to prevent reactivation of the MAPK signaling pathway, interrupt cell cycle progression, trigger apoptosis, and inhibit colony formation growth. Our findings offer initial proof-of-concept that PRKD3 is a valid target to overcome drug resistance being encountered widely in the clinic with RAF or MEK inhibitors.

RNA interference against polo-like kinase-1 in advanced non-small cell lung cancers

Worldwide, approximately one and a half million new cases of lung cancer are diagnosed each year, and about 85% of lung cancer are non-small cell lung cancer (NSCLC). As the molecular pathogenesis underlying NSCLC is understood, new molecular targeting agents can be developed. However, current therapies are not sufficient to cure or manage the patients with distant metastasis, and novel strategies are necessary to be developed to cure the patients with advanced NSCLC.RNA interference (RNAi) is a phenomenon of sequence-specific gene silencing in mammalian cells and its discovery has lead to its wide application as a powerful tool in post-genomic research. Recently, short interfering RNA (siRNA), which induces RNAi, has been experimentally introduced as a cancer therapy and is expected to be developed as a nucleic acid-based medicine. Recently, several clinical trials of RNAi therapies against cancers are ongoing. In this article, we discuss the most recent findings concerning the administration of siRNA against polo-like kinase-1 (PLK-1) to liver metastatic NSCLC. PLK-1 regulates the mitotic process in mammalian cells. These promising results demonstrate that PLK-1 is a suitable target for advanced NSCLC therapy.

Tailoring nanostructured solid-lipid carriers for time-controlled intracellular siRNA kinetics to sustain RNAi-mediated chemosensitization

Use of siRNA for silencing major oncogenic/chemoresistance targets such as survivin has strong potential for cancer therapy. However, a key clinical limitation is their short action, preventing them from sustaining their therapeutic RNA-interference activity for optimal chemosensitization. This issue is tackled from the perspective of intracellular siRNA kinetics using a novel lipid-based "nanostructured siRNA carrier" (NSC), which incorporates variable amount of oil phase into the solid-lipid matrix to modify its siRNA release behaviors. We demonstrate that by manipulating the degradation responses of NSC device to lysosomal enzyme, tailoring of intracellular siRNA kinetics is achievable. A tailored NSC design delivering survivin-siRNA can extend the survivin knockdown period to 9 days, translating into steady, effective in vitro and in vivo chemosensitization of prostate cancer to docetaxel for over a week. All in all, this new NSC design provides a convenient mean to set up a clinically more appealing weekly or longer dosing cycle for siRNA therapy, which addresses a significant unmet need for prostate cancer treatment and is potentially useful for other chronic disease conditions as well.

Allograft inflammatory factor-1 is overexpressed and induces fibroblast chemotaxis in the skin of sclerodermatous GVHD in a murine model

Allograft inflammatory factor (AIF)-1 has been identified in chronic rejection of rat cardiac allografts and is thought to be involved in the immune response. We previously showed that AIF-1 was strongly expressed in synovial tissues in rheumatoid arthritis and that rAIF-1 increased the IL-6 production of synoviocytes and peripheral blood mononuclear cells. Recently, the expression of AIF-1 has been reported in systemic sclerosis (SSc) tissues, whose clinical features and histopathology are similar to those of chronic graft-vs-host disease (GVHD). To clarify the pathogenic mechanism of fibrosis, we examined the expression and function of AIF in sclerodermatous (Scl) GVHD mice. We demonstrated that immunoreactive AIF-1 and IL-6 were significantly expressed in infiltrating mononuclear cells and fibroblasts in thickened skin of Scl GVHD mice compared with control. The immunohistochemical findings were confirmed by Western blot analysis. Wound healing assay also revealed that rAIF-1 increased the migration of normal human dermal fibroblasts (NHDF) directly, but cell growth assay did not show that rAIF-1 increased the proliferation of them. These findings suggest that AIF-1, which can induce the migration of fibroblasts and the production of IL-6 in affected skin tissues, is an important molecule promoting fibrosis in GVHD. Although the biological function of AIF-1 has not been completely elucidated, AIF-1 can induce IL-6 secretion on mononuclear cells and fibroblast chemotaxis. AIF-1 may accordingly provide an attractive new target for antifibrotic therapy in SSc as well as Scl GVHD.

A combination of a DNA-chimera siRNA against PLK-1 and zoledronic acid suppresses the growth of malignant mesothelioma cells in vitro

Although novel agents effective against malignant mesothelioma (MM) have been developed, the prognosis of patients with MM is still poor. We generated a DNA-chimeric siRNA against polo-like kinase-1 (PLK-1), which was more stable in human serum than the non-chimeric siRNA. The chimeric PLK-1 siRNA inhibited MM cell proliferation through the induction of apoptosis. Next, we investigated the effects of zoledronic acid (ZOL) on MM cells, and found that ZOL also induced apoptosis in MM cells. Furthermore, ZOL augmented the inhibitory effects of the PLK-1 siRNA. In conclusion, combining a PLK-1 siRNA with ZOL treatment is an attractive strategy against MM.

Overexpression of Plk1 promotes malignant progress in human esophageal squamous cell carcinoma

PURPOSE

Plk1, belonging to a family of serine/threonine kinases, is involved in spindle formation and chromosome segregation during mitosis and therefore, in the regulation of cell cycle. Plk1 was found to be overexpressed in various human tumors. In the present work, we investigated the expression of human esophageal squamous cell carcinoma (ESCC) to determine whether Plk1 has a role in malignant progress.

METHODS

Immunohistochemistry and Western blotting were performed to define the expressions of Plk1 in ESCC tissues and normal adjacent tissues. Transfection of cells with small interference RNA, growth suppression assay, and Transwell assay were used to determine the potential role of Plk1 in ESCC malignant progress.

RESULTS

Plk1 was overexpressed in 69.6% of the ESCC tissues. In addition, the extent of Plk1 expression was closely correlated with differentiation grades and invasiveness in ESCC. We also found that the downregulation of endogenous Plk1 in human ESSC cell lines Eca-109 and EC9706 significantly decreased cells proliferation and migrating ability.

CONCLUSIONS

Our results show that Plk1 expression is elevated in ESCC tissues and is associated with differentiation grades and invasiveness in ESCC, indicating that overexpression of Plk1 may play an important role in carcinogenesis and malignant progress of ESCC.

Targeted depletion of Polo-like kinase (Plk) 1 through lentiviral shRNA or a small-molecule inhibitor causes mitotic catastrophe and induction of apoptosis in human melanoma cells

Melanoma, one of the most lethal forms of skin cancer, remains resistant to currently available treatments. Therefore, additional target-based approaches are needed for the management of this neoplasm. Polo-like kinase 1 (Plk1) has been shown to be a crucial regulator of mitotic entry, progression, and exit. Elevated Plk1 level has been associated with aggressiveness of several cancer types and with poor disease prognosis. However, the role of Plk1 in melanoma is not well established. Here, we show that Plk1 is overexpressed in both clinical tissue specimens and cultured human melanoma cells (WM115, A375, and HS294T) when compared with normal skin tissues and cultured normal melanocytes, respectively. Furthermore, Plk1 gene knockdown through Plk1-specific shRNA or its activity inhibition by a small-molecule inhibitor resulted in a significant decrease in the viability and growth of melanoma cells without affecting normal human melanocytes. In addition, Plk1 inhibition resulted in a significant (i) decrease in clonogenic survival, (ii) multiple mitotic errors, (iii) G(2)/M cell-cycle arrest, and (iv) apoptosis of melanoma cells. This study suggests that Plk1 may have a functional relevance toward melanoma development and/or progression. We suggest that the targeting of Plk1 may be a viable approach for the treatment of melanoma.

The expression of PLK-1 in cervical carcinoma: a possible target for enhancing chemosensitivity

BACKGROUND

Polo-like kinase-1 (PLK-1) is reported to be upregulated in a variety of human tumors and is implicated in cell proliferation and survival. However, its importance in cervical carcinoma has not yet been fully elucidated.

METHODS

We examined PLK-1 expression in cervical carcinoma tissues using immunohistochemical staining. Furthermore, we blocked PLK-1 expression in HeLa cells using specific siRNA and detected the cell cycle, cell proliferation and chemosensitivity using western blotting, MTT and flow cytometry.

RESULTS

We provide evidence that expression of PLK-1 exists in human cervical carcinoma tissues and establish an association with tumor size. Furthermore, we show that PLK-1 knockdown by transfection of siRNA induces accumulation of HeLa cells in the G2/M cell cycle phase and enhances cisplatin-induced apoptosis.

CONCLUSION

Our results indicate that PLK-1 production in HeLa cells might be critical in determining whether cells survive or undergo apoptosis. Therefore, targeting PLK-1 might be a promising strategy for enhancing sensitivity to chemotherapeutic reagents in cervical carcinoma.

Delivery of RNA interference therapeutics using polycation-based nanoparticles

RNAi-based therapies are dependent on extracellular and intracellular delivery of RNA molecules for enabling target interaction. Polycation-based nanoparticles (or polyplexes) formed by self-assembly with RNA can be used to modulate pharmacokinetics and intracellular trafficking to improve the therapeutic efficacy of RNAi-based therapeutics. This review describes the application of polyplexes for extracellular and intracellular delivery of synthetic RNA molecules. Focus is given to routes of administration and silencing effects in animal disease models. The inclusion of functional components into the nanoparticle for controlling cellular trafficking and RNA release is discussed. This work highlights the versatile nature of polycation-based nanoparticles to fulfil the delivery requirements for RNA molecules with flexibility in design to evolve alongside an expanding repertoire of RNAi-based drugs.

beta-catenin small interfering RNA successfully suppressed progression of multiple myeloma in a mouse model

PURPOSE

beta-catenin is the downstream effector of the Wnt signaling pathway, and it regulates cell proliferation. beta-catenin overexpression correlates positively with prognosis in several types of malignancies. We herein assessed its effects on growth of multiple myeloma cells using a xenograft model.

EXPERIMENTAL DESIGN

We first investigated the expression of beta-catenin in multiple myeloma cell lines and multiple myeloma cells obtained from patients. Next, we investigated the growth inhibitory effects of beta-catenin small interfering RNA on the growth of multiple myeloma cells in vivo. Six-week-old male BALB/c nu/nu mice were inoculated s.c. in the right flank with 5 x 10(6) RPMI8226 cells, followed by s.c. injections of beta-catenin small interfering RNA, scramble small interfering RNA, or PBS/atelocollagen complex twice a week for a total of eight injections.

RESULTS

Significantly higher levels of beta-catenin expression were observed in multiple myeloma cell lines and in samples from patients with multiple myeloma than those found in mononuclear cells obtained from healthy volunteers. In in vivo experiments, no inhibitory effects were observed following treatment with scramble small interfering RNA or PBS/atelocollagen complexes, whereas treatment with beta-catenin small interfering RNA/atelocollagen complex significantly inhibited growth of multiple myeloma tumors (P < 0.05).

CONCLUSIONS

beta-catenin small interfering RNA treatment inhibited the growth of multiple myeloma tumors in a xenograft model. To our knowledge, this is the first report showing that the treatment with beta-catenin small interfering RNA produces an inhibitory effects on growth of hematologic malignancies in vivo. Because treatment with beta-catenin small interfering RNA inhibited growth of multiple myeloma cells, beta-catenin is the attractive novel target for treating multiple myeloma.

Involvement of BH3-only proteins in hematologic malignancies

The interaction between anti-apoptotic and pro-apoptotic members of the Bcl-2 family proteins determines life or death for cancer cells. In this context, BH3-only proteins (such as Bim), members of the pro-apoptotic Bcl-2 family proteins, act as key initiators of apoptosis by activating Bax and Bak through liberating them from anti-apoptotic Bcl-2 members. This then leads to the disruption of mitochondrial outer membrane, and eventually promotes proteolytic cascades for cellular dismantling. We here review the growing evidence of how BH3-only proteins are involved in tumorigenesis and in apoptosis induced by anti-cancer agents in hematologic malignancies. A deeper understanding of the roles of BH3-only proteins in cell death regulation may yield crucial insights for the further development of more effective and rational cell killing strategies. Recent developments in the direct therapeutic manipulation of Bcl-2 proteins using BH3-mimicking agents, such as ABT-737 or GX15-070, for hematologic malignancies are also summarized.