Guanxin Shen

Phi29 pRNA vector for efficient escort of hammerhead ribozyme targeting survivin in multiple cancer cells

Ribozymes are potential therapeutic agents which suppress specific genes in disease-affected cells. Ribozymes have high substrate cleavage efficiency, yet their medical application has been hindered by RNA degradation, aberrant cell trafficking, or misfolding when fused to a carrier. In this study, we constructed a chimeric ribozyme carried by the motor pRNA of bacteriophage phi29 to achieve proper folding and enhanced stability. A pRNA molecule contains an interlocking loop domain and a 5´/3´ helical domain, which fold independently of one another. When a ribozyme is connected to the helical domain, the chimeric pRNA/ribozyme reorganize into a circularly permuted form, in which the 5´/3´ ends are relocated and buried in the original 71′/75′ positions. Effective silencing of an anti-apoptotic gene survivin by an appropriately designed chimeric ribozyme, as demonstrated at mRNA and protein levels, led to programmed cell death in various human cancer cell lines, including breast, prostate, cervical, nasopharyngeal, and lung, without causing significant non-specific cytotoxicity. Through the interlocking interaction of right and left loops, monomer pRNA/ribozyme chimeras can be incorporated into multi-functional dimer, trimer and hexamer complexes for specific gene delivery. Using the phi29 motor pRNA as an escort may revive the ribozymes strength in medical application again.

Inhibiting the growth of malignant melanoma by blocking the expression of vascular endothelial growth factor using an RNA interference approach

Background  Vascular endothelial growth factor (VEGF) is overexpressed in malignant melanoma (MM).

Hepatitis B Virus Protein X-induced Expression of the CXC Chemokine IP-10 Is Mediated through Activation of NF-κB and Increases Migration of Leukocytes

Interferon-γ inducible protein 10 (IP-10) involves inflammatory cell recruitment and cellular immune damage during virus infection. Although an increase of the peripheral IP-10 level is known in HBV-infected patients, the molecular basis of HBV infection inducing IP-10 expression has remained elusive. In the present study, we demonstrate that hepatitis B virus protein X (HBx) increases IP-10 expression in a dose-dependent manner. Transfection of the HBx-expressing vector into HepG2 cells results in nuclear translocation of NF-κB, which directly binds the promoter of IP-10 at positions from −122 to −113, thus facilitating transcription. The addition of the NF-κB inhibitor blocks the effect of HBx on IP-10 induction. In parallel, increase of NF-κB subunits p65 and p50 in HepG2 cells also augments IP-10 expression. Furthermore, we show that HBx induces activation of NF-κB through the TRAF2/TAK1 signaling pathway, leading to up-regulation of IP-10 expression. As a consequence, up-regulation of IP-10 may mediate the migration of peripheral blood leukocytes in a NF-κB-dependent manner. In conclusion, we report a novel molecular mechanism of HBV infection inducing IP-10 expression, which involves viral protein HBx affecting NF-κB pathway, leading to transactivation of the IP-10 promoter. Our study provides insight into the migration of leukocytes in response to HBV infection, thus causing immune pathological injury of liver.

Transcriptional upregulation of HSP70-2 by HIF-1 in cancer cells in response to hypoxia.

Heat shock protein 70‐2 (HSP70‐2) can be expressed by cancer cells and act as an important regulator of cancer cell growth and survival. Here, we show the molecular mechanisms by which hypoxia regulate HSP70‐2 expression in cancer cells. When cells were subjected to hypoxia (1% O2), the expression of HSP70‐2 had a significant increase in cancer cells. Such increase was due to the direct binding of hypoxia‐inducible factor to hypoxia‐responsive elements (HREs) in the HSP70‐2 promoter. By luciferase assays, we demonstrated that the HRE1 at position −446 was essential for transcriptional activation of HSP70‐2 promoter under hypoxic conditions. We also demonstrated that HIF‐1α binds to the HSP70‐2 promoter and the binding is specific, as revealed by HIF binding/competition and chromatin immunoprecipitation assays. Consequently, the upregulation of HSP70‐2 enhanced the resistance of tumor cells to hypoxia‐induced apoptosis. These findings provide a new insight into how tumor cells overcome hypoxic stress and survive, and also disclose a new regulatory mechanism of HSP70‐2 expression in tumor cells.

Evaluation of specific delivery of chimeric phi29 pRNA/siRNA nanoparticles to multiple tumor cells

The pRNA (packaging RNA) of bacteriophage phi29 DNA packaging motor has been reported to have novel applications in nanotechnology and nanomedicine. The unique ability of pRNA to form dimers, trimers, hexamers and patterned superstructures via the interaction of two reengineered interlocking loops makes it a promising polyvalent vehicle to load siRNA and other therapeutic molecules and be applied as a therapeutic nanoparticle in tumor therapy. In this study, several tumor cell lines were used to evaluate the previously reported pRNA nanotechnology for specific siRNA delivery and for the silencing of targeted genes. It was found that MCF-7 and HeLa cells, out of twenty-five tested tumor cell lines, expressed high levels of folate receptors and exhibited specific binding of the FITC-folate-pRNA nanoparticles, while the others expressed low levels and thus, for these, delivery was not feasible using folate as a targeting agent. Folate receptor positive tumor cells were then incubated with the chimeric pRNA dimer harboring both the folate-pRNA and the chimeric pRNA/siRNA (survivin). Knock down effects of survivin expression in these tumor cells were detected at the mRNA level by real time-PCR and at the protein level by western blot. Apoptosis was detected by flow cytometry analysis with dual staining of annexinV-FITC and PI. The data suggest that the chimeric pRNA nanoparticles containing folate-pRNA and pRNA/siRNA (survivin) could be specifically taken up by tumor cells through folate receptor-mediated endocytosis, resulting in significant inhibition of both transcription and expression of survivin in tumor cells and triggering cell apoptosis. Using such protein-free nanoparticles as therapeutic reagents would not only allow specific gene delivery and extend the in vivo retaining time but also allow long-term administration of therapeutic particles, therefore avoiding the induction of antibodies caused by repeated treatment for chronic diseases.

Targeting Hypoxia-inducible Factor-1α With Tf–PEI–shRNA Complex via Transferrin Receptor–mediated Endocytosis Inhibits Melanoma Growth

Malignant melanoma (MM) is a major public health problem. The development of effective, systemic therapies for MM is highly desired. We showed here that the transferrin receptor (TfR) was a suitable surface marker for targeting of gene therapy in MM and that the hypoxia-inducible factor-1α (HIF-1α) was an attractive therapeutic molecular target in MM. We observed that inhibition of HIF-1α blocked cell proliferation and induced cell apoptosis in vitro. We then showed that a transferrin-polyethylenimine-HIF-1α-short-hairpin RNA (Tf-PEI-HIF-1α-shRNA) complex could target MM specifically and efficiently both in vivo and in vitro, exploiting the high expression of the TfR in MM. The systemic delivery of sequence-specific small-interfering RNA (siRNA) against HIF-1α by the Tf- PEI-HIF-1α-shRNA complex dramatically inhibited tumor growth in the A375 MM xenograft model. The underlying concept of transfecting a HIF-1α shRNA expression vector complexed with Tf-PEI to block HIF-1α holds promise as a clinical approach to gene therapy for MM.Malignant melanoma (MM) is a major public health problem. The development of effective, systemic therapies for MM is highly desired. We showed here that the transferrin receptor (TfR) was a suitable surface marker for targeting of gene therapy in MM and that the hypoxia-inducible factor-1alpha (HIF-1alpha) was an attractive therapeutic molecular target in MM. We observed that inhibition of HIF-1alpha blocked cell proliferation and induced cell apoptosis in vitro. We then showed that a transferrin-polyethylenimine-HIF-1alpha-short-hairpin RNA (Tf-PEI-HIF-1alpha-shRNA) complex could target MM specifically and efficiently both in vivo and in vitro, exploiting the high expression of the TfR in MM. The systemic delivery of sequence-specific small-interfering RNA (siRNA) against HIF-1alpha by the Tf- PEI-HIF-1alpha-shRNA complex dramatically inhibited tumor growth in the A375 MM xenograft model. The underlying concept of transfecting a HIF-1alpha shRNA expression vector complexed with Tf-PEI to block HIF-1alpha holds promise as a clinical approach to gene therapy for MM.

The effects of PDL-Ig on collagen-induced arthritis

Programmed death ligand (PDL) is a new member of the B7 family of costimulatory molecules that specifically interacts with programmed death 1 (PD-1) expressed on activated T cells, B cells, and myeloid cells. Collagen II (CII)-induced arthritis (CIA) is an experimental model of arthritis that has been used to dissect the pathogenesis of human rheumatoid arthritis. In this study, we have investigated the effects of PDL-Ig on CIA. Administration of PDL-Ig significantly ameliorated the disease as assessed by clinical arthritis score and histology in the joints. Expression of proinflammatory cytokines, such as IL-17 and IL-23, in the serum was reduced by PDL-Ig treatment. These results showed a beneficial effect of PDL-Ig on CIA through anti-inflammatory actions and inhibition of cell proliferation in response to CII, suggesting that the PD-1-PDL pathway may be involved in the pathogenesis of CIA, and thus PDL-Ig may be a useful therapy for the improvement of human rheumatoid arthritis.

Cytotoxicity of BSA‐Stabilized Gold Nanoclusters: In Vitro and In Vivo Study

Gold nanoclusters (Au NCs) are one of the most promising fluorescent nanomaterials for bioimaging, targeting, and cancer therapy due to their tunable optical properties, yet their biocompatibility still remains unclear. Herein, the cytotoxicity of bovine serum albumin (BSA)-stabilized Au NCs is studied by using three tumor cell lines and two normal cell lines. The results indicate that Au NCs induce the decline of cell viabilities of different cell lines to varying degrees in a dose- and time-dependent manner, and umbilical vein endothelial cells which had a higher intake of Au NCs than melanoma cells show more toxicity. Addition of free BSA to BSA-Au NCs solutions can relieve the cytotoxicity, implying that BSA can prevent cell damage. Moreover, Au NCs increase intracellular reactive oxygen species (ROS) production, further causing cell apoptosis. Furthermore, N-acetylcysteine, a ROS scavenger, partially reverses Au NCs-induced cell apoptosis and cytotoxicity, indicating that ROS might be one of the primary reasons for the toxicity of BSA-Au NCs. Surprisingly, Au NCs with concentrations of 5 and 20 nM significantly inhibit tumor growth in the xenograft mice model of human liver cancer, which might provide a new avenue for the design of anti-cancer drug delivery vehicles.

Interleukin-32 expression induced by hepatitis B virus protein X is mediated through activation of NF-κB.

HBV replicates noncytopathically in hepatocytes, but HBV or proteins encoded by HBV genome could induce cytokines, chemokines expression by hepatocytes. Moreover, liver damage in patients with HBV infection is immune-mediated and cytokines play important roles in immune-mediated liver damage after HBV infection. Interleukin-32 (IL-32) is a proinflammatory cytokine and plays a critical role in inflammation. However, the role of HBV in IL-32 expression remains unclear. In the present study, we demonstrate that hepatitis B virus protein X (HBx) increases IL-32 expression through the promoter of IL-32 at positions from -746 to +25 and in a dose-dependent manner. Furthermore, we demonstrate that increase of NF-κB subunits p65 and p50 in Huh7 cells also augments IL-32 expression, and the NF-κB inhibitor blocks the effect of HBx on IL-32 induction. These results indicate that NF-κB activation is required for HBx-induced IL-32 expression. In conclusion, IL-32 is induced by HBx in Huh7 cells. Our results suggest that IL-32 might play an important role in inflammatory response after HBV infection.

The role of hepatitis B virus X protein is related to its differential intracellular localization

Chronic hepatitis B virus (HBV) infection has been strongly associated with hepatocellular carcinoma. HBV encodes an oncogenic hepatitis B virus X protein (HBx), which is a multifunctional regulator that modulates signal transduction, transcription, cell cycle progress, protein degradation, apoptosis, and genetic stability through direct and indirect interaction with host factors. The subcellular localization of HBx is primarily cytoplasmic, with a small fraction in the nucleus. In addition, high levels of HBx expression lead to an abnormal mitochondrial distribution. The dynamic distribution of HBx could be important to the multiple functions of HBx at different stages of the HBV life cycle. This short review presents an overview of the differential roles of HBx as a function of its intracellular localization.