Combination therapy with VEGFR2 and EGFR siRNA enhances the antitumor effect of cisplatin in non-small cell lung cancer xenografts

Recent Advances in RNA-Targeted Cancer Therapy

Ribonucleic acid (RNA) plays a pivotal role in gene regulation and protein biosynthesis. Interfering the physiological function of key RNAs to induce cell apoptosis holds great promise for cancer treatment. Many RNA-targeted anti-cancer strategies have emerged continuously. Among them, RNA interference (RNAi) has been recognized as a promising therapeutic modality for various disease treatments. Nevertheless, the primary obstacle in siRNA delivery-escaping the endosome and crossing the plasma membrane severely impedes its therapeutic potential. Thus far, a variety of nanosystems as well as carrier-free bioconjugation for siRNA delivery have been developed and employed to enhance the drug delivery and anti-tumor efficiency. Besides, the use of small molecules to target specific RNA structures and disrupt their function, along with the covalent modification of RNA, has also drawn tremendous attention recently owing to high therapeutic efficacy. In this review, we will provide an overview of recent progress in RNA-targeted cancer therapy including various siRNA delivery strategies, RNA-targeting small molecules, and newly emerged covalent RNA modification. Finally, challenges and future perspectives faced in this research field will be discussed.

Exploiting Nanomedicine for Cancer Polychemotherapy: Recent Advances and Clinical Applications

The most important limitations of chemotherapeutic agents are severe side effects and the development of multi-drug resistance. Recently, the clinical successes achieved with immunotherapy have revolutionized the treatment of several advanced-stage malignancies, but most patients do not respond and many of them develop immune-related adverse events. Loading synergistic combinations of different anti-tumor drugs in nanocarriers may enhance their efficacy and reduce life-threatening toxicities. Thereafter, nanomedicines may synergize with pharmacological, immunological, and physical combined treatments, and should be increasingly integrated in multimodal combination therapy regimens. The goal of this manuscript is to provide better understanding and key considerations for developing new combined nanomedicines and nanotheranostics. We will clarify the potential of combined nanomedicine strategies that are designed to target different steps of the cancer growth as well as its microenvironment and immunity interactions. Moreover, we will describe relevant experiments in animal models and discuss issues raised by translation in the human setting.

A bivalent cyclic RGD-siRNA conjugate enhances the antitumor effect of apatinib via co-inhibiting VEGFR2 in non-small cell lung cancer xenografts

The vascular endothelial growth factor receptor 2 (VEGFR2) is considered to be a pivotal target for anti-tumor therapy against angiogenesis of non-small cell lung cancer (NSCLC). However, effective and low-toxicity targeted therapies to inhibit VEGFR2 are still lacking. Here, biRGD–siVEGFR2 conjugate comprising murine VEGFR2 siRNA and [cyclo(Arg-Gly-Asp-D-Phe-Lys)-Ahx]₂-Glu-PEG-MAL (biRGD) peptide which selectively binds to integrin αvβ3 receptors expressing on neovascularization endothelial cell was synthesized. The anti-tumor activity and renal toxicity of biRGD–siVEGFR2 or its combination therapy with low-dose apatinib were investigated on NSCLC xenografts. The immunogenicity of biRGD–siVEGFR2 was also evaluated in C57BL/6J mice. In vivo, intravenously injected biRGD–siVEGFR2 substantially inhibited NSCLC growth with a marked reduction of vessels and a down-regulation of VEGFR2 in tumor tissue. Furthermore, biRGD–siVEGFR2 in combination with low-dose apatinib achieved powerful anti-tumor effect with less nephrotoxicity compared with the regular dose of apatinib. Besides, no obvious immunogenicity of biRGD–siVEGFR2 was found. These findings demonstrate that biRGD–siVEGFR2 conjugate can be used as a new candidate for the treatment of NSCLC and its combination therapy with apatinib may also provide a novel strategy for cancer treatment in clinic.

Employing siRNA tool and its delivery platforms in suppressing cisplatin resistance: Approaching to a new era of cancer chemotherapy

Although chemotherapy is a first option in treatment of cancer patients, drug resistance has led to its failure, requiring strategies to overcome it. Cancer cells are capable of switching among molecular pathways to ensure their proliferation and metastasis, leading to their resistance to chemotherapy. The molecular pathways and mechanisms that are responsible for cancer progression and growth, can be negatively affected for providing chemosensitivity. Small interfering RNA (siRNA) is a powerful tool extensively applied in cancer therapy in both pre-clinical (in vitro and in vivo) and clinical studies because of its potential in suppressing tumor-promoting factors. As such oncogene pathways account for cisplatin (CP) resistance, their targeting by siRNA plays an important role in reversing chemoresistance. In the present review, application of siRNA for suppressing CP resistance is discussed. The first priority of using siRNA is sensitizing cancer cells to CP-mediated apoptosis via down-regulating survivin, ATG7, Bcl-2, Bcl-xl, and XIAP. The cancer stem cell properties and related molecular pathways including ID1, Oct-4 and nanog are inhibited by siRNA in CP sensitivity. Cell cycle arrest and enhanced accumulation of CP in cancer cells can be obtained using siRNA. In overcoming siRNA challenges such as off-targeting feature and degradation, carriers including nanoparticles and biological carriers have been applied. These carriers are important in enhancing cellular accumulation of siRNA, elevating gene silencing efficacy and reversing CP resistance.

Multiwalled carbon nanotubes co-delivering sorafenib and epidermal growth factor receptor siRNA enhanced tumor-suppressing effect on liver cancer

OBJECTIVE

This study aimed to investigate the effects of multiwalled carbon nanotubes (MWNTs) co-delivering sorafenib (Sor) and epidermal growth factor receptor (EGFR) siRNA (MWNT/Sor/siRNA) on tumor growth in liver cancer (LC).

RESULTS

MWNT/Sor/siRNA was proved to possess increased Sor release, high siRNA stability, and enhanced cellular uptake. In addition, MWNT treatment has few effects on cell proliferation and apoptosis in HepG2 cells; however, MWNT/Sor/siRNA treatment significantly inhibited clone number and induced cell apoptosis, which shows a more favorable antitumor effect than MWNT/Sor and free Sor and free siRNA in HepG2 cells. Moreover MWNT/Sor/siRNA treatment has the most significant antitumor effect in vivo.

CONCLUSIONS

MWNT/Sor/siRNA exhibited a superior antitumor effect in vitro and in vivo.

METHODS

The MWNT/Sor and MWNT/Sor/siRNA were prepared, and then the morphologies of MWNT/Sor/siRNA were analyzed. In vitro Sor release assay, siRNA stability and cellular uptake of MWNT/Sor/siRNA were performed as well. Next, the effects of MWNT, free Sor, free siRNA, MWNT/Sor and MWNT/Sor/siRNA were evaluated by colony-forming assay, and cell apoptosis assay in HepG2 cells. Meanwhile, the level of EGFR and proteins associated with apoptosis was tested. Furthermore, the anti-tumor effects of MWNT/Sor/siRNA on LC xenograft mice were also unraveled.

Cancer-Targeting Nanoparticles for Combinatorial Nucleic Acid Delivery

Nucleic acids are a promising type of therapeutic for the treatment of a wide range of conditions, including cancer, but they also pose many delivery challenges. For efficient and safe delivery to cancer cells, nucleic acids must generally be packaged into a vehicle, such as a nanoparticle, that will allow them to be taken up by the target cells and then released in the appropriate cellular compartment to function. As with other types of therapeutics, delivery vehicles for nucleic acids must also be designed to avoid unwanted side effects; thus, the ability of such carriers to target their cargo to cancer cells is crucial. Classes of nucleic acids, hurdles that must be overcome for effective intracellular delivery, types of nonviral nanomaterials used as delivery vehicles, and the different strategies that can be employed to target nucleic acid delivery specifically to tumor cells are discussed. Additonally, nanoparticle designs that facilitate multiplexed delivery of combinations of nucleic acids are reviewed.

Narciclasine inhibits angiogenic processes by activation of Rho kinase and by downregulation of the VEGF receptor 2

The process of angiogenesis is involved in several pathological conditions, such as tumor growth or age-related macular degeneration. Although the available anti-angiogenic drugs have improved the therapy of these diseases, major drawbacks, such as unwanted side effects and resistances, still exist. Consequently, the search for new anti-angiogenic substances is still ongoing. Narciclasine, a plant alkaloid from different members of the Amaryllidaceae family, has extensively been characterized as anti-tumor compound. Beyond the field of cancer, the compound has recently been shown to possess anti-inflammatory properties. Surprisingly, potential actions of narciclasine on endothelial cells in the context of angiogenesis have been neglected so far. Thus, we aimed to analyze the effects of narciclasine on angiogenic processes in vitro and in vivo and to elucidate the underlying mechanism. Narciclasine (100-300 nM) effectively inhibited the proliferation, undirected and directed migration, network formation and angiogenic sprouting of human primary endothelial cells. Moreover, narciclasine (1 mg/kg/day) strongly reduced the VEGF-triggered angiogenesis in vivo (Matrigel plug assay in mice). Narciclasine mediated its anti-angiogenic effects in part by a RhoA-independent activation of the Rho kinase ROCK. Most importantly, however, the compound reduced the de novo protein synthesis in endothelial cells by approx. 50% without exhibiting considerable cytotoxic effects. As a consequence, narciclasine diminished the presence of proteins with a short half-life, such as the VEGF receptor 2, which is the basis for its anti-angiogenic effects. Taken together, our study highlights narciclasine as an interesting anti-angiogenic compound that is worth to be further evaluated in preclinical studies.

Water-soluble substituted chitosan derivatives as technology platform for inhalation delivery of siRNA

Despite research efforts full potential of siRNA-based therapeutics has not yet been fully realized due to a need for suitable, effective delivery formulations. Here, we examine a potential of a new class of water-soluble chitosans as siRNA platform for pulmonary delivery. The system is based on piperazine-substituted chitosans, a material designed to integrate established, safe application of chitosan for mucosal administration with novel properties: the piperazine-substituted chitosans are freely water-soluble at physiological pH, possess low cytotoxicity (no significant reduction in cell viability up to 0.1 mg/ml), and provide efficient incorporation of siRNA into sub-300 nm colloidal complexes (at relatively low polymer/siRNA ratio of 5:1). In vitro, the complexes achieved silencing of a model gene at a level of 40–80%, when tested in a panel of lung epithelial cells. Considering the formulation ‘developability’, there were no significant changes in the complexes’ size and integrity on aerosolisation by microsprayer (PenCentury™) device. Following intratracheal aerolisation, the complexes deposited throughout the lung, although relatively inhomogeneously, as judged from IVIS imaging of the isolated mouse lung (visualizing DY647-siRNA). In vivo data illustrate absence of adverse effects on repeated administration of complexes and significant tumor reduction in atopical lung cancer model in mice. Altogether, the data illustrates potential of substituted chitosan derivatives to be utilized as a safe system for inhalation delivery of siRNA.

Nanomedicine-based combination anticancer therapy between nucleic acids and small-molecular drugs

Anticancer therapy has always been a vital challenge for the development of nanomedicine. Repeated single therapeutic agent may lead to undesirable and severe side effects, unbearable toxicity and multidrug resistance due to complex nature of tumor. Nanomedicine-based combination anticancer therapy can synergistically improve antitumor outcomes through multiple-target therapy, decreasing the dose of each therapeutic agent and reducing side effects. There are versatile combinational anticancer strategies such as chemotherapeutic combination, nucleic acid-based co-delivery, intrinsic sensitive and extrinsic stimulus combinational patterns. Based on these combination strategies, various nanocarriers and drug delivery systems were engineered to carry out the efficient co-delivery of combined therapeutic agents for combination anticancer therapy. This review focused on illustrating nanomedicine-based combination anticancer therapy between nucleic acids and small-molecular drugs for synergistically improving anticancer efficacy.

EGF-Induced VEGF Exerts a PI3K-Dependent Positive Feedback on ERK and AKT through VEGFR2 in Hematological In Vitro Models

EGFR and VEGFR pathways play major roles in solid tumor growth and progression, however, little is known about these pathways in haematological tumors. This study investigated the crosstalk between EGFR and VEGFR2 signaling in two hematological in vitro models: THP1, a human monocytic leukemia, and Raji, a Burkitt's lymphoma, cell lines. Results showed that both cell lines express EGFR and VEGFR2 and responded to EGF stimulation by activating EGFR, triggering VEGF production and phosphorylating ERK, AKT, and p38 very early, with a peak of expression at 10-20min. Blocking EGFR using Tyrphostin resulted in inhibiting EGFR induced activation of ERK, AKT, and p38. In addition, EGF stimulation caused a significant and immediate increase, within 1min, in pVEGFR2 in both cell lines, which peaked at ~5-10 min after treatment. Selective inhibition of VEGFR2 by DMH4, anti-VEGFR2 antibody or siRNA diminished EGF-induced pAKT and pERK, indicating a positive feedback exerted by EGFR-induced VEGF. Similarly, the specific PI3K inhibitor LY294002, suppressed AKT and ERK phosphorylation showing that VEGF feedback is PI3K-dependent. On the other hand, phosphorylation of p38, initiated by EGFR and independent of VEGF feedback, was diminished using PLC inhibitor U73122. Moreover, measurement of intracellular [Ca2+] and ROS following VEGFR2 inhibition and EGF treatment proved that VEGFR2 is not implicated in EGF-induced Ca2+ release whereas it boosts EGF-induced ROS production. Furthermore, a significant decrease in pAKT, pERK and p-p38 was shown following the addition of the ROS inhibitor NAC. These results contribute to the understanding of the crosstalk between EGFR and VEGFR in haematological malignancies and their possible combined blockade in therapy.

HCRP1 is downregulated in non-small cell lung cancer and regulates proliferation, invasion, and drug resistance

HCRP1 has been reported to have tumor suppressive function. However, its expression pattern and function in human non-small cell lung cancer (NSCLC) remain obscure. This study aims to explore clinical significance of HCRP1 in NSCLC. Immunohistochemical results showed high HCRP1 protein in normal bronchial epithelial tissue and downregulated HCRP1 expression in 47/98 lung cancer specimens. HCRP1 downregulation correlated with clinical stage (p = 0.0203), nodal status (p = 0.0168), and poor patient prognosis (log-rank, p = 0.0076). Univariate analysis showed that TNM stage (p < 0.0001) and HCRP1 (p = 0.0098) were significant prognostic factors; Cox regression model showed that TNM stage serves as an independent prognostic factor (p = 0.0011). We also found that HCRP1 was downregulated in lung cancer cells compared with normal HBE cells. HCRP1 plasmid transfection in H1299 cells inhibited proliferation, cell cycle progression, and invasion. HCRP1 depletion in A549 cells showed the opposite biological effects. In addition, we found that HCRP1 could inhibit MAPK and AKT signaling with downregulation of ERK and AKT phosphorylation, cyclin proteins, Bcl2 and MMP9, while HCRP1 depletion activated ERK and AKT signaling. The level of EGFR phosphorylation was also inhibited by HCRP1. In addition, we found that HCRP1 depletion confers multidrug resistance in H1299 cells. We employed paclitaxel and cisplatin in A549 cells with HCRP1 depletion. HCRP1 depletion decreased the effect of paclitaxel and cisplatin in A549 cells. Treatment with EGFR inhibitor AG1478 and AKT inhibitor LY249004 abolished the effect of HCRP1 depletion on drug resistance. In conclusion, the present study demonstrate that HCRP1 is downregulated in NSCLC and regulates proliferation, invasion, and drug resistance through modulation of EGFR signaling.

Effects for Sequential Treatment of siAkt and Paclitaxel on Gastric Cancer Cell Lines

Real-time screening of cellular response on the drugs could provide valuable insights for the early detection of therapeutic efficiency and the evaluation of disease progression. Cancer cells have the ability to vary widely in response to stress in a manner to adjust the signaling pathway to promote the survival or having a resistance to stimulation. Cell-based label-free technologies using electronic impedance sensor have strategies for constructing the signature profiles of each cells. To achieve exquisite sensitivity to substantially change of live-cell response have an important role that predict the potential of therapeutic effects. In this study, we use an impedance-based real-time cell analysis system to investigate dynamic phenotypes of cells described as a cellular index value. We show that gastric cancer cells generated characteristic kinetic patterns that corresponded to the treatment order of therapeutics. The kinetic feature of the cells offers insightful information that cannot be acquired from a conventional single end-point assay. Furthermore, we employ a 'sequential treatment strategy' to increase cytotoxic effects with minimizing the use of chemotherapeutics. Specifically, treatment of paclitaxel (PTX) after down-regulating Akt gene expression using RNAi reduces the cell proliferation and increases apoptosis. We propose that the sequential treatment may exhibit more effective approach rather than traditional combination therapy. Moreover, the dynamic monitoring of cell-drug interaction enables us to obtain a better understanding of the temporal effects in vitro.

Far upstream element-binding protein 1 is a prognostic biomarker and promotes nasopharyngeal carcinoma progression

Nasopharyngeal carcinoma (NPC) is a malignant epithelial tumor with tremendous invasion and metastasis capacities, and it has a high incidence in southeast Asia and southern China. Previous studies identified that far upstream element-binding protein 1 (FBP1), a transcriptional regulator of c-Myc that is one of the most frequently aberrantly expressed oncogenes in various human cancers, including NPC, is an important biomarker for many cancers. Our study aimed to investigate the expression and function of FBP1 in human NPC. Quantitative real-time RT-PCR (qRT-PCR), western blot and immunohistochemical staining (IHC) were performed in NPC cells and biopsies. Furthermore, the effect of FBP1 knockdown on cell proliferation, colony formation, side population tests and tumorigenesis in nude mice were measured by MTT, clonogenicity analysis, flow cytometry and a xenograft model, respectively. The results showed that the mRNA and protein levels of FBP1, which are positively correlated with c-Myc expression, were substantially higher in NPC than that in nasopharyngeal epithelial cells. IHC revealed that the patients with high FBP1 expression had a significantly poorer prognosis compared with the patients with low expression (P=0.020). In univariate analysis, high FBP1 and c-Myc expression predicted poorer overall survival (OS) and poorer progression-free survival. Multivariate analysis indicated that high FBP1 and c-Myc expression were independent prognostic markers. Knockdown of FBP1 reduced cell proliferation, clonogenicity and the ratio of side populations, as well as tumorigenesis in nude mice. These data indicate that FBP1 expression, which is closely correlated with c-Myc expression, is an independent prognostic factor and promotes NPC progression. Our results suggest that FBP1 can not only serve as a useful prognostic biomarker for NPC but also as a potential therapeutic target for NPC patients.

Morpholino-Mediated Isoform Modulation of Vascular Endothelial Growth Factor Receptor-2 (VEGFR2) Reduces Colon Cancer Xenograft Growth

Angiogenesis plays a key role in tumor growth. Vascular endothelial growth factor (VEGF) is a pro-angiogenic that is involved in tumor angiogenesis. When VEGF binds to membrane-bound vascular endothelial growth factor receptor 2 (mVEGFR2), it promotes angiogenesis. Through alternative polyadenylation, VEGFR2 is also expressed in a soluble form (sVEGFR2). sVEGFR2 sequesters VEGF and is therefore anti-angiogenic. The aim of this study was to show that treatment with a previously developed and reported antisense morpholino oligomer that shifts expression from mVEGFR2 to sVEGFR2 would lead to reduced tumor vascularization and growth in a murine colon cancer xenograft model. Xenografts were generated by implanting human HCT-116 colon cancer cells into the flanks of NMRI nu/nu mice. Treatment with the therapeutic morpholino reduced both tumor growth and tumor vascularization. Because the HCT-116 cells used for the experiments did not express VEGFR2 and because the treatment morpholino targeted mouse rather than human VEGFR2, it is likely that treatment morpholino was acting on the mouse endothelial cells rather than directly on the tumor cells.

Tumor-targeted in vivo gene silencing via systemic delivery of cRGD-conjugated siRNA

RNAi technology is taking strong position among the key therapeutic modalities, with dozens of siRNA-based programs entering and successfully progressing through clinical stages of drug development. To further explore potentials of RNAi technology as therapeutics, we engineered and tested VEGFR2 siRNA molecules specifically targeted to tumors through covalently conjugated cyclo(Arg-Gly-Asp-d-Phe-Lys[PEG-MAL]) (cRGD) peptide, known to bind αvβ3 integrin receptors. cRGD-siRNAs were demonstrated to specifically enter and silence targeted genes in cultured αvβ3 positive human cells (HUVEC). Microinjection of zebrafish blastocysts with VEGFR2 cRGD-siRNA resulted in specific inhibition of blood vessel growth. In tumor-bearing mice, intravenously injected cRGD-siRNA molecules generated no innate immune response and bio-distributed to tumor tissues. Continuous systemic delivery of two different VEGFR2 cRGD-siRNAs resulted in down-regulation of corresponding mRNA (55 and 45%) and protein (65 and 45%) in tumors, as well as in overall reduction of tumor volume (90 and 70%). These findings demonstrate strong potential of cRGD-siRNA molecules as anti-tumor therapy.

Nanocarrier mediated delivery of siRNA/miRNA in combination with chemotherapeutic agents for cancer therapy: current progress and advances

Chemotherapeutic agents have certain limitations when it comes to treating cancer, the most important being severe side effects along with multidrug resistance developed against them. Tumor cells exhibit drug resistance due to activation of various cellular level processes viz. activation of drug efflux pumps, anti-apoptotic defense mechanisms, etc. Currently, RNA interference (RNAi) based therapeutic approaches are under vibrant scrutinization to seek cancer cure. Especially small interfering RNA (siRNA) and micro RNA (miRNA), are able to knock down the carcinogenic genes by targeting the mRNA expression, which underlies the uniqueness of this therapeutic approach. Recent research focus in the regime of cancer therapy involves the engagement of targeted delivery of siRNA/miRNA in combinations with other therapeutic agents (such as gene, DNA or chemotherapeutic drug) for targeting permeability glycoprotein (P-gp), multidrug resistant protein 1 (MRP-1), B-cell lymphoma (BCL-2) and other targets that are mainly responsible for resistance in cancer therapy. RNAi-chemotherapeutic drug combinations have also been found to be effective against different molecular targets as well and can increase the sensitization of cancer cells to therapy several folds. However, due to stability issues associated with siRNA/miRNA suitable protective carrier is needed and nanotechnology based approaches have been widely explored to overcome these drawbacks. Furthermore, it has been univocally advocated that the co-delivery of siRNA/miRNA with other chemodrugs significantly enhances their capability to overcome cancer resistance compared to naked counterparts. The objective of this article is to review recent nanocarrier based approaches adopted for the delivery of siRNA/miRNA combinations with other anticancer agents (siRNA/miRNA/pDNA/chemodrugs) to treat cancer.

Self-assembled nanoparticles based on the c(RGDfk) peptide for the delivery of siRNA targeting the VEGFR2 gene for tumor therapy

The clinical application of small interfering RNA (siRNA) has been restricted by their poor intracellular uptake, low serum stability, and inability to target specific cells. During the last several decades, a great deal of effort has been devoted to exploring materials for siRNA delivery. In this study, biodegradable, tumor-targeted, self-assembled peptide nanoparticles consisting of cyclo(Arg–Gly–Asp–d–Phe–Lys)-8–amino–3,6–dioxaoctanoic acid–β–maleimidopropionic acid (hereafter referred to as RPM) were found to be an effective siRNA carrier both in vitro and in vivo. The nanoparticles were characterized based on transmission electron microscopy, circular dichroism spectra, and dynamic light scattering. In vitro analyses showed that the RPM/VEGFR2-siRNA exhibited negligible cytotoxicity and induced effective gene silencing. Delivery of the RPM/VEGFR2 (zebrafish)-siRNA into zebrafish embryos resulted in inhibition of neovascularization. Administration of RPM/VEGFR2 (mouse)-siRNA to tumor-bearing nude mice led to a significant inhibition of tumor growth, a marked reduction of vessels, and a down-regulation of VEGFR2 (messenger RNA and protein) in tumor tissue. Furthermore, the levels of IFN-α, IFN-γ, IL-12, and IL-6 in mouse serum, assayed via enzyme-linked immunosorbent assay, did not indicate any immunogenicity of the RPM/VEGFR2 (mouse)-siRNA in vivo. In conclusion, RPM may provide a safe and effective delivery vector for the clinical application of siRNAs in tumor therapy.

Knockdown of VEGFR2 inhibits proliferation and induces apoptosis in hemangioma-derived endothelial cells

Angiogenesis is a process of development and growth of new capillary blood vessels from pre-existing vessels. Angiogenic growth factors play important roles in the development and maintenance of some malignancies, of which vascular endothelial growth factor (VEGF)/VEGFR2 interactions are involved in proliferation, migration, and survival of many cancer cells. The aim of this study was to investigate the function of VEGFR2 in human hemangiomas (HAs). Using immunohistochemistry assay, we examined the expression levels of VEGF, VEGFR2, Ki-67, glucose transporter-1 (Glut-1), phosphorylated protein kinase B (p-AKT) and p-ERK in different phases of human HAs. Positive expression of VEGF, VEGFR2, Ki-67, Glut-1, p-AKT and p-ERK was significantly increased in proliferating phase HAs, while decreased in involuting phase HAs (P=0.001; P=0.003). In contrast, cell apoptotic indexes were decreased in proliferating phase HAs, but increased in involuting phase HAs (P&lt;0.01). Furthermore, we used small hairpin RNA (shRNA)-mediated VEGFR2 knockdown in primary HA-derived endothelial cells (HemECs) to understand  the  role  of  VEGF/VEGFR2 signaling. Knockdown of VEGFR2 by Lv-shVEGFR2 inhibited cell viability and induced apoptosis in primary HemECs companied with decreased expression of p-AKT, p-ERK, p-p38MAPK and Ki-67 and increased expression of caspase-3 (CAS-3). Overexpression of VEGFR2 promoted cell viability and blocked apoptosis in Lv-VEGFR2-transfected HemECs. Taken together, our findings demonstrate that, increased expression of VEGFR2 is involved in the development of primary HemECs possibly through regulation of the AKT and ERK pathways, suggesting that VEGFR2 may be a potential therapeutic target for HAs. 

A murine-human chimeric IgG antibody against vascular endothelial growth factor receptor 2 inhibits angiogenesis in vitro

Vascular endothelial growth factor receptor 2 (VEGFR2) has been reported to play an important role in angiogenesis and tumorigenesis. A murine anti-VEGFR2 mAb (A8H1) has been established in a previous study. To reduce the incompatibility of the murine mAb for human use, the chimeric anti-VEGFR2-IgG was developed by genetic recombination of the variable regions of the A8H1 antibody and the constant regions of human IgG, and was expressed in Sp2/0 cells transfected with the two recombinant vectors containing the heavy chain and the light chain regions. After screening, clone 2F12 was selected and was found to stably secrete the murine-human chimeric anti-VEGFR2-IgG (coded 2F12). This chimeric IgG maintained the specificity and the affinity of the parental murine antibody against VEGFR2, and effectively identified VEGFR2 expressed on the surface of HUVECs and BEL-7402 cells. Furthermore, the 2F12 antibody demonstrated inhibition of angiogenesis in vitro, such as proliferation, migration, invasion and tube formation of HUVECs. This murine-human chimeric IgG may be considered for further development as an anti-angiogenesis and anti-tumor agent.

Sticky siRNAs targeting survivin and cyclin B1 exert an antitumoral effect on melanoma subcutaneous xenografts and lung metastases

Background

Melanoma represents one of the most aggressive and therapeutically challenging malignancies as it often gives rise to metastases and develops resistance to classical chemotherapeutic agents. Although diverse therapies have been generated, no major improvement of the patient prognosis has been noticed. One promising alternative to the conventional therapeutic approaches currently available is the inactivation of proteins essential for survival and/or progression of melanomas by means of RNA interference. Survivin and cyclin B1, both involved in cell survival and proliferation and frequently deregulated in human cancers, are good candidate target genes for siRNA mediated therapeutics.

Methods

We used our newly developed sticky siRNA-based technology delivered with linear polyethyleneimine (PEI) to inhibit the expression of survivin and cyclin B1 both in vitro and in vivo, and addressed the effect of this inhibition on B16-F10 murine melanoma tumor development.

Results

We confirm that survivin and cyclin B1 downregulation through a RNA interference mechanism induces a blockage of the cell cycle as well as impaired proliferation of B16-F10 cells in vitro. Most importantly, PEI-mediated systemic delivery of sticky siRNAs against survivin and cyclin B1 efficiently blocks growth of established subcutaneaous B16-F10 tumors as well as formation and dissemination of melanoma lung metastases. In addition, we highlight that inhibition of survivin expression increases the effect of doxorubicin on lung B16-F10 metastasis growth inhibition.

Conclusion

PEI-mediated delivery of sticky siRNAs targeting genes involved in tumor progression such as survivin and cyclin B1, either alone or in combination with chemotherapeutic drugs, represents a promising strategy for melanoma treatment.