Sustained and cancer cell targeted cytosolic delivery of Onconase results in potent antitumor effects

Role of the Ribonuclease ONCONASE in miRNA Biogenesis and tRNA Processing: Focus on Cancer and Viral Infections

The majority of transcribed RNAs do not codify for proteins, nevertheless they display crucial regulatory functions by affecting the cellular protein expression profile. MicroRNAs (miRNAs) and transfer RNA-derived small RNAs (tsRNAs) are effectors of interfering mechanisms, so that their biogenesis is a tightly regulated process. Onconase (ONC) is an amphibian ribonuclease known for cytotoxicity against tumors and antiviral activity. Additionally, ONC administration in patients resulted in clinical effectiveness and in a well-tolerated feature, at least for lung carcinoma and malignant mesothelioma. Moreover, the ONC therapeutic effects are actually potentiated by cotreatment with many conventional antitumor drugs. This review not only aims to describe the ONC activity occurring either in different tumors or in viral infections but also to analyze the molecular mechanisms underlying ONC pleiotropic and cellular-specific effects. In cancer, data suggest that ONC affects malignant phenotypes by generating tRNA fragments and miRNAs able to downregulate oncogenes expression and upregulate tumor-suppressor proteins. In cells infected by viruses, ONC hampers viral spread by digesting the primer tRNAs necessary for viral DNA replication. In this scenario, new therapeutic tools might be developed by exploiting the action of ONC-elicited RNA derivatives.

Biological Activities of Secretory RNases: Focus on Their Oligomerization to Design Antitumor Drugs

Ribonucleases (RNases) are a large number of enzymes gathered into different bacterial or eukaryotic superfamilies. Bovine pancreatic RNase A, bovine seminal BS-RNase, human pancreatic RNase 1, angiogenin (RNase 5), and amphibian onconase belong to the pancreatic type superfamily, while binase and barnase are in the bacterial RNase N1/T1 family. In physiological conditions, most RNases secreted in the extracellular space counteract the undesired effects of extracellular RNAs and become protective against infections. Instead, if they enter the cell, RNases can digest intracellular RNAs, becoming cytotoxic and having advantageous effects against malignant cells. Their biological activities have been investigated either in vitro, toward a number of different cancer cell lines, or in some cases in vivo to test their potential therapeutic use. However, immunogenicity or other undesired effects have sometimes been associated with their action. Nevertheless, the use of RNases in therapy remains an appealing strategy against some still incurable tumors, such as mesothelioma, melanoma, or pancreatic cancer. The RNase inhibitor (RI) present inside almost all cells is the most efficacious sentry to counteract the ribonucleolytic action against intracellular RNAs because it forms a tight, irreversible and enzymatically inactive complex with many monomeric RNases. Therefore, dimerization or multimerization could represent a useful strategy for RNases to exert a remarkable cytotoxic activity by evading the interaction with RI by steric hindrance. Indeed, the majority of the mentioned RNases can hetero-dimerize with antibody derivatives, or even homo-dimerize or multimerize, spontaneously or artificially. This can occur through weak interactions or upon introducing covalent bonds. Immuno-RNases, in particular, are fusion proteins representing promising drugs by combining high target specificity with easy delivery in tumors. The results concerning the biological features of many RNases reported in the literature are described and discussed in this review. Furthermore, the activities displayed by some RNases forming oligomeric complexes, the mechanisms driving toward these supramolecular structures, and the biological rebounds connected are analyzed. These aspects are offered with the perspective to suggest possible efficacious therapeutic applications for RNases oligomeric derivatives that could contemporarily lack, or strongly reduce, immunogenicity and other undesired side-effects.

A novel stearic acid-modified hirudin peptidomimetic with improved pharmacokinetic properties and anticoagulant activity

A novel hirudin isoform 3 mimetic peptide, named peptide S2, has been prepared by introduction of a stearic acid modification. Peptide S2 exhibited superior inhibitory activity to hirulog-1 (Bivariludin) and showed significantly higher anticoagulant potency in vivo. Peptide S2 elevated the thrombin time, prothrombin time and activated partial thromboplastin time of rat and human plasma more efficiently than hirulog-1 and the unmodified form of peptide S2 (peptide 1). Furthermore, peptide S2 inhibited arterial thrombosis and inferior vena cava in rat model 8 h after administration, and was 10-fold more potent than hirulog-1 300 min after administration of 0.1 μmol/kg peptide. The enhanced antithrombotic activity could be attributed to its long half-life (T_1/2 = 212.2 ± 58.4 min), which was 13.1 and 14.7-fold longer than those of hirulog-1 (T_1/2 = 15.1 ± 1.3 min) and peptide 1 (T_1/2 = 13.5 ± 2.6 min), respectively. Further enzymatic degradation and binding assay with human serum albumin (HSA) demonstrated that the longer duration time should be originated from the slowing of trypsin or thrombin–mediated degradation, as well as its binding to HSA. The improved pharmacokinetic properties observed for peptide S2 has made it a promising therapeutic agent for the treatment of thrombi-related diseases.

Rana catesbeiana ribonuclease induces cell apoptosis via the caspase-9/-3 signaling pathway in human glioblastoma DBTRG, GBM8901 and GBM8401 cell lines

Human glioblastoma multiforme is one of the most aggressive malignant brain tumor types, and the mean survival time of patients with a brain tumor is <2 years when traditional therapies are administered. Thus, numerous studies have focused on the development of novel treatments for brain tumors. Frog ribonucleases, such as Onconase and Rana catesbeiana ribonuclease (RC-RNase), exert antitumor effects on various tumor cells, including cervical cancer, breast cancer, hepatoma, leukemia, pancreatic cancer and prostate cancer cells. In addition, frog Onconase has been applied as a treatment in clinical trials. However, the antitumor effects of frog ribonucleases on brain tumors are unclear. Previous studies have indicated that RC-RNase demonstrates a decreased cytotoxic effect in normal cells compared with Onconase. Therefore, the present study investigated the ability of RC-RNase to exert antitumor activities on human glioblastoma. It was found that RC-RNase inhibits the growth of the human glioblastoma DBTRG, GBM8901 and GBM8401 cells. In addition, the present study revealed that RC-RNase induces caspase-9/-3 activity and triggers the apoptotic cell death pathway in human glioblastoma cells. Notably, it was also demonstrated that RC-RNase effectively inhibits the growth of human glioblastoma tumors in a nude mouse model. Overall, the present study indicates that RC-RNase may be a potential agent for the treatment of human glioblastoma.

Designing hybrid onconase nanocarriers for mesothelioma therapy: a Taguchi orthogonal array and multivariate component driven analysis

Onconase (ONC) is a member of a ribonuclease superfamily that has cytostatic activity against malignant mesothelioma (MM). The objective of this investigation was to develop bovine serum albumin (BSA)-chitosan based hybrid nanoformulations for the efficient delivery of ONC to MM while minimizing the exposure to normal tissues. Taguchi orthogonal array L9 type design was used to formulate ONC loaded BSA nanocarriers (ONC-ANC) with a mean particle size of 15.78 ± 0.24 nm (ζ = -21.89 ± 0.11 mV). The ONC-ANC surface was hybridized using varying chitosan concentrations ranging between 0.100 and 0.175% w/v to form various ONC loaded hybrid nanocarriers (ONC-HNC). The obtained data set was analyzed by principal component analysis (PCA) and principal component regressions (PCR) to decode the effects of investigated design variables. PCA showed positive correlations between investigated design variables like BSA, ethanol dilution, and total ethanol with particle size and entrapment efficiency (EE) of formulated nanocarriers. PCR showed that the particle size depends on BSA, ethanol dilution, and total ethanol content, while EE was only influenced by BSA content. Further analysis of chitosan and TPP effects used for coating of ONC-ANC by PCR confirmed their positive impacts on the particle size, zeta potential, and prolongation of ONC release compared to uncoated ONC-ANC. PCR analysis of preliminary stability studies showed increase in the particle size and zeta potential at lower pH. However, particle size, zeta potential, and EE of developed HNC were below 63 nm, 31 mV, and 96%, respectively, indicating their stability under subjected buffer conditions. Out of the developed formulations, HNC showed enhanced inhibition of cell viability with lower IC50 against human MM-REN cells compared to ONC and ONC-ANC. This might be attributed to the better cell uptake of HNC, which was confirmed in the cell uptake fluorescence studies. These studies indicated that a developed nanotherapeutic approach might aid in reducing the therapeutic dose of ONC, minimizing adverse effects by limiting the exposure of ONC to normal tissues, and help in the development of new therapeutic forms and routes of administration.

Amine-modified hyaluronic acid-functionalized porous silicon nanoparticles for targeting breast cancer tumors

Active targeting of nanoparticles to receptor-overexpressing cancer cells has great potential for enhancing the cellular uptake of nanoparticles and for reducing fast clearance of the nanoparticles from the body. Herein, we present a preparation method of a porous silicon (PSi)-based nanodelivery system for breast cancer targeting, by covalently conjugating a synthesized amide-modified hyaluronic acid (HA(+)) derived polymer on the surface of undecylenic acid-modified thermally hydrocarbonized PSi (UnTHCPSi) nanoparticles. The resulting UnTHCPSi-HA(+) nanoparticles showed relatively small size, reduced polydispersibility, high biocompatibility, improved colloidal and human plasma stability, as well as enhanced cellular interactions and internalization. Moreover, we demonstrated that the enhanced cellular association of UnTHCPSi-HA(+) relies on the capability of the conjugated HA(+) to bind and consequently target CD44 receptors expressed on the surface of breast cancer cells, thus making the HA(+)-functionalized UnTHCPSi nanoparticles a suitable and promising nanoplatform for the targeting of CD44-overexpressing breast tumors and for drug delivery.

Leczyme: a new candidate drug for cancer therapy

Sialic acid-binding lectin (SBL), isolated from oocytes of Rana catesbeiana, is leczyme and has both lectin and ribonuclease (RNase) activities. A remarkable antitumor effect of SBL has also been reported. SBL agglutinates various kinds of tumor cells but not normal cells. SBL agglutination activity is not affected by mono- or oligosaccharides. However, SBL-induced agglutination and antitumor effects are inhibited by sialomucin but not asialomucin. In addition, SBL has very little effect on sialidase-treated cells. SBL causes cancer-selective induction of apoptosis by multiple signaling pathways, which target RNA. Synergistic antitumor effects with other molecules, such as tumor necrosis factor-related apoptosis ligand (TRAIL) and interferon-γ (IFN-γ), have been reported. Thus, SBL may be a novel candidate molecule for anticancer drug development. Sialoglycoconjugates on the tumor cell surface may be associated with lectin activity and antitumor effects of SBL. We review the properties of SBL, particularly its lectin, RNase, and antitumor activities, and comprehensively examine the potential application of SBL for clinical purposes.

Recombinant expression, different downstream processing of the disulfide-rich anti-tumor peptide Ranpirnase and its effect on the growth of human glioma cell line SHG-44

Ranpirnase (Onconase) is a frogspawn-derived disulfide-rich peptide with ribonuclease activity that may be used for tumor treatment. In the present study, we established an efficient approach for preparing mature ranpirnase which may be used for research and therapeutic purposes. The designed ranpirnase precursors carried a 6xHis-tag and were recombinantly expressed in Escherichia coli. After S-sulfonation, the precursors were purified by immobilized metal-ion affinity chromatography. Following removal of the tag by aminopeptidase cleavage, cyclization and in vitro oxidative refolding, the mature ranpirnase was obtained with considerable yield, and the yield of mature ranpirnase was ~50-60 mg per liter cultures. In addition, ranpirnase inhibited the growth of human glioma cells SHG-44 in a dose-dependent manner. Thus the present study has provided an efficient approach for the preparation of active ranpirnase and its analogues for future studies.

Epithelial cell adhesion molecule-targeted drug delivery for cancer therapy

INTRODUCTION

The epithelial cell adhesion molecule (EpCAM) is abundantly expressed in epithelial tumors, on cancer stem cells and circulating tumor cells. Together with its role in oncogenic signaling, this has sparked interest in its potential for tumor targeting with antibodies and drug conjugates for safe and effective cancer therapy. Recent advances in protein engineering, linker design and drug formulations have provided a multitude of EpCAM-targeting anticancer agents, several of them with good perspectives for clinical development.

AREAS COVERED

This article reviews the biological, therapeutic and technical aspects of EpCAM-targeted drug delivery for cancer therapy. The authors discuss seminal findings, which distinguish EpCAM as a target with oncogenic function and abundant expression in epithelial tumors. Moreover, recent trends in engineering improved anti-EpCAM antibodies, binding proteins that are not derived from immunoglobulins and drug conjugates derived from them are highlighted and their therapeutic potential based on reported preclinical and clinical data, originality of design and perspectives are critically assessed.

EXPERT OPINION

EpCAM has shown promise for safe and efficient targeting of solid tumors using antibodies, alternative binding molecules and novel drug conjugates. Among the myriad of EpCAM-targeting drug delivery systems investigated so far, several could demonstrate therapeutic benefit, other formulations engineered to become tailor-made missiles are on the brink.