A Novel Venom-Derived Peptide for Brachytherapy of Glioblastoma: Preclinical Studies in Mice

Venom-derived peptides for breaking through the glass ceiling of drug development

Venoms are complex mixtures produced by animals and consist of hundreds of components including small molecules, peptides, and enzymes selected for effectiveness and efficacy over millions of years of evolution. With the development of venomics, which combines genomics, transcriptomics, and proteomics to study animal venoms and their effects deeply, researchers have identified molecules that selectively and effectively act against membrane targets, such as ion channels and G protein-coupled receptors. Due to their remarkable physico-chemical properties, these molecules represent a credible source of new lead compounds. Today, not less than 11 approved venom-derived drugs are on the market. In this review, we aimed to highlight the advances in the use of venom peptides in the treatment of diseases such as neurological disorders, cardiovascular diseases, or cancer. We report on the origin and activity of the peptides already approved and provide a comprehensive overview of those still in development.

Snake venom bioprospecting as an approach to finding potential anti-glioblastoma molecules

Glioblastoma (GB) is the most common type of malignant tumor of the central nervous system, responsible for significant morbidity and with a 5-year overall relative survival of only 6.8%. Without advances in treatment in the last twenty years, the standard of care continues to be maximum safe resection, Temozolomide (TMZ), and radiotherapy. Many new trials are ongoing, and despite showing increased progression-free survival, these trials did not improve overall survival. They did not consider the adverse effects of these therapies. Therefore, an increasing number of bioprospecting studies have used snake venom molecules to search for new strategies to attack GB selectively without producing side effects. The present review aims to describe GB characteristics and current and new approaches for treatment considering their side effects. Besides, we focused on the antitumoral activity of snake venom proteins from the Viperidae family against GB, exploring the potential for drug design based on in vitro and in vivo studies. This review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. In January 2024, a systematic search was performed in the PubMed, EMBASE, and Web of Science databases from January 2000 to December 2023. Search terms were selected based on the population/exposure/outcome (PEO) framework and combined using Boolean operators ("AND", "OR"). The search strategy used these terms: glioblastoma, glioma, high-grade glioma, WHO IV glioma, brain cancer, snake venom, Viperidae, and bioprospection. We identified 10 in vivo and in vitro studies with whole and isolated proteins from Viperidae venom that could have antitumor activity against glioblastoma. Studies in bioprospecting exploring the advantage of snake venom proteins against GB deserve to be investigated due to their high specificity, small size, inherent bioactivity, and few side effects to cross the blood-brain barrier (BBB) to reach the tumor microenvironment.

Effect of Dimeric Disintegrins Isolated from Vipera lebetina obtusa Venom on Glioblastoma Cellular Responses

Integrins play a fundamental role in the migration and invasiveness of glioblastoma (GBM) cells, making them suitable targets for innovative cancer therapy. The aim of this study was to evaluate the effect of the RGD homodimeric disintegrin VLO4, isolated from Vipera lebetina obtusa venom, on the adhesion, spreading, migration, and survival of LBC3, LN18, and LN229 cell lines. This disintegrin, as a potent antagonist for α5β1 integrin, showed pro-adhesive properties for these cell lines, the highest for LN229 and the lowest for LBC3. Glioblastoma cells displayed significant differences in the spreading on the immobilized VLO4 and the natural α5β1 integrin ligand, fibronectin. Solubilized VLO4 showed different cytotoxicity and pro-apoptotic properties among tested cell lines, with the highest against LN18 and none against LN229. Moreover, VLO4 revealed an inhibitory effect on the migration of LBC3 and LN18 cell lines, in contrast to LN229 cells, which were not sensitive to this disintegrin. However, LN229 migration was impaired by VLO5, a disintegrin antagonistic to integrin α9β1, used in combination with VLO4. A possible mechanism of action of VLO4 may be related to the downregulation of α5β1 integrin subunit expression, as revealed by Western blot. VLO4 also inhibited cell proliferation and induced caspase-dependent apoptosis in LBC3 and LN18 cell lines. These results indicate that targeting α5β1 integrin by related VLO4 compounds may be useful in the development of integrin-targeted therapy for glioblastoma.

Evaluation of Temozolomide and Fingolimod Treatments in Glioblastoma Preclinical Models

Glioblastomas are malignant brain tumors which remain lethal due to their aggressive and invasive nature. The standard treatment combines surgical resection, radiotherapy, and chemotherapy using Temozolomide, albeit with a minor impact on patient prognosis (15 months median survival). New therapies evaluated in preclinical translational models are therefore still required to improve patient survival and quality of life. In this preclinical study, we evaluated the effect of Temozolomide in different models of glioblastoma. We also aimed to investigate the efficacy of Fingolimod, an immunomodulatory drug for multiple sclerosis also described as an inhibitor of the sphingosine-1-phosphate (S1P)/S1P receptor axis. The effects of Fingolimod and Temozolomide were analyzed with in vitro 2D and 3D cellular assay and in vivo models using mouse and human glioblastoma cells implanted in immunocompetent or immunodeficient mice, respectively. We demonstrated both in in vitro and in vivo models that Temozolomide has a varied effect depending on the tumor type (i.e., U87MG, U118MG, U138MG, and GL261), demonstrating sensitivity, acquired resistance, and purely resistant tumor phenotypes, as observed in patients. Conversely, Fingolimod only reduced in vitro 2D tumor cell growth and increased cytotoxicity. Indeed, Fingolimod had little or no effect on 3D spheroid cytotoxicity and was devoid of effect on in vivo tumor progression in Temozolomide-sensitive models. These results suggest that the efficacy of Fingolimod is dependent on the glioblastoma tumor microenvironment. Globally, our data suggest that the response to Temozolomide varies depending on the cancer model, consistent with its clinical activity, whereas the potential activity of Fingolimod may merit further evaluation.

Bioactive peptides from venoms against glioma progression

Venoms are complex mixtures of different molecules and ions. Among them, bioactive peptides have been found to affect cancer hallmarks, such as cell proliferation, cell invasion, cell migration, and can also modulate the immune response of normal and cancer-bearing organisms. In this article, we review the mechanisms of action on these cancer cell features, focusing on bioactive peptides being developed as potential therapeutics for one of the most aggressive and deadly brain tumors, glioblastoma (GB). Novel therapeutic approaches applying bioactive peptides may contribute to multiple targeting of GB and particularly of GB stem cells. Bioactive peptides selectively target cancer cells without harming normal cells. Various molecular targets related to the effects of bioactive peptides on GB have been proposed, including ion channels, integrins, membrane phospholipids and even immunomodulatory treatment of GB. In addition to therapy, some bioactive peptides, such as disintegrins, can also be used for diagnostics or are used as labels for cytotoxic drugs to specifically target cancer cells. Given the limitations described in the last section, successful application in cancer therapy is rather low, as only 3.4% of such peptides have been included in clinical trials and have passed successfully phases I to III. Combined approaches of added bioactive peptides to standard cancer therapies need to be explored using advanced GB in vitro models such as organoids. On the other hand, new methods are also being developed to improve translation from research to practice and provide new hope for GB patients and their families.

Bioactive Peptides and Proteins from Centipede Venoms

Venoms are a complex cocktail of biologically active molecules, including peptides, proteins, polyamide, and enzymes widely produced by venomous organisms. Through long-term evolution, venomous animals have evolved highly specific and diversified peptides and proteins targeting key physiological elements, including the nervous, blood, and muscular systems. Centipedes are typical venomous arthropods that rely on their toxins primarily for predation and defense. Although centipede bites are frequently reported, the composition and effect of centipede venoms are far from known. With the development of molecular biology and structural biology, the research on centipede venoms, especially peptides and proteins, has been deepened. Therefore, we summarize partial progress on the exploration of the bioactive peptides and proteins in centipede venoms and their potential value in pharmacological research and new drug development.

Identification of harmine and β-carboline analogs from a high-throughput screen of an approved drug collection; profiling as differential inhibitors of DYRK1A and monoamine oxidase A and for in vitro and in vivo anti-cancer studies

DYRK1A (dual-specificity tyrosine phosphorylation-regulated kinase 1a) is highly expressed in glioma, an aggressive brain tumor, and has been proposed as a therapeutic target for cancer. In the current study, we have used an optimized and validated time-resolved fluorescence energy transfer (TR-FRET)-based DYRK1A assay for high-throughput screening (HTS) in 384-well format. A small-scale screen of the FDA-approved Prestwick drug collection identified the β-carboline, harmine, and four related analogs as DYRK1A inhibitors. Hits were confirmed by dose response and in an orthogonal DYRK1A assay. Harmine's potential therapeutic use has been hampered by its off-target activity for monoamine oxidase A (MAO-A) which impacts multiple nervous system targets. Selectivity profiling of harmine and a broader collection of analogs allowed us to map some divergent SAR (structure-activity relationships) for the DYRK1A and MAO-A activities. The panel of harmine analogs had varying activities in vitro in glioblastoma (GBM) cell lines when tested for anti-proliferative effects using a high content imaging assay. In particular, of the identified analogs, harmol was found to have the best selectivity for DYRK1A over MAO-A and, when tested in a glioma tumor xenograft model, harmol demonstrated a better therapeutic window compared to harmine.

Prognostic Biomarker ZNF311 and Its Correlation With Tumor Progression and Immune Infiltrates in Glioma

BACKGROUND

Gliomas, particularly high-grade gliomas, are the most common primary brain tumors. From the Chinese Glioma Genome Atlas (CGGA) database, the relationships between the altered molecular pathways and gliomas could be easily observed. A close connection in the occurrence of the pathogenesis exists between the microenvironment, the glioma, and the associated genes.

METHODS

Validation of the role of ZNF311 oncogene was confirmed by data from the CGGA dataset on glioblastoma and low-grade glioma. Furthermore, we used CIBERSORT to analyze the correlation between ZNF311 and cancer immune infiltrates.

RESULTS

According to our analysis, ZNF311 was expressed higher in patients with grade-depended glioma with poor prognosis. In addition, we obtained valuable prognostic results between isocitrate dehydrogenase 1 (IDH1) and ZNF311 through the analysis of integrated correlations. Similarly, we simultaneously revealed the prognostic results between 1p/19q and ZNF311. In addition, we found that ZNF311 is correlated with a large number of tumor-infiltrating immune cells.

CONCLUSIONS

Based on the study findings, we conclude that ZNF311 is potentially a novel biomarker for assessing prognosis and immune infiltration in glioblastoma and diffuse glioma cases.

Cytotoxic effect of Montivipera bornmuelleri's venom on cancer cell lines: in vitro and in vivo studies

Background

Montivipera bornmuelleri’s venom has shown immunomodulation of cytokines release in mice and selective cytotoxicity on cancer cells in a dose-dependent manner, highlighting an anticancer potential. Here, we extend these findings by elucidating the sensitivity of murine B16 skin melanoma and 3-MCA-induced murine fibrosarcoma cell lines to M. bornmuelleri’s venom and its effect on tumor growth in vivo.

Methods

The toxicity of the venom on B16 and MCA cells was assessed using flow cytometry and xCELLigence assays. For in vivo testing, tumor growth was followed in mice after intratumoral venom injection.

Results

The venom toxicity showed a dose-dependent cell death on both B16 and MCA cells. Interestingly, overexpression of ovalbumin increased the sensitivity of the cells to the venom. However, the venom was not able to eradicate induced-tumor growth when injected at 100 µg/kg. Our study demonstrates a cytotoxic effect of M. bornmuelleri’s venom in vitro which, however, does not translate to an anticancer action in vivo.

Structural Insight into Integrin Recognition and Anticancer Activity of Echistatin

Echistatin (Ech) is a short disintegrin with a long ⁴²NPHKGPAT C-terminal tail. We determined the 3-D structure of Ech by X-ray crystallography. Superimposition of the structures of chains A and B showed conformational differences in their RGD loops and C-termini. The chain A structure is consistent with our NMR analysis that the GPAT residues of the C-terminus cannot be observed due to high flexibility. The hydrogen bond patterns of the RGD loop and between the RGD loop and C-terminus in Ech were the same as those of the corresponding residues in medium disintegrins. The mutant with C-terminal HKGPAT truncation caused 6.4-, 7.0-, 11.7-, and 18.6-fold decreases in inhibiting integrins αvβ3, αIIbβ3, αvβ5, and α5β1. Mutagenesis of the C-terminus showed that the H44A mutant caused 2.5- and 4.4-fold increases in inhibiting αIIbβ3 and α5β1, and the K45A mutant caused a 2.6-fold decrease in inhibiting αIIbβ3. We found that Ech inhibited VEGF-induced HUVEC proliferation with an IC₅₀ value of 103.2 nM and inhibited the migration of A375, U373MG, and Panc-1 tumor cells with IC₅₀ values of 1.5, 5.7, and 154.5 nM. These findings suggest that Ech is a potential anticancer agent, and its C-terminal region can be optimized to improve its anticancer activity.

Preclinical studies of a novel snake venom-derived recombinant disintegrin with antitumor activity: A review

Snake venoms consist of a complex mixture of many bioactive molecules. Among them are disintegrins, which are peptides without enzymatic activity, but with high binding affinity for integrins, transmembrane receptors that function to connect cells with components of the extracellular matrix. Integrin-mediated cell attachment is critical for cell migration and dissemination, as well as for signal transduction pathways involved in cell growth. During tumor development, integrins play key roles by supporting cancer cell proliferation, angiogenesis, and metastasis. The recognition that snake venom disintegrins can block integrin functions has spawned a number of studies to explore their cancer therapeutic potential. While dozens of different disintegrins have been isolated, none of them as yet has undergone clinical evaluation in cancer patients. Among the best-characterized and preclinically most advanced disintegrins is vicrostatin (VCN), a recombinant disintegrin that was rationally designed by fusing 62 N-terminal amino acids derived from the disintegrin contortrostatin with 6 C-terminal amino acids from echistatin, the disintegrins from another snake species. Bacterially produced VCN was shown to target multiple tumor-associated integrins, achieving potent anti-tumor and anti-angiogenic effects in in vitro and in vivo models in the absence of noticeable toxicity. This review will introduce the field of snake venom disintegrins as potential anticancer agents and illustrate the translational development and cancer-therapeutic potential of VCN as an example.

Antibacterial properties of snake venom components

An increasing problem in the field of health protection is the emergence of drug-resistant and multi-drug-resistant bacterial strains. They cause a number of infections, including hospital infections, which currently available antibiotics are unable to fight. Therefore, many studies are devoted to the search for new therapeutic agents with bactericidal and bacteriostatic properties. One of the latest concepts is to search for this type of substances among toxins produced by venomous animals. In this approach, however, special attention is paid to snake venom because it contains molecules with antibacterial properties. Thorough investigations have shown that the phospholipases A2 (PLA2) and l-amino acids oxidases (LAAO), as well as fragments of these enzymes, are mainly responsible for the bactericidal properties of snake venoms. Some preliminary research studies also suggest that fragments of three-finger toxins (3FTx) are bactericidal. It has also been proven that some snakes produce antibacterial peptides (AMP) homologous to human defensins and cathelicidins. The presence of these proteins and peptides means that snake venoms continue to be an interesting material for researchers and can be perceived as a promising source of antibacterial agents.