MEL-pep, an analog of melittin, disrupts cell membranes and reverses 5-fluorouracil resistance in human hepatocellular carcinoma cells

Recalculating the Route: Repositioning Antimicrobial Peptides for Cancer Treatment

Resistance to antimicrobial drugs has been considered a public health problem. Likewise, the increasing resistance of cancer cells to drugs currently used in therapy has also become a problem. Therefore, the research and development of synthetic peptides bring a new perspective on the emergence of new drugs for treating this resistance since bioinformatics provides a means to optimize these molecules and save time and costs in research. Peptides have several mechanisms of action, such as forming pores on the cell membrane and inhibiting protein synthesis. Some studies report the use of antimicrobial peptides with the potential for action against cancer cells, suggesting a repositioning of antimicrobial peptides to fight back cancer resistance. There is an alteration in the microenvironment, making its net charge negative for the survival and growth of cancer cells. The changes in glycoproteins favor the membrane to have a more negative charge, favoring the interaction between the cells and the peptide, thus making possible the repositioning of these antimicrobial peptides against cancer. Here, we will discuss the mechanism of action, targets and effects of peptides, comparison between microbial and cancer cells, and proteomic changes caused by the interaction of peptides and cells.

Melittin analog p5RHH enhances recombinant adeno-associated virus transduction efficiency

OBJECTIVE

Melittin and its derivative have been developed to support effective gene delivery systems. Their ability to facilitate endosomal release enhances the delivery of nanoparticle-based gene therapy. Nevertheless, its potential application in the context of viral vectors has not received much attention. Therefore, we would like to optimize the rAAV vector by Melittin analog to improve the transduction efficiency of rAAV in liver cancer cells and explore the mechanism of Melittin analog on rAAV.

METHODS

Various melittin-derived peptides were inserted into loop VIII of the capsid protein in recombinant adeno-associated virus vectors. These vectors carrying either gfp or fluc genes were subjected to quantitative polymerase chain reaction assays and transduction assays in human embryonic kidney 293 (HEK293T) cells to investigate the efficiency of vector production and gene delivery. In addition, the ability of a specific p5RHH-rAAV vector to deliver genes was examined through in vitro transduction of different cultured cells and in vivo tail vein administration to C57BL/6 mice. Finally, the intricate details of the vector-mediated transduction mechanisms were explored by using pharmacological inhibitors of every stage of the rAAV2 intracellular life cycle.

RESULTS

A total of 76 melittin-related peptides were identified from existing literature. Among them, CMA-3, p5RHH and aAR3 were found to significantly inhibit transduction of rAAV2 vector crude lysate. The p5RHH-rAAV2 vectors efficiently transduced not only rAAV-potent cell lines but also cell lines previously considered resistant to rAAV. Mechanistically, bafilomycin A1, a vacuolar endosome acidification inhibitor, completely inhibited the transgene expression mediated by the p5RHH-rAAV2 vectors. Most importantly, p5RHH-rAAV8 vectors also increased hepatic transduction in vivo in C57BL/6 mice.

CONCLUSION

The incorporation of melittin analogs into the rAAV capsids results in a significant improvement in rAAV-mediated transgene expression. While further modifications remain an area of interest, our studies have substantially broadened the pharmacological prospects of melittin in the context of viral vector-mediated gene delivery. Please cite this article as: Meng J, He Y, Yang H, Zhou L, Wang S, Feng X, Al-shargi OY, Yu X, Zhu L, Ling, C. Melittin analog p5RHH enhances recombinant adeno-associated virus transduction efficiency. J Integr Med. 2024; 22(1): 72-82.

Chemical Strategies towards the Development of Effective Anticancer Peptides

Cancer is increasingly recognized as one of the primary causes of death and has become a multifaceted global health issue. Modern medical science has made significant advancements in the diagnosis and therapy of cancer over the past decade. The detrimental side effects, lack of efficacy, and multidrug resistance of conventional cancer therapies have created an urgent need for novel anticancer therapeutics or treatments with low cytotoxicity and drug resistance. The pharmaceutical groups have recognized the crucial role that peptide therapeutic agents can play in addressing unsatisfied healthcare demands and how these become great supplements or even preferable alternatives to biological therapies and small molecules. Anticancer peptides, as a vibrant therapeutic strategy against various cancer cells, have demonstrated incredible anticancer potential due to high specificity and selectivity, low toxicity, and the ability to target the surface of traditional "undruggable" proteins. This review will provide the research progression of anticancer peptides, mainly focusing on the discovery and modifications along with the optimization and application of these peptides in clinical practice.

Application Value of Antimicrobial Peptides in Gastrointestinal Tumors

Gastrointestinal cancer is a common clinical malignant tumor disease that seriously endangers human health and lacks effective treatment methods. As part of the innate immune defense of many organisms, antimicrobial peptides not only have broad-spectrum antibacterial activity but also can specifically kill tumor cells. The positive charge of antimicrobial peptides under neutral conditions determines their high selectivity to tumor cells. In addition, antimicrobial peptides also have unique anticancer mechanisms, such as inducing apoptosis, autophagy, cell cycle arrest, membrane destruction, and inhibition of metastasis, which highlights the low drug resistance and high specificity of antimicrobial peptides. In this review, we summarize the related studies on antimicrobial peptides in the treatment of digestive tract tumors, mainly oral cancer, esophageal cancer, gastric cancer, liver cancer, pancreatic cancer, and colorectal cancer. This paper describes the therapeutic advantages of antimicrobial peptides due to their unique anticancer mechanisms. The length, net charge, and secondary structure of antimicrobial peptides can be modified by design or modification to further enhance their anticancer effects. In summary, as an emerging cancer treatment drug, antimicrobial peptides need to be further studied to realize their application in gastrointestinal cancer diseases.

Combating drug resistance in hepatocellular carcinoma: No awareness today, no action tomorrow

Hepatocellular carcinoma (HCC), the sixth most common cancer worldwide, is associated with a high degree of malignancy and poor prognosis. Patients with early HCC may benefit from surgical resection to remove tumor tissue and a margin of healthy tissue surrounding it. Unfortunately, most patients with HCC are diagnosed at an advanced or distant stage, at which point resection is not feasible. Systemic therapy is now routinely prescribed to patients with advanced HCC; however, drug resistance has become a major obstacle to the treatment of HCC and exploring purported mechanisms promoting drug resistance remains a challenge. Here, we focus on the determinants of drug resistance from the perspective of non-coding RNAs (ncRNAs), liver cancer stem cells (LCSCs), autophagy, epithelial-mesenchymal transition (EMT), exosomes, ferroptosis, and the tumor microenvironment (TME), with the aim to provide new insights into HCC treatment.

An Updated Review Summarizing the Anticancer Efficacy of Melittin from Bee Venom in Several Models of Human Cancers

Apitherapy (using bee products) has gained broad recognition in cancer therapeutics globally. Honeybee venom has a broad range of biological potential, and its utilization is rapidly emerging in apitherapy. Bee products have significant potential to strengthen the immune system and improve human health. Thus, this review is targeted toward recapitulating the chemo-preventive potential of melittin (MEL), which constitutes a substantial portion of honeybee venom. Honeybee venom (apitoxin) is produced in the venom gland of the honeybee abdomen, and adult bees utilize it as a primary colony defense mechanism. Apitoxin comprises numerous biologically active compounds, including peptides, enzymes, amines, amino acids, phospholipids, minerals, carbohydrates, and volatile components. We are mainly focused on exploring the potential of melittin (a peptide component) of bee venom that has shown promising potential in the treatment of several human cancers, including breast, stomach, lung, prostate, ovary, kidney, colon, gastric, esophageal, cervical cancers, melanoma, osteosarcoma, and hepatocellular carcinoma. This review has summarized all potential studies related to the anticancerous efficacy of melittin (apitoxin), its formulations, conjugates, and nano-formulations against several human carcinomas, which would further pave the way for future researchers in developing potent drugs for cancer management.

Development of Polymersomes Co-Delivering Doxorubicin and Melittin to Overcome Multidrug Resistance

Multidrug resistance (MDR) is one of the major barriers in chemotherapy. It is often related to the overexpression of efflux receptors such as P-glycoprotein (P-gp). Overexpressed efflux receptors inhibit chemotherapeutic efficacy by pumping out intracellularly delivered anticancer drugs. In P-gp-mediated MDR-related pathways, PI3K/Akt and NF-kB pathways are commonly activated signaling pathways, but these pathways are downregulated by melittin, a main component of bee venom. In this study, a polymersome based on a poly (lactic acid) (PLA)-hyaluronic acid (HA) (20k-10k) di-block copolymer and encapsulating melittin and doxorubicin was developed to overcome anticancer resistance and enhance chemotherapeutic efficacy. Through the simultaneous delivery of doxorubicin and melittin, PI3K/Akt and NF-κB pathways could be effectively inhibited, thereby downregulating P-gp and successfully enhancing chemotherapeutic efficacy. In conclusion, a polymersome carrying an anticancer drug and melittin could overcome MDR by regulating P-gp overexpression pathways.

Pharmacological effects and mechanisms of bee venom and its main components: Recent progress and perspective

Bee venom (BV), a type of defensive venom, has been confirmed to have favorable activities, such as anti-tumor, neuroprotective, anti-inflammatory, analgesic, anti-infectivity effects, etc. This study reviewed the recent progress on the pharmacological effects and mechanisms of BV and its main components against cancer, neurological disorders, inflammatory diseases, pain, microbial diseases, liver, kidney, lung and muscle injury, and other diseases in literature during the years 2018–2021. The related target proteins of BV and its main components against the diseases include Akt, mTOR, JNK, Wnt-5α, HIF-1α, NF-κB, JAK2, Nrf2, BDNF, Smad2/3, AMPK, and so on, which are referring to PI3K/Akt/mTOR, MAPK, Wnt/β-catenin, HIF-1α, NF-κB, JAK/STAT, Nrf2/HO-1, TrkB/CREB/BDNF, TGF-β/Smad2/3, and AMPK signaling pathways, etc. Further, with the reported targets, the potential effects and mechanisms on diseases were bioinformatically predicted via Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway, disease ontology semantic and enrichment (DOSE) and protein-protein interaction (PPI) analyses. This review provides new insights into the therapeutic effects and mechanisms of BV and its main components on diseases.

Development of Anticancer Peptides Using Artificial Intelligence and Combinational Therapy for Cancer Therapeutics

Cancer is a group of diseases causing abnormal cell growth, altering the genome, and invading or spreading to other parts of the body. Among therapeutic peptide drugs, anticancer peptides (ACPs) have been considered to target and kill cancer cells because cancer cells have unique characteristics such as a high negative charge and abundance of microvilli in the cell membrane when compared to a normal cell. ACPs have several advantages, such as high specificity, cost-effectiveness, low immunogenicity, minimal toxicity, and high tolerance under normal physiological conditions. However, the development and identification of ACPs are time-consuming and expensive in traditional wet-lab-based approaches. Thus, the application of artificial intelligence on the approaches can save time and reduce the cost to identify candidate ACPs. Recently, machine learning (ML), deep learning (DL), and hybrid learning (ML combined DL) have emerged into the development of ACPs without experimental analysis, owing to advances in computer power and big data from the power system. Additionally, we suggest that combination therapy with classical approaches and ACPs might be one of the impactful approaches to increase the efficiency of cancer therapy.

Stable Loading and Delivery of Melittin with Lipid-Coated Polymeric Nanoparticles for Effective Tumor Therapy with Negligible Systemic Toxicity

Melittin is a potential anticancer candidate with remarkable antitumor activity and ability to overcome tumor drug resistance. However, the clinical applications of melittin are largely restricted by its severe hemolytic activity and nonspecific cytotoxicity after systemic administration. Here, a biocompatible and stable melittin-loaded lipid-coated polymeric nanoparticle (MpG@LPN) formulation that contains a melittin/poly-γ-glutamic acid nanoparticle inner core, a lipid membrane middle layer, and a polyethylene glycol (PEG) and PEG-targeting molecule outer shell was designed. The formulations were prepared by applying a self-assembly procedure based on intermolecular interactions, including electrostatic attraction and hydrophobic effect. The core-shell MpG@LPN presented high efficiency for melittin encapsulation and high stability in physiological conditions. Hemolysis and cell proliferation assays showed that the PEG-modified MpG@LPN had almost no hemolytic activity and nonspecific cytotoxicity even at high concentrations. The modification of targeting molecules on the MpG@LPNs allowed for the selective binding with target tumor cells and cytolytic activity via apoptosis induction. In vivo experiments revealed that MpG@LPNs can remarkably inhibit the growth of tumors without the occurrence of hemolysis and tissue toxicity. Results suggested that the developed MpG@LPN with a core-shell structure can effectively address the main obstacles of melittin in clinical applications and has great potential in cancer treatment.

The effects and mechanisms of aloe-emodin on reversing adriamycin-induced resistance of MCF-7/ADR cells

Multidrug resistance (MDR) is one of the major obstacles for clinical effective chemotherapy. In this study, the effects and possible mechanisms of aloe-emodin (AE) were investigated on reversing the adriamycin (ADR)-induced resistance of MCF-7/ADR cells. AE could significantly reverse the ADR resistance in MCF-7/ADR cells. The combination of AE (20 μM) and ADR had no effect on the P-glycoprotein (P-gp) level, but notably promoted the accumulation of ADR in drug-resistant cells. The efflux function of P-gp required ATP, but AE reduced the intracellular ATP level. AE played a reversal role might through inhibiting the efflux function of P-gp. The research result of energy metabolism pathways indicated that combination of AE and ADR could inhibit glycolysis, tricarboxylic acid (TCA) cycle, glutamine metabolism, and related amino acid synthesis pathways. Moreover, we found AE not only reversed ADR-induced resistant but also induced autophagy as a defense mechanism. In addition, the combination of AE and ADR arrested G2/M cell cycle and induced apoptosis through DNA damage, ROS generation, caspase-3 activation. Our study indicated that AE could be a potential reversal agent to resensitize ADR resistant in tumor chemotherapy and inhibiting autophagy might be an effective strategy to further enhance the reversal activity of AE.

Melittin sensitizes skin squamous carcinoma cells to 5-fluorouracil by affecting cell proliferation and survival

Combined 5-fluorouracil (5-FU) and melittin (MEL) is believed to enhance cytotoxic effects on skin squamous cell carcinoma (SCC). However, the rationale underlying cytotoxicity is fundamentally important for a proper design of combination chemotherapy, and to provide translational insights for future therapeutics in the dermatology field. The aim was to elucidate the effects of 5-FU/MEL combination on the viability, proliferation and key structures of human squamous cell carcinoma (A431). Morphology, plasma membrane, DNA, mitochondria, oxidative stress, cell viability, proliferation and cell death pathways were targeted for investigation by microscopy, MTT, trypan blue assay, flow cytometry and real-time cell analysis. 5-FU/MEL (0.25 µM/0.52 µM) enhanced the cytotoxic effect in A431 cells (74.46%, p < .001) after 72 h exposure, showing greater cytotoxic effect when compared to each isolated compound (45.55% 5-FU and 61.78% MEL). The results suggest that MEL induces plasma membrane alterations that culminate in a loss of integrity at subsequent times, sensitizing the cell to 5-FU action. DNA fragmentation, S and G2/M arrest, disruption of mitochondrial metabolism, and alterations in cell morphology culminated in proliferation blockage and apoptosis. 5-FU/MEL combination design optimizes the cytotoxic effects of each drug at lower concentrations, which may represent an innovative strategy for SCC therapy.

Targeting Cancer Heterogeneity with Immune Responses Driven by Oncolytic Peptides

Accumulating preclinical and clinical evidence indicates that high degrees of heterogeneity among malignant cells constitute a considerable obstacle to the success of cancer therapy. This calls for the development of approaches that operate - or enable established treatments to operate - despite such intratumoral heterogeneity (ITH). In this context, oncolytic peptides stand out as promising therapeutic tools based on their ability to drive immunogenic cell death associated with robust anticancer immune responses independently of ITH. We review the main molecular and immunological pathways engaged by oncolytic peptides, and discuss potential approaches to combine these agents with modern immunotherapeutics in support of superior tumor-targeting immunity and efficacy in patients with cancer.

Melittin Increases Cisplatin Sensitivity and Kills KM-H2 and L-428 Hodgkin Lymphoma Cells

Hodgkin lymphoma (HL) is neoplasia with high cure rates. However, not all patients can be cured with the current treatment. Chemo-resistance of tumor cells is one factor involved in treatment failure. In addition to its pore-forming activity on lipid bilayer membranes, the toxin melittin from bee venom is an inhibitor of several cancer-related signaling pathways. Moreover, melittin analogs have been shown to inhibit the activity of ATP binding cassette (ABC) transporters which are known to play important roles in the chemo-resistance of tumor cells. Therefore, we tested the toxicity of melittin for HL cell lines KM-H2 and L-428 and whether melittin can increase the chemo-sensitivity of cisplatin-resistant HL cells. We found high toxicity of melittin for KM-H2 and L-428 cells. In co-cultures with normal blood cells, melittin preferentially killed KM-H2 and L-428 cells. In addition, we observed increased cisplatin sensitivity of chemo-resistant L-428 cells after treatment with melittin. ABC transporter activity was not reduced after treatment with melittin. Our data suggest that melittin or melittin analogs might be promising agents for the future development of treatment strategies for HL patients with resistant disease.

Venom peptides in cancer therapy: An updated review on cellular and molecular aspects

Based on the high incidence and mortality rates of cancer, its therapy remains one of the most vital challenges in the field of medicine. Consequently, enhancing the efficacy of currently applied treatments and finding novel strategies are of great importance for cancer treatment. Venoms are important sources of a variety of bioactive compounds including salts, small molecules, macromolecules, proteins, and peptides that are defined as toxins. They can exhibit different pharmacological effects, and in recent years, their anti-tumor activities have gained significant attention. Several different compounds are responsible for the anti-tumor activity of venoms, and peptides are one of them. In the present review, we discuss the possible anti-tumor activities of venom peptides by highlighting molecular pathways and mechanisms through which these molecules can act effectively. Venom peptides can induce cell death in cancer cells and can substantially enhance the efficacy of chemotherapy and radiotherapy. Also, the venom peptides can mitigate the migration of cancer cells via suppression of angiogenesis and epithelial-to-mesenchymal transition. Notably, nanoparticles have been applied in enhancing the bioavailability of venom peptides and providing targeted delivery, thereby leading to their elevated anti-tumor activity and potential application for cancer therapy.

Facile Fabrication of Nanoparticles with Dual-Targeting Ligands for Precise Hepatocellular Carcinoma Therapy In Vitro and In Vivo

Efficient hepatocellular carcinoma (HCC) therapy remains a significant challenge due to the unsatisfactory targeting efficiency of nanoparticles (NPs) with either a passive targeting or a single active targeting property. Although a dual-targeting mechanism-based strategy can promote the partial targeting efficiency, most of the reported NPs with dual-targeting properties generally suffer from sophisticated chemical design, multistep synthesis, and purification procedures, leading to batch-to-batch variation and difficulties in scalable production. To develop a facile yet efficient strategy toward dual-targeting ligand-functionalized NPs for precise HCC therapy and potential clinical translation, folic acid (FA) was readily introduced as a hydrophobic and targeting component to a hydrophilic macromolecular prodrug, galactosylated chitosan-5-fluorouracil acetic acid (GC-FU), to afford FA-GC-FU formulation that can self-assemble into NPs driven by the solubility variation of FA and GC-FU without the necessity of previously used physical cross-linking. The resulting nanoparticles of FA-GC-FU can target the overexpressed asialoglycoprotein receptors (ASGPRs) and folate receptors (FRs) on the surface of HCC cells, respectively, via the FA and lactobionic acid (LA) residues exposed on the surface of the NPs, leading to the maximized targeting efficiency of HCC and minimized nonspecific uptake by normal hepatocytes in vitro and in vivo. Therefore, this study not only developed a simple yet efficient strategy toward a facile fabrication of NPs with dual-targeting ligands but also presented a precise therapeutic platform for HCC with great potential for clinical translation.

Anti-cancer peptides: classification, mechanism of action, reconstruction and modification

Anti-cancer peptides (ACPs) are a series of short peptides composed of 10-60 amino acids that can inhibit tumour cell proliferation or migration, or suppress the formation of tumour blood vessels, and are less likely to cause drug resistance. The aforementioned merits make ACPs the most promising anti-cancer candidate. However, ACPs may be degraded by proteases, or result in cytotoxicity in many cases. To overcome these drawbacks, a plethora of research has focused on reconstruction or modification of ACPs to improve their anti-cancer activity, while reducing their cytotoxicity. The modification of ACPs mainly includes main chain reconstruction and side chain modification. After summarizing the classification and mechanism of action of ACPs, this paper focuses on recent development and progress about their reconstruction and modification. The information collected here may provide some ideas for further research on ACPs, in particular their modification.

Baicalein and baicalin promote antitumor immunity by suppressing PD-L1 expression in hepatocellular carcinoma cells

Blocking the PD-L1/PD-1 pathway to prevent the immune evasion of tumor cells is a powerful approach for treating multiple cancers, including hepatocellular carcinoma (HCC). Previous studies have shown that baicalein and baicalin are directly cytotoxic to some tumors, here we demonstrate that in addition to direct cytotoxicity, these two flavonoids stimulate the T cell mediated immune response against tumors through reduction of PD-L1 expression in cancer cells. Interestingly, more significant tumor regression was observed in BALB/c mice than in BALB/c-nu/nu mice after baicalein and baicalin treatment. PD-L1 upregulation induced by interferon-γ (IFN-γ) was significantly inhibited by these two flavonoids in vitro. Both baicalein and baicalin enhanced the cytotoxicity of T cells to eliminate tumor cells, which was abrogated after HCC cells were transfected with a PD-L1 overexpression plasmid or after T cells were pretreated with an anti-PD-1 blocking antibody. Further mechanistic research indicated that the IFN-γ-induced expression and promoter activity of PD-L1 were suppressed by these two flavonoids, and these effects were mediated by STAT3 activity inhibition. Therefore, baicalein and baicalin decreased STAT3 activity, further downregulated IFN-γ-induced PD-L1 expression and subsequently restored T cell sensitivity to kill tumor cells. Our findings provide novel insight into the anticancer effects of baicalein and baicalin through which tumor growth is inhibited by PD-L1 expression downregulation and suggest that these flavonoids have great potential for clinical treatment.

Melittin Inhibits Hypoxia-Induced Vasculogenic Mimicry Formation and Epithelial-Mesenchymal Transition through Suppression of HIF-1α/Akt Pathway in Liver Cancer

In this study, we investigated whether melittin could suppress hypoxia-induced vasculogenic mimicry (VM) formation in liver cancer and explored the underlying mechanisms. Melittin significantly inhibited the proliferation of liver cancer cells with or without CoCl₂ presence. Melittin also significantly inhibited CoCl₂-induced migration, invasion, and VM formation of liver cancer cells. CoCl₂ treatment suppressed the expression of E-cadherin and elevated the expression of N-cadherin and Vimentin. Melittin reversed the changes in the protein and mRNA levels of these epithelial-mesenchymal transition (EMT) markers. CoCl₂-induced accumulation of HIF-1α increased the level of phosphorylated Akt and upregulated the expression of VEGF and MMP-2/9. Melittin decreased the HIF-1α level and thereby suppressed the levels of p-Akt, VEGF, and MMP-2/9. In addition, the inhibitor of PI3K/Akt also suppressed CoCl₂-induced EMT and liver cancer cells migration, and the activator of Akt, SC-79, partly blocked the effect of melittin on CoCl₂-induced EMT and liver cancer cells migration. In the xenograft tumor model in nude mice, melittin treatment significantly suppressed the tumor growth, VM formation, and HIF-1α expression in the tumor. In conclusion, this study indicates melittin may inhibit hypoxia-induced VM formation and EMT in liver cancer through inhibiting HIF-1α/Akt pathway.