Novel synthetic cyclic integrin αvβ3 binding peptide ALOS4: Antitumor activity in mouse melanoma models

Small molecule- and peptide-drug conjugates addressing integrins: A story of targeted cancer treatment

Targeted cancer treatment should avoid side effects and damage to healthy cells commonly encountered during traditional chemotherapy. By combining small molecule or peptidic ligands as homing devices with cytotoxic drugs connected by a cleavable or non-cleavable linker in peptide-drug conjugates (PDCs) or small molecule-drug conjugates (SMDCs), cancer cells and tumours can be selectively targeted. The development of highly affine, selective peptides and small molecules in recent years has allowed PDCs and SMDCs to increasingly compete with antibody-drug conjugates (ADCs). Integrins represent an excellent target for conjugates because they are overexpressed by most cancer cells and because of the broad knowledge about native binding partners as well as the multitude of small-molecule and peptidic ligands that have been developed over the last 30 years. In particular, integrin αVβ3 has been addressed using a variety of different PDCs and SMDCs over the last two decades, following various strategies. This review summarises and describes integrin-addressing PDCs and SMDCs while highlighting points of great interest.

Delivery of Theranostic Nanoparticles to Various Cancers by Means of Integrin-Binding Peptides

Active targeting of tumors is believed to be the key to efficient cancer therapy and accurate, early-stage diagnostics. Active targeting implies minimized off-targeting and associated cytotoxicity towards healthy tissue. One way to acquire active targeting is to employ conjugates of therapeutic agents with ligands known to bind receptors overexpressed onto cancer cells. The integrin receptor family has been studied as a target for cancer treatment for almost fifty years. However, systematic knowledge on their effects on cancer cells, is yet lacking, especially when utilized as an active targeting ligand for particulate formulations. Decoration with various integrin-targeting peptides has been reported to increase nanoparticle accumulation in tumors ≥ 3-fold when compared to passively targeted delivery. In recent years, many newly discovered or rationally designed integrin-binding peptides with excellent specificity towards a single integrin receptor have emerged. Here, we show a comprehensive analysis of previously unreviewed integrin-binding peptides, provide diverse modification routes for nanoparticle conjugation, and showcase the most notable examples of their use for tumor and metastases visualization and eradication to date, as well as possibilities for combined cancer therapies for a synergetic effect. This review aims to highlight the latest advancements in integrin-binding peptide development and is directed to aid transition to the development of novel nanoparticle-based theranostic agents for cancer therapy.

Targeted Modulation of Interferon Response-Related Genes with IFN-Alpha/Lambda Inhibition

Interferon (IFN) signaling resulting from external or internal inflammatory processes initiates the rapid release of cytokines and chemokines to target viral or bacterial invasion, as well as cancer and other diseases. Prolonged exposure to IFNs, or the overexpression of other cytokines, leads to immune exhaustion, enhancing inflammation and leading to the persistence of infection and promotion of disease. Hence, to control and stabilize an excessive immune response, approaches for the management of inflammation are required. The potential use of peptides as anti-inflammatory agents has been previously demonstrated. Our team discovered, and previously published, a 9-amino-acid cyclic peptide named ALOS4 which exhibits anti-cancer properties in vivo and in vitro. We suggested that the anti-cancer effect of ALOS4 arises from interaction with the immune system, possibly through the modulation of inflammatory processes. Here, we show that treatment with ALOS4 decreases basal cytokine levels in mice with chronic inflammation and prolongs the lifespan of mice with acute systemic inflammation induced by irradiation. We also show that pretreatment with ALOS4 reduces the expression of IFN alpha, IFN lambda, and selected interferon-response genes triggered by polyinosinic-polycytidylic acid (Poly I:C), a synthetic analog of viral double-stranded RNA, while upregulating the expression of other genes with antiviral activity. Hence, we conclude that ALOS4 does not prevent IFN signaling, but rather supports the antiviral response by upregulating the expression of interferon-response genes in an interferon-independent manner.

Peptide-Based Bioconjugates and Therapeutics for Targeted Anticancer Therapy

With rapidly growing knowledge in bioinformatics related to peptides and proteins, amino acid-based drug-design strategies have recently gained importance in pharmaceutics. In the past, peptide-based biomedicines were not widely used due to the associated severe physiological problems, such as low selectivity and rapid degradation in biological systems. However, various interesting peptide-based therapeutics combined with drug-delivery systems have recently emerged. Many of these candidates have been developed for anticancer therapy that requires precisely targeted effects and low toxicity. These research trends have become more diverse and complex owing to nanomedicine and antibody–drug conjugates (ADC), showing excellent therapeutic efficacy. Various newly developed peptide–drug conjugates (PDC), peptide-based nanoparticles, and prodrugs could represent a promising therapeutic strategy for patients. In this review, we provide valuable insights into rational drug design and development for future pharmaceutics.

Anti-Cancer Effects of Cyclic Peptide ALOS4 in a Human Melanoma Mouse Model

We examined the effects of ALOS4, a cyclic peptide discovered previously by phage library selection against integrin α_vβ₃, on a human melanoma (A375) xenograft model to determine its abilities as a potential anti-cancer agent. We found that ALOS4 promoted healthy weight gain in A375-engrafted nude mice and reduced melanoma tumor mass and volume. Despite these positive changes, examination of the tumor tissue did not indicate any significant effects on proliferation, mitotic index, tissue vascularization, or reduction of αSMA or Ki-67 tumor markers. Modulation in overall expression of critical downstream α_vβ₃ integrin factors, such as FAK and Src, as well as reductions in gene expression of c-Fos and c-Jun transcription factors, indirectly confirmed our suspicions that ALOS4 is likely acting through an integrin-mediated pathway. Further, we found no overt formulation issues with ALOS4 regarding interaction with standard inert laboratory materials (polypropylene, borosilicate glass) or with pH and temperature stability under prolonged storage. Collectively, ALOS4 appears to be safe, chemically stable, and produces anti-cancer effects in a human xenograft model of melanoma. We believe these results suggest a role for ALOS4 in an integrin-mediated pathway in exerting its anti-cancer effects possibly through immune response modulation.

The Functional Significance of Endocrine-immune Interactions in Health and Disease

Hormones are known to influence various body systems that include skeletal, cardiac, digestive, excretory, and immune systems. Emerging investigations suggest the key role played by secretions of endocrine glands in immune cell differentiation, proliferation, activation, and memory attributes of the immune system. The link between steroid hormones such as glucocorticoids and inflammation is widely known. However, the role of peptide hormones and amino acid derivatives such as growth and thyroid hormones, prolactin, dopamine, and thymopoietin in regulating the functioning of the immune system remains unclear. Here, we reviewed the findings pertinent to the functional role of hormone-immune interactions in health and disease and proposed perspective directions for translational research in the field.

Molecular Delivery of Cytotoxic Agents via Integrin Activation

Integrins are cell adhesion receptors overexpressed in tumor cells. A direct inhibition of integrins was investigated, but the best inhibitors performed poorly in clinical trials. A gained attention towards these receptors arouse because they could be target for a selective transport of cytotoxic agents. Several active-targeting systems have been developed to use integrins as a selective cell entrance for some antitumor agents. The aim of this review paper is to report on the most recent results on covalent conjugates between integrin ligands and antitumor drugs. Cytotoxic drugs thus conjugated through specific linker to integrin ligands, mainly RGD peptides, demonstrated that the covalent conjugates were more selective against tumor cells and hopefully with fewer side effects than the free drugs.

Antitumor activity of integrin αVβ3 antibody conjugated-cationic microbubbles in liver cancer

Background

The overexpression of integrin α_Vβ₃ in hepatocarcinoma (HCC) promotes tumor progression, metastasis, and clinical staging. Thus, the inhibition of integrin α_Vβ₃ might be potentially effective as an anti-cancer agent in HCC.

Methods

In this study, we aimed to investigate the antitumor effect of integrin α_Vβ₃ antibody conjugated cationic microbubbles (CMBs) in HCC model. By conjugating with integrin α_Vβ₃ antibody with non-targeting CMBs, CMBs_αvβ3 was constructed. The antitumor effect of CMBs_αvβ3 was evaluated in HepG2 cells in vitro and in HepG2 xenograft mice models. Bcl-2, p53 and CD31 mRNA level, and caspase-3 activity were examined in xenograft tumors. Cell proliferation assay and scratch test were performed to evaluate the anti-migrant effect of CMBs_αvβ3in vitro.

Results

CMBs_αvβ3 could specifically target to HCC HepG2 cells and improve pEGFP-KDRP-CD/TK plasmid transfection efficiency. In HepG2 xenograft mice models, CMBs_αvβ3 treatment significantly suppressed tumor weights and volumes. CMBs_αvβ3 treatment suppressed Bcl-2 and p53 mRNA level in tumors. In HepG2 cells, CMBs_αvβ3 significantly impaired wound healing and inhibited cell proliferation. Moreover, when combined with CD/TK double suicide gene transfection and 5-FC/GCV treatment, caspase-3 was activated and the cell proliferation was tremendously inhibited.

Conclusions

CMBs_αvβ3 not only suppresses cell migration and proliferation, but also facilitates 5-FC/GCV plus CD/TK double suicide gene-induced apoptotic cell death. CMBs_αvβ3 is a promising gene delivery agent with potential anti-tumor activity itself.

Toward the development of a novel non-RGD cyclic peptide drug conjugate for treatment of human metastatic melanoma

The newly discovered short (9 amino acid) non-RGD S-S bridged cyclic peptide ALOS-4 (H-cycl(Cys-Ser-Ser-Ala-Gly-Ser-Leu-Phe-Cys)-OH), which binds to integrin α_vβ₃ is investigated as peptide carrier for targeted drug delivery against human metastatic melanoma. ALOS4 binds specifically the α_vβ₃ overexpressing human metastatic melanoma WM-266-4 cell line both in vitro and in ex vivo assays. Coupling ALOS4 to the topoisomerase I inhibitor Camptothecin (ALOS4-CPT) increases the cytotoxicity of CPT against human metastatic melanoma cells while reduces dramatically the cytotoxicity against non-cancerous cells as measured by the levels of γH2A.X, active caspase 3 and cell viability. Moreover, conjugating ALOS4 to CPT even increases the chemo-stability of CPT under physiological pH. Bioinformatic analysis using Rosetta platform revealed potential docking sites of ALOS4 on the α_vβ₃ integrin which are distinct from the RGD binding sites. We propose to use this specific non-RGD cyclic peptide as the therapeutic carrier for conjugation of drugs in order to improve efficacy and reduce toxicity of currently available treatments of human malignant melanoma.

Cytokines, growth factors and macromolecules as mediators of implantation in mammalian species

Implantation is one of the most critical steps in mammalian reproduction and implantation failure constitutes a major cause of infertility in both animals and humans. The mechanism of implantation is exclusively under the control of ovarian steroids progesterone and oestrogen whose actions are mediated in a complex phenomenon that involves a number of cytokines and growth factors. According to a plethora of literature on implantation in mammalian species, prominent of these cytokines and growth factor playing crucial roles in implantation include integrin, osteopontin, integrin, insulin-like growth factor and leukaemia inhibitory factor. Others are cluster domain 44, hyaluronan system and many non-adhesive molecules such as glycoprotein mucin 1. In this review, the specific roles played by these molecules are expatiated. Generally, they function as adhesive molecules that facilitate attachment of ligands/proteins on the trophectoderm to their respective receptors on endometrial luminal epithelia or vice versa. Sometimes, they also function as signalling molecules that enhance communication between implanting blastocyst and receptive endometrium. This is of particular importance in embryo culture and embryo transfer where in vitro derived blastocyst unlike the in vivo condition, is not exposed to these substances and hence, their absence may be partly responsible for the low implantation rate observed in the surrogate. Appreciation of the roles played by these cytokines, growth factors and molecules as revealed in this review will spur further research on these topics, facilitate their inclusion in embryo culture media (if positively required) and are considered as vital aspect while developing strategies to improve fertility.

Inside the Cell: Integrins as New Governors of Nuclear Alterations?

Cancer cell migration is a complex process that requires coordinated structural changes and signals in multiple cellular compartments. The nucleus is the biggest and stiffest organelle of the cell and might alter its physical properties to allow cancer cell movement. Integrins are transmembrane receptors that mediate cell-cell and cell-extracellular matrix interactions, which regulate numerous intracellular signals and biological functions under physiological conditions. Moreover, integrins orchestrate changes in tumor cells and their microenvironment that lead to cancer growth, survival and invasiveness. Most of the research efforts have focused on targeting integrin-mediated adhesion and signaling. Recent exciting data suggest the crucial role of integrins in controlling internal cellular structures and nuclear alterations during cancer cell migration. Here we review the emerging role of integrins in nuclear biology. We highlight increasing evidence that integrins are critical for changes in multiple nuclear components, the positioning of the nucleus and its mechanical properties during cancer cell migration. Finally, we discuss how integrins are integral proteins linking the plasma membrane and the nucleus, and how they control cell migration to enable cancer invasion and infiltration. The functional connections between these cell receptors and the nucleus will serve to define new attractive therapeutic targets.

Peptides for tumor-specific drug targeting: state of the art and beyond

This review outlines the most recent advances in peptide-mediated tumor-targeting and gives insight into the direction of the field.