Molecular Delivery of Cytotoxic Agents via Integrin Activation

Targeting Cytotoxic Agents through EGFR-Mediated Covalent Binding and Release

A major drawback of cytotoxic chemotherapy is the lack of selectivity toward noncancerous cells. The targeted delivery of cytotoxic drugs to tumor cells is a longstanding goal in cancer research. We proposed that covalent inhibitors could be adapted to deliver cytotoxic agents, conjugated to the β-position of the Michael acceptor, via an addition-elimination mechanism promoted by covalent binding. Studies on model systems showed that conjugated 5-fluorouracil (5FU) could be released upon thiol addition in relevant time scales. A series of covalent epidermal growth factor receptor (EGFR) inhibitors were synthesized as their 5FU derivatives. Achieving the desired release of 5FU was demonstrated to depend on the electronics and geometry of the compounds. Mass spectrometry and NMR studies demonstrated an anilinoquinazoline acrylate ester conjugate bound to EGFR with the release of 5FU. This work establishes that acrylates can be used to release conjugated molecules upon covalent binding to proteins and could be used to develop targeted therapeutics.

Fabrication of curcumin-loaded magnetic PEGylated-PLGA nanocarriers tagged with GRGDS peptide for improving anticancer activity

Carrier-mediated drug delivery systems are highly promising as a treatment option for the targeted delivery of potent cytotoxic drugs with increased efficacy and safety. Considering that poly (lactic-co-glycolic acid) (PLGA) and polyethylene glycol (PEG) polymers each provide certain advantages for biological purposes, PEGylated-PLGA nanoparticles have emerged as a leading candidate among other alternatives. Furthermore, these nanoparticles can be modified with the specific short peptide sequences such as glycine-arginine-glycine-aspartic acid‑serine (GRGDS), which selectively binds to integrins overexpressed in most cancer cells, allowing for targeted delivery. Here, we reported the details in fabrication and characterization of magnetic PEGylated-PLGA nanoparticles functionalized with GRGDS peptide. In addition, superparamagnetic iron oxide nanoparticles (SPIONs) and the natural pharmaceutical compound curcumin (Cur) were loaded into these polymeric nanoparticles to assess their anticancer activity potential. Overall, this study provides comprehensive methodologies, including all synthesis procedures, challenges, and useful suggestions for peptide-conjugated polymeric nanoparticles that may be used for cellular targeting and therapeutic applications.•Step by step fabrication protocol for the Cur loaded magnetic PEGylated-PLGA nanoparticles was presented.•Validation of the fabrication and the GRGDS conjugation to the nanoparticles were shown via detailed characterization studies.•The cytotoxic effect of the Cur-loaded and GRGDS-tagged magnetic nanoparticles was tested on T98G glioblastoma cell line as a preliminary in vitro study.

Targeting Integrins for Cancer Therapy - Disappointments and Opportunities

Integrins mediate adhesive interactions between cells and their environment, including neighboring cells and extracellular matrix (ECM). These heterodimeric transmembrane receptors bind extracellular ligands with their globular head domains and connect to the cytoskeleton through multi-protein interactions at their cytoplasmic tails. Integrin containing cell–matrix adhesions are dynamic force-responsive protein complexes that allow bidirectional mechanical coupling of cells with their environment. This allows cells to sense and modulate tissue mechanics and regulates intracellular signaling impacting on cell faith, survival, proliferation, and differentiation programs. Dysregulation of these functions has been extensively reported in cancer and associated with tumor growth, invasion, angiogenesis, metastasis, and therapy resistance. This central role in multiple hallmarks of cancer and their localization on the cell surface makes integrins attractive targets for cancer therapy. However, despite a wealth of highly encouraging preclinical data, targeting integrin adhesion complexes in clinical trials has thus far failed to meet expectations. Contributing factors to therapeutic failure are 1) variable integrin expression, 2) redundancy in integrin function, 3) distinct roles of integrins at various disease stages, and 4) sequestering of therapeutics by integrin-containing tumor-derived extracellular vesicles. Despite disappointing clinical results, new promising approaches are being investigated that highlight the potential of integrins as targets or prognostic biomarkers. Improvement of therapeutic delivery at the tumor site via integrin binding ligands is emerging as another successful approach that may enhance both efficacy and safety of conventional therapeutics. In this review we provide an overview of recent encouraging preclinical findings, we discuss the apparent disagreement between preclinical and clinical results, and we consider new opportunities to exploit the potential of integrin adhesion complexes as targets for cancer therapy.

The development of peptide-drug conjugates (PDCs) strategies for paclitaxel

INTRODUCTION

Paclitaxel is a powerful and effective anti-tumor drug with wide clinical application. However, there are still some limitations, including poor water solubility, low specificity, and susceptibility to drug resistance. The peptide-drug conjugates (PDCs) represent a rising class of therapeutic drugs, which combines small-molecule chemotherapeutic drugs with highly flexible peptides through a cleavable or non-cleavable linker. When this strategy is applied, the therapeutic effects of paclitaxel can be improved.

AREAS COVERED

In this review, we discuss the application of the PDCs strategy in paclitaxel, including two parts: the tumor targeting peptide-paclitaxel conjugates and the cell penetrating peptide-paclitaxel conjugates.

EXPERT OPINION

Combining drugs with multifunctional peptides covalently is an effective strategy for delivering paclitaxel to tumors. Depending on different functional peptides, conjugates can increase the water solubility of paclitaxel, tumor permeability of paclitaxel, the accumulation of paclitaxel in tumor tissues, and enhance the antitumor effect of paclitaxel. In addition, due to the change of cell entry mechanism, partial conjugates can restore the therapeutic activity of paclitaxel against resistant tumors. Notably, in order to better translate into the clinical field in the future, more research should be conducted to ensure the safety and effectiveness of peptide-paclitaxel conjugates.

Selective Integrin Ligands Promote Cell Internalization of the Antineoplastic Agent Fluorouracil

Drug conjugates consisting of an antineoplastic drug and a targeting receptor ligand could be effective to overcome the heavy side effects of unselective anticancer agents. To address this need, we report here the results of a project aimed to study agonist and antagonist integrin ligands as targeting head of molecular cargoes for the selective delivery of 5-fluorouracil (5-FU) to cancer or noncancer cells. Initially, two fluorescent β-lactam-based integrin ligands were synthesized and tested for an effective and selective internalization mediated by α4β1 or α5β1 integrins in Jurkat and K562 cells, respectively. No cellular uptake was observed for both fluorescent compounds in HEK293 noncancerous control cells. Afterward, three conjugates composed of the β-lactam-based integrin ligand, suitable linkers, and 5-FU were realized. The best compound E, acting as α5β1 integrin agonist, is able to selectively deliver 5-FU into tumor cells, successfully leading to cancer cell death.