Rational design of an EGF-IL18 fusion protein: implication for developing tumor therapeutics

Proteins and their functionalization for finding therapeutic avenues in cancer: Current status and future prospective

Despite the remarkable advancement in the health care sector, cancer remains the second most fatal disease globally. The existing conventional cancer treatments primarily include chemotherapy, which has been associated with little to severe side effects, and radiotherapy, which is usually expensive. To overcome these problems, target-specific nanocarriers have been explored for delivering chemo drugs. However, recent reports on using a few proteins having anticancer activity and further use of them as drug carriers have generated tremendous attention for furthering the research towards cancer therapy. Biomolecules, especially proteins, have emerged as suitable alternatives in cancer treatment due to multiple favourable properties including biocompatibility, biodegradability, and structural flexibility for easy surface functionalization. Several in vitro and in vivo studies have reported that various proteins derived from animal, plant, and bacterial species, demonstrated strong cytotoxic and antiproliferative properties against malignant cells in native and their different structural conformations. Moreover, surface tunable properties of these proteins help to bind a range of anticancer drugs and target ligands, thus making them efficient delivery agents in cancer therapy. Here, we discuss various proteins obtained from common exogenous sources and how they transform into effective anticancer agents. We also comprehensively discuss the tumor-killing mechanisms of different dietary proteins such as bovine α-lactalbumin, hen egg-white lysozyme, and their conjugates. We also articulate how protein nanostructures can be used as carriers for delivering cancer drugs and theranostics, and strategies to be adopted for improving their in vivo delivery and targeting. We further discuss the FDA-approved protein-based anticancer formulations along with those in different phases of clinical trials.

Targeted Delivery of 111In Into the Nuclei of EGFR Overexpressing Cells via Modular Nanotransporters With Anti-EGFR Affibody

Since cell nucleus is one of the most vulnerable compartments, the maximum therapeutic effect from a variety of locally acting agents, such as photosensitizers, alfa-emitters, Auger electron emitters, will be expected when they get there. Therefore, the targeted delivery of these agents into the nuclei of target tumor cells is necessary for their anticancer effects and minimization of side effects. Modular nanotransporters (MNT) are artificial polypeptides comprising several predefined modules that recognize target cell, launching their subsequent internalization, escape from endosomes, and transport the drug load to the nucleus. This technology significantly enhances the cytotoxicity of locally acting drugs in vitro and in vivo. Epidermal growth factor receptors (EGFR) are useful molecular targets as they are overexpressed in glioblastoma, head-and-neck cancer, bladder cancer, and other malignancies. Here, we examined the possibility of using internalizable anti-EGFR affibody as an EGFR-targeting MNT module for drug transport into the cancer cell nuclei. It binds to both murine and human EGFR facilitating preclinical studies. We showed that MNT with affibody on the N-terminus (MNT_N-affibody) effectively delivered the Auger electron emitter ¹¹¹In to target cell nuclei and had pronounced cytotoxic efficacy against EGFR-overexpressing human A431 epidermoid carcinoma cells. Using EGFR-expressing human adenocarcinoma MCF-7 cells, we demonstrated that in contrast to MNT with N-terminal epidermal growth factor (EGF), MNT_N-affibody and MNT with EGF on the C-terminus did not stimulate cancer cell proliferation.

Structure optimisation to improve the delivery efficiency and cell selectivity of a tumour-targeting cell-penetrating peptide

Cell-penetrating peptide (CPP) is used for the delivery of biomacromolecules across the cell membrane and is limited in cancer therapy due to the lack of cell selectivity. Epidermal growth factor receptor (EGFR) has been widely used in clinical targeted therapy for tumours. Here, we reported a novel tumour targeting cell-penetrating peptide (TCPP), EHB (ELBD-C6H) with 20-fold and 3000-fold greater transmembrane ability and tumour cell selectivity than our previously reported S3-HBD and classic CPP TAT, respectively. In this new TCPP, a specific alpha helix structure was inserted into a repeated amino acid (AA) sequence formed by tandem multiple selected key AA residues of vaccinia growth factor (VGF), and this sequence was then fused to a tailored heparin binding domain sequence (C6H) derived from heparin-binding epidermal growth factor-like growth factor to intensify its targeting delivery ability. EHB could carry anticancer proteins such as MAP30 (Momordica Antiviral Protein 30 kDa) into EGFR-overexpressing cancer cell and inhibit cell growth, but it had a greatly reduced interaction with normal cells. These results indicated that EHB, as a novel efficient TCPP for the selective delivery of drug molecules into cancer cells, would help to improve the efficacy and safety of anti-tumour drugs.

Enhancing tumor-specific intracellular delivering efficiency of cell-penetrating peptide by fusion with a peptide targeting to EGFR

Cell-penetrating peptides (CPPs) are well known as intracellular delivery vectors. However, unsatisfactory delivery efficiency and poor specificity are challenging barriers to CPP applications at the clinical trial stage. Here, we showed that S3, an EGFR-binding domain derived from vaccinia virus growth factor, when fused to a CPP such as HBD or TAT can substantially enhance its internalization efficiency and tumor selectivity. The uptake of S3-HBD (S3H) recombinant molecule by tumor cells was nearly 80 folds increased compared to HBD alone. By contrast, the uptake of S3H by non-neoplastic cells still remained at a low level. The specific recognition between S3 and its receptor, EGFR, as well as between HBD and heparan sulfate proteoglycans on the cell surface was essential for these improvements, suggesting a syngeneic effect between the two functional domains in conjugation. This syngeneic effect is likely similar to that of the heparin-binding epidermal growth factor, which is highly abundant particularly in metastatic tumors. The process that S3H entered cells was dependent on time, dosage, and energy, via macropinocytosis pathway. With excellent cell-penetrating efficacy and a novel tumor-targeting ability, S3H appears as a promising candidate vector for targeted anti-cancer drug delivery.

GM-CSF-based fusion cytokines as ligands for immune modulation

Chromosomal translocations that combine distinct functional domains of unrelated proteins are an experiment in nature. They demonstrate how endogenous regulatory checkpoints can be overridden by altered cell biochemistry, informing a means to engineering an aberrant signal that the cell is incapable of counterregulating. Thus, our laboratory and others have synthesized fusions of GM-CSF with peptides, ILs, and chemokines, which we have termed fusokines, with the aim of inducing an enhanced immune response against cancer, aiming to overcome the maladapted biological processes causing disease. In doing so, we found that these fusokines did not behave as merely the sum of their natural unfused counterparts, but as entirely novel ligands co-opting their cognate receptor to communicate a unique message to responsive cellular targets. In this review, we discuss how fusion proteins combining different bioactive ligands can alter immune responses and briefly discuss the regulatory pathways that they circumvent.

Construction and expression of a novel bioactive IFN-alpha2b/CM4 fusion protein in Escherichia coli

Human interferon alpha2b (IFN-alpha2b) is a pleiotropic cytokine used for the treatment of various cancers. Antibacterial peptide CM4 is a small peptide that can strongly inhibit many kinds of bacteria, fungi, and tumor cells, but it does no harm to normal cells. Here, we describe a protein expression system for the production of IFN-alpha2b/CM4 fusion protein in insoluble form in Escherichia coli, coupled to an efficient dialysis refolding and histidine-tag purification protocol. The expressed IFN-alpha2b/CM4 fusion protein not only displays significantly improved antitumor activity, but also retains the antibacterial-antifungal activity of CM4.