Synthesis and purification of a toxin-linked conjugate targeting epidermal growth factor receptor in Escherichia coli

Advances in antibody-based drugs and their delivery through the blood-brain barrier for targeted therapy and immunotherapy of gliomas

Gliomas are highly invasive and are the most common type of primary malignant brain tumor. The routine treatments for glioma include surgical resection, radiotherapy, and chemotherapy. However, glioma recurrence and patient survival remain unsatisfactory after employing these traditional treatment approaches. With the rapid development of molecular immunology, significant breakthroughs have been made in targeted glioma therapy and immunotherapy. Antibody-based therapy has excellent advantages in treating gliomas due to its high specificity and sensitivity. This article reviewed various targeted antibody drugs for gliomas, including anti-glioma surface marker antibodies, anti-angiogenesis antibodies, and anti-immunosuppressive signal antibodies. Notably, many antibodies have been validated clinically, such as bevacizumab, cetuximab, panitumumab, and anti-PD-1 antibodies. These antibodies can improve the targeting of glioma therapy, enhance anti-tumor immunity, reduce the proliferation and invasion of glioma, and thus prolong the survival time of patients. However, the existence of the blood-brain barrier (BBB) has caused significant difficulties in drug delivery for gliomas. Therefore, this paper also summarized drug delivery methods through the BBB, including receptor-mediated transportation, nano-based carriers, and some physical and chemical methods for drug delivery. With these exciting advancements, more antibody-based therapies will likely enter clinical practice and allow more successful control of malignant gliomas.

New ribosome-inactivating proteins and other proteins with protein synthesis-inhibiting activities

Ribosome-inactivating proteins (RIPs) consist of three varieties. Type 1 RIPs are single-chained and approximately 30-kDa in molecular weight. Type 2 RIPs are double-chained and composed of a type 1 RIP chain and a lectin chain. Type III RIPs, such as maize b-32 barley and JIP60 which are produced as single-domain proenzymes, possess an N-terminal domain corresponding to the A domain of RIPs and fused to a C-terminal domain. In addition to the aforementioned three types of RIPs originating from flowering plants, there are recently discovered proteins and peptides with ribosome-inactivating and protein synthesis inhibitory activities but which are endowed with characteristics such as molecular weights distinctive from those of the regular RIPs. These new/unusual RIPs discussed in the present review encompass metazoan RIPs from Anopheles and Culex mosquitos, antimicrobial peptides derived from RIP of the pokeweed Phytolacca dioica, maize RIP (a type III RIP derived from a precursor form), RIPs from the garden pea and the kelp. In addition, RIPs with a molecular weight smaller than those of regular type 1 RIPs are produced by plants in the Cucurbitaceae family including the bitter gourd, bottle gourd, sponge gourd, ridge gourd, wax gourd, hairy gourd, pumpkin, and Chinese cucumber. A small type II RIP from camphor tree (Cinnamomum camphora) seeds and a snake gourd type II RIP with its catalytic chain cleaved into two have been reported. RIPs produced from mushrooms including the golden needle mushroom, king tuber mushroom, straw mushroom, and puffball mushroom are also discussed in addition to a type II RIP from the mushroom Polyporus umbellatus. Bacterial (Spiroplasma) RIPs associated with the fruitfly, Shiga toxin, and Streptomyces coelicolor RIP are also dealt with. The aforementioned proteins display a diversity of molecular weights, amino acid sequences, and mechanisms of action. Some of them are endowed with exploitable antipathogenic activities.

Turning a Luffa Protein into a Self-Assembled Biodegradable Nanoplatform for Multitargeted Cancer Therapy

The peptide-derived self-assembly platform has attracted increasing attention for its great potential to develop into multitargeting nanomedicines as well as its inherent biocompatibility and biodegradability. However, their clinical application potentials are often compromised by low stability, weak membrane penetrating ability, and limited functions. Herein, inspired by a natural protein from the seeds of Luffa cylindrica, we engineered via epitope grafting and structure design a hybrid peptide-based nanoplatform, termed Lupbin, which is capable of self-assembling into a stable superstructure and concurrently targeting multiple protein-protein interactions (PPIs) located in cytoplasm and nuclei. We showed that Lupbin can efficiently penetrate cell membrane, escape from early endosome-dependent degradation, and subsequently disassemble into free monomers with wide distribution in cytosol and nucleus. Importantly, Lupbin abrogated tumor growth and metastasis through concurrent blockade of the Wnt/β-catenin signaling and reactivation of the p53 signaling, with a highly favorable in vivo biosafety profile. Our strategy expands the application of self-assembled nanomedicines into targeting intercellular PPIs, provides a potential nanoplatform with high stability for multitargeted cancer therapy, and likely reinvigorates the development of peptide-based therapeutics for the treatment of different human diseases including cancer.

Optimization of EnBase Fed-Batch Cultivation to Improve Soluble Fraction Ratio of α-Luffin Ribosome Inactivating Protein

Background

The increase of the protein expression via ribosomal manipulation is one of the suggested cellular mechanisms involved in EnBase fed-batch mode of cultivation. However, this system has not been implemented for cytotoxic proteins.

Objectives

Here, the expression pattern of α-Luffin, a ribosome inactivation protein (RIP) with an innate toxicity, was investigated in EnBase system and the effect of low temperature cultivation on the increase of α-Luffin solubility was determined.

Materials and Methods

The encoding cDNA for mature α-Luffin was synthesized and subcloned into pET28a plasmid under the control of T7 promoter. The E. coli expression yield in EnBase® Flo fed-batch system was compared with traditional batch mode at two temperatures: 25 °C and 30 °C. Sampling was performed at several time intervals and solubility of recombinant-protein was checked on SDS-PAGE in pellet and supernatant samples. The purification of recombinant protein was performed by Ni-NTA column.

Results

In fed-batch cultivation mode, the early incubation time was desirable at 30 °C whereas the maximum amount of soluble α-Luffin was achieved from the extended protein synthesis period (12 and 24h post induction) at 25 °C.

Conclusions

Our founding showed that EnBase had a greater efficacy in producing higher soluble protein ratios compared to batch cultivation growth rate, however for cytotoxic proteins, incubation temperature and time need to be optimized. Owing to the advantages of natural toxins from RIP family for producing anticancer immune-conjugates, well optimization of this protein expression is of importance regarding industrial aspects. The optimized condition proposed here is promising in terms of large scale soluble production of α-Luffin without the need for refolding.

Cloning and soluble expression of mature α-luffin from Luffa cylindrica in E. coli using SUMO fusion protein

α-Lufin, found in Luaf cylindrica seeds, is a type I ribosome inactivating proteins. Cytotoxic effects make it an appropriate candidate for the construction of immunotoxins and conjugates. Because of limited natural resources, recombinant technology is the best approach to achieve large-scale production of plant-based proteins. In the present study, α-lufin protein was expressed in E. coli and the effects of different temperature conditions, SUMO fusion tag, and cultivation strategies on total expression and solubility were investigated. Protein expression was evaluated at different intervals (0, 4, 6, 8, 24 h) postinduction. Our results showed that EnBase had higher eficiency than LB, and maximum solubility and total protein expression were achieved 24 h after induction at 30 °C and 25 °C, respectively. It was shown that SUMO tag is an effective strategy to improve protein solubility.

Recombinant Immunotoxin Therapy of Glioblastoma: Smart Design, Key Findings, and Specific Challenges

Recombinant immunotoxins (RITs) refer to a group of recombinant protein-based therapeutics, which consists of two components: an antibody variable fragment or a specific ligand that allows RITs to bind specifically to target cells and an engineered toxin fragment that kills the target cells upon internalization. To date, over 1,000 RITs have been generated and significant success has been achieved in the therapy of hematological malignancies. However, the immunogenicity and off-target toxicities of RITs remain as significant barriers for their application to solid tumor therapy. A group of RITs have also been generated for the treatment of glioblastoma multiforme, and some have demonstrated evidence of tumor response and an acceptable profile of toxicity and safety in early clinical trials. Different from other solid tumors, how to efficiently deliver the RITs to intracranial tumors is more critical and needs to be solved urgently. In this article, we first review the design and expression of RITs, then summarize the key findings in the preclinical and clinical development of RIT therapy of glioblastoma multiforme, and lastly discuss the specific issues that still remain to forward RIT therapy to clinical practice.