Isolation of cross-reacting antigen candidates by mRNA-display using a mixed cDNA library

RASAL2 Plays Inconsistent Roles in Different Cancers

RAS protein activator like 2 (RASAL2) belongs to the RAS GTPase-activating protein family and plays an important role in several cancers, including ovarian cancer, nasopharyngeal carcinoma, malignant astrocytoma, renal cell carcinoma, bladder cancer, colorectal cancer, liver cancer, triple-negative breast cancer, lung adenocarcinoma, and pancreatic ductal adenocarcinoma. Traditionally, RASAL2 has been regarded as a tumor suppressor but recent studies have found that it is an oncogene in specific types of cancer, such as colorectal cancer, liver cancer, triple-negative breast cancer, triple-negative/estrogen receptor-negative breast cancer. In this review, we summarize the latest findings regarding RASAL2 in cancers, which may be important and useful in clinical practice. We discussed the specific functions and mechanisms of RASAL2 in different kinds of cancer cells (including its inhibition of invasion, metastasis and angiogenesis and its opposite effects), which may provide new directions for cancer research and treatments. RASAL2 exhibits different relationship with clinical cancer stage, histological grade, prognosis and overall survival in different kinds of tumor. RASAL2 is a potential prognostic factor and a new therapeutic target for diagnosis and treatment.

Advantages of mRNA display selections over other selection techniques for investigation of protein-protein interactions

mRNA display is a genotype–phenotype conjugation method that allows for amplification-based, iterative rounds of in vitro selection to be applied to peptides and proteins. mRNA display can be used to display both long natural protein and short synthetic peptide libraries with unusually high diversities for the investigation of protein–protein interactions. Here, we summarize the advantages of mRNA display by comparing it with other widely used peptide or protein-selection techniques, and discuss various applications of this technique in studying protein–protein interactions.

In vitro selection of a peptide inhibitor of human IL-6 using mRNA display

Interleukin-6 (IL-6) plays a crucial role in malignant diseases, such as rheumatoid arthritis, Castleman disease, and multiple myeloma, and as such, is an attractive therapeutic target. Here, the authors isolated a novel IL-6 inhibitor peptide by in vitro selection using mRNA display. The authors first used a random-primed human cDNA library to isolate IL-6-binding peptides. After four rounds of selection, a 19-amino acid peptide named CA11 was selected and confirmed to specifically interact with IL-6. The authors then performed an alanine scan analysis of CA11 and determined the amino acid residues necessary to interact with IL-6. Next, the authors constructed a CA11-based partially randomized library and after ten more rounds of selection, isolated several groups of peptides. The most frequently occurring sequence, RA07, bound to IL-6 with 3 to 4-fold higher affinity than CA11. Furthermore, RA07 inhibited IL-6-dependent KT-3 cell proliferation in a dose-dependent manner. ELISAs revealed that RA07 could not inhibit IL-6 from binding to the IL-6 receptor (IL-6R), but could inhibit the IL-6/IL-6 complex binding to gp130.

In vitro selection of scFv and its production: an application of mRNA display and wheat embryo cell-free and E. coli cell production system

Synthetic DNA libraries encoding human antibody V(L) and V(H) fragments were designed, constructed, and enriched using mRNA display. The enriched libraries were then combined to construct a scFv library for mRNA display. Sequencing revealed that 46% of the library coded for full-length scFvs. Considering the number of molecules used in mRNA display, the size of the library displayed was calculated to be >10(10). To verify this, we tried to isolate a scFv against human RANK. A scFv was successfully isolated in the sixth round of panning and was synthesized in wheat embryo cell-free (WE) and Escherichia coli cell systems. In the WE system, even though the production level was high, the product was almost soluble. However, in the E. coli system, it was over-produced as inclusion bodies. The inclusion bodies were successfully refolded and showed approximately the same binding affinity as the WE product. These results demonstrate that using mRNA display with synthetic libraries and WE and E. coli cell production systems, a system for in vitro selection and small- to large-scale production of scFvs has been established.