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Fragile X mental retardation protein (FMRP), an RNA binding protein (RBP), is aberrantly hyper‐expressed in human tumors and plays an essential role in tumor invasion, metastasis and immune evasion. However, there is no small‐molecule inhibitor for FMRP so far. In this study, we developed the first FMRP‐targeting degrader based on PROteolysis TArgeting Chimera (PROTAC) technology and constructed a heterobifunctional PROTAC through linking a FMRP‐targeting G‐quadruplex RNA (sc1) to a von Hippel‐Lindau (VHL)‐targeting ligand peptide (named as sc1‐VHLL). Sc1‐VHLL specifically degraded endogenous FMRP via ubiquitination pathway in both mouse and human cancer cells. The FMRP degradation significantly changed the secretion pattern of cancer cells, resulting in higher expression of pro‐inflammatory cytokine and smaller amounts of immunomodulatory contents. Furthermore, sc1‐VHLL, when encapsulated into ionizable liposome nanoparticles (LNP), efficiently targeted tumor site and degraded FMRP in cancer cells. In CT26 tumor‐bearing mouse model, FMRP degradation within tumors substantially promoted the infiltration of lymphocytes and CD8 T cells and reduced the proportion of Treg cells, reshaping the proinflammatory tumor microenvironment and accordingly transforming cold tumor into hot tumor. When combined with immune checkpoint blockade (ICB) therapy, sc1‐VHLL based treatment remarkably inhibited the tumor growth. [ABSTRACT FROM AUTHOR]

Cell‐specific aptamers offer a powerful tool to study membrane receptors at the single‐molecule level. Most target receptors of aptamers are highly expressed on the cell surface, but difficult to analyze in situ because of dense distribution and fast velocity. Therefore, we herein propose a random sampling‐based analysis strategy termed ligand dilution analysis (LDA) for easily implemented aptamer‐based receptor study. Receptor density on the cell surface can be calculated based on a regression model. By using a synergistic ligand dilution design, colocalization and differentiation of aptamer and monoclonal antibody (mAb) binding on a single receptor can be realized. Once this is accomplished, precise binding site and detailed aptamer‐receptor binding mode can be further determined using molecular docking and molecular dynamics simulation. The ligand dilution strategy also sets the stage for an aptamer‐based dynamics analysis of two‐ and three‐dimensional motion and fluctuation of highly expressed receptors on the live cell membrane. [ABSTRACT FROM AUTHOR]

The advent of SELEX (systematic evolution of ligands by exponential enrichment) technology has shown the ability to evolve artificial ligands with affinity and specificity able to meet growing clinical demand for probes that can, for example, distinguish between the target leukemia cells and other cancer cells within the matrix of heterogeneity, which characterizes cancer cells. Though antibodies are the conventional and ideal choice as a molecular recognition tool for many applications, aptamers complement the use of antibodies due to many unique advantages, such as small size, low cost, and facile chemical modification. This Minireview will focus on the novel applications of aptamers and SELEX, as well as opportunities to develop molecular tools able to meet future clinical needs in biomedicine. [ABSTRACT FROM AUTHOR]