Antitumor Effect of Anti-c-Myc Aptamer-Based PROTAC for Degradation of the c-Myc Protein.

Targeting "undruggable" targets with intrinsically disordered structures is of great significance for the treatment of disease. The transcription factor c-Myc controls global gene expression and is an attractive therapeutic target for multiple types of cancers. However, due to the lack of defined ligand binding pockets, targeted c-Myc have thus far been unsuccessful. Herein, to address the dilemma of lacking ligands, an efficient and high throughput aptamer screening strategy is established, named polystyrene microwell plate-based systematic evolution of ligands by exponential enrichment (microwell-SELEX), and identify the specific aptamer (MA9C1) against c-Myc. The multifunctional aptamer-based Proteolysis Targeting Chimeras (PROTAC) for proteolysis of the c-Myc (ProMyc) is developed using the aptamer MA9C1 as the ligand. ProMyc not only significantly degrades c-Myc by the ubiquitin-proteasome system, but also reduces the Max protein, synergistically inhibiting c-Myc transcriptional activity. Combination of the artificial cyclization and anti-PD-L1 aptamer (PA1)-based delivery system, circular PA1-ProMyc chimeras achieve tumor regression in the xenograft tumor model, laying a solid foundation for the development of efficacious c-Myc degrader for the clinic. Therefore, this aptamer-based degrader provides an invaluable potential degrader in drug discovery and anti-tumor therapy, offering a promising degrader to overcome the challenge of targeting intractable targets.

Research on the bearing behavior of single pile in self-weight collapsible loess areas.

The negative skin frictional caused by loess collapse will decrease the bearing capacity of single pile, which is essential to the design of pile foundations in loess areas. In this study, a method for estimating the subsidence of soil layer at any depth is firstly proposed based on the total self-weight collapse value. Secondly, a new load transfer constitutive model for pile-soil interface is developed, which considers the nonlinear stress-strain relationship and the ultimate shear strength of soil. Then, a load transfer calculation model for pile foundation is established, which can calculate the pile axial force, the pile skin frictional, neutral point position and the settlement of a single pile. The calculation results are compared with the test data that obtained from a pile foundation on-site immersion test and the effectiveness of the calculation method is verified well. This calculation method may be useful for designing pile foundations in collapsible loess regions.

Interactions of isoorientin and its Semi-synthetic analogs with human serum albumin.

Isoorientin is a C-glycosyl flavone with a wide range of health beneficial effects and inhibits glycogen synthase kinase 3ß (GSK-3ß) potentially against Alzheimer's disease. Its semi-synthetic derivatives have greater potency than isoorientin. The present study was aimed to determine the mechanism of interactions of isoorientin and its derivatives with human serum albumin (HSA) using multi-spectroscopic, microscale thermophoresis (MST) and computational studies. Spectra of steady-state fluorescence, UV-Vis, and time-resolved fluorescence indicated that isoorientin and its derivatives quenched the intrinsic fluorescence of HSA through a static quenching process. Isoorientin and its derivatives had a moderate affinity with HSA (Ka 7.7-14.9 × 104 M-1). The binding process was accompanied by an exothermic phenomenon, ΔG° of HSA-isoorientin and its derivatives systems were calculated as from -29.51 kJ mol-1 to -27.87 kJ mol-1. Displacement experiments with site-specific markers revealed that isoorientin and its derivatives bind to HSA at site II (subdomain IIIA) only. A reduction in the α-helical content of HSA-isoorientin and its derivatives complex was observed, because the conformational changes was structurally perturbed by the hydrophilic groups of the compounds. Further molecular modeling studies confirmed that the binding of isoorientin and its derivatives to the site II via hydrophobic interaction. The MST results confirmed the interactions between HSA and the compounds of interest. The esterase-like assay studies indicated that isoorientin and its derivatives shared the same binding site in HSA, and their induced structural changes of HSA may have been caused by partial unfolding of HSA. This work helps to understand transport, distribution, bioactivity, and design of flavonoid-based GSK-3ß inhibitors.

A CRISPR-Cas autocatalysis-driven feedback amplification network for supersensitive DNA diagnostics.

Artificial nucleic acid circuits with precisely controllable dynamic and function have shown great promise in biosensing, but their utility in molecular diagnostics is still restrained by the inability to process genomic DNA directly and moderate sensitivity. To address this limitation, we present a CRISPR-Cas-powered catalytic nucleic acid circuit, namely, CRISPR-Cas-only amplification network (CONAN), for isothermally amplified detection of genomic DNA. By integrating the stringent target recognition, helicase activity, and trans-cleavage activity of Cas12a, a Cas12a autocatalysis-driven artificial reaction network is programmed to construct a positive feedback circuit with exponential dynamic in CONAN. Consequently, CONAN achieves one-enzyme, one-step, real-time detection of genomic DNA with attomolar sensitivity. Moreover, CONAN increases the intrinsic single-base specificity of Cas12a, and enables the effective detection of hepatitis B virus infection and human bladder cancer-associated single-nucleotide mutation in clinical samples, highlighting its potential as a powerful tool for disease diagnostics.

SCF-FBXO24 regulates cell proliferation by mediating ubiquitination and degradation of PRMT6.

The protein arginine methyltransferase 6 (PRMT6) is a coregulator of gene expression by methylation of the histone H3 on arginine 2 (H3R2), H4R3 and H2AR3 [1,2]. PRMT6 is aberrantly expressed in various types of human cancer, and abnormal methylation in cancers caused by overexpression of PRMT6 is considered to correlate with poor recovery prognosis [3,4]. However, mechanisms that regulate PRMT6 protein stability in cells remain largely unknown. Here we identified that an orphan F-box protein, FBXO24, that binds to 270 to 275 amino acid residues of PRMT6 to cause polyubiquitination of lysine at position 369 of PRMT6, which mediates its degradation via the ubiquitin-proteasome pathway. Overexpression of FBXO24 or knockout of PRMT6 was found to inhibit cell proliferation, migration, and invasion in H1299 cells. PRMT6 K369R mutant became resistant to degradation. Overexpression of PRMT6 K369R caused cell cycle progression, resulting in cell proliferation. Thus, our data confirm that FBXO24 regulates cell proliferation by mediating ubiquitin-dependent proteasomal degradation of PRMT6.

Research Advances in Chemokine-like Factor Super Family Member 8.

Chemokine-like factor super family member (CMTM) is a novel generic family firstly reported by Peking University Center for Human Disease Genomics. CMTM8 is one member of this family and has exhibited tumor-inhibiting activities. It can encode proteins approaching to the transmembrane 4 superfamily. CMTM8 is down-regulated in most carcinoma cell lines and tissues. Over-expression of CMTM8 may inhibit the proliferation,migration,and invasion of carcinoma cells. However,the exact mechanism of its anti-tumor activity remains unclear. CMTM8 may be involved in various signaling pathways governing the occurrence and development of tumors. CMTM8 may be a new target in the gene therapies for tumors,while further studies on CMTM8 and its anti-tumor mechanisms are warranted.

CMTM8 inhibits the carcinogenesis and progression of bladder cancer.

Bladder cancer is the most common tumor of the urinary tract. The incidence of bladder cancer has increased in the last few decades, thus novel molecular markers for early diagnosis and more efficacious treatment are urgently needed. Chemokine­like factor (CKLF)­like MARVEL transmembrane domain containing 8 (CMTM8) is downregulated in several types of cancers and is associated with tumor progression. However, CMTM8 expression has been unexplored in bladder cancer to date. Our results revealed that the expression of CMTM8 was negative in 46 of 74 (62.2%) bladder cancer samples via immunohistochemistry assay. CMTM8 downregulation was associated with advancing tumor stage and tumor grade. CMTM8 was successfully overexpressed by lentivirus in EJ and T24 cells, and the CCK­8 and Transwell assays showed that CMTM8 overexpression decreased cell proliferation, migration and invasion in vitro. In tumor xenografts upregulation of CMTM8 inhibited tumor growth and lymph node metastasis in vivo. In conclusion, overexpression of CMTM8 in bladder cancer results in reduced malignant cell growth, migration and invasion, which could make it a potential therapeutic target in the treatment of bladder cancer.

[Tryptase of mast cells in immune organs of developing chicken embryos].

OBJECTIVE: To observe the form, distribution and emerging time of the mast cells (MCs) and tryptase positive cells (TPCs) in the immune organs of different days old chicken embryos. METHODS: The thymus, bursa of Fabricius and spleen of chicken embryos at different development time were taken and fixed in Carnoy's solution. The alcian blue/safranine O (AB/SO) and streptavidin-biotin complex (SABC) immunohistochemistry were used to observe the MCs and TPCs. RESULTS: MCs were first present in the thymus, bursa and spleen of day 13-14 embryos. The number of MCs increased along with the development days. On day 16, TPCs were first found in the immune organs. The form and distribution of TPCs were similar to MCs, but the emerging time of TPCs was later than that of MCs. CONCLUSION: Tryptase appears in the MCs in the immune organs of day 16 or later chicken embryos, and it is mainly located in the MCs of the connective tissues.