Label-free target identification for natural products based on proteomics / 药学学报

Target identification and verification of natural products is an important and challenging work in the field of chemical biology. It is also an important job for researchers to apply chemical proteomics technology to biomedicine in order to identify target proteins of natural products. Target identification is critical to understanding its mechanisms and developing natural products as molecular probes and potential therapeutic drugs. Traditional approaches of small molecule target identification based on affinity have been shown to be successful, such as click-chemical probes, radioisotope labeling or photosensitized small-molecule probes. Nevertheless, these technologies require purified candidate target proteins, and modified small molecules with probes or linkers, such as adding agarose beads, biotin labels, fluorescent labeling or photo-affinity labeling. Many structure-activity relationship studies should be performed to ensure that the addition of small molecule labels undisturbed the original biological activity of the small molecules. Unfortunately, all these modifications are likely to alter their biological activity or binding specificity. To overcome the bottleneck of "target recognition", researchers have developed a series of new techniques for unmodified drug target identification. In this article, we reviewed the target identification techniques of natural product without structural modification in order to provide reference for the development of natural products.

The technologies of small molecule ligand-target protein interaction and high throughput ligand screening / 药学学报

The interaction of drug and target protein is a critical part of new drug discovery. It is the premise for drugs to exert therapeutic effects by targeting specific binding sites of target proteins and thereby affecting its pharmacological activity. Currently, a variety of techniques are exploited to detect the interaction between drug ligands and target proteins. For example, cellular thermal shift assay (CETSA) and differential scanning fluorimetry (DSF) based on thermodynamics, mass spectrometry and nuclear magnetic resonance technology, etc. In addition, high-throughput ligand screening technology provides technical convenience for the search of specific ligand, and is a powerful tool to efficiently identify the interaction between drug ligand and target protein. Here, we summarize the detection techniques of interaction between small molecules and target proteins, and discuss the application of high-throughput ligand screening technology in drug research.

Polyphyllin I promotes cell death via suppressing UPR-mediated CHOP ubiquitination and degradation in non-small cell lung cancer / 中国天然药物

Polyphyllin I (PPI) purified from Polyphyllarhizomes displays puissant cytotoxicity in many kinds of cancers. Several researches investigated its anti-cancer activity. But novel mechanisms are still worth investigation. This study aimed to explore PPI-induced endoplasmic reticulum (ER) stress as well as the underlying mechanism in non-small cell lung cancer (NSCLC). Cell viability or colony-forming was detected by MTT or crystal violet respectively. Cell cycle, apoptosis, reactive oxygen species (ROS) and mitochondrial membrane potential were assessed by flow cytometry. Gene and protein levels were evaluated by qRT-PCR and immunoblotting respectively. Protein interaction was determined by immunoprecipitation or immunofluorescence assay. Gene overexpression or silencing was carried out by transient transfection with plasmids or small interfering RNAs. The Cancer Genome Atlas (TCGA) database was used for Gene Set Enrichment Analysis (GSEA), survival analysis, gene expression statistics or pathway enrichment assay. PPI inhibited the propagation of NSCLC cells, increased non-viable apoptotic cells, arrested cell cycle at G2/M phase, induced ROS levels but failed to decrease mitochondrial membrane potential. High levels of GRP78 indicates poor prognosis in NSCLC patients. PPI selectively suppressed unfolded protein response (UPR)-induced GRP78 expression, subsequently protected CHOP from GRP78-mediated ubiquitination and degradation. We demonstrated that the natural product PPI, obtained from traditional herbal medicine, deserves for further study as a valuable candidate for lead compound in the chemotherapy of NSCLC.

Reversal of multidrug resistance by icaritin in doxorubicin-resistant human osteosarcoma cells / 中国天然药物

Multidrug resistance (MDR) is one of the major obstacles in cancer chemotherapy. Our previous study has shown that icariin could reverse MDR in MG-63 doxorubicin-resistant (MG-63/DOX) cells. It is reported that icariin is usually metabolized to icariside II and icaritin. Herein, we investigated the effects of icariin, icariside II, and icaritin (ICT) on reversing MDR in MG-63/DOX cells. Among these compounds, ICT exhibited strongest effect and showed no obvious cytotoxicity effect on both MG-63 and MG-63/DOX cells ranging from 1 to 10 μmol·L. Furthermore, ICT increased accumulation of rhodamine 123 and 6-carboxyfluorescein diacetate and enhanced DOX-induced apoptosis in MG-63/DOX cells in a dose-dependent manner. Further studies demonstrated that ICT decreased the mRNA and protein levels of multidrug resistance protein 1 (MDR1) and multidrug resistance-associated protein 1 (MRP1). We also verified that blockade of STAT3 phosphorylation was involved in the reversal effect of multidrug resistance in MG-63/DOX cells. Taken together, these results indicated that ICT may be a potential candidate in chemotherapy for osteosarcoma.

Reversal of multidrug resistance by icaritin in doxorubicin-resistant human osteosarcoma cells / 中国天然药物

Multidrug resistance (MDR) is one of the major obstacles in cancer chemotherapy. Our previous study has shown that icariin could reverse MDR in MG-63 doxorubicin-resistant (MG-63/DOX) cells. It is reported that icariin is usually metabolized to icariside II and icaritin. Herein, we investigated the effects of icariin, icariside II, and icaritin (ICT) on reversing MDR in MG-63/DOX cells. Among these compounds, ICT exhibited strongest effect and showed no obvious cytotoxicity effect on both MG-63 and MG-63/DOX cells ranging from 1 to 10 μmol·L. Furthermore, ICT increased accumulation of rhodamine 123 and 6-carboxyfluorescein diacetate and enhanced DOX-induced apoptosis in MG-63/DOX cells in a dose-dependent manner. Further studies demonstrated that ICT decreased the mRNA and protein levels of multidrug resistance protein 1 (MDR1) and multidrug resistance-associated protein 1 (MRP1). We also verified that blockade of STAT3 phosphorylation was involved in the reversal effect of multidrug resistance in MG-63/DOX cells. Taken together, these results indicated that ICT may be a potential candidate in chemotherapy for osteosarcoma.

Cis-CA1P inhibits tumor cell proliferation and prevents blood vessel formation / 中国应用生理学杂志

<p><b>OBJECTIVE</b>To investigate the effects of cis-combretastatin-A1 phosphate (cis-CA1P) on tumor cell proliferation, and its effects on the blood vessel formations.</p><p><b>METHODS</b>MTT and IC50 values were used to assess the inhibitory effects of cis-CA1P on tumor cell proliferation. Chicken embryo chorioallantoic membrane and thoracic aorta annulations isolated from rats were used to investigate the effects of cis-CAIP on the blood vessel formation.</p><p><b>RESULTS</b>Cis-CA1P concentration-dependently inhibited the proliferations of several cancer cell lines, including human gastric carcinoma cell line MGC-803, human leukemic monocyte lymphoma cell line U937, human melanoma cell line A375, human colon cancer cell line HCT116, human breast carcinoma cell line MDA-MB-231, and human leukemia cell line K562. Cis-CAIP significantly decreased the formation of blood vessels in chicken embryo chorioallantoic membrane and in thoracic aorta annulations.</p><p><b>CONCLUSION</b>Cis-CA1P inhibits cancer cell proliferation and prevents blood vessel formation.</p>