Proteome Analysis of Responses to Ascochlorin in a Human Osteosarcoma Cell Line by 2-D Gel Electrophoresis and MALDI-TOF MS

Filamentous Fungi-Derived Orsellinic Acid-Sesquiterpene Meroterpenoids: Fungal Sources, Chemical Structures, Bioactivities, and Biosynthesis

Fungi-derived polyketide-terpenoid hybrids are important meroterpenoid natural products that possess diverse structure scaffolds with a broad spectrum of bioactivities. Herein, we focus on an ever-increasing group of meroterpenoids, orsellinic acid-sesquiterpene hybrids comprised of biosynthetic start unit orsellinic acid coupling to a farnesyl group or/and its modified cyclic products. The review entails the search of China National Knowledge Infrastructure (CNKI), Web of Science, Science Direct, Google Scholar, and PubMed databases up to June 2022. The key terms include "orsellinic acid", "sesquiterpene", "ascochlorin", "ascofuranone", and "Ascochyta viciae", which are combined with the structures of "ascochlorin" and "ascofuranone" drawn by the Reaxys and Scifinder databases. In our search, these orsellinic acid-sesquiterpene hybrids are mainly produced by filamentous fungi. Ascochlorin was the first compound reported in 1968 and isolated from filamentous fungus Ascochyta viciae (synonym: Acremonium egyptiacum; Acremonium sclerotigenum); to date, 71 molecules are discovered from various filamentous fungi inhabiting in a variety of ecological niches. As typical representatives of the hybrid molecules, the biosynthetic pathway of ascofuranone and ascochlorin are discussed. The group of meroterpenoid hybrids exhibits a broad arrange of bioactivities, as highlighted by targeting hDHODH (human dihydroorotate dehydrogenase) inhibition, antitrypanosomal, and antimicrobial activities. This review summarizes the findings related to the structures, fungal sources, bioactivities, and their biosynthesis from 1968 to June 2022.

hnRNP L is essential for myogenic differentiation and modulates myotonic dystrophy pathologies

INTRODUCTION

RNA-binding proteins (RBPs) play an important role in skeletal muscle development and disease by regulating RNA splicing. In myotonic dystrophy type 1 (DM1), the RBP MBNL1 (muscleblind-like) is sequestered by toxic CUG repeats, leading to missplicing of MBNL1 targets. Mounting evidence from the literature has implicated other factors in the pathogenesis of DM1. Herein we sought to evaluate the functional role of the splicing factor hnRNP L in normal and DM1 muscle cells.

METHODS

Co-immunoprecipitation assays using hnRNPL and MBNL1 expression constructs and splicing profiling in normal and DM1 muscle cell lines were performed. Zebrafish morpholinos targeting hnrpl and hnrnpl2 were injected into one-cell zebrafish for developmental and muscle analysis. In human myoblasts downregulation of hnRNP L was achieved with shRNAi. Ascochlorin administration to DM1 myoblasts was performed and expression of the CUG repeats, DM1 splicing biomarkers, and hnRNP L expression levels were evaluated.

RESULTS

Using DM1 patient myoblast cell lines we observed the formation of abnormal hnRNP L nuclear foci within and outside the expanded CUG repeats, suggesting a role for this factor in DM1 pathology. We showed that the antiviral and antitumorigenic isoprenoid compound ascochlorin increased MBNL1 and hnRNP L expression levels. Drug treatment of DM1 muscle cells with ascochlorin partially rescued missplicing of established early biomarkers of DM1 and improved the defective myotube formation displayed by DM1 muscle cells.

DISCUSSION

Together, these studies revealed that hnRNP L can modulate DM1 pathologies and is a potential therapeutic target.

Patent highlights December 2019-January 2020

A snapshot of noteworthy recent developments in the patent literature of relevance to pharmaceutical and medical research and development.

HnRNPL inhibits the osteogenic differentiation of PDLCs stimulated by SrCl2 through repressing Setd2

Osteoporosis has been shown to intensify bone loss caused by periodontitis and both share common risk factors. One strategy utilized to manage the disease has been via the release of Sr ions by Strontium Ranelate having a direct effect on preventing osteoclast activation and promoting osteoblast differentiation. Previously we have developed and characterized porous Sr-mesoporous bioactive glass (Sr-MBG) scaffolds and demonstrated their ability to promote periodontal regeneration when compared to MBG alone. Our group further discovered a splicing factor, heterogeneous nuclear ribonucleoprotein L (hnRNPL), was drastically down-regulated in periodontal ligament stem cells (PDLCs) stimulated by Sr through the activation of AKT pathway. Furthermore, hnRNPL restrained the osteogenic differentiation of PDLCs through down-regulating H3K36me3-specific methyltransferase Setd2. The goal of the present study was to investigate the mechanism of periodontal regeneration stimulated by Sr It was first found that the epigenetic mechanism of splicing factor hnRNPL participated in the osteogenesis processing of PDLCs stimulated by SrCl2 . Meanwhile, the different role of hnRNPL and SET domain containing 2 (Setd2) may provide some implication of the treatment of periodontitis patients simultaneously suffering from osteoporosis.

Exploring targeted therapy of osteosarcoma using proteomics data

Despite multimodal therapeutic treatments of osteosarcoma (OS), some patients develop resistance to currently available regimens and eventually end up with recurrent or metastatic outcomes. Many attempts have been made to discover effective drugs for improving outcome; however, due to the heterogeneity of the disease, new therapeutic options have not yet been identified. This study aims to explore potential targeted therapy related to protein profiles of OS. In this review of proteomics studies, we extracted data on differentially expressed proteins (DEPs) from archived literature in PubMed and our in-house repository. The data were divided into three experimental groups, DEPs in 1) OS/OB: OS vs osteoblastic (OB) cells, 2) metastasis: metastatic vs non-metastatic sublines plus fresh tissues from primary OS with and without pulmonary metastasis, and 3) chemoresistance: spheroid (higher chemoresistance) vs monolayer cells plus fresh tissues from biopsies from good and poor responders. All up-regulated protein entities in the list of DEPs were sorted and cross-referenced with identifiers of targets of US Food and Drug Administration (FDA)-approved agents and chemical inhibitors. We found that many targets of FDA-approved antineoplastic agents, mainly a group of epigenetic regulators, kinases, and proteasomes, were highly expressed in OS cells. Additionally, some overexpressed proteins were targets of FDA-approved non-cancer drugs, including immunosuppressive and antiarrhythmic drugs. The resulting list of chemical agents showed that some transferase enzyme inhibitors might have anticancer activity. We also explored common targets of OS/OB and metastasis groups, including amidophosphoribosyltransferase (PPAT), l-lactate dehydrogenase B chain (LDHB), and pyruvate kinase M2 (PKM2) as well as the common target of all categories, cathepsin D (CTSD). This study demonstrates the benefits of a text mining approach to exploring therapeutic targets related to protein expression patterns. These results suggest possible repurposing of some FDA-approved medicines for the treatment of OS and using chemical inhibitors in drug screening tests.

Proteomics of osteosarcoma

Osteosarcoma (OS) is the most common primary malignant tumor of bone and the third most common cancer in childhood and adolescence. Nowadays, early diagnosis, drug resistance and recurrence of the disease represent the major challenges in OS treatment. Post-genomics, and in particular proteomic technologies, offer an invaluable opportunity to address the level of biological complexity expressed by OS. Although the main goal of OS oncoproteomics is focused on diagnostic and prognostic biomarker discovery, in this review we describe and discuss global protein profiling approaches to other aspects of OS biology and pathophysiology, or to investigate the mechanism of action of chemotherapeutics. In addition, we present proteomic analyses carried out on OS cell lines as in vitro models for studying osteoblastic cell biology and the attractive opportunity offered by proteomics of OS cancer stem cells.

Mass spectrometric identification of ancient proteins as potential molecular biomarkers for a 2000-year-old osteogenic sarcoma

Osteosarcoma is the most common primary malignant tumor of bone usually occurring in young adolescent and children. This disease has a poor prognosis, because of the metastases in the period of tumor progression, which are usually developed previous to the clinical diagnosis. In this paper, a 2000-year-old ancient bone remain with osteogenic sarcoma was analyzed searching for tumor biomarkers which are closely related to this disease. After a specific extraction SDS-PAGE gel electrophoresis followed by tryptic digestion was performed. After the digestion the samples were measured using MALDI TOF/TOF MS. Healthy bone samples from same archaeological site were used as control samples. Our results show that in the pathological skeletal remain several well known tumor biomarkers are detected such as annexin A10, BCL-2-like protein, calgizzarin, rho GTPase-activating protein 7, HSP beta-6 protein, transferrin and vimentin compared to the control samples. The identified protein biomarkers can be useful in the discovery of malignant bone lesions such as osteosarcoma in the very early stage of the disease from paleoanthropological remains.

Ascochlorin inhibits growth factor-induced HIF-1α activation and tumor-angiogenesis through the suppression of EGFR/ERK/p70S6K signaling pathway in human cervical carcinoma cells

Ascochlorin, a non-toxic prenylphenol compound derived from the fungus Ascochyta viciae, has been shown recently to have anti-cancer effects on various human cancer cells. However, the precise molecular mechanism of this anti-cancer activity remains to be elucidated. Here, we investigated the effects of ascochlorin on hypoxia-inducible factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF) expression in human epidermoid cervical carcinoma CaSki cells. Ascochlorin inhibited epidermal growth factor (EGF)-induced HIF-1α and VEGF expression through multiple potential mechanisms. First, ascochlorin selectively inhibited HIF-1α expression in response to EGF stimulation, but not in response to hypoxia (1% O(2)) or treatment with a transition metal (CoCl(2)). Second, ascochlorin inhibited EGF-induced ERK-1/2 activation but not AKT activation, both of which play essential roles in EGF-induced HIF-1α protein synthesis. Targeted inhibition of epidermal growth factor receptor (EGFR) expression using an EGFR-specific small interfering RNA (siRNA) diminished HIF-1α expression, which suggested that ascochlorin inhibits HIF-1α expression through suppression of EGFR activation. Finally, we showed that ascochlorin functionally abrogates in vivo tumor angiogenesis induced by EGF in a Matrigel plug assay. Our data suggest that ascochlorin inhibits EGF-mediated induction of HIF-1α expression in CaSki cells, providing a potentially new avenue of development of anti-cancer drugs that target tumor angiogenesis.

4-O-carboxymethyl ascochlorin causes ER stress and induced autophagy in human hepatocellular carcinoma cells

The synthetic derivative of ascochlorin, 4-O-carboxymethyl ascochlorin (AS-6) is an agonist of the nuclear hormone receptor PPARγ and has been shown to induce differentiation in mouse pre-adipocytes and to ameliorate type II diabetes in a murine model. AS-6 was cytotoxic when added at micromolar concentrations to cultures of three different human cancer cell lines. We used gel electrophoresis and mass spectrometry to identify proteins with altered expression in human hepatocarcinoma cells (HepG2) cells after 12 h in the presence of AS-6 and found 58 proteins that were differentially expressed. Many of the proteins showing increased expression in cells treated with AS-6 are involved in protein quality control, including glucose-regulated protein 78 (GRP78/BiP), a regulator of ER stress responses, and the transcriptional regulator CHOP, which mediates ER stress-induced apoptosis. Cells treated with AS-6 undergo an autophagic response accompanied by increased expression of beclin1, ATG5, and LC3-II and autophagosome formation marked by the appearance of large vesicles containing LC3-II. Grp78 induction was inhibited when the PPARγ antagonist, GW9662, was added together with AS-6, and autophagy and cell death were partially blocked. 3-methyl-adenine (3-MA), an inhibitor of phosphatidyl inositol 3-kinase (PI3-kinase) prevented induction of ATG5 and activation of LC3-II and blocked autophagosome formation. 3-MA also blocked induction of GRP78 and CHOP, suggesting that PI3-kinase, which is known to mediate ER stress-induced autophagy, also plays a role in initiating apoptosis in response to ER stress. Together these data establish that the cytotoxicity of AS-6 operates by a mechanism dependent on ER stress-induced autophagy and apoptosis.

Proteomic technologies for the study of osteosarcoma

Osteosarcoma is the most common primary bone cancer of children and is established during stages of rapid bone growth. The disease is a consequence of immature osteoblast differentiation, which gives way to a rapidly synthesized incompletely mineralized and disorganized bone matrix. The mechanism of osteosarcoma tumorogenesis is poorly understood, and few proteomic studies have been used to interrogate the disease thus far. Accordingly, these studies have identified proteins that have been known to be associated with other malignancies, rather than being osteosarcoma specific. In this paper, we focus on the growing list of available state-of-the-art proteomic technologies and their specific application to the discovery of novel osteosarcoma diagnostic and therapeutic targets. The current signaling markers/pathways associated with primary and metastatic osteosarcoma that have been identified by early-stage proteomic technologies thus far are also described.

Post-genomics of bone metabolic dysfunctions and neoplasias

Post-genomic research on osteoblastic and osteoclastic cells, in contrast to that on many other cell types, has only been undertaken recently. Nevertheless, important information has been gained from these investigations on the mechanisms involved in osteoblast differentiation and on markers relevant for tissue regeneration and therapeutic validation of drugs, hormones and growth factors. These protein indicators may also have a diagnostic and prognostic value for bone dysfunctions and tumors. Some reviews have already focused on the application of transcriptomics and/or proteomics for exploring skeletal biology and related disorders. The main goal of the present review is to systematically summarize the most relevant post-genomic studies on various metabolic bone diseases (osteoporosis, Paget's disease and osteonecrosis), neoplasias (osteosarcoma) and metabolic conditions that indirectly affect bone tissue, such as alkaptonuria.

Proteomics analysis of starved cells revealed Annexin A1 as an important regulator of autophagic degradation

Macroautophagy is involved in the bulk degradation of long-lived cytosolic proteins and subcellular organelles, which is important for the survival of cells during starvation. To identify potential players of the autophagy process, we subjected HCT116 cells cultured in complete medium and in Earle's balanced salt solution to proteomics analysis. In approximately 1500 protein spots detected, we characterized 52 unique proteins, whose expression levels were significantly changed following starvation. Notably, we found that Annexin A1 was significantly upregulated following starvation at both mRNA and protein levels. Inhibition of Annexin A1 expression with specific siRNA did not alter starvation-induced autophagy as measured by the level of lipidated LC3, but significantly reversed autophagy degradation as measured by the level of p62/SQSTM 1. Thus Annexin A1 seemed to be positively upregulated during starvation to promote autophagic degradation. Overall, the data presented in this study established a expression profile of the proteome in starved cells, which allowed the identification of proteins with potential significance in starvation-induced autophagy.

p53-independent induction of G1 arrest and p21WAF1/CIP1 expression by ascofuranone, an isoprenoid antibiotic, through downregulation of c-Myc

Ascofuranone has been shown to have antitumor activity, but the precise molecular mechanism by which it inhibits the proliferation of cancer cells remains unclear. Here, we study the effects of ascofuranone on cell cycle progression in human cancer cells and find that ascofuranone induces G(1) arrest without cytoxicity with upregulation of p53 and p21(WAF1/CIP1) while downregulating c-Myc and G(1) cyclins. Chromatin immunoprecipitation assay and RNA interference studies with cells deficient in p53 and p21 show that ascofuranone induces p21(WAF1/CIP1) expression and subsequent G(1) arrest through the release of p21(WAF1/CIP1) promoter from c-Myc-mediated transcriptional repression, independent of p53. Ascofuranone-induced p21(WAF1/CIP1) associates with CDK2 and prevents CDK2-cyclin E complex formation, leading to the inactivation of E2F transcriptional activity. These results suggest that ascofuranone upregulates p21(WAF1/CIP1) through p53-independent suppression of c-Myc expression, leading to cytostatic G(1) arrest. Thus, ascofuranone represents a unique natural antitumor compound that targets c-Myc independent of p53.

Comparative proteomic analysis of plasma membrane proteins between human osteosarcoma and normal osteoblastic cell lines

BACKGROUND

Osteosarcoma (OS) is the most common primary malignant tumor of bone in children and adolescents. However, the knowledge in diagnostic modalities has progressed less. To identify new biomarkers for the early diagnosis of OS as well as for potential novel therapeutic candidates, we performed a sub-cellular comparative proteomic research.

METHODS

An osteosarcoma cell line (MG-63) and human osteoblastic cells (hFOB1.19) were used as our comparative model. Plasma membrane (PM) was obtained by aqueous two-phase partition. Proteins were analyzed through iTRAQ-based quantitative differential LC/MS/MS. The location and function of differential proteins were analyzed through GO database. Protein-protein interaction was examined through String software. One of differentially expressed proteins was verified by immunohistochemistry.

RESULTS

342 non-redundant proteins were identified, 68 of which were differentially expressed with 1.5-fold difference, with 25 up-regulated and 43 down-regulated. Among those differential proteins, 69% ware plasma membrane, which are related to the biological processes of binding, cell structure, signal transduction, cell adhesion, etc., and interaction with each other. One protein--CD151 located in net nodes was verified to be over-expressed in osteosarcoma tissue by immunohistochemistry.

CONCLUSION

It is the first time to use plasma membrane proteomics for studying the OS membrane proteins according to our knowledge. We generated preliminary but comprehensive data about membrane protein of osteosarcoma. Among these, CD151 was further validated in patient samples, and this small molecule membrane might be a new target for OS research. The plasma membrane proteins identified in this study may provide new insight into osteosarcoma biology and potential diagnostic and therapeutic biomarkers.

Proteomics in bone research

Osteoporosis is prevalent among the elderly and is a major cause of bone fracture in this population. Bone integrity is maintained by the dynamic processes of bone resorption and bone formation (bone remodeling). Osteoporosis results when there is an imbalance of the two counteracting processes. Bone mineral density, measured by dual-energy x-ray absorptiometry has been the primary method to assess fracture risk for decades. Recent studies demonstrated that measurement of bone turnover markers allows for a dynamic assessment of bone remodeling, while imaging techniques, such as dual-energy x-ray absorptiometry, do not. The application of proteomics has permitted discoveries of new, sensitive, bone turnover markers, which provide unique information for clinical diagnosis and treatment of patients with bone diseases. This review summarizes the recent findings of proteomic studies on bone diseases, properties of mesenchymal stem cells with high expansion rates and osteoblast and osteoclast differentiation, with emphasis on the role of quantitative proteomics in the study of signaling dynamics, biomarkers and discovery of therapeutic targets.

KEGG spider: interpretation of genomics data in the context of the global gene metabolic network

KEGG spider is a web-based tool for interpretation of experimentally derived gene lists in order to gain understanding of metabolism variations at a genomic level. KEGG spider implements a 'pathway-free' framework that overcomes a major bottleneck of enrichment analyses: it provides global models uniting genes from different metabolic pathways. Analyzing a number of experimentally derived gene lists, we demonstrate that KEGG spider provides deeper insights into metabolism variations in comparison to existing methods.

Disialoganglioside GD3 synthase expression recruits membrane transglutaminase 2 during erythroid differentiation of the human chronic myelogenous leukemia K562 cells

By employing proteomics analysis tool, we examined the effects of GD3 synthase expression on the differentiation properties of chronic myelogenous leukemia (CML)-derived leukemia cells K562. Forced expression of GD3 synthase induced erythroid differentiation as determined by an increase in glycophorin A expression and synthesis of hemoglobins. The proteomic analysis revealed that 15 proteins were increased by GD3 synthase. In contrast, we observed three protein gel spots decreased in contents in the cell membranes of GD3 synthase-transfected K562 cells. Among the increased proteins, membrane transglutaminase 2 (TG2) was specifically increased in the cell membrane of GD3 synthase-transfected K562 cells. Then, we generated the GD3 synthase-transfected cells in the K562 cells. Interestingly, the TG2 level was increased in GD3 synthase-transfected cells compared with vector- and plasma membrane-associated ganglioside sialidase (Neu3)-transfected cells. In addition, its ability to be photoaffinity-labeled with [alpha-(32)P]GTP was also increased in the GD3 synthase- and TG2-transfected cells. Moreover, small interfering RNA (siRNA) analysis for the GD3 synthase showed the decrease or abolishment of the membrane TG2. Finally, GD3 synthase-transfected cells accelerated the erythroid differentiation. Therefore, we propose that the recruitment of TG2 into membranes by GD3 might play an important role in the erythroid differentiation in K562 cells.

Suppression of mesangial cell proliferation and extracellular matrix production in streptozotocin-induced diabetic rats by Sp1 decoy oligodeoxynucleotide in vitro and in vivo

Transcription factor Sp-1 is an important fibrogenic factor that is involved in the pathogenesis of diabetic nephropathy. In this study, we examined the effect of Sp1 decoy oligodeoxynucleotides (ODNs) on the extracellular matrix (ECM) gene expression in cultured rat mesangial cells (RMC) and streptozotocin (STZ)-induced diabetic rats. The ring-type Sp1 decoy ODNs significantly decreased ECM mRNA expression and Sp1 binding to the promoter region of these PDGF-induced genes in RMC. In addition, the decoy ODNs was introduced into the left renal artery of diabetic rat using the hemagglutinating virus of Japan (HVJ)-liposome mediated gene transfer method and effectively delivered to the kidney. On 14 days after ring-type Sp1 decoy ODNs injection, type IV collagen, fibronectin mRNA, and protein expression were markedly decreased, and the rate of urinary creatinine excretion was reduced in the ring-type Sp1 decoy ODNs-treated diabetic rats. These results indicated that the ring-type Sp1 decoy ODNs would be superior to P-Sp1 ODNs. Also, the R-Sp1 decoy ODN when introduced in vivo, effectively reduced ECM production during the progression of nephropathy. Therefore, ring-type Sp1 decoy is a promising tool for developing new therapeutic applications for progressive diabetic nephropathy.

Ascochlorin suppresses oxLDL-induced MMP-9 expression by inhibiting the MEK/ERK signaling pathway in human THP-1 macrophages

The critical initiating event in atherogenesis involves the invasion of monocytes through the endothelial walls of arteries and the transformation of monocytes from macrophages into foam cells. Human THP-1 monocytic cells can be induced to differentiate into macrophages by phorbol myristate acetate (PMA) and can then be converted into foam cells by exposure to oxidized low-density lipoprotein (oxLDL). Also, during a chronic inflammatory response, monocytes/macrophages produce the 92-kDa matrix metalloproteinase-9 (MMP-9) that may contribute to the extravasation, migration, and tissue remolding capacities of the phagocytic cells. Here, we investigate the effect of ascochlorin (ASC), a prenylphenol antiviral compound from the fungus Ascochyta viciae, on oxLDL-induced MMP-9 expression and activity in human THP-1 macrophages. ASC reduced oxLDL-induced MMP-9 expression and activity in a time-dependent and dose-dependent manner. Also, an analysis of MMP-9 activity using pharmacologic inhibitors showed that ASC inhibits MMP-9 activity via the extracellular signal-regulated kinase 1 and kinase 2 pathways. Our results suggest that ASC may be useful as a potent clinical antiatherogenic agent, a topic of considerable interest in the biological chemistry of chemotherapeutic agents.