Skp1 in lung cancer: clinical significance and therapeutic efficacy of its small molecule inhibitors

Centipeda minima and 6-O-angeloylplenolin enhance the efficacy of immune checkpoint inhibitors in non-small cell lung cancer

BACKGROUND

Chemotherapeutic agents including cisplatin, gemcitabine, and pemetrexed, significantly enhance the efficacy of immune checkpoint inhibitors (ICIs) in non-small cell lung cancer (NSCLC) by increasing PD-L1 expression and potentiating T cell cytotoxicity. However, the low response rate and adverse effects limit the application of chemotherapy/ICI combinations in patients.

METHODS

We screened for medicinal herbs that could perturb PD-L1 expression and enhance T cell cytotoxicity in the presence of anti-PD-L1 antibody, and investigated the underlying mechanisms.

RESULTS

We found that the aqueous extracts of Centipeda minima (CM) significantly enhanced the cancer cell-killing activity and granzyme B expression level of CD8+ T cells, in the presence of anti-PD-L1 antibody. Both CM and its active component 6-O-angeloylplenolin (6-OAP) upregulated PD-L1 expression by suppressing GSK-3β-β-TRCP-mediated ubiquitination and degradation. CM and 6-OAP significantly enhanced ICI-induced reduction of tumor burden and prolongation of overall survival of mice bearing NSCLC cells, accompanied by upregulation of PD-L1 and increase of CD8+ T cell infiltration. CM also exhibited anti-NSCLC activity in cells and in a patient-derived xenograft mouse model.

CONCLUSIONS

These data demonstrated that the induced expression of PD-L1 and enhancement of CD8+ T cell cytotoxicity underlay the beneficial effects of 6-OAP-rich CM in NSCLCs, providing a clinically available and safe medicinal herb for combined use with ICIs to treat this deadly disease.

Identification of arnicolide C as a novel chemosensitizer to suppress mTOR/E2F1/FANCD2 axis in non-small cell lung cancer

BACKGROUND AND PURPOSE

The mammalian target of rapamycin (mTOR) pathway plays critical roles in intrinsic chemoresistance by regulating Fanconi anaemia complementation group D2 (FANCD2) expression. However, the mechanisms by which mTOR regulates FANCD2 expression and related inhibitors are not clearly elucidated. Extracts of Centipeda minima (C. minima) showed promising chemosensitizing effects by inhibiting FANCD2 activity. Here, we have aimed to identify the bioactive chemosensitizer in C. minima extracts and elucidate its underlying mechanism.

EXPERIMENTAL APPROACH

The chemosensitizing effects of arnicolide C (ArC), a bioactive compound in C. minima, on non-small cell lung cancer (NSCLC) were investigated using immunoblotting, immunofluorescence, flow cytometry, the comet assay, small interfering RNA (siRNA) transfection and animal models. The online SynergyFinder software was used to determine the synergistic effects of ArC and chemotherapeutic drugs on NSCLC cells.

KEY RESULTS

ArC had synergistic cytotoxic effects with DNA cross-linking drugs such as cisplatin and mitomycin C in NSCLC cells. ArC treatment markedly decreased FANCD2 expression in NSCLC cells, thus attenuating cisplatin-induced FANCD2 nuclear foci formation, leading to DNA damage and apoptosis. ArC inhibited the mTOR pathway and attenuated mTOR-mediated expression of E2F1, a critical transcription factor of FANCD2. Co-administration of ArC and cisplatin exerted synergistic anticancer effects in the A549 xenograft mouse model by suppressing mTOR/FANCD2 signalling in tumour tissues.

CONCLUSION AND IMPLICATIONS

ArC suppressed DNA cross-linking drug-induced DNA damage response by inhibiting the mTOR/E2F1/FANCD2 signalling axis, serving as a chemosensitizing agent. This provides insight into the anticancer mechanisms of ArC and offers a potential combinatorial anticancer therapeutic strategy.

Targeting SMAD-Dependent Signaling: Considerations in Epithelial and Mesenchymal Solid Tumors

SMADs are the canonical intracellular effector proteins of the TGF-β (transforming growth factor-β). SMADs translocate from plasma membrane receptors to the nucleus regulated by many SMAD-interacting proteins through phosphorylation and other post-translational modifications that govern their nucleocytoplasmic shuttling and subsequent transcriptional activity. The signaling pathway of TGF-β/SMAD exhibits both tumor-suppressing and tumor-promoting phenotypes in epithelial-derived solid tumors. Collectively, the pleiotropic nature of TGF-β/SMAD signaling presents significant challenges for the development of effective cancer therapies. Here, we review preclinical studies that evaluate the efficacy of inhibitors targeting major SMAD-regulating and/or -interacting proteins, particularly enzymes that may play important roles in epithelial or mesenchymal compartments within solid tumors.

YB-1 activating cascades as potential targets in KRAS-mutated tumors

Y‑box binding protein‑1 (YB-1) is a multifunctional protein that is highly expressed in human solid tumors of various entities. Several cellular processes, e.g. cell cycle progression, cancer stemness and DNA damage signaling that are involved in the response to chemoradiotherapy (CRT) are tightly governed by YB‑1. KRAS gene with about 30% mutations in all cancers, is considered the most commonly mutated oncogene in human cancers. Accumulating evidence indicates that oncogenic KRAS mediates CRT resistance. AKT and p90 ribosomal S6 kinase are downstream of KRAS and are the major kinases that stimulate YB‑1 phosphorylation. Thus, there is a close link between the KRAS mutation status and YB‑1 activity. In this review paper, we highlight the importance of the KRAS/YB‑1 cascade in the response of KRAS-mutated solid tumors to CRT. Likewise, the opportunities to interfere with this pathway to improve CRT outcome are discussed in light of the current literature.

Ceftazidime reduces cellular Skp2 to promote type-I interferon activity

Skp2 plays multiple roles in malignant tumours. Here, we revealed that Skp2 negatively regulates type-I interferon (IFN-I)-mediated antiviral activity. We first noticed that Skp2 can promote virus infection in cells. Further studies demonstrated that Skp2 interacts with IFN-I receptor 2 (IFNAR2) and promotes K48-linked polyubiquitination of IFNAR2, which accelerates the degradation of IFNAR2 proteins. Skp2-mediated downregulation of IFNAR2 levels inhibits IFN-I signalling and IFN-I-induced antiviral activity. In addition, we uncovered for the first time that the antibiotic ceftazidime can act as a repressor of Skp2. Ceftazidime reduces cellular Skp2 levels, thus enhancing IFNAR2 stability and IFN-I antiviral activity. This study reveals a new role of Skp2 in regulating IFN-I signalling and IFN-I antiviral activity and reports the antibiotic ceftazidime as a potential repressor of Skp2.

Ethanol Extract of Citrus grandis 'Tomentosa' Exerts Anticancer Effects by Targeting Skp2/p27 Pathway in Non-Small Cell Lung Cancer

SCOPE

This study aims to investigate the anticancer properties of Citrus grandis 'Tomentosa' (CGT) in non-small cell lung cancer (NSCLC).

METHODS AND RESULTS

The ethanol extract of CGT (CGTE) is prepared by using anhydrous ethanol and analyzed by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), revealing that the main chemical components in CGTE are flavonoids and coumarins, such as naringin, rhoifolin, apigenin, bergaptol, and osthole. CGTE at concentrations without inducing cell death significantly inhibits cell proliferation via inducing cell cycle G1 phase arrest by MTT, colony formation, and flow cytometry assays, implying that CGT has anticancer potential. CGTE markedly inhibits the activity of Skp2-SCF E3 ubiquitin ligase, decreases the protein level of Skp2, and promotes the accumulation of p27 by co-immunoprecipitation (co-IP) and in vivo ubiquitination assay; whereas Skp2 overexpression rescues the effects of CGTE in NSCLC cells. In subcutaneous LLC allograft and A549 xenograft mouse models, CGTE, without causing obvious side effects in mice, significantly inhibits lung tumor growth by targeting the Skp2/p27 signaling pathway.

CONCLUSION

These findings demonstrate that CGTE efficiently inhibits NSCLC proliferation both in vitro and in vivo by targeting the Skp2/p27 signaling pathway, suggesting that CGTE may serve as a therapeutic candidate for NSCLC treatment.

Promising anticancer activities and mechanisms of action of active compounds from the medicinal herb Centipeda minima (L.) A. Braun & Asch

BACKGROUND

Centipeda minima (L.) A. Braun & Asch (C. minima) has been used as a traditional Chinese herbal medicine to treat multiple diseases, including sinusitis, rhinitis, headache, and allergy. To date, the anticancer properties of C. minima have drawn considerable attention owing to the anticancer potential of C. minima extracts, the identification of active components, and the elucidation of underlying molecular mechanisms. However, the anticancer properties and significance of active components in C. minima have rarely been summarized.

PURPOSE

This review presents a comprehensive summary of the anticancer properties exhibited by active components of C. minima.

METHODS

An extensive search for published articles on the anticancer activities and active components of C. minima was performed using Web of Science, PubMed, Science Direct, and Google Scholar.

RESULTS

C. minima extracts exhibited both anticancer and chemosensitizing effects. Phytochemical studies have identified the active anticancer components of C. minima extracts. Sesquiterpene lactones, such as 6-O-angeloylplenolin (6-OAP, or brevilin A) and arnicolide D, have similar structures and anticancer mechanisms. As the most abundant sesquiterpene lactone in C. minima, 6-OAP exhibits anticancer activities mainly by targeting Skp1-Cullin1-F-box protein (SCF) E3 ubiquitin ligase and signal transducers and activators of transcription 3 (STAT3). Clinical trials have assessed the potential of 6-OAP in patients with vertex balding and alopecia areata, given its effect on JAK-STATs signaling. Chlorogenic acid, a representative organic acid in C. minima, reportedly possesses anticancer potential and inhibits tumor growth by affecting tumor microenvironment and has been approved for phase II clinical trials in patients with glioma in China.

CONCLUSION

In the present review, we highlight intriguing anticancer properties mediated by active compounds isolated from C. minima extracts, particularly sesquiterpene lactones, which might provide clues for developing novel anticancer drugs. Relevant clinical trials on chlorogenic acid and 6-OAP can promote anticancer clinical applications. Therefore, it is worth comprehensively elucidating underlying anticancer mechanisms and conducting clinical trials on C. minima and its active components.

Meta-Analysis of EGF-Stimulated Normal and Cancer Cell Lines to Discover EGF-Associated Oncogenic Signaling Pathways and Prognostic Biomarkers

BACKGROUND

Although epidermal growth factor (EGF) controls many crucial processes in the human body, it can increase the risk of developing cancer when overexpresses.

OBJECTIVES

This study focused on detecting cancer-associated genes that are dysregulated by EGF overexpression.

MATERIALS AND METHODS

To identify differentially expressed genes (DEGs), two independent meta-analyses with normal and cancer RNA-Seq samples treated by EGF were conducted. The new DEGs detected only via two meta-analyses were used in all downstream analyses. To reach count data, the tools of FastQC, Trimmomatic, HISAT2, SAMtools, and HTSeq-count were employed. DEGs in each individual RNA-Seq study and the meta-analysis of RNA-Seq studies were identified using DESeq2 and metaSeq R package, respectively. MCODE detected densely interconnected top clusters in the protein-protein interaction (PPI) network of DEGs obtained from normal and cancer datasets. The DEGs were then introduced to Enrichr and ClueGO/CluePedia, and terms, pathways, and hub genes enriched in Gene Ontology (GO) and KEGG and Reactome were detected.

RESULTS

The meta-analysis of normal and cancer datasets revealed 990 and 541 new DEGs, all upregulated. A number of DEGs were enriched in protein K48-linked deubiquitination, ncRNA processing, ribosomal large subunit binding, and protein processing in endoplasmic reticulum. Hub genes overexpression (DHX33, INTS8, NMD3, OTUD4, P4HB, RPS3A, SEC13, SKP1, USP34, USP9X, and YOD1) in tumor samples were validated by TCGA and GTEx databases. Overall survival and disease-free survival analysis also confirmed worse survival in patients with hub genes overexpression.

CONCLUSIONS

The detected hub genes could be used as cancer biomarkers when EGF overexpresses.

A small-molecule Skp1 inhibitor elicits cell death by p53-dependent mechanism

Skp1 overexpression promotes tumor growth, whereas reduced Skp1 activity is also linked with genomic instability and neoplastic transformation. This highlights the need to gain better understanding of Skp1 biology in cancer settings. To this context, potent and cellularly active small-molecule Skp1 inhibitors may be of great value. Using a hypothesis-driven, structure-guided approach, we herein identify Z0933M as a potent Skp1 inhibitor with K_D ∼0.054 μM. Z0933M occupies a hydrophobic hotspot (P1) – encompassing an aromatic cage of two phenylalanines (F101 and F139) – alongside C-terminal extension of Skp1 and, thus, hampers its ability to interact with F-box proteins, a prerequisite step to constitute intact and active SCF E3 ligase(s) complexes. In cellulo, Z0933M disrupted SCF E3 ligase(s) functioning, recapitulated previously reported effects of Skp1-reduced activity, and elicited cell death by a p53-dependent mechanism. We propose Z0933M as valuable tool for future efforts toward probing Skp1 cancer biology, with implications for cancer therapy.

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Z0933M manifests strong binding with Skp1 and inhibits Skp1-F-box PPIs

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Z0933M interacts with a P1 hotspot alongside C-terminal extension of Skp1

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Z0933M alters SCF E3 ligase functioning, leading to substrate accumulation/modulation

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Z0933M causes cell-cycle arrest, and elicits cell death by p53-dependent mechanism

Core cysteine residues in the Plasminogen-Apple-Nematode (PAN) domain are critical for HGF/c-MET signaling

The Plasminogen-Apple-Nematode (PAN) domain, with a core of four to six cysteine residues, is found in > 28,000 proteins across 959 genera. Still, its role in protein function is not fully understood. The PAN domain was initially characterized in numerous proteins, including HGF. Dysregulation of HGF-mediated signaling results in multiple deadly cancers. The binding of HGF to its cell surface receptor, c-MET, triggers all biological impacts. Here, we show that mutating four core cysteine residues in the HGF PAN domain reduces c-MET interaction, subsequent c-MET autophosphorylation, and phosphorylation of its downstream targets, perinuclear localization, cellular internalization of HGF, and its receptor, c-MET, and c-MET ubiquitination. Furthermore, transcriptional activation of HGF/c-MET signaling-related genes involved in cancer progression, invasion, metastasis, and cell survival were impaired. Thus, targeting the PAN domain of HGF may represent a mechanism for selectively regulating the binding and activation of the c-MET pathway.

A Data Science Approach for the Identification of Molecular Signatures of Aggressive Cancers

The main hallmarks of cancer include sustaining proliferative signaling and resisting cell death. We analyzed the genes of the WNT pathway and seven cross-linked pathways that may explain the differences in aggressiveness among cancer types. We divided six cancer types (liver, lung, stomach, kidney, prostate, and thyroid) into classes of high (H) and low (L) aggressiveness considering the TCGA data, and their correlations between Shannon entropy and 5-year overall survival (OS). Then, we used principal component analysis (PCA), a random forest classifier (RFC), and protein-protein interactions (PPI) to find the genes that correlated with aggressiveness. Using PCA, we found GRB2, CTNNB1, SKP1, CSNK2A1, PRKDC, HDAC1, YWHAZ, YWHAB, and PSMD2. Except for PSMD2, the RFC analysis showed a different list, which was CAD, PSMD14, APH1A, PSMD2, SHC1, TMEFF2, PSMD11, H2AFZ, PSMB5, and NOTCH1. Both methods use different algorithmic approaches and have different purposes, which explains the discrepancy between the two gene lists. The key genes of aggressiveness found by PCA were those that maximized the separation of H and L classes according to its third component, which represented 19% of the total variance. By contrast, RFC classified whether the RNA-seq of a tumor sample was of the H or L type. Interestingly, PPIs showed that the genes of PCA and RFC lists were connected neighbors in the PPI signaling network of WNT and cross-linked pathways.

6-O-angeloylplenolin inhibits anti-IgE-stimulated human mast cell activation via suppressing calcium influx and ERK phosphorylation

Objectives

Mast cells are important immune cells that primarily localize in the interface between the host and external environment, and protect us from pathogen infection. However, they are also involved in the pathology of allergic diseases such as asthma and atopic dermatitis. A novel S phase kinase-associated protein 1 (SKP1) inhibitor 6-O-angeloylplenolin (6-OAP), was studied with its potential ability to alleviate the anti-IgE-induced inflammatory responses of primary human cultured mast cells (HCMCs) and LAD2 cell line.

Materials and Methods

We isolated the HCMCs from the buffy coat of voluntary blood donors. The effects of 6-OAP on mast cell activation were evaluated by measuring degranulation, cytokine release, migration, calcium influx, and ERK phosphorylation using spectro-fluorescence assay, multiplex cytometric bead assay/ELISA, migration assay, Fluo-4 calcium flux assay, and western blot, respectively.

Results

It was found that 6-OAP exerted anti-inflammatory effects on human mast cells by dose-dependently suppressing the anti-IgE-mediated degranulation and release of cytokines such as proinflammatory cytokines (IL-8 and TNF-α), growth factors (GM-CSF, VEGF, and FGF), and chemokines (CCL2 and CCL3) in HCMC and LAD2 cells. It also suppressed the migration of immature HCMCs induced by CXCL12. Moreover, the process of calcium influx and ERK phosphorylation in activated HCMC cells were inhibited by 6-OAP administration.

Conclusion

Our results showed that 6-OAP inhibited anti-IgE-induced inflammatory responses of human mast cells via suppressing calcium influx and ERK phosphorylation.

Aberrant SKP1 Expression: Diverse Mechanisms Impacting Genome and Chromosome Stability

The S-phase Kinase-Associated Protein 1 (SKP1) is a core component of the SKP1, Cullin 1, F-box protein (SCF) complex, an E3 ubiquitin ligase that serves to poly-ubiquitinate a vast array of protein targets as a signal for their proteasomal degradation, thereby playing a critical role in the regulation of downstream biological processes. Many of the proteins regulated by SKP1 and the SCF complex normally function within pathways that are essential for maintaining genome stability, including DNA damage repair, apoptotic signaling, and centrosome dynamics. Accordingly, aberrant SKP1 and SCF complex expression and function is expected to disrupt these essential pathways, which may have pathological implications in diseases like cancer. In this review, we summarize the central role SKP1 plays in regulating essential cellular processes; we describe functional models in which SKP1 expression is altered and the corresponding impacts on genome stability; and we discuss the prevalence of SKP1 somatic copy number alterations, mutations, and altered protein expression across different cancer types, to identify a potential link between SKP1 and SCF complex dysfunction to chromosome/genome instability and cancer pathogenesis. Ultimately, understanding the role of SKP1 in driving chromosome instability will expand upon our rudimentary understanding of the key events required for genome/chromosome stability that may aid in our understanding of cancer pathogenesis, which will be critical for future studies to establish whether SKP1 may be useful as prognostic indicator or as a therapeutic target.

Brusatol has therapeutic efficacy in non-small cell lung cancer by targeting Skp1 to inhibit cancer growth and metastasis

Skp1-Cul1-F-box protein (SCF) ubiquitin E3 ligases play important roles in cancer development and serve as a promising therapeutic target in cancer therapy. Brusatol (Bru), a known Nrf2 inhibitor, holds promise for treating a wide range of tumors; however, the direct targets of Bru and its anticancer mode of action remain unclear. In our study, 793 Bru-binding candidate proteins were identified by using a biotin-brusatol conjugate (Bio-Bru) followed by streptavidin-affinity pull down-based mass spectrometry. We found that Bru can directly bind to Skp1 and disrupt the interactions of Skp1 with the F-box protein Skp2, leading to the inhibition of the Skp2-SCF E3 ligase. Bru inhibited both proliferation and migration via promoting the accumulation of the substrates p27 and E-cadherin; Skp1 overexpression attenuated while Skp1 knockdown enhanced these effects of Bru in non-small cell lung cancer (NSCLC) cells. Moreover, Bru binding to Skp1 also inhibited the β-TRCP-SCF E3 ligase. In both subcutaneous and orthotopic NSCLC xenografts, Bru significantly inhibited the growth and metastasis of NSCLC through targeting SCF complex and upregulating p27 and E-cadherin protein levels. These data demonstrate that Bru is a Skp1-targeting agent that may have therapeutic potentials in lung cancer.

6-Shogaol Inhibits Oxidative Stress-Induced Rat Vascular Smooth Muscle Cell Apoptosis by Regulating OXR1-p53 Axis

Apoptosis of vascular smooth muscle cells (VSMCs) is closely related to the pathogenesis of cardiovascular diseases, and oxidative stress is an important cause of VSMCs' death. Inhibiting VSMCs apoptosis is an effective preventive strategy in slowing down the development of cardiovascular disease, especially for atherosclerosis. In this study, we found that oxidation resistance protein 1 (OXR1), a crucial participator for responding to oxidative stress, could modulate the expression of p53, the key regulator of cell apoptosis. Our results revealed that oxidative stress promoted VSMCs apoptosis by overexpression of the OXR1-p53 axis, and 6-shogaol (6S), a major biologically active compound in ginger, could effectively attenuate cell death by preventing the upregulated expression of the OXR1-p53 axis. Quantitative proteomics analysis revealed that the degradation of p53 mediated by OXR1 might be related to the enhanced assembly of SCF ubiquitin ligase complexes, which is reported to closely relate to the modification of ubiquitination or neddylation and subsequent degradation of p53.

A Comprehensive Assessment of Genetic and Epigenetic Alterations Identifies Frequent Variations Impacting Six Prototypic SCF Complex Members

The SKP1, CUL1, F-box protein (SCF) complex represents a family of 69 E3 ubiquitin ligases that poly-ubiquitinate protein substrates marking them for proteolytic degradation via the 26S proteasome. Established SCF complex targets include transcription factors, oncoproteins and tumor suppressors that modulate cell cycle activity and mitotic fidelity. Accordingly, genetic and epigenetic alterations involving SCF complex member genes are expected to adversely impact target regulation and contribute to disease etiology. To gain novel insight into cancer pathogenesis, we determined the prevalence of genetic and epigenetic alterations in six prototypic SCF complex member genes (SKP1, CUL1, RBX1, SKP2, FBXW7 and FBXO5) from patient datasets extracted from The Cancer Genome Atlas (TCGA). Collectively, ~45% of observed SCF complex member mutations are predicted to impact complex structure and/or function in 10 solid tumor types. In addition, the distribution of encoded alterations suggest SCF complex members may exhibit either tumor suppressor or oncogenic mutational profiles in a cancer type dependent manner. Further bioinformatic analyses reveal the potential functional implications of encoded alterations arising from missense mutations by examining predicted deleterious mutations with available crystal structures. The SCF complex also exhibits frequent copy number alterations in a variety of cancer types that generally correspond with mRNA expression levels. Finally, we note that SCF complex member genes are differentially methylated across cancer types, which may effectively phenocopy gene copy number alterations. Collectively, these data show that SCF complex member genes are frequently altered at the genetic and epigenetic levels in many cancer types, which will adversely impact the normal targeting and timely destruction of protein substrates, which may contribute to the development and progression of an extensive array of cancer types.

Bioinformatics analysis identifying FBXO45 gene as a potential oncogene in esophageal cancer

BACKGROUND

F-box protein 45 (FBXO45) is a member of the F-box protein family, and is reportedly involved in the progression of many diseases. However, its role in esophageal cancer (ESCA) remains unclear.

METHODS

The expression, clinical characteristics, gene function, pathway, and correlation between the infiltration of different immune cells were analyzed using public data. The pan-cancer expression of FBXO45 was assessed using the TIMER2 database. The expression of FBXO45 in different tumor stages and histology subtypes were evaluated using the UALCAN database. The protein-protein interaction (PPI) network was constructed using the STRING database. Immune cell infiltration data were downloaded from the ImmuCellAI database.

RESULTS

The top 300 genes most positively correlated with FBXO45 were screened into the enrichment analysis. The functional enrichment results showed that FBXO45 was mainly associated with proteasomal protein catabolic process and the regulation of DNA metabolic processing in the biological process (BP) category; spindle, chromosomal region, and focal adhesion in the cellular component category; and ATPase activity and ubiquitin-protein transferase activity terms in the molecular function category. FBXO45 was overexpressed in ESCA and other cancer types. FBXO45 expression was positively associated with the infiltration levels of immunosuppressive cells, such as CD8+ (cluster of differentiation 8+) T cells and NK (natural killer cell) cells, in ESCA. MYCBP2 and SKP1 were most associated with FBXO45.

CONCLUSIONS

Our results suggested that FBXO45 is a potential oncogene in ESCA. Elevated FBXO45 expression indicates a relatively immunosuppressive microenvironment.

Establishment of high-throughput screening HTRF assay for identification small molecule inhibitors of Skp2-Cks1

S-phase kinase associated protein 2 (Skp2), a member of the F-box family that constitute the largest known class of ubiquitin E3 specificity components, is responsible for recognizing and recruiting cyclin-dependent kinase inhibitor p27 for its ubiquitination in the presence of the small accessory protein cyclin-dependent kinase regulatory subunit 1(Cks1). Skp2 is overexpressed in esophageal carcinoma tissues and closely related with tumor poor prognosis, and perturbation of the Skp2-Cks1 interaction by inhibitors or RNAi could inhibit the proliferation and metastasis of tumor cells. Therefore, inhibition of Skp2 function by small-molecule compounds targeting Skp2-Cks1 interaction is emerging as a promising and novel anti-cancer strategy. In this study, we establish an improved high-throughput screening platform to screen Skp2 inhibitors targeting Skp2-Cks1interaction, which may provide a new therapeutic approach for the clinic.

Centipeda minima extract sensitizes lung cancer cells to DNA-crosslinking agents via targeting Fanconi anemia pathway

BACKGROUND

Intrinsic and acquired chemoresistance remains a critical challenge in lung cancer chemotherapy. Fanconi anemia (FA) pathway plays an important role in antagonizing the cytotoxic effects of chemotherapeutics by repairing DNA damage. We recently demonstrated that the traditional Chinese medicinal herb, Centipeda minima (C. minima), possessed anti-inflammatory and antioxidant properties. However, the potential anticancer application of C. minima and the underlying mechanisms remain unclear.

PURPOSE

We aimed to investigate the combined anticancer effects of the ethanol extract of C. minima (ECM) and DNA-crosslinking agents on non-small cell lung cancer (NSCLC) and elucidate the underlying mechanisms.

METHODS

Cell viability and flow cytometry assay were performed to determine the synergistic cytotoxicity of ECM and DNA-crosslinking agents, cisplatin (CDDP) or mitomycin C (MMC), in NSCLC cells. Western blotting and immunofluorescence were conducted to examine the effects of ECM on protein expression in DNA damage repair pathway. Comet assay was applied to evaluate DNA damage levels. Subcutaneous xenografts of NSCLC were established to evaluate the combined anticancer effects of ECM and CDDP.

RESULTS

Combined treatments with ECM and DNA-crosslinking agents exhibited synergistic cytotoxic effects against A549 and H1299 cells. FANCD2 was highly expressed in NSCLC that correlates with poor prognosis of NSCLC patients, based on the online database analysis. ECM significantly inhibited DNA damage-induced monoubiquitination and nuclear foci formation of FANCD2, thereby sensitizing NSCLC to CDDP- or MMC-induced DNA damage and apoptosis, as evidenced by increased expression of γ-H2AX, increased cleavage of caspases-3 and PARP, and enhanced Annexin V-FITC/PI staining. Further, ECM can also decrease the protein level of FANCD2 that contributes to the chemosensitizing effects. Moreover, ECM significantly attenuated CDDP-mediated S-phase arrest by antagonizing the activation of ATR/Chk1 pathway in NSCLC cells. Animal experiments further demonstrated that ECM and CDDP combination treatment synergistically inhibited tumor growth by decreasing FANCD2 protein level in tumor tissues.

CONCLUSION

Our results demonstrated that ECM can inhibit DNA-crosslinking agents-induced activation of FA pathway by attenuating both the expression and monoubiquitination of FANCD2. ECM and CDDP combination therapy exhibited synergistic anticancer effects both in vitro and in vivo, indicating that ECM and its active components might serve as novel anticancer drugs in the combination chemotherapy.

Identification of a potential tumor suppressor gene, UBL3, in non-small cell lung cancer

Objective: Oncogenes have been shown to be drivers of non-small cell lung cancer (NSCLC), yet the tumor suppressing genes involved in lung carcinogenesis remain to be systematically investigated. This study aimed to identify tumor suppressing ubiquitin pathway genes (UPGs) that were critical to lung tumorigenesis.

Methods: The 696 UPGs were silenced by an siRNA screening in NSCLC cells; the potential tumor suppressing UPGs were analyzed, and their clinical significance was investigated.

Results: We reported that silencing of 11 UPGs resulted in enhanced proliferation of NSCLC cells, and four UPGs (UBL3, TRIM22, UBE2G2, and MARCH1) were significantly downregulated in tumor samples compared to that in normal lung tissues and their expression levels were positively associated with overall survival (OS) of NSCLC patients. Among these genes, UBL3 was the most significant one. UBL3 expression was decreased in tumor samples compared to that in paired normal lung tissues in 59/86 (68.6%) NSCLCs, was correlated with TNM stage and sex of NSCLC patients, and was significantly higher in non-smoking patients than in smoking patients. Silencing UBL3 accelerated cell proliferation and ectopic expression of UBL3 suppressed NSCLC in vitro and in vivo.

Conclusions: These results showed that UBL3 represented a tumor suppressor in NSCLC and may have potential for use in therapeutics and for the prediction of clinical outcome of patients.

Phytochemical library screening reveals betulinic acid as a novel Skp2-SCF E3 ligase inhibitor in non-small cell lung cancer

Skp2 is overexpressed in multiple cancers and plays a critical role in tumor development through ubiquitin/proteasome-dependent degradation of its substrate proteins. Drugs targeting Skp2 have exhibited promising anticancer activity. Here, we identified a plant-derived Skp2 inhibitor, betulinic acid (BA), via high-throughput structure-based virtual screening of a phytochemical library. BA significantly inhibited the proliferation and migration of non-small cell lung cancer (NSCLC) through targeting Skp2-SCF E3 ligase both in vitro and in vivo. Mechanistically, BA binding to Skp2, especially forming H-bonds with residue Lys145, decreases its stability by disrupting Skp1-Skp2 interactions, thereby inhibiting the Skp2-SCF E3 ligase and promoting the accumulation of its substrates; that is, E-cadherin and p27. In both subcutaneous and orthotopic xenografts, BA significantly inhibited the proliferation and metastasis of NSCLC through targeting Skp2-SCF E3 ligase and upregulating p27 and E-cadherin protein levels. Taken together, BA can be considered a valuable therapeutic candidate to inhibit metastasis of NSCLC.

ZC3HC1 Is a Novel Inherent Component of the Nuclear Basket, Resident in a State of Reciprocal Dependence with TPR

The nuclear basket (NB) scaffold, a fibrillar structure anchored to the nuclear pore complex (NPC), is regarded as constructed of polypeptides of the coiled-coil dominated protein TPR to which other proteins can bind without contributing to the NB's structural integrity. Here we report vertebrate protein ZC3HC1 as a novel inherent constituent of the NB, common at the nuclear envelopes (NE) of proliferating and non-dividing, terminally differentiated cells of different morphogenetic origin. Formerly described as a protein of other functions, we instead present the NB component ZC3HC1 as a protein required for enabling distinct amounts of TPR to occur NB-appended, with such ZC3HC1-dependency applying to about half the total amount of TPR at the NEs of different somatic cell types. Furthermore, pointing to an NB structure more complex than previously anticipated, we discuss how ZC3HC1 and the ZC3HC1-dependent TPR polypeptides could enlarge the NB's functional repertoire.

Pulchelloid A, a sesquiterpene lactone from the Canadian prairie plant Gaillardia aristata inhibits mitosis in human cells

BACKGROUND

The Canadian prairie ecosystem presents a rich source of natural products from plants that are subjected to herbivory by grazing mammals. This type of ecological competition may contribute to the production of natural products of interest in cell biology and medical research. We provide the first biological description of the sesquiterpene lactone, pulchelloid A, which we isolated from the prairie plant, Gaillardia aristata (Asteraceae) and report that it inhibits mitosis in human cells.

METHODS AND RESULTS

We found that G. aristata (Blanket flower) extracts were cytotoxic to human cell lines and used phenotypic assays to characterize the bioactivity of extracts. Before dying, cells were characterized by a rounded morphology, phospho-histone H3 signals, mitotic spindles, and active Cdk1. By biology-guided fractionation of Gaillardia extracts, we isolated a sesquiterpene lactone named pulchelloid A. We used immunofluorescence microscopy and observed that cells treated with pulchelloid A have phospho-histone H3 positive chromosomes and a mitotic spindle, confirming that they were in mitosis. Treated cells arrest with an unusual phenotype; they enter a prolonged mitotic arrest in which the spindles become multipolar and the chromosomes acquire histone γH2AX foci, a hallmark of damaged DNA.

CONCLUSIONS

We propose that pulchelloid A, a natural product present in the prairie plant Gaillardia aristata, delays cells in mitosis. There is a growing body of evidence that a small number of members of the sesquiterpene lactone chemical family may target proteins that regulate mitosis.

[Affinity chromatography based phosphoproteome research on lung cancer cells and its application]

磷酸化是蛋白质翻译后修饰的重要形式之一,其异常往往会导致细胞内信号通路的紊乱和疾病的发生。固定化金属离子亲和色谱(IMAC)是磷酸化肽段的高效富集技术,在磷酸化蛋白质组研究方面应用广泛。该研究以金属钛离子(Ti⁴⁺)螯合IMAC材料(Ti⁴⁺-IMAC)为载体,进行磷酸化肽段富集。比较了10 μm Ti⁴⁺-IMAC通过振荡法和固相萃取法(SPE)富集磷酸肽的效果,发现振荡法可以富集到更多的磷酸肽;对比了两种尺寸(10 μm和30 μm)Ti⁴⁺-IMAC在磷酸化肽段富集中的差异,发现小尺寸材料富集效果更佳。进一步采用优化的策略比较了不同转移能力肺癌细胞的磷酸化蛋白质组,免标记定量蛋白质组学结果表明,优化的Ti⁴⁺-IMAC方法可以从正常的肺成纤维细胞MRC5、低转移肺癌细胞95C和高转移肺癌细胞95D中分别鉴定到510、863和1108种磷酸化蛋白质,其中317种为3组所共有。该研究共鉴定到1268种磷酸化蛋白质上的7560个磷酸化位点,其中1130个为差异磷酸化位点,文献报道显示部分异常表达的激酶与癌症转移密切相关。通过生信对比分析发现,异常表达的磷酸化蛋白质主要与细胞侵袭、迁移和死亡等细胞迁移方面的功能有关。通过优化磷酸化肽富集策略,初步阐明了磷酸化蛋白质网络的异常与肺癌转移之间的相关性,该方法有望用于肺癌进展相关的磷酸化位点、磷酸化蛋白质及其信号通路研究。

Isolation of a natural product with anti-mitotic activity from a toxic Canadian prairie plant

We are investigating plants from the prairie ecological zone of Canada to identify natural products that inhibit mitosis in cancer cells. Investigation of plant parts from the Canadian plant species Hymenoxys richardsonii (Asteraceae) revealed that leaf extracts (PP-360A) had anti-mitotic activity on human cancer cell lines. Cells treated with leaf extracts acquired a rounded morphology, similar to that of cells in mitosis. We demonstrated that the rounded cells contained mitotic spindles and phospho-histone H3 using the techniques of immunofluorescence microscopy. By biology-guided fractionation of H. richardsonii leaves, we isolated a sesquiterpene lactone named hymenoratin, which had not been previously assigned a biological activity. Cells treated with hymenoratin have phospho-histone H3 positive chromosomes, a mitotic spindle, and enter a prolonged mitotic arrest in which the spindles become distorted. By Western blot analysis, hymenoratin treated cells acquire high levels of cyclin B and dephosphorylated Cdk1. There is a growing body of evidence that select members of the sesquiterpene lactone chemical family have anti-mitotic activity.

A Destiny for Degradation: Interplay between Cullin-RING E3 Ligases and Autophagy

Autophagy and the ubiquitin-proteasome system (UPS) are two major pathways for protein degradation. The cullin-RING E3 ligases (CRLs) are the largest E3 ligase family and have key biological functions in maintaining protein homeostasis. We provide an updated review of the interactions between CRLs and autophagy, focusing on the regulatory effects of CRLs on the core autophagy machinery that consists of several autophagy-related protein (ATG) complexes and their key upstream signaling pathways. The involvement of such functional interactions in health and disease is also discussed. Understanding the role of CRLs in autophagy is helpful for the development of therapeutic strategies for diseases in which CRLs and autophagy are dysregulated, such as cancer and neurodegenerative conditions.

Transcriptional Profiling Reveals the Regulatory Role of DNER in Promoting Pancreatic Neuroendocrine Neoplasms

Wnt/β-catenin and NOTCH signaling contribute to the pathogenesis and growth of (PanNENs). The wnt and Notch signaling pathways form an integrated signaling device termed "wntch" and regulate stochastic cell fate decisions, suggesting the essentiality of Wnt/Notch interactions in disease progression. However, the function of Wnt/Notch interactions in PanNENs is unclear. We analyzed RNA sequencing (RNA-seq) data to identify differentially expressed lncRNAs, mRNAs and pathways according to enriched Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways associated with PanNENs. RNA-seq analysis revealed that the levels of the lncRNA XLOC_221242 and the mRNA encoding Delta/Notch-like epidermal growth factor (EGF)-related receptor (DNER) were significantly increased in tumor tissues compared with normal tissues (n = 3). Protein-protein interaction (PPI) prediction combined with transcriptional profiling data analysis revealed that DNER expression levels were positively correlated with those of DNA-binding factor (RBPJ), S phase kinase-associated protein 1 (Skp1), CTNNB1 and Cadherin-2 (CDH2), which promote PanNEN tumorigenesis and progression. These results were consistent with those of immunohistochemical analysis of DNER, RBPJ, SKP1, CTNNB1, and CDH2 expression (n = 15). These findings provide compelling clinical and molecular evidence supporting the conclusion that DNER and the related RBPJ, SKP1, CTNNB1, and CDH2 signaling contribute to PanNEN tumorigenesis and progression by activating wnt/Notch interactions.

The functional analysis of Cullin 7 E3 ubiquitin ligases in cancer

Cullin (CUL) proteins have critical roles in development and cancer, however few studies on CUL7 have been reported due to its characteristic molecular structure. CUL7 forms a complex with the ROC1 ring finger protein, and only two F-box proteins Fbxw8 and Fbxw11 have been shown to bind to CUL7. Interestingly, CUL7 can interact with its substrates by forming a novel complex that is independent of these two F-box proteins. The biological implications of CUL-ring ligase 7 (CRL7) suggest that the CRL7 may not only perform a proteolytic function but may also play a non-proteolytic role. Among the existing studied CRL7-based E3 ligases, CUL7 exerts both tumor promotion and suppression in a context-dependent manner. Currently, the mechanism of CUL7 in cancer remains unclear, and no studies have addressed potential therapies targeting CUL7. Consistent with the roles of the various CRL7 adaptors exhibit, targeting CRL7 might be an effective strategy for cancer prevention and treatment. We systematically describe the recent major advances in understanding the role of the CUL7 E3 ligase in cancer and further summarize its potential use in clinical therapy.

Identification of Important Modules and Biomarkers in Breast Cancer Based on WGCNA

Introduction

Breast cancer (BRCA) has the highest incidence among female malignancies, and the prognosis for these patients remains poor.

Materials and Methods

In this study, core modules and central genes related to BRCA were identified through a weighted gene co-expression network analysis (WGCNA). Gene expression profiles and clinical data of GSE25066 were obtained from the Gene Expression Omnibus (GEO) database. The result was validated with RNA-seq data from The Cancer Genome Atlas (TCGA) and Oncomine database. The top 30 key module genes with the highest intramodule connectivity were selected as the core genes (R² = 0.40).

Results

According to TCGA and Oncomine datasets, seven genes were selected as candidate hub genes. Following further experimental verification, four hub genes (FAM171A1, NDFIP1, SKP1, and REEP5) were retained.

Conclusion

We identified four hub genes as candidate biomarkers for BRCA. These hub genes may provide a theoretical basis for targeted therapy against BRCA.

Synthesis and Evaluation of Novel Anticancer Compounds Derived from the Natural Product Brevilin A

Cancer is the second leading cause of death globally, responsible for an estimated 9.6 million deaths in 2018, and this burden continues to increase. Therefore, there is a clear and urgent need for novel drugs with increased efficacy for the treatment of different cancers. Previous research has demonstrated that brevilin A (BA) exerts anticancer activity in various cancers, including human multiple myeloma, breast cancer, lung cancer, and colon carcinoma, suggesting the anticancer potential present in the chemical scaffold of BA. Here, we designed and synthesized a small library of 12 novel BA derivatives and evaluated the biological anticancer effects of the compounds in various cancer cell lines. The results of this structure-activity relationship study demonstrated that BA derivatives BA-9 and BA-10 possessed significantly improved anticancer activity toward lung, colon, and breast cancer cell lines. BA-9 and BA-10 could more effectively reduce cancer cell viability and induce DNA damage, cell-cycle arrest, and apoptosis when compared with BA. Our findings represent a significant step forward in the development of novel anticancer entities.

Centipeda minima extract exerts antineuroinflammatory effects via the inhibition of NF-κB signaling pathway

BACKGROUND

Centipeda minima (L.) A.Br. (C. minima) has been used in traditional Chinese herbal medicine to treat nasal allergy, diarrhea, asthma and malaria for centuries. Recent pharmacological studies have demonstrated that the ethanol extract of C. minima (ECM) and several active components possess anti-bacterial, anti-arthritis and anti-inflammatory properties. However, the effects of ECM on neuroinflammation and the underlying mechanisms have never been reported.

PURPOSE

The study aimed to examine the potential inhibitory effects of ECM on neuroinflammation and illustrate the underlying mechanisms.

METHODS

High performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was performed to qualify the major components of ECM; BV2 and primary microglial cells were used to examine the anti-inflammatory activity of ECM in vitro. To evaluate the anti-inflammatory effects of ECM in vivo, the mice were orally administrated with ECM (100, 200 mg•kg^-1•d^-1) for 2 days before cotreatment with LPS (2 mg•kg^-1•d^-1, ip) for an additional 3 days. The mice were sacrificed the day after the last treatment and the hippocampus was dissected for further experiments. The expression of inflammatory proteins and the activation of microglia were respectively detected by real-time PCR, ELISA, Western blotting and immunofluorescence.

RESULTS

HPLC-MS/MS analysis confirmed and quantified seven chemicals in ECM. In BV2 and primary microglial cells, ECM inhibited the LPS-induced production of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β), thus protecting HT22 neuronal cells from inflammatory damage. Furthermore, ECM inhibited the LPS-induced activation of NF-κB signaling pathway and subsequently attenuated the induction of inducible nitric oxide synthase (iNOS), cyclooxygenase 2 (COX2), NADPH oxidase 2 (NOX2) and NADPH oxidase 4 (NOX4), leading to the decreased production of nitrite oxide, prostaglandin E₂ (PGE₂) and reactive oxygen species (ROS). In an LPS-induced neuroinflammatory mouse model, ECM was found to exert anti-inflammatory activity by decreasing the production of proinflammatory mediators, inhibiting the phosphorylation of NF-κB, and reducing the expression of COX2, iNOS, NOX2 and NOX4 in the hippocampal tissue. Moreover, LPS-induced microglial activation was markedly attenuated in the hippocampus, while ECM at a high dose possesses a stronger anti-inflammatory activity than the positive drug dexamethansone (DEX).

CONCLUSION

These findings demonstrate that ECM exerts antineuroinflammatory effects via attenuating the activation of NF-κB signaling pathway and inhibiting the production of proinflammatory mediators both in vitro and in vivo. C. minima might become a novel phytomedicine to treat neuroinflammatory diseases.

6-O-angeloylplenolin exerts neuroprotection against lipopolysaccharide-induced neuroinflammation in vitro and in vivo

Neuroinflammation is one of the critical events in neurodegenerative diseases, whereas microglia play an important role in the pathogenesis of neuroinflammation. In this study, we investigated the effects of a natural sesquiterpene lactone, 6-O-angeloylplenolin (6-OAP), isolated from the traditional Chinese medicine Centipeda minima (L.) A.Br., on neuroinflammation and the underlying mechanisms. We showed that treatment with lipopolysaccharide (LPS) caused activation of BV2 and primary microglial cells and development of neuroinflammation in vitro, evidenced by increased production of inflammatory cytokines TNF-α and IL-1β, the phosphorylation and nuclear translocation of NF-κB, and the transcriptional upregulation of COX-2 and iNOS, leading to increased production of proinflammatory factors NO and PGE₂. Moreover, LPS treatment induced oxidative stress through increasing the expression levels of NOX2 and NOX4. Pretreatment with 6-OAP (0.5−4 μM) dose-dependently attenuated LPS-induced NF-κB activation and oxidative stress, thus suppressed neuroinflammation in the cells. In a mouse model of LPS-induced neuroinflammation, 6-OAP (5−20 mg·kg⁻¹·d⁻¹, ip, for 7 days before LPS injection) dose-dependently inhibited the production of inflammatory cytokines, the activation of the NF-κB signaling pathway, and the expression of inflammatory enzymes in brain tissues. 6-OAP pretreatment significantly ameliorated the activation of microglia and astrocytes in the brains. 6-OAP at a high dose caused a much stronger antineuroinflammatory effect than dexamethansone (DEX). Furthermore, we demonstrated that 6-OAP pretreatment could inhibit LPS-induced neurite and synaptic loss in vitro and in vivo. In conclusion, our results demonstrate that 6-OAP exerts antineuroinflammatory effects and can be considered a novel drug candidate for the treatment of neuroinflammatory diseases.

Matcha green tea (MGT) inhibits the propagation of cancer stem cells (CSCs), by targeting mitochondrial metabolism, glycolysis and multiple cell signalling pathways

Matcha green tea (MGT) is a natural product that is currently used as a dietary supplement and may have significant anti-cancer properties. However, the molecular mechanism(s) underpinning its potential health benefits remain largely unknown. Here, we used MCF7 cells (an ER(+) human breast cancer cell line) as a model system, to systematically dissect the effects of MGT at the cellular level, via i) metabolic phenotyping and ii) unbiased proteomics analysis. Our results indicate that MGT is indeed sufficient to inhibit the propagation of breast cancer stem cells (CSCs), with an IC-50 of ~0.2 mg/ml, in tissue culture. Interestingly, metabolic phenotyping revealed that treatment with MGT is sufficient to suppress both oxidative mitochondrial metabolism (OXPHOS) and glycolytic flux, shifting cancer cells towards a more quiescent metabolic state. Unbiased label-free proteomics analysis identified the specific mitochondrial proteins and glycolytic enzymes that were down-regulated by MGT treatment. Moreover, to discover the underlying signalling pathways involved in this metabolic shift, we subjected our proteomics data sets to bio-informatics interrogation via Ingenuity Pathway Analysis (IPA) software. Our results indicate that MGT strongly affected mTOR signalling, specifically down-regulating many components of the 40S ribosome. This raises the intriguing possibility that MGT can be used as inhibitor of mTOR, instead of chemical compounds, such as rapamycin. In addition, other key pathways were affected, including the anti-oxidant response, cell cycle regulation, as well as interleukin signalling. Our results are consistent with the idea that MGT may have significant therapeutic potential, by mediating the metabolic reprogramming of cancer cells.

Brevilin A Induces Cell Cycle Arrest and Apoptosis in Nasopharyngeal Carcinoma

Nasopharyngeal carcinoma (NPC) is one of the most common malignant cancers in Southeast Asia and Southern China. Centipeda minima extract (CME) had previously demonstrated anti-cancer effects in human NPC. Brevilin A, a sesquiterpene lactone isolated from C. minima, has been reported to exhibit biological activities. In this study, we investigated its anti-NPC effect and further explored its molecular mechanisms. The effects of brevilin A were tested in the NPC cell lines CNE-1, CNE-2, SUNE-1, HONE1, and C666-1. Effects of brevilin A on cell viability were determined by MTT assay, and cell cycle and apoptosis were detected by flow cytometry. The molecular mechanism of cell cycle regulation and apoptosis were investigated via Western blot. Results showed that brevilin A inhibited NPC cell viability in a concentration- and time-dependent manner. Brevilin A induced cell cycle arrest at G2/M and induced apoptosis. Western blot results demonstrated that brevilin A could down-regulate cyclin D3, cdc2, p-PI3K, p-AKT, p-mTOR, and p-STAT3, while up-regulating cleaved PARP, cleaved caspase 9, and Bax. Regulation of cyclin B1, cdk6, and Bcl-2 expression by brevilin A showed dynamic changes according to dose and time. In the tumor xenograft model, brevilin A could reduce tumor growth, at a similar magnitude to cisplatin. However, notably, whereas cisplatin treatment led to significant weight loss in treated mice, treatment with brevilin A did not, indicating its relative lack of toxicity. Taken together, brevilin A regulated cell cycle, activated the caspase signaling pathway, and inhibited PI3K/AKT/mTOR and STAT3 signaling pathways in vitro, and exhibited similar efficacy to the common chemotherapeutic cisplatin in vivo, without its associated toxicity. These findings provide a framework for the preclinical development of brevilin A as a chemotherapeutic for NPC.

Arnicolide D, from the herb Centipeda minima, Is a Therapeutic Candidate against Nasopharyngeal Carcinoma

Nasopharyngeal carcinoma (NPC) is a high morbidity and mortality cancer with an obvious racial and geographic bias, particularly endemic to Southeast China. Our previous studies demonstrated that Centipeda minima extract (CME) exhibited anti-cancer effects in human NPC cell lines. Arnicolide C and arnicolide D are sesquiterpene lactones isolated from Centipeda minima. In this study, for the first time, we investigated their anti-NPC effects and further explored the related molecular mechanisms. The effects of both arnicolide C and arnicolide D were tested in NPC cells CNE-1, CNE-2, SUNE-1, HONE1, and C666-1. The results showed that the two compounds inhibited NPC cell viability in a concentration- and time-dependent manner. As the inhibitory effect of arnicolide D was the more pronounced of the two, our following studies focused on this compound. Arnicolide D could induce cell cycle arrest at G₂/M, and induce cell apoptosis. The molecular mechanism of cell cycle regulation and apoptosis induction was investigated, and the results showed that arnicolide D could downregulate cyclin D3, cdc2, p-PI3K, p-AKT, p-mTOR, and p-STAT3, and upregulate cleaved PARP, cleaved caspase 9, and Bax. Regulation of cyclin B1, cdk6, and Bcl-2 expression by arnicolide D showed dynamic changes according to dose and time. Taken together, arnicolide D modulated the cell cycle, activated the caspase signaling pathway, and inhibited the PI3K/AKT/mTOR and STAT3 signaling pathways. These findings provide a solid base of evidence for arnicolide D as a lead compound for further development, and act as proof for the viability of drug development from traditional Chinese medicines.

Ethanol Extract of Centipeda minima Exerts Antioxidant and Neuroprotective Effects via Activation of the Nrf2 Signaling Pathway

Oxidative stress is implicated in the pathogenesis of neurodegeneration and other aging-related diseases. Previous studies have found that the whole herb of Centipeda minima has remarkable antioxidant activities. However, there have been no reports on the neuroprotective effects of C. minima, and the underlying mechanism of its antioxidant properties is unclear. Here, we examined the underlying mechanism of the antioxidant activities of the ethanol extract of C. minima (ECM) both in vivo and in vitro and found that ECM treatment attenuated glutamate and tert-butyl hydroperoxide (tBHP)-induced neuronal death, reactive oxygen species (ROS) production, and mitochondria dysfunction. tBHP-induced phosphorylation of p38 mitogen-activated protein kinase (p38 MAPK) and c-Jun N-terminal kinases (JNK) was reduced by ECM, and ECM sustained phosphorylation level of extracellular signal regulated kinase (ERK) in SH-SY5Y and PC12 cells. Moreover, ECM induced the activation of nuclear factor erythroid 2-related factor 2 (Nrf2) and the upregulation of phase II detoxification enzymes, including heme oxygenase-1 (HO-1), superoxide dismutase-2 (SOD2), and NAD(P)H quinone oxidoreductase-1 (NQO-1) in both two cell types. In a D-galactose (D-gal) and aluminum muriate (AlCl₃)-induced neurodegenerative mouse model, administration of ECM improved the learning and memory of mice in the Morris water maze test and ameliorated the effects of neurodegenerative disorders. ECM sustained the expression level of postsynaptic density 95 (PSD95) and synaptophysin (SYN), activated the Nrf2 signaling pathway, and restored the levels of cellular antioxidants in the hippocampus of mice. In addition, four sesquiterpenoids were isolated from C. minima to identify the bioactive components responsible for the antioxidant activity of C. minima; 6-O-angeloylplenolin and arnicolide D were found to be the active compounds responsible for the activation of the Nrf2 signaling pathway and inhibition of ROS production. Our study examined the mechanism of C. minima and its active components in the amelioration of oxidative stress, which holds the promise for the treatment of neurodegenerative disease.

Aberrantly expressed genes and miRNAs in human hypopharyngeal squamous cell carcinoma based on RNA‑sequencing analysis

The aim of the present study was to investigate the key genes, miRNAs and pathways in hypopharyngeal squamous cell carcinoma (HPSCC) and to elucidate the mechanisms underlying HPSCC development. The gene and microRNA (miRNA) expression profiles of HPSCC tissues and adjacent normal tissues from three subjects were obtained. Differentially expressed genes (DEGs) and differentially expressed miRNAs were identified in HPSCC. Functional annotation and protein-protein interaction (PPI) network were conducted to elucidate the biological functions of DEGs. A total of 160 DEGs (16 upregulated and 144 downregulated genes) and 79 differentially expressed miRNAs (48 upregulated and 31 downregulated miRNAs) were identified in HPSCC. The deregulated genes were significantly involved in spliceosome, cell cycle and RNA degradation. In the PPI network, S-phase kinase associated protein 1 (SKP1), non-POU domain containing octamer binding (NONO) and zinc activated ion channel (ZACN) were identified as hub proteins. On the whole, the present study may help to gain a comprehensive understanding of tumorigenesis in HPSCC and provide valuable information for early diagnosis and drug design of HPSCC in future research.

Sesquiterpene lactone 6-O-angeloylplenolin reverses vincristine resistance by inhibiting YB-1 nuclear translocation in colon carcinoma cells

Multidrug resistance (MDR) is a major obstacle to cancer chemotherapy efficacy. In the present study, 6-O-angeloylplenolin repressed the overexpression of ATP binding cassette subfamily B member 1 (MDR1) and increasing the intracellular concentration of anticancer drugs. A reduction in P-glycoprotein expression (encoded by MDR1) was observed in parallel with a decline in mRNA expression in vincristine-resistant HCT (HCT-8/VCR) cells treated with 6-O-angeloylplenolin. In addition, 6-O-angeloylplenolin suppressed the activity of the MDR1 gene promoter. Treatment with 6-O-angeloylplenolin also decreased the amount of the specific protein complex that interacted with the MDR1 gene promoter in HCT-8/VCR cells, potentially leading to the suppression of MDR1 expression. Treatment with 6-O-angeloylplenolin inhibited the nuclear translocation of Y-box binding protein-1 in HCT-8/VCR cells treated with 6-O-angeloylplenolin, contributing to the negative regulation of MDR1. Finally, 6-O-angeloylplenolin reversed VCR resistance in an HCT/VCR xenograft model. In conclusion, 6-O-angeloylplenolin exhibited a MDR-reversing effect by downregulating MDR1 expression and could represent a novel adjuvant agent for chemotherapy.

Proteomic identification of the oncoprotein STAT3 as a target of a novel Skp1 inhibitor

The S phase kinase-associated protein 1 (Skp1), an adaptor protein of the Skp1-Cul1-F-box protein complex, binds the ubiquitin E3 ligase Skp2 and is critical to its biological functions. Targeting of Skp1 by a small compound 6-O-angeloylplenolin (6-OAP) results in dissociation and degradation of Skp2 and mitotic arrest of lung cancer cells. Here, by using a proteome microarray containing 16,368 proteins and a biotinylated 6-OAP, we identified 99 proteins that could bind 6-OAP, with Skp1 and STAT3 sitting at the central position of the 6-OAP interactome. 6-OAP formed hydrogen bonds with Ser611/Ser613/Arg609 at the SH2 domain of STAT3 and inhibited the constitutive and interleukin-6-induced phosphorylated STAT3 (pSTAT3), leading to inhibitory effects on lung cancer cells and suppression of Skp2 transcription. STAT3 was overexpressed in tumor samples compared to counterpart normal lung tissues and was inversely associated with prognosis of the patients. 6-OAP inhibited tumor growth in SCID mice intravenously injected with lung cancer cells, and downregulated both STAT3 and Skp2 in tumor samples. Given that 6-OAP is a Skp1 inhibitor, our data suggest that this compound may target Skp1 and STAT3 to suppress Skp2, augmenting its anti-lung cancer activity.

Emerging Anti-Mitotic Activities and Other Bioactivities of Sesquiterpene Compounds upon Human Cells

We review the bio-activities of natural product sesquiterpenes and present the first description of their effects upon mitosis. This type of biological effect upon cells is unexpected because sesquiterpenes are believed to inactivate proteins through Michael-type additions that cause non-specific cytotoxicity. Yet, certain types of sesquiterpenes can arrest cells in mitosis as measured by cell biology, biochemical and imaging techniques. We have listed the sesquiterpenes that arrest cells in mitosis and analyzed the biological data that support those observations. In view of the biochemical complexity of mitosis, we propose that a subset of sesquiterpenes have a unique chemical structure that can target a precise protein(s) required for mitosis. Since the process of mitotic arrest precedes that of cell death, it is possible that some sesquiterpenes that are currently classified as cytotoxic might also induce a mitotic arrest. Our analysis provides a new perspective of sesquiterpene chemical biology.

Specific targeting of the deubiquitinase and E3 ligase families with engineered ubiquitin variants

The ubiquitin proteasome system (UPS) has garnered much attention due to its potential for the development of therapeutics. Following a successful clinical application of general proteasome inhibitors much effort has been devoted to targeting individual UPS components including E3 enzymes and deubiquitinases that control specificity of ubiquitination. Our group has developed a novel approach for targeting the UPS proteins using engineered ubiquitin variants (Ubvs). These drug‐like proteins can serve as valuable tools to study biological function of UPS components and assist in the development of small molecules for clinical use. In this review, we summarize studies of Ubvs targeting members of three major families, including deubiquitinases, HECT E3 ligases, and CRL E3 ligases. In particular, we focus on Ubv binding mechanisms, structural studies, and effects on enzyme function. Furthermore, new insights gained from the Ubvs are discussed in the context of small molecule studies.

Skp1: Implications in cancer and SCF-oriented anti-cancer drug discovery

In the last decade, the ubiquitin proteasome system (UPS), in general, and E3 ubiquitin ligases, in particular, have emerged as valid drug targets for the development of novel anti-cancer therapeutics. Cullin RING Ligases (CRLs), which can be classified into eight groups (CRL1-8) and comprise approximately 200 members, represent the largest family of E3 ubiquitin ligases which facilitate the ubiquitination-derived proteasomal degradation of a myriad of functionally and structurally diverse substrates. S phase kinase-associated protein 1 (Skp1)-Cullin1-F-Box protein (SCF) complexes are the best characterized among CRLs, which play crucial roles in numerous cellular processes and physiological dysfunctions, such as in cancer biology. Currently, there is growing interest in developing SCF-targeting anti-cancer therapies for clinical application. Indeed, the research in this field has seen some progress in the form of cullin neddylation- and Skp2-inhibitors. However, it still remains an underdeveloped area and needs to design new strategies for developing improved form of therapy. In this review, we venture a novel strategy that rational pharmacological targeting of Skp1, a central regulator of SCF complexes, may provide a novel avenue for SCF-oriented anti-cancer therapy, expected: (i) to simultaneously address the critical roles that multiple SCF oncogenic complexes play in cancer biology, (ii) to selectively target cancer cells with minimal normal cell toxicity, and (iii) to offer multiple chemical series, via therapeutic interventions at the Skp1 binding interfaces in SCF complex, thereby maximizing chances of success for drug discovery. In addition, we also discuss the challenges that might be posed regarding rational pharmacological interventions against Skp1.