Inhibition of Plk1 and Pin1 by 5'-nitro-indirubinoxime suppresses human lung cancer cells

RPL27 contributes to colorectal cancer proliferation and stemness via PLK1 signaling

Although expression of ribosomal protein L27 (RPL27) is upregulated in clinical colorectal cancer (CRC) tissue, to the best of our knowledge, the oncogenic role of RPL27 has not yet been defined. The present study aimed to investigate whether targeting RPL27 could alter CRC progression and determine whether RPL27 gains an extra‑ribosomal function during CRC development. Human CRC cell lines HCT116 and HT29 were transfected with RPL27‑specific small interfering RNA and proliferation was assessed in vitro and in vivo using proliferation assays, fluorescence‑activated cell sorting (FACS) and a xenograft mouse model. Furthermore, RNA sequencing, bioinformatic analysis and western blotting were conducted to explore the underlying mechanisms responsible for RPL27 silencing‑induced CRC phenotypical changes. Inhibiting RPL27 expression suppressed CRC cell proliferation and cell cycle progression and induced apoptotic cell death. Targeting RPL27 significantly inhibited growth of human CRC xenografts in nude mice. Notably, polo‑like kinase 1 (PLK1), which serves an important role in mitotic cell cycle progression and stemness, was downregulated in both HCT116 and HT29 cells following RPL27 silencing. RPL27 silencing reduced the levels of PLK1 protein and G2/M‑associated regulators such as phosphorylated cell division cycle 25C, CDK1 and cyclin B1. Silencing of RPL27 reduced the migration and invasion abilities and sphere‑forming capacity of the parental CRC cell population. In terms of phenotypical changes in cancer stem cells (CSCs), RPL27 silencing suppressed the sphere‑forming capacity of the isolated CD133+ CSC population, which was accompanied by decreased CD133 and PLK1 levels. Taken together, these findings indicated that RPL27 contributed to the promotion of CRC proliferation and stemness via PLK1 signaling and RPL27 may be a useful target in a next‑generation therapeutic strategy for both primary CRC treatment and metastasis prevention.

Small molecules targeting Pin1 as potent anticancer drugs

Background: Pin1 is a member of the evolutionarily conserved peptidyl-prolyl isomerase (PPIase) family of proteins. Following phosphorylation, Pin1-catalyzed prolyl-isomerization induces conformational changes, which serve to regulate the function of many phosphorylated proteins that play important roles during oncogenesis. Thus, the inhibition of Pin1 provides a unique means of disrupting oncogenic pathways and therefore represents an appealing target for novel anticancer therapies.

Methods: As Pin1 is conserved between yeast and humans, we employed budding yeast to establish a high-throughput screening method for the primary screening of Pin1 inhibitors. This effort culminated in the identification of the compounds HWH8-33 and HWH8-36. Multifaceted approaches were taken to determine the inhibition profiles of these compounds against Pin1 activity in vitro and in vivo, including an isomerization assay, surface plasmon resonance (SPR) technology, virtual docking, MTT proliferation assay, western blotting, cell cycle analysis, apoptosis analysis, immunofluorescence analysis, wound healing, migration assay, and nude mouse assay.

Results:In vitro, HWH8-33 and HWH8-36 could bind to purified Pin1 and inhibited its enzyme activity; showed inhibitory effects on cancer cell proliferation; led to G2/M phase arrest, dysregulated downstream protein expression, and apoptosis; and suppressed cancer cell migration. In vivo, HWH8-33 suppressed tumor growth in the xenograft mice after oral administration for 4 weeks, with no noticeable toxicity. Together, these results show the anticancer activity of HWH8-33 and HWH8-36 against Pin1 for the first time.

Conclusion: In summary, we identified two hit compounds HWH8-33 and HWH8-36, which after further structure optimization have the potential to be developed as antitumor drugs.

The regulatory role of Pin1 in neuronal death

Regulated cell death predominantly involves apoptosis, autophagy, and regulated necrosis. It is vital that we understand how key regulatory signals can control the process of cell death. Pin1 is a cis-trans isomerase that catalyzes the isomerization of phosphorylated serine or threonine-proline motifs of a protein, thereby acting as a crucial molecular switch and regulating the protein functionality and the signaling pathways involved. However, we know very little about how Pin1-associated pathways might play a role in regulated cell death. In this paper, we review the role of Pin1 in regulated cell death and related research progress and summarize Pin1-related pathways in regulated cell death. Aside from the involvement of Pin1 in the apoptosis that accompanies neurodegenerative diseases, accumulating evidence suggests that Pin1 also plays a role in regulated necrosis and autophagy, thereby exhibiting distinct effects, including both neurotoxic and neuroprotective effects. Gaining an enhanced understanding of Pin1 in neuronal death may provide us with new options for the development of therapeutic target for neurodegenerative disorders.

Anticancer potential of indirubins in medicinal chemistry: Biological activity, structural modification, and structure-activity relationship

Indirubin is the crucial ingredient of Danggui Longhui Wan and Qing-Dai, traditional Chinese medicine herbal formulas used for the therapy of chronic myelocytic leukemia in China for hundreds of years. Although the monomeric indirubin has been used in China for the treatment human chronic myelocytic leukemia. However, due to low water solubility, poor pharmacokinetic properties and low therapeutic effects are the major obstacle, and had significantly limited its clinical application. Consequently, the attractive anticancer profile of indirubin has enthused numerous researchers to discover novel indirubin derivatives with improved pharmacodynamic activity as well as good pharmacokinetic property. In this paper, we comprehensively review the recent progress of anticancer potential of indirubins, structural modification and structure-activity relationship, which may provide useful direction for the further development of novel indirubins with improved pharmacological profiles for the treatment of various types of cancer.

[Research on Analysis of Final Diagnosis and Prognostic Factors, and Development of New Therapeutic Drugs for Malignant Tumors (Especially Malignant Pediatric Tumors)]

Outcomes of treatment for malignant pediatric tumors including leukemia are improving by conventional multimodal treatment with strong chemotherapy, surgical resection, radiotherapy, and bone marrow transplantation. However, patients with advanced neuroblastoma, metastatic Ewing's sarcoma family of tumor (ESFT), and metastatic osteosarcoma continue to have an extremely poor prognosis. Therefore novel therapeutic strategies are urgently needed to improve their survival. Apoptotic cell death is a key mechanism for normal cellular homeostasis. Intact apoptotic mechanisms are pivotal for embryonic development, tissue remodeling, immune regulation, and tumor regression. Genetic aberrations disrupting programmed cell death often underpin tumorigenesis and drug resistance. Moreover, it has been suggested that apoptosis or cell differentiation proceeds to spontaneous regression in early stage neuroblastoma. Therefore apoptosis or cell differentiation is a critical event in this cancer. We extracted many compounds from natural plants (Angelica keiskei, Alpinia officiarum, Lycaria puchury-major, Brassica rapa) or synthesized cyclophane pyridine, indirubin derivatives, vitamin K3 derivatives, burchellin derivatives, and GANT61, and examined their effects on apoptosis, cell differentiation, and cell cycle in neuroblastoma and ESFT cell lines compared with normal cells. Some compounds were very effective against these tumor cells. These results suggest that they may be applicable as an efficacious and safe drug for the treatment of malignant pediatric tumors.

PLK1 promotes proliferation and suppresses apoptosis of renal cell carcinoma cells by phosphorylating MCM3

Minichromosome maintenance 3 (MCM3) protein has been widely studied due to its essential role in DNA replication. In addition, it is overexpressed in several human tumor types. However, the role of this protein in renal cell carcinoma (RCC) is not widely known. In this study, we demonstrated that polo-like kinase 1 (PLK1)-mediated MCM3 phosphorylation regulates proliferation and apoptosis in RCC. Our results confirm that PLK1 and phospho-MCM3 (p-MCM3) are highly expressed in renal cell carcinoma. The expression of PLK1 is closely related to the clinical characteristics of renal cell carcinoma. They play important roles in the proliferation and apoptosis of RCC. In vitro, after overexpression of PLK1 or MCM3, the proliferation of RCC cells was significantly enhanced and cell apoptosis was inhibited, while after knockout, the proliferation of RCC cells was weakened and cell apoptosis was promoted. In addition, Mn2+-Phos-tag SDS-PAGE, western blotting, and immunofluorescence were utilized to determine that MCM3 is a physiological substrate of PLK1, which is phosphorylated on serine 112 (Ser112) in a PLK1-dependent manner. PLK1-mediated MCM3 phosphorylation promotes RCC cell cycle proliferation and suppresses apoptosis in vitro. Moreover, we found that PLK1-mediated MCM3 phosphorylation induced cellular proliferation and decreased apoptosis, as well as tumor growth in mice. Overall, we conclude that PLK1-mediated MCM3 phosphorylation is a novel mechanism to regulate RCC proliferation and apoptosis.

Targeting PIN1 as a Therapeutic Approach for Hepatocellular Carcinoma

PIN1 is a peptidyl-prolyl cis/trans isomerase that specifically binds and catalyzes the cis/trans isomerization of the phosphorylated serine or threonine residue preceding a proline (pSer/Thr-Pro) motif of its interacting proteins. Through this phosphorylation-dependent prolyl isomerization, PIN1 is involved in the regulation of various important cellular processes including cell cycle progression, cell proliferation, apoptosis and microRNAs biogenesis; hence its dysregulation contributes to malignant transformation. PIN1 is highly expressed in hepatocellular carcinoma (HCC). By fine-tuning the functions of its interacting proteins such as cyclin D1, x-protein of hepatitis B virus and exportin 5, PIN1 plays an important role in hepatocarcinogenesis. Growing evidence supports that targeting PIN1 is a potential therapeutic approach for HCC by inhibiting cell proliferation, inducing cellular apoptosis, and restoring microRNAs biogenesis. Novel formulation of PIN1 inhibitors that increases in vivo bioavailability of PIN1 inhibitors represents a promising future direction for the therapeutic strategy of HCC treatment. In this review, the mechanisms underlying PIN1 over-expression in HCC are explored. Furthermore, we also discuss the roles of PIN1 in HCC tumorigenesis and metastasis through its interaction with various phosphoproteins. Finally, recent progress in the therapeutic options targeting PIN1 for HCC treatment is examined and summarized.

Anti-Proliferation Activity of a Decapeptide from Perinereies aibuhitensis toward Human Lung Cancer H1299 Cells

Perinereis aibuhitensis peptide (PAP) is a decapeptide (Ile-Glu-Pro-Gly-Thr-Val-Gly-Met-Met-Phe, IEPGTVGMMF) with anticancer activity that was purified from an enzymatic hydrolysate of Perinereis aibuhitensis. In the present study, the anticancer effect of PAP on H1299 cell proliferation was investigated. Our results showed that PAP promoted apoptosis and inhibited the proliferation of H1299 cells in a time- and dose-dependent manner. When the PAP concentration reached 0.92 mM, more than 95% of treated cells died after 72 h of treatment. Changes in cell morphology were further analyzed using an inverted microscope and AO/EB staining and flow cytometry was adopted for detecting apoptosis and cell cycle phase. The results showed that the early and late apoptosis rates of H1299 cells increased significantly after treatment with PAP and the total apoptosis rate was significantly higher than that of the control group. Moreover, after treatment with PAP, the number of cells in the S phase of cells was significantly reduced and the ability for the cells to proliferate was also reduced. H1299 cells were arrested in the G2/M phase and cell cycle progression was inhibited. Furthermore, the results of western blotting showed that nm23-H1 and vascular endothelial growth factor (VEGF) protein levels decreased in a dose-dependent manner, while the pro-apoptotic protein and anti-apoptotic protein ratios and the level of apoptosis-related caspase protein increased in a dose-dependent manner. In conclusion, our results indicated that PAP, as a natural marine bioactive substance, inhibited proliferation and induced apoptosis of human lung cancer H1299 cells. PAP is likely to be exploited as the functional food or adjuvant that may be used for prevention or treatment of human non-small cell lung cancer in the future.

miR-190, CDK1, MCM10 and NDC80 predict the prognosis of the patients with lung cancer

Lung cancer (LC), which includes small-cell lung carcinoma (SCLC) and non-small-cell lung carcinoma (NSCLC), is common and has a high fatality rate. This study aimed to reveal the prognostic mechanisms of LC. GSE30219 was extracted from the Gene Expression Omnibus (GEO) database, and included 293 LC samples and 14 normal lung samples. Differentially expressed genes (DEGs) were identified using the Limma package, and subjected to pathway enrichment analysis using DAVID. MicroRNAs (miRNAs) targeting the DEGs were predicted using Webgestalt. Cytoscape software was used to build a protein-protein interaction (PPI) network and to identify significant network modules. Survival analysis was conducted using Survminer and Survival packages, and validation was performed using The Cancer Genome Atlas (TCGA) dataset. The good and poor prognosis groups contained 518 DEGs. miR-190, miR-493, and miR-218 for the upregulated genes and miR-302, miR-200, and miR-26 for the downregulated genes were predicted. Three network modules (module 1, 2, and 3) were identified from the PPI network. CDK1, MCM10, and NDC80 were the core nodes of module 1, 2, and 3, respectively. In module 1, CDK1 interacted with both CCNB1 and CCNB2. Additionally, CDK1, CCNB1, CCNB2, MCM10, and NDC80 expression levels correlated with clinical survival and were identified as DEGs in both GSE30219 and the TCGA dataset. miR-190, miR-493, miR-218, miR-200, and miR-302 might act in LC by targeting the DEGs. CDK1, CCNB1, CCNB2, MCM10, and NDC80 might also influence the prognosis of LC.

Knockdown of the prolyl isomerase Pin1 inhibits Hep-2 cell growth, migration, and invasion by targeting the β-catenin signaling pathway

There is increasing evidence indicating that peptidylprolyl cis/trans isomerase, NIMA-interacting 1 (Pin1) plays a decisive role in a variety of cancers. Nevertheless, its function in laryngeal squamous cell carcinoma (LSCC) has not been elaborated. The aim of this study is to determine the role of Pin1 in LSCC. Here, we established stably transfected Hep-2 cells with low expression of Pin1. Intriguingly, cell proliferation, migration, and invasion was significantly inhibited in Pin1-silenced Hep-2 cells. Similarly, knockdown of Pin1 induced apoptosis of Hep-2 cells, as evidenced by increased expression of cleaved-caspase-3, cleaved-PARP, and bax, and decreased expression of bcl2. We also demonstrated that silencing of Pin1 down-regulated β-catenin and cyclin D1 expression. Inversely, over-expression of β-catenin reversed the inhibiting effect of Pin1 silencing on Hep-2 cells. Moreover, we proved that knockdown of Pin1 inhibited tumorigenesis of Hep-2 cells in vivo. Taken together, we demonstrate that silencing of Pin1 effectively suppresses the growth of Hep-2 cells through β-catenin, indicating that Pin1 possess the potential to serve as a therapeutic target for the treatment of LSCC.

PIN1 in Cell Cycle Control and Cancer

Cell cycle progression is tightly controlled by many cell cycle-regulatory proteins that are in turn regulated by a family of cyclin-dependent kinases (CDKs) through protein phosphorylation. The peptidyl-prolyl cis/trans isomerase PIN1 provides a further post-phosphorylation modification and functional regulation of these CDK-phosphorylated proteins. PIN1 specifically binds the phosphorylated serine or threonine residue preceding a proline (pSer/Thr-Pro) motif of its target proteins and catalyzes the cis/trans isomerization on the pSer/Thr-Pro peptide bonds. Through this phosphorylation-dependent prolyl isomerization, PIN1 fine-tunes the functions of various cell cycle-regulatory proteins including retinoblastoma protein (Rb), cyclin D1, cyclin E, p27, Cdc25C, and Wee1. In this review, we discussed the essential roles of PIN1 in regulating cell cycle progression through modulating the functions of these cell cycle-regulatory proteins. Furthermore, the mechanisms underlying PIN1 overexpression in cancers were also explored. Finally, we examined and summarized the therapeutic potential of PIN1 inhibitors in cancer therapy.

Downregulation of microRNA-370 in esophageal squamous-cell carcinoma is associated with cancer progression and promotes cancer cell proliferation via upregulating PIN1

PIN1 is a peptidyl-prolyl cis/trans isomerase (PPIase) that controls cell fate by regulating multiple signal transduction pathways and is found to be overexpressed in a variety of malignant tumors. Herein, we found the expression of PIN1 is up-regulated while miRNA-370 (miR-370) down-regulated in both esophageal squamous-cell carcinoma (ESCC) tissues and cells. Transfection of miR-370 can significantly decrease PIN1 expression in targeting ESCC cells. Overexpression of miR-370 can induce decreased cell proliferation and cell cycle arrest, as well as increased apoptosis in ESCC cells, while this function can be significantly prevented by co-transfection of PIN1. Further experimental results demonstrated that β-catenin, cyclin D1, and caspase activation might be involved in miR-370/PIN1 induced growth inhibition and apoptosis. Besides, low miR-370 and high PIN1 expression significantly correlated with tumor diameter, poor differentiation, tumor invasion and lymph node metastasis in patients diagnosed with ESCC. In conclusion, downregulation of miR-370 in ESCC is associated with cancer progression and promotes cancer cell proliferation via upregulating PIN1, which might be a potential therapeutic target and adverse prognostic factor in the clinic.

LncRNAs are altered in lung squamous cell carcinoma and lung adenocarcinoma

Long non-coding RNAs (lncRNAs) have been implicated in pathogenesis of various cancers, including lung squamous cell carcinoma (LUSC) and lung adenocarcinoma (LUAD). We used cBioPortal to analyze lncRNA alteration frequencies and their ability to predict overall survival (OS) using 504 LUSC and 522 LUAD samples from The Cancer Genome Atlas (TCGA) database. In LUSC, 624 lncRNAs had alteration rates > 1% and 64 > 10%. In LUAD 625 lncRNAs had alteration rates > 1% and 36 > 10%. Among those, 620 lncRNAs had alteration frequencies > 1% in both LUSC and LUAD, while 22 were LUSC-specific and 23 were LUAD-specific. Twenty lncRNAs had alteration frequencies > 10% in both LUSC and LUAD, while 44 were LUSC-specific and 16 were LUAD specific. Genome ontology and pathway analyses produced similar results for LUSC and LUAD. Two lncRNAs (IGF2BP2-AS1 and DGCR5) correlated with better OS in LUSC, and three (MIR31HG, CDKN2A-AS1 and LINC01600) predicted poor OS in LUAD. Chip-seq and luciferase reporter assays identified potential IGF2BP2-AS1, DGCR5 and LINC01600 promoters and enhancers. This study presented lncRNA landscapes and revealed differentially expressed, highly altered lncRNAs in LUSC and LUAD. LncRNAs that act as oncogenes and lncRNA-regulating transcription factors provide novel targets for anti-lung cancer therapeutics.

In silico identification of potential key regulatory factors in smoking-induced lung cancer

Background

Lung cancer is a leading cause of cancer-related death worldwide and is the most commonly diagnosed cancer. Like other cancers, it is a complex and highly heterogeneous disease involving multiple signaling pathways. Identifying potential therapeutic targets is critical for the development of effective treatment strategies.

Methods

We used a systems biology approach to identify potential key regulatory factors in smoking-induced lung cancer. We first identified genes that were differentially expressed between smokers with normal lungs and those with cancerous lungs, then integrated these differentially expressed genes (DEGs) with data from a protein-protein interaction database to build a network model with functional modules for pathway analysis. We also carried out a gene set enrichment analysis of DEG lists using the Kinase Enrichment Analysis (KEA), Protein-Protein Interaction (PPI) hubs, and KEGG (Kyoto Encyclopedia of Genes and Genomes) databases.

Results

Twelve transcription factors were identified as having potential significance in lung cancer (CREB1, NUCKS1, HOXB4, MYCN, MYC, PHF8, TRIM28, WT1, CUX1, CRX, GABP, and TCF3); three of these (CRX, GABP, and TCF) have not been previously implicated in lung carcinogenesis. In addition, 11 kinases were found to be potentially related to lung cancer (MAPK1, IGF1R, RPS6KA1, ATR, MAPK14, MAPK3, MAPK4, MAPK8, PRKCZ, and INSR, and PRKAA1). However, PRKAA1 is reported here for the first time. MEPCE, CDK1, PRKCA, COPS5, GSK3B, BRCA1, EP300, and PIN1 were identified as potential hubs in lung cancer-associated signaling. In addition, we found 18 pathways that were potentially related to lung carcinogenesis, of which 12 (mitogen-activated protein kinase, gonadotropin-releasing hormone, Toll-like receptor, ErbB, and insulin signaling; purine and ether lipid metabolism; adherens junctions; regulation of autophagy; snare interactions in vesicular transport; and cell cycle) have been previously identified.

Conclusion

Our systems-based approach identified potential key molecules in lung carcinogenesis and provides a basis for investigations of tumor development as well as novel drug targets for lung cancer treatment.

Imazamethabenz inhibits human breast cancer cell proliferation, migration and invasion via combination with Pin1

Overexpression of peptidyl-prolyl cis/trans isomerase, NIMA interacting‑1 (Pin1) is a significant marker of the occurrence and development of tumors. In the present study, the imidazoline ketone herbicide imazamethabenz was investigated as a potential antitumor drug by inhibiting Pin1. Molecular docking and enzyme activity tests verified, for the first time, that the imidazoline ketone compound imazamethabenz effectively inhibited Pin1 in vitro. MTT assays, western blotting, wound healing assay and Matrigel invasion assays revealed that imazamethabenz induced apoptosis and inhibited migration and invasion of the breast cancer cell line MCF‑7, which overexpresses Pin1, by inhibiting the Pin1‑mediated signaling pathway involving vascular endothelial growth factor and matrix metalloproteinase 9. These findings indicated that imazamethabenz offers potential applications for the treatment of tumors as a Pin1 inhibitor.

Induction of cell death in pancreatic ductal adenocarcinoma by indirubin 3'-oxime and 5-methoxyindirubin 3'-oxime in vitro and in vivo

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive cancer with a poor prognosis. To identify potential effective therapeutic drugs for PDAC, we established a screening system based on spheroid formation using 170#3 mouse PDAC cells with or without fibroblasts. We found that indirubin 3'-oxime (Indox) and 5-methoxyindirubin 3'-oxime (5MeOIndox) inhibited PDAC cell proliferation. Furthermore, PDAC xenograft growth was also inhibited in BALB/c nu/nu mice after administration of Indox and 5MeOIndox. Both phosphorylated CDK1 and cyclin B1 levels in 170#3 cells were significantly reduced by treatment with Indox and 5MeOIndox in vitro and in vivo. Cell cycle analysis revealed that 5MeOIndox, but not Indox, induced G2/M arrest. Annexin V-propidium iodide double-staining analysis demonstrated that Indox induced abundant non-apoptotic cell death of 170#3 cells, while 5MeOIndox predominantly induced early apoptosis, indicating that the cytotoxicity of 5MeOIndox is lower than that of Indox. These results suggest that one mechanism of 5MeOIndox is to induce G2/M arrest of PDAC cells via inhibition of CDK1/cyclin B1 levels, thereby leading to apoptosis. Our findings suggest 5MeOIndox as a potential useful anticancer agent in PDAC.

Cudraxanthone H Induces Growth Inhibition and Apoptosis in Oral Cancer Cells via NF-κB and PIN1 Pathways

Cudraxanthone H (CH) is a natural compound isolated from a methanol extract of the root bark of Cudrania tricuspidata, a herbal plant also known as Moraceae. However, the effect of CH on human cancer cells has not been reported previously. The aim of this study was to investigate the anticancer effects and mechanism of action of CH on oral squamous cell carcinoma (OSCC) cells. CH exerted significant antiproliferative effects on OSCC cells in dose- and time-dependent manners. CH also induced apoptosis in OSCC cells, as evidenced by an increased percentage of cells in the sub-G1 phase of the cell cycle, annexin V-positive/propidium iodide-negative cells, and nuclear morphology. This antiproliferative effect of CH was associated with a marked reduction in the expression of cyclin D1 and cyclin E, with a concomitant induction of cyclin-dependent kinase inhibitor (CDKI) expression (p21 and p27). CH inhibited the phosphorylation and degradation of I[Formula: see text]B-[Formula: see text]and the nuclear translocation of NF-[Formula: see text]B p65. Furthermore, CH treatment down-regulated PIN1 mRNA and protein expression in a dose-dependent manner. PIN1 overexpression by infection with adenovirus-PIN1 (Ad-PIN1) attenuated the CH-induced growth-inhibiting and apoptosis-inducing effects, blocked CH-enhanced CDKI expression and restored cyclin levels. In contrast, inhibiting PIN1 expression via juglone exerted the opposite effects. The present study is the first to demonstrate antiproliferative and apoptosis-inducing effects of CH, which exerts its effects by inhibiting NF-[Formula: see text]B and PIN1. These data suggest that it might be a novel alternative chemotherapeutic agent for use in the treatment of oral cancer.

Indirubin and Indirubin Derivatives for Counteracting Proliferative Diseases

Indirubin is the active component of Danggui Longhui Wan, a traditional Chinese medicine formulation. The encouraging clinical results from the 1980s obtained in chronic myelocytic leukemia patients treated with indirubin stimulated numerous studies on this compound. These investigations explored the use of indirubin in different types of cancer and reported the synthesis of novel derivatives with improved chemical and pharmacokinetic properties. In this paper, we review the impressive progress that has been made in elucidating the mechanistic understanding of how indirubin and its derivatives affect physiological and pathophysiological processes, mainly by inhibition of cell proliferation and induction of cell death. Furthermore, we survey the therapeutic use of these compounds in combating proliferative diseases such as cancer, restenosis, and psoriasis.

Enhancing effects of indirubin on the arsenic disulfide-induced apoptosis of human diffuse large B-cell lymphoma cells

The aim of the present study was to investigate the indirubin-enhanced effects of arsenic disulfide (As₂S₂) on the proliferation and apoptosis of diffuse large B-cell lymphoma (DLBCL) cells in order to identify an optimum combination therapy. The human DLBCL cells, LY1 and LY8, were treated with different concentrations of indirubin for 24, 48 and 72 h. Next, the cells were treated with 10 μM As₂S₂ or a combination of 10 μM As₂S₂ and 20 μM indirubin for 48 h. Cell proliferation inhibition was detected using cell counting kit-8 and cell apoptosis was determined using flow cytometry. The expression levels of Bcl-2, Bcl-2-associated X protein (Bax) and caspase-3 were analyzed by quantitative polymerase chain reaction (qPCR) and western blotting. The DLBCL cell viability exhibited no significant changes at 24, 48 or 72 h with increasing indirubin concentration. In addition, the apoptotic rates of the LY1 and LY8 cells demonstrated no noticeable effects at 48 h with increasing indirubin concentration. Following treatment with the combination of indirubin and As₂S₂, the inhibitory and apoptotic rates of the cells were notably increased compared with those of the As₂S₂-treated group. The qPCR results revealed that indirubin alone had no enhancing effect upon the Bax/Bcl-2 mRNA expression ratio and caspase-3 mRNA expression. Western blot analysis revealed that indirubin alone had an enhancing effect upon the Bax/Bcl-2 protein ratio and procaspase-3 protein expression. In addition, the results demonstrated that the 21-KDa Bax protein was proteolytically cleaved into an 18-KDa Bax in the DLBCL cells treated with the combination of indirubin and As₂S₂. Indirubin alone did not inhibit proliferation or induce the apoptosis of the LY1 and LY8 cells. However, the combination of indirubin and As₂S₂ yielded enhancing effects. Therefore, the results of the present study demonstrated that with regard to antitumor activities, As₂S₂ served as the principal drug, whereas indirubin served as the adjuvant drug. The enhancing effect was due, in part, to the induction of the mitochondrial apoptotic pathway, which involves the cleavage of Bax.

Polo-like kinase 1 is overexpressed in renal cancer and participates in the proliferation and invasion of renal cancer cells

Polo-like kinase 1 (Plk1) is an interesting molecule both as a biomarker and as a target for highly specific cancer therapy for several reasons. However, the functional significance of Plk1 in renal cell carcinoma (RCC) has not been reported. To explore whether Plk1 plays a general role in renal carcinoma, we examined the expression of Plk1 protein in renal urothelial carcinoma and cell lines, and analyzed the relationship between Plk1 protein expression and development, proliferation, and invasion of renal carcinoma. Immunohistochemisty was used to detect the expression of Plk1 in 100 renal carcinoma tissues. Moreover, the expression of Plk1 was analyzed by western blot and real-time polymerase chain reaction (PCR) in 80 renal carcinoma tissues and 20 normal renal tissues. CCK-8 assay, colony formation assay, and Transwell assay were used to examine proliferation and invasion ability of renal cancer cells with treatment of scytonemin (the specific inhibitor of Plk1). Statistical analysis was used to discuss the association between Plk1 expression and clinicopathologic parameters, and proliferation and invasion ability of renal cancer cells. Plk1 expressions were greater in cancerous tissues than in normal tissues (P<0.05). With an increase in tumor grade and stage, tumor metastasis, and recurrence, the level of Plk1 increased significantly in renal cancerous tissues. Moreover, there was a significantly higher expression of Plk1 in higher degree of malignant renal adenocarcinoma cell ACHN than that in renal adenocarcinoma cell 769-P. With increasing concentration of scytonemin, we found that cell proliferation and invasion activity decreased significantly. Plk1 expression status was closely correlated with important histopathologic characteristics (grades, stages, metastasis, and recurrence) of renal carcinomas. Furthermore, Plk1 played an important function on renal cancer cells' proliferation and invasion.

Decursin exerts anti-cancer activity in MDA-MB-231 breast cancer cells via inhibition of the Pin1 activity and enhancement of the Pin1/p53 association

The peptidyl-prolyl cis/trans isomerase Pin1 is overexpressed in a wide variety of cancer cells and thus considered as an important target molecule for cancer therapy. This study demonstrates that decursin, a bioactive compound from Angelica gigas, exert the anti-cancer effect against breast cancer cells via regulation of Pin1 and its related signaling molecules. We observed that decursin induced G1 arrest with decrease in cyclin D1 level in Pin1-expressing breast cancer cells MDA-MB-231, but not Pin1-non-expressing breast cancer cells MDA-MB-157. In addition, decursin significantly reduced protein expression and enzymatic activity of Pin1 in MDA-MB-231 cells. Further, we found that decursin treatment enhanced the p53 expression level and failed to down-regulate Pin1 in the cells transfected with p53 siRNA, indicating the importance of p53 in the decursin-mediated Pin1 inhibition in MDA-MB-231 cells. Decursin stimulated association between Pin1 to p53. Moreover, decursin facilitated p53 transcription in MDA-MB-231 cells. Overall, our current study suggests the potential of decursin as an attractive cancer therapeutic agent for breast cancer by targeting Pin1 protein.

The APC/C Ubiquitin Ligase: From Cell Biology to Tumorigenesis

The ubiquitin proteasome system (UPS) is required for normal cell proliferation, vertebrate development, and cancer cell transformation. The UPS consists of multiple proteins that work in concert to target a protein for degradation via the 26S proteasome. Chains of an 8.5-kDa protein called ubiquitin are attached to substrates, thus allowing recognition by the 26S proteasome. Enzymes called ubiquitin ligases or E3s mediate specific attachment to substrates. Although there are over 600 different ubiquitin ligases, the Skp1-Cullin-F-box (SCF) complexes and the anaphase promoting complex/cyclosome (APC/C) are the most studied. SCF involvement in cancer has been known for some time while APC/C's cancer role has recently emerged. In this review we will discuss the importance of APC/C to normal cell proliferation and development, underscoring its possible contribution to transformation. We will also examine the hypothesis that modulating a specific interaction of the APC/C may be therapeutically attractive in specific cancer subtypes. Finally, given that the APC/C pathway is relatively new as a cancer target, therapeutic interventions affecting APC/C activity may be beneficial in cancers that are resistant to classical chemotherapy.