CDC25C

Gene Summary

Gene:CDC25C; cell division cycle 25C
Aliases: CDC25, PPP1R60
Location:5q31.2
Summary:This gene encodes a conserved protein that plays a key role in the regulation of cell division. The encoded protein directs dephosphorylation of cyclin B-bound CDC2 and triggers entry into mitosis. It also suppresses p53-induced growth arrest. Multiple alternatively spliced transcript variants of this gene have been described. [provided by RefSeq, Dec 2015]
Databases:VEGA, OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:M-phase inducer phosphatase 3
Source:NCBIAccessed: 16 March, 2017

Ontology:

What does this gene/protein do?
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Pathways:What pathways are this gene/protein implicaed in?
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Cancer Overview

Research Indicators

Publications Per Year (1992-2017)
Graph generated 16 March 2017 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

Tag cloud generated 16 March, 2017 using data from PubMed, MeSH and CancerIndex

Specific Cancers (4)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: CDC25C (cancer-related)

Duangprompo W, Aree K, Itharat A, Hansakul P
Effects of 5,6-Dihydroxy-2,4-Dimethoxy-9,10-Dihydrophenanthrene on G2/M Cell Cycle Arrest and Apoptosis in Human Lung Carcinoma Cells.
Am J Chin Med. 2016; 44(7):1473-1490 [PubMed] Related Publications
5,6-dihydroxy-2,4-dimethoxy-9,10-dihydrophenanthrene (HMP) is an active compound isolated from the rhizome extracts of Dioscorea membranacea Pierre, a Thai medicinal plant. This study aimed to investigate the growth-inhibitory and apoptosis-inducing effects of HMP in human lung cancer A549 cells. The antiproliferative and cytotoxic effects of HMP were analyzed by a Sulforhodamine B assay. Cell division, cell cycle distribution and membrane asymmetry changes were each performed with different fluorescent dyes and then analyzed by flow cytometry. Real-time PCR and immunoblotting were used to detect cell cycle- and apoptosis-related mRNA levels and proteins, respectively. The nuclear morphology of the cells stained with DAPI and DNA fragmentation were detected by fluorescence microscopy and gel electrophoresis, respectively. The results showed that HMP exerted strong antiproliferative and cytotoxic activities in A549 cells with the highest selectivity index. It halted the cell cycle in [Formula: see text]/M phase via down-regulation of the expression levels of regulatory proteins Cdc25C, Cdk1 and cyclinB1. In addition, HMP induced early apoptotic cells with externalized phosphatidylserine and subsequent apoptotic cells in sub-[Formula: see text] phase. HMP increased caspase-3 activity and levels of the cleaved (active) form of caspase-3 whose actions were supported by the cleavage of its target PARP, nuclear condensation and DNA apoptotic ladder. Moreover, HMP significantly increased the mRNA and protein levels of proapoptotic Bax as well as promoted subsequent caspase-9 activation and BID cleavage, indicating HMP-induced apoptosis via both intrinsic and extrinsic pathways. These data support, for the first time, the potential role of HMP as a cell-cycle arrest and apoptosis-inducing agent for lung cancer treatment.

Yu YQ, Weng J, Li SQ, et al.
MiR-675 Promotes the Growth of Hepatocellular Carcinoma Cells Through the Cdc25A Pathway.
Asian Pac J Cancer Prev. 2016; 17(8):3881-5 [PubMed] Related Publications
BACKGROUND: MicroRNAs (miRNAs) have fundamental roles in tumorigenesis. MiR-675 is upregulated in hepatocellular carcinoma(HCC) cells. However, the roles of miR-675 in hepatocellular carcinogenesis are still not fully elucidated. In this study, we focus on investigating the effect and mechanism of miR-675 in proliferation of HCC cells.
MATERIALS AND METHODS: The cell proliferation was measured by MTT assays after transfection with miR-675 inhibitor and miR-675 mimics in HCC cells. The expression level of miR-675 was detected by real-time quantitative reverse transcription polymerase chain reaction. Protein expression of Cdc25A was measured by western blotting analysis.
RESULTS: In MTT assays, overexpression of miR-675 promoted the proliferation of HCC cells(<0.05. at 48 hours, <0.01. at 72 hours) compared with the miR-675mimics control group. Downexpression of miR-675 inhibited the proliferation of HCC cells(<0.05. at 48 hours, <0.01. at 72 hours) compared with the miR-675inhibitor control group. In western blotting analysis, the expression level of Cdc25A was significantly increased (<0.05) after treatment with miR-675 mimics. The expression level of Cdc25A was significantly decreased (<0.05) after treatment with miR-675 inhibitor.
CONCLUSIONS: Our results indicate that miR-675 promotes proliferation in human hepatocellular carcinoma cells by associating with the Cdc25A signaling pathway.

Yin Y, Dou X, Duan S, et al.
Downregulation of cell division cycle 25 homolog C reduces the radiosensitivity and proliferation activity of esophageal squamous cell carcinoma.
Gene. 2016; 590(2):244-9 [PubMed] Related Publications
Radiation therapy is one of the most important methods of contemporary cancer treatment. Cells in the G2 and M phases are more sensitive to radiation therapy, and cell division cycle 25 homolog C (CDC25C) is essential in shifting the cell cycle between these two phases. In this study, the knockdown of CDC25C in human esophageal squamous carcinoma EC9706 cells was mediated by transfecting shRNA against human CDC25C-subcloning into pGV248. The levels of CDC25C mRNA and protein expression were assessed by reverse transcription-polymerase chain reaction (RT-PCR) and western blotting, respectively. Moreover, cell proliferation and radiosensitivity were measured. Stable CDC25C-knockdown EC9706 cell lines were successfully established. Furthermore, the proliferation of both control and CDC25C-shRNA-EC9706 cells was inhibited after the cells were treated with increasing X-ray doses, and the proliferation of the control cells was affected more significantly (p<0.05). Moreover, cell colony formation assays allowed us to reach the same conclusion. Taken together, our experiments demonstrated that the knockdown of CDC25C can reduce both the radiotherapy sensitivity and the proliferation activity of EC9706 cells. Thus, CDC25C might be a potential biomarker for radiotherapy treatment.

Lu Y, Li F, Xu T, Sun J
miRNA-497 Negatively Regulates the Growth and Motility of Chondrosarcoma Cells by Targeting Cdc25A.
Oncol Res. 2016; 23(4):155-63 [PubMed] Related Publications
Chondrosarcoma (CHS) is the second most common malignant bone sarcoma with increased risk of invasion and metastasis. However, the regulatory mechanisms of CHS tumorigenesis remain unknown. Here we investigated the novel role of miR-497 in regulating chondrosarcoma cell growth and cell cycle arrest. RT-PCR analysis showed that the expression of miR-497 is aberrantly downregulated in human chondrosarcoma samples and cells. After transfection with miR-497 mimic or antagomir, the proliferation and apoptosis of JJ012 and OUMS-27 chondrosarcoma cells were determined by CCK-8 assay and flow cytometric analysis, respectively. Results showed that the proliferation capacity of JJ012 and OUMS-27 cells was significantly decreased by miR-497 overexpression but increased by miR-497 repression. Apoptosis in both cell types was remarkably enhanced by miR-497 mimic but inhibited by miR-497 antagomir. By bioinformatics and luciferase reporter analysis, Cdc25A was proven to be a direct target of miR-497 in chondrosarcoma cells. Further studies indicated that miR-497 modulates the growth of chondrosarcoma cells by targeting Cdc25A, in which the cell cycle inhibitor p21 is involved through a p53-independent pathway. In conclusion, we demonstrated that miR-497 represents a potential tumor suppressor in human chondrosarcoma that regulates the growth of chondrosarcoma cells by targeting Cdc25A. This may provide a novel therapeutic target for chondrosarcoma.

Zhou J, Zhao M, Tang Y, et al.
The milk-derived fusion peptide, ACFP, suppresses the growth of primary human ovarian cancer cells by regulating apoptotic gene expression and signaling pathways.
BMC Cancer. 2016; 16:246 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: ACFP is an anti-cancer fusion peptide derived from bovine milk protein. This study was to investigate the anti-cancer function and underlying mechanisms of ACFP in ovarian cancer.
METHODS: Fresh ovarian tumor tissues were collected from 53 patients who underwent initial debulking surgery, and primary cancer cells were cultured. Normal ovarian surface epithelium cells (NOSECs), isolated from 7 patients who underwent surgery for uterine fibromas, were used as normal control tissue. Anti-viabilities of ACFP were assessed by WST-1 (water-soluble tetrazolium 1), and apoptosis was measured using a flow cytometry-based assay. Gene expression profiles of ovarian cancer cells treated with ACFP were generated by cDNA microarray, and the expression of apoptotic-specific genes, such as bcl-xl, bax, akt, caspase-3, CDC25C and cyclinB1, was assessed by real time PCR and western blot analysis.
RESULTS: Treatment with ACFP inhibited the viability and promoted apoptosis of primary ovarian cancer cells but exhibited little or no cytotoxicity toward normal primary ovarian cells. Mechanistically, the anti-cancer effects of ACFP in ovarian cells were shown to occur partially via changes in gene expression and related signal pathways. Gene expression profiling highlighted that ACFP treatment in ovarian cancer cells repressed the expression of bcl-xl, akt, CDC25C and cyclinB1 and promoted the expression of bax and caspase-3 in a time- and dose-dependent manner.
CONCLUSIONS: Our results suggest that ACFP may represent a potential therapeutic agent for ovarian cancer that functions by altering the expression and signaling of cancer-related pathways in ovarian cancer cells.

Yu R, Yu BX, Chen JF, et al.
Anti-tumor effects of Atractylenolide I on bladder cancer cells.
J Exp Clin Cancer Res. 2016; 35:40 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Atractylenolide I (ATR-1), an active component of Rhizoma Atractylodis Macrocephalae, possesses cytotoxicity against various carcinomas. However, little is known about the effects of ATR-1on bladder cancer. In the present study, the anti-tumor activity of ATR-1 was examined on bladder cancer cells both in vivo and in vitro.
METHODS: MTT assay was used to assess the cytotoxic effect of ATR-1. Cell cycle distribution and apoptosis levels were evaluated using flow cytometry. Western blotting assay was applied to measure the levels of proteins associated with the apoptotic pathway, cell cycle progression and PI3K/Akt/mTOR signaling pathway. Tumor models in nude mice were induced by injection of T-24 and 253J human bladder cancer cells.
RESULTS: ATR-1 inhibited bladder cancer cell proliferation, arrested cell cycle in G2/M phase through up-regulation of p21 and down-regulation of cyclin B1, CDK1 and Cdc25c. Meanwhile, ATR-1 also triggered cellular apoptosis depending on the activation of mitochondrial apoptotic pathway. Mechanism investigation indicated that ATR-1 exerts its anti-tumor effect also relies on the inhibition of PI3K/Akt/mTOR signaling pathway. Finally, mice studies showed that ATR-1 blocked the T-24 or 253J-induced xenograft tumor growth without noticeable toxicity.
CONCLUSIONS: ATR-1 may be served as a potential therapeutic agent for the treatment of bladder cancer.

Cao XC, Yu Y, Hou LK, et al.
miR-142-3p inhibits cancer cell proliferation by targeting CDC25C.
Cell Prolif. 2016; 49(1):58-68 [PubMed] Related Publications
OBJECTIVES: MicroRNAs (miRNAs) contribute to control of cell cycle progression and are frequently deregulated in cancer. The focus of this study was to determine effects of miR-142-3p on the cell cycle progression and cancer cell proliferation.
MATERIALS AND METHODS: RT-qPCR was performed to determine expression of miR-142-3p in a range of cancer cell lines and in clinical cancer specimens. To further understand its role, we restored its expression in cancer cell lines by transfection with miR-142-3p mimics or inhibitors. Effects of miR-142-3p on cell cycle progression and cell proliferation were also determined.
RESULTS: miR-142-3p was down-regulated in both cancer cell lines and cancer specimens. Its overexpression suppressed proliferation, whereas its depletion promoted it. In addition, miR-142-3p lead to cell cycle arrest in G2/M. Moreover, CDC25C was identified as being a target of miR-142-3p, ectopic expression of which reversed suppression of cell proliferation.
CONCLUSIONS: Our observations suggest that miR-142-3p functioned as a tumor suppressor by targeting CDC25C.

Kralovicova J, Knut M, Cross NC, Vorechovsky I
Exon-centric regulation of ATM expression is population-dependent and amenable to antisense modification by pseudoexon targeting.
Sci Rep. 2016; 6:18741 [PubMed] Free Access to Full Article Related Publications
ATM is an important cancer susceptibility gene that encodes a critical apical kinase of the DNA damage response (DDR) pathway. We show that a key nonsense-mediated RNA decay switch exon (NSE) in ATM is repressed by U2AF, PUF60 and hnRNPA1. The NSE activation was haplotype-specific and was most promoted by cytosine at rs609621 in the NSE 3' splice-site (3'ss), which is predominant in high cancer risk populations. NSE levels were deregulated in leukemias and were influenced by the identity of U2AF35 residue 34. We also identify splice-switching oligonucleotides (SSOs) that exploit competition of adjacent pseudoexons to modulate NSE levels. The U2AF-regulated exon usage in the ATM signalling pathway was centred on the MRN/ATM-CHEK2-CDC25-cdc2/cyclin-B axis and preferentially involved transcripts implicated in cancer-associated gene fusions and chromosomal translocations. These results reveal important links between 3'ss control and ATM-dependent responses to double-strand DNA breaks, demonstrate functional plasticity of intronic variants and illustrate versatility of intronic SSOs that target pseudo-3'ss to modify gene expression.

He Y, Liu X
The tumor-suppressor gene LZTS1 suppresses hepatocellular carcinoma proliferation by impairing PI3K/Akt pathway.
Biomed Pharmacother. 2015; 76:141-6 [PubMed] Related Publications
BACKGROUND: To study the role of LZTS1 in hepatocellular carcinoma (HCC) proliferation and the molecular mechanism involved.
METHODS: LZTS1 expression was studied in 10 HCC cell lines and 1 normal hepatocyte cell line by western blot analysis and qRT-PCR. One HCC cell line was selected and transfected with LZTS1 lentivirus. Cell proliferation and cell cycle were then determined by CCK-8 assay and flow cytometry, respectively. LZTS1, cyclin D1, CDK1, Cdc25C, pS473 Akt, and pT308 Akt mRNA and protein expressions were measured. PS473 Akt and pT308 Akt expression level was also compared with the HCC cells treated with LY294002.
RESULTS: Compared with the normal hepatocyte cells, LZTS1 expression in HCC cells was significantly lower. After the transfection with LZTS1 lentivirus, HCC cell proliferation ability decreased markedly and HCC cells were blocked at G2/M phase. Cyclin D1 and CDK1 expression were both decreased but not significantly. Cdc25C expression was increased significantly. PS473 Akt and pT308 Akt expression level was increased significantly as well, which were almost the same with those transfected with LY294002.
CONCLUSION: LZTS1 could inhibit HCC cell proliferation by impairing PI3K/Akt pathway.

Lu X, Sun W, Tang Y, et al.
Identification of key genes in hepatocellular carcinoma and validation of the candidate gene, cdc25a, using gene set enrichment analysis, meta-analysis and cross-species comparison.
Mol Med Rep. 2016; 13(2):1172-8 [PubMed] Free Access to Full Article Related Publications
The aim of the present study was to determine key pathways and genes involved in the pathogenesis of hepatocellular carcinoma (HCC) through bioinformatic analyses of HCC microarray data based on cross-species comparison. Microarray data of gene expression in HCC in different species were analyzed using gene set enrichment analysis (GSEA) and meta-analysis. Reverse transcription-quantitative polymerase chain reaction and western blotting were performed to determine the mRNA and protein expression levels of cdc25a, one of the identified candidate genes, in human, rat and tree shrew samples. The cell cycle pathway had the largest overlap between the GSEA and meta-analysis. Meta-analyses showed that 25 genes, including cdc25a, in the cell cycle pathway were differentially expressed. Cdc25a mRNA levels in HCC tissues were higher than those in normal liver tissues in humans, rats and tree shrews, and the expression level of cdc25a in HCC tissues was higher than in corresponding paraneoplastic tissues in humans and rats. In human HCC tissues, the cdc25a mRNA level was significantly correlated with clinical stage, portal vein tumor thrombosis and extrahepatic metastasis. Western blotting showed that, cdc25a protein levels were significantly upregulated in HCC tissues in humans, rats and tree shrews. In conclusion, GSEA and meta-analysis can be combined to identify key molecules and pathways involved in HCC. This study demonstrated that the cell cycle pathway and the cdc25a gene may be crucial in the pathogenesis and progression of HCC.

Zhan W, Han T, Zhang C, et al.
TRIM59 Promotes the Proliferation and Migration of Non-Small Cell Lung Cancer Cells by Upregulating Cell Cycle Related Proteins.
PLoS One. 2015; 10(11):e0142596 [PubMed] Free Access to Full Article Related Publications
TRIM protein family is an evolutionarily conserved gene family implicated in a number of critical processes including inflammation, immunity, antiviral and cancer. In an effort to profile the expression patterns of TRIM superfamily in several non-small cell lung cancer (NSCLC) cell lines, we found that the expression of 10 TRIM genes including TRIM3, TRIM7, TRIM14, TRIM16, TRIM21, TRIM22, TRIM29, TRIM59, TRIM66 and TRIM70 was significantly upregulated in NSCLC cell lines compared with the normal human bronchial epithelial (HBE) cell line, whereas the expression of 7 other TRIM genes including TRIM4, TRIM9, TRIM36, TRIM46, TRIM54, TRIM67 and TRIM76 was significantly down-regulated in NSCLC cell lines compared with that in HBE cells. As TRIM59 has been reported to act as a proto-oncogene that affects both Ras and RB signal pathways in prostate cancer models, we here focused on the role of TRIM59 in the regulation of NSCLC cell proliferation and migration. We reported that TRIM59 protein was significantly increased in various NSCLC cell lines. SiRNA-induced knocking down of TRIM59 significantly inhibited the proliferation and migration of NSCLC cell lines by arresting cell cycle in G2 phase. Moreover, TRIM59 knocking down affected the expression of a number of cell cycle proteins including CDC25C and CDK1. Finally, we knocked down TRIM59 and found that p53 protein expression levels did not upregulate, so we proposed that TRIM59 may promote NSCLC cell growth through other pathways but not the p53 signaling pathway.

Fischer M, Quaas M, Nickel A, Engeland K
Indirect p53-dependent transcriptional repression of Survivin, CDC25C, and PLK1 genes requires the cyclin-dependent kinase inhibitor p21/CDKN1A and CDE/CHR promoter sites binding the DREAM complex.
Oncotarget. 2015; 6(39):41402-17 [PubMed] Free Access to Full Article Related Publications
The transcription factor p53 is central to cell cycle control by downregulation of cell cycle-promoting genes upon cell stress such as DNA damage. Survivin (BIRC5), CDC25C, and PLK1 encode important cell cycle regulators that are repressed following p53 activation. Here, we provide evidence that p53-dependent repression of these genes requires activation of p21 (CDKN1A, WAF1, CIP1). Chromatin immunoprecipitation (ChIP) data indicate that promoter binding of B-MYB switches to binding of E2F4 and p130 resulting in a replacement of the MMB (Myb-MuvB) by the DREAM complex. We demonstrate that this replacement depends on p21. Furthermore, transcriptional repression by p53 requires intact DREAM binding sites in the target promoters. The CDE and CHR cell cycle promoter elements are the sites for DREAM binding. These elements as well as the p53 response of Survivin, CDC25C, and PLK1 are evolutionarily conserved. No binding of p53 to these genes is detected by ChIP and mutation of proposed p53 binding sites does not alter the p53 response. Thus, a mechanism for direct p53-dependent transcriptional repression is not supported by the data. In contrast, repression by DREAM is consistent with most previous findings and unifies models based on p21-, E2F4-, p130-, and CDE/CHR-dependent repression by p53. In conclusion, the presented data suggest that the p53-p21-DREAM-CDE/CHR pathway regulates p53-dependent repression of Survivin, CDC25C, and PLK1.

Ta HQ, Ivey ML, Frierson HF, et al.
Checkpoint Kinase 2 Negatively Regulates Androgen Sensitivity and Prostate Cancer Cell Growth.
Cancer Res. 2015; 75(23):5093-105 [PubMed] Free Access to Full Article Related Publications
Prostate cancer is the second leading cause of cancer death in American men, and curing metastatic disease remains a significant challenge. Nearly all patients with disseminated prostate cancer initially respond to androgen deprivation therapy (ADT), but virtually all patients will relapse and develop incurable castration-resistant prostate cancer (CRPC). A high-throughput RNAi screen to identify signaling pathways regulating prostate cancer cell growth led to our discovery that checkpoint kinase 2 (CHK2) knockdown dramatically increased prostate cancer growth and hypersensitized cells to low androgen levels. Mechanistic investigations revealed that the effects of CHK2 were dependent on the downstream signaling proteins CDC25C and CDK1. Moreover, CHK2 depletion increased androgen receptor (AR) transcriptional activity on androgen-regulated genes, substantiating the finding that CHK2 affects prostate cancer proliferation, partly, through the AR. Remarkably, we further show that CHK2 is a novel AR-repressed gene, suggestive of a negative feedback loop between CHK2 and AR. In addition, we provide evidence that CHK2 physically associates with the AR and that cell-cycle inhibition increased this association. Finally, IHC analysis of CHK2 in prostate cancer patient samples demonstrated a decrease in CHK2 expression in high-grade tumors. In conclusion, we propose that CHK2 is a negative regulator of androgen sensitivity and prostate cancer growth, and that CHK2 signaling is lost during prostate cancer progression to castration resistance. Thus, perturbing CHK2 signaling may offer a new therapeutic approach for sensitizing CRPC to ADT and radiation.

Li YR, Li S, Ho CT, et al.
Tangeretin derivative, 5-acetyloxy-6,7,8,4'-tetramethoxyflavone induces G2/M arrest, apoptosis and autophagy in human non-small cell lung cancer cells in vitro and in vivo.
Cancer Biol Ther. 2016; 17(1):48-64 [PubMed] Free Access to Full Article Related Publications
Tangeretin, a major phytochemicals in tangerine peels--an important Chinese herb, has been found to have anti-carcinogenic properties. To improve bioavailability and increase potency of tangeretin, its derivative, 5-acetyloxy-6,7,8,4'-tetramethoxyflavone (5-AcTMF), has been synthesized and shown potent inhibition of proliferation activity against human breast and leukemia cancer cell lines. In this study, we have further investigated the anticancer effects of 5-AcTMF on CL1-5 non-small cell lung cancer cells (NSCLC) both in vitro and in vivo and demonstrated that 5-AcTMF effectively inhibited cancer cell proliferation, induced G2/M-phase arrest associated with cdc2 and CDC25c and increased in the apoptotic cells associated with caspase activation, down regulation of Bcl-2, XIAP and Survivn, inducing release of cytochrome c into the cytosol and disruption of mitochondrial membrane potential. We also found that 5-AcTMF treatment of CL1-5 activated autophagy, indicated by triggered autophagosome formation and increased LC3-II levels and formation of LC3 puncta. Moreover, we also found that 5-AcTMF lowered phophoatidylinositol 3-kinase/AKT/mTOR signaling pathway. Over-expression of AKT by AKT cDNA transfection decreased 5-AcTMF mediated apoptosis and autophagy, supporting the induction of apoptosis and autophagy by inhibition of AKT pathway. In an animal study, 5-AcTMF effectively delayed tumor growth in a nude mouse model of CL1-5 xenografts without observed adverse effect. Immunohistochemistry Analysis indicated that 5-AcTMF induced CL1-5 cell apoptosis and autophagy in vivo. Taken together, these data demonstrate that 5-AcTMF is a novel small molecule agent that can inhibit NSCLC cell proliferation, and induce G(2)/M phase arrest and via the mitochondrial apoptotic pathway and autophagy.

Wu L, Zhang X, Zhao Z, et al.
Full-length single-cell RNA-seq applied to a viral human cancer: applications to HPV expression and splicing analysis in HeLa S3 cells.
Gigascience. 2015; 4:51 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Viral infection causes multiple forms of human cancer, and HPV infection is the primary factor in cervical carcinomas. Recent single-cell RNA-seq studies highlight the tumor heterogeneity present in most cancers, but virally induced tumors have not been studied. HeLa is a well characterized HPV+ cervical cancer cell line.
RESULT: We developed a new high throughput platform to prepare single-cell RNA on a nanoliter scale based on a customized microwell chip. Using this method, we successfully amplified full-length transcripts of 669 single HeLa S3 cells and 40 of them were randomly selected to perform single-cell RNA sequencing. Based on these data, we obtained a comprehensive understanding of the heterogeneity of HeLa S3 cells in gene expression, alternative splicing and fusions. Furthermore, we identified a high diversity of HPV-18 expression and splicing at the single-cell level. By co-expression analysis we identified 283 E6, E7 co-regulated genes, including CDC25, PCNA, PLK4, BUB1B and IRF1 known to interact with HPV viral proteins.
CONCLUSION: Our results reveal the heterogeneity of a virus-infected cell line. It not only provides a transcriptome characterization of HeLa S3 cells at the single cell level, but is a demonstration of the power of single cell RNA-seq analysis of virally infected cells and cancers.

Iacobucci I, Di Rorà AG, Falzacappa MV, et al.
In vitro and in vivo single-agent efficacy of checkpoint kinase inhibition in acute lymphoblastic leukemia.
J Hematol Oncol. 2015; 8:125 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Although progress in children, in adults, ALL still carries a dismal outcome. Here, we explored the in vitro and in vivo activity of PF-00477736 (Pfizer), a potent, selective ATP-competitive small-molecule inhibitor of checkpoint kinase 1 (Chk1) and with lower efficacy of checkpoint kinase 2 (Chk2).
METHODS: The effectiveness of PF-00477736 as single agent in B-/T-ALL was evaluated in vitro and in vivo studies as a single agent. The efficacy of the compound in terms of cytotoxicity, induction of apoptosis, and changes in gene and protein expression was assessed using different B-/T-ALL cell lines. Finally, the action of PF-00477736 was assessed in vivo using leukemic mouse generated by a single administration of the tumorigenic agent N-ethyl-N-nitrosourea.
RESULTS: Chk1 and Chk2 are overexpressed concomitant with the presence of genetic damage as suggested by the nuclear labeling for γ-H2A.X (Ser139) in 68 % of ALL patients. In human B- and T-ALL cell lines, inhibition of Chk1/2 as a single treatment strategy efficiently triggered the Chk1-Cdc25-Cdc2 pathway resulting in a dose- and time-dependent cytotoxicity, induction of apoptosis, and increased DNA damage. Moreover, treatment with PF-00477736 showed efficacy ex vivo in primary leukemic blasts separated from 14 adult ALL patients and in vivo in mice transplanted with T-ALL, arguing in favor of its future clinical evaluation in leukemia.
CONCLUSIONS: In vitro, ex vivo, and in vivo results support the inhibition of Chk1 as a new therapeutic strategy in acute lymphoblastic leukemia, and they provide a strong rationale for its future clinical investigation.

Bertoli S, Boutzen H, David L, et al.
CDC25A governs proliferation and differentiation of FLT3-ITD acute myeloid leukemia.
Oncotarget. 2015; 6(35):38061-78 [PubMed] Free Access to Full Article Related Publications
We investigated cell cycle regulation in acute myeloid leukemia cells expressing the FLT3-ITD mutated tyrosine kinase receptor, an underexplored field in this disease. Upon FLT3 inhibition, CDC25A mRNA and protein were rapidly down-regulated, while levels of other cell cycle proteins remained unchanged. This regulation was dependent on STAT5, arguing for FLT3-ITD-dependent transcriptional regulation of CDC25A. CDC25 inhibitors triggered proliferation arrest and cell death of FLT3-ITD as well as FLT3-ITD/TKD AC-220 resistant cells, but not of FLT3-wt cells. Consistently, RNA interference-mediated knock-down of CDC25A reduced the proliferation of FLT3-ITD cell lines. Finally, the clonogenic capacity of primary FLT3-ITD AML cells was reduced by the CDC25 inhibitor IRC-083864, while FLT3-wt AML and normal CD34+ myeloid cells were unaffected. In good agreement, in a cohort of 100 samples from AML patients with intermediate-risk cytogenetics, high levels of CDC25A mRNA were predictive of higher clonogenic potential in FLT3-ITD+ samples, not in FLT3-wt ones.Importantly, pharmacological inhibition as well as RNA interference-mediated knock-down of CDC25A also induced monocytic differentiation of FLT3-ITD positive cells, as judged by cell surface markers expression, morphological modifications, and C/EBPα phosphorylation. CDC25 inhibition also re-induced monocytic differentiation in primary AML blasts carrying the FLT3-ITD mutation, but not in blasts expressing wild type FLT3. Altogether, these data identify CDC25A as an early cell cycle transducer of FLT3-ITD oncogenic signaling, and as a promising target to inhibit proliferation and re-induce differentiation of FLT3-ITD AML cells.

Deng D, Xue L, Shao N, et al.
miR-137 acts as a tumor suppressor in astrocytoma by targeting RASGRF1.
Tumour Biol. 2016; 37(3):3331-40 [PubMed] Related Publications
Astrocytoma is one of the most common primary central nervous system tumors and has both high mortality and a poor 5-year survival rate. MicroRNAs (miRNAs) play important roles in carcinogenesis by acting on multiple signaling pathways. Although we have demonstrated that miR-137 is downregulated in astrocytoma tissues, the role of miR-137 in astrocytoma still remains unknown. In the present study, we aimed to investigate the function of miR-137 and its possible target genes in astrocytoma. miR-137 was significantly downregulated in astrocytoma tissues, and its expression level was inversely correlated with the clinical stage. Restoring miR-137 was able to dramatically inhibit cell proliferation, migration, and invasion and enhance apoptosis in vitro, whereas silencing its expression inhibited these processes. By overexpressing or inhibiting miR-137 in cancer cells, we experimentally confirmed that miR-137 directly recognized the 3'-UTR (3'-untranslated region) of the RASGRF1 (Ras protein-specific guanine nucleotide-releasing factor 1) transcript and regulated RASGRF1 expression. Furthermore, an inverse correlation was observed between miR-137 levels and RASGRF1 protein levels, but not mRNA levels, in astrocytoma samples. The silencing of RASGRF1 resulted in similar effects to miR-137 restoration in cancer cells. Finally, overexpression of RASGRF1 rescued the inhibitory effects of miR-137. Taken together, our results indicate that miR-137 acts as a tumor suppressor in astrocytoma by targeting RASGRF1. These findings suggest that miR-137 may serve as a novel therapeutic target in astrocytoma treatment.

Chiang KC, Chen HY, Hsu SY, et al.
PTEN insufficiency modulates ER+ breast cancer cell cycle progression and increases cell growth in vitro and in vivo.
Drug Des Devel Ther. 2015; 9:4631-8 [PubMed] Free Access to Full Article Related Publications
Phosphatase and tensin homolog (PTEN), a well-known tumor suppressor gene and frequently mutated or lost in breast cancer, possesses the negative regulation function over the PI3K/Akt/mTOR pathway. PTEN insufficiency has been associated with advanced breast cancer and poor prognosis of breast cancer patients. Recently, target therapies aimed at PI3K/Akt/mTOR pathway to treat breast cancer have got popularity. However, the exact effect of PTEN on breast cancer cells is still not well understood. This study demonstrated that PTEN knockdown in MCF-7 cells strengthened the downstream gene expressions, including p-Akt, p-ERK1/2, p-mTOR, p-p70s6k, and p-GSK3β. PTEN knockdown MCF-7 cells had increased cell growth and Ki-67 expression. Further Western blot demonstrated that p27 was repressed obviously with p21 slightly inhibited and CDK1, 2, 4, 6, cyclin A, and Cdc25C were upregulated in MCF-7 PTEN knockdown cells, leading to the higher growth rate. More importantly, PTEN knockdown MCF-7 cells had higher tumorigenesis and tumor growth in vivo. From our current work, we provided more detailed PTEN-mediated mechanisms to stimulate ER+ breast cancer cell growth. Our result may pave the way for further target therapy development used alone or in combination with other drugs for ER+ breast cancer with PTEN insufficiency.

Heo JH, Song JY, Jeong JY, et al.
Fibulin-5 is a tumour suppressor inhibiting cell migration and invasion in ovarian cancer.
J Clin Pathol. 2016; 69(2):109-16 [PubMed] Related Publications
AIMS: Fibulin-5 is an extracellular matrix (ECM) glycoprotein which has a role in the organisation and stabilisation of ECM structures and regulating cell proliferation and tumourigenesis. Here, the expression of fibulin-5 and its functional effects on the migration and invasion of ovarian cancer cells were assessed.
METHODS: Expression of fibulin-5 was detected in 44 ovarian tumour tissues by qRT-PCR, Western blotting and immunohistochemistry. We performed cell migration and invasion assays, and cell cycle analysis in fibulin-5 transfected SKOV3 (SKOV3-FBLN5) cells and the parental SKOV3 cells. We further examined the expression of three tissue inhibitors of metalloproteinases (TIMPs) and seven matrix metalloproteinases (MMPs) by RT-PCR.
RESULTS: mRNA and protein expression of fibulin-5 were down-regulated (0.05-fold and 0.1-fold) in ovarian carcinomas compared with control tissues (p<0.01 and p=0.022). In wound-healing and invasion assays, significantly fewer SKOV3-FBLN5 cells than SKOV3 control cells migrated and invaded (39.1%, p=0.046 and 70%, p=0.03, respectively), which was reversed by siRNA-treatment. Overexpression of fibulin-5 induced G2/M arrest and increased cyclin B1, CDC2 and CDC25C. Expression of TIMP-2 (0.56-fold), MMP-3 (0.43-fold) and MMP-13 (0.18-fold) was lower and MMP-9 expression (2.20-fold) was higher in SKOV3-FBLN5 cells than in control cells.
CONCLUSIONS: Fibulin-5 is significantly down-regulated in ovarian carcinoma and acts as a tumour suppressor by inhibiting the migration and invasion of ovarian cancer cells.

Qi LW, Zhang Z, Zhang CF, et al.
Anti-Colon Cancer Effects of 6-Shogaol Through G2/M Cell Cycle Arrest by p53/p21-cdc2/cdc25A Crosstalk.
Am J Chin Med. 2015; 43(4):743-56 [PubMed] Related Publications
Chemopreventive agents can be identified from botanicals. Recently, there has been strong support for the potential of 6-shogaol, a natural compound from dietary ginger (Zingiber officinale), in cancer chemoprevention. However, whether 6-shogaol inhibits the growth of colorectal tumors in vivo remains unknown, and the underlying anticancer mechanisms have not been well characterized. In this work, we observed that 6-shogaol (15 mg/kg) significantly inhibited colorectal tumor growth in a xenograft mouse model. We show that 6-shogaol inhibited HCT-116 and SW-480 cell proliferation with IC50 of 7.5 and 10 μM, respectively. Growth of HCT-116 cells was arrested at the G2/M phase of the cell cycle, primarily mediated by the up-regulation of p53, the CDK inhibitor p21(waf1/cip1) and GADD45α, and by the down-regulation of cdc2 and cdc25A. Using p53(-/-) and p53(+/+) HCT-116 cells, we confirmed that p53/p21 was the main pathway that contributed to the G2/M cell cycle arrest by 6-shogaol. 6-Shogaol induced apoptosis, mainly through the mitochondrial pathway, and the bcl-2 family might act as a key regulator. Our results demonstrated that 6-shogaol induces cancer cell death by inducing G2/M cell cycle arrest and apoptosis. 6-Shogaol could be an active natural product in colon cancer chemoprevention.

He Y, Wang L, Liu W, et al.
MAP3K3 expression in tumor cells and tumor-infiltrating lymphocytes is correlated with favorable patient survival in lung cancer.
Sci Rep. 2015; 5:11471 [PubMed] Free Access to Full Article Related Publications
MAP3K3 is involved in both the immune response and in tumor progression. Its potential biological role in vitro in lung cancer cell lines and the association of mRNA/protein expression patterns with clinical outcome of primary lung tumors were investigated in this study. Silencing MAP3K3 using siRNA in lung cancer cell lines resulted in decreased cell proliferation, migration and invasion. These effects were associated with down-regulation of the JNK, p38, AKT, and GSK3β pathways as determined using phospho-protein and gene expression array analyses. However, MAP3K3 mRNA and protein overexpression in primary lung tumors correlated significantly with favorable patient survival. Gene cluster and pathway analyses of primary tumor datasets indicated that genes positively-correlated with MAP3K3 are significantly involved in immune response rather than the cell cycle regulators observed using in vitro analyses. These results indicate that although MAP3K3 overexpression has an oncogenic role in vitro, in primary lung adenocarcinomas it correlates with an active immune response in the tumor environment that correlates with improved patient survival. MAP3K3 may potentially not only serve as diagnostic/prognostic markers for patients with lung cancer but also provide an indicator for future investigations into immunomodulatory therapies for lung cancer.

Yuan X, Sun X, Shi X, et al.
USP39 promotes the growth of human hepatocellular carcinoma in vitro and in vivo.
Oncol Rep. 2015; 34(2):823-32 [PubMed] Related Publications
Ubiquitin specific protease 39 (USP39) plays an important role in mRNA splicing. In the present study, we investigated the role of USP39 in regulating the growth of hepatocellular carcinoma (HCC). We detected USP39 expression in more than 100 HCC clinical samples. The USP39 expression was significantly higher in the tumor tissues compared to the adjacent normal tissues, and was strongly associated with the pathological grade of HCC. USP39 knockdown inhibited cell proliferation and colony formation in vitro in the HepG2 cells, while upregulation of USP39 promoted tumor cell growth. FCM assay showed that USP39 knockdown led to G2/M arrest and induced apoptosis in the HepG2 cells. USP39 knockdown by shRNA inhibited xenograft tumor growth in nude mice. Moreover, USP39 knockdown led to the upregulation of p-Cdc2 and downregulation of p-Cdc25c and p-myt1, while the expression of total Cdc2, Cdc25c and myt1 was not changed in the USP39-knockdown cells. We also found that p-Cdc2 was decreased in the USP39-overexpressing cells and was upregulated in the xenografted tumors derived from the HepG2/KD cells from nude mice. Meanwhile, the expression levels of FoxM1 and its target genes PLK1 and cyclin B1 were decreased in the USP39-knockdown cells. These results suggest that USP39 may contribute to FoxM1 splicing in HCC tumor cells. Our data indicate that USP39 knockdown inhibited the growth of HCC both in vitro and in vivo through G2/M arrest, which was partly achieved via the inhibition of FoxM1 splicing.

Kiss K, Baghy K, Spisák S, et al.
Chronic hyperglycemia induces trans-differentiation of human pancreatic stellate cells and enhances the malignant molecular communication with human pancreatic cancer cells.
PLoS One. 2015; 10(5):e0128059 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Diabetes mellitus is linked to pancreatic cancer. We hypothesized a role for pancreatic stellate cells (PSC) in the hyperglycemia induced deterioration of pancreatic cancer and therefore studied two human cell lines (RLT-PSC, T3M4) in hyperglycemic environment.
METHODOLOGY/PRINCIPAL FINDINGS: The effect of chronic hyperglycemia (CHG) on PSCs was studied using mRNA expression array with real-time PCR validation and bioinformatic pathway analysis, and confirmatory protein studies. The stress fiber formation (IC: αSMA) indicated that PSCs tend to transdifferentiate to a myofibroblast-like state after exposure to CHG. The phosphorylation of p38 and ERK1/2 was increased with a consecutive upregulation of CDC25, SP1, cFOS and p21, and with downregulation of PPARγ after PSCs were exposed to chronic hyperglycemia. CXCL12 levels increased significantly in PSC supernatant after CHG exposure independently from TGF-β1 treatment (3.09-fold with a 2.73-fold without TGF-β1, p<0.05). The upregualtion of the SP1 transcription factor in PSCs after CHG exposure may be implicated in the increased CXCL12 and IGFBP2 production. In cancer cells, hyperglycemia induced an increased expression of CXCR4, a CXCL12 receptor that was also induced by PSC's conditioned medium. The receptor-ligand interaction increased the phosphorylation of ERK1/2 and p38 resulting in activation of MAP kinase pathway, one of the most powerful stimuli for cell proliferation. Certainly, conditioned medium of PSC increased pancreatic cancer cell proliferation and this effect could be partially inhibited by a CXCR4 inhibitor. As the PSC conditioned medium (normal glucose concentration) increased the ERK1/2 and p38 phosphorylation, we concluded that PSCs produce other factor(s) that influence(s) pancreatic cancer behaviour.
CONCLUSIONS: Hyperglycemia induces increased CXCL12 production by the PSCs, and its receptor, CXCR4 on cancer cells. The ligand-receptor interaction activates MAP kinase signaling that causes increased cancer cell proliferation and migration.

Lin TC, Lin PL, Cheng YW, et al.
MicroRNA-184 Deregulated by the MicroRNA-21 Promotes Tumor Malignancy and Poor Outcomes in Non-small Cell Lung Cancer via Targeting CDC25A and c-Myc.
Ann Surg Oncol. 2015; 22 Suppl 3:S1532-9 [PubMed] Related Publications
BACKGROUND: MicroRNA (miR)-184 has been reported to have a dual role in human cancers. However, the role of miR-184 in non-small cell lung cancer (NSCLC) remains unclear.
METHODS: Wild-type or mutant CDC25A promoters were constructed by PCR and site-directed mutagenesis to verify whether miR-184 could inhibit CDC25A expression at post-transcription level. Boyden chamber assay was used to assess whether miR-184 could modulate cell invasiveness via targeting CDC25A and c-Myc. We utilized 124 tumors from NSCLC patients to determine miR-184, miR-21, PDCD4 mRNA, c-Myc mRNA, and CDC25A mRNA expression levels by means of real-time PCR analysis. The prognostic value of CDC25A, c-Myc, and miR-184 on overall survival (OS) and relapse-free survival (RFS) was evaluated by Kaplan-Meier and Cox regression analysis.
RESULTS: MiR-184 suppressed CDC25A expression by enhancing the instability of its mRNA as a result of miR-184 binding to its coding region. An increase in CDC25A expression by means of a reduction in miR-184 promotes cell invasiveness. Moreover, a concomitant increase in CDC25A and c-Myc expression as a result of decreased miR-184 via the miR-21-mediated PDCD4 reduction is responsible for cell invasiveness. Among patients, miR-184 expression in lung tumors was found to correlate negatively with CDC25A mRNA, c-Myc mRNA, and miR-21 expression, but was positively related to PDCD4 mRNA expression. High-miR-184, High-CDC25A, or high-c-Myc mRNA tumors exhibited shorter OS and RFS periods than their counterparts. The worst OS and RFS were observed in low-miR-184/high-CDC25A/high-c-Myc tumors, followed by low-miR-184 /high-CDC25A, low-miR-184/high-c-Myc, high-c-Myc, and high-CDC25A tumors.
CONCLUSIONS: MiR-184 as a tumor suppressor miR inhibits cell proliferation and invasion capability via targeting CDC25A and c-Myc. Low miR-184 level may predict worse prognosis in NSCLC patients.

Peng ZG, Yao YB, Yang J, et al.
Mangiferin induces cell cycle arrest at G2/M phase through ATR-Chk1 pathway in HL-60 leukemia cells.
Genet Mol Res. 2015; 14(2):4989-5002 [PubMed] Related Publications
This study aimed to determine the effect of mangiferin on the cell cycle in HL-60 leukemia cells and expression of the cell cycle-regulatory genes Wee1, Chk1 and CDC25C and to further investigate the molecular mechanisms of the antileukemic action of mangiferin. The inhibitory effect of mangiferin on HL-60 leukemia cell proliferation was determined by the MTT assay. The impact of mangiferin on the HL-60 cell cycle was evaluated by flow cytometry. After the cells were treated with different concentrations of mangiferin, the expression levels of Wee1, Chk1 and CDC25C mRNA were determined by RT-PCR, and Western blot was used to evaluate the expression levels of cdc25c, cyclin B1, and Akt proteins. The inhibition of HL-60 cell growth by mangiferin was dose- and time-dependent. After treatment for 24 h, cells in G2/M phase increased, and G2/M phase arrest appeared with increased mRNA expression of Wee1, Chk1 and CDC25C. Mangiferin inhibited Chk1 and cdc25c mRNA expression at high concentrations and induced Wee1 mRNA expression in a dose-dependent manner. It significantly inhibited ATR, Chk1, Wee1, Akt, and ERK1/2 phosphorylation but increased cdc2 and cyclin B1 phosphorylation. Furthermore, mangiferin reduced cdc25c, cyclin B1, and Akt protein levels while inducing Wee1 protein expression. It also antagonized the phosphorylation effect of vanadate on ATR, and the phosphorylation effect of EGF on Wee1. These findings indicated that mangiferin inhibits cell cycle progression through the ATR-Chk1 stress response DNA damage pathway, leading to cell cycle arrest at G2/M phase in leukemia cells.

Zhao L, Miao HC, Li WJ, et al.
LW-213 induces G2/M cell cycle arrest through AKT/GSK3β/β-catenin signaling pathway in human breast cancer cells.
Mol Carcinog. 2016; 55(5):778-92 [PubMed] Related Publications
LW-213 is a derivative of Wogonin and the anticancer activities of Wogonin have been reported. To study whether LW-213 inhibits cancer cells and explore a possible mechanism, we investigate the compound in several cancer cell lines. We found LW-213 arrests G2/M cycle in breast cancer cells by suppression of Akt/Gsk3β/β-catenin signaling pathway. In compound treated cells, cell cycle-related proteins cyclin A, cyclin B1, p-CDK1, p-Cdc25C, and p-Chk2 (Thr68) were upregulated, and β-catenin nuclear translocation was inhibited. Electrophoretic mobility shift assay revealed LW-213 inhibits binding of β-catenin/LEF complex to DNA. GSK3β inhibitor LiCl and siRNA against GSK3β partially reversed G2/M arrest in breast cancer MCF-7 cells. These results suggest LW-213 triggered G2/M cell cycle arrest through suppression of β-catenin signaling. In BALB/c mice, growth of xenotransplanted MCF-7 tumor was also inhibited after treatment of LW-213. Regulation of cyclin A, cyclin B1, and β-catenin by LW-213 in vivo was the same as in vitro study. In conclusion, we found LW-213 exerts its anticancer effect on cell proliferation and cell cycle through repression of Akt/Gsk3β/β-catenin signaling pathway. LW-213 could be a potential candidate for anticancer drug development.

Xie Q, Wu Q, Mack SC, et al.
CDC20 maintains tumor initiating cells.
Oncotarget. 2015; 6(15):13241-54 [PubMed] Free Access to Full Article Related Publications
Glioblastoma is the most prevalent and lethal primary intrinsic brain tumor. Glioblastoma displays hierarchical arrangement with a population of self-renewing and tumorigenic glioma tumor initiating cells (TICs), or cancer stem cells. While non-neoplastic neural stem cells are generally quiescent, glioblastoma TICs are often proliferative with mitotic control offering a potential point of fragility. Here, we interrogate the role of cell-division cycle protein 20 (CDC20), an essential activator of anaphase-promoting complex (APC) E3 ubiquitination ligase, in the maintenance of TICs. By chromatin analysis and immunoblotting, CDC20 was preferentially expressed in TICs relative to matched non-TICs. Targeting CDC20 expression by RNA interference attenuated TIC proliferation, self-renewal and in vivo tumor growth. CDC20 disruption mediated its effects through induction of apoptosis and inhibition of cell cycle progression. CDC20 maintains TICs through degradation of p21CIP1/WAF1, a critical negative regulator of TICs. Inhibiting CDC20 stabilized p21CIP1/WAF1, resulting in repression of several genes critical to tumor growth and survival, including CDC25C, c-Myc and Survivin. Transcriptional control of CDC20 is mediated by FOXM1, a central transcription factor in TICs. These results suggest CDC20 is a critical regulator of TIC proliferation and survival, linking two key TIC nodes-FOXM1 and p21CIP1/WAF1-elucidating a potential point for therapeutic intervention.

Guha G, Lu W, Li S, et al.
Novel Pactamycin Analogs Induce p53 Dependent Cell-Cycle Arrest at S-Phase in Human Head and Neck Squamous Cell Carcinoma (HNSCC) Cells.
PLoS One. 2015; 10(5):e0125322 [PubMed] Free Access to Full Article Related Publications
Pactamycin, although putatively touted as a potent antitumor agent, has never been used as an anticancer drug due to its high cytotoxicity. In this study, we characterized the effects of two novel biosynthetically engineered analogs of pactamycin, de-6MSA-7-demethyl-7-deoxypactamycin (TM-025) and 7-demethyl-7-deoxypactamycin (TM-026), in head and neck squamous cell carcinoma (HNSCC) cell lines SCC25 and SCC104. Both TM-025 and TM-026 exert growth inhibitory effects on HNSCC cells by inhibiting cell proliferation. Interestingly, unlike their parent compound pactamycin, the analogs do not inhibit synthesis of nascent protein in a cell-based assay. Furthermore, they do not induce apoptosis or autophagy in a dose- or a time-dependent manner, but induce mild senescence in the tested cell lines. Cell cycle analysis demonstrated that both analogs significantly induce cell cycle arrest of the HNSCC cells at S-phase resulting in reduced accumulation of G2/M-phase cells. The pactamycin analogs induce expression of cell cycle regulatory proteins including master regulator p53, its downstream target p21Cip1/WAF1, p27kip21, p19, cyclin E, total and phospho Cdc2 (Tyr15) and Cdc25C. Besides, the analogs mildly reduce cyclin D1 expression without affecting expression of cyclin B, Cdk2 and Cdk4. Specific inhibition of p53 by pifithrin-α reduces the percentage of cells accumulated in S-phase, suggesting contribution of p53 to S-phase increase. Altogether, our results demonstrate that Pactamycin analogs TM-025 and TM-026 induce senescence and inhibit proliferation of HNSCC cells via accumulation in S-phase through possible contribution of p53. The two PCT analogs can be widely used as research tools for cell cycle inhibition studies in proliferating cancer cells with specific mechanisms of action.

Fukasawa T, Enomoto A, Miyagawa K
Serine-Threonine Kinase 38 regulates CDC25A stability and the DNA damage-induced G2/M checkpoint.
Cell Signal. 2015; 27(8):1569-75 [PubMed] Related Publications
Cells respond to DNA damage by activating protein kinase-mediated signaling pathways that promote cell-cycle arrest, DNA repair, or apoptosis. A key regulator of cell-cycle arrest is the CDC25A (cell division cycle 25 homologue A) phosphatase. CDC25A normally plays a pivotal role in regulating the G1/S and G2/M transitions by dephosphorylating and activating cyclin/cyclin-dependent kinase (CDK) complexes; however, CDC25A is specifically degraded in response to DNA damage. Here, we demonstrate that the depletion of serine-threonine kinase 38 (STK38) prevents the DNA-damage-induced degradation of CDC25A and subsequent G2 arrest, and that STK38 directly phosphorylates CDC25A at Ser-76, resulting in CDC25A's degradation. Taken together, these results indicate that the STK38-mediated phosphorylation of CDC25A at Ser-76 and the subsequent degradation of CDC25A are required to promote DNA damage-induced G2/M checkpoint activation.

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