Involvement of the role of Chk1 in lithium-induced G2/M phase cell cycle arrest in hepatocellular carcinoma cells

Exploring the mechanisms underlying the therapeutic effect of the Radix Bupleuri-Rhizoma Cyperi herb pair on hepatocellular carcinoma using multilevel data integration and molecular docking

Traditional Chinese medicine (TCM) is a promising and effective treatment for cancer with minimal side effects through a multi-active ingredient multitarget network. Radix Bupleuri and Rhizoma Cyperi are listed as herbs dispersing stagnated liver Qi in China. They have been used clinically to treat liver diseases for many years and recent pharmacological studies have shown that they inhibit the proliferation of hepatocellular carcinoma (HCC). However, the pharmacological mechanisms, potential targets, and clinical value of the Radix Bupleuri-Rhizoma Cyperi herb pair (CXP) for suppressing HCC growth have not been fully elucidated. We identified 44 CXP targets involved in the treatment of HCC using the GEO dataset and HERB database. An analysis of the Traditional Chinese Medicine System Pharmacology Database (TCMSP) showed that CXP exerts synergistic effects through 4 active ingredients, including quercetin, stigmasterol, isorhamnetin, and kaempferol. GO and KEGG analyses revealed that CXP mainly regulates HCC progression through metabolic pathways, the p53 signaling pathway, and the cell cycle. Additionally, we applied The Cancer Genome Atlas (TCGA)-liver hepatocellular carcinoma (LIHC) database to perform the expression patterns, clinical features, and prognosis of 6 genes (CCNB1, CDK1, CDK4, MYC, CDKN2A, and CHEK1) in cell cycle pathways to reveal that CXP suppresses HCC clinical therapeutic value. Moreover, based on molecular docking, we further verified that CXP exerts its anti-HCC activity through the interaction of multiple active components with cell cycle-related genes. We systematically revealed the potential pharmacological mechanisms and targets of CXP in HCC using multilevel data integration and molecular docking strategies.

Identification of Multiple Hub Genes and Pathways in Hepatocellular Carcinoma: A Bioinformatics Analysis

Hepatocellular carcinoma (HCC) is a common malignant tumor of the digestive system, and its early asymptomatic characteristic increases the difficulty of diagnosis and treatment. This study is aimed at obtaining some novel biomarkers with diagnostic and prognostic meaning and may find out potential therapeutic targets for HCC. We screen differentially expressed genes (DEGs) from the HCC gene expression profile GSE14520 using GEO2R. Gene Ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis were conducted by using the clusterProfiler software while a protein-protein interaction (PPI) network was performed based on the STRING database. Then, prognosis analysis of hub genes was conducted using The Cancer Genome Atlas (TCGA) database. Quantitative real-time polymerase chain reaction (qRT-PCR) was utilized to further verify the expression of hub genes and explore the correlation between gene expression and clinicopathological parameters. A total of 1053 DEGs were captured, containing 497 upregulated genes and 556 downregulated genes. GO and KEGG analysis indicated that the downregulated DEGs were mainly enriched in the fatty acid catabolic process while upregulated DEGs were primarily enriched in the cell cycle. Simultaneously, ten hub genes (CYP3A4, UGT1A6, AOX1, UGT1A4, UGT2B15, CDK1, CCNB1, MAD2L1, CCNB2, and CDC20) were identified by the PPI network. Five prognosis-related hub genes (CYP3A4, CDK1, CCNB1, MAD2L1, and CDC20) were uncovered by the survival analysis based on TCGA database. The ten hub genes were further validated by qRT-PCR using samples obtained from our hospital. The prognosis-related hub genes such as CYP3A4, CDK1, CCNB1, MAD2L1, and CDC20 could be considered potential diagnosis biomarkers and prognosis targets for HCC. We also use Oncomine for further verification, and we found CCNB1, CCNB2, CDK1, and CYP3A4 which were highly expressed in HCC. Meanwhile, CCNB1, CCNB2, and CDK1 are highly expressed in almost all cancer types, which may play an important role in cancer. Still, further functional study should be conducted to explore the underlying mechanism and biological effect in the near future.

The Role of Lithium in Management of Endocrine Tumors-A Comprehensive Review

Background: Epidemiological data reveal that treatment with lithium, a mood stabilizer, is associated with decreased incidence and mortality of certain cancer types, such as melanoma. Therefore, repositioning of lithium as an anticancer agent has emerged as a promising strategy in oncology. Since lithium affects the physiology of several endocrine tissues, the goal of this study was to analyze the role of lithium in the pathogenesis and treatment of tumors of the endocrine system. Methods: The databases of PubMed, EMBASE, MEDLINE, were searched from January 1970 through February 2019 for articles including the keywords "lithium and"-"thyroid cancer," "thyroid nodule," "parathyroid adenoma," "parathyroid carcinoma," "pituitary adenoma," "pituitary neuroendocrine tumor," "neuroendocrine tumor," "carcinoid," "adrenal adenoma," "adrenal carcinoma," "pheochromocytoma/paraganglioma." Preclinical in vitro and in vivo studies as well as case series, retrospective cohort studies and prospective trials were selected for the analysis. Results: Treatment with lithium has been associated with a higher prevalence of thyroid enlargement, hypothyroidism and increased calcium levels due to parathyroid adenoma or hyperplasia, as one of the mechanisms of its action is to stimulate proliferation of normal follicular thyroid and parathyroid cells via activation of the Wnt signaling pathway. Supratherapeutic concentrations of lithium decrease the activity of glycogen synthase kinase-3β (GSK-3β), leading to cell cycle arrest in several in vitro cancer models including medullary thyroid cancer (TC), pheochromocytoma/paraganglioma and carcinoid. Growth inhibitory effects of lithium in vivo have been documented in medullary TC xenograft mouse models. Clinically, lithium has been used as an adjuvant agent to therapy with radioactive iodine (RAI), as it increases the residence time of RAI in TC. Conclusion: Patients chronically treated with lithium need to be screened for hypothyroidism, goiter, and hyperparathyroidism, as the prevalence of these endocrine abnormalities is higher in lithium-treated patients than in the general population. The growth inhibitory effects of lithium in medullary TC, pheochromocytoma/paraganglioma and carcinoid were achieved with supratherapeutic concentrations of lithium thus limiting its translational perspective. Currently available clinical data on the efficacy of lithium in the therapy of endocrine tumors in human is limited and associated with conflicting results.

Potential role of microRNA‑223‑3p in the tumorigenesis of hepatocellular carcinoma: A comprehensive study based on data mining and bioinformatics

The aims of the present study were to examine the potential role of microRNA‑233‑3p (miR)‑223‑3p in the tumorigenesis of hepatocellular carcinoma (HCC), and to investigate its diagnostic accuracy and potential molecular mechanisms. The expression data of miR‑223‑3p in HCC were obtained from the Gene Expression Omnibus (GEO). Data for the precursor miR‑223 were obtained from The Cancer Genome Atlas (TCGA). The diagnostic role of miR‑223‑3p was identified by the receiver operating curve (ROC), and the diagnostic value of miR‑223‑3p in HCC was calculated from qualified reports in the literature. In addition, associated data from the GEO, TCGA and qualified experiments were pooled for comprehensive meta‑analysis. Genes, which intersected between online prediction databases, natural language processing and differentially expressed genes from TCGA were regarded as potential targets of miR‑223‑3p in HCC. The Gene Ontology enrichment analysis and the Kyoto Encyclopedia of Genes and Genomes pathways of potential targets were performed using the Database for Annotation, Visualization and Integrated Discovery. The protein‑protein interactions were mapped using the Search Tool for the Retrieval of Interacting Genes. Among 15 qualified microarray data sets from GEO, seven showed that a significantly lower level of miR‑223‑3p was present in the HCC tissues, compared with that in non‑cancerous tissues (P<0.05). In addition, five GEO data sets revealed diagnostic values of miR‑223‑3p, with an area under the curve (AUC) of >0.80 (P<0.05). The diagnostic accuracy of the precursor miR‑223 in TCGA was also calculated (AUC=0.78, P<0.05). Similarly, the precursor miR‑223 showed a higher level of downregulation in HCC tissues, compared with that in healthy controls in TCGA (P<0.001). A summary ROC was also calculated as 0.89 (95% CI, 0.85‑0.91) in the meta‑analysis. A total of 72 potential targets were extracted, mainly involved in the terms 'microRNAs in cancer', 'ATP binding' and 'prostate cancer'. Five potential target genes were considered the hub genes of miR‑223‑3p in HCC, including checkpoint kinase 1, DNA methyltransferase 1, baculoviral IAP repeat containing 5, kinesin family member 23, and collagen, type I, α1. Based on TCGA, the hub genes were significantly upregulated in HCC (P<0.05). Collectively, these results showed that miR‑223‑3p may be crucial in HCC carcinogenesis showing high diagnostic accuracy, and may be mediated by several hub genes.

A novel relationship for schizophrenia, bipolar and major depressive disorder Part 3: Evidence from chromosome 3 high density association screen

Familial clustering of schizophrenia (SCZ), bipolar disorder (BPD), and major depressive disorder (MDD) was systematically reported (Aukes et al, Genet Med 2012, 14, 338-341) and convergent evidence from genetics, symptomatology, and psychopharmacology imply that there are intrinsic connections between these three major psychiatric disorders, for example, any two or even three of these disorders could co-exist in some families. A total of 60, 838 single-nucleotide polymorphisms (SNPs) on chromosome 3 were genotyped by Affymetrix Genome-Wide Human SNP array 6.0 on 119 SCZ, 253 BPD (type-I), 177 MDD patients and 1,000 controls. The population of Shandong province was formed in 14 century and believed that it belongs to homogenous population. Associated SNPs were systematically revealed and outstanding susceptibility genes (CADPS, GRM7,KALRN, LSAMP, NLGN1, PRICKLE2, ROBO2) were identified. Unexpectedly, flanking genes for the associated SNPs distinctive for BPD and/or MDD were replicated in an enlarged cohort of 986 SCZ patients. The evidence from this chromosome 3 analysis supports the notion that both of bipolar and MDD might be subtypes of schizophrenia rather than independent disease entity. Also, a similar finding was detected on chromosome 5, 6, 7, and 8 (Chen et al. Am J Transl Res 2017;9 (5):2473-2491; Curr Mol Med 2016;16(9):840-854; Behav Brain Res 2015;293:241-251; Mol Neurobiol 2016. doi: 10.1007/s12035-016-0102-1). Furthermore, PRICKLE2 play an important role in the pathogenesis of three major psychoses in this population.

Tumour growth environment modulates Chk1 signalling pathways and Chk1 inhibitor sensitivity

Clinical development of Chk1 inhibitors is currently focussed on evaluating activity as monotherapy and as potentiators of chemotherapy. To aid translation of pre-clinical studies, we sought to understand the effects of the tumour growth environment on Chk1 signalling and sensitivity to small molecule Chk1 inhibition. Spheroid culture altered Chk1 signalling to a more xenograft like state but decreased sensitivity to Chk1 inhibition. Growth in low serum did not alter DDR signalling but increased the sensitivity of A2058 and U2OS tumour cells to Chk1 inhibition. An analysis of the expression levels of replication associated proteins identified a correlation between Cdc6 and pChk1 (S296) as well as total Chk1 in xenograft derived samples and between Cdc6 and total Chk1 in anchorage-dependent growth derived protein samples. No apparent correlation between Chk1 or Cdc6 expression and sensitivity to Chk1 inhibition in vitro was observed. A database analysis revealed upregulation of CDC6 mRNA expression in tumour compared to normal tissue and a correlation between CDC6 and CHEK1 mRNA expression in human cancers. We suggest that Cdc6 overexpression in human tumours requires a concomitant increase in Chk1 to counterbalance the deleterious effects of origin hyperactivation-induced DNA damage.

Effect of lithium chloride on cell proliferation and osteogenic differentiation in stem cells from human exfoliated deciduous teeth

Lithium Chloride (LiCl) has been used as a canonical Wnt pathway activator due to its ability to inhibit a glycogen synthase kinase-3. The aim of the present study was to investigate the effect of LiCl on cell proliferation and osteogenic differentiation in stem cells isolated from human exfoliated deciduous teeth (SHEDs). SHEDs were isolated and cultured in media supplemented with LiCl at 5, 10, or 20mM. The results demonstrated that LiCl significantly decreased SHEDs colony forming unit ability in a dose dependent manner. LiCl significantly enhanced the percentage of cells in the sub G0 phase, accompanied by a reduction of the percentage of cells in the G1 phase at day 3 and 7 after treatment. Further, LiCl markedly decreased OSX and DMP1 mRNA expression after treating SHEDs in an osteogenic induction medium for 7 days. In addition, no significant difference in alkaline phosphatase enzymatic activity or mineral deposition was found. Together, these results imply that LiCl influences SHEDs behavior.

Lithium-induced developmental anomalies in the spirotrich ciliate Stylonychia lemnae (Ciliophora, Hypotrichida)

Lithium is known to have profound biological effects of varying intensity in different life forms. In the present investigation, the effect of lithium was studied on the spirotrich ciliate Stylonychia lemnae. Lithium treatment brings about quantitative changes in the patterning of ciliary structures in S. lemnae. The dorsal surface of the affected cells develops supernumerary ciliary kineties due to excessive proliferation of the kinetosomes. The ventral surface on the other hand develops fewer than normal cirri formed from reduced numbers of ciliary primordia. The adoral zone of membranelles (AZM) fails to remodel properly as, in certain segments, membranelles become disarranged and misaligned. Lithium-induced changes are transitory as the normal pattern is restored during recovery after the cells are shifted to normal medium, suggesting non-genic regulation of cortical pattern. Lithium also affects the process of cell proliferation as the number of cells undergoing division is negligible as compared to reorganizing cells. The results point to the extremely complex and heterogeneous organization of the cellular cortex (plasma membrane and cytoskeleton) which is capable of exerting autonomous control over the phenotype and cortical pattern.

Lithium Chloride Promotes Apoptosis in Human Leukemia NB4 Cells by Inhibiting Glycogen Synthase Kinase-3 Beta

Acute promyelocytic leukemia (APL) is a subtype of acute myeloid leukemia (AML). With the application of all-trans retinoic acid (ATRA) and arsenic trioxide (ATO), APL becomes one of best prognosis of leukemia. However, ATRA and ATO are not effective against all APLs. Therefore, a new strategy for APL treatment is necessary. Here, we investigated whether lithium chloride (LiCl), a drug used for the treatment of mental illness, could promote apoptosis in human leukemia NB4 cells. We observed that treatment with LiCl significantly accelerated apoptosis in NB4 cells and led to cell cycle arrest at G2/M phase. Moreover, LiCl significantly increased the level of Ser9-phosphorylated glycogen synthase kinase 3β(p-GSK-3β), and decreased the level of Akt1 protein in a dose-dependent manner. In addition, LiCl inhibition of c-Myc also enhanced cell death with a concomitant increase in β-catnin. Taken together, these findings demonstrated that LiCl promoted apoptosis in NB4 cells through the Akt signaling pathway and that G2/M phase arrest was induced by increase of p-GSK-3β(S9).

Transcriptional and functional complexity of Shank3 provides a molecular framework to understand the phenotypic heterogeneity of SHANK3 causing autism and Shank3 mutant mice

Background

Considerable clinical heterogeneity has been well documented amongst individuals with autism spectrum disorders (ASD). However, little is known about the biological mechanisms underlying phenotypic diversity. Genetic studies have established a strong causal relationship between ASD and molecular defects in the SHANK3 gene. Individuals with various defects of SHANK3 display considerable clinical heterogeneity. Different lines of Shank3 mutant mice with deletions of different portions of coding exons have been reported recently. Variable synaptic and behavioral phenotypes have been reported in these mice, which makes the interpretations for these data complicated without the full knowledge of the complexity of the Shank3 transcript structure.

Methods

We systematically examined alternative splicing and isoform-specific expression of Shank3 across different brain regions and developmental stages by regular RT-PCR, quantitative real time RT-PCR (q-PCR), and western blot. With these techniques, we also investigated the effects of neuronal activity and epigenetic modulation on alternative splicing and isoform-specific expression of Shank3. We explored the localization and influence on dendritic spine development of different Shank3 isoforms in cultured hippocampal neurons by cellular imaging.

Results

The Shank3 gene displayed an extensive array of mRNA and protein isoforms resulting from the combination of multiple intragenic promoters and extensive alternative splicing of coding exons in the mouse brain. The isoform-specific expression and alternative splicing of Shank3 were brain-region/cell-type specific, developmentally regulated, activity-dependent, and involved epigenetic regulation. Different subcellular distribution and differential effects on dendritic spine morphology were observed for different Shank3 isoforms.

Conclusions

Our results indicate a complex transcriptional regulation of Shank3 in mouse brains. Our analysis of select Shank3 isoforms in cultured neurons suggests that different Shank3 isoforms have distinct functions. Therefore, the different types of SHANK3 mutations found in patients with ASD and different exonic deletions of Shank3 in mutant mice are predicted to disrupt selective isoforms and result in distinct dysfunctions at the synapse with possible differential effects on behavior. Our comprehensive data on Shank3 transcriptional regulation thus provides an essential molecular framework to understand the phenotypic diversity in SHANK3 causing ASD and Shank3 mutant mice.

Chk1, but not Chk2, is responsible for G2/M phase arrest induced by diallyl disulfide in human gastric cancer BGC823 cells

Diallyl disulfide (DADS) has been shown to cause G2/M phase cell cycle arrest in several human cancers. Here we demonstrate a mechanism by which DADS induces G2/M phase arrest in BGC823 human gastric cancer cells via Chk1. From cell cycle gene array results, we next confirmed that cyclin B1 expression was decreased by DADS, while the expression of p21, GADD45α and p53 were increased. Despite the lack of change in Chk1 gene expression in response to DADS according to the array analysis, intriguingly overexpression of Chk1, but not Chk2, exhibited increased accumulation in G2/M phase. Moreover, overexpression of Chk1 promoted the effect of DADS-induced G2/M arrest. Augmented phosphorylation of Chk1 by DADS was observed in Chk1-transfected cells, followed by downregulation of Cdc25C and cyclin B1 proteins. In contrast, phosphorylated Chk2 showed no obvious change in Chk2-transfected cells after DADS treatment. Furthermore, knockdown of Chk1 by siRNA partially abrogated DADS-induced downregulation of Cdc25C and cyclin B1 proteins and G2/M arrest. In contrast, knockdown of Chk2 did not show these effects. Therefore, these data indicate that DADS may specifically modulate Chk1 phosphorylation, and DADS-induced G2/M phase arrest in BGC823 cells could result in part from Chk1-mediated inhibition of the Cdc25C/cyclin B1 pathway.

Lithium causes G2 arrest of renal principal cells

Vasopressin-regulated expression and insertion of aquaporin-2 channels in the luminal membrane of renal principal cells is essential for urine concentration. Lithium affects urine concentrating ability, and approximately 20% of patients treated with lithium develop nephrogenic diabetes insipidus (NDI), a disorder characterized by polyuria and polydipsia. Lithium-induced NDI is caused by aquaporin-2 downregulation and a reduced ratio of principal/intercalated cells, yet lithium induces principal cell proliferation. Here, we studied how lithium-induced principal cell proliferation can lead to a reduced ratio of principal/intercalated cells using two-dimensional and three-dimensional polarized cultures of mouse renal collecting duct cells and mice treated with clinically relevant lithium concentrations. DNA image cytometry and immunoblotting revealed that lithium initiated proliferation of mouse renal collecting duct cells but also increased the G2/S ratio, indicating G2/M phase arrest. In mice, treatment with lithium for 4, 7, 10, or 13 days led to features of NDI and an increase in the number of principal cells expressing PCNA in the papilla. Remarkably, 30%-40% of the PCNA-positive principal cells also expressed pHistone-H3, a late G2/M phase marker detected in approximately 20% of cells during undisturbed proliferation. Our data reveal that lithium treatment initiates proliferation of renal principal cells but that a significant percentage of these cells are arrested in the late G2 phase, which explains the reduced principal/intercalated cell ratio and may identify the molecular pathway underlying the development of lithium-induced renal fibrosis.

S100A8/A9 (calprotectin) negatively regulates G2/M cell cycle progression and growth of squamous cell carcinoma

Malignant transformation results in abnormal cell cycle regulation and uncontrolled growth in head and neck squamous cell carcinoma (HNSCC) and other cancers. S100A8/A9 (calprotectin) is a calcium-binding heterodimeric protein complex implicated in cell cycle regulation, but the specific mechanism and role in cell cycle control and carcinoma growth are not well understood. In HNSCC, S100A8/A9 is downregulated at both mRNA and protein levels. We now report that downregulation of S100A8/A9 correlates strongly with a loss of cell cycle control and increased growth of carcinoma cells. To show its role in carcinogenesis in an in vitro model, S100A8/A9 was stably expressed in an S100A8/A9-negative human carcinoma cell line (KB cells, HeLa-like). S100A8/A9 expression increases PP2A phosphatase activity and p-Chk1 (Ser345) phosphorylation, which appears to signal inhibitory phosphorylation of mitotic p-Cdc25C (Ser216) and p-Cdc2 (Thr14/Tyr15) to inactivate the G2/M Cdc2/cyclin B1 complex. Cyclin B1 expression then downregulates and the cell cycle arrests at the G2/M checkpoint, reducing cell division. As expected, S100A8/A9-expressing cells show both decreased anchorage-dependent and -independent growth and mitotic progression. Using shRNA, silencing of S100A8/A9 expression in the TR146 human HNSCC cell line increases growth and survival and reduces Cdc2 inhibitory phosphorylation at Thr14/Tyr15. The level of S100A8/A9 endogenous expression correlates strongly with the reduced p-Cdc2 (Thr14/Tyr14) level in HNSCC cell lines, SCC-58, OSCC-3 and UMSCC-17B. S100A8/A9-mediated control of the G2/M cell cycle checkpoint is, therefore, a likely suppressive mechanism in human squamous cell carcinomas and may suggest new therapeutic approaches.

Lithium enhances TRAIL-induced apoptosis in human lung carcinoma A549 cells

Non-small cell lung cancer (NSCLC) A549 cells are resistant to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis. Therefore, combination therapy using sensitizing agents to overcome TRAIL resistance may provide new strategies for treatment of NSCLC. Here, we investigated whether lithium chloride (LiCl), a drug for mental illness, could sensitize A549 cells to TRAIL-induced apoptosis. We observed that LiCl significantly enhanced A549 cells apoptosis through up-regulation of death receptors DR4 and DR5 and activation of caspase cascades. In addition, G2/M arrest induced by LiCl also contributed to TRAIL-induced apoptosis. Concomitantly, LiCl strongly inhibited the activity of c-Jun N-terminal kinases (JNKs), and the inhibition of JNKs by SP600125 also induced G2/M arrest and augmented cell death caused by TRAIL or TRAIL plus LiCl. However, glycogen synthase kinase-3β (GSK3β) inhibition was not involved in TRAIL sensitization induced by LiCl. Collectively, these findings indicated that LiCl sensitized A549 cells to TRAIL-induced apoptosis through caspases-dependent apoptotic pathway via death receptors signaling and G2/M arrest induced by inhibition of JNK activation, but independent of GSK3β.

Zygotic G2/M cell cycle arrest induced by ATM/Chk1 activation and DNA repair in mouse embryos fertilized with hydrogen peroxide-treated epididymal mouse sperm

Human sperm cryopreservation for assisted reproduction is compromised by ROS-induced sperm cryodamage. Our previous model study in which mouse sperm were treated with H₂O₂ to simulate sperm DNA-damage caused by cryopreservation-induced ROS have discovered that mouse embryos fertilized with treated sperm showed a delay in cleavage that might be associated with cell cycle arrest. The DNA-damage checkpoint pathway underlying the delay remained elusive. Moreover, our previous study have also indicated that γH2AX, the DNA-damage repair marker, was functional in mouse embryos similarly fertilized, but the completeness and correctness are unknown and warrant more studies because insufficiency of completeness and correctness of DNA repair would otherwise trigger apoptosis. Based on the aforementioned model, we used embryo culture, inverted microscope, BrdU incorporation and immunofluorescence to explore the cell cycle phase that arrest occurred and the underlying DNA-damage checkpoint pathway in mouse zygotes fertilized with H₂O₂-treated sperm. We also adopted Tunel to investigate the apoptosis of mouse embryos similarly fertilized at different developmental stages to testify the completeness and correctness of sperm-derived DNA-damage repair. We found G2/M cell cycle arrest in zygotes fertilized with H₂O₂-treated sperm. ATM (pSer-1981) and Chk1 (pSer-345) activations, rather than ATR (pSer-428) and Chk2 (pThr-68), were detected in zygotes of the treated group. The apoptosis of embryos of different developmental stages of the treated group weren't different from those of the untreated group. In conclusions, ATM (pSer-1981)-Chk1 (pSer-345) cascade might have mediated G2/M cell cycle arrest and allowed time to facilitate sperm-derived DNA-damage repair in mouse zygotes fertilized with oxygen-stressed sperm, and the DNA-damage repair might be effective.

Effects of SASH1 on melanoma cell proliferation and apoptosis in vitro

The SAM and SH3 domain containing 1 (SASH1) gene was originally identified as a potential tumor suppressor gene in breast cancer, mapped on chromosome 6q24.3. The expression of SASH1 plays a prognostic role in human colon cancer. Its expression is frequently downregulated in several human malignancies. However, the biological function of SASH1 in melanoma cells is yet to be determined. In this study, in order to investigate the tumor suppressive effects of the SASH1 gene, an A-375 stable melanoma cell line was established, overexpressing the SASH1 gene. The stable cell line was examined using proliferation assay, apoptosis assay, cell cycle analysis and real-time PCR. The results indicated that the tumor suppressive activity of SASH1 derived from G2/M arrest in A-375 cells, and that the phosphorylation of Cdc2 or the disruption of cyclin B-Cdc2 binding may be responsible for the G2/M arrest.

Effects of Wnt/β-catenin signalling on proliferation and differentiation of apical papilla stem cells

OBJECTIVES

The Wnt signalling pathway has been shown to play an important role in tooth development, however its effects with stem cells from the apical papilla (SCAP) have remained unclear. The purpose of this study was to determine effects of Wnt/β-catenin on proliferation and differentiation of SCAP in vitro.

MATERIALS AND METHODS

SCAP were obtained, identified and cultured. Cell proliferation, alkaline phosphatase (ALP) activity, mRNA expression of mineralization-related genes and mineralized nodule formation were measured in presence or absence of various concentrations of lithium chloride.

RESULTS

MTT assay and flow cytometry demonstrated that Wnt/β-catenin activity could promote proliferation of SCAP. Real-time PCR analysis found that Wnt/β-catenin strongly upregulated expression of dentine sialophosphoprotein, osteocalcin and ALP in SCAP after incubation with mineralization induction medium, while ALP and alizarin red staining indicated that Wnt/β-catenin enhanced ALP activity and formation of mineralized nodules.

CONCLUSION

Our results suggest that canonical Wnt/β-catenin signalling promotes proliferation and odonto/osteogenic differentiation of SCAP.

N-acetyl cysteine and penicillamine induce apoptosis via the ER stress response-signaling pathway

N-acetyl cysteine (NAC) and penicillamine (PEN) have been shown to induce apoptosis in multiple types of human cancer cells; however, the molecular mechanism underlying this activity is unclear. This study was designed to identify the genes responsible for apoptosis induction by NAC and PEN. We found that glucose-regulated protein 78 (GRP78) was upregulated in HeLa cells following treatment with NAC or PEN. GRP78 is a central regulator of endoplasmic reticulum (ER) stress and has been used as a marker of ER stress. Additionally, both the activating transcription factor 6 (ATF6) protein and X box-binding protein 1 (XBP1) mRNA were processed, which facilitates the expression of C/EBP homologous protein (CHOP), a key-signaling component of ER stress-induced apoptosis. Furthermore, the PERK-ATF4 pathway, which also induces the expression of CHOP, was activated in NAC-treated cells. The role of the ER stress pathway was further confirmed through the small interfering RNA (siRNA)-mediated knockdown of CHOP, which attenuated NAC and PEN-induced apoptosis. These results demonstrate that NAC- and PEN-induced apoptosis in HeLa cells is mediated by the ER stress pathway.

Lithium-mediated protection of hippocampal cells involves enhancement of DNA-PK-dependent repair in mice

Long-term neurological deficiencies resulting from hippocampal cytotoxicity induced by cranial irradiation (IR) present a challenge in the treatment of primary and metastatic brain cancers, especially in children. Previously, we showed that lithium protected hippocampal neurons from IR-induced apoptosis and improved neurocognitive function in treated mice. Here, we demonstrate accelerated repair of IR-induced chromosomal double-strand breaks (DSBs) in lithium-treated neurons. Lithium treatment not only increased IR-induced DNA-dependent protein kinase (DNA-PK) threonine 2609 foci, a surrogate marker for activated nonhomologous end-joining (NHEJ) repair, but also enhanced double-strand DNA end-rejoining activity in hippocampal neurons. The increased NHEJ repair coincided with reduced numbers of IR-induced gamma-H2AX foci, well-characterized in situ markers of DSBs. These findings were confirmed in vivo in irradiated mice. Consistent with a role of NHEJ repair in lithium-mediated neuroprotection, attenuation of IR-induced apoptosis of hippocampal neurons by lithium was dramatically abrogated when DNA-PK function was abolished genetically in SCID mice or inhibited biochemically by the DNA-PK inhibitor IC86621. Importantly, none of these findings were evident in glioma cancer cells. These results support our hypothesis that lithium protects hippocampal neurons by promoting the NHEJ repair-mediated DNA repair pathway and warrant future investigation of lithium-mediated neuroprotection during cranial IR, especially in the pediatric population.

Activation of ATM/Chk1 by curcumin causes cell cycle arrest and apoptosis in human pancreatic cancer cells

Curcumin has been shown to inhibit the growth of various types of cancer cells; however, at concentrations much above the clinically achievable levels in humans. The concentration of curcumin achieved in the plasma after oral administration in humans was estimated to be around 1.8 μM. Here, we report that treatment of BxPC-3 human pancreatic cancer cells with a low and single exposure of 2.5 μM curcumin for 24 h causes significant arrest of cells in the G2/M phase and induces significant apoptosis. Immunoblot studies revealed increased phosphorylation of H2A.X at Ser-139 and Chk1 at Ser-280 and a decrease in DNA polymerase-β level in curcumin-treated cells. Phosphorylation of H2A.X and Chk1 proteins are an indicator of DNA damage whereas DNA polymerase-β plays a role in the repair of DNA strand breaks. Normal immortalised human pancreatic ductal epithelial (HPDE-6) cells remained unaffected by curcumin treatment. In addition, we also observed a significant increase in the phosphorylation of Chk1 at Ser-345, Cdc25C at Ser-216 and a subtle increase in ATM phosphorylation at Ser-1981. Concomitant decrease in the expressions of cyclin B1 and Cdk1 were seen in curcumin-treated cells. Further, curcumin treatment caused significant cleavage of caspase-3 and PARP in BxPC-3 but not in HPDE-6 cells. Silencing ATM/Chk1 expression by transfecting BxPC-3 cells with ATM or Chk1-specific SiRNA blocked the phosphorylation of ATM, Chk1 and Cdc25C and protected the cells from curcumin-mediated G2/M arrest and apoptosis. This study reflects the critical role of ATM/Chk1 in curcumin-mediated G2/M cell cycle arrest and apoptosis in pancreatic cancer cells.