Cyclin H Regulates Lung Cancer Progression as a Carcinoma Inducer.

INTRODUCTION: Studies have previously shown that Cyclin H (CCNH) is involved in the tumorigenesis and development of many cancers. The increasing research in CCNH is associated with the poor prognosis of most human cancers. Early diagnosis and clinical treatment are still the main challenges for lung cancer treatment. However, the exact role of CCNH in the tumorigenesis of lung cancer remains unclear. METHODS: The Tumor Genome Atlas (TCGA) database and the Clinical Proteomics Tumor Analysis Association (CPTAC) database were analyzed to detect key genes that might play an important role in lung cancer. The biological functions of CCNH were further revealed through bioinformatics experiments. The Kaplan-Meier method was applied to explore the relationship between CCNH expression and prognosis. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was used to detect the expression levels of CCNH in 6 lung cancer tissues and 3 cancer cell lines. The effect of CCNH expression on lung cancer progression was studied by in vitro functional experiments. RESULTS: Database analysis screened out candidate oncogenes, and CCNH was of great significance to the tumorigenesis of lung cancer. The higher the expression of CCNH was, the lower the survival rate of lung cancer patients were. The qRT-PCR data illustrated that the CCNH expression level was largely increased in lung cancer tissues and cells. The reduction of CCNH inhibited cell proliferation, invasion, and migration. CONCLUSION: CCNH was related to poor prognosis, suggesting that CCNH regulated the tumorigenesis and development of lung cancer. Our study suggested that CCNH was a promising biomarker and target in the treatment of lung cancer.

Thyroid Cancer: The Quest for Genetic Susceptibility Involving DNA Repair Genes.

The incidence of thyroid cancer (TC), particularly well-differentiated forms (DTC), has been rising and remains the highest among endocrine malignancies. Although ionizing radiation (IR) is well established on DTC aetiology, other environmental and genetic factors may also be involved. DNA repair single nucleotide polymorphisms (SNPs) could be among the former, helping in explaining the high incidence. To further clarify the role of DNA repair SNPs in DTC susceptibility, we analyzed 36 SNPs in 27 DNA repair genes in a population of 106 DTCs and corresponding controls with the aim of interpreting joint data from previously studied isolated SNPs in DNA repair genes. Significant associations with DTC susceptibility were observed for XRCC3 rs861539, XPC rs2228001, CCNH rs2230641, MSH6 rs1042821 and ERCC5 rs2227869 and for a haplotype block on chromosome 5q. From 595 SNP-SNP combinations tested and 114 showing relevance, 15 significant SNP combinations (p < 0.01) were detected on paired SNP analysis, most of which involving CCNH rs2230641 and mismatch repair variants. Overall, a gene-dosage effect between the number of risk genotypes and DTC predisposition was observed. In spite of the volume of data presented, new studies are sought to provide an interpretability of the role of SNPs in DNA repair genes and their combinations in DTC susceptibility.

Cyclins B1, T1, and H differ in their molecular mode of interaction with cytomegalovirus protein kinase pUL97.

Human cytomegalovirus (HCMV) is a common ß-herpesvirus causing life-long latent infections. HCMV replication interferes with cell cycle regulation in host cells because the HCMV-encoded cyclin-dependent kinase (CDK) ortholog pUL97 extensively phosphorylates the checkpoint regulator retinoblastoma protein. pUL97 also interacts with cyclins B1, T1, and H, and recent findings have strongly suggested that these interactions influence pUL97 substrate recognition. Interestingly, here we detected profound mechanistic differences among these pUL97-cyclin interactions. Our study revealed the following. (i) pUL97 interacts with cyclins B1 and H in a manner dependent on pUL97 activity and HCMV-specific cyclin modulation, respectively. (ii) The phosphorylated state of both proteins is an important determinant of the pUL97-cyclin B1 interaction. (iii) Activated phospho-Thr-315 cyclin H is up-regulated during HCMV replication. (iv) Thr-315 phosphorylation is independent of intracellular pUL97 or CDK7 activity. (v) pUL97-mediated in vitro phosphorylation is detectable for cyclin B1 but not H. (vi) Mutual transphosphorylation between pUL97 and CDK7 is not detectable, and an MS-based phosphosite analysis indicated that pUL97 might unexpectedly not be phosphorylated in its T-loop. (vii) The binary complexes pUL97-cyclin H and CDK7-cyclin H as well as the ternary complex pUL97-cyclin-H-CDK7 are detectable in an assembly-based CoIP approach. (viii) pUL97 self-interaction can be bridged by the transcriptional cyclins T1 or H but not by the classical cell cycle-regulating B1 cyclin. Combined, our findings unravel a number of cyclin type-specific differences in pUL97 interactions and suggest a multifaceted regulatory impact of cyclins on HCMV replication.

Mechanistic insights into avian reovirus p17-modulated suppression of cell cycle CDK-cyclin complexes and enhancement of p53 and cyclin H interaction.

The avian reovirus p17 protein is a nucleocytoplasmic shuttling protein. Although we have demonstrated that p17 causes cell growth retardation via activation of p53, the precise mechanisms remain unclear. This is the first report that avian reovirus p17 possesses broad inhibitory effects on cell cycle CDKs, cyclins, CDK-cyclin complexes, and CDK-activating kinase activity in various mammalian, avian, and cancer cell lines. Suppression of CDK activity by p17 occurs by direct binding to CDKs, cyclins, and CDK-cyclin complexes; transcriptional down-regulation of CDKs; cytoplasmic retention of CDKs and cyclins; and inhibition of CDK-activating kinase activity by promoting p53-cyclin H interaction. p17 binds to CDK-cyclin except for CDK1-cyclin B1 and CDK7-cyclin H complexes. We have determined that the negatively charged 151LAVXDVDA(E/D)DGADPN165 motif in cyclin B1 interacts with a positively charged region of CDK1. p17 mimics the cyclin B1 sequence to compete for CDK1 binding. The PSTAIRE motif is not required for interaction of CDK1-cyclin B1, but it is required for other CDK-cyclin complexes. p17 interacts with cyclins by its cyclin-binding motif, 125RXL127 Sequence and mutagenic analyses of p17 indicated that a 140WXFD143 motif and residues Asp-113 and Lys-122 in p17 are critical for CDK2 and CDK6 binding, leading to their sequestration in the cytoplasm. Exogenous expression of p17 significantly enhanced virus replication, whereas p17 mutants with low binding ability to cell cycle CDKs had no effect on virus yield, suggesting that p17 inhibits cell growth and the cell cycle, benefiting virus replication. An in vivo tumorigenesis assay also showed a significant reduction in tumor size.

Genetic polymorphisms in cyclin H gene are associated with oxaliplatin-induced acute peripheral neuropathy in South Indian digestive tract cancer patients.

PURPOSE: Digestive tract cancer patients treated with oxaliplatin are often associated with the development of peripheral neuropathy. The aim of the present study is to identify the influence of single-nucleotide polymorphisms (SNPs) in genes involved in oxaliplatin metabolism, cell cycle control, detoxification or excretion pathways with the development of oxaliplatin-induced acute peripheral neuropathy (acute OXAIPN) and its severity among digestive tract cancer patients treated with oxaliplatin-based chemotherapy. PATIENTS AND METHODS: A total of 228 digestive tract cancer patients undergoing with the oxaliplatin-based chemotherapy between November 2014 and December 2016 were included in the current study. Genomic DNA was extracted from peripheral blood by standard phenol-chloroform method. Genotyping of five SNPs in four genes [GSTP1 (rs1965), ABCG2 (rs3114018), CCNH (rs2230641, rs3093816), AGXT (rs4426527)] was carried out by Real-Time TaqMan SNP genotyping assay. RESULTS: We found that the two genetic variants rs2230641 and rs3093816 in cyclin H (CCNH) gene were significantly associated with both the incidence and severity of acute OXAIPN. For CCNH-rs2230641 (AA vs AG+GG; dominant model) Incidence: OR 2.62, 95% CI 1.44-4.75, p = 0.001, severity; OR 4.64, 95% CI 1.58-13.62, p = 0.002. For CCNH-rs3093816 (AA vs AG+GG; dominant model); incidence: OR 3.43, 95% CI 1.57-7.50, p = 0.001; severity: OR 2.36, 95% CI 1.05-5.30, p = 0.033. CONCLUSIONS: The results of the present study found significant association between CCNH polymorphisms and acute OXAIPN development. However, further studies are warranted from independent groups to validate our study results.

Traditional Chinese Medicine Curcumin Sensitizes Human Colon Cancer to Radiation by Altering the Expression of DNA Repair-related Genes.

BACKGROUND/AIM: The aim of the present study was to investigate the radio-sensitizing efficacy of curcumin, a traditional Chinese medicine (TCM) on colon cancer cells in vitro and in vivo. MATERIALS AND METHODS: Human colon cancer HT-29 cells were treated with curcumin (2.5 µM), irradiation (10 Gy) and the combination of irradiation and curcumin. Cell proliferation was assessed using the MTT assay. Apoptotic cells were detected by Annexin V-PE/7-AAD analysis. PCR was performed to determine differential-expression profiling of 95 DNA-repair genes in irradiated cells and cells treated with both irradiation and curcumin. Differentially-expressed genes were confirmed by Western blotting. In vivo radio-sensitizing efficacy of curcumin was assessed in a xenograft mouse model of HT-29 colon cancer. Curcumin was administrated daily by intraperitoneal injection at 20 mg/kg/dose. Mice received irradiation (10 Gy) twice weekly. Apoptosis of the cancer cells following treatment was determined by TUNEL staining. RESULTS: Irradiation induced proliferation inhibition and apoptosis of HT-29 cells in vitro. Concurrent curcumin treatment sensitized the HT-29 tumor to irradiation (p<0.01). DNA repair-related genes CCNH and XRCC5 were upregulated and LIG4 and PNKP downregulated by the combination of curcumin and irradiation compared with irradiation alone (p<0.05). Combined treatment of curcumin and irradiation resulted in a significantly greater tumor-growth inhibition and apoptosis compared to irradiation treatment alone (p<0.01). CONCLUSION: Curcumin sensitizes human colon cancer in vitro and in vivo to radiation. Downregulation of LIG4 and PNKP and upregulation of XRCC5 and CCNH DNA-repair-related genes were involved in the radio-sensitizing efficacy of curcumin in colon cancer.

Contextualization of drug-mediator relations using evidence networks.

BACKGROUND: Genomic analysis of drug response can provide unique insights into therapies that can be used to match the "right drug to the right patient." However, the process of discovering such therapeutic insights using genomic data is not straightforward and represents an area of active investigation. EDDY (Evaluation of Differential DependencY), a statistical test to detect differential statistical dependencies, is one method that leverages genomic data to identify differential genetic dependencies. EDDY has been used in conjunction with the Cancer Therapeutics Response Portal (CTRP), a dataset with drug-response measurements for more than 400 small molecules, and RNAseq data of cell lines in the Cancer Cell Line Encyclopedia (CCLE) to find potential drug-mediator pairs. Mediators were identified as genes that showed significant change in genetic statistical dependencies within annotated pathways between drug sensitive and drug non-sensitive cell lines, and the results are presented as a public web-portal (EDDY-CTRP). However, the interpretability of drug-mediator pairs currently hinders further exploration of these potentially valuable results. METHODS: In this study, we address this challenge by constructing evidence networks built with protein and drug interactions from the STITCH and STRING interaction databases. STITCH and STRING are sister databases that catalog known and predicted drug-protein interactions and protein-protein interactions, respectively. Using these two databases, we have developed a method to construct evidence networks to "explain" the relation between a drug and a mediator.  RESULTS: We applied this approach to drug-mediator relations discovered in EDDY-CTRP analysis and identified evidence networks for ~70% of drug-mediator pairs where most mediators were not known direct targets for the drug. Constructed evidence networks enable researchers to contextualize the drug-mediator pair with current research and knowledge. Using evidence networks, we were able to improve the interpretability of the EDDY-CTRP results by linking the drugs and mediators with genes associated with both the drug and the mediator. CONCLUSION: We anticipate that these evidence networks will help inform EDDY-CTRP results and enhance the generation of important insights to drug sensitivity that will lead to improved precision medicine applications.

Expression of CDK7, Cyclin H, and MAT1 Is Elevated in Breast Cancer and Is Prognostic in Estrogen Receptor-Positive Breast Cancer.

PURPOSE: CDK-activating kinase (CAK) is required for the regulation of the cell cycle and is a trimeric complex consisting of cyclin-dependent kinase 7 (CDK7), Cyclin H, and the accessory protein, MAT1. CDK7 also plays a critical role in regulating transcription, primarily by phosphorylating RNA polymerase II, as well as transcription factors such as estrogen receptor-α (ER). Deregulation of cell cycle and transcriptional control are general features of tumor cells, highlighting the potential for the use of CDK7 inhibitors as novel cancer therapeutics. EXPERIMENTAL DESIGN: mRNA and protein expression of CDK7 and its essential cofactors cyclin H and MAT1 were evaluated in breast cancer samples to determine if their levels are altered in cancer. Immunohistochemical staining of >900 breast cancers was used to determine the association with clinicopathologic features and patient outcome. RESULTS: We show that expressions of CDK7, cyclin H, and MAT1 are all closely linked at the mRNA and protein level, and their expression is elevated in breast cancer compared with the normal breast tissue. Intriguingly, CDK7 expression was inversely proportional to tumor grade and size, and outcome analysis showed an association between CAK levels and better outcome. Moreover, CDK7 expression was positively associated with ER expression and in particular with phosphorylation of ER at serine 118, a site important for ER transcriptional activity. CONCLUSIONS: Expressions of components of the CAK complex, CDK7, MAT1, and Cyclin H are elevated in breast cancer and correlate with ER. Like ER, CDK7 expression is inversely proportional to poor prognostic factors and survival. Clin Cancer Res; 22(23); 5929-38. ©2016 AACR.

Binding Pattern Elucidation of NNK and NNAL Cigarette Smoke Carcinogens with NER Pathway Enzymes: an Onco- Informatics Study.

Cigarette smoke derivatives like NNK (4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone) and NNAL (4-(methylnitrosamino)-1-(3-pyridyl)-1-butan-1-ol) are well-known carcinogens. We analyzed the interaction of enzymes involved in the NER (nucleotide excision repair) pathway with ligands (NNK and NNAL). Binding was characterized for the enzymes sharing equivalent or better interaction as compared to +Ve control. The highest obtained docking energy between NNK and enzymes RAD23A, CCNH, CDK7, and CETN2 were -7.13 kcal/mol, -7.27 kcal/mol, -8.05 kcal/mol and -7.58 kcal/mol respectively. Similarly the highest obtained docking energy between NNAL and enzymes RAD23A, CCNH, CDK7, and CETN2 were -7.46 kcal/mol, -7.94 kcal/mol, -7.83 kcal/mol and -7.67 kcal/mol respectively. In order to find out the effect of NNK and NNAL on enzymes involved in the NER pathway applying protein-protein interaction and protein-complex (i.e. enzymes docked with NNK/NNAL) interaction analysis. It was found that carcinogens are well capable to reduce the normal functioning of genes like RAD23A (HR23A), CCNH, CDK7 and CETN2. In silico analysis indicated loss of functions of these genes and their corresponding enzymes, which possibly might be a cause for alteration of DNA repair pathways leading to damage buildup and finally contributing to cancer formation.

Interaction with CCNH/CDK7 facilitates CtBP2 promoting esophageal squamous cell carcinoma (ESCC) metastasis via upregulating epithelial-mesenchymal transition (EMT) progression.

CtBP2, as a transcriptional corepressor of epithelial-specific genes, has been reported to promote tumor due to upregulating epithelial-mesenchymal transition (EMT) in cancer cells. CtBP2 was also demonstrated to contribute to the proliferation of esophageal squamous cell carcinoma (ESCC) cells through a negative transcriptional regulation of p16(INK4A). In this study, for the first time, we reported that CtBP2 expression, along with CCNH/CDK7, was higher in ESCC tissues with lymph node metastases than in those without lymph node metastases. Moreover, both CtBP2 and CCNH/CDK7 were positively correlated with E-cadherin, tumor grade, and tumor metastasis. However, the concrete mechanism of CtBP2's role in enhancing ESCC migration remains incompletely understood. We confirmed that CCNH/CDK7 could directly interact with CtBP2 in ESCC cells in vivo and in vitro. Furthermore, our data demonstrate for the first time that CtBP2 enhanced the migration of ESCC cells in a CCNH/CDK7-dependent manner. Our results indicated that CCNH/CDK7-CtBP2 axis may augment ESCC cell migration, and targeting the interaction of both may provide a novel therapeutic target of ESCC.

Association of single nucleotide polymorphisms in cell cycle regulatory genes with oral cancer susceptibility.

Alterations in the regulation of the cell cycle are strongly linked to tumorigenesis, so genetic variants in genes critical to control of the cycle are good candidates to have their association with susceptibility to oral cancer assessed. In this hospital-based, case-control study of 445 patients who had been newly-diagnosed with oral cancer and 449 unaffected controls, we used a multigenic approach to examine the associations among a panel of 10 selected polymorphisms in the pathway of the cell cycle that were possibly susceptible to oral cancer. Six of 9 single nucleotide polymorphisms in the cell cycle showed significant risks for oral cancer, the highest risk being evident for p27 (rs34329; Odds ratio 3.05, 95% CI 2.12 to 4.40). A significant risk of oral cancer was also evident for individual polymorphisms of cyclin E (rs1406), cyclin H (rs3093816), cyclin D1-1 (rs647451), cyclin D2 (rs3217901) and Rb1-2 (rs3092904). The risk of oral cancer increased significantly as the number of unfavourable genotypes in the pathway increased, and so the results point to a stronger combined effect of polymorphisms in important cell cycle regulatory genes on predisposition to oral cancer.

Pharmacogenetic predictors of severe peripheral neuropathy in colon cancer patients treated with oxaliplatin-based adjuvant chemotherapy: a GEMCAD group study.

BACKGROUND: Oxaliplatin-based chemotherapy (CT), widely used as adjuvant therapy for stage III and selected high-risk stage II colon cancer (CC) patients, is often associated with cumulative peripheral neuropathy. Our aim is to identify single-nucleotide polymorphisms (SNPs) in genes involved in oxaliplatin metabolism, DNA repair mechanisms, cell cycle control, detoxification or excretion pathways to predict severe (grade 2-3) oxaliplatin-induced peripheral neuropathy (OXPN) among CC patients treated with oxaliplatin and fluoropyrimidine-based adjuvant CT. PATIENTS AND METHODS: Genomic DNA was extracted from formalin-fixed-paraffin-embedded peritumoral samples from 206 high-risk stage II and stage III CC patients receiving oxaliplatin-based adjuvant CT from January 2004 to December 2009. Genotyping was carried out for 34 SNPs in 15 genes using MassARRAY (SEQUENOM) technology. A total of 181 stage II-III CC patients treated with the same CT regimens were enrolled as a validation set. RESULTS: The rs2230641 cyclin H (CCNH) rs2230641 C/C [odd ratio (OR)=5.03, 95% confidence interval (CI) 1.061-2.41, P=0.042] and the ATP-binding cassette subfamily G, member 2 (ABCG2) rs3114018 A/A genotypes (OR=2.67; 95% CI 0.95-4.41; P=0.059) were associated with a higher risk of severe OXPN. In addition, patients harboring the combination of CCNH C/C and/or the ABCG2 rs3114018 A/A genotypes had a higher risk of grade 2-3 OXPN than those with the CCNH any T and ABCG2 any C genotypes (37.73% versus 19.42%; OR=2.46; 95% CI 1.19-5.07; P=0.014) in the logistic regression analysis using age, gender, adjuvant CT regimen and cumulative dose of oxaliplatin as covariates. The ability to predict severe OXPN of this combined analysis was independently validated in the second cohort (58% versus 33.33%; OR=2.99; 95% CI 1.45-6.13; P=0.002). CONCLUSIONS: Our results suggest that SNPs in CCNH and ABCG2 can modulate the development of severe OXPN among stage II-III CC patients who received oxaliplatin-based CT, thus enabling the individualization of adjuvant treatment.

In silico characterization and molecular dynamics simulation of Pfcyc-1, a cyclin homolog of Plasmodium falciparum.

Malaria is still one of the deadly diseases resulting in deaths of millions of people worldwide and situation has become worse due to alarming rise in anti-malarial drug resistance. Genome sequence availability of Plasmodium falciparum, the main causal organism of severe malaria in humans, has enabled identification of various parasite cell cycle regulators like several cyclins and cyclin dependent kinases or CDKs which are promising novel drug targets for Malaria. Here, we present in silico characterization of tertiary structure of Pfcyc-1, a P. falciparum cyclin homolog, which enables identification of key structural elements that contribute to its tertiary structure and function. We have investigated the structure and dynamics of Pfcyc-1 structural model by performing 10 ns molecular dynamics (MD) simulation. Our study indicates that despite poor sequence similarities with cyclin H and A, the characteristic structural cyclin domains are conserved in Pfcyc-1 too. The Pfcyc-1 model reveals a cyclin box, consisting of two tandemly repeating five-helix bundles separated by a linker hinge peptide. Furthermore, the amino acid residues in other known cyclins mediating cyclin-CDK interactions are conserved in Pfcyc-1. The model and its MD simulation offer a first ever structural annotation of any plasmodium cyclin, which along with sequence comparisons, helps in identification of important functional residues mediating the Pfcyc-1-CDK like interactions.

The role of CCNH Val270Ala (rs2230641) and other nucleotide excision repair polymorphisms in individual susceptibility to well-differentiated thyroid cancer.

Well-differentiated thyroid cancer (DTC) is the most common form of thyroid cancer (TC); however, with the exception of radiation exposure, its etiology remains largely unknown. Several single nucleotide polymorphisms (SNPs) have previously been implicated in DTC risk. Nucleotide excision repair (NER) polymorphisms, despite having been associated with cancer risk at other locations, have received little attention in the context of thyroid carcinogenesis. In order to evaluate the role of NER pathway SNPs in DTC susceptibility, we performed a case-control study in 106 Caucasian Portuguese DTC patients and 212 matched controls. rs2230641 (CCNH), rs2972388 (CDK7), rs1805329 (RAD23B), rs3212986 (ERCC1), rs1800067 (ERCC4), rs17655, rs2227869 (ERCC5), rs4253211 and rs2228529 (ERCC6) were genotyped using TaqMan® methodology, while conventional PCR-RFLP was employed for rs2228000 and rs2228001 (XPC). When considering all DTC cases, only rs2230641 (CCNH) was associated with DTC risk; a consistent increase in overall DTC risk was observed for both the heterozygous genotype (OR=1.89, 95% CI=1.14-3.14) and the variant allele carriers (OR=1.79, 95% CI=1.09-2.93). Histological stratification analysis confirmed an identical effect on follicular TC (OR=2.72, 95% CI=1.19-6.22, for heterozygous; OR=2.44, 95% CI=1.07­5.55, for variant allele carriers). Considering papillary TC, the rs2228001 (XPC) variant genotype was associated with increased risk (OR=2.33, 95% CI=1.05-5.16), while a protective effect was observed for rs2227869 (ERCC5) (OR=0.26, 95% CI=0.08­0.90, for heterozygous; OR=0.25, 95% CI=0.07-0.86, for variant allele carriers). No further significant results were observed. Our results suggest that NER polymorphisms such as rs2230641 (CCNH) and, possibly, rs2227869 (ERCC5) and rs2228001 (XPC), may influence DTC susceptibility. However, larger studies are required to confirm these results.

Single nucleotide polymorphisms in the NER pathway and clinical outcome of patients with bone malignant tumors.

The effects of polymorphisms in ERCC5, ERCC6, XPC, CCNH and MMS19L on osteosarcoma response to chemotherapy and the survival of the affected patients were assessed. Genotyping of ERCC5, ERCC6, XPC, CCNH and MMS19L was performed by PCR-RFLP assay. The median PFS was 12.8 months, and the median OS was 18.6 months. Individuals carrying homozygous genotypes of ERCC5 rs17655 and ERCC5 rs1047768 were more like to have good response to treatment, while those carrying homozygous genotypes of MMS19L rs29001322 showed poor response. Osteosarcoma patients carrying TT genotype of ERCC5 rs1047768 showed a significantly longer PFS (16.8 months) and OS (21.4 months) than CC genotype, with HRs(95% CI) of 0.31 (0.10-0.93) and 0.32 (0.06-0.97), respectively. Conversely, those with the TT genotype of MMS19L rs29001322 demonstrated shorter PFS and OS, the HRs (95% CI) being 2.23 (1.08-4.15) and 4.62 (1.45-16.08), respectively. Our findings showed polymorphisms in ERCC5 rs1047768 and MMS19L rs29001322 to be associated with clinical outcome of osteosarcoma patients undergoing chemotherapy.

A Cdk7-Cdk4 T-loop phosphorylation cascade promotes G1 progression.

Eukaryotic cell division is controlled by cyclin-dependent kinases (CDKs), which require phosphorylation by a CDK-activating kinase (CAK) for full activity. Chemical genetics uncovered requirements for the metazoan CAK Cdk7 in determining cyclin specificity and activation order of Cdk2 and Cdk1 during S and G2 phases. It was unknown if Cdk7 also activates Cdk4 and Cdk6 to promote passage of the restriction (R) point, when continued cell-cycle progression becomes mitogen independent, or if CDK-activating phosphorylation regulates G1 progression. Here we show that Cdk7 is a Cdk4- and Cdk6-activating kinase in human cells, required to maintain activity, not just to establish the active state, as is the case for Cdk1 and Cdk2. Activating phosphorylation of Cdk7 rises concurrently with that of Cdk4 as cells exit quiescence and accelerates Cdk4 activation in vitro. Therefore, mitogen signaling drives a CDK-activation cascade during G1 progression, and CAK might be rate-limiting for R point passage.

Low expression of cyclinH and cyclin-dependent kinase 7 can decrease the proliferation of human esophageal squamous cell carcinoma.

BACKGROUND: Increased expression of cyclinH (CCNH) and cyclin-dependent kinase 7 (CDK7) has a relationship with poor prognosis in most human cancers. AIM: Investigate the expression of CCNH and CDK7 in human esophageal squamous cell carcinoma (ESCC) and the effect of chemotherapy on their expression. METHODS: Western blotting and immunohistochemistry were used to measure the expression of CCNH and CDK7 proteins in ESCC and adjacent normal tissue in 98 patients. We use Cell Counting Kit-8 and cell flow to analyze the effects of cisplatin and interference of CCNH and CDK7 in cell cycle process. RESULTS: Immunohistochemical analysis showed that CCNH and CDK7 expression were significantly associated with unfavorable clinicopathologic variables. CCNH and CDK7 protein levels were elevated in ESCC tissues in comparison with adjacent normal tissues. Survival analysis revealed that CCNH and CDK7 overexpression were significantly associated with overall survival (P < 0.001). Cisplatin or interference of CCNH or CDK7 led cells to grow slowly. Overexpression of CCNH and CDK7 in TE1 cells can lead to resistance to cisplatin. CONCLUSIONS: We can conclude that CCNH and CDK7 may play an important role in the tumorigenesis and development of ESCC. CCNH and CDK7 expression affected the chemotherapy of tumor.

Amniotic membrane-derived cells inhibit proliferation of cancer cell lines by inducing cell cycle arrest.

Cells derived from the amniotic foetal membrane of human term placenta have drawn particular attention mainly for their plasticity and immunological properties, which render them interesting for stem-cell research and cell-based therapeutic applications. In particular, we have previously demonstrated that amniotic mesenchymal tissue cells (AMTC) inhibit lymphocyte proliferation in vitro and suppress the generation and maturation of monocyte-derived dendritic cells. Here, we show that AMTC also significantly reduce the proliferation of cancer cell lines of haematopoietic and non-haematopoietic origin, in both cell-cell contact and transwell co-cultures, therefore suggesting the involvement of yet-unknown inhibitory soluble factor(s) in this 'cell growth restraint'. Importantly, we provide evidence that the anti-proliferative effect of AMTC is associated with induction of cell cycle arrest in G0/G1 phase. Gene expression analyses demonstrate that AMTC can down-regulate cancer cells' mRNA expression of genes associated with cell cycle progression, such as cyclins (cyclin D2, cyclin E1, cyclin H) and cyclin-dependent kinase (CDK4, CDK6 and CDK2), whilst they up-regulate cell cycle negative regulator such as p15 and p21, consistent with a block in G0/G1 phase with no progression to S phase. Taken together, these findings warrant further studies to investigate the applicability of these cells for controlling cancer cell proliferation in vivo.

Cyclin H expression is increased in GIST with very-high risk of malignancy.

BACKGROUND: Risk estimation of gastrointestinal stromal tumours (GIST) is based on tumour size and mitotic rate according to the National Institutes of Health consensus classification. The indication for adjuvant treatment of patients with high risk GIST after R0 resection with small molecule inhibitors is still a controversial issue, since these patients represent a highly heterogeneous population. Therefore, additional prognostic indicators are needed. Here, we evaluated the prognostic value of cyclin H expression in GIST. METHODS: In order to identify prognostic factors of GIST we evaluated a single centre cohort of ninety-five GIST patients. First, GISTs were classified with regard to tumour size, mitotic rate and localisation according to the NIH consensus and to three additional suggested risk classifications. Second, Cyclin H expression was analysed. RESULTS: Of ninety-five patients with GIST (53 female/42 male; median age: 66.78a; range 17-94a) risk classification revealed: 42% high risk, 20% intermediate risk, 23% low risk and 15% very low risk GIST. In patients with high risk GIST, the expression of cyclin H was highly predictive for reduced disease-specific survival (p = 0.038). A combination of cyclin H expression level and high risk classification yielded the strongest prognostic indicator for disease-specific and disease-free survival (p < or = 0.001). Moreover, in patients with tumour recurrence and/or metastases, cyclin H positivity was significantly associated with reduced disease-specific survival (p = 0.016) regardless of risk-classification. CONCLUSION: Our data suggest that, in addition to high risk classification, cyclin H expression might be an indicator for "very-high risk" GIST.

Acute myeloid leukemia outcome: role of nucleotide excision repair polymorphisms in intermediate risk patients.

In acute myeloid leukemia (AML), cytogenetics predicts treatment outcome for the favorable and poor subgroups but not for the intermediate subgroup. Polymorphisms within the nucleotide excision repair (NER) pathway may lead to interindividual differences in DNA repair capacity, influencing outcome. We studied the role of six polymorphisms (ERCC1 Gln504Lys, XPD Lys751Gln, XPC Ala499Val, XPC Lys939Gln, XPG Asp1104His, and CCNH Val270Ala) in overall and disease-free survival among 170 adult de novo patients with intermediate cytogenetics (diploid [n = 117]; non-diploid [n = 53]), treated with induction chemotherapy. Kaplan-Meier and Cox proportional hazards models were performed. Diploid patients with the XPD AC/CC genotype survived shorter than those with the wild-type genotype (median survival 22 vs. 40 months, p = 0.03). Diploid patients with XPC CT/TT genotype survived shorter than those with the wild-type genotype (median survival 15 vs. 30 months, p = 0.02). After adjusting for clinical and sociodemographic variables, patients carrying both XPD AC/CC and XPC CT/TT had a greater than two-fold increased risk of dying, compared to those with the wild-type genotypes (HR = 2.49; 95% CI: 1.06-5.85). No associations were observed for disease-free survival. This combined genotype may modulate treatment effect, decreasing overall survival. These findings could in the future help select treatments for patients with normal cytogenetics.