The present study was performed with the aim of understanding the mechanisms of pathogenesis and providing novel biomarkers for cervical cancer by constructing a regulatory circular (circ)RNA‑micro (mi)RNA‑mRNA network. Using an adjusted P-value of <0.05 and an absolute log value of fold-change >1, 16 and 156 miRNAs from GSE30656 and The Cancer Genome Atlas (TCGA), 5,321 mRNAs from GSE63514, 4,076 mRNAs from cervical squamous cell carcinoma and endocervical adenocarcinoma (from TCGA) and 75 circRNAs from GSE102686 were obtained. Using RNAhybrid, Venn and UpSetR plot, 12 circRNA‑miRNA pairs and 266 miRNA‑mRNA pairs were obtained. Once these pairs were combined, a circRNA‑miRNA‑mRNA network with 11 circRNA nodes, 4 miRNA nodes, 153 mRNA nodes and 203 edges was constructed. By constructing the protein‑protein interaction network using Molecular Complex Detection scores >5 and >5 nodes, 7 hubgenes (RRM2, CEP55, CHEK1, KIF23, RACGAP1, ATAD2 and KIF11) were identified. By mapping the 7 hubgenes into the preliminary circRNA‑miRNA‑mRNA network, a circRNA‑miRNA‑hubgenes network consisting of 5 circRNAs (hsa_circRNA_000596, hsa_circRNA_104315, hsa_circRNA_400068, hsa_circRNA_101958 and hsa_circRNA_103519), 2 mRNAs (hsa‑miR‑15b and hsa‑miR‑106b) and 7 mRNAs (RRM2, CEP55, CHEK1, KIF23, RACGAP1, ATAD2 and KIF11) was constructed. There were 22 circRNA‑miRNA‑mRNA regulatory axes identified in the subnetwork. By analyzing the overall survival for the 7 hubgenes using the Gene Expression Profiling Interactive Analysis tool, higher expression of RRM2 was demonstrated to be associated with a significantly poorer overall survival. PharmGkb analysis identified single nucleotide polymorphisms (SNPs) of rs5030743 and rs1130609 of RRM2, which can be treated with cladribine and cytarabine. RRM2 was also indicated to be involved in the gemcitabine pathway. The 5 circRNAs (hsa_circRNA_000596, hsa_circRNA_104315, hsa_circRNA_400068, hsa_circRNA_101958 and hsa_circRNA_103519) may function as competing endogenous RNAs and serve critical roles in cervical cancer. In addition, cytarabine may produce similar effects to gemcitabine and may be an optional chemotherapeutic drug for treating cervical cancer by targeting rs5030743 and rs1130609 or other similar SNPs. However, the specific mechanism of action should be confirmed by further study.

Opa interacting protein 5 (OIP5) overexpression is associated with human carcinoma. However, its biological function, underlying mechanism and clinical significance in liver cancer remain unknown. In the present study, the effects of OIP5 expression on liver cancer, and the mechanisms regulating these effects, were investigated. OIP5 expression was measured in human hepatocellular carcinoma (HCC) tissues and liver cancer cell lines. The effect of OIP5 knockdown on tumorigenesis was also detected in nude mice, and differentially‑expressed genes (DEGs) were identified and their biological functions were identified. The results indicated that OIP5 expression was significantly upregulated in HCC tissues and four liver cancer cell lines (P<0.01). Increased OIP5 protein expression significantly predicted reduced survival rate of patients with HCC (P<0.01). OIP5 knockdown resulted in the suppression of proliferation and colony forming abilities, cell cycle arrest at the G0/G1 or G2/M phases, and promotion of cell apoptosis. A total of 628 DEGs, including 87 upregulated and 541 downregulated genes, were identified following OIP5 knockdown. Functional enrichment analysis indicated that DEGs were involved in 'RNA Post‑Transcriptional Modification, Cancer and Organismal Injury and Abnormalities'. Finally, OIP5 knockdown in Huh7 cells dysregulated bone morphogenetic protein receptor type 2/JUN/checkpoint kinase 1/Rac family small GTPase 1 expression. In conclusion, the overall results demonstrated the involvement of OIP5 in the progression of liver cancer and its mechanism of action.

Accumulating evidence has demonstrated that long non‑coding RNAs (lncRNAs) play important roles in the pathogenesis and development of diverse types of human disorders. Cancer susceptibility candidate 9 (CASC9), a gene encoding a lncRNA, has frequently been reported to be dysregulated and has been implicated in multiple types of human malignancies. However, the biological role of lncRNA CASC9 in breast cancer (BC) remains largely unknown. The present study aimed to investigate the role of lncRNA CASC9 in BC and to elucidate the potential molecular mechanisms involved. In the present study, lncRNA CASC9 was found to be significantly upregulated in both BC tissues and cell lines. Furthermore, functional analyses revealed that lncRNA CASC9 accelerated BC cell proliferation, promoted cell cycle progression and suppressed cell apoptosis. Moreover, mechanical experiments demonstrated that lncRNA CASC9 positively regulated checkpoint kinase 1 (CHK1) by competitively binding to the miR‑195/497 cluster in BC cells. Additionally, the knockdown of lncRNA CASC9 was observed to suppress breast tumor growth in vivo. Taken together, the results of this study indicate that lncRNA CASC9 plays an oncogenic role in BC through sponging the miR‑195/497 cluster, and that lncRNA CASC9 may be used as a novel therapeutic target and as a potential diagnostic marker for BC.

Radiotherapy is a frequent mode of cancer treatment, although the development of radioresistance limits its effectiveness. Extensive investigations indicate the diversity of the mechanisms underlying radioresistance. Here, we aimed to explore the effects of extracellular signal-regulated kinase 5 (ERK5) on lung cancer radioresistance and the associated mechanisms. Our data showed that ERK5 is activated during solid lung cancer development, and ectopic expression of ERK5 promoted cell proliferation and G2/M cell cycle transition. In addition, we found that ERK5 is a potential regulator of radiosensitivity in lung cancer cells. Mechanistic investigations revealed that ERK5 could trigger IR-induced activation of Chk1, which has been implicated in DNA repair and cell cycle arrest in response to DNA double-strand breaks (DSBs). Subsequently, ERK5 knockdown or pharmacological inhibition selectively inhibited colony formation of lung cancer cells and enhanced IR-induced G2/M arrest and apoptosis. In vivo, ERK5 knockdown strongly radiosensitized A549 and LLC tumor xenografts to inhibition, with a higher apoptotic response and reduced tumor neovascularization. Taken together, our data indicate that ERK5 is a novel potential target for the treatment of lung cancer, and its expression might be used as a biomarker to predict radiosensitivity in NSCLC patients.

BACKGROUND: While androgen deprivation therapy (ADT) and radiotherapy (RT) are currently used together to treat locally advanced prostate cancer (PCa), RT might have the adverse effect of increasing the PCa androgen receptor (AR) protein expression, which might then increase the resistance to continued RT.
METHODS: We used multiple assays for RT sensitivity, protein and RNA expression of AR and related DDR genes, ROS level, DNA damage/repair level, cell cycle and apoptosis. All statistical comparisons were analyzed with t-test or one-way ANOVA.
FINDINGS: We demonstrated that RT induced AR expression in C4-2 and CWR22Rv-1 cells. We found that combining RT and ASC-J9
INTERPRETATION: Targeting ionizing radiation (IR)-increased AR with the AR degradation enhancer, ASC-J9

High-risk human papillomaviruses (HPVs) constitutively activate ataxia telangiectasia mutated (ATM) and ataxia telangiectasia- and Rad3-related (ATR) DNA damage repair pathways for viral genome amplification. HPVs activate these pathways through the immune regulator STAT-5. For the ATR pathway, STAT-5 increases expression of the topoisomerase IIβ-binding protein 1 (TopBP1), a scaffold protein that binds ATR and recruits it to sites of DNA damage. TopBP1 also acts as a transcriptional regulator, and we investigated how this activity influenced the HPV life cycle. We determined that TopBP1 levels are increased in cervical intraepithelial neoplasias as well as cervical carcinomas, consistent with studies in HPV-positive cell lines. Suppression of TopBP1 by shRNAs impairs HPV genome amplification and activation of the ATR pathway but does not affect the total levels of ATR and CHK1. In contrast, knockdown reduces the expression of other DNA damage factors such as RAD51 and Mre11 but not BRCA2 or NBS1. Interestingly, TopBP1 positively regulates the expression of E2F1, a TopBP1-binding partner, and p73 in HPV-positive cells in contrast to its effects in other cell types. TopBP1 transcriptional activity is regulated by AKT, and treatment with AKT inhibitors suppresses expression of E2F1 and p73 without interfering with ATR signaling. Importantly, the levels of p73 are elevated in HPV-positive cells and its knockdown impairs HPV genome amplification. This demonstrates that p73, like p63 and p53, is an important regulator of the HPV life cycle that is controlled by the transcriptional activating properties of the multifunctional TopBP1 protein.

PURPOSE: Triple-negative breast cancers (TNBC) are often resistant to treatment with ionizing radiation (IR). We sought to investigate whether pharmacologic inhibition of Chk1 kinase, which is commonly overexpressed in TNBC, preferentially sensitizes TNBC cells to IR.
METHODS: Ten breast cancer cell lines were screened with small molecule inhibitors against Chk1 and other kinases. Chk1 inhibition was also tested in isogenic KRAS mutant or wild-type cancer cells. Cellular radiosensitization was measured by short-term and clonogenic survival assays and by staining for the DNA double-strand break (DSB) marker γ-H2AX. Radiosensitization was also assessed in breast cancer biopsies using an ex vivo assay. Aurora B kinase-dependent mitosis-like chromatin condensation, a marker of radioresistance, was detected using a specific antibody against co-localized phosphorylation of serine 10 and trimethylation of lysine 9 on histone 3 (H3K9me3/S10p). Expression of CHEK1 and associated genes was evaluated in TNBC and lung adenocarcinoma.
RESULTS: Inhibition of Chk1 kinase preferentially radiosensitized TNBC cells in vitro and in patient biopsies. Interestingly, TNBC cells displayed lower numbers of IR-induced DSBs than non-TNBC cells, correlating with their observed radioresistance. We found that Chk1 suppressed IR-induced DSBs in these cells, which was dependent on H3K9me3/S10p-a chromatin mark previously found to indicate radioresistance in KRAS mutant cancers. Accordingly, the effects of Chk1 inhibition in TNBC were reproduced in KRAS mutant but not wild-type cells. We also observed co-expression of genes in this Chk1 chromatin pathway in TNBC and KRAS mutant lung cancers.
CONCLUSIONS: Chk1 promotes an unexpected, common phenotype of chromatin-dependent DSB suppression in radioresistant TNBC and KRAS mutant cancer cells, providing a direction for future investigations into overcoming the treatment resistance of TNBC.

The BRCA1-BRCA2-RAD51 axis is essential for homologous recombination repair (HRR) and is frequently disrupted in breast cancers. PARP inhibitors (PARPis) are used clinically to treat BRCA-mutated breast tumors. Using a genetic screen, we identified EMI1 as a modulator of PARPi sensitivity in triple-negative breast cancer (TNBC) cells. This function requires the F-box domain of EMI1, through which EMI1 assembles a canonical SCF ubiquitin ligase complex that constitutively targets RAD51 for degradation. In response to genotoxic stress, CHK1-mediated phosphorylation of RAD51 counteracts EMI1-dependent degradation by enhancing RAD51's affinity for BRCA2, leading to RAD51 accumulation. Inhibition of RAD51 degradation restores HRR in BRCA1-depleted cells. Human breast cancer samples display an inverse correlation between EMI1 and RAD51 protein levels. A subset of BRCA1-deficient TNBC cells develop resistance to PARPi by downregulating EMI1 and restoring RAD51-dependent HRR. Notably, reconstitution of EMI1 expression reestablishes PARPi sensitivity both in cellular systems and in an orthotopic mouse model.

Cholinergic Receptor Nicotinic Alpha 5 (CHRNA5) is an important susceptibility locus for nicotine addiction and lung cancer. Depletion of CHRNA5 has been associated with reduced cell viability, increased apoptosis and alterations in cellular motility in different cancers yet not in breast cancer. Herein we first showed the expression of CHRNA5 was variable and positively correlated with the fraction of total genomic alterations in breast cancer cell lines and tumors indicating its potential role in DNA damage response (DDR). Next, we demonstrated that silencing of CHRNA5 expression in MCF7 breast cancer cell line by RNAi affected expression of genes involved in cytoskeleton, TP53 signaling, DNA synthesis and repair, cell cycle, and apoptosis. The transcription profile of CHRNA5 depleted MCF7 cells showed a significant positive correlation with that of A549 lung cancer cell line while exhibiting a negative association with the CHRNA5 co-expression profile obtained from Cancer Cell Line Encylopedia (CCLE). Moreover, it exhibited high similarities with published MCF7 expression profiles obtained from exposure to TP53 inducer nutlin-3a and topoisomerase inhibitors. We then demonstrated that CHRNA5 siRNA treatment reduced cell viability and DNA synthesis indicating G1 arrest while it significantly increased apoptotic sub-G1 cell population. Accordingly, we observed lower levels of phosphorylated RB (Ser807/811) and an increased BAX/BCL2 ratio in RNAi treated MCF7 cells. We also showed that CHRNA5 RNAi transcriptome correlated negatively with DDR relevant gene expression profile in breast cancer gene expression datasets while the coexposure to topoisomerase inhibitors in the presence of CHRNA5 RNAi enhanced chemosensitivity potentially due to reduced DDR. CHRNA5 RNAi consistently lowered total CHEK1 mRNA and protein levels as well as phosphorylated CHEK1 (Ser345) in MCF7 cells. We also detected a significant positive correlation between the expression levels of CHRNA5 and CHEK1 in CCLE, TCGA and METABRIC breast cancer datasets. Our study suggests CHRNA5 RNAi is associated with cell cycle inhibition, apoptosis as well as reduced DDR and increased drug sensitivity in breast cancer yet future studies are warranted since dose- and cell line-specific differences exist in response to CHRNA5 depletion. Gene expression microarray data can be accessed from GEO database under the accession number GSE89333.

Paclitaxel, which isolated from Taxus brevifolia, is recently started to be used against prostate cancer treatment and it is a very effective compound against cancer. In this study, we aimed to test the synergistic effect of two plant active compounds (sulphoraphane (SFN) and silymarin (SILY)) and several endemic plant species from Turkey (such as Phlomis leucophracta, Rubia davisiana, Alkanna tinctoria), which are known to have anticarcinogenic effect on androgen-independent PC3 and DU145, and androgen-dependent VCaP prostate cancer cell lines, with paclitaxel on the expression of cell cycle signaling and apoptosis regulator genes. Herbal substances and endemic herbal extracts were combined with Paclitaxel drug. IC

BACKGROUND/AIM: 5-Fluorouracil (5-FU) is frequently used in colorectal cancer treatment, but with limited success. The aim of the present study was to explore the cytotoxic effects of 5-FU, in combination with inhibition of doublecortin-like kinase 1 (Dclk1), a tumor stem cell marker that regulates pro-survival signaling in colorectal cancer cells, in the human colon cancer cell line, COLO-320.
MATERIALS AND METHODS: The effects of 5-FU treatment plus Dclk1 inhibition on the phosphorylation of checkpoint kinase 1 (Chk1), cell cycle, DNA damage, apoptosis, and cell survival in COLO-320 cells were evaluated.
RESULTS: Combined treatment with 5-FU and a Dclk1 inhibitor, LRRK2-IN-1 (LRRK), decreased 5-FU-induced phosphorylation of Chk1 and canceled 5-FU-induced cell-cycle arrest at the S phase. Combined treatment with 5-FU and LRRK failed to induce poly (ADP-ribose) polymerase 1 (PARP-1) cleavage, but tended to decrease cell survival compared to individual treatment with 5-FU or LRRK.
CONCLUSION: These results indicate that a combination of 5-FU and LRRK may be an effective, novel approach for colorectal cancer therapy.

Objective: To evaluate the association between upregulated differentially expressed genes (DEGs) and the outcomes of patients with hepatocellular carcinoma (HCC).
Methods: Using Gene Expression Omnibus (GEO) datasets including GSE45436, GSE55092, GSE60502, GSE84402, and GSE17548, we detected upregulated DEGs in tumors. KEGG, GO, and Reactome enrichment analysis of the DEGs was conducted to clarify their function. The impact of the upregulated DEGs on patients' survival was analyzed based on TCGA profile.
Results: 161 shared upregulated DEGs were identified among GSE45436, GSE55092, GSE60502, and GSE84402 profiles. Cell cycle was the shared pathway/biological process in the gene sets investigation among databases of KEGG, GO, and Reactome. After being validated in GSE17548, 13 genes including BUB1B, CCNA2, CCNB1, CCNE2, CDC20, CDC6, CDC7, CDK1, CDK4, CDKN2A, CHEK1, MAD2L1, and MCM3 in cell cycle pathway were shared in the three databases for enrichment. The expression of BUB1B, CCNB1, CDC7, CDC20, and MCM3 was upregulated in HCC tissues when compared with adjacent normal tissues in 6.67%, 7.5%, 8.06%, 5.56%, and 9.72% of HCC patients, respectively. Overexpression of BUB1B, CCNB1, CDC7, CDC20, and MCM3 in HCC tissues accounted for poorer overall survival (OS) and disease-free survival (DFS) in HCC patients (all log rank
Conclusion: Correlated with advanced histologic grade and/or vascular invasion, upregulation of BUB1B, CCNB1, CDC7, CDC20, and MCM3 in HCC tissues predicted worse OS and DFS in HCC patients. These genes could be novel therapeutic targets for HCC treatment.

Genomic instability is a key hallmark of cancer that arises owing to defects in the DNA damage response (DDR) and/or increased replication stress. These alterations promote the clonal evolution of cancer cells via the accumulation of driver aberrations, including gene copy-number changes, rearrangements and mutations; however, these same defects also create vulnerabilities that are relatively specific to cancer cells, which could potentially be exploited to increase the therapeutic index of anticancer treatments and thereby improve patient outcomes. The discovery that BRCA-mutant cancer cells are exquisitely sensitive to inhibition of poly(ADP-ribose) polymerase has ushered in a new era of research on biomarker-driven synthetic lethal treatment strategies for different cancers. The therapeutic landscape of antitumour agents targeting the DDR has rapidly expanded to include inhibitors of other key mediators of DNA repair and replication, such as ATM, ATR, CHK1 and CHK2, DNA-PK and WEE1. Efforts to optimize these therapies are ongoing across a range of cancers, involving the development of predictive biomarker assays of responsiveness (beyond BRCA mutations), assessment of the mechanisms underlying intrinsic and acquired resistance, and evaluation of rational, tolerable combinations with standard-of-care treatments (such as chemotherapeutics and radiation), novel molecularly targeted agents and immune-checkpoint inhibitors. In this Review, we discuss the current status of anticancer therapies targeting the DDR.

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Hepatocellular carcinoma (HCC) accounts for a significant proportion of liver cancer, which has become the second most common cause of cancer-related mortality worldwide. To investigate the potential mechanisms of invasion and progression of HCC, bioinformatics analysis and validation by qRT-PCR were performed. We found 237 differentially expressed genes (DEGs) including EGR1, FOS, and FOSB, which were three cancer-related transcription factors. Subsequently, we constructed TF-gene network and miRNA-TF-mRNA network based on data obtained from mRNA and miRNA expression profiles for analysis of HCC. We found that 42 key genes from the TF-gene network including EGR1, FOS, and FOSB were most enriched in the p53 signaling pathway. The qRT-PCR data confirmed that mRNA levels of EGR1, FOS, and FOSB all were decreased in HCC tissues. In addition, we confirmed that the mRNA levels of CCNB1, CCNB2, and CHEK1, three key markers of the p53 signaling pathway, were all increased in HCC tissues by bioinformatics analysis and qRT-PCR validation. Therefore, we speculated that miR-181a-5p, which was upregulated in HCC tissues, could regulate FOS and EGR1 to promote the invasion and progression of HCC by p53 signaling pathway. Overall, the study provides support for the possible mechanisms of progression in HCC.

BACKGROUND: DNA repair gene mutations are present in 8-10% of localized prostate cancers. It is unknown whether this is influenced by clinicopathologic factors.
METHODS: We interrogated localized prostate adenocarcinomas with tumor DNA sequencing information from the TCGA validated (n = 333) and Nature Genetics (n = 377) datasets. Homologous recombination repair genes included in our analysis were: ATM, BRCA1/2, CDK12, CHEK1/2, FANCA, FANCD2, FANCL, GEN1, NBN, PALB2, RAD51, and RAD51C. Proportions of cases with pathogenic DNA repair mutations (and in ATM/BRCA1/2 specifically) were reported by Gleason grade group, clinical T, pathologic T, and pathologic N stage. Odds ratios and Fisher's exact tests were used to compare proportions between categories.
RESULTS: Patients with Gleason grade groups 3 and higher were 2.2 times more likely to harbor any DNA repair mutation (95% CI: 1.2-4.2; 10.3% versus 5.0%) and were 2.7 times more likely to have BRCA1/2 or ATM mutations (95% CI: 1.3-6.6; 7.0% versus 2.7%) compared to those in Gleason grade groups 1-2. Patients with pathologic T3 and T4 stage (pT3/pT4) were 2.6 times more likely to have any DNA repair mutation (95% CI: 1.3-6.6; 13.0% versus 5.5%) and were 3.2 times more likely to have BRCA1/2 or ATM mutations (95% CI: 1.2-11.3; 9.5% versus 3.1%) compared to those with pT2 disease. There was no difference by clinical tumor or nodal stage. Among men with Gleason grade group ≥ 3 and clinical stage ≥ cT3, 21.3% (1 in 5) had a DNA repair mutation in any gene and 11.7% (1 in 9) had a mutation in ATM/BRCA1/2.
CONCLUSIONS: The prevalence of pathogenic DNA repair gene alterations is enriched in men with advanced tumor stages and higher Gleason grade groups, with maximal enrichment observed in those with Gleason grade group ≥ 3 and clinical stage ≥ cT3 disease. This information can be used to guide eligibility criteria for genomically targeted clinical trials in the neoadjuvant/adjuvant settings.

Mutations in SPOP, the gene most frequently point-mutated in primary prostate cancer, are associated with a high degree of genomic instability and deficiency in homologous recombination repair of DNA but the underlying mechanisms behind this defect are currently unknown. Here we demonstrate that SPOP knockdown leads to spontaneous replication stress and impaired recovery from replication fork stalling. We show that this is associated with reduced expression of several key DNA repair and replication factors including BRCA2, ATR, CHK1 and RAD51. Consequently, SPOP knockdown impairs RAD51 foci formation and activation of CHK1 in response to replication stress and compromises recovery from replication fork stalling. An SPOP interactome analysis shows that wild type (WT) SPOP but not mutant SPOP associates with multiple proteins involved in transcription, mRNA splicing and export. Consistent with the association of SPOP with transcription, splicing and RNA export complexes, the decreased expression of BRCA2, ATR, CHK1 and RAD51 occurs at the level of transcription.

Colorectal cancer (CRC) is one of the leading causes of cancer-related death worldwide. 5-Fluorouracil (5-FU) is widely used in the treatment of cancers, but its antineoplastic activity is limited in drug-resistant cancer cells. To investigate the detailed mechanism of 5-FU resistance, we developed a model of 5-FU-resistant cells from HCT-8 cells, a well-established colorectal cancer cell line. We found that the drug-resistant cells demonstrated high expression of TCF4 and β-catenin, indicating an upregulated Wnt pathway. A microarray analysis revealed that the suppression of the checkpoint kinase 1 (CHK1) pathway explained the resistance to 5-FU, especially in p53 wild-type cancer cells such as HCT-8. Our data also demonstrated that the CHK1 pathway is suppressed by the Wnt pathway in 5-FU-resistant cells. In summary, we have discovered a novel mechanism for 5-FU resistance mediated by histone deacetylation, which also revealed the crosstalk between the Wnt pathway and CHK1 pathway.

Cyclin-dependent kinase 12 (CDK12) belongs to the cyclin-dependent kinase (CDK) family of serine/threonine protein kinases that regulate transcriptional and post-transcriptional processes, thereby modulating multiple cellular functions. Early studies characterised CDK12 as a transcriptional CDK that complexes with cyclin K to mediate gene transcription by phosphorylating RNA polymerase II. CDK12 has been demonstrated to specifically upregulate the expression of genes involved in response to DNA damage, stress and heat shock. More recent studies have implicated CDK12 in regulating mRNA splicing, 3' end processing, pre-replication complex assembly and genomic stability during embryonic development. Genomic alterations in CDK12 have been detected in oesophageal, stomach, breast, endometrial, uterine, ovarian, bladder, colorectal and pancreatic cancers, ranging from 5% to 15% of sequenced cases. An increasing number of studies point to CDK12 inhibition as an effective strategy to inhibit tumour growth, and synthetic lethal interactions have been described with MYC, EWS/FLI and PARP/CHK1 inhibition. Herein, we discuss the present literature on CDK12 in cell function and human cancer, highlighting important roles for CDK12 as a clinical biomarker for treatment response and potential as an effective therapeutic target.

Chemotherapy for suppressing tumor growth and metastasis tends to induce various effects on other organs. Using AZD7762, an inhibitor of checkpoint kinase (Chk) 1 and 2, the present study examined its effect on mammary tumor cells in addition to bone cells (osteoclasts, osteoblasts and osteocytes), using monolayer cell cultures and three-dimensional (3D) cell spheroids. The results revealed that AZD7762 blocked the proliferation of 4T1.2 mammary tumor cells and suppressed the development of RAW264.7 pre-osteoclast cells by downregulating nuclear factor of activated T cells cytoplasmic 1. AZD7762 also promoted the mineralization of MC3T3 osteoblast-like cells and 3D bio-printed bone constructs of MLO-A5 osteocyte spheroids. While a Chk1 inhibitor, PD407824, suppressed the proliferation of tumor cells and the differentiation of pre-osteoclasts, its effect on gene expression in osteoblasts was markedly different compared with AZD7762. Western blotting indicated that the stimulating effect of AZD7762 on osteoblast development was associated with the inhibition of Chk2 and the downregulation of cellular tumor antigen p53. The results of the present study indicated that in addition to acting as a tumor suppressor, AZD7762 may prevent bone loss by inhibiting osteoclastogenesis and stimulating osteoblast mineralization.

Claspin was discovered as a Chk1-interacting protein necessary for Chk1 phosphorylation and activation by the upstream kinase, ATR, in response to DNA synthesis inhibition in Xenopus oocyte extracts. Subsequent investigations have defined a molecular model in which Claspin acts as an adaptor or scaffold protein to facilitate activation of Chk1 by ATR within a multiprotein complex that forms on single-stranded DNA at stalled replication forks and sites of DNA damage. Interestingly, Claspin is an unstable protein whose degradation via the proteasome is tightly regulated via ubiquitination and controlled by multiple ubiquitin ligases and deubiquitinases. As a result, Claspin levels fluctuate during the cell cycle, contributing to the regulation of checkpoint proficiency and playing a key role in terminating checkpoint-mediated cell cycle arrest. In addition to its role in signalling genotoxic stress, Claspin is required to maintain normal rates of replication fork progression during unperturbed DNA replication and may contribute to the regulation of replication origin firing. Consistent with this, Claspin can bind directly to DNA, with particular affinity for branched or forked molecules, and it interacts with multiple protein components of the replisome. As expected for a protein with key roles in checkpoint signalling and genome duplication, aberrations of Claspin expression and structure have been observed in cancer. Claspin is furthermore targeted to facilitate viral replication and plays a role in suppressing cellular DNA synthesis in response to nongenotoxic endoplasmic reticulum stress. Here, we review the functions and regulation of Claspin with a focus on areas of active research.

Cyclin-dependent kinases (CDK) are considered to be potential targets of anticancer drugs that can interrupt the uncontrolled division of cancer cells. In this study, we selected two selective CDK inhibitors, AT7519 and SNS‑032, from current clinical trials and examined their anticancer and radiosensitizing effects in a cervical cancer model. SNS‑032 was found to be more potent than AT7519, with a lower half maximal inhibitory concentration (IC50) value. Both AT7519 and SNS‑032 induced the apoptosis, premature senescence and cytostasis of cervical cancer cells, which led to the attenuation of tumor growth in vivo. Moreover, using these CDK inhibitors together with radiation synergistically inhibited tumor growth in a human xenograft tumor model. The concomitant activation of the p53 tumor suppressor and the suppression of cell cycle checkpoint responses mediated by Chk1 led to the cytostasis of cervical cancer cells. Finally, AT7519 and SNS‑032 inhibited cancer cell migration, invasion and angiogenesis in vitro, and suppressed lung metastases in a spontaneous metastasis model. On the whole, the findings of this study indicate that the utilization of AT7519 and SNS‑032 as part of an adjuvant treatment may help control cervical cancer progression.

BACKGROUND: Colorectal cancer is the leading cause of cancer-related deaths in Saudi Arabia. Cancer has a multifactorial nature and can be described as a disease of altered gene expression. The profiling of gene expression has been used to identify cancer subtypes and to predict patients' responsiveness. Telomere-associated proteins that regulate telomere biology are essential molecules in cancer development. Thus, the present study examined their contributions to colorectal cancer progression in Saudi patients.
METHODS: The expression of hTERT, TRF1, TRF2, POT1, ATR, ATM, Chk1 and Chk2 were measured via real-time PCR in matched cancerous and adjacent tissues of CRC patients. The protein level of hTERT, TRF1, TRF2, ATR, ATM, Chk1 and Chk2 were measured using immunohistochemistry. A region of hTERT core promoter was sequenced via Sanger sequencing. Methylation of CTCF binding site was examined via methylation-specific PCR. Finally, the length of telomere was estimated using q-PCR.
RESULTS: Our results showed that POT1, ATR, Chk1 and Chk2 show increased expression in CRC relative to the adjacent mucosa. The expression levels of each gene were associated with clinicopathological characteristics of patients with CRC. There was a positive correlation between the age of the patients and hTERT expression. Regarding tumor site, telomere length, ATR, ATM and Chk1 were shown to be altered. No somatic mutation was detected in hTERT core promoter, and no differences in methylation patterns at CTCF binding site in the promoter between normal and cancer tissues.
CONCLUSION: Analysis of targeted genes expression in colorectal cancer based on the clinical variables revealed that tumor location and age could have a role in gene expression and telomere length variations and this could be taken under consideration during CRC diagnosis and therapy. Other epigenetic mechanisms could influence hTERT expression in cancers. Our findings warrant further validation through experiments involving a larger number of patients.

BACKGROUND: This study compared tumor-related signaling pathways with known compounds to determine potential agents for lung adenocarcinoma (LUAD) treatment.
METHODS: Kyoto Encyclopedia of Genes and Genomes signaling pathway analyses were performed based on LUAD differentially expressed genes from The Cancer Genome Atlas (TCGA) project and genotype-tissue expression controls. These results were compared to various known compounds using the Connectivity Mapping dataset. The clinical significance of the hub genes identified by overlapping pathway enrichment analysis was further investigated using data mining from multiple sources. A drug-pathway network for LUAD was constructed, and molecular docking was carried out.
RESULTS: After the integration of 57 LUAD-related pathways and 35 pathways affected by small molecules, five overlapping pathways were revealed. Among these five pathways, the p53 signaling pathway was the most significant, with CCNB1, CCNB2, CDK1, CDKN2A, and CHEK1 being identified as hub genes. The p53 signaling pathway is implicated as a risk factor for LUAD tumorigenesis and survival. A total of 88 molecules significantly inhibiting the five LUAD-related oncogenic pathways were involved in the LUAD drug-pathway network. Daunorubicin, mycophenolic acid, and pyrvinium could potentially target the hub gene CHEK1 directly.
CONCLUSION: Our study highlights the critical pathways that should be targeted in the search for potential LUAD treatments, most importantly, the p53 signaling pathway. Some compounds, such as ciclopirox and AG-028671, may have potential roles for LUAD treatment but require further experimental verification.

Small cell lung cancer (SCLC) is one of the highly malignant tumors and a serious threat to human health. The aim of the present study was to explore the underlying molecular mechanisms of SCLC. mRNA microarray datasets GSE6044 and GSE11969 were downloaded from Gene Expression Omnibus database, and the differentially expressed genes (DEGs) between normal lung and SCLC samples were screened using GEO2R tool. Functional and pathway enrichment analyses were performed for common DEGs using the DAVID database, and the protein‑protein interaction (PPI) network of common DEGs was constructed by the STRING database and visualized with Cytoscape software. In addition, the hub genes in the network and module analysis of the PPI network were performed using CentiScaPe and plugin Molecular Complex Detection. Finally, the mRNA expression levels of hub genes were validated in the Oncomine database. A total of 150 common DEGs with absolute fold‑change >0.5, including 66 significantly downregulated DEGs and 84 upregulated DEGs were obtained. The Gene Ontology term enrichment analysis suggested that common upregulated DEGs were primarily enriched in biological processes (BPs), including 'cell cycle', 'cell cycle phase', 'M phase', 'cell cycle process' and 'DNA metabolic process'. The common downregulated genes were significantly enriched in BPs, including 'response to wounding', 'positive regulation of immune system process', 'immune response', 'acute inflammatory response' and 'inflammatory response'. Kyoto Encyclopedia of Genes and Genomes pathway analysis identified that the common downregulated DEGs were primarily enriched in the 'complement and coagulation cascades' signaling pathway; the common upregulated DEGs were mainly enriched in 'cell cycle', 'DNA replication', 'oocyte meiosis' and the 'mismatch repair' signaling pathways. From the PPI network, the top 10 hub genes in SCLC were selected, including topoisomerase IIα, proliferating cell nuclear antigen, replication factor C subunit 4, checkpoint kinase 1, thymidylate synthase, minichromosome maintenance protein (MCM) 2, cell division cycle (CDC) 20, cyclin dependent kinase inhibitor 3, MCM3 and CDC6, the mRNA levels of which are upregulated in Oncomine SCLC datasets with the exception of MCM2. Furthermore, the genes in the significant module were enriched in 'cell cycle', 'DNA replication' and 'oocyte meiosis' signaling pathways. Therefore, the present study can shed new light on the understanding of molecular mechanisms of SCLC and may provide molecular targets and diagnostic biomarkers for the treatment and early diagnosis of SCLC.

Neuroblastoma (NB), the most common extracranial solid tumor of childhood, causes death in almost 15% of children affected by cancer. Treatment of neuroblastoma is based on the combination of chemotherapy with other therapeutic interventions such as surgery, radiotherapy, use of differentiating agents, and immunotherapy. In particular, adoptive NK cell transfer is a new immune-therapeutic approach whose efficacy may be boosted by several anticancer agents able to induce the expression of ligands for NK cell-activating receptors, thus rendering cancer cells more susceptible to NK cell-mediated lysis. Here, we show that chemotherapeutic drugs commonly used for the treatment of NB such as cisplatin, topotecan, irinotecan, and etoposide are unable to induce the expression of activating ligands in a panel of NB cell lines. Consistently, cisplatin-treated NB cell lines were not more susceptible to NK cells than untreated cells. The refractoriness of NB cell lines to these drugs has been partially associated with the abnormal status of genes for ATM, ATR, Chk1, and Chk2, the major transducers of the DNA damage response (DDR), triggered by several anticancer agents and promoting different antitumor mechanisms including the expression of ligands for NK cell-activating receptors. Moreover, both the impaired production of reactive oxygen species (ROS) in some NB cell lines and the transient p53 stabilization in response to our genotoxic drugs under our experimental conditions could contribute to inefficient induction of activating ligands. These data suggest that further investigations, exploiting molecular strategies aimed to potentiate the NK cell-mediated immunotherapy of NB, are warranted.

OBJECTIVE: High grade astrocytoma (HGA) as an aggressive brain tumor, is always correlated with poor prognosis. In this paper, we aimed to explore the genetic prognostic biomarkers for HGA.
METHODS: The genome-wide expression profile of 26 brain tumor samples obtained from 26 patients with HGA was downloaded from Gene Expression Omnibus. The risk genes for prognosis of HGA were identified and verified by the data in TCGA database. Protein-protein interaction (PPI) network of risk factor genes was constructed and significant module was screened. Function and pathway annotations were performed for risk genes and drug target genes were further analyzed.
RESULTS: A total of 598 genes were identified as significant risk genes for prognosis, such as checkpoint kinase 1, potassium inwardly-rectifying channel, subfamily J, member 6, leukocyte receptor tyrosine kinase and uncharacterized LOC283887. All risk genes for prognosis of HGA were significantly enriched in cell cycle, mitotic as well as mitotic anaphase. While the genes in the network module mainly participated in functions such as cell cycle, mitotic cell cycle and cell cycle process. Moreover, the genes in the network module mainly participated in the pathways such as cell cycle and cell cycle, mitotic. Drug target analysis showed that seven genes were recorded in Drugbank database, and there were as many as 32 drug records of CHEK1.
CONCLUSION: The prognostic effect of CHEK1 was validated based on the expression profile data of 615 low-grade glioma and glioblastoma samples. We proposed CHEK1 as prognostic biomarker for HGA. Our work might provide the candidate target for HGA therapy.

Although radiotherapy often with chemotherapy has been shown to offer a survival benefit comparable with that of radical cystectomy in select patients with bladder cancer, the development of radiosensitization strategies may significantly enhance its application. Notably, emerging preclinical evidence has indicated the involvement of androgen receptor (AR) signaling in urothelial cancer progression. We here assessed whether AR signals could contribute to modulating radiosensitivity in bladder cancer cells. Ionizing radiation reduced the numbers of viable cells or colonies of AR-negative lines more significantly than those of AR-positive lines. Similarly, in AR-positive cells cultured in androgen-depleted conditions, dihydrotestosterone treatment lowered the effects of irradiation. Meanwhile, an antiandrogen hydroxyflutamide enhanced them in AR-positive cells cultured in the presence of androgens. AR knockdown or hydroxyflutamide treatment also resulted in a delay in DNA double-strand break repair 4-24 hours after irradiation. We then established "radiation-resistant" sublines and found considerable elevation of the expression of AR as well as DNA repair genes, such as

AIM: To investigate the effect of dioxonaphthoimidazolium analog YM155 on cell cycle progression of the clear-cell variant of renal cell carcinoma (ccRCC).
MAIN METHODS: Cell cycle analysis was performed using bromodeoxyuridine (BrdU) and PI, apoptosis initiation was monitored using Annexin V and proteins expression was determined using western immunoblotting.
KEY FINDINGS: Here, we showed that YM155 activated stress-related molecules (histone H2AX, checkpoint kinases Chk1 and Chk2, p53) that mediate DNA damage checkpoint responses. The coordinated activation of these effector molecules disrupts progression of the cell cycle at the S phase as deduced from BrdU pulsing experiments and the ensuing changes in the levels of proteins (cyclins, CDKs, CDK inhibitors, phosphatases) that control cell cycle progression. Notably, we found increases in cyclin E and Cdc2 which regulate transition of cells from G1 to S, even as losses were observed for other CDKs and their cyclin partners. Furthermore, by inducing a loss in total pRb possibly by promoting its degradation, YM155 promoted the E2F transcription of genes that regulate entry into the S phase. After 24 h, cell cycle arrest to repair YM155-inflicted DNA damage was overtaken by p53-mediated apoptosis. YM155 induced increases in pro-apoptotic proteins (Bax and Bad), diminished anti-apoptotic proteins (Mcl-1, Bcl-xl, XIAP, survivin) and initiated cleavage of apoptotic marker proteins caspase 3 and PARP.
SIGNIFICANCE: Taken together, the added insight provided on the cell cycle perturbative effects of YM155 may assist clinicians in framing rational choices for combining YM155 with other anti-cancer drugs or treatment modalities in ccRCC.

Microtubule-targeting agents (MTAs) are widely used for the treatment of non-small cell lung cancer (NSCLC). The response rate is only ∼25%, mainly attributable to drug resistance. To identify determinants of resistance in NSCLC, we performed a high-throughput screen using a library of miRNA mimics. Here we report that miR-195 synergizes with MTAs to inhibit the growth of NSCLC cells in vitro, that increased expression of miR-195 sensitizes NSCLC cells to MTAs and that repression of miR-195 confers resistance to MTAs. We show that NSCLC tumors over-expressing miR-195 are more sensitive to MTA treatment and that induced expression of miR-195 in NSCLC tumors potentiates the anti-tumor effect of MTAs. Additionally, we demonstrate that miR-195 targets checkpoint kinase 1 (CHEK1) to regulate the response of NSCLC cells to MTAs, that over-expression of CHEK1 contributes to resistance to MTAs and that knock-down of CHEK1 synergizes with MTAs to repress cell growth. Our results highlight the importance of miR-195 in regulating the response of NSCLC cells to MTAs and underline the potential application of miR-195 as a biomarker for response to MTAs, and as a therapeutic adjuvant to MTA treatment.