Minichromosome maintenance protein 2 is a strong independent prognostic marker in breast cancer

MCM-2 Levels as a Potential Biomarker for Predicting High-Risk Breast Cancer Patients According to TAILORx Classification

Background

The minichromosome maintenance protein-2 (MCM-2) is a more sensitive proliferation marker than Ki-67. This study aimed to evaluate the relationship between MCM-2 and Oncotype DX recurrence score (ODX-RS) and determine an MCM-2 cutoff value in high-risk patients according to TAILORx risk categorization.

Methods

Hormone receptor (HR) positive HER-2 negative early-stage breast cancer patients (pT1-2, pN0-N1, M0) who had ODX-RS were included in the study. According to the TAILORx trial, patients were divided into two groups with high (ODX-RS ≥26) and low risk (ODX-RS <26) in terms of ODX-RS. Formalin-fixed-paraffin-embedded tissues of patients were re-evaluated, and 3 µm sections were prepared for MCM-2 immuno-histochemical staining. The relationship between ODX-RS and the percentage of MCM-2 staining was evaluated in two groups. The ROC curve analysis was performed to determine the MCM-2 cut-off value for the TAILORx high-risk group (ODX-RS ≥26).

Results

The mean MCM-2 value was significantly higher in the high-risk group [(60.2 ± 11.2 vs 34.4 ± 13.8, p < 0.001)]. In the multivariate analysis, MCM-2 (OR: 1.27, 95% CI: 1.08-1.49, p = 0.003) and progesterone receptor (PR) levels ≤10% (OR: 60.9, 95% CI: 4.1-89.7, p = 0.003) were found to be independent factors indicating a high-risk group. A one-unit increase in MCM-2 level increased the likelihood of being in the high-risk group by 1.27 times. In the ROC curve analysis, the optimal MCM-2 cut-off level was 50 (AUC: 0.921, sensitivity: 86.7%, specificity: 96.0%, p < 0.001).

Conclusion

Our study is the first study in the literature to investigate the relationship between ODX-RS and MCM-2 levels in HR-positive HER-2 negative early breast-cancer patients. In this study, MCM-2 was an independent risk factor in identifying high-risk patients according to TAILORx risk classification. MCM 2 cut-off value (50) may help the decision on adjuvant chemotherapy in patients where the Oncotype DX test cannot be performed.

Expression of Minichromosome Maintenance Protein 2 (MCM2) in Oral Epithelial Dysplasia and Oral Squamous Cell Carcinoma: A Systematic Review

The histopathological investigations of oral lesions are a basic approach for diagnosing ongoing cancer or pre-cancer associated pathological attributes in the dissected biopsy. The early detection and management of potentially malignant disorders of the lip and oral cavity that require intervention may reduce malignant transformations, or in case any malignancy is detected during surveillance, the appropriate treatment may improve survival rates. This would guide the clinicians to decide the appropriate treatment modality or lesion to achieve a more favorable prognosis. MCM2 protein is involved in DNA replication providing additional information about the prognosis of neoplasms. Some authors have pointed out that MCM proteins have been inversely correlated with salivary tumour differentiation and therefore could be an indicator of proliferation potential. Therefore, it is essential to find the expression of the MCM2 gene in oral leukoplakia and oral squamous cell carcinoma. Electronic databases like Ebscohost, Livivo, Google Scholar and PubMed were searched. Based on the inclusion and exclusion criteria, 2 reviewers (MS and SN) independently selected the relevant articles. Any disagreement was discussed until a consensus was reached. We used the QUADAS-2 tool to assess the quality of the included studies over four key domains: patient selection, index test, reference standard and flow and timing of participants through the study. 10 out of 57 titles were found to meet the eligibility criteria. Biopsied tissue with immunohistochemical staining or advanced diagnostic studies were included. A total of 901 samples were included in the study and different groups were normal oral mucosa (NOM), oral epithelial dysplasia (OED) and oral squamous cell carcinoma (OSCC). MCM2 proteins are useful diagnostic markers for distinguishing malignant from benign epithelial dysplasia and for early detection and diagnosis of OSCC as an adjunct to clinicopathological parameters.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12070-022-03296-7.

Loss of Brca1 and Trp53 in adult mouse mammary ductal epithelium results in development of hormone receptor-positive or hormone receptor-negative tumors, depending on inactivation of Rb family proteins

BACKGROUND

Breast cancer is a heterogenous disease with several histological and molecular subtypes. Models that represent these subtypes are essential for translational research aimed at improving clinical strategy for targeted therapeutics.

METHODS

Different combinations of genetic aberrations (Brca1 and Trp53 loss, and inhibition of proteins of the Rb family) were induced in the mammary gland by injection of adenovirus expressing Cre recombinase into the mammary ducts of adult genetically engineered mice. Mammary tumors with different genetic aberrations were classified into molecular subtypes based on expression of molecular markers and RNAseq analysis. In vitro potency assays and Western blots were used to examine their drug sensitivities.

RESULTS

Induction of Brca1 and Trp53 loss in mammary ductal epithelium resulted in development of basal-like hormone receptor (HR)-negative mammary tumors. Inhibition of Rb and Trp53 loss or the combination of Rb, Trp53 and Brca1 aberrations resulted in development of luminal ductal carcinoma positive for ER, PR, and Her2 expression. HR positivity in tumors with Rb, Trp53 and Brca1 aberrations indicated that functionality of the Rb pathway rather than Brca1 status affected HR status in these models. Mammary tumor gene expression profiles recapitulated human basal-like or luminal B breast cancer signatures, but HR-positive luminal cancer models were endocrine resistant and exhibited upregulation of PI3K signaling and sensitivity to this pathway inhibition. Furthermore, both tumor subtypes were resistant to CDK4/6 inhibition.

CONCLUSIONS

Examination of molecular expression profiles and drug sensitivities of tumors indicate that these breast cancer models can be utilized as a translational platform for evaluation of targeted combinations to improve chemotherapeutic response in patients that no longer respond to hormone therapy or that are resistant to CDK4/6 inhibition.

MCM2 in human cancer: functions, mechanisms, and clinical significance

Background

Aberrant DNA replication is the main source of genomic instability that leads to tumorigenesis and progression. MCM2, a core subunit of eukaryotic helicase, plays a vital role in DNA replication. The dysfunction of MCM2 results in the occurrence and progression of multiple cancers through impairing DNA replication and cell proliferation.

Conclusions

MCM2 is a vital regulator in DNA replication. The overexpression of MCM2 was detected in multiple types of cancers, and the dysfunction of MCM2 was correlated with the progression and poor prognoses of malignant tumors. According to the altered expression of MCM2 and its correlation with clinicopathological features of cancer patients, MCM2 was thought to be a sensitive biomarker for cancer diagnosis, prognosis, and chemotherapy response. The anti-tumor effect induced by MCM2 inhibition implies the potential of MCM2 to be a novel therapeutic target for cancer treatment. Since DNA replication stress, which may stimulate anti-tumor immunity, frequently occurs in MCM2 deficient cells, it also proposes the possibility that MCM2 targeting improves the effect of tumor immunotherapy.

Multi-Omics Analysis of MCM2 as a Promising Biomarker in Pan-Cancer

Minichromosome maintenance 2 (MCM2) is a member of the minichromosomal maintenance family of proteins that mainly regulates DNA replication and the cell cycle and is involved in regulating cancer cell proliferation in various cancers. Previous studies have reported that MCM2 plays a pivotal role in cell proliferation and cancer development. However, few articles have systematically reported the pathogenic roles of MCM2 across cancers. Therefore, the present pan-cancer study was conducted. Various computational tools were used to investigate the MCM2 expression level, genetic mutation rate, and regulating mechanism, immune infiltration, tumor diagnosis and prognosis, therapeutic response and drug sensitivity of various cancers. The expression and function of MCM2 were examined by Western blotting and CCK-8 assays. MCM2 was significantly upregulated in almost all cancers and cancer subtypes in The Cancer Genome Atlas and was closely associated with tumor mutation burden, tumor stage, and immune therapy response. Upregulation of MCM2 expression may be correlated with a high level of alterations rate. MCM2 expression was associated with the infiltration of various immune cells and molecules and markedly associated with a poor prognosis. Western blotting and CCK-8 assays revealed that MCM2 expression was significantly upregulated in melanoma cell lines. Our results also suggested that MCM2 promotes cell proliferation in vitro by activating cell proliferation pathways such as the Akt signaling pathways. This study explored the oncogenic role of MCM2 across cancers, provided data on the underlying mechanisms of these cancers for further research and demonstrated that MCM2 may be a promising target for cancer immunotherapy.

MCM6 versus Ki-67 in diagnosis of luminal molecular subtypes of breast cancers

Background

Currently, breast cancers are divided into four major molecular subtypes. The distinction between the luminal A and luminal B subtypes is mainly based on the cellular proliferation indices and is assessed by the Ki-67 scoring. Due to the limitations in the assessment and expression of Ki-67, we hypothesized that minichromosome maintenance protein 6 (MCM6) might be taken as a surrogate marker to differentiate molecular subtypes and aid in more precise grading of tumors.

Methods

We performed a retrospective, cross-sectional study on 124 samples of breast cancer and 40 samples of normal breast tissue. Relevant clinical information was retrieved from the Cancer Institute database.

Results

MCM6 could discriminate between various categories of histologic grades, tubule formation, mitotic indices, and nuclear pleomorphism (P = 0.002 for tubule formation and P < 0.001 for other). Moreover, the MCM6 score exhibited a significant correlation with the mitotic count (P < 0.001). However, the Ki-67 score could not discriminate subgroups of the mitotic index and nuclear pleomorphism. Compared to the luminal A subtype, luminal B exhibited a higher MCM6 score (P = 0.01). Besides, MCM6 scores were higher for certain subtypes with more aggressive behaviors, such as hormone receptor (HR)-negative disease, and human epidermal growth factor receptor 2 (HER2)-enriched and triple-negative breast cancers, as there was a significantly higher MCM6 mean score in the HR-negative in comparison to the luminal breast cancers (P < 0.001). Similarly, higher MCM6 scores were observed among samples with more advanced nuclear grades, tubule formation, and overall grades.

Conclusion

MCM6 can differentiate luminal A and luminal B subtypes and is correlated with mitotic counts. However, this study was unable to prove the superiority of MCM6 in differentiating between molecular subtypes compared to the Ki-67 score. Nevertheless, in our study, MCM6 was superior to Ki-67 in exhibiting correlations with the mitotic grade, tubule formation, and nuclear grades. More studies are needed to standardize its assessment methods, determine more robust cut-off values, and evaluate its associations with prognostic features of breast cancer.

Minichromosome maintenance 2 is an independent predictor of survival in patients with lung adenocarcinoma

Minichromosome maintenance (MCM) protein deregulation is associated with tumor formation, progression and malignant transformation. MCM2 is frequently expressed during premalignant lung cell proliferation and is a sensitive marker for the early detection of pulmonary malignant lesions. The present study was undertaken to investigate whether MCM2 expression is of clinical and prognostic value in patients who have undergone lung adenocarcinoma resection. Between January 2009 and December 2010, 102 consecutive patients underwent complete pulmonary resection (involving lobectomy or more extensive resection) for lung adenocarcinoma at St. Marianna Medical University Hospital (Kanagawa, Japan). Among those, 73 patients, who had a final pathological diagnosis of lung adenocarcinoma measuring ≥10 mm, were enrolled in the present study. High MCM2 expression was found in 35 patients (48.0%). Univariate analysis of the overall survival (OS) revealed that pathological stage and MCM2 expression were significant prognostic factors in lung adenocarcinoma (P<0.001 and P<0.002, respectively). Univariate analysis of the recurrence-free survival (RFS), the significant prognostic factors included pathological stage, EGFR mutation status and MCM2 expression (P<0.001, P<0.034 and P<0.003, respectively). On multivariate survival analysis, high MCM2 expression and pathological stage II-III were identified as independent strong prognostic factors (OS: HR=5.084, 95% CI: 1.715-15.080, P=0.003; RFS: HR=2.761, 95% CI: 1.090-6.998, P=0.032). Therefore, the findings of the present study demonstrated that MCM2 may serve as a potential biomarker and therapeutic target for lung adenocarcinoma.

OB-Folds and Genome Maintenance: Targeting Protein-DNA Interactions for Cancer Therapy

Genome stability and maintenance pathways along with their requisite proteins are critical for the accurate duplication of genetic material, mutation avoidance, and suppression of human diseases including cancer. Many of these proteins participate in these pathways by binding directly to DNA, and a subset employ oligonucleotide/oligosaccharide binding folds (OB-fold) to facilitate the protein-DNA interactions. OB-fold motifs allow for sequence independent binding to single-stranded DNA (ssDNA) and can serve to position specific proteins at specific DNA structures and then, via protein-protein interaction motifs, assemble the machinery to catalyze the replication, repair, or recombination of DNA. This review provides an overview of the OB-fold structural organization of some of the most relevant OB-fold containing proteins for oncology and drug discovery. We discuss their individual roles in DNA metabolism, progress toward drugging these motifs and their utility as potential cancer therapeutics. While protein-DNA interactions were initially thought to be undruggable, recent reports of success with molecules targeting OB-fold containing proteins suggest otherwise. The potential for the development of agents targeting OB-folds is in its infancy, but if successful, would expand the opportunities to impinge on genome stability and maintenance pathways for more effective cancer treatment.

Expression and Prognostic Value of MCM Family Genes in Osteosarcoma

We performed a detailed cancer VS normal analysis to explore the expression and prognostic value of minichromosome maintenance (MCM) proteinsin human sarcoma. The mRNA expression levels of the MCM family genes in sarcoma were analyzed using data from ONCOMINE, GEPIA and CCLE databases. KEGG database was used to analyze the function of MCM2–7 complex in DNA replication and cell cycle. QRT-PCR and western blot were used to confirm the differential expression of key MCMs in osteosarcoma cell lines. Cell Counting Kit-8 and flow cytometry method were used to detect the cell proliferation and apoptosis of hFOB1.19 cells. The results showed that MCM1–7 and MCM10 were all upregulated in sarcoma in ONCOMINE database. MCM2, and MCM4–7 were highly expressed in sarcoma in GEPIA database. Moreover, all these ten factors were highly expressed in sarcoma cell lines. Furthermore, we analyzed the prognostic value of MCMs for sarcoma in GEPIA and found that MCM2, MCM3, MCM4, and MCM10 are prognostic biomarkers for human sarcoma. Analysis results using KEGG datasets showed that MCM4 and MCM6–7 constituted a core structure of MCM2-7 hexamers. We found that AzadC treatment and overexpression of MCM4 significantly promoted hFOB1.19 cell proliferation and inhibited apoptosis. The present study implied that MCM2–4 and 10 are potential biomarkers for the prognosis of sarcoma. The prognostic role of MCM4 may be attributable to the change in its DNA methylation patterns.

A Mechanism of Action Study on Danggui Sini Decoction to Discover Its Therapeutic Effect on Gastric Cancer

Danggui Sini Decoction (DSD), a classic Chinese herb medicine (CHM) formula, has been used to treat various diseases in China for centuries. However, it remains challenging to reveal its mechanism of action through conventional pharmacological methods. Here, we first explored the mechanism of action of DSD with the assistance of network pharmacology and bioinformatic analysis tools, and found a potential therapeutic effect of DSD on cancer. Indeed, our in vivo experiment demonstrated that oral administration of DSD could significantly inhibit the growth of xenografted gastric cancer (GC) on mice. The subsequent enrichment analyses for 123 candidate core targets evacuated from the drug/disease-target protein-protein interaction network showed that DSD could affect the key biological processes involving the survival and growth of GC cells, such as apoptosis and cell cycle, and the disturbance of these biological processes is likely attributed to the simultaneous inhibition of multiple signaling pathways, including PI3K/Akt, MAPK, and p53 pathways. Notably, these in silico results were further validated by a series of cellular functional and molecular biological assays in vitro. Moreover, molecular docking analysis suggested an important role of MCM2 in delivering the pharmacological activity of DSD against GC. Together, these results indicate that our network pharmacology and bioinformatics-guided approach is feasible and useful in exploring not only the mechanism of action, but also the "new use" of the old CHM formula.

Computational assessment of MCM2 transcriptional expression and identification of the prognostic biomarker for human breast cancer

Minichromosome maintenance protein 2 (MCM2) is a highly conserved protein from the MCM protein family that plays an important role in eukaryotic DNA replication as well as in cell cycle progression. In addition, it maintains the ploidy level consistency in eukaryotic cells, hence, mutations or alteration of this protein could result in the disintegration of the fine-tuned molecular machinery that can lead to uncontrolled cell proliferation. Moreover, MCM2 has been found to be an important marker for progression and prognosis in different cancers. Therefore, we aimed to analyze the MCM2 expression and the associated outcome in breast cancer (BC) patients based on the publicly available online databases. In this study, server-based gene expression analyses indicate the upregulation of MCM2 (p < 10^-6; fold change>2.0) in various BC subtypes as compared to the respective normal tissues. Besides, the evaluation of histological sections from healthy and cancer tissues showed strong staining signals indicating higher expression of MCM2 protein. The overexpression of MCM2 was significantly correlated to promoter methylation and was related to patients' clinical features. Further, mutation analysis suggested missense as the predominant type of mutation (71.4%) with 18 copy-number alterations and 0.2% mutation frequency in the MCM2 gene. This study revealed a significant correlation (Cox p ≤ 0.05) between the higher MCM2 expression and lower patient survival. Finally, we identified the co-expressed genes with gene ontological features and signaling pathways associated in BC development. We believe that this study will provide a basis for MCM2 to be a significant biomarker for human BC prognosis.

Toward a holistic view of multiscale breast cancer molecular biomarkers

Powered by rapid technology developments, biomarkers become increasingly diverse, including those detected at genomic, transcriptomic, proteomic, metabolomic and cellular levels. While diverse sets of biomarkers have been utilized in breast cancer predisposition, diagnosis, prognosis, treatment and management, recent additions derived from lincRNA, circular RNA, circulating DNA together with its methylated and hydroxymethylated forms and immune signatures are likely to further transform clinical practice. Here, we take breast cancer as an example of heterogeneous diseases that require many informed decisions from treatment to care to review the huge variety of biomarkers. By assessing the advantages and limitations of modern biomarkers in diverse use scenarios, this article outlines the prospects and challenges of releasing complimentary advantages by augmentation of multiscale molecular biomarkers.

MCM2, MCM4, and MCM6 in Breast Cancer: Clinical Utility in Diagnosis and Prognosis

Breast cancer is a heterogeneous disease comprising the estrogen receptor (ER)-positive luminal subtype which is subdivided into luminal A and luminal B and ER-negative breast cancer which includes the triple-negative subtype. This study has four aims: 1) to examine whether Minichromosome Maintenance (MCM)2, MCM4, and MCM6 can be used as markers to differentiate between luminal A and luminal B subtypes; 2) to study whether MCM2, MCM4, and MCM6 are highly expressed in triple-negative breast cancer, as there is an urgent need to search for surrogate markers in this aggressive subtype, for drug development purposes; 3) to compare the prognostic values of these markers in predicting relapse-free survival; and 4) to compare the three approaches used for scoring the protein expression of these markers by immunohistochemistry (IHC). MCM2, MCM4, MCM6, and MKI67 mRNA expression was first studied using in silico analysis of available breast cancer datasets. We next used IHC to evaluate their protein expression on tissue microarrays using three scoring methods. MCM2, MCM4, and MCM6 can help in distinction between luminal A and luminal B whose therapeutic management and clinical outcomes are different. MCM2, MCM4, MCM6, and Ki-67 are highly expressed in breast cancer of high histological grades that comprise clinically aggressive tumors such as luminal B, HER2-positive, and triple-negative subtypes. Low transcript expression of these markers is associated with increased probability of relapse-free survival. A positive relationship exists among the three scoring methods of each of the four markers. An independent validation cohort is needed to confirm their clinical utility.

The role of Ki-67 in Asian triple negative breast cancers: a novel combinatory panel approach

The proliferation marker Ki-67 is frequently used to assess aggressiveness in the pathological evaluation of cancer, but its role remains uncertain in triple-negative breast cancer (TNBC). We aimed to quantify and localize Ki-67 expression in both epithelial and immune compartments in TNBC and investigate its association with clinicopathological parameters and survival outcomes. A total of 406 TNBC cases diagnosed between 2003 and 2015 at Singapore General Hospital were recruited. Using state-of-the-art, 7-colour multiplex immunofluorescence (mIF) tissue microarrays (TMAs) were stained to assess the abundance, density and spatial distribution of Ki-67-positive tumour cells and immune cells co-decorated with cytokeratin (CK) and leukocyte common antigen (CD45) respectively. Furthermore, MKI67 mRNA profiles were analysed using NanoString technology. In multivariate analysis adjusted for tumour size, histologic grade, age at diagnosis, and lymph node stage, a high Ki-67 labelling index (LI) > 0.3% was associated with improved disease-free survival (DFS; HR = 0.727; p = 0.027). High Ki-67-positive immune cell count per TMA was a favourable prognostic marker for both DFS (HR = 0.379; p = 0.00153) and overall survival (OS; HR = 0.473; p = 0.0482). The combination of high Ki-67 LI and high MKI67 expression was associated with improved DFS (HR = 0.239; p = 0.00639) and OS (HR = 0.213; p = 0.034). This study is among the first to highlight that Ki-67 is associated with favourable prognosis in an adjuvant setting in TNBC, and the mIF-based evaluation of Ki-67 expression on both tumour and immune cells represents a novel prognostic approach.

Genome-wide investigation of the clinical significance and prospective molecular mechanism of minichromosome maintenance protein family genes in patients with Lung Adenocarcinoma

Our current study is to identify clinical significance of minichromosome maintenance (MCM) gene expression in Lung Adenocarcinoma (LUAD) using genome-wide RNA sequencing (RNA-seq) dataset and bioinformatics analysis tools. The biological function and potential process for function of the MCM1-10 were identified by multiple bioinformatics analysis tools. Clinical significance and molecular mechanism of the MCM1-10 were investigated by the RNA-seq dataset of LUAD from The Cancer Genome Atlas. Functional assessment substantiated involvement of MCM1-10 in cell cycle progression and DNA replication, and co-expressed with each other. We also observed that the MCM1-10 were dysregulation in LUAD tumor tissues, and may be have diagnostic implications in LUAD. Prognosis analysis in TCGA and KM plotter cohorts suggest that high abundance of MCM5, MCM8 and MCM4 notably correlated to poor LUAD overall survival. Mechanistic exploration of MCM4, MCM5, and MCM8 by gene set enrichment analysis suggests that these genes may influence the LUAD prognosis by regulating the cell cycle, DNA replication and other multiple biological processes and pathways. In comclusion, our study suggests that MCM1-10 can serve as diagnostic biomarkers for LUAD patients. Of them, MCM4, MCM5, and MCM8 may act as potential prognostic indicators for LUAD.

Exploring the Molecular Mechanism of the Drug-Treated Breast Cancer Based on Gene Expression Microarray

: Breast cancer (BRCA) remains the leading cause of cancer morbidity and mortality worldwide. In the present study, we identified novel biomarkers expressed during estradiol and tamoxifen treatment of BRCA. The microarray dataset of E-MTAB-4975 from Array Express database was downloaded, and the differential expressed genes (DEGs) between estradiol-treated BRCA sample and tamoxifen-treated BRCA sample were identified by limma package. The pathway and gene ontology (GO) enrichment analysis, construction of protein-protein interaction (PPI) network, module analysis, construction of target genes-miRNA interaction network and target genes-transcription factor (TF) interaction network were performed using bioinformatics tools. The expression, prognostic values, and mutation of hub genes were validated by SurvExpress database, cBioPortal, and human protein atlas (HPA) database. A total of 856 genes (421 up-regulated genes and 435 down-regulated genes) were identified in T47D (overexpressing Split Ends (SPEN) + estradiol) samples compared to T47D (overexpressing Split Ends (SPEN) + tamoxifen) samples. Pathway and GO enrichment analysis revealed that the DEGs were mainly enriched in response to lysine degradation II (pipecolate pathway), cholesterol biosynthesis pathway, cell cycle pathway, and response to cytokine pathway. DEGs (MCM2, TCF4, OLR1, HSPA5, MAP1LC3B, SQSTM1, NEU1, HIST1H1B, RAD51, RFC3, MCM10, ISG15, TNFRSF10B, GBP2, IGFBP5, SOD2, DHF and MT1H) , which were significantly up- and down-regulated in estradiol and tamoxifen-treated BRCA samples, were selected as hub genes according to the results of protein-protein interaction (PPI) network, module analysis, target genes-miRNA interaction network and target genes-TF interaction network analysis. The SurvExpress database, cBioPortal, and Human Protein Atlas (HPA) database further confirmed that patients with higher expression levels of these hub genes experienced a shorter overall survival. A comprehensive bioinformatics analysis was performed, and potential therapeutic applications of estradiol and tamoxifen were predicted in BRCA samples. The data may unravel the future molecular mechanisms of BRCA.

Evaluation of the diagnostic and therapeutic roles of non-coding RNA and cell proliferation related gene association in hepatocellular carcinoma

Micro RNA-34a-5p (miR-34a-5p) is an important molecule that can act as a modulator of tumor growth. It controls expression of a plenty of proteins controlling cell cycle, differentiation and apoptosis and opposing processes that favor viability of cancer cells, their metastasis and resistance to chemotherapy. Bioinformatics analysis indicated that minichromosome maintenance protein 2 (MCM2) is a target gene of miR-34a-p. In this study, RT-qPCR was employed to detect the expression of miR-34a-5p and MCM2 in 10 hepatocellular carcinoma (HCC) tissues. The functional role of miR-34a-5p in HCC was investigated and the interaction between miR-34a-5p and MCM2 was explored. Results showed miR-34a-5p expression in HCC tissues was significantly lower than in non HCC liver tissues (P < 0.05), but MCM2 expression in HCC tissues was markedly higher than in non HCC liver tissues (P < 0.05). In addition, miR-34a-5p expression was negatively related to MCM2 expression. To confirm effect of miR-34a-5p on tumor growth and its possible effect on MCM2, miR-34a-5p mimic and inhibitor was transfected into HCC cell lines (HepG2). MTS assay, showed miR-34a-5p over-expression could inhibit the proliferation of HCC cells. RT-qPCR was done to detect the expression of miR-34a-5p and MCM2 in HepG2 cells before and after transfection. Results showed that MCM2 expression in HCC tissues was markedly lower in mimic transfected group than in inhibitor transfected group and control group (P < 0.05) while miR-34a-5p expression in HepG2 cells was significantly higher in mimic transfected group than in inhibitor transfected group and control group (P < 0.05). Thus, miR-34a-5p may inhibit the proliferation of HCC cells via regulating MCM2 expression. These findings provide an evidence for the emerging role of microRNAs as diagnostic markers and therapeutic targets in HCC.

Fluoro-Chromogenic Labelling for Detection of MCM2 to Assess Proliferation Activity in HER2-amplified Breast Carcinomas

Minichromosome Maintenance Protein 2 (MCM2) is critical in initiating DNA replication during the cell division process. As expressed intensively in all phases of the active cell cycle, MCM2 has been proposed as a novel biomarker to determine cellular proliferation. We aimed at clarifying the prevalence and clinical significance of MCM2 in HER2-amplified breast cancer subtype. MCM2 expression was studied in 142 primary HER2-amplified breast carcinomas by applying a novel fluoro-chromogenic immunohistochemistry and tailored digital image analysis to determine labelling index (MCM2-LI). The presence of MCM2 was detected with HRP-conjugated polymer and visualized with 3, 3'-diaminobenzidine tetrahydrochloride, in cytokeratin (CK)-positive and Cy2-IgG-labelled breast cancer cells of epithelial origin. Stained slides were digitized by scanning sequentially under bright field (for MCM2) and fluorescence (for CK) illumination. Multilayer JPEG2000 images were analyzed with ImmunoRatio 2.5 (accessory in SlideVantage 1.2 software) utilizing its bright field and fluorescence image-blending mode to display MCM2-CK dual-positive cells. MCM2-LI was retrospectively compared with histopathologic characteristics and patients' clinical outcome. MCM2 protein-expressing cells (median MCM2-LI, 63.5%) were more frequent than those of Ki67 (median Ki67 labelling index, 33%). Significant correlations were found between high MCM2-LI, high Ki67 labelling index, negative hormone receptor (ER, PR) statuses, high grade of malignancy, and high cyclin E expression. MCM2-LI was not shown to be predictive of disease recurrence during the median follow-up of 5.3 years but was shown to be useful to distinguish aggressive-type HER2-amplified breast carcinomas with high malignancy grade and hormone receptor negativity. The fluoro-chromogenic double-labelling immunohistochemistry accompanied with digital image analysis provides an accurate carcinoma-specific determination of MCM2-LI on a single tumor section.

Assessment of Proliferative Index Between the Tumor Margin, Center of Tumor, and the Invasive Tumor Front of Oral Squamous Cell Carcinoma With the Help of Mcm-2: An Immunohistochemical Study

AIM

The knowledge of cellular proteins that involves cell cycle and its control system is essential for understanding tumor biology. Minichromosome maintenance protein (Mcm-2), a component of prereplicative complex, essential for initiating DNA replication, is deregulated in different malignant lesions, and is expressed throughout the whole cell cycle including the G0 and G1 phases. This characteristic cell cycle event is not found in other proliferative markers such as geminin, AgNOR, Ki-67, and proliferating cell nuclear antigen. The aim of the present study was to analyze and compare the expression of Mcm-2 in normal oral mucosa (NM) and oral squamous cell carcinomas at tumor margins (TM), the tumor center (TC), and the invasive tumor front (ITF), with correlation of clinicopathologic features.

MATERIALS AND METHODS

Tissues from 50 oral squamous cell carcinomas and 10 NM were archived retrospectively and stained with an antibody directed against the Mcm-2 antigen. A quantitative method was used to score the Mcm-2 expression in NM, TM, TC, and ITF. Nuclei labeling index for each case was estimated as the percentage of immunoreactive nuclei among 500 cells separately for NM, TM, TC, and ITF.

RESULTS

Nuclei labeling index increases progressively from NM (49.08%), TM (67.79%), and TC (76.87%) to ITF (87.77%).

CONCLUSIONS

Cell proliferation by Mcm-2 at the ITF had a strong positive relationship with TC, TM. Mcm-2, a pan-cell cycle marker, is more sensitive in comparison with other conventional proliferative markers, which can be a better prognostic indicator.

Control of DNA Replication Initiation by Ubiquitin

Eukaryotic cells divide by accomplishing a program of events in which the replication of the genome is a fundamental part. To ensure all cells have an accurate copy of the genome, DNA replication occurs only once per cell cycle and is controlled by numerous pathways. A key step in this process is the initiation of DNA replication in which certain regions of DNA are marked as competent to replicate. Moreover, initiation of DNA replication needs to be coordinated with other cell cycle processes. At the molecular level, initiation of DNA replication relies, among other mechanisms, upon post-translational modifications, including the conjugation and hydrolysis of ubiquitin. An example is the precise control of the levels of the DNA replication initiation protein Cdt1 and its inhibitor Geminin by ubiquitin-mediated proteasomal degradation. This control ensures that DNA replication occurs with the right timing during the cell cycle, thereby avoiding re-replication events. Here, we review the events that involve ubiquitin signalling during DNA replication initiation, and how they are linked to human disease.

Prognostic value of minichromosome maintenance mRNA expression in early-stage pancreatic ductal adenocarcinoma patients after pancreaticoduodenectomy

Background

The aim of the current study was to investigate the potential prognostic value of minichromosome maintenance (MCM) genes in patients with early-stage pancreatic ductal adenocarcinoma (PDAC) after pancreaticoduodenectomy by using the RNA-sequencing dataset from The Cancer Genome Atlas (TCGA).

Methods

An RNA-sequencing dataset of 112 early-stage PDAC patients who received a pancreaticoduodenectomy was obtained from TCGA. Survival analysis was used to identify potential prognostic values of MCM genes in PDAC overall survival (OS).

Results

Through mining public databases, we observed that MCM genes (MCM2, MCM3, MCM4, MCM5, MCM6, and MCM7) were upregulated in pancreatic cancer tumor tissue and have a strong positive coexpression with each other. Multivariate survival analysis indicated that a high expression of MCM4 significantly increased the risk of death in patients with PDAC, and time-dependent receiver operating characteristic analysis showed an area under the curve of 0.655, 0.587, and 0.509 for a 1-, 2-, and 3-year PDAC OS prediction, respectively. Comprehensive survival analysis of MCM4 using stratified and joint effects survival analysis suggests that MCM4 may be an independent prognostic indicator for PDAC OS. Gene set enrichment analysis indicated that MCM4 may participate in multiple biologic processes and pathways, including DNA replication, cell cycle, tumor protein p53, and Notch signaling pathways, thereby affecting prognosis of PDAC patients.

Conclusions

Our study indicates that MCM2–7 were upregulated in pancreatic cancer tumor tissues, and mRNA expression of MCM4 may serve as an independent prognostic indicator for PDAC OS prediction after pancreaticoduodenectomy.

Distinct Diagnostic and Prognostic Values of Minichromosome Maintenance Gene Expression in Patients with Hepatocellular Carcinoma

Background: The aim of the present study was to identify diagnostic and prognostic values of minichromosome maintenance (MCM) gene expression in patients with hepatocellular carcinoma (HCC).

Methods: The biological function of the MCM genes were investigated by bioinformatics analysis. The diagnostic and prognostic values of the MCM genes were investigated by using the data of HCC patients from the GSE14520 and The Cancer Genome Atlas (TCGA) databases.

Results: Bioinformatics analysis of the MCM genes substantiated that MCM2-7 genes were significantly enriched in DNA replication and cell cycle, and co-expressed with each other. These genes also co-expressed in HCC tumor tissue in both the GSE14520 and TCGA cohort. We also observed that the expression of the MCM2-7 genes was increased in tumor tissue, and diagnostic receiver operating characteristic analysis of MCM2-7 indicated that these genes could serve as sensitive diagnostic markers in HCC. Survival analysis in the GSE14520 cohort suggested that expression of MCM2, MCM4, MCM5, and MCM6 were significantly associated with hepatitis B virus-related HCC overall survival (OS). However, none of the MCM genes were associated with recurrence-free survival in the GSE14520 cohort. The validation cohort of TCGA suggested that the expression of MCM2, MCM6, and MCM7 were significantly correlated with HCC OS.

Conclusion: Our study indicated that MCM2-7 genes may be potential diagnostic biomarkers in patients with HCC. Among them, MCM2 and MCM6 may serve as potential prognostic biomarkers for HCC.

The Human Replicative Helicase, the CMG Complex, as a Target for Anti-cancer Therapy

DNA helicases unwind or rearrange duplex DNA during replication, recombination and repair. Helicases of many pathogenic organisms such as viruses, bacteria, and protozoa have been studied as potential therapeutic targets to treat infectious diseases, and human DNA helicases as potential targets for anti-cancer therapy. DNA replication machineries perform essential tasks duplicating genome in every cell cycle, and one of the important functions of these machineries are played by DNA helicases. Replicative helicases are usually multi-subunit protein complexes, and the minimal complex active as eukaryotic replicative helicase is composed of 11 subunits, requiring a functional assembly of two subcomplexes and one protein. The hetero-hexameric MCM2-7 helicase is activated by forming a complex with Cdc45 and the hetero-tetrameric GINS complex; the Cdc45-Mcm2-7-GINS (CMG) complex. The CMG complex can be a potential target for a treatment of cancer and the feasibility of this replicative helicase as a therapeutic target has been tested recently. Several different strategies have been implemented and are under active investigations to interfere with helicase activity of the CMG complex. This review focuses on the molecular function of the CMG helicase during DNA replication and its relevance to cancers based on data published in the literature. In addition, current efforts made to identify small molecules inhibiting the CMG helicase to develop anti-cancer therapeutic strategies were summarized, with new perspectives to advance the discovery of the CMG-targeting drugs.

MCMs expression in lung cancer: implication of prognostic significance

Minichromosome Maintenance (MCM) proteins play essential roles in various cancers. We previously reported that MCM7 could be a prognostic biomarker in non-small cell lung cancer (NSCLC). The purpose of current study is to explore roles of other MCM proteins in NSCLC and their correlation with clinico-pathologic parameters of NSCLC patients. We evaluated the expression of MCM2, MCM5 and MCM6 immunohistochemically in 571 primary NSCLC samples. High expression of MCM2, MCM5 and MCM6 was detected in 42.2%, 38.3% and 52.9% of tumor tissues, respectively. The expression of MCM2, MCM5 and MCM6 was significantly associated with gender (P = 0.00004, 0.00004, 0.008), tumor type (P < 0.00001, < 0.00001, 0.00001) and smoking history (P = 0.009, 0.00043, 0.002). MCM2 and MCM5 were detected more in central-type lung cancer (P< 0.006, 0.016). Higher labeling index (LI) of MCM2 was observed more frequently in aged patients (P = 0.023) and in those at later stage (P = 0.001). Higher MCM5 LIs was detected more in patients with distant metastasis (P = 0.008). Kaplan-Meier curves indicated that early-stage (stage I/II) patients with higher MCM2 LIs had a poorer OS compared to those with lower LIs (P = 0.021). And lung squamous cell carcinoma (SCC) patients presenting high MCM5 expression had shorter OS (P = 0.015). Multivariate Cox regression analysis showed that MCM5 was an independent prognostic indicator (P = 0.035, HR = 1.586, 95%CI: 1.032-2.437). We reported for the first time that higher MCM5 LIs could be an independent adverse prognostic biomarker for SCC patients.

MCM2: An alternative to Ki-67 for measuring breast cancer cell proliferation

Breast cancer is a heterogeneous disease comprising a diversity of tumor subtypes that manifest themselves in a wide variety of clinical, pathological, and molecular features. One important subset, luminal breast cancers, comprises two clinically distinct subtypes luminal A and B each of them endowed with its own genetic program of differentiation and proliferation. Luminal breast cancers were operationally defined as follows: Luminal A: ER+, PR+, HER2-, Ki-67<14% and Luminal B: ER+ and/or PR+, HER2-,Ki-67≥14% or, alternatively ER+ and/or PR+, HER2+, any Ki-67. There is currently a need for a clinically robust and validated immunohistochemical assay that can help distinguish between luminal A and B breast cancer. MCM2 is a family member of the minichromosome maintenance protein complex whose role in DNA replication and cell proliferation is firmly established. As MCM2 appears to be an attractive alternative to Ki-67, we sought to study the expression of MCM2 and Ki-67 in different histological grades and molecular subtypes of breast cancer focusing primarily on ER-positive tumors. MCM2 and Ki-67 mRNA expression were studied using in silico analysis of available DNA microarray and RNA-sequencing data of human breast cancer. We next used immunohistochemistry to evaluate protein expression of MCM2 and Ki-67 on tissue microarrays of invasive breast carcinoma. We found that MCM2 and Ki-67 are highly expressed in breast tumors of high histological grades, comprising clinically aggressive tumors such as triple-negative, HER2-positive and luminal B subtypes. MCM2 expression was detected at higher levels than that of Ki-67 in normal breast tissues and in breast cancers. The bimodal distribution of MCM2 scores in ER+/HER2- breast tumors led to the identification of two distinct subgroups with different relapse-free survival rates. In conclusion, MCM2 expression can help sorting out two clinically important subsets of luminal breast cancer whose treatment and clinical outcomes are likely to diverge.

The prognostic significance of Cdc6 and Cdt1 in breast cancer

DNA replication is a critical step in cell proliferation. Overexpression of MCM2-7 genes correlated with poor prognosis in breast cancer patients. However, the roles of Cdc6 and Cdt1, which work with MCMs to regulate DNA replication, in breast cancers are largely unknown. In the present study, we have shown that the expression levels of Cdc6 and Cdt1 were both significantly correlated with an increasing number of MCM2-7 genes overexpression. Both Cdc6 and Cdt1, when expressed in a high level, alone or in combination, were significantly associated with poorer survival in the breast cancer patient cohort (n = 1441). In line with this finding, the expression of Cdc6 and Cdt1 was upregulated in breast cancer cells compared to normal breast epithelial cells. Expression of Cdc6 and Cdt1 was significantly higher in ER negative breast cancer, and was suppressed when ER signalling was inhibited either by tamoxifen in vitro or letrozole in human subjects. Importantly, breast cancer patients who responded to letrozole expressed significantly lower Cdc6 than those patients who did not respond. Our results suggest that Cdc6 is a potential prognostic marker and therapeutic target in breast cancer patients.

MCM7 expression is a promising predictor of recurrence in patients surgically resected for meningiomas

Patients with high risk of recurrence after meningioma resection might benefit from adjuvant radiation therapy and closer clinical follow-up. While the World Health Organization (WHO) classification and the MIB-1 biomarker are applied in the clinical practice to identify these patients, the reliability of these methods is questionable. To improve the prediction of tumor recurrence, this study evaluated and compared the prognostic usefulness of the biomarker MCM7 with the conventional mitotic index and the MIB-1 biomarker. One hundred sixty patients were retrospectively analyzed. The expression of MIB-1 and MCM7 was determined as proliferative indices (PI-percentage of positive immunoreactive cells among 1000 tumor cells) in tissue microarrays. MCM7 PI revealed significantly higher indices in recurrent meningiomas compared with non-recurrent meningiomas (p = 0.020), while mitotic index and MIB-1 PI did not reach statistical significance (p ≥ 0.547). The optimal cutoff values for recurrence prediction were 3% for MIB-1 PI and 8% for MCM7 PI. MCM7 PI was significantly associated with recurrence-free survival in COX multivariate survival analyses (p = 0.005), while no association was found with mitotic index or MIB-1 (p ≥ 0.153). MCM7 PI allowed for the most accurate prediction of recurrence, obtaining the highest sensitivity and the greatest area under the ROC curve. These results proved that MCM7 PI is a better method for identifying patients with risk of recurrence compared with the traditional methods used in the current clinical practice. MCM7 may thus improve diagnostics, prediction of prognosis and treatment decision making in patients suffering from meningiomas.

Ki67, PCNA, and MCM proteins: Markers of proliferation in the diagnosis of breast cancer

The proliferative activity of tumour cells represents an important prognostic marker in the diagnosis of cancer. One of the methods for assessing the proliferative activity of cells is the immunohistochemical detection of cell cycle-specific antigens. For example, Ki67, proliferating cell nuclear antigen (PCNA), and minichromosome maintenance (MCM) proteins are standard markers of proliferation that are commonly used to assess the growth fraction of a cell population. The function of Ki67, the widely used marker of proliferation, still remains unclear. In contrast, PCNA and MCM proteins have been identified as important participants of DNA replication. All three proteins only manifest their expression during the cell division of normal and neoplastic cells. Since the expression of these proliferative markers was confirmed in several malignant tumours, their prognostic and predictive values have been evaluated to determine their significance in the diagnosis of cancer. This review offers insight into the discovery of the abovementioned proteins, as well as their current molecular and biological importance. In addition, the functions and properties of all three proteins and their use as markers of proliferation in the diagnosis of breast cancer are described. This work also reveals new findings about the role of Ki67 during the mitotic phase of the cell cycle. Finally, information is provided about the advantages and disadvantages of using all three antigens in the diagnosis of cancer.

Digital imaging in the immunohistochemical evaluation of the proliferation markers Ki67, MCM2 and Geminin, in early breast cancer, and their putative prognostic value

Background

Immunohistochemical assessment of proliferation may provide additional prognostic information in early breast cancer. However, due to a lack of methodological standards proliferation markers are still not routinely used for determining therapy. Even for Ki67, one of the most widely-studied markers, disagreements over the optimal cutoff exist. Improvements in digital microscopy may provide new avenues to standardise and make data more reproducible.

Methods

We studied the immunohistochemical expression of three markers of proliferation: Ki67, Mini-Chromosome Maintenance protein 2 and Geminin, by conventional light microscope and digital imaging on triplicate TMAs from 309 consecutive cases of primary breast cancers. Differences between the average and the maximum percentage reactivity in tumour cell nuclei from the three TMA cores were investigated to assess the validity of the approach. Time-dependent Receiver Operating Characteristic curves were utilized to obtain optimal expression level cut-offs, which were then correlated with clinico-pathological features and survival.

Results

High concordance between conventional and digital scores was observed for all 3 markers (Ki67: r_s = 0.87, P < 0.001; MCM2: r_s = 0.94, P < 0.001; and Geminin: r_s = 0.86, P < 0.001; Spearman’s rank). There was no significant difference according to the number of TMA cores included for either Ki67 or MCM2; analysis of two or three cores produced comparable results. Higher levels of all three proliferation markers were significantly associated with higher grade (P < 0.001) and ER-negativity (P < 0.001). Optimal prognostic cut-offs for percentage expression in the tumour were 8 %, 12 and 2.33 % for Ki67, MCM2 and Geminin respectively. All 3 proliferation marker cutoffs were predictive of 15-year breast cancer-specific survival in univariable Cox regression analyses. In multivariable analysis only lymph node status (HR = 3.9, 95 % CI = 1.79-8.5, P = 0.0006) and histological grade (HR = 1.84, 95 % CI = 1–3.38, P = 0.05) remained significantly prognostic.

Conclusions

Here we show that. MCM2 is a more sensitive marker of proliferation than Ki67 and should be examined in future studies, especially in the lymph node-negative, hormone receptor-positive subgroup. Further, digital microscopy can be used effectively as a high-throughput method to evaluate immunohistochemical expression.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1531-3) contains supplementary material, which is available to authorized users.

Characterization of the Tyrosine Kinase-Regulated Proteome in Breast Cancer by Combined use of RNA interference (RNAi) and Stable Isotope Labeling with Amino Acids in Cell Culture (SILAC) Quantitative Proteomics

Tyrosine kinases (TKs) are central regulators in cellular activities and perturbations of TK signaling contribute to oncogenesis. However, less than half of the TKs have been thoroughly studied and a global functional analysis of their proteomic portrait is lacking. Here we conducted a combined approach of RNA interference (RNAi) and stable isotope labeling with amino acids in cell culture (SILAC)-based quantitative proteomics to decode the TK-regulated proteome and associated signaling dynamics. As a result, a broad proteomic repertoire modulated by TKs was revealed, upon silencing of the 65 TKs expressed in MCF7 breast cancer cells. This yielded 10 new distinctive TK clusters according to similarity in TK-regulated proteome, each characterized by a unique signaling signature in contrast to previous classifications. We provide functional analyses and identify critical pathways for each cluster based on their common downstream targets. Analysis of different breast cancer subtypes showed distinct correlations of each cluster with clinical outcome. From the significantly up- and down-regulated proteins, we identified a number of markers of drug sensitivity and resistance. These data supports the role of TKs in regulating major aspects of cellular activity, but also reveals redundancy in signaling, explaining why kinase inhibitors alone often fail to achieve their clinical aims. The TK-SILACepedia provides a comprehensive resource for studying the global function of TKs in cancer.

Deregulation of the replisome factor MCMBP prompts oncogenesis in colorectal carcinomas through chromosomal instability

Genetic instability has emerged as an important hallmark of human neoplasia. Although most types of cancers exhibit genetic instability to some extent, in colorectal cancers genetic instability is a distinctive characteristic. Recent studies have shown that deregulation of genes involved in sister chromatid cohesion can result in chromosomal instability in colorectal cancers. Here, we show that the replisome factor minichromosome maintenance complex–binding protein (MCMBP), which is directly involved in the dynamics of the minichromosome maintenance complex and contributes to maintaining sister chromatid cohesion, is transcriptionally misregulated in different types of carcinomas. Cellular studies revealed that both MCMBP knockdown and overexpression in different breast and colorectal cell lines is associated with the emergence of a subpopulation of cells with abnormal nuclear morphology that likely arise as a consequence of aberrant cohesion events. Association analysis integrating gene expression data with clinical information revealed that enhanced MCMBP transcript levels correlate with an increased probability of relapse risk in colorectal cancers and different types of carcinomas. Moreover, a detailed study of a cohort of colorectal tumors showed that the MCMBP protein accumulates to high levels in cancer cells, whereas in normal proliferating tissue its abundance is low, indicating that MCMBP could be exploited as a novel diagnostic marker for this type of carcinoma.

Potential therapeutic mechanism of genistein in breast cancer involves inhibition of cell cycle regulation

Genistein can prevent tumorigenesis and reduce the incidence of diseases that are dependent upon estrogen. Previous research, however, has shown that genistein can also increase the risk of breast cancer. Thus, the aim of the present study was to investigate the mechanism underlying the effect of genistein in breast cancer and to determine whether genistein produces a therapeutic effect or promotes the development of breast cancer. Gene microarray data obtained from three samples treated with alcohol (control group), three samples treated with 3 μmol/l genistein and three samples treated with 10 μmol/l genistein for 48 h, were downloaded from the Gene Expression Omnibus database. Analysis of the differentially expressed genes (DEGs) and functional enrichment in the two genistein groups was performed. The interaction networks of the DEGs were constructed and the overlapping network was extracted. Finally, the functions and pathways of the DEGs in the overlapping network were enriched. In total, 224 DEGs coexisted in the two genistein groups, and the most significant function of these was the cell cycle. The number and the fold change of expression values of the DEGs in the 10 μmol/l genistein group were significantly higher compared with that of the 3 μmol/l genistein group. The most significant function and pathway of the DEGs in the overlapping network was the cell cycle involving several genes, including GLIPR1, CDC20, BUB1, MCM2 and CCNB1. Thus, genistein stimulation resulted in gene expression changes in breast cancer cell lines and discrepancies increased with higher doses of genistein. The DEGs were most significantly associated with cell cycle regulation.

MCM Paradox: Abundance of Eukaryotic Replicative Helicases and Genomic Integrity

As a crucial component of DNA replication licensing system, minichromosome maintenance (MCM) 2–7 complex acts as the eukaryotic DNA replicative helicase. The six related MCM proteins form a heterohexamer and bind with ORC, CDC6, and Cdt1 to form the prereplication complex. Although the MCMs are well known as replicative helicases, their overabundance and distribution patterns on chromatin present a paradox called the “MCM paradox.” Several approaches had been taken to solve the MCM paradox and describe the purpose of excess MCMs distributed beyond the replication origins. Alternative functions of these MCMs rather than a helicase had also been proposed. This review focuses on several models and concepts generated to solve the MCM paradox coinciding with their helicase function and provides insight into the concept that excess MCMs are meant for licensing dormant origins as a backup during replication stress. Finally, we extend our view towards the effect of alteration of MCM level. Though an excess MCM constituent is needed for normal cells to withstand stress, there must be a delineation of the threshold level in normal and malignant cells. This review also outlooks the future prospects to better understand the MCM biology.

Endocrine Resistance in Breast Cancer

Around 70% of all breast cancers are estrogen receptor alpha positive and hence their development is highly dependent on estradiol. While the invention of endocrine therapies has revolusioned the treatment of the disease, resistance to therapy eventually occurs in a large number of patients. This paper seeks to illustrate and discuss the complexity and heterogeneity of the mechanisms which underlie resistance and the approaches proposed to combat them. It will also focus on the use and development of methods for predicting which patients are likely to develop resistance.

Minichromosome Maintenance (MCM) Family as potential diagnostic and prognostic tumor markers for human gliomas

Background

Gliomas are the most common type of all central nervous system tumors. Almost all patients diagnosed with these tumors have a poor prognostic outcome. We aimed to identify novel glioma prognosis-associated candidate genes.

Methods

We applied WebArrayDB software to span platform integrate and analyze the microarray datasets. We focused on a subset of the significantly up-regulated genes, the minichromosome maintenance (MCM) family. We used frozen glioma samples to predict the relationship between the expression of MCMs and patients outcome by qPCR and western blot.

Results

We found that MCMs expression was significantly up-regulated in glioma samples. MCM2-7 and MCM10 expressions were associated with WHO tumor grade. High MCM2 mRNA expression appeared to be strongly associated with poor overall survival in patients with high grade glioma. Furthermore, we report that MCM7 is strongly correlated with patient outcome in patients with WHO grade II-IV tumor. MCM3 expression was found to be up-regulated in glioma and correlated with overall survival in patients with WHO grade III tumor. MCM2, MCM3 and MCM7 expression levels were of greater prognostic relevance than histological diagnosis according to the current WHO classification system.

Conclusions

High expression of MCM 2, MCM3 and MCM7 mRNA correlated with poor outcome and may be clinically useful molecular prognostic markers in glioma.

Virus transcript levels and cell growth rates after naturally occurring HPV16 integration events in basal cervical keratinocytes

Cervical carcinogenesis is characterized by a clonal selection process in which the high-risk human papillomavirus (HRHPV) genome usually changes from the extra-chromosomal (episomal) state seen in productive infections to DNA that is integrated into host chromosomes. However, it is not clear whether all HRHPV integration events provide cells with a selective growth advantage compared with the episome-containing cells from which they originate. It is also unclear whether selection of cells containing a particular integrant from a mixed population simply reflects the highest levels of virus oncogene expression or has additional determinants. These early events in cervical carcinogenesis cannot readily be addressed by cross-sectional studies of clinical samples. We used the W12 model system to generate a panel of cervical squamous cell clones that were derived from an identical background under non-competitive conditions and differed only by the genomic site of HPV16 integration. Compared with the ‘baseline’ episome-containing cells from which they were isolated, only 9/17 clones (53%) showed significantly greater growth rates and only 7/17 (41%) showed significantly greater expression of the major virus oncogenes E7/E6. There were significant variations in levels of HPV16 transcription per DNA template, changes that were associated with histone modifications in the integrated virus chromatin. Cell growth rates showed only weak and non-significant associations with protein and mRNA levels for E7, E6, and the mean E7/E6 values. We conclude that HPV16 integration in basal cervical cells does not necessarily lead to increased levels of virus oncogenes, or to a competitive growth advantage, when compared with the initiating episome-containing cells.

MCM3 as a novel diagnostic marker in benign and malignant salivary gland tumors

BACKGROUND

Proliferation markers widely have been used to diagnose and determine the behaviour and prognosis of benign and malignant tumours. Minichromosome maintenance 3 (MCM3) is a novel proliferation marker. The aim of this study was to evaluate and compare MCM3 with Ki-67 in diagnosis of salivary gland tumours.

MATERIALS AND METHODS

In this retrospective study, immunohistochemical expression of MCM3 and Ki-67 was evaluated in 15 pleomorphic adenomas (PA), 17 mucoepidermoid carcinomas (MEC) and 18 adenoid cystic carcinomas (ADCC) . Labeling indices (LIs) for the two markers were calculated and compared.

RESULTS

MCM3 and Ki-67 LIs were significantly higher in MEC and ADCC compared to PA. The LI of MCM3 was significantly higher than that of Ki-67 in MEC and PA. There was no significant difference between the two markers in ADCC. A cut-off point of 8% with 74.3% sensitivity and 93.3% specificity for MCM3 was obtained to discern between benign and malignant tumors.

CONCLUSIONS

These results suggest that MCM3 might be a useful proliferation marker for differential diagnosis and recognition of clinical behavior of salivary gland tumors.

Replication proteins and human disease

In this article, we discuss the significance of DNA replication proteins in human disease. There is a broad range of mutations in genes encoding replication proteins, which result in several distinct clinical disorders that share common themes. One group of replication proteins, the MCMs, has emerged as effective biomarkers for early detection of a range of common cancers. They offer practical and theoretical advantages over other replication proteins and have been developed for widespread clinical use.

Urea transporter UT-B deletion induces DNA damage and apoptosis in mouse bladder urothelium

BACKGROUND

Previous studies found that urea transporter UT-B is abundantly expressed in bladder urothelium. However, the dynamic role of UT-B in bladder urothelial cells remains unclear. The objective of this study is to evaluate the physiological roles of UT-B in bladder urothelium using UT-B knockout mouse model and T24 cell line.

METHODOLOGY/PRINCIPAL FINDINGS

Urea and NO measurement, mRNA expression micro-array analysis, light and transmission electron microscopy, apoptosis assays, DNA damage and repair determination, and intracellular signaling examination were performed in UT-B null bladders vs wild-type bladders and in vitro T24 epithelial cells. UT-B was highly expressed in mouse bladder urothelium. The genes, Dcaf11, MCM2-4, Uch-L1, Bnip3 and 45 S pre rRNA, related to DNA damage and apoptosis were significantly regulated in UT-B null urothelium. DNA damage and apoptosis highly occurred in UT-B null urothelium. Urea and NO levels were significantly higher in UT-B null urothelium than that in wild-type, which may affect L-arginine metabolism and the intracellular signals related to DNA damage and apoptosis. These findings were consistent with the in vitro study in T24 cells that, after urea loading, exhibited cell cycle delay and apoptosis.

CONCLUSIONS/SIGNIFICANCE

UT-B may play an important role in protecting bladder urothelium by balancing intracellular urea concentration. Disruption of UT-B function induces DNA damage and apoptosis in bladder, which can result in bladder disorders.

Bisphenol-A-induced inactivation of the p53 axis underlying deregulation of proliferation kinetics, and cell death in non-malignant human breast epithelial cells

Widespread distribution of bisphenol-A (BPA) complicates epidemiological studies of possible carcinogenic effects on the breast because there are few unexposed controls. To address this challenge, we previously developed non-cancerous human high-risk donor breast epithelial cell (HRBEC) cultures, wherein BPA exposure could be controlled experimentally. BPA consistently induced activation of the mammalian target of rapamycin (mTOR) pathway—accompanied by dose-dependent evasion of apoptosis and increased proliferation—in HRBECs from multiple donors. Here, we demonstrate key molecular changes underlying BPA-induced cellular reprogramming. In 3/3 BPA-exposed HRBEC cell lines, and in T47D breast cancer cells, proapoptotic negative regulators of the cell cycle (p53, p21^WAF1 and BAX) were markedly reduced, with concomitant increases in proliferation-initiating gene products (proliferating cell nuclear antigen, cyclins, CDKs and phosphorylated pRb). However, simultaneous exposure to BPA and the polyphenol, curcumin, partially or fully reduced the spectrum of effects associated with BPA alone, including mTOR pathway proteins (AKT1, RPS6, pRPS6 and 4EBP1). BPA exposure induced an increase in the ERα (Estrogen Receptor): ERβ ratio—an effect also reversed by curcumin (analysis of variance, P < 0.02 for all test proteins). At the functional level, concurrent curcumin exposure reduced BPA-induced apoptosis evasion and rapid growth kinetics in all cell lines to varying degrees. Moreover, BPA extended the proliferation potential of 6/6 primary finite-life HRBEC cultures—another effect reduced by curcumin. Even after removal of BPA, 1/6 samples maintained continuous growth—a hallmark of cancer. We show that BPA exposure induces aberrant expression of multiple checkpoints that regulate cell survival, proliferation and apoptosis and that such changes can be effectively ameliorated.

Aurora kinase A outperforms Ki67 as a prognostic marker in ER-positive breast cancer

Background:

Proliferation has emerged as a major prognostic factor in luminal breast cancer. The immunohistochemical (IHC) proliferation marker Ki67 has been most extensively investigated but has not gained widespread clinical acceptance.

Methods:

We have conducted a head-to-head comparison of a panel of proliferation markers, including Ki67. Our aim was to establish the marker of the greatest prognostic utility. Tumour samples from 3093 women with breast cancer were constructed as tissue microarrays. We used IHC to detect expression of mini-chromosome maintenance protein 2, Ki67, aurora kinase A (AURKA), polo-like kinase 1, geminin and phospho-histone H3. We used a Cox proportional-hazards model to investigate the association with 10-year breast cancer-specific survival (BCSS). Missing values were resolved using multiple imputation.

Results:

The prognostic significance of proliferation was limited to oestrogen receptor (ER)-positive breast cancer. Aurora kinase A emerged as the marker of the greatest prognostic significance in a multivariate model adjusted for the standard clinical and molecular covariates (hazard ratio 1.3; 95% confidence interval 1.1–1.5; P=0.005), outperforming all other markers including Ki67.

Conclusion:

Aurora kinase A outperforms other proliferation markers as an independent predictor of BCSS in ER-positive breast cancer. It has the potential for use in routine clinical practice.

Expression of minichromosome maintenance MCM6 protein in meningiomas is strongly correlated with histologic grade and clinical outcome

The 2007 World Health Organization histologic grading of meningiomas is associated with recurrence and clinical outcome. However, distinction of grade I from grade II (atypical) meningiomas can be challenging. In the World Health Organization classification, there are 4 parameters on the basis of which grade II status can be determined: mitotic rate, cytoarchitectural features, brain invasion, and/or histologic subtype. Furthermore, this classification fails to detect grade I recurrent meningiomas, for which other prognostic criteria would be needed. The aim of this study was to evaluate the respective value of several markers involved in cell cycle as effective tools to predict recurrence. This retrospective study was based on a series of 59 meningiomas (grade I: 32 of 59, grade II: 27 of 59, all harboring ≥4 mitoses/1.6 mm), analyzed with the following immunohistochemical markers: MCM6, Ki-67, PHH3, cyclin D1, and p53. We found a significant correlation between histologic grade and mean labeling index for MCM6 (grade I: 21.8% vs. grade II: 65.8%; P<0.001), Ki-67 (3.2% vs. 16.9%; P<0.001), PHH3 (0.7‰ vs. 2.8‰; P<0.001), cyclin D1 (50.4% vs. 70.0%; P=0.005), and p53 (17.3% vs. 32.4%; P=0.017). Histologic grading and mitotic index were correlated with progression-free survival (P=0.010 and P=0.020, respectively). A nearly linear correlation was found between progression-free survival and staining for MCM6 (P<0.001), Ki-67 (P=0.003), and PHH3 (P=0.037) but not for cyclin D1 (P=0.400) and p53 (P=0.758). The interobserver agreement coefficients for MCM6, Ki-67, PHH3, cyclin D1, and p53 were, respectively, 0.97 (95% confidence interval, 0.95-0.98), 0.93 (0.89-0.96), 0.81 (0.70-0.88), 0.90 (0.83-0.94), and 0.84 (0.73-0.90). In conclusion, because of its strong level of expression and sharp difference in labeling index between indolent and recurrent tumors, MCM6 is the most efficient marker to identify tumors with a high risk of recurrence.

Initiation of DNA Replication in the Human Genome

Replication of the human genome relies on the presence of thousands of origins distributed along each of the chromosomes. The activation of these origins occurs in a highly regulated manner to ensure that chromosomes are faithfully duplicated only once during each cell cycle. Failure in this regulation can lead to abnormal cell proliferation, or/and genomic instability, the hallmarks of cancer cells. The mechanisms determining how, when, and where origins are activated remains still a mystery. However recent technological advances have facilitated the study of DNA replication in a genome-wide scale, and have provided a wealth of information on several features of this process. Here we present an overview of the current progress on our understanding of the initiation step of DNA replication in human cells, and its relationship to abnormal cell proliferation.