Clinical significance of MCM-2 and MCM-5 expression in colon cancer: association with clinicopathological parameters and tumor proliferative capacity

Expression and promoter methylation status of hMLH1, MGMT, APC, and CDH1 genes in patients with colon adenocarcinoma

Colorectal cancer (CRC) is the third most common cancer in men and the second in women worldwide. CRC development is the result of genetic and epigenetic alterations accumulation in the epithelial cells of colon mucosa. In the present study, DNA methylation, an epigenetic event, was evaluated in tumoral and matching normal epithelium in a cohort of 61 CRC patients. The results confirmed and expanded knowledge for the tumor suppressor genes hMLH1, MGMT, APC, and CDH1. Promoter methylation was observed for all the examined genes in different percentage. A total of 71% and 10% of the examined cases were found to be methylated in two or more and in all genes, respectively. mRNA and protein levels were also evaluated. Promoter methylation of hMLH1, MGMT, APC, and CDH1 genes was present at the early stages of tumor's formation and it could also be detected in the normal mucosa. Correlations of the methylated genes with patient's age and tumor's clinicopathological characteristics were also observed. Our findings suggest that DNA methylation is a useful marker for tumor progression monitoring and that promoter methylation in certain genes is associated with more advanced tumor stage, poor differentiation, and metastasis.

Molecular mechanism of anticancer effect of Sclerotium rolfsii lectin in HT29 cells involves differential expression of genes associated with multiple signaling pathways: A microarray analysis

Sclerotium rolfsii lectin (SRL) is a lectin isolated from fungus S. rolfsii and has high binding specificity toward the oncofetal Thomsen-Friedenreich carbohydrate antigen (Galβ1-3GalNAc-α-O-Ser/Thr, T or TF), which is expressed in more than 90% of human cancers. Our previous studies have shown that binding of SRL to human colon, breast and ovarian cancer cells induces cell apoptosis in vitro and suppresses tumor growth in vivo. This study investigated the SRL-mediated cell signaling in human colon cancer HT29 cells by mRNA and miRNA microarrays. It was found that SRL treatment results in altered expression of several hundred molecules including mitogen-activated protein kinase (MAPK) and c-JUN-associated, apoptosis-associated and cell cycle and DNA replication-associated signaling molecules. Pathway analysis using GeneSpring 12.6.1 revealed that SRL treatment induces changes of MAPK and c-JUN-associated signaling pathways as early as 2 h while changes of cell cycle, DNA replication and apoptosis pathways were significantly affected only after 24 h. A significant change of cell miRNA expression was also observed after 12 h treatment of the cells with SRL. These changes were further validated by quantitative real time polymerase chain reaction and immunoblotting. This study thus suggests that the presence of SRL affects multiple signaling pathways in cancer cells with early effects on cell proliferation pathways associated with MAPK and c-JUN, followed by miRNA-associated cell activity and apoptosis. This provides insight information into the molecular mechanism of the anticancer activity of this fungal lectin.

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.

De Novo proteome analysis of genetically modified tumor cells by a metabolic labeling/azide-alkyne cycloaddition approach

Activin receptor type II (ACVR2) is a member of the transforming growth factor type II receptor family and controls cell growth and differentiation, thereby acting as a tumor suppressor. ACVR2 inactivation is known to drive colorectal tumorigenesis. We used an ACVR2-deficient microsatellite unstable colon cancer cell line (HCT116) to set up a novel experimental design for comprehensive analysis of proteomic changes associated with such functional loss of a tumor suppressor. To this end we combined two existing technologies. First, the ACVR2 gene was reconstituted in an ACVR2-deficient colorectal cancer (CRC) cell line by means of recombinase-mediated cassette exchange, resulting in the generation of an inducible expression system that allowed the regulation of ACVR2 gene expression in a doxycycline-dependent manner. Functional expression in the induced cells was explicitly proven. Second, we used the methionine analog azidohomoalanine for metabolic labeling of newly synthesized proteins in our cell line model. Labeled proteins were tagged with biotin via a Click-iT chemistry approach enabling specific extraction of labeled proteins by streptavidin-coated beads. Tryptic on-bead digestion of captured proteins and subsequent ultra-high-performance LC coupled to LTQ Orbitrap XL mass spectrometry identified 513 proteins, with 25 of them differentially expressed between ACVR2-deficient and -proficient cells. Among these, several candidates that had already been linked to colorectal cancer or were known to play a key role in cell growth or apoptosis control were identified, proving the utility of the presented experimental approach. In principle, this strategy can be adapted to analyze any gene of interest and its effect on the cellular de novo proteome.

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.

Multifunctional imaging signature for V-KI-RAS2 Kirsten rat sarcoma viral oncogene homolog (KRAS) mutations in colorectal cancer

This study explores the potential for multifunctional imaging to provide a signature for V-KI-RAS2 Kirsten rat sarcoma viral oncogene homolog (KRAS) gene mutations in colorectal cancer.

METHODS

This prospective study approved by the institutional review board comprised 33 patients undergoing PET/CT before surgery for proven primary colorectal cancer. Tumor tissue was examined histologically for presence of the KRAS mutations and for expression of hypoxia-inducible factor-1 (HIF-1) and minichromosome maintenance protein 2 (mcm2). The following imaging parameters were derived for each tumor: (18)F-FDG uptake ((18)F-FDG maximum standardized uptake value [SUVmax]), CT texture (expressed as mean of positive pixels [MPP]), and blood flow measured by dynamic contrast-enhanced CT. A recursive decision tree was developed in which the imaging investigations were applied sequentially to identify tumors with KRAS mutations. Monte Carlo analysis provided mean values and 95% confidence intervals for sensitivity, specificity, and accuracy.

RESULTS

The final decision tree comprised 4 decision nodes and 5 terminal nodes, 2 of which identified KRAS mutants. The true-positive rate, false-positive rate, and accuracy (95% confidence intervals) of the decision tree were 82.4% (63.9%-93.9%), 0% (0%-10.4%), and 90.1% (79.2%-96.0%), respectively. KRAS mutants with high (18)F-FDG SUVmax and low MPP showed greater frequency of HIF-1 expression (P = 0.032). KRAS mutants with low (18)F-FDG SUV(max), high MPP, and high blood flow expressed mcm2 (P = 0.036).

CONCLUSION

Multifunctional imaging with PET/CT and recursive decision-tree analysis to combine measurements of tumor (18)F-FDG uptake, CT texture, and perfusion has the potential to identify imaging signatures for colorectal cancers with KRAS mutations exhibiting hypoxic or proliferative phenotypes.

Suppression of ERβ signaling via ERβ knockout or antagonist protects against bladder cancer development

Epidemiological studies showed that women have a lower bladder cancer (BCa) incidence, yet higher muscle-invasive rates than men, suggesting that estrogen and the estrogen receptors, estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ), may play critical roles in BCa progression. Using in vitro cell lines and an in vivo carcinogen N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN)-induced mouse BCa model, we found that ERβ plays a positive role in promoting BCa progression. Knockdown of ERβ with ERβ-shRNA in ERβ-positive human BCa J82, 647v and T24 cell lines led to suppressed cell growth and invasion. Mice lacking ERβ have less cancer incidence with reduced expression of the proliferation marker Ki67 in BBN-induced BCa. Consistently, our results show that non-malignant urothelial cells with ERβ knockdown are more resistant to carcinogen-induced malignant transformation. Mechanism dissection found that targeting ERβ suppressed the expression of minichromosome maintenance complex component 5 (MCM5), a DNA replication licensing factor that is involved in tumor cell growth. Restoring MCM5 expression can partially reverse ERβ knockdown-mediated growth reduction. Supportively, treating cells with the ERβ-specific antagonist, 4-[2-Phenyl-5,7-bis(trifluoromethyl) pyrazolo[1,5-a]pyrimidin-3-yl]phenol (PHTPP), reduced BCa cell growth and invasion, as well as MCM5 expression. Furthermore, we provide the first evidence that BCa burden and mortality can be controlled by PHTPP treatment in the carcinogen-induced BCa model. Together, these results demonstrate that ERβ could play positive roles in promoting BCa progression via MCM5 regulation. Targeting ERβ through ERβ-shRNA, PHTPP or via downstream targets, such as MCM5, could serve as potential therapeutic approaches to battle BCa.

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.

Joint network and node selection for pathway-based genomic data analysis

Motivation: By capturing various biochemical interactions, biological pathways provide insight into underlying biological processes. Given high-dimensional microarray or RNA-sequencing data, a critical challenge is how to integrate them with rich information from pathway databases to jointly select relevant pathways and genes for phenotype prediction or disease prognosis. Addressing this challenge can help us deepen biological understanding of phenotypes and diseases from a systems perspective.

Results: In this article, we propose a novel sparse Bayesian model for joint network and node selection. This model integrates information from networks (e.g. pathways) and nodes (e.g. genes) by a hybrid of conditional and generative components. For the conditional component, we propose a sparse prior based on graph Laplacian matrices, each of which encodes detailed correlation structures between network nodes. For the generative component, we use a spike and slab prior over network nodes. The integration of these two components, coupled with efficient variational inference, enables the selection of networks as well as correlated network nodes in the selected networks.

Simulation results demonstrate improved predictive performance and selection accuracy of our method over alternative methods. Based on three expression datasets for cancer study and the KEGG pathway database, we selected relevant genes and pathways, many of which are supported by biological literature. In addition to pathway analysis, our method is expected to have a wide range of applications in selecting relevant groups of correlated high-dimensional biomarkers.

Availability: The code can be downloaded at www.cs.purdue.edu/homes/szhe/software.html.

Contact:alanqi@purdue.edu

Increased copy-number and not DNA hypomethylation causes overexpression of the candidate proto-oncogene CYP24A1 in colorectal cancer

In colorectal cancer (CRC) the vitamin D catabolizing enzyme 1,25-dihydroxyvitamin D 24-hydroxylase (CYP24A1) is overexpressed with a potentially significant, positive impact on the catabolism of 1,25-dihydroxyvitamin D₃ (1,25-D₃). However, the underlying mechanism of CYP24A1 overexpression is poorly understood. In the present study, we investigated possible causes including hypomethylation of the CYP24A1 promoter, amplification of the CYP24A1 gene locus (20q13.2), and altered expression of CYP24A1-specific transcription factors. We quantified CYP24A1 gene copy-number, performed bisulfite sequencing of the CYP24A1 promoter to assess DNA methylation, and measured mRNA expression of CYP24A1, 25-hydroxyvitamin D 1α-hydroxylase (CYP27B1), vitamin D receptor (VDR) and retinoid X receptor (RXR). We found that 77 (60%) out of 127 colorectal tumors showed increased CYP24A1 gene copy-number and that more than 6 copies of CYP24A1 correlated positively with CYP24A1 mRNA expression suggestive of a causal relationship. No differences in CYP24A1 promoter methylation were found between tumor tissue and adjacent mucosa from the same patient or between tissues with high or low mRNA expression, thus excluding DNA hypomethylation as a possible cause of CYP24A1 overexpression in CRC. Furthermore, mRNA expression of several factors involved in replication licensing positively correlated with CYP24A1 mRNA expression, raising the possibility that CYP24A1 overexpression might favor increased proliferation in tumors by suppressing local 1,25-D₃ levels. We conclude that high copy-number gain is a key determinant of CYP24A1 overexpression in CRC. Other postulated causes of CYP24A1 overexpression including promoter hypomethylation and enhanced VDR and/or RXR expression do not appear to be involved.

What’s new?

Recently, it has been suggested that the association between colorectal cancer and reduced levels of circulating vitamin D may be related to overexpression of the vitamin D-catabolizing enzyme, CYP24A1 in the tumor. In this search for a mechanistic explanation, increased CYP24A1 gene copy number was associated with the enzyme’s overexpression in 60 percent of colorectal tumors, and expression was correlated strongly with proliferation markers. The findings suggest that CYP24A1 overexpression is likely to deplete tumor calcitriol (1,25-dihydroxyvitamin D₃) levels, possibly increasing the proliferative potential of the tumors.

Loss of E-cadherin independently predicts the lymph node status in colorectal cancer

BACKGROUND

The identification of biomarkers that improve risk stratification in patients with colorectal cancer (CRC) is still a challenge. The objective of our study was to identify independent protein markers as predictors of lymph node (N) stage in CRC.

METHODS

Tumour specimens from 221 CRC patients were mounted onto a multiple-punch tissue microarray and evaluated for 21 tumour related factors and one host related factor involved in CRC carcinogenesis, namely β-catenin, E-cadherin, EGFR, pERK, RHAMM, pAKT, pSMAD2, p21, p16, Bcl-2, Ki-67, APAF-1, MST1, RKIP, VEGF, EphB2, MMP7, Laminin5γ2, MUC1, CDX2, caspase-3 as well as intra-tumoural and stromal CD8+ tumour infiltrating lymphocytes (iTILs and sTILs).

RESULTS

Node positive cancers showed significant losses for p21 (p = 0.026), Bcl-2 (p = 0.027), APAF-1 (p = 0.033), EphB2 (p = 0.006), E-cadherin (p < 0.001), RKIP (p = 0.019), CD8+ iTILs and sTILs (p < 0.001 and p = 0.008, respectively) and cytoplasmic MST1 (p = 0.014). Based on the area under the receiver operating characteristic curve (AUC) EphB2, E-cadherin, iTILs and sTILs were identified as potential predictors of N stage (AUC values >0.6), but only loss of E-cadherin was an independent predictor in multivariate analysis.

CONCLUSIONS

E-cadherin appears to be a strong predictor of N stage in CRC and should be considered in pre-operative and post-operative management of colon and rectal cancer patients.

Integrative functional genomics analysis of sustained polyploidy phenotypes in breast cancer cells identifies an oncogenic profile for GINS2

Aneuploidy is among the most obvious differences between normal and cancer cells. However, mechanisms contributing to development and maintenance of aneuploid cell growth are diverse and incompletely understood. Functional genomics analyses have shown that aneuploidy in cancer cells is correlated with diffuse gene expression signatures and aneuploidy can arise by a variety of mechanisms, including cytokinesis failures, DNA endoreplication, and possibly through polyploid intermediate states. To identify molecular processes contributing to development of aneuploidy, we used a cell spot microarray technique to identify genes inducing polyploidy and/or allowing maintenance of polyploid cell growth in breast cancer cells. Of 5760 human genes screened, 177 were found to induce severe DNA content alterations on prolonged transient silencing. Association with response to DNA damage stimulus and DNA repair was found to be the most enriched cellular processes among the candidate genes. Functional validation analysis of these genes highlighted GINS2 as the highest ranking candidate inducing polyploidy, accumulation of endogenous DNA damage, and impairing cell proliferation on inhibition. The cell growth inhibition and induction of polyploidy by suppression of GINS2 was verified in a panel of breast cancer cell lines. Bioinformatic analysis of published gene expression and DNA copy number studies of clinical breast tumors suggested GINS2 to be associated with the aggressive characteristics of a subgroup of breast cancers in vivo. In addition, nuclear GINS2 protein levels distinguished actively proliferating cancer cells suggesting potential use of GINS2 staining as a biomarker of cell proliferation as well as a potential therapeutic target.

MCM-2 and MCM-5 expression in gastric adenocarcinoma: clinical significance and comparison with Ki-67 proliferative marker

BACKGROUND

Minichromosome maintenance (MCM) proteins are essential components of DNA replication, being related to cell proliferation, and serve as useful biomarkers for cancer screening, surveillance and prognosis. The aim of the present study was to evaluate the clinical significance of MCM-2 and MCM-5 expression in gastric adenocarcinoma in comparison with Ki-67 proliferative marker.

METHODS

MCM-2, MCM-5 and Ki-67 expression was assessed immunohistochemically in 66 tumoral samples of gastric adenocarcinoma patients and was statistically analyzed in relation to clinicopathological characteristics and patient survival.

RESULTS

MCM-2 expression did not show significant associations with any clinicopathological parameters, while Ki-67 expression was merely significantly associated with tumor size (P = 0.0150). MCM-2 and Ki-67 expression were more frequently in intestinal (median values: 67.5 and 60%) compared to diffuse-type (median values: 60 and 45%) gastric adenocarcinoma cases without though reaching statistical significance (P > 0.05). MCM-5 expression was significantly associated with tumor size (P = 0.0295), presence of lymph node metastases (P = 0.0216) and tumor histopathological stage (P = 0.0098). Patients presenting high MCM-5 expression had significantly shorter survival times (log-rank test, P = 0.0042), whereas neither MCM-2 nor Ki-67 expression showed significant prognostic value (log-rank test, P = 0.9618 and P = 0.7174, respectively). In multivariate analysis, patient age, histopathological stage and grade of differentiation, but not MCM-5 expression, were identified as independent prognostic factors (Cox regression analysis, P = 0.0097, P = 0.0195, P = 0.0035 and P = 0.3245, respectively).

CONCLUSIONS

The present study showed that MCM-5 expression was associated with clinicopathological parameters in gastric adenocarcinoma. However, further studies highlighting the distinct impact of the two histopathological types, intestinal and diffuse, are warranted to delineate whether MCMs could be used as diagnostic and prognostic markers in gastric neoplasia.

Expression of p16 in lymph node metastases of adjuvantly treated stage III colorectal cancer patients identifies poor prognostic subgroups: a retrospective analysis of biomarkers in matched primary tumor and lymph node metastases

BACKGROUND

The objective of identifying protein biomarkers for patients with stage III and IV colorectal cancer is to improve risk stratification and, thus, to identify patients in the postoperative setting who may benefit from more targeted treatment. The objective of the current study was to determine the prognostic value of 19 protein markers assessed in primary tumors and matched lymph node (LN) metastases from patients with stage III and IV colorectal cancer.

METHODS

Matched primary tumors and LN metastases from 82 patients with stage III and IV colorectal cancer were mounted onto a multiple-punch tissue microarray and were stained for 19 protein markers involved in tumor progression (β-catenin, E-cadherin, epidermal growth factor receptor, phosphorylated extracellular signal-regulated kinase [pERK], receptor for hyaluronic acid-mediated motility, phosphorylated protein kinase B, p21, p16, B-cell lymphoma 2, Ki67, apoptotic protease activating factor 1, mammalian sterile 20-like kinase 1, Raf kinase inhibitor protein, vascular endothelial growth factor, ephrin type-B receptor 2, matrix metalloproteinase 7, laminin5γ2, mucin 1 [MUC1], and caudal-related homeobox 2). The prognostic effects of biomarkers in both primary tumor and positive LNs were assessed.

RESULTS

MUC1, pERK and p16 in LN (P=.002, P=.014, and P=.002, respectively) had independent prognostic value. In patients with stage III disease who received adjuvant treatment, negative p16 expression was associated with highly unfavorable outcomes overall (hazard ratio [HR], 0.26; 95% confidence interval [CI], 0.1-0.6; P=.005) when the analysis was stratified by pathologic tumor classification (HR, 0.25; 95% CI, 0.1-0.7; P=.005), age (HR, 0.23; 95% CI, 0.1-0.6; P=.004), and LN ratio (HR, 0.26; 95% CI, 0.1-0.7; P=.007); and, in multivariate analysis, it was associated with performance status and the receipt of folic acid treatment (HR, 0.29; 95% CI, 0.09-0.89; P=.03).

CONCLUSIONS

The loss of p16 in LN metastases contributed to adverse outcomes in adjuvantly treated patients with stage III colorectal cancer independent of pathologic tumor classification, age, LN ratio, performance status, or folic acid treatment. The current results support the investigation of p16 as a prognostic and potential predictive biomarker for future randomized trials of patients with stage III colorectal cancer.

Study of histopathological, morphological and immunohistochemical features of recurrent pleomorphic adenoma: an attempt to predict recurrence of pleomorphic adenoma

BACKGROUND

Recurrent pleomorphic adenoma (RPA) is an uncommon and challenging disease. The aim of this study was to review the clinical information obtained by examining RPA patients, to determine its histomorphological features and to verify the expression of the Mcm-2 markers of cell proliferation and the expression of p-53 in pleomorphic adenoma (PA), RPA, and RPA with malignant transformation (TRPA).

METHODS

A total of 10 cases of PA and 29 cases of RPA were examined in detail for the presence of nodules and their histomorphological features. Cell proliferation and expression of p-53 were detected by the immunohistochemical technique using the antibodies against Mcm-2 and p-53.

RESULTS

Histopathologically, RPA is very similar to PA; the only difference found was that all the cases of RPA were multinodular. When comparing primary and recurrent tumor, no significant difference was found in terms of cell proliferation and the expression of p-53; however, in the RPA with areas of malignant transformation there was an increased expression of these proteins.

CONCLUSION

This study showed that recurrences were multinodular, with nodules varying in numbers and sizes. No significant difference in histological features was found between RPA and PA. Moreover, the immunohistochemical study showed a low expression of p-53 and Mcm-2 in PA and RPA and an increased expression of these proteins in the RPA with areas of malignant transformation.

Comparative protein profiling reveals minichromosome maintenance (MCM) proteins as novel potential tumor markers for meningiomas

Meningiomas are among the most frequent tumors of the brain and spinal cord accounting for 15-20% of all central nervous system tumors and frequently associated with neurofibromatosis type 2. In this study, we aimed to unravel molecular meningioma tumorigenesis and discover novel protein biomarkers for diagnostic and/or prognostic purposes and performed in-depth proteomic profiling of meningioma cells compared to human primary arachnoidal cells. We isolated proteins from meningioma cell line SF4433 and human primary arachnoidal cells and analyzed the protein profiles by Gel-nanoLC-MS/MS in conjunction with protein identification and quantification by shotgun nanoLC tandem mass spectrometry and spectral counting. Differential analysis of meningiomas revealed changes in the expression levels of 281 proteins (P < 0.01) associated with various biological functions such as DNA replication, recombination, cell cycle, and apoptosis. Among several interesting proteins, we focused on a subset of the highly significantly up-regulated proteins, the minichromosome maintenance (MCM) family. We performed subsequent validation studies by qRT-PCR in human meningioma tissue samples (WHO grade I, 14 samples; WHO grade II, 7 samples; and WHO grade III, 7 samples) compared to arachnoidal tissue controls (from fresh autopsies; 3 samples) and found that MCMs are highly and significantly up-regulated in human meningioma tumor samples compared to arachnoidal tissue controls. We found a significant increase in MCM2 (8 fold), MCM3 (5 fold), MCM4 (4 fold), MCM5 (4 fold), MCM6 (3 fold), and MCM7 (5 fold) expressions in meningiomas. This study suggests that MCM family proteins are up-regulated in meningiomas and can be used as diagnostic markers.

Determination of cell proliferation using Mcm2 antigen and evaluation of apoptosis and TGF-beta1 expression in GH-secreting or clinically nonfunctioning pituitary adenomas

Pituitary adenomas (PA) occasionally show aggressive behavior, with invasion of the surrounding tissues. The identification of markers able to recognize aggressive PA in early stages remains a challenge. We aimed to determine the expression of a new cell proliferation marker, Mcm2, and the presence of apoptosis in PA, and to evaluate the association of clinicopathological features with the apoptotic and proliferative indices. Additionally, the TGF-beta1 expression, an inducer of apoptosis, was determined. The proliferative index was determined in GH-secreting or clinically nonfunctioning PA using immunohistochemical (IH) methods for Mcm2 and Ki-67 antigens. The apoptosis was assessed by the TUNEL method and the TGF-beta1 expression by IH. A significant positive correlation was found between log Mcm2 index and log Ki-67 index (p < 0.001). Mcm2 and Ki-67 detected a similar number of proliferating cells. Mcm2 index showed a significant association with tumor extension (p = 0.02), but not with tumor invasion. Apoptosis was detected in 17% of the adenomas, with a maximum apoptotic index of 0.77%. Immunoreactivity to TGF-beta1 was observed in 77% of the adenomas, showing an association with tumor extension. We concluded that, in this sample, Mcm2 was similar to Ki-67 in the identification of the proliferating cells and that apoptosis was rare.

PSF3 marks malignant colon cancer and has a role in cancer cell proliferation

PSF3 (partner of Sld five 3) is a member of the tetrameric complex termed GINS, composed of SLD5, PSF1, PSF2, and PSF3, and well-conserved evolutionarily. Previous studies suggested that some GINS complex members are upregulated in cancer, but PSF3 expression in colon carcinoma has not been investigated. Here, we established a mouse anti-PSF3 antibody, and examined PSF3 expression in human colon carcinoma cell lines and colon carcinoma specimens. We found that PSF3 is expressed in the crypt region in normal colonic mucosa and that many PSF3-positive cells co-expressed Ki-67. This suggests that PSF3-positivity of normal mucosa is associated with cell proliferation. Expression of the PSF3 protein was greater in carcinoma compared with the adjacent normal mucosa, and even stronger in high-grade malignancies, suggesting that it may be associated with colon cancer progression. PSF3 gene knock-down in human colon carcinoma cell lines resulted in growth inhibition characterized by delayed S-phase progression. These results suggest that PSF3 is a potential biomarker for diagnosis of progression in colon cancer and could be a new target for cancer therapy.