Absence of cyclin D2 expression is associated with promoter hypermethylation in gastric cancer

D-Type Cyclins in Development and Disease

D-type cyclins encode G1/S cell cycle checkpoint proteins, which play a crucial role in defining cell cycle exit and progression. Precise control of cell cycle exit is vital during embryonic development, with defects in the pathways regulating intracellular D-type cyclins resulting in abnormal initiation of stem cell differentiation in a variety of different organ systems. Furthermore, stabilisation of D-type cyclins is observed in a wide range of disorders characterized by cellular over-proliferation, including cancers and overgrowth disorders. In this review, we will summarize and compare the roles played by each D-type cyclin during development and provide examples of how their intracellular dysregulation can be an underlying cause of disease.

Value of Plasma Methylated SFRP2 in Prognosis of Gastric Cancer

BACKGROUND

Secreted frizzled-related protein 2 (SFRP2) in circulating tumor DNA (ctDNA) is related to gastric cancer (GC) proliferation. However, whether methylated SFRP2 in ctDNA serves as the biomarker in GC patients remains unknown.

AIMS

To investigate the relationship between methylated SFRP2 and the clinical outcomes of GC patients.

METHODS

One hundred and forty-eight GC patients receiving systemic chemotherapy were collected during 2015-2017. Aberrant SFRP2 methylation was detected before and after chemotherapy by digital PCR-based technologies.

RESULTS

Baseline SFRP2 methylation positively correlated with lymph node status (P < 0.001), distant metastasis (P < 0.001) and TNM stage (P = 0.005). The top 50% methylated SFRP2 had shorter progression-free survival (PFS) and overall survival (OS) than those with bottom 50% in stage III GC patients (median PFS, 11.0 vs. NR months; HR 13.05; 95% CI 3.05-55.95; median OS 17.0 vs. NR months; HR 7.80; 95% CI 1.81-33.60) and stage IV GC patients (median PFS, 4.0 vs. 7.0 months; HR 2.74; 95% CI 1.58-4.78; median OS 12.0 vs. 16.0 months; HR 3.14; 95% CI 1.67-5.92). Besides, the increased methylated SFPR2 from baseline to post-treatment was related to the worse PFS and OS among stage IV patients (median PFS, 5.0 vs. 7.0 months; HR 2.17; 95% CI 1.25-3.76; median OS 12.0 vs. 15.5 months; HR 3.51; 95% CI 1.94-6.35), but not to stage III patients.

CONCLUSIONS

SFRP2 methylation and dynamic change are associated with GC prognosis. Our findings provide potential biomarker detection approach in ctDNA for prognosis prediction and dynamic monitoring among GC patients.

Measurement of Cyclin D2 (CCND2) Gene Promoter Methylation in Plasma and Peripheral Blood Mononuclear Cells and Alpha-Fetoprotein Levels in Patients with Hepatitis B Virus-Associated Hepatocellular Carcinoma

Background

Alpha-fetoprotein (AFP) is widely used to screen for hepatocellular carcinoma (HCC). However, the use of this biomarker has been challenged due to its low sensitivity and high rate of false negatives. In this study, we evaluated the diagnostic capability of cyclin D2 (CCND2) promoter methylation in patients with HCC related to hepatitis B virus (HBV).

Material/Methods

Using methylation-specific PCR and quantitative real-time PCR, we measured methylation status and mRNA levels of CCND2 in plasma and peripheral blood mononuclear cells (PBMCs) from 275 subjects: 75 patients with chronic hepatitis B (CHB), 47 with liver cirrhosis (LC), 118 with HCC, and 35 healthy controls (HCs).

Results

The methylation rate of the CCND2 promoter was significantly higher in HCC patients than in patients without HCC (P<0.001). Furthermore, advanced HCC (TNM III/IV) was associated with a significantly higher frequency of CCND2 methylation and lower CCND2 mRNA levels than early-stage disease (TNM I/II; P<0.05). Combined measurement of CCND2 methylation and AFP yielded significantly higher sensitivity and area under the curve (AUC) than AFP alone in distinguishing patients with HCC from subjects with LC and CHB (P<0.001).

Conclusions

CCND2 methylation may be useful for predicting HCC progression. In addition, combined measurement of CCND2 methylation and AFP could serve as a non-invasive diagnostic marker for patients with HBV-related HCC.

Cyclin D degradation by E3 ligases in cancer progression and treatment

D cyclins include three isoforms: D1, D2, and D3. D cyclins heterodimerize with cyclin-dependent kinase 4/6 (CDK4/6) to form kinase complexes that can phosphorylate and inactivate Rb. Inactivation of Rb triggers the activation of E2F transcription factors, which in turn regulate the expression of genes whose products drive cell cycle progression. Because D-type cyclins function as mitogenic sensors that link growth factor signaling directly with G₁ phase progression, it is not surprising that D cyclin accumulation is dysregulated in a variety of human tumors. Elevated expression of D cyclins results from gene amplification, increased gene transcription and protein translation, decreased microRNA levels, and inefficiency or loss of ubiquitylation-mediated protein degradation. This review focuses on the clinicopathological importance of D cyclins, how dysregulation of Ubiquitin-Proteasome System (UPS) contributes to the overexpression of D cyclins, and the therapeutic potential through targeting D cyclin-related machinery in human tumors.

Sulforaphane Decrease of SERTAD1 Expression Triggers G1/S Arrest in Breast Cancer Cells

Studies have identified the potential of chemopreventive effects of sulforaphane (SFN); however, the underlying mechanisms of its effect on breast cancer require further elucidation. This study investigated the anticancer effects of SFN that specifically induces G1/S arrest in breast ductal carcinoma (ZR-75-1) cells. The proliferation of the cancer cells after treatment with SFN was detected by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. DNA content and cell cycle status were analyzed through flow cytometry. Our results demonstrated the inhibition of growth in ZR-75-1 cells upon SFN exposure. In addition, SERTAD1 (SEI-1) caused the accumulation of SFN-treated G1/S-phase cells. The downregulation of SEI-1, cyclin D2, and histone deacetylase 3 suggested that in addition to the identified effects of SFN against breast cancer prevention, it may also exert antitumor activities in established breast cancer cells. In conclusion, SFN can inhibit growth of and induce cell cycle arrest in cancer cells, suggesting its potential role as an anticancer agent.

Prognostic role of cyclin D2/D3 in multiple human malignant neoplasms: A systematic review and meta-analysis

Cyclin D2/D3 (CCND2/3) are core components of the machinery that drives cell cycle progression and therefore, are associated with tumorigenesis. Currently, there are contradictory evidences on the function of CCND2/3 in tumorigenesis. Thus, we conducted a comprehensive meta‐analysis to derive a precise predictive value of CCND2/3 in various tumors. We searched PubMed, EMBASE, Web of Science for eligible studies up to October 8, 2018. Pooled hazard ratios (HRs) with 95% confidence intervals (CIs) of OS or DFS/PFS/RFS were calculated using Forest plot analysis to demonstrate their associations. A total of 14 studies were ultimately included in this meta‐analysis. Our results indicated CCND2/3 played an oncogenic role in all of the cancer patients (CCND2: pooled HR = 2.21, 95% CI: 1.67‐2.93; CCND3: pooled HR = 2.29, 95% CI: 1.05‐5.03). In tumor subgroup, CCND2 was associated with shorter OS in patients with gastric cancer (HR = 2.20, 95% CI: 1.66‐2.92), whereas it might be a tumor suppressor in NSCLC (HR = 0.28, 95% CI: 0.12‐0.64). In addition, CCND3 was correlated to reduced OS in breast cancer patients (HR = 1.64, 95% CI: 1.07‐2.52) and shorter DFS/PFS/RFS in bladder cancer patients (HR = 4.60, 95% CI: 1.89‐12.57). Taken together, CCND2/3 could be the promising biomarkers for predicting the prognosis of patients with malignant neoplasms.

Clinical significance and biological roles of cyclins in gastric cancer

Background and aim

Cyclins have been reported to be overexpressed with poor prognosis in several human cancers. However, limited numbers of studies evaluated the expressions and prognostic roles of cyclins in gastric cancer (GC). We aim to evaluate the expressions and prognostic roles of cyclins. Also, further efforts were made to explore biological function of the differentially expressed cyclins.

Methods

Cyclins expressions were analyzed by Oncomine and The Cancer Genome Atlas datasets, and the prognostic roles of cyclins in GC patients were investigated by the Kaplan–Meier Plotter database. Then, a comprehensive PubMed literature search was performed to identify expression and prognosis of cyclins in GC. Biological functions of the differentially expressed cyclins were explored through Enrich R platform, and KEGG and transcription factor were analyzed.

Results

The expression levels of CCNA2 (cyclin A2), CCNB1 (cyclin B1), CCNB2 (cyclin B2), and CCNE1 (cyclin E1) mRNAs were identified to be significantly higher in GC tissues than in normal tissues in both Oncomine and The Cancer Genome Atlas datasets. High expressions of CCNA2, CCNB1, and CCNB2 mRNAs were identified to be related with poor overall survival in Kaplan–Meier Plotter dataset. Evidence from clinical studies showed that CCNB1 was related with overall survival in GC patients. Cyclins were associated with several biological pathways, including cell cycle, p53 signaling pathway, FoxO signaling pathway, viral carcinogenesis, and AMPK signaling pathway. Enrichment analysis also showed that cyclins interacted with some certain transcription factors, such as FOXM1, SIN3A, NFYA, and E2F4.

Conclusion

Based on our results, high expressions of cyclins were related with poor prognosis in GC patients. The above information might be useful for better understanding the clinical and biological roles of cyclins mRNA and guiding individualized treatments for GC patients.

Cyclin D1 overexpression correlates with poor tumor differentiation and prognosis in gastric cancer

Overexpression of cyclin D is associated with the molecular tumorigenesis of gastric cancer. The purpose of the present study was to investigate the expression of cyclin D in human gastric cancer and to determine the potential correlations between cyclin D expression and clinicopathological characteristics of specific histological types, as well as its prognostic significance. In the present study, the expression of the cyclin D1 (CCND1), cyclin D2 (CCND2) and cyclin D3 (CCND3) genes in gastric cancer patients was explored using the Oncomine database, and their correlation with overall survival (OS) and progression-free survival (PFS) was evaluated using Kaplan-Meier analysis. The prognostic significance of CCND1 protein expression was evaluated by western blot analysis of 32 matched specimens of gastric adenocarcinomas and normal tissues obtained from patients treated at the National Cheng Kung University Hospital (Tainan, Taiwan). Analysis of the Oncomine cancer microarray database revealed that CCND1 gene expression was significantly increased in gastric intestinal-type adenocarcinoma, while CCND2 was significantly increased in diffuse gastric adenocarcinoma, gastric intestinal-type adenocarcinoma and gastric mixed adenocarcinoma. Kaplan-Meier analysis indicated that overexpression of CCND1 was associated with reduced OS and PFS. In addition, overexpression of CCND1 and downregulation of CCND2 were significantly correlated with receptor tyrosine-protein kinase erb-2-negative tumors and poor differentiation. The ratio of relative CCND1 expression (expressed as the CCND1/β-actin ratio) in tumor tissues compared with that in normal tissues was correlated with poor differentiation (P=0.0018). In summary, CCND1 overexpression is associated with shorter survival in patients with gastric cancer and with poorly differentiated tumors.

Demethylation and alterations in the expression level of the cell cycle-related genes as possible mechanisms in arsenic trioxide-induced cell cycle arrest in human breast cancer cells

Arsenic trioxide (As₂O₃) has been used clinically as an anti-tumor agent. Its mechanisms are mostly considered to be the induction of apoptosis and cell cycle arrest. However, the detailed molecular mechanisms of its anti-cancer action through cell cycle arrest are poorly known. Furthermore, As₂O₃ has been shown to be a potential DNA methylation inhibitor, inducing DNA hypomethylation. We hypothesize that As₂O₃ may affect the expression of cell cycle regulatory genes by interfering with DNA methylation patterns. To explore this, we examined promoter methylation status of 24 cell cycle genes in breast cancer cell lines and in a normal breast tissue sample by methylation-specific polymerase chain reaction and/or restriction enzyme-based methods. Gene expression level and cell cycle distribution were quantified by real-time polymerase chain reaction and flow cytometric analyses, respectively. Our methylation analysis indicates that only promoters of RBL1 (p107), RASSF1A, and cyclin D2 were aberrantly methylated in studied breast cancer cell lines. As₂O₃ induced CpG island demethylation in promoter regions of these genes and restores their expression correlated with DNA methyltransferase inhibition. As₂O₃ also induced alterations in messenger RNA expression of several cell cycle-related genes independent of demethylation. Flow cytometric analysis revealed that the cell cycle arrest induced by As₂O₃ varied depending on cell lines, MCF-7 at G1 phase and both MDA-MB-231 and MDA-MB-468 cells at G2/M phase. These changes at transcriptional level of the cell cycle genes by the molecular mechanisms dependent and independent of demethylation are likely to represent the mechanisms of cell cycle redistribution in breast cancer cells, in response to As₂O₃ treatment.

The Silencing of CCND2 by Promoter Aberrant Methylation in Renal Cell Cancer and Analysis of the Correlation between CCND2 Methylation Status and Clinical Features

Cyclin D2 (CCND2) is a member of the D-type cyclins, which plays a pivotal role in cell cycle regulation, differentiation and malignant transformation. However, its expression status and relative regulation mechanism remains unclear in renal cell cancer (RCC). In our study, the mRNA expression level of CCND2 is down-regulated in 22/23 paired RCC tissues (p<0.05). In addition, its protein expression level is also decreased in 43/43 RCC tumor tissues compared with its corresponding non-malignant tissues (p<0.001). We further detected that CCND2 was down-regulated or silenced in 6/7 RCC cell lines, but expressed in “normal” human proximal tubular (HK-2) cell line. Subsequently, MSP and BGS results showed that the methylation status in CCND2 promoter region is closely associated with its expression level in RCC cell lines. Treatment with 5-Aza with or without TSA restored CCND2 expression in several methylated RCC cell lines. Among the 102 RCC tumors, methylation of CCND2 was detected in 29/102 (28%) cases. Only 2/23 (8.7%) adjacent non-malignant tissues showed methylation. We then analyzed the correlation of clinical features and its promoter methylation. Collectively, our data suggested that loss of CCND2 expression is closely associated with the promoter aberrant methylation.

A Cyclin D2-derived peptide acts on specific cell cycle phases by activating ERK1/2 to cause the death of breast cancer cells

Protein degradation by the proteasome generates functional intracellular peptides. Pep5, a peptide derived from Cyclin D2, induces cell death in tumor cell lines and reduces the volume of rat C6 glioblastoma tumors in vivo. Here, we chose the human MDA-MB-231 breast cancer cells to evaluate the mechanism of cell death induced by pep5 in different phases of the cell cycle. Fluorescently labeled pep5, monitored by real time confocal microscopy, entered the MDA-MB-231 cells 3min after application and localized to the nucleus and cytoplasm. Pep5-induced cell death was increased when the MDA-MB-231 cell population was arrested at the G1/S transition or in S phase compared to asynchronous cells. Pep5 induced permanent extracellular signal-regulated kinase (ERK1/2) phosphorylation in MDA-MB-231 cells synchronized in G1/S or S phase. Affinity chromatography followed by mass spectrometry identified CLIC1 and Plectin as the only two proteins that interacted with pep5 in both asynchronous and synchronized MDA-MB-231 cells. These interactions could explain the long-lasting ERK1/2 phosphorylation and the cytoskeleton perturbations in the MDA-MB-231 cells, in which the stress fibers' integrity is affected by pep5 treatments. These data suggest that pep5 has potential therapeutic properties for treating specific types of cancers, such as breast cancer cells.

BIOLOGICAL SIGNIFICANCE

Pep5, a natural intracellular peptide formed by the degradation of Cyclin D2 through the ubiquitin-proteasome system, induces cell death when reintroduced into MDA-MB-231 breast cancer cells, which express low levels of Cyclin D2, specifically in G1/S arrested cells or in cells that are passing through S phase. Under these conditions, pep5 is able to interact with different intracellular proteins, primarily cytoskeleton and proteasome components, which can lead to cellular apoptosis. Together, our data suggest that pep5 is an intracellular peptide with therapeutic potential for treating specific types of tumors with low expression of Cyclin D2 by inhibiting cell proliferation.

An epigenetic marker panel for recurrence risk prediction of low grade papillary urothelial cell carcinoma (LGPUCC) and its potential use for surveillance after transurethral resection using urine

By a candidate gene approach, we analyzed the promoter methylation (PM) of 8 genes genes (ARF, TIMP3, RAR-β2, NID2, CCNA1, AIM1, CALCA and CCND2) by quantitative methylation specific PCR (QMSP) in DNA of 17 non-recurrent and 19 recurrent noninvasive low grade papillary urothelial cell carcinoma (LGPUCC) archival tissues. Among the genes tested, by establishing an empiric cutoff value, CCND2, CCNA1, NID2, and CALCA showed higher frequency of methylation in recurrent than in non-recurrent LGPUCC: CCND2 10/19 (53%) vs. 2/17 (12%) (p=0.014); CCNA1 11/19 (58%) vs. 4/17 (23.5%) (p=0.048); NID2 13/19 (68%) vs. 3/17 (18%) (p=0.003) and CALCA 10/19 (53%) vs. 4/17 (23.5%) (p=0.097), respectively. We further analyzed PM of CCND2, CCNA1, and CALCA in urine DNA from UCC patients including LGPUCC and controls. The frequency of CCND2, CCNA1 and CALCA was significantly higher (p<0.0001) in urine of UCC cases [ 38/148 (26%), 50/73 (68%) and 94/148 (63.5%) respectively] than controls [0/56 (0%), 10/60 (17%) and 16/56 (28.5%), respectively)]. Most importantly we found any one of the 3 markers methylation positive in 25 out of 30 (83%) cytology negative LGPUCC cases. We also explored the biological function of CCNA1 in UCC. Prospective confirmatory studies are needed to develop a reliable tool for prediction of recurrence using primary LGPUCC tissues and/or urine.

PIAS1 regulates breast tumorigenesis through selective epigenetic gene silencing

Epigenetic gene silencing by histone modifications and DNA methylation is essential for cancer development. The molecular mechanism that promotes selective epigenetic changes during tumorigenesis is not understood. We report here that the PIAS1 SUMO ligase is involved in the progression of breast tumorigenesis. Elevated PIAS1 expression was observed in breast tumor samples. PIAS1 knockdown in breast cancer cells reduced the subpopulation of tumor-initiating cells, and inhibited breast tumor growth in vivo. PIAS1 acts by delineating histone modifications and DNA methylation to silence the expression of a subset of clinically relevant genes, including breast cancer DNA methylation signature genes such as cyclin D2 and estrogen receptor, and breast tumor suppressor WNT5A. Our studies identify a novel epigenetic mechanism that regulates breast tumorigenesis through selective gene silencing.

Valproic acid inhibits the proliferation of cancer cells by re-expressing cyclin D2

In this study, primary murine prostate cancer (PCa) cells were derived using the well-established TRAMP model. These PCa cells were treated with the histone deacetylase inhibitor, valproic acid (VPA), and we demonstrated that VPA treatment has an antimigrative, antiinvasive and antiproliferative effect on PCa cells. Using microarray analyses, we discovered several candidate genes that could contribute to the cellular effects we observed. In this study, we could demonstrate that VPA treatment of PCa cells causes the re-expression of cyclin D2, a known regulator that is frequently lost in PCa as we could show using immunohistochemical analyses on PCa specimens. We demonstrate that VPA specifically induces the re-expression of cyclin D2, one of the highly conserved D-type cyclin family members, in several cancer cell lines with weak or no cyclin D2 expression. Interestingly, VPA treatment had no effect in fibroblasts, which typically have high basal levels of cyclin D2 expression. The re-expression of cyclin D2 observed in PCa cells is activated by increased histone acetylation in the promoter region of the Ccnd2 gene and represents one underlying molecular mechanism of VPA treatment that inhibits the proliferation of cancer cells. Altogether, our results confirm that VPA is an anticancer therapeutic drug for the treatment of tumors with epigenetically repressed cyclin D2 expression.

Bile acids down-regulate caveolin-1 in esophageal epithelial cells through sterol responsive element-binding protein

Bile acids are synthesized from cholesterol and are major risk factors for Barrett adenocarcinoma (BAC) of the esophagus. Caveolin-1 (Cav1), a scaffold protein of membrane caveolae, is transcriptionally regulated by cholesterol via sterol-responsive element-binding protein-1 (SREBP1). Cav1 protects squamous epithelia by controlling cell growth and stabilizing cell junctions and matrix adhesion. Cav1 is frequently down-regulated in human cancers; however, the molecular mechanisms that lead to this event are unknown. We show that the basal layer of the nonneoplastic human esophageal squamous epithelium expressed Cav1 mainly at intercellular junctions. In contrast, Cav1 was lost in 95% of tissue specimens from BAC patients (n = 100). A strong cytoplasmic expression of Cav1 correlated with poor survival in a small subgroup (n = 5) of BAC patients, and stable expression of an oncogenic Cav1 variant (Cav1-P132L) in the human BAC cell line OE19 promoted proliferation. Cav1 was also detectable in immortalized human squamous epithelial, Barrett esophagus (CPC), and squamous cell carcinoma cells (OE21), but was low in BAC cell lines (OE19, OE33). Mechanistically, bile acids down-regulated Cav1 expression by inhibition of the proteolytic cleavage of 125-kDa pre-SREBP1 from the endoplasmic reticulum/Golgi apparatus and nuclear translocation of active 68-kDa SREBP1. This block in SREBP1's posttranslational processing impaired transcriptional activation of SREBP1 response elements in the proximal human Cav1 promoter. Cav1 was also down-regulated in esophagi from C57BL/6 mice on a diet enriched with 1% (wt/wt) chenodeoxycholic acid. Mice deficient for Cav1 or the nuclear bile acid receptor farnesoid X receptor showed hyperplasia and hyperkeratosis of the basal cell layer of esophageal epithelia, respectively. These data indicate that bile acid-mediated down-regulation of Cav1 marks early changes in the squamous epithelium, which may contribute to onset of Barrett esophagus metaplasia and progression to BAC.

Promoter de-methylation of cyclin D2 by sulforaphane in prostate cancer cells

Sulforaphane (SFN), an isothiocyanate derived from cruciferous vegetables, induces potent anti-proliferative effects in prostate cancer cells. One mechanism that may contribute to the anti-proliferative effects of SFN is the modulation of epigenetic marks, such as inhibition of histone deacetylase (HDAC) enzymes. However, the effects of SFN on other common epigenetic marks such as DNA methylation are understudied. Promoter hyper-methylation of cyclin D2, a major regulator of cell cycle, is correlated with prostate cancer progression, and restoration of cyclin D2 expression exerts anti-proliferative effects on LnCap prostate cancer cells. Our study aimed to investigate the effects of SFN on DNA methylation status of cyclin D2 promoter, and how alteration in promoter methylation impacts cyclin D2 gene expression in LnCap cells. We found that SFN significantly decreased the expression of DNA methyltransferases (DNMTs), especially DNMT1 and DNMT3b. Furthermore, SFN significantly decreased methylation in cyclin D2 promoter regions containing c-Myc and multiple Sp1 binding sites. Reduced methlyation of cyclin D2 promoter corresponded to an increase in cyclin D2 transcript levels, suggesting that SFN may de-repress methylation-silenced cyclin D2 by impacting epigenetic pathways. Our results demonstrated the ability of SFN to epigenetically modulate cyclin D2 expression, and provide novel insights into the mechanisms by which SFN may regulate gene expression as a prostate cancer chemopreventive agent.

Epigenetic inactivation and tumor suppressor activity of HAI-2/SPINT2 in gastric cancer

Hepatocyte growth factor (HGF) activator inhibitor type 2 (HAI-2/SPINT2) encodes Kunitz-type protease inhibitor that regulates HGF activity. Inspection of the human HAI-2/SPINT2 locus uncovered a large and dense CpG island within the 5' region of this gene. Analysis of cultured human gastric tumor lines indicated that HAI-2/SPINT2 expression is either undetectable or in low abundance in several lines; however, enhanced gene expression was measured in cells cultured on the DNA demethylating agent 5-aza-2'-deoxycytidine. Bisulfite DNA sequencing confirmed the densely methylated HAI-2/SPINT2 promoter region. Forced expression of HAI-2/SPINT2 induced cell apoptosis, suppressed anchorage independent growth in vitro and tumor growth in vivo. We investigated HAI-2/SPINT2 aberrant methylation in patients with gastric cancer. The HAI-2/SPINT2 methylation was found preferentially in cancerous tissues (30 of 40, 75%) compared with nontumor tissues (no methylation was detected), indicating that this aberrant characteristic is common in gastric malignancies. In conclusion, epigenetic inactivation of HAI-2/SPINT2 is a common event contributing to gastric carcinogenesis and may be a potential biomarker for gastric cancer.

Methylated cyclin D2 gene circulating in the blood as a prognosis predictor of hepatocellular carcinoma

BACKGROUND

Prognosis of hepatocellular carcinoma (HCC) remains poor because of high recurrence rate. We examined preoperatively the methylated CCND2 gene levels present in the serum following release from HCC cells as a prognosis predictor in patients undergoing curative hepatectomy.

METHODS

Quantitative real-time RT-PCR and quantitative methylation-specific PCR were used to measure methylated CCND2 gene and its mRNA levels.

RESULTS

The CCND2 mRNA levels were down-regulated in HCC with early intrahepatic recurrence (IHR) within 1year of curative hepatectomy. We also identified that this down-regulation was due to promoter hypermethylation. In 70 HCC patients who underwent curative hepatectomy, 39 patients sero-positive for the methylated CCND2 gene (>70pg/ml serum) exhibited a significantly shorter disease-free survival (DFS) period (P=0.02) than the 31 patients who were sero-negative for the methylated CCND2 gene. None of the sero-negative patients demonstrated early IHR, and this method of serum testing did not produce any false-negative predictions for early IHR. Multivariate analysis showed that the serum level of methylated CCND2 was an independent risk factor for DFS (hazard ratio of 1.866, 95% CI: 1.106-3.149).

CONCLUSION

Methylated CCND2 gene in the serum serves as a prognosis predictor of HCC after curative hepatectomy.

Cytogenetic and molecular characterization of plutonium-induced rat osteosarcomas

The association between ionizing radiation and the subsequent development of osteosarcoma has been well described, but little is known about the cytogenetic and molecular events, which could be involved in the formation of radiation-induced osteosarcomas. Here, we performed comparative genomic hybridization (CGH) to detect chromosomal copy number changes in a series of 16 rat osteosarcomas induced by injection of plutonium-238. Recurrent gains/amplifications were observed at chromosomal regions 3p12-q12, 3q41-qter, 4q41-qter, 6q12-q16, 7q22-q34, 8q11-q23, 9q11-q22, 10q32.1-qter, and 12q, whereas recurrent losses were observed at 1p, 1q, 3q23-q35, 5q21-q33, 8q24-q31, 10q22-q25, 15p, 15q, and 18q. The gained region at 7q22-q34 was homologous to human chromosome bands 12q13-q15/8q24/22q11-q13, including the loci of Mdm2, Cdk4, c-Myc and Pdgf-b genes. The lost regions at 5q21-q33, 10q22-q25 and 15q contained tumor suppressor genes such as p16INK4a/p19ARF, Tp53 and Rb1. To identify potential target gene(s) for the chromosomal aberrations, we compared the expression levels of several candidate genes, located within the regions of frequent chromosomal aberrations, between the tumors and normal osteoblasts by using quantitative RT-PCR analysis. The Cdk4, c-Myc, Pdgf-b and p57KIP2 genes were thought to be possible target genes for the frequent chromosomal gain at 7q22-34 and loss at 1q in the tumors, respectively. In addition, mutations of the Tp53 gene were found in 27% (4 of 15) osteosarcomas. Our data may contribute to further understanding of the molecular mechanisms underlying osteosarcomas induced by ionizing radiation in human.

Establishment of a new human osteosarcoma cell line, UTOS-1: cytogenetic characterization by array comparative genomic hybridization

The cytogenetic characteristics of osteosarcoma (OS) remain controversial. The establishment of a new human OS cell line may improve the characterization. We report the establishment of a new human osteosarcoma cell line, UTOS-1, from a typical osteoblastic OS of an 18-year-old man. Cultured UTOS-1 cells are spindle-shaped, and have been maintained in vitro for over 50 passages in more than 2 years. Xenografted UTOS-1 cells exhibit features typical of OS, such as production of osteoid or immature bone matrix, and proliferation potency in vivo. UTOS-1 also exhibit morphological and immunohistochemical characteristics typical of osteoblastic OS. Chromosomal analysis by G-band show 73~85 chromosomes with complicated translocations. Array CGH show frequent gains at locus DAB2 at chromosome 5q13, CCND2 at 12p13, MDM2 at 12q14.3-q15, FLI and TOP3A at 17p11.2-p12 and OCRL1 at Xq25, and show frequent losses at HTR1B at 6q13, D6S268 at 6q16.3-q21, SHGC17327 at 18ptel, and STK6 at 20q13.2-q13.3. The UTOS-1 cell line may prove useful for biologic and molecular pathogenetic investigations of human OS.

Methylation of protocadherin 10, a novel tumor suppressor, is associated with poor prognosis in patients with gastric cancer

BACKGROUND & AIMS

By using methylation-sensitive representational difference analysis, we identified protocadherin 10 (PCDH10), a gene that encodes a protocadherin and is silenced in a tumor-specific manner. We analyzed its epigenetic inactivation, biological effects, and prognostic significance in gastric cancer.

METHODS

Methylation status was evaluated by combined bisulfite restriction analysis and bisulfite sequencing. The effects of PCDH10 re-expression were determined in growth, apoptosis, proliferation, and invasion assays. PCDH10 target genes were identified by complementary DNA microarray analysis.

RESULTS

PCDH10 was silenced or down-regulated in 94% (16 of 17) of gastric cancer cell lines; expression levels were restored by exposure to demethylating agents. Re-expression of PCDH10 in MKN45 gastric cancer cells reduced colony formation in vitro and tumor growth in mice; it also inhibited cell proliferation (P < .01), induced cell apoptosis (P < .001), and repressed cell invasion (P < .05), up-regulating the pro-apoptosis genes Fas, Caspase 8, Jun, and CDKN1A; the antiproliferation gene FGFR; and the anti-invasion gene HTATIP2. PCDH10 methylation was detected in 82% (85 of 104) of gastric tumors compared with 37% (38 of 104) of paired nontumor tissues (P < .0001). In the latter, PCDH10 methylation was higher in precancerous lesions (27 of 45; 60%) than in chronic gastritis samples (11 of 59; 19%) (P < .0001). After a median follow-up period of 16.8 months, multivariate analysis revealed that patients with PCDH10 methylation in adjacent nontumor areas had a significant decrease in overall survival. Kaplan-Meier survival curves showed that PCDH10 methylation was associated significantly with shortened survival in stage I-III gastric cancer patients.

CONCLUSIONS

PCDH10 is a gastric tumor suppressor; its methylation at early stages of gastric carcinogenesis is an independent prognostic factor.

Epigenetic identification of ubiquitin carboxyl-terminal hydrolase L1 as a functional tumor suppressor and biomarker for hepatocellular carcinoma and other digestive tumors

The ubiquitin carboxyl-terminal hydrolase L1 (UCHL1) is a carboxyl-terminal ubiquitin hydrolase regulating cellular ubiquitin levels, recently suggested as a tumor suppressor. However, the role of UCHL1 in hepatocellular carcinoma (HCC) is not clear. We investigated the expression and DNA methylation of the UCHL1 in primary HCC, liver metastases from digestive carcinomas, and primary digestive cancers. UCHL1 is expressed in all normal tissues and immortalized normal epithelial cell lines, but was low or silenced in 77% (10/13) of HCC cell lines, which is well correlated with its promoter methylation status. Methylation was further detected in 44% (12/27) of HCCs, but less in metastatic tumors generated from colorectal and stomach in the liver (19%, 3/16; P < 0.05). Methylation was also detected in primary digestive tumors, including 71% (22/31) of colon, 77% (53/69) of gastric, and 40% (18/45) of esophageal carcinomas, but none or occasionally in paired adjacent nontumor tissues. Detailed methylation analysis of 49 CpG sites at a 540-bp promoter region by bisulfite genomic sequencing confirmed the methylation. UCHL1 silencing could be reversed by chemical or genetic demethylation of the promoter, indicating direct epigenetic silencing. Restoring UCHL1 expression in silenced cell lines significantly inhibited their growth and colony formation ability by inhibiting cell proliferation, causing cell cycle arrest in G2/M phase and inducing apoptosis through the intrinsic caspase-dependent pathway. Moreover, UCHL1 directly interacts with p53 and stabilizes p53 through the ubiquitination pathway.

CONCLUSION

Epigenetic inactivation of UCHL1 is common in primary HCCs and other digestive tumors. UCHL1 appears to be a functional tumor suppressor involved in the tumorigenesis of HCCs and other digestive cancers.

Frequent epigenetic inactivation of secreted frizzled-related protein 2 (SFRP2) by promoter methylation in human gastric cancer

The role of secreted frizzled-related protein (SFRP) genes in gastric cancer remains largely unknown. We determined the frequency and functional significance of SFRPs hypermethylation in human gastric cancer. The expression and methylation status of four SFRP members (SFRP1, 2, 4, and 5) in primary gastric cancer samples was screened. The biological effects of SFRP were analysed by flow cytometry, cell viability assay and in vivo tumour growth in nude mice. Among the four SFRPs, only SFRP2 was significantly downregulated in gastric cancer as compared to adjacent non-cancer samples (P<0.01). Promoter hypermethylation of SFRP2 was detected in 73.3% primary gastric cancer tissues, 37.5% of samples showing intestinal metaplasia and 20% adjacent normal gastric tissues. Bisulphite DNA sequencing confirmed the densely methylated SFRP2 promoter region. Demethylation treatment restored the expression of SFRP2 in gastric cancer cell lines. Forced expression of SFRP2 induced cell apoptosis, inhibited proliferation of gastric cancer cells and suppressed tumour growth in vivo. Moreover, methylated SFRP2 was detected in 66.7% of serum samples from cancer patients but not in normal controls. In conclusion, epigenetic inactivation of SFRP2 is a common and early event contributing to gastric carcinogenesis and may be a potential biomarker for gastric cancer.

Promoter methylation status of the Cyclin D2 gene is associated with poor prognosis in human epithelial ovarian cancer

Gene silencing associated with aberrant DNA methylation of promoter CpG islands is one mechanism through which several genes may be inactivated in human cancers. Cyclin D2, a member of the D-type cyclins, implicated in cell cycle regulation, differentiation and malignant transformation, is inactivated due to aberrant DNA methylation in several human cancers. In the present study, we examined the promoter methylation status and expression of Cyclin D2 in human epithelial ovarian cancer, and then determined the relationship between methylation status and various clinicopathological variables. Twelve ovarian cancer cell lines and 71 surgical specimens were examined by methylation-specific polymerase chain reaction and quantitative reverse transcription-polymerase chain reaction to evaluate the methylation status and expression of the Cyclin D2 gene. The relationship between methylation status and various clinicopathological variables was evaluated using statistical analysis. Aberrant methylation of Cyclin D2 was present in five of 12 ovarian cancer cell lines and 16 of 71 primary ovarian cancer tissues. In five cell lines with methylation, expression of the Cyclin D2 gene tended to be lower than in cell lines without methylation. In ovarian cancer tissues, methylation bands were detected in 16 of 71 cases. The methylation status of Cyclin D2 was associated with advanced stage and a residual tumor size (>2 cm) (P = 0.027 and P = 0.031, respectively). Based on univariate analysis, patients with aberrant methylation of the Cyclin D2 promoter had a significantly worse chance of disease-free survival than those without methylation (P = 0.021). Our results suggest that aberrant promoter methylation of the Cyclin D2 gene is significantly associated with patient prognosis in epithelial ovarian cancer.

Hypermethylation of Cyclin D2 is associated with loss of mRNA expression and tumor development in prostate cancer

D-type cyclins play a pivotal role in cell cycle regulation and their abnormal expression was associated with several human malignancies. To assess Cyclin D2 promoter methylation status and expression levels in prostate tissues, quantitative methylation-specific PCR and quantitative reverse transcription PCR assays were performed in a large series of prostate carcinomas, high-grade prostatic intraepithelial neoplasias (HGPIN), benign prostate hyperplasias (BPH), normal prostate tissue (NPT) samples, and prostate cancer (PCa) cell lines (before and after demethylating treatment). Methylation levels were correlated with mRNA expression levels and key clinicopathologic parameters. Cyclin D2 promoter methylation was found in 117/118 PCa, 38/38 HGPIN, 24/30 BPH, 11/11 NPT, and 4/4 cell lines. Methylation levels were significantly higher in PCa compared with HGPIN, NPT, and BPH (P<0.0001), correlating with tumor stage and Gleason score (r=0.29, P=0.0014; and r=0.32, P=0.0005, respectively). Conversely, Cyclin D2 mRNA levels were significantly lower in PCa (P<0.01) and a significant inverse correlation between Cyclin D2 methylation and expression levels was found in prostatic tissues (r=-0.61, P<0.000001). Demethylating treatment induced a substantial increase in Cyclin D2 mRNA in LNCaP cells whereas decreased levels were observed in DU-145 and PC-3 cells. We concluded that Cyclin D2 promoter methylation downregulates gene transcription and occurs with high frequency at low levels in normal, hyperplastic, and preneoplastic prostate tissues. Conversely, high Cyclin D2 methylation levels characterize invasive prostatic carcinoma, correlating with clinicopathologic features of tumor aggressiveness.

Molecular screening of gastric cancer by proteome analysis

Gastric cancer affects annually more than 800,000 individuals worldwide and remains a challenge for clinicians and oncologists. Most patients with gastric cancer are diagnosed in advanced stages, when a curative resection is impossible, which leads to an overall poor prognosis. Finding new diagnostic and treatment procedures is of paramount importance to improve patient prognosis, which will be improved most dramatically by techniques that allow the detection of gastric cancer in its early stages. So far the value of conventional tumour markers such as Ca72-4 or carcinoembryonic antigen is limited, and even markers developed from molecular biological studies on the carcinogenesis of gastric cancer, such as E-cadherin and others, have not proved to be of adequate sensitivity and specificity to allow the early detection of gastric cancer. With the development of innovative diagnostic tools, such as proteome analysis, new biomarkers may be identified that may allow early diagnosis and thus screening for gastric cancer, particularly in at-risk patient populations. Recent studies have indicated that these biomarkers may be derived from the tumour itself or reflect a specific metabolic or immunological response to cancer that can be used to find gastric cancer patients at an early and putatively curative stage of the disease.

Expression of D-type cyclins in colon cancer and in cell lines from colon carcinomas

Cyclins D1, D2 and D3 play important roles in cell proliferation and differentiation. Although their abnormal expression has been linked to cancer development and progression in a number of tissues, the expression of cyclin D2 and D3 proteins in colon cancer has not yet been characterised. In this study, we examined cyclin D1, D2 and D3 protein expression by Western blot analysis in tumour and adjacent normal colon tissues of 57 patients. In addition, we examined D-type cyclins protein expression in HT29 and LoVo39 cell lines from colon carcinomas, as a function of induced proliferation and differentiation. In both cell lines, the expression of the three D-type cyclins increased as a result of induced proliferation, whereas the expression of cyclin D3 increased as a result of induced differentiation. In colon tumours, cyclin D1 was overexpressed in 44%, cyclin D2 was overexpressed in 53% and cyclin D3 was overexpressed in 35% of the cases. We also found that in 16% of the cases, cyclin D3 protein expression was reduced in the tumour, as compared to the adjacent normal tissue. Examination of D-type cyclin protein overexpression in relation to the TNM stage of the tumours revealed that overexpression of cyclins D1 and/or D2, but not cyclin D3, is linked to colon carcinogenesis and that overexpression of cyclin D2 may be related to a higher TNM stage of the tumour.

Distinct methylation patterns of benign and malignant liver tumors revealed by quantitative methylation profiling

PURPOSE

A comparative quantitative methylation profiling of hepatocellular carcinoma and the most frequent benign liver tumor, hepatocellular adenoma, was set up for the identification of tumor-specific methylation patterns.

EXPERIMENTAL DESIGN

The quantitative methylation levels of nine genes (RASSF1A, cyclinD2, p16INK4a, DAP-K, APC, RIZ-1, HIN-1, GSTpi1, SOCS-1) were analyzed in hepatocellular carcinoma and adjacent normal tissue (n = 41), hepatocellular adenoma and adjacent normal tissue (n = 26), focal nodular hyperplasia (n = 10), and unrelated normal liver tissue (n = 28). Accumulated methylation data were analyzed using various statistical algorithms, including hierarchical clustering, to detect tumor-specific methylation patterns.

RESULTS

Cluster analysis revealed that hepatocellular adenoma displays a methylation profile much more similar to that found in normal liver tissue and focal nodular hyperplasia than to that found in hepatocellular carcinoma. Many characteristic differences were not detected when using mere qualitative methylation assays. The cyclinD2 gene was identified as a new and frequent target for aberrant hypermethylation in hepatocellular carcinoma (68%). In the control group of 28 liver specimens from healthy donors, a clear correlation between age of patient and frequency and level of aberrant methylation was seen, which could not be detected in the group of hepatocellular carcinoma specimens.

CONCLUSIONS

Methylation profiling can clearly contribute to the unequivocal classification of suspicious lesions, but only if done in a quantitative manner applying cell type and gene-specific thresholds. In hepatocellular carcinoma, the altered methylation patterns accompanying malignant transformation override the age-dependent increase in gene methylation.

Gene expression profiling of choline-deprived neural precursor cells isolated from mouse brain

Choline is an essential nutrient and an important methyl donor. Choline deficiency alters fetal development of the hippocampus in rodents and these changes are associated with decreased memory function lasting throughout life. Also, choline deficiency alters global and gene-specific DNA methylation in several models. This gene expression profiling study describes changes in cortical neural precursor cells from embryonic day 14 mice, after 48 h of exposure to a choline-deficient medium. Using Significance Analysis of Microarrays, we found the expression of 1003 genes to be significantly changed (from a total of 16,000 total genes spotted on the array), with a false discovery rate below 5%. A total of 846 genes were overexpressed while 157 were underexpressed. Classification by gene ontology revealed that 331 of these genes modulate cell proliferation, apoptosis, neuronal and glial differentiation, methyl metabolism, and calcium-binding protein classes. Twenty-seven genes that had changed expression have previously been reported to be regulated by promoter or intron methylation. These findings support our previous work suggesting that choline deficiency decreases the proliferation of neural precursors and possibly increases premature neuronal differentiation and apoptosis.

Distinction of acute lymphoblastic leukemia from acute myeloid leukemia through microarray-based DNA methylation analysis

Patterns of DNA methylation are substantially altered in malignancies compared to normal tissue, with both genome-wide hypomethylation and regional increase of cytosine methylation at dinucleotides of cytosine and guanine, i.e., CpG dinucleotides. While genome-wide hypomethylation renders chromosomes instable, hypermethylation of CpGs in promoter regions is generally associated with transcriptional silencing, e.g., of tumor suppressor genes. To investigate whether disease-specific methylation profiles exist for different entities of acute leukemia, a microarray-based DNA methylation analysis simultaneously assessing 249 CpG dinucleotides originating from 57 genes was employed. Hereby, samples from precursor B-cell acute lymphoblastic leukemia (ALL) could be distinguished from cases of acute myeloid leukemia by virtue of N33, EGR4, CDC2, CCND2, or MOS hypermethylation in ALL.