[Show abstract][Hide abstract] ABSTRACT: Glycogen synthase kinase 3β (GSK3β) is a serine/threonine protein kinase involved in human cancers including glioblastoma. We have previously demonstrated that GSK3β inhibition enhances temozolomide effect in glioma cells. In this report, we investigated the molecular mechanisms of sensitization of glioblastoma cells to temozolomide by GSK3β inhibition, focusing on O(6)-methylguanine DNA methyltransferase (MGMT) gene silencing. Glioblastoma tissues from patients treated with the GSK3β-inhibiting drugs were subjected to immunohistochemistry and methylation-specific polymerase chain reaction (MSP) assay. Human glioblastoma cell lines T98G, U138, U251 and U87 were treated with a small-molecule GSK3β inhibitor, AR-A014418 or GSK3β-specific siRNA. The combined effect of temozolomide and AR-A014418 on cell proliferation was determined by AlamarBlue assay and an isobologram method. MGMT promoter methylation was estimated by MSP and MethyLight assay. MGMT gene expression was evaluated by real-time quantitative reverse transcriptase-polymerase chain reaction. c-Myc and DNA (cytosine-5)-methyltransferase 3A (DNMT3A) binding to the MGMT promoter was estimated by chromatin immunoprecipitation assay. GSK3β inhibition decreased phosphorylation of glycogen synthase and reduced MGMT expression, and increased MGMT promoter methylation in clinical tumors. In glioblastoma cell lines, GSK3β inhibition decreased cell viability, enhanced temozolomide effect, and downregulated MGMT expression with relevant changes in the methylation levels of the MGMT promoter. Here, we showed for the first time that c-Myc binds to the MGMT promoter with consequent recruitment of DNMT3A, regulating the levels of MGMT promoter methylation. The results of this study suggest that GSK3β inhibition enhances temozolomide effect by silencing MGMT expression via c-Myc-mediated promoter methylation..
[Show abstract][Hide abstract] ABSTRACT: Aberrant DNA methylation is a commonly observed epigenetic change in lung cancer. Folate has been suggested to play a role in the homeostasis of DNA methylation and has also been implicated in cancer chemotherapy. We investigated a possible role for folate in DNA methylation by measuring folate concentrations in tumors and adjacent normal tissues from 72 non-small cell lung cancer (NSCLC) patients. These were compared to DNA methylation levels and to clinicopathological features. Folate concentrations were determined as the sum of 5,10-methylenetetrahydrofolate and tetrahydrofolate. The MethyLight assay was used to quantitate methylation in promoter regions of P16(CDKN2A), APC, CDH13, RARB, RASSF1, RUNX3, and MYOD1. Methylation of LINE-1 repeats was used as a surrogate for global methylation. Folate levels in tumors correlated positively with LINE-1, CDH13, and RUNX3 methylation. Folate concentrations and methylation of LINE-1, RASSF1, and RUNX3 were significantly higher in adenocarcinoma compared to squamous cell carcinoma (SCC). Two sets of array-based data retrieved from the Gene Expression Omnibus consistently showed that expression of FOLR1, a folate transport enzyme, and GGH, an enzyme that prevents folate retention, were higher and lower, respectively, in adenocarcinomas compared to SCC. This was independently validated by quantitative RT-PCR in 26 adenocarcinomas and 13 SCC. Our results suggest that folate metabolism plays a role in aberrant DNA methylation in NSCLC. The histological subtype differences in folate concentration and DNA methylation observed here were associated with distinct expression patterns for folate metabolizing enzymes. These findings may have clinical applications for histology-directed chemotherapy with fluoropyrimidine and anti-folates in NSCLC. (Cancer Sci 2009l; 100: 2325–2330)
[Show abstract][Hide abstract] ABSTRACT: The major obstacles to treatment of pancreatic cancer are the highly invasive capacity and resistance to chemo- and radiotherapy. Glycogen synthase kinase 3β (GSK3β) regulates multiple cellular pathways and is implicated in various diseases including cancer. Here we investigate a pathological role for GSK3β in the invasive and treatment resistant phenotype of pancreatic cancer.
Pancreatic cancer cells were examined for GSK3β expression, phosphorylation and activity using Western blotting and in vitro kinase assay. The effects of GSK3β inhibition on cancer cell survival, proliferation, invasive ability and susceptibility to gemcitabine and radiation were examined following treatment with a pharmacological inhibitor or by RNA interference. Effects of GSK3β inhibition on cancer cell xenografts were also examined.
Pancreatic cancer cells showed higher expression and activity of GSK3β than non-neoplastic cells, which were associated with changes in its differential phosphorylation. Inhibition of GSK3β significantly reduced the proliferation and survival of cancer cells, sensitized them to gemcitabine and ionizing radiation, and attenuated their migration and invasion. These effects were associated with decreases in cyclin D1 expression and Rb phosphorylation. Inhibition of GSK3β also altered the subcellular localization of Rac1 and F-actin and the cellular microarchitecture, including lamellipodia. Coincident with these changes were the reduced secretion of matrix metalloproteinase-2 (MMP-2) and decreased phosphorylation of focal adhesion kinase (FAK). The effects of GSK3β inhibition on tumor invasion, susceptibility to gemcitabine, MMP-2 expression and FAK phosphorylation were observed in tumor xenografts.
The targeting of GSK3β represents an effective strategy to overcome the dual challenges of invasiveness and treatment resistance in pancreatic cancer.
[Show abstract][Hide abstract] ABSTRACT: Background
Long interspersed nucleotide element 1 (LINE-1) hypomethylation is suggested to play a role in the progression of colorectal cancer (CRC). To assess intra-patient heterogeneity of LINE-1 methylation in CRC and to understand its biological relevance in invasion and metastasis, we evaluated the LINE-1 methylation at multiple tumor sites. In addition, the influence of stromal cell content on the measurement of LINE-1 methylation in tumor tissue was analyzed.
Formalin-fixed paraffin-embedded primary tumor tissue was obtained from 48 CRC patients. Matched adjacent normal colon tissue, lymph node metastases and distant metastases were obtained from 12, 18 and 7 of these patients, respectively. Three different areas were microdissected from each primary tumor and included the tumor center and invasive front. Normal mucosal and stromal cells were also microdissected for comparison with the tumor cells. The microdissected samples were compared in LINE-1 methylation level measured by multicolor MethyLight assay. The assay results were also compared between microdissected and macrodissected tissue samples.
LINE-1 methylation within primary tumors showed no significant intra-tumoral heterogeneity, with the tumor center and invasive front showing identical methylation levels. Moreover, no difference in LINE-1 methylation was observed between the primary tumor and lymph node and distant metastases from the same patient. Tumor cells showed significantly less LINE-1 methylation compared to adjacent stromal and normal mucosal epithelial cells. Consequently, LINE-1 methylation was significantly lower in microdissected samples compared to macrodissected samples. A trend for less LINE-1 methylation was also observed in more advanced stages of CRC.
LINE-1 methylation shows little intra-patient tumor heterogeneity, indicating the suitability of its use for molecular diagnosis in CRC. The methylation is relatively stable during CRC progression, leading us to propose a new concept for the association between LINE-1 methylation and disease stage.
[Show abstract][Hide abstract] ABSTRACT: Inter-ethnic differences in drug handling and frequencies of pharmacogenetic variants are increasingly being characterized. In this study, we systematically assessed the feasibility of inferring ethnic trends in chemotherapy outcomes from inter-ethnic differences in pharmacogenetic variant frequencies. Frequencies of 51 variants and chemotherapy outcomes of East Asian and Caucasian colorectal cancer patients on standard chemotherapy regimens were summarized by meta-analyses, and variant frequencies were validated by MassARRAY analysis. Inferences of relative chemotherapy outcomes were made by considering minor allele function and population differences in their frequency. Significant population differences in genotype distributions were observed for 13/23 (60%) and 27/35 (77%) variants in the meta-analyses and validation series, respectively. Across chemotherapy regimens, East Asians had lower rates of grade 3/4 toxicity for diarrhea and stomatitis/mucositis than Caucasians, which was correctly inferred from 13/18 (72%, P=0.018) informative genetic variants. With appropriate variant selection, inferring relative population toxicity rates from population genotype differences may be relevant.The Pharmacogenomics Journal advance online publication, 26 June 2012; doi:10.1038/tpj.2012.26.
No preview · Article · Jun 2012 · The Pharmacogenomics Journal
[Show abstract][Hide abstract] ABSTRACT: Recent evidence has suggested that carcinoma is accompanied by the loss of cell polarity. An epithelial cell-specific form of the AP-1 clathrin adaptor complex, AP1B, is involved in the polarized transport of membrane proteins to the basolateral surface of epithelial cells. In our study, we investigated whether AP1B is involved in intestinal tumorigenesis. The cellular polarity of intestinal tumor cells was examined using APC(Min/+) mice as an in vivo model and SW480 cells with a truncating mutation in the adenomatous polyposis coli (APC) gene as an in vitro model by confocal microscopy. Next, the expression of AP1B in intestinal tumor cells was examined by real-time polymerase chain reaction (PCR) and Western blotting. The localization of β-catenin and the expression of AP1B in the tumor tissue of patients with colorectal cancer were evaluated by confocal microscopy and real-time PCR, respectively, and the relationships among cell polarity, AP1B expression and intestinal tumorigenesis were examined. Cellular polarity was lost in intestinal tumor cells, and the expression of AP1B was downregulated. In addition, the reduction in the expression level of AP1B correlated with the nuclear localization of β-catenin in human colorectal cancer. Our study indicates the close associations between AP1B, intestinal tumorigenesis and mutations in the APC gene. This is the first report to reveal the relationships among AP1B, cellular polarity and intestinal tumorigenesis, and achieving a detailed understanding of AP1B will hopefully lead to discovery of therapeutic targets and novel biomarkers for intestinal cancer.
Full-text · Article · Mar 2012 · International Journal of Cancer
[Show abstract][Hide abstract] ABSTRACT: Pancreatic cancer develops and progresses through complex, cumulative biological processes involving metabolic disorder, local inflammation, and deregulated molecular pathways. The resulting tumor aggressiveness hampers surgical intervention and renders pancreatic cancer resistant to standard chemotherapy and radiation therapy. Based on these pathologic properties, several therapeutic strategies are being developed to reverse refractory pancreatic cancer. Here, we outline molecular targeting therapies, which are primarily directed against growth factor receptor-type tyrosine kinases deregulated in tumors, but have failed to improve the survival of pancreatic cancer patients. Glycogen synthase kinase-3β (GSK3β) is a member of a serine/threonine protein kinase family that plays a critical role in various cellular pathways. GSK3β has also emerged as a mediator of pathological states, including glucose intolerance, inflammation, and various cancers (e.g., pancreatic cancer). We review recent studies that demonstrate the anti-tumor effects of GSK3β inhibition alone or in combination with chemotherapy and radiation. GSK3β inhibition may exert indirect anti-tumor actions in pancreatic cancer by modulating metabolic disorder and inflammation.
[Show abstract][Hide abstract] ABSTRACT: Pancreatic cancer is obstinate and resistant to gemcitabine, a standard chemotherapeutic agent for the disease. We previously showed a therapeutic effect of glycogen synthase kinase-3β (GSK3β) inhibition against gastrointestinal cancer and glioblastoma. Here, we investigated the effect of GSK3β inhibition on pancreatic cancer cell sensitivity to gemcitabine and the underlying molecular mechanism.
Expression, phosphorylation, and activity of GSK3β in pancreatic cancer cells (PANC-1) were examined by Western immunoblotting and in vitro kinase assay. The combined effect of gemcitabine and a GSK3β inhibitor (AR-A014418) against PANC-1 cells was examined by isobologram and PANC-1 xenografts in mice. Changes in gene expression in PANC-1 cells following GSK3β inhibition were studied by cDNA microarray and reverse transcription (RT)-PCR.
PANC-1 cells showed increased GSK3β expression, phosphorylation at tyrosine 216 (active form), and activity compared with non-neoplastic HEK293 cells. Administration of AR-A014418 at pharmacological doses attenuated proliferation of PANC-1 cells and xenografts, and significantly sensitized them to gemcitabine. Isobologram analysis determined that the combined effect was synergistic. DNA microarray analysis detected GSK3β inhibition-associated changes in gene expression in gemcitabine-treated PANC-1 cells. Among these changes, RT-PCR and Western blotting showed that expression of tumor protein 53-induced nuclear protein 1, a gene regulating cell death and DNA repair, was increased by gemcitabine treatment and substantially decreased by GSK3β inhibition.
The results indicate that GSK3β inhibition sensitizes pancreatic cancer cells to gemcitabine with altered expression of genes involved in DNA repair. This study provides insight into the molecular mechanism of gemcitabine resistance and thus a new strategy for pancreatic cancer chemotherapy.
Full-text · Article · Nov 2011 · Journal of Gastroenterology
[Show abstract][Hide abstract] ABSTRACT: Trefoil factors (TFFs) regulate mucosal repair and suppress tumor formation in the stomach. Tff1 deficiency results in gastric cancer, whereas Tff2 deficiency increases gastric inflammation. TFF2 expression is frequently lost in gastric neoplasms, but the nature of the silencing mechanism and associated impact on tumorigenesis have not been determined.
We investigated the epigenetic silencing of TFF2 in gastric biopsy specimens from individuals with Helicobacter pylori-positive gastritis, intestinal metaplasia, gastric cancer, and disease-free controls. TFF2 function and methylation were manipulated in gastric cancer cell lines. The effects of Tff2 deficiency on tumor growth were investigated in the gp130(F/F) mouse model of gastric cancer.
In human tissue samples, DNA methylation at the TFF2 promoter began at the time of H pylori infection and increased throughout gastric tumor progression. TFF2 methylation levels were inversely correlated with TFF2 messenger RNA levels and could be used to discriminate between disease-free controls, H pylori-infected, and tumor tissues. Genome demethylation restored TFF2 expression in gastric cancer cell lines, so TFF2 silencing requires methylation. In Tff2-deficient gp130(F/F)/Tff2(-/-) mice, proliferation of mucosal cells and release of T helper cell type-1 (Th-1) 1 cytokines increased, whereas expression of gastric tumor suppressor genes and Th-2 cytokines were reduced, compared with gp130(F/F)controls. The fundus of gp130(F/F)/Tff2(-/-) mice displayed glandular atrophy and metaplasia, indicating accelerated preneoplasia. Experimental H pylori infection in wild-type mice reduced antral expression of Tff2 by increased promoter methylation.
TFF2 negatively regulates preneoplastic progression and subsequent tumor development in the stomach, a role that is subverted by promoter methylation during H pylori infection.
[Show abstract][Hide abstract] ABSTRACT: Cancer cells acquire metastatic phenotypes by accumulating genetic and epigenetic abnormalities. DNA methylation is involved in epigenetic regulation of gene transcription and frequently altered with carcinogenesis. Two modes of aberrant DNA methylation, promoter hypermethylation and global hypomethylation, play a role in cancer metastasis with different mechanisms. Here, we discuss how the aberrant DNA methylation contributes to acquisition of metastatic phenotypes in cancer and review the recent trials for molecular diagnosis of cancer metastasis using methylation markers.
No preview · Article · Nov 2010 · Gan to kagaku ryoho. Cancer & chemotherapy
[Show abstract][Hide abstract] ABSTRACT: Epigenetic alterations have been correlated with field cancerization in human patients, but evidence from experimental models that specific epigenetic changes can initiate cancer has been lacking. Although hormones have been associated with cancer risk, the mechanisms have not been determined. The peptide hormone gastrin exerts a suppressive effect on antral gastric carcinogenesis.
N-methyl-N-nitrosourea (MNU)-dependent gastric cancer was investigated in hypergastrinemic (INS-GAS), gastrin-deficient (GAS(-/-)), Tff1-deficient (Tff1(+/-)), and wild-type (WT) mice. Epigenetic alterations of the trefoil factor 1 (TFF1) tumor suppressor gene were evaluated in vitro and in vivo.
Human intestinal-type gastric cancers in the antrum exhibited progressive TFF1 repression and promoter hypermethylation. Mice treated with MNU exhibited a field defect characterized by widespread Tff1 repression associated with histone H3 lysine 9 methylation and H3 deacetylation at the Tff1 promoter in epithelial cells. In MNU-induced advanced cancers, DNA methylation at the Tff1 promoter was observed. Tumor induction and Tff1 repression were increased in MNU-treated mice by Helicobacter infection. Hypergastrinemia suppressed MNU-dependent tumor initiation and progression in a manner that correlated with gene silencing and epigenetic alterations of Tff1. In contrast, homozygous gastrin-deficient and heterozygous Tff1-deficient mice showed enhanced MNU-dependent field defects and cancer initiation compared with WT mice. In gastric cancer cells, gastrin stimulation partially reversed the epigenetic silencing in the TFF1 promoter.
Initiation of antral gastric cancer is associated with progressive epigenetic silencing of TFF1, which can be suppressed by the hormone gastrin.
[Show abstract][Hide abstract] ABSTRACT: We investigated the clinical value of methylation of long interspersed nuclear element-1 (LINE-1) for the prognosis of colorectal cancer (CRC) and for the survival benefit from adjuvant chemotherapy with oral fluoropyrimidines. LINE-1 methylation in tumor DNA was measured by quantitative methylation-specific PCR in 155 samples of stage II and stage III CRC. The presence of microsatellite instability and CpG island methylator phenotype (CIMP) were assessed and 131 microsatellite stable/CIMP- cases were selected for survival analysis, of which 77 patients had received postoperative adjuvant chemotherapy with oral fluoropyrimidines. The CRC cell lines were used to investigate possible mechanistic links between LINE-1 methylation and effects of 5-fluorouracil (5-FU). High LINE-1 methylation was a marker for better prognosis in patients treated by surgery alone. Patients with low LINE-1 methylation who were treated with adjuvant chemotherapy survived longer than those treated by surgery alone, suggestive of a survival benefit from the use of oral fluoropyrimidines. In contrast, a survival benefit from chemotherapy was not observed for patients with high LINE-1 methylation. The CRC cell lines treated with 5-FU showed increased expression of LINE-1 mRNA. This was associated with upregulation of the phospho-histone H2A.X in cells with low LINE-1 methylation, but not in cells with high LINE-1 methylation. The 5-FU-mediated induction of phospho-histone H2A.X, a marker of DNA damage, was inhibited by knockdown of LINE-1. These results suggest that LINE-1 methylation is a novel predictive marker for survival benefit from adjuvant chemotherapy with oral fluoropyrimidines in CRC patients. This finding could be important for achieving personalized chemotherapy.
[Show abstract][Hide abstract] ABSTRACT: Gliomas are the most frequent malignant intracranial tumors arising from the brain or spinal cord tissue. The most malignant
among them is glioblastoma multiforme (GBM), which constitutes approximately 20–25% of all primary intracranial neoplasms
with an incidence of 3–4/100,000. This type of tumor is characterized by progressive overgrowth of neoplastic glial cells
with widespread and relentless invasion, resulting in acquisition of resistance to treatment and a poor prognosis due to recurrence.
These features hamper efficient surgical intervention of the disease. Current chemo/radiotherapy conditions act sublethally
but cannot effectively suppress the proliferation of glioma cells. Despite some progress, the therapeutic options are yet
limited, and novel therapeutic strategies are clearly needed. Targeting of disease-specific molecules involved in the proliferation,
apoptosis, and invasion of the tumor cells as well as in tumor angiogenesis may offer a high potential for the development
of more effective therapies for GBM. RNA interference (RNAi) has been emerging not only for in vitro target validation, but also for a novel therapeutic strategy based on the highly specific and efficient silencing of a target
gene. Indeed, RNAi has shown to act against GBM efficiently in numerous preclinical studies. Many efforts have been devoted
to overcome the three major obstacles in use of RNAi in vivo; their specificity, instability, and poor cellular delivery of bioactive small interfering RNA (siRNA) across the blood–brain
barrier. The identification of effective target and the establishment of novel siRNA delivery systems are needed for the clinical
applications of RNAi for treatment of GBM.
[Show abstract][Hide abstract] ABSTRACT: The Family with sequence similarity 107 (FAM107) possesses an N-terminal domain of unknown function (DUF1151) that is highly conserved beyond species. In human, FAM107A termed TU3A/DRR1 has been reported as a candidate tumor suppressor gene which expression is downregulated in several types of cancer, however no studies have investigated the other family protein, FAM107B. In the present study, we designated FAM107B as heat shock-inducible tumor small protein (HITS) and studied its expression and functional properties in cancer. HITS is an 18-kDa nuclear protein expressed in a variety of tissues including stomach, colon, lung and lymphoid organs. In human gastric and colorectal cancers and a mouse model of colon cancer, its expression in tumor cells was much lower than normal epithelial cells, while expression pattern and intensity varied among different histological types of cancer. In functional analysis in vitro, forced expression of this protein suppresses the cellular responses to growth factors. Furthermore, HITS gene carries the promoter region providing heat shock transcription factor (HSF) binding sites and amplifying the transcription of HITS by heat shock or hyperthermia treatment both in vitro and in vivo. Thus HITS would be a potential tumor suppressor gene similar to TU3A containing heat responding elements, which contrasts with previously described oncogenic activities of other heat shock proteins such as HSP70 and HSP90.
Full-text · Article · Sep 2010 · International Journal of Oncology