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C Richard Boland

Publications and source records attributed to C Richard Boland.

At least 19 recordsLinked to original sources
PubMed2006

Structure and function of the components of the human DNA mismatch repair system.

DNA mismatch repair (MMR) is one of the several enzyme systems involved in DNA homeostasis. DNA MMR is involved in the repair of specific types of errors that occur during new DNA synthesis; loss of this system leads to an accelerated accumulation of potential mutations, and predisposes to certain types of cancers. Germline mutations in some of the DNA MMR genes cause the hereditary cancer predisposition, Lynch syndrome. This review addresses advances in the biochemistry of DNA MMR and its relationship to carcinogenesis.

Animals↗
PubMed2006

The CpG island methylator phenotype and chromosomal instability are inversely correlated in sporadic colorectal cancer.

BACKGROUND & AIMS: The CpG island methylator phenotype (CIMP) is one of the mechanisms involved in colorectal carcinogenesis (CRC). Although CIMP is probably the cause of high-frequency microsatellite instability (MSI-H) sporadic CRCs, its role in microsatellite stable (MSS) tumors is debated. The majority of MSS CRCs demonstrate chromosomal instability (CIN) with frequent loss of heterozygosity (LOH) at key tumor suppressor genes. We hypothesized that the majority of sporadic CRCs without CIN would be associated with CIMP. METHODS: We tested 126 sporadic CRCs for MSI and LOH and categorized tumors into MSI, LOH, or MSI-/LOH- subgroups. Methylation status was evaluated using 6 CIMP-related markers (MINT1, MINT2, MINT31, p16(INK4alpha), p14(ARF), and hMLH1) and 6 tumor suppressor genes (PTEN, TIMP3, RUNX3, HIC1, APC, and RARbeta2). BRAF V600E mutation analysis was performed using allele-specific polymerase chain reaction and DNA sequencing. RESULTS: We observed frequent methylation at all 12 loci in all CRCs. BRAF V600E mutations correlated with the MSI (P < .0001) and MSI-/LOH- (P = .03) subgroups. MSI and MSI-/LOH- tumors exhibited more promoter methylation than CRCs with LOH (P < .0001). We also found an inverse correlation between the frequencies of methylation and LOH (rho = -0.36; P < .0001). CONCLUSIONS: The associations between methylation frequencies at CIMP-related markers and MSI or MSI-/LOH- sporadic CRCs suggest that the majority of these tumors evolve through CIMP. These findings suggest that CIN and CIMP represent 2 independent and inversely related mechanisms of genetic and epigenetic instability in sporadic CRCs and confirm that MSI cancers arise as a consequence of CIMP.

Adult↗
PubMed2006

Oncogenic T-antigen of JC virus is present frequently in human gastric cancers.

BACKGROUND: JC virus (JCV) is a polyomavirus that commonly infects humans and is the causative agent of progressive multifocal leukoencephalopathy in immune-compromised patients. An association between JCV and human cancers long has been suspected, because this virus induces brain tumors in several animal models. The oncogenic potential of JCV is mediated by a transforming protein, the T-antigen (T-Ag), which is a multifunctional protein that transforms cells through interactions with various growth-regulatory genes, including p53 and pRb, and by stabilizing beta-catenin. Previously, the laboratory at the authors' institution demonstrated that JCV is present frequently in the human gastrointestinal tract and may play a role in colorectal carcinogenesis. However, to date, no studies have determined whether JCV sequences are present specifically in gastric cancers. The current study was designed to investigate whether JCV sequences and expression are found in human gastric cancers. METHODS: DNA was extracted from 23 paraffin embedded and 14 frozen gastric cancer specimens. For the detection of JCV gene sequences, polymerase chain reaction amplifications were performed using gene-specific primers for T-Ag, VP-1 (a JCV capsid gene), and the viral regulatory region (or transcriptional control region). Immunohistochemical staining was performed with an anti-T-Ag monoclonal antibody to detect protein expression. RESULTS: Twenty-one of 37 gastric cancers (57%) harbored JCV T-Ag sequences, and 13 of 37 gastric cancers (30%) contained VP-1 sequences. T-Ag sequences also were found in adjacent nonneoplastic mucosa. In addition, JCV regulatory region sequences were present frequently in gastric cancers and adjacent nonneoplastic mucosa. T-Ag protein expression was found in 9 of 23 gastric cancers (39%), whereas no expression was observed in any of the nonneoplastic tissues. CONCLUSIONS: To the authors' knowledge, this is the first demonstration of the presence of JCV T-Ag expression in human gastric cancers. These findings suggest a possible role for this polyomavirus in gastric carcinogenesis.

Antigens, Polyomavirus Transforming↗
PubMed2006

Selenomethionine induces p53 mediated cell cycle arrest and apoptosis in human colon cancer cells.

While there is an increasing interest in selenium chemoprevention against human colon polyp recurrence and other cancers, the mechanism(s) by which these agents inhibit carcinogenesis are uncertain. Some of the proposed mechanisms include the inhibition of cytosine methyltransferases, carcinogen bioactivation, and inhibition of cyclooxygenase (COX). More recently, it has been suggested that selenium may exert growth inhibitory effects by activating p53. However, the molecular mechanisms of action of selenomethionine, an organoselenium compound present in selenized yeast and currently being investigated in human clinical trials for colon polyp prevention, are unclear. In the present study we tested the hypothesis that selenomethionine might affect colon cancer cell growth by p53 mediated apoptosis and/or cell cycle regulation. Four human colon cancer cell lines including HCT116 and RKO (wild type p53), HCT116-p53KO (isogenic control of HCT116 cells with p53 knocked out) and Caco-2 (mutant p53) were treated with 0-100 microM of selenomethionine for 24, 48 and 72 h. Cell viability rates were determined by the MTT assay. Cell cycle analysis was performed by flow cytometry and apoptosis measured by Annexin V-Cy5 staining. Expression of p53 protein was determined by Western blotting and immunofluorescence assays. All cell lines showed concentration and time dependent growth inhibition with selenomethionine, although HCT116 and RKO cells were the most sensitive to such treatments. Interestingly, although HCT116 and HCT116-p53KO are isogenic cell lines, selenomethionine caused a G2/M cell cycle arrest in HCT116 and RKO cells, but not in HCT116-p53KO cells. Similarly, both HCT116 and RKO demonstrated a significant increase in apoptosis (100-170%; p < 0.01) with 50-100 microM selenomethionine. Cell cycle arrest and apoptosis observed in HCT116 and RKO cell lines were accompanied by a marked increase in p53 protein expression following selenium treatment. These results clearly suggest that selenomethionine exerts p53 dependent growth inhibitory effects in colon cancer cells by inducing G2/M cell cycle arrest as well as apoptosis.

Apoptosis↗
PubMed2006

Phenotypic and genotypic heterogeneity in the Lynch syndrome: diagnostic, surveillance and management implications.

Lynch syndrome is the most common form of hereditary colorectal cancer (CRC). This review covers the cardinal features of Lynch syndrome with particular emphasis upon its diagnostic criteria, molecular genetics, natural history, genetic counseling, surveillance and management. Considerable attention has been given to the etiologic role of mismatch repair (MMR) genes as well as low penetrance alleles and modifier genes. The American founder mutation, a deletion of exons 1-6 of MSH2, is discussed in some detail, owing to its high frequency in the US (19 000-30 000 carriers). Genetic counseling is essential prior to patients' undergoing DNA testing and again when receiving their test results. Families with a lower incidence of CRC and extracolonic cancers, in the face of being positive for Amsterdam I criteria but who do not have MMR deficiency by tumor testing, are probably not Lynch syndrome, and thereby should preferably be designated as familial CRC of undetermined type. Patients who are either noncompliant or poorly compliant with colonoscopy, and who are MMR mutation positive, may be candidates for prophylactic colectomy, while MMR mutation-positive women who are noncompliant with gynecologic surveillance may be candidates for prophylactic hysterectomy and bilateral salpingo-oophorectomy.

Colorectal Neoplasms, Hereditary Nonpolyposis↗
PubMed2006

Association of JC virus T-antigen expression with the methylator phenotype in sporadic colorectal cancers.

BACKGROUND & AIMS: JC virus (JCV) is a polyomavirus that ubiquitously infects humans and has been implicated in various human cancers. JCV encodes a "transforming" gene, T-antigen (T-Ag), which is believed to mediate the oncogenic potential of the virus. We have previously shown that JCV DNA sequences are usually present in human colorectal cancers (CRCs), and we have provided in vitro evidence that JCV can induce chromosomal instability (CIN) in CRC cells. This study tests the hypothesis that JCV T-Ag expression correlates with one or more forms of genomic or epigenetic instability in sporadic CRCs. METHODS: We characterized 100 sporadic CRCs for microsatellite instability (MSI) and CIN. PCR amplifications were performed for T-Ag sequences, and immunohistochemical (IHC) staining was performed to detect T-Ag expression. De novo methylation of the promoter regions of nine putative tumor suppressor genes thought to play a role in colorectal carcinogenesis was studied by methylation-specific PCR. RESULTS: JCV T-Ag DNA sequences were found in 77% of the CRCs and 56% of these cancers (or 43% of the total) expressed T-Ag by IHC. Significant associations were observed between T-Ag expression and CIN in CRCs (P = .017) and between T-Ag expression and promoter methylation of multiple genes (P = .01). CONCLUSIONS: The association between T-Ag expression and promoter methylation in CRC suggests that this viral oncogene may induce methylator phenotype and that JCV may be involved in CRC through multiple mechanisms of genetic and epigenetic instability.

Analysis of Variance↗
PubMed2005

Molecular pathogenesis of colorectal cancer: implications for molecular diagnosis.

Colorectal cancer is the third leading cause of cancer-related death in both men and woman in industrialized countries. Major advances have been made in our understanding of molecular events leading to formation of adenomatous polyps and cancer. Most colorectal cancers are sporadic, but a significant proportion (5-6%) has a clear genetic background. It is now widely accepted that colorectal carcinogenesis is a multistep process involving the inactivation of a variety of tumor-suppressor and DNA-repair genes and simultaneous activation of certain oncogenes. In addition, epigenetic alterations through aberrant promoter methylation and histone modification have been found to play a major role in the evolution and progression of a large proportion of sporadic colon cancers. Consequently, it is now apparent that individual colorectal cancers may evolve through diverse molecular pathways. In this article, the authors have summarized the current knowledge of molecular pathogenesis in common hereditary syndromes and sporadic forms of colorectal cancer. Novel molecular diagnostic tools for the early diagnosis and prevention of colorectal cancer that have emerged from these insights are discussed.

Colorectal Neoplasms↗
PubMed2005

Clinicopathological features and microsatellite instability (MSI) in colorectal cancers from African Americans.

African Americans (AAs) have a 1.5 times higher risk of colorectal carcinoma (CRC) than Caucasians. Gene silencing through CpG island hypermethylation has been associated with the genesis or progression of microsatellite instability (MSI) largely due to 1 target for hypermethylation being the DNA mismatch repair gene hMLH1; there is anecdotal evidence of an increased incidence of MSI among AAs. P16 and hMLH1 can be inactivated by hypermethylation of their respective promoter regions, abrogating the ability to regulate cell proliferation and repair processes. We studied such methylation, as well as hMHS2 expression in colorectal cancers from AA patients to determine if MSI is associated with epigenetic silencing. Experiments were conducted on matched normal and colon cancer tissues from AA patients (n = 51). A total of 5 microsatellite markers (D2S123, D5S346, D17S250, BAT25 and BAT26) were used to evaluate MSI status. P16 and hMLH1 promoter methylation status was determined following bisulfite modification of DNA and using methylation specific PCR, while immunohistochemistry (IHC) was used to examine expression of hMLH1 and hMSH2. A total of 22 (43%) cancers demonstrated microsatellite instability-high (MSI-H), while 27 were microsatellite stable (MSS) and 2 were microsatellite instability-low (MSH-L). Most of the MSI-H tumors were proximal, well differentiated and highly mucinous. Most patients in the MSI-H group were females (68%). The p16 promoter was methylated in 19 of 47 (40%) tumors. A total of 7 of these CRCs demonstrated MSI-H (33%). The hMLH1 promoter was methylated in 29 of 34 (85%) tumors, of which 13 CRCs demonstrated MSI-H (87%). hMLH1 and hMSH2 staining was observed in 66% and 38% of MSI-H tumors, respectively. Overall, the prevalence of MSI-H colorectal tumor was 2-3-fold higher, while the defect in the percentage expression of mismatch repair (MMR) genes (hMLH1 and hMSH2) was similar in AA patients compared to the U.S. Caucasian population. Similar numbers of AA MSS tumors with p16 and hMLH1 methylation likely indicate hemimethylation of genes that might reflect environmental or genetic influences that might be more common in the AA population.

Adaptor Proteins, Signal Transducing↗
PubMed2005

Mesalazine improves replication fidelity in cultured colorectal cells.

Epidemiologic studies indicate that mesalazine has chemopreventive effects in inflammatory bowel disease-associated colorectal cancer. Most of our general understanding of chemoprevention in colorectal cancer is, however, derived from aspirin, which is structurally similar to mesalazine. Herein we determined the influence of aspirin and mesalazine on replication fidelity in cultured colorectal cells. Flow cytometry was used for quantitation of mutation rates at a (CA)13 microsatellite in HCT116 cells (mismatch repair deficient) and HCT116+chr3 cells (mismatch repair proficient) that had been stably transfected with pIREShyg2-EGFP/CA13, an enhanced green fluorescence protein-based plasmid, and cultured in the absence or presence of various concentrations of aspirin or mesalazine. Aspirin at doses above 1.25 mmol/L markedly reduced cell growth. Mesalazine doses up to 5.0 mmol/L had no such effect. The mutation rate in mismatch repair-deficient HCT116 cells was 6.8 x 10(-4) +/- 9.0 x 10(-5). In aspirin-treated cultures the mutation rate was 8.2 x 10(-4) +/- 1.3 x 10(-4) (121% of control). Instead, mesalazine lowered the mutation rate in a dose-dependent fashion (5.5 x 10(-4) +/- 1.1 x 10(-4); 81% of control). The effects of mesalazine were most significant in the M1 fraction (P < 0.0001), which represents a mutant population immediate after the polymerase error and were confirmed in mismatch repair-proficient HCT116+chr3 cells. Our data indicate that mesalazine reduces frameshift mutations at a (CA)13 microsatellite in cultured colorectal cells independent of mismatch repair proficiency. This finding suggests that mesalazine improves replication fidelity, an effect that may be active in reducing mutations independent of its anti-inflammatory properties.

Aspirin↗
PubMed2005

Evolution of the nomenclature for the hereditary colorectal cancer syndromes.

The hereditary forms of colorectal cancer have been given many names historically as the manifestations have been gradually understood. Lynch syndrome has had several names, most prominently 'Hereditary Nonpolyposis Colorectal Cancer' or HNPCC. Clarification of the genetic basis and full phenotypic expression of this disease mandates a more clinically useful name that clarifies the consideration of non-colonic cancers in a family history, and unifies the diagnosis around the germline mutation in a DNA mismatch repair (MMR) gene. The term 'Lynch syndrome' is proposed for the autosomal dominant disease caused by a germline mutation in a DNA MMR gene.

Colorectal Neoplasms, Hereditary Nonpolyposis↗
PubMed2005

Lynch syndrome (hereditary non-polyposis colorectal cancer): current concepts and approaches to management.

Colorectal cancer is among the most frequent causes of cancer death worldwide. An inherited predisposition to cancer of the colon and other organs, Lynch syndrome-- also called hereditary non-polyposis colorectal cancer--is probably the most frequent cause of hereditary cancer and is often found in a colon cancer patient and traced through other family members. However, this syndrome is not only characterized by the early onset of colon cancers but also by a predisposition to a constellation of extraintestinal cancers that tend to be misdiagnosed. With new diagnostic technologies, the incidence of familial/inherited versus sporadic cases may appear to increase, due to the recognition of cancers in families that do not fulfill clinical guidelines developed prior to knowledge of the genetic basis of this disease. We now have the ability and the responsibility to detect and prevent this disease, and equally important, to direct patients to specifically targeted treatment. Specialists should be aware of the significance of inherited colon cancer and should become familiar with the molecular diagnostic tests now widely available.

Antineoplastic Agents↗
PubMed2005

Surveillance of patients at high risk for colorectal cancer.

Colorectal cancer (CRC) mortality may be greatly reduced by clinically feasible screening programs. The benefits of surveillance of high-risk programs are evident. Cancer mortality can be dramatically reduced by eradication of precursor lesions and by detection of cancer at an early and highly curable stage. Available screening methods, recommended intervals, and screening for other associated cancers are reviewed for specific high-risk groups.

Colorectal Neoplasms↗
PubMed2005

Somatic evolution of cancer cells.

Cancers develop through a process called genomic instability, which generates diversity, from which clonal evolution may occur. In colorectal cancers, this process has been extensively studied, and there are three identifiable processes involved in generating diversity at the genetic or epigenetic level. Colorectal cancers may have chromosomal instability (CIN), microsatellite instability (MSI), or the CpG island methylator phenotype (CIMP). Each of these processes is associated with a unique mutational or epigenetic "signature" identifiable in the tumor cells, and there are important conceptual and clinical implications of each.

Adenoma↗