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J G Herman

Publications and source records attributed to J G Herman.

At least 91 records · Page 5Linked to original sources
PubMed1997

Association between CpG island methylation and microsatellite instability in colorectal cancer.

De novo methylation of promoter region CpG islands has been increasingly associated with transcriptional inactivation of important genes in neoplasia. To study the potential mechanisms underlying aberrant methylation in cancer, we have determined the methylation patterns of selected genes in colorectal cancers with and without microsatellite instability (MI), which results from defects in one of several base mismatch repair genes. A total of 47 colorectal cancers were analyzed, of which 15 were MI+ (32%). We now report that both the frequency and the extent of de novo methylation are strikingly increased in MI+ cancers. Hypermethylation of the p16 gene was found in 60% of MI+ cancers, compared to only 22% in MI- cancers (P = 0.02). Similarly, hypermethylation of the thrombospondin-1 (TSP-1) gene, an angiogenesis inhibitor, was increased in MI+ cancers (27% versus 0%; P = 0.008). Extensive methylation of insulin-like growth factor II (IGF2) and hypermethylated in cancer-1 (HIC-1) genes was observed in 60 and 80% of MI+ cancers, respectively, as contrasted with 6 and 38% of MI- cancers (P = 0.0002 and 0.01, respectively). Furthermore, 60% of the MI+ cancers displayed the hypermethylation events at two or more loci in a concordant manner compared to only 9% of the MI- cancers (P < 0.001). These results demonstrate a strong link between promoter hypermethylation and genetic instability due to deficient DNA repair.

Carrier Proteins↗
PubMed1997

Abrogation of the Rb/p16 tumor-suppressive pathway in virtually all pancreatic carcinomas.

The Rb/p16 tumor-suppressive pathway is abrogated frequently in human tumors, either through inactivation of the Rb or p16INK4a/CDKN2/MTS1 tumor-suppressor proteins, or through alteration or overexpression of the cyclin D1 or cyclin-dependent kinase 4 oncoproteins. We reported previously that the p16 gene was genetically inactivated in 82% of pancreatic carcinomas. Nearly half of these inactivations were by intragenic mutation of p16, and the remainder were by homozygous deletion of the gene. Here, we analyzed pancreatic carcinomas for additional mechanisms by which the Rb/p16 pathway might be inactivated. Transcriptional silencing of the p16 gene in association with methylation of its 5'-CpG island was examined by methylation-specific PCR in 18 pancreatic carcinomas. Nine of these were known to harbor an intragenic mutation in p16, and nine had a wild-type p16 coding sequence. Seven of the 18 tumors were hypermethylated, and all 7 were p16 wild-type (P = 0.001). Complete silencing of transcription from methylated wild-type gene sequences was demonstrated. Immunohistochemical analysis revealed normal expression levels of the Rb protein in all carcinomas studied. None of the carcinomas had genomic amplification of the cyclin D1 or CDK4 genes, and none had mutation of the p16-binding domain of CDK4. An additional p16 mutation was identified. In total, the Rb/p16 pathway was abrogated in 49 of the 50 carcinomas (98%) studied, all through inactivation of the p16 gene. Similar results were obtained in an independently analyzed series of 19 pancreatic carcinomas. These data demonstrate the central role of the Rb/p16 pathway in the development of pancreatic carcinoma.

Carrier Proteins↗
PubMed1997

Distinct patterns of inactivation of p15INK4B and p16INK4A characterize the major types of hematological malignancies.

Inactivation of the cyclin-dependent kinase inhibitors p16INK4A and p15INK4B are frequent alterations in neoplasia, often resulting from homozygous deletion or promoter region hypermethylation. We have analyzed both modes of inactivation of p15INK4B and p16INK4A in the major types of adult and pediatric hematological malignancies. Hypermethylation of p15INK4B, without alteration of p16INK4A, was an almost universal finding in adult acute myelogenous leukemia, and occurred very frequently in adult acute lymphocytic leukemia and pediatric acute myelogenous leukemia and acute lymphocytic leukemia. In contrast, neither p15INK4B nor p16INK4A were inactivated in any stage of chronic myelogenous leukemia. Hypermethylation of p16INK4A, often without alterations of p15INK4B, was found in non-Hodgkin's lymphoma and was much more frequent in cases with high-grade than low-grade histology. Enriched normal bone marrow stem cells had no detectable promoter region methylation of these genes, as analyzed by a newly developed PCR method. Remarkably distinct patterns of inactivation of p15INK4B and p16INK4A characterize different types of hematological malignancy, and alterations in these tumor suppressor genes are one of the most common alterations in hematological malignancies.

Adult↗
PubMed1997

Frequent aberrant methylation of p16INK4a in primary rat lung tumors.

The p16INK4a (p16) tumor suppressor gene is frequently inactivated by homozygous deletion or methylation of the 5' CpG island in cell lines derived from human non-small-cell lung cancers. However, the frequency of dysfunction in primary tumors appears to be significantly lower than that in cell lines. This discordance could result from the occurrence or selection of p16 dysfunction during cell culture. Alternatively, techniques commonly used to examine tumors for genetic and epigenetic alterations may not be sensitive enough to detect all dysfunctions within the heterogeneous cell population present in primary tumors. If p16 inactivation plays a central role in development of non-small-cell lung cancer, then the frequency of gene inactivation in primary tumors should parallel that observed in cell lines. The present investigation addressed this issue in primary rat lung tumors and corresponding derived cell lines. A further goal was to determine whether the aberrant p16 gene methylation seen in human tumors is a conserved event in this animal model. The rat p16 gene was cloned and sequenced, and the predicted amino acid sequence of its product found to be 62% homologous to the amino acid sequence of the human analog. Homozygous deletion accounted for loss of p16 expression in 8 of 20 cell lines, while methylation of the CpG island extending throughout exon 1 was observed in 9 of 20 cell lines. 2-Deoxy-5-azacytidine treatment of cell lines with aberrant methylation restored gene expression. The methylated phenotype seen in cell lines showed an absolute correlation with detection of methylation in primary tumors. Aberrant methylation was also detected in four of eight primary tumors in which the derived cell line contained a deletion in p16. These results substantiate the primary tumor as the origin for dysfunction of the p16 gene and implicate CpG island methylation as the major mechanism for inactivating this gene in the rat lung tumors examined. Furthermore, rat lung cancer appears to be an excellent model in which to investigate the mechanisms of de novo gene methylation and the role of p16 dysfunction in the progression of neoplasia.

Amino Acid Sequence↗
PubMed1997

DNA methylation changes in hematologic malignancies: biologic and clinical implications.

DNA methylation changes are among the most common detectable abnormalities in human neoplasia. Hypermethylation within the promoters of selected genes appears to be especially common in all types of human hematopoietic neoplasms, and is usually associated with inactivation of the involved gene(s). Such hypermethylation-associated silencing of gene expression has been shown for several genes regulating the growth and differentiation of hematopoietic cells, including the estrogen receptor (ER) gene, P15, P16 and others. Hypermethylation within the promoters of some genes appear to be an early event in the pathogenesis of neoplasia (ER, P15), while other genes seem to become methylated during the progression of leukemias (HIC1, c-abl). The high prevalence of promoter methylation suggests that this molecular abnormality can be used to monitor disease activity during therapy. In addition, new technology allows the sensitive identification of gene hypermethylation in a background of normal cells, suggesting possible new strategies for the detection of minimal residual disease. Finally, reactivation of tumor-suppressor gene expression through pharmacologic inhibition of DNA methyltransferase and resultant DNA demethylation appears to be a promising new avenue of therapy in acute leukemia.

Blood Cells↗
PubMed1997

Deletional, mutational, and methylation analyses of CDKN2 (p16/MTS1) in primary and metastatic prostate cancer.

The tumor suppressor gene CDKN2 (p16/MTS1) resides on chromosome 9p21 and encodes a 16 kDa inhibitor of the cyclin-dependent kinases. Inactivation of CDKN2 by homozygous deletion, point mutation, and recently described aberrant methylation in the 5' promoter region may increase progression through the cell cycle in tumors. In this study, we examine the CDKN2 gene for the presence of inactivating alterations in human prostate cancer. Sequence analysis of cell lines revealed no mutation in LNCaP, PC3, and TSU-PR1 and a missense mutation, GAC-->TAC (asp to tyr), in exon 2 of the DU145 cell line at codon 76. No mutations were identified in three primary prostate cancers or in seven lymph node metastases. Loss of heterozygosity (LOH) was analyzed by analysis of microsatellite markers in the vicinity of the CDKN2 gene. LOH was detected in 12 (20%) of 60 primary tumors at one or more loci and in 13 (46%) of 28 metastases. Methylation analysis of the CpG-rich promoter region revealed a dense methylation of CDKN2 in cell lines PC3, PPC1, and TSU-PR1, and this was found to correlate with a lack of mRNA expression by reverse transcription-polymerase chain reaction. A demethylating agent, 5-aza-2'-deoxycytidine, induced reexpression when cells were exposed in vitro. DU145 and LNCaP expressed the CDKN2 transcript and were unmethylated in the promoter region. Three of twenty-four (13%) primary prostate cancers and 1 of 12 metastatic tumors demonstrated promoter methylation. No normal prostate tissues were methylated at the CDKN2 gene promoter. One tumor was found to contain concomitant LOH and promoter methylation indicative of biallelic inactivation. A comprehensive analysis of CDKN2 in prostate cancer reveals that point mutations are infrequent, but gene deletion and methylation combine to inactivate CDKN2 in a subset of tumors. Moreover, alterations in this gene may represent a late event in prostate cancer progression.

Aged↗
PubMed1996

Methylation-specific PCR: a novel PCR assay for methylation status of CpG islands.

Precise mapping of DNA methylation patterns in CpG islands has become essential for understanding diverse biological processes such as the regulation of imprinted genes, X chromosome inactivation, and tumor suppressor gene silencing in human cancer. We describe a new method, MSP (methylation-specific PCR), which can rapidly assess the methylation status of virtually any group of CpG sites within a CpG island, independent of the use of methylation-sensitive restriction enzymes. This assay entails initial modification of DNA by sodium bisulfite, converting all unmethylated, but not methylated, cytosines to uracil, and subsequent amplification with primers specific for methylated versus unmethylated DNA. MSP requires only small quantities of DNA, is sensitive to 0.1% methylated alleles of a given CpG island locus, and can be performed on DNA extracted from paraffin-embedded samples. MSP eliminates the false positive results inherent to previous PCR-based approaches which relied on differential restriction enzyme cleavage to distinguish methylated from unmethylated DNA. In this study, we demonstrate the use of MSP to identify promoter region hypermethylation changes associated with transcriptional inactivation in four important tumor suppressor genes (p16, p15, E-cadherin, and von Hippel-Lindau) in human cancer.

Antisense Elements (Genetics)↗
PubMed1996

Hypermethylation-associated inactivation indicates a tumor suppressor role for p15INK4B.

The recently identified cyclin-dependent kinase inhibitor p15INK4B is localized to a region on chromosome 9p21 frequently deleted in human tumors. Previous evidence has pointed to a related gene, p16INK4A, as the principal target of this deletion. We report that in gliomas and, to a striking degree, in leukemias, the p15 gene is commonly inactivated in association with promoter region hypermethylation involving multiple sites in a 5'-CpG island. In some gliomas and all of the primary leukemias, this event occurs without alteration of the adjacent gene, p16INK4A. In other tumors, including lung, head and neck, breast, prostate, and colon cancer, inactivation of p15INK4B occurs only rarely and only with concomitant inactivation of p16. Aberrant methylation of p15INK4B is associated with transcriptional loss of this gene. Treatment with the demethylating agent 5-aza-2'-deoxycytidine leads to re-expression of p15 mRNA. In selected leukemia cell lines, p15 inactivation correlates with known resistance to the growth-suppressive effects of transforming growth factor-beta. These results suggest that p15INK4B is inactivated selectively in leukemias and gliomas and seems to constitute an important tumor suppressor gene loss in these neoplasms.

Adult↗
PubMed1996

Expression of prokaryotic HhaI DNA methyltransferase is transforming and lethal to NIH 3T3 cells.

In neoplastic cells, levels of DNA methyltransferase activity are often increased, and evidence is accruing to suggest an important role for this event in tumorigenesis. To evaluate this possibility further, and to investigate the contribution of increasing de novo, as opposed to maintenance, DNA methylation in mammalian cells, we expressed the bacterial HhaI methyltransferase in cultured murine fibroblasts. This enzyme is a pure de novo DNA methyltransferase that methylates the internal C in the sequence GCGC. We find that both constitutive and induced expression of the wild-type HhaI results, primarily, in lethality to the cells. However, surviving cell clones that express low levels of M. HhaI demonstrate increased tumorigenicity as assessed by soft agar cloning efficiency (8.6% for sense HhaI-transduced PA 317 cells versus 0.4% for antisense controls; 1.7% for sense HhaI-transfected NIH 3T3 cells versus 0% for a mutant HhaI control) and tumorigenicity in nude mouse heterotransplants (75% for sense HhaI-transduced PA 317 cells versus 18.5% for antisense controls). DNA isolated from the clonogenic sense HhaI clones, versus clones expressing the mutant HhaI gene, has no increase in overall CpG methylation but an average of 27% (range, 16.7-38.9) increase in methylcytosine content at GCGC sites. These findings suggest that eukaryotic cells tolerate a narrow window of increase de novo DNA methylating capacity, above which cell death occurs and within cell transformation results. Our results further emphasize the potential role of increased DNA methyltransferase activity in the evolution of cancer.

3T3 Cells↗
PubMed1995

E-cadherin expression is silenced by DNA hypermethylation in human breast and prostate carcinomas.

Expression of the Ca(2+)-dependent, homotypic cell:cell adhesion molecule, E-cadherin (E-cad), suppresses tumor cell invasion and metastasis in experimental tumor models. Decreased E-cad expression is common in poorly differentiated, advanced-stage carcinomas. These data implicate E-cad as an "invasion suppressor" gene. The mechanism by which E-cad is silenced in advanced stage carcinomas is unclear. In this report, we show that: (a) the 5' CpG island of E-cad is densely methylated in E-cad-negative breast and prostate carcinoma cell lines and primary breast carcinoma tissue but is unmethylated in normal breast tissue; (b) treatment with the demethylating agent, 5-aza-2'-deoxycytidine, partially restores E-cad RNA and protein levels in E-cad-negative breast and prostate carcinoma cell lines; and (c) and E-cad promoter/CAT construct is expressed in both E-cad-positive and -negative breast and prostate carcinoma cell lines, indicating that these cells have the active transcriptional machinery necessary for E-cad expression. Our data demonstrate that frequent loss of E-cad expression in human breast and prostate carcinomas results from hypermethylation of the E-cad promoter region.

Base Sequence↗
PubMed1995

Inactivation of the CDKN2/p16/MTS1 gene is frequently associated with aberrant DNA methylation in all common human cancers.

The tumor suppressor gene CDKN2/p16/MTS1, located on chromosome 9p21, is frequently inactivated in many human cancers through homozygous deletion. Recently, we have reported another pathway of inactivation that involves loss of transcription associated with de novo methylation of a 5' CpG island of CDKN2/p16 in lung cancers, gliomas, and head and neck squamous cell carcinomas. We now show that this aberrant CpG island methylation also occurs frequently in cell lines of breast cancer (33%), prostate cancer (60%), renal cancer (23%), and colon cancer (92%) and is associated with loss of transcription. Primary tumors of the breast (31%) and colon (40%) also displayed de novo methylation of this CpG island. This alteration of p16 in colon cancer was particularly striking, since inactivation does not occur through homozygous deletion in this tumor type. Our data show that in tumors, de novo methylation of the 5' CpG island is a frequent mode of inactivation of CDKN2/p16 and also firmly demonstrate that CDKN2/p16 is one of the most frequently altered genes in human neoplasia.

Carrier Proteins↗
PubMed1995

5' CpG island methylation is associated with transcriptional silencing of the tumour suppressor p16/CDKN2/MTS1 in human cancers.

Loss of heterozygosity on chromosome 9p21 is one of the most frequent genetic alterations identified in human cancer. The rate of point mutations of p16, a candidate suppressor gene of this area, is low in most primary tumours with allelic loss of 9p21. Monosomic cell lines with structurally unaltered p16 show methylation of the 5' CpG island of p16. This distinct methylation pattern was associated with a complete transcriptional block that was reversible upon treatment with 5-deoxyazacytidine. Moreover, de novo methylation of the 5' CpG island of p16 was also found in approximately 20% of different primary neoplasms, but not in normal tissues, potentially representing a common pathway of tumour suppressor gene inactivation in human cancers.

5-Methylcytosine↗
PubMed1994

Silencing of the VHL tumor-suppressor gene by DNA methylation in renal carcinoma.

Mutational inactivation and allelic loss of the von Hippel-Lindau (VHL) gene appear to be causal events for the majority of spontaneous clear-cell renal carcinomas. We now show that hypermethylation of a normally unmethylated CpG island in the 5' region provides another potentially important mechanism for inactivation of the VHL gene in a significant portion of these cancers. This hypermethylation was found in 5 of 26 (19%) tumors examined. Four of these had lost one copy of VHL while one retained two heavily methylated alleles. Four of the tumors with VHL hypermethylation had no detectable mutations, whereas one had a missense mutation in addition to hypermethylation of the single retained allele. As would be predicted for the consequence of methylation in this 5' CpG island, none of the 5 tumors expressed the VHL gene. In contrast, normal kidney and all tumors examined with inactivating VHL gene mutations but no CpG island methylation had expression. In a renal cell culture line, treatment with 5-aza-2'-deoxycytidine resulted in reexpression of the VHL gene. These findings suggest that aberrant methylation of CpG islands may participate in the tumor-suppressor gene inactivations which initiate or cause progression of common human cancers.

Adenocarcinoma, Clear Cell↗
PubMed1989

Radical radiotherapy for muscle invasive transitional cell carcinoma of the bladder: failure analysis.

Patients with muscle invasive carcinoma of the bladder treated with radical radiation were prospectively documented and followed in an attempt to identify prognostic factors predictive of the response to treatment. Data on 121 consecutive patients treated with radical radiation between 1981 and 1985 are presented. Over-all actuarial survival of the patient population (median age 70 years) was 31.6% at 5 years and cause-specific survival was 44.8%. At analysis 33 of 121 patients (27.3%) were alive with preserved bladder function. Independent prognostic factors for cause-specific survival and for complete response with radical radiation were tumor configuration, hemoglobin level and clinical stage. The rate free of local relapse was significantly influenced by stage and presence of coexistent carcinoma in situ. The study suggests that factors other than stage and grade influence prognosis in invasive bladder cancer and should be considered in interpreting treatment results.

Adult↗
PubMed1988

Pseudo-graft-versus-host disease in heart and heart-lung recipients.

Autopsies from nine patients who had received a cardiac allograft transplant and one with a combined heart-lung transplant were assessed for histologic evidence of pseudo-graft-versus-host disease (pseudo-GVHD). Five of the ten patients had GVHD-like changes in two or more tissues, including prominent lymphocyte-associated bile duct injury consistent with marked hepatic pseudo-GVHD and mild cutaneous changes resembling GVHD. A sixth recipient had marked changes in the liver, but autopsy restrictions prevented examination of the skin. A seventh recipient had only mild pseudo-GVHD changes limited to the skin. In contrast, a series of six patients who were candidates for cardiac transplant had no specific pathologic changes suggesting pseudo-GVHD. The majority of those with pseudo-GVHD had received nonirradiated blood product transfusions, raising the possibility of posttransfusion engraftment and GVHD. Unlike the posttransfusion GVHD, however, two of the six developed GVHD-related complications late with a latent period of five and 9.5 months, and two recipients received no transfusions. All were receiving only modest doses of immunosuppressive agents at the time they developed liver function abnormalities, including low or tapering doses of cyclosporine (CsA). In some of these recipients, therefore, the pseudo-GVHD changes may well represent an autoimmune reaction resembling the post-CsA model of autoimmune disease.

Adult↗
PubMed1987

Keeping a hold of hard copy.

Laser image recorders, daylight film processors, and "filmless" radiography system" are already found in many major medical centers, but radiologists and manufacturers believe that the technology is still in its infancy and that the best is yet to come.

Lasers↗
PubMed1985

Autocatalytic oxidation of hemoglobin induced by nitrite: activation and chemical inhibition.

The nitrite ion is a direct causative agent for methemoglobinemia. Oxidation of hemoglobin to methemoglobin under aerobic conditions is induced by nitrite, catalyzed by methemoglobin in the presence of hydrogen peroxide, and inhibited by chemical reagents ranging from cysteine and ascorbic acid to sulfite. The stoichiometry of nitrate production is dependent on the initial [NO2-]/[HbO2] ratio, but reaches a limiting value of 1:1 [NO3-]: [Hb+] when [NO2-]/[HbO2] greater than 8. Ascorbic acid is an exceptionally effective inhibitor for the autocatalytic oxidation, but its use does not affect the stoichiometry of nitrate formation. Sulfite reduces nitrate production to a level that is half that observed in its absence. These chemical inhibitors act upon the rapid autocatalytic stage for hemoglobin oxidation, but they do not influence the slow direct oxidation of hemoglobin by nitrite. The autocatalytic stage for hemoglobin oxidation results from nitrogen dioxide formed from nitrite through the peroxidase activity of methemoglobin. Peroxide and methemoglobin are formed during the initiation stage by electron transfer from nitrite that is kinetically first order in oxyhemoglobin and in nitrite.

Ascorbic Acid↗