Search PubMed⌕ Search

Biomedical subjects

S E Kern

Publications and source records attributed to S E Kern.

At least 109 records · Page 6Linked to original sources
PubMed1995

p53-independent expression of the cyclin-dependent kinase inhibitor p21 in pancreatic carcinoma.

The p53 tumor suppressor gene is mutated in the majority of pancreatic adenocarcinomas, and several studies have suggested that loss of p53 function may contribute to the aggressive clinical behavior of pancreas cancer. Although immunocytochemical accumulation of the p53 gene product has previously been assessed as a marker for p53 mutations in cancers of the pancreas and other organ systems, the relationship between p53 mutations and p53 protein accumulation is variable. The cyclin-dependent kinase inhibitor, p21 (also known as WAF1 and CIP1), is induced by wild-type but not mutant p53, and recent work has implicated p21 as a downstream mediator of the growth-suppressing and apoptosis-promoting functions of wild-type p53. In the present work, we sought to determine whether loss of p21 expression could more precisely identify those tumors with p53 mutations and/or loss, compared with immunocytochemical assessment of p53 protein accumulation. We evaluated p53 and p21 expression immunohistochemically in a series of 21 ductal adenocarcinomas of the pancreas with known p53 mutational status. Diffuse overexpression of p53 was found in 3 of 8 cases (38%) with wild-type p53 and 7 of 13 cases (54%) with p53 mutations with or without loss of heterozygosity at 17p. Surprisingly, expression of p21 correlated neither with p53 mutational status nor with p53 protein expression. In particular, strong p21 expression was seen even in carcinomas in which molecular analysis revealed a frameshift mutation in one allele of p53 and loss of the second. These data suggest that p21 expression in pancreatic adenocarcinoma may also be induced by a p53-independent pathway and that p21 expression, as assessed immunocytochemically, does not reflect the functional status of p53 in these carcinomas.

Adenocarcinoma↗
PubMed1994

Detection of K-ras mutations in the stool of patients with pancreatic adenocarcinoma and pancreatic ductal hyperplasia.

Pancreatic adenocarcinoma is the fifth leading cause of cancer death in the United States. Mutations in the K-ras oncogene occur in 85% of pancreatic adenocarcinomas and have also been identified in 75% of pancreatic ducts with mucinous cell hyperplasia seen in association with chronic pancreatitis. We identified K-ras mutations in 65% of duct lesions associated not only with chronic pancreatitis but also with pancreatic adenocarcinoma and distal common bile duct carcinoma (cholangiocarcinoma). These observations make K-ras a potential candidate for a gene-based diagnostic test. Indeed, K-ras mutations have been demonstrated in the pancreatic secretions of patients with pancreatic carcinoma and pancreatic intraductal neoplasia. We analyzed stool specimens for mutated K-ras sequences using a plaque hybridization assay in patients with pancreatic adenocarcinoma, cholangiocarcinoma, and chronic pancreatitis. K-ras mutations were detected in stool specimens from 6 of 11 patients with pancreatic adenocarcinoma, from 2 of 3 patients with cholangiocarcinoma, and from 1 of 3 patients with chronic pancreatitis. The K-ras mutations found in stool specimens from patients with pancreatic carcinoma were identical to those in the primary cancer in five cases. Mutations found in the stool specimens from one patient with pancreatic cancer, one patient with chronic pancreatitis, and two patients with cholangiocarcinoma were the same as those identified in pancreatic ductal mucinous cell hyperplasia lesions present in the resected pancreas specimens. Our data suggest that the K-ras mutations originating from cells of pancreatic adenocarcinomas and from cells shed by abnormal pancreatic duct epithelium can be detected in the stool. These results support the further exploration of stool K-ras analysis as a potential screening assay for the early detection of pancreatic adenocarcinoma and precursor lesions such as pancreatic ductal mucinous cell hyperplasia.

Acute Disease↗
PubMed1994

p53 mutations in pancreatic carcinoma and evidence of common involvement of homocopolymer tracts in DNA microdeletions.

Pancreatic adenocarcinoma is a major cause of cancer death, and yet little is known about its molecular pathogenesis. We identified p53 mutations in 19 (70%) of 27 primary pancreatic adenocarcinomas. Most were missense point mutations, and the mutations were distributed primarily within the evolutionarily conserved domains. Transitions predominated over transversions, and many of the transitions were at CpG dinucleotides. Intragenic deletions accounted for 32% of mutations and were associated with decreased survival (P = 0.0016). A review of 1937 published p53 mutations revealed that the occurrence of small (1-2 base pairs) microdeletions varied among different types of human neoplasms and that pancreatic adenocarcinoma had one of the highest frequencies (13% of 47 mutations, P = 0.0036). Many small deletions occurred in iterations of single bases, but this did not fully account for their pattern of distribution, and there was evidence for the involvement of homocopolymer (polypurine:polypyrimidine) tracts. This may represent a more widespread phenomenon, because microdeletions occur in similar sequence patterns in reports of somatic and germ line mutations among genes other than p53.

Adenocarcinoma↗
PubMed1994

Allelotype of pancreatic adenocarcinoma.

Knowledge of the patterns of allelic loss has been useful in identifying the spectrum of the tumor suppressor genes involved in various tumor types. Such analyses in pancreatic carcinoma have been difficult due to the characteristic host desmoplastic reaction to the neoplasm. We have assembled the first allelotype of pancreatic adenocarcinoma, a survey for allelic loss among each chromosomal arm, using seven cryostat-dissected neoplasms. The fractional allelic loss in these seven neoplasms was 0.18, a value similar to that seen previously in colorectal carcinoma. Alleles of chromosome 18q (lost in five of six informative tumors) and of chromosome 17p (lost in four of five informative tumors) were commonly affected. Neither APC mutations (33 neoplasms), allelic shifts of dinucleotide repeats (26 neoplasms), nor immunohistochemical evidence of retinoblastoma protein underexpression (7 neoplasms) were found. Further evaluation of allelic loss in pancreatic cancer would benefit from improved methods for the analysis of lost genetic material which overcome the problems posed by the high admixture of nonneoplastic stromal and inflammatory cells in these tumors.

Adenocarcinoma↗
PubMed1994

Molecular genetic profiles of colitis-associated neoplasms.

BACKGROUND/AIMS: A major long-term risk for patients with chronic idiopathic colitis is the development of colorectal dysplasia and adenocarcinoma. The presence or absence of specific genetic changes in these lesions will provide important insights into the relationship of colitis-associated dysplasia and the development of carcinoma. METHODS: A case-study approach was used to develop detailed molecular genetic profiles of advanced dysplasias and carcinomas from six patients with ulcerative colitis or Crohn's colitis. RESULTS: Numerous genetic alterations were identified in each of the dysplasias and carcinomas profiled. These genetic alterations involved many of the same targets found in sporadic colorectal tumors and included multiple sites of allelic deletion, microsatellite instabilities, and mutations of the K-ras, p53, and APC genes. The progression of dysplasia to carcinoma was often accompanied by an accumulation of these mutations. CONCLUSIONS: Genetic alterations are common in colitis-associated neoplasia, just as in sporadic colorectal neoplasia. This could have important implications for the evaluation and treatment of patients with colitis.

Adenocarcinoma↗
PubMed1994

Frequent somatic mutations and homozygous deletions of the p16 (MTS1) gene in pancreatic adenocarcinoma.

The MTS1 gene on chromosome 9p21 encodes the p16 inhibitor of cyclinD/Cdk-4 complexes, and is deleted or mutated in a variety of tumour types. We found allelic deletions of 9p21-p22 in 85% of pancreatic adenocarcinomas. Analysis of MTS1 in pancreatic carcinomas (27 xenografts and 10 cell lines) showed homozygous deletions in 15 (41%) and sequence changes in 14 (38%). These included eight point mutations (four nonsense, two missense and two splice site mutations) and six deletions/insertions, all accompanied by loss of the wild-type allele. Sequencing of MTS1 from primary tumours confirmed the mutations. Coexistent inactivations of both MTS1 and p53 was common and suggests that abnormal regulation of cyclin-dependent kinases may play an important role in the biology of pancreatic carcinoma.

Adenocarcinoma↗
PubMed1994

An effectiveness study of a new piezoelectric sensor for train-of-four measurement.

We have developed an easy-to-use, noninvasive piezoelectric sensor for quantitative monitoring of neuromuscular block. In a clinical evaluation with 23 patients, the piezo sensor was objectively compared to a mechanomyogram (MMG) for its ability to measure train-of-four (TOF) ratio from the adductor pollicis. After administration of succinylcholine (120-200 mg intravenously [i.v.]) to facilitate intubation, neuromuscular block was maintained with vecuronium by either boluses (1-2 mg i.v.) or an infusion (0.4-1.0 micrograms.kg-1.min-1 i.v.). Paired measurements were made of the TOF ratio from both sensors over a complete range of block levels (8%-100%). The difference in the TOF ratio measurement between the sensors showed a bias of 0.018. The SD of the difference between the sensors was +/- 0.129. The limits of agreement, which define the range in which 95% of the differences between the sensor measurements lie, were from -0.24 to 0.275. The sensitivity of the piezo sensor for detecting recovery based on a TOF ratio greater than 0.70 was shown to be 0.74 with specificity of 0.91. Under the conditions tested, the piezo sensor was not as accurate as the MMG. However, it was able to predict recovery of neuromuscular block with better accuracy than shown previously by manual evaluation of the TOF ratio, making it a reasonable, convenient alternative for quantitative monitoring of recovery from neuromuscular block.

Humans↗
PubMed1992

Oncogenic forms of p53 inhibit p53-regulated gene expression.

Mutant forms of the gene encoding the tumor suppressor p53 are found in numerous human malignancies, but the physiologic function of p53 and the effects of mutations on this function are unknown. The p53 protein binds DNA in a sequence-specific manner and thus may regulate gene transcription. Cotransfection experiments showed that wild-type p53 activated the expression of genes adjacent to a p53 DNA binding site. The level of activation correlated with DNA binding in vitro. Oncogenic forms of p53 lost this activity. Moreover, all mutants inhibited the activity of coexpressed wild-type p53, providing a basis for the selection of such mutants during tumorigenesis.

Base Sequence↗
PubMed1992

Loss of heterozygosity for chromosomes 1 or 14 defines subsets of advanced neuroblastomas.

Neuroblastomas have been characterized genetically by N-myc amplification and by deletions or loss of heterozygosity (LOH) for the short arm of chromosome 1. However, recent studies have suggested deletion or allelic loss involving at least three other chromosome arms, 11q, 14q, and 17p. Therefore, we undertook an analysis of allelic loss for these respective chromosomal arms to determine the frequency and pattern of LOH as well as the correlation of these findings with other biological and clinical variables. A group of 24 pairs of normal and tumor DNAs was chosen that were representative of patients of different ages and stages. A substantial frequency of LOH (greater than or equal to 20%) was found only for 1p and 14q, whereas LOH for the other chromosome arms occurred in less than or equal to 5% of cases. On the basis of these results, we extended the analysis to a total of 59 neuroblastomas, and we found 1p LOH in 15 of the 59 cases (25%) and 14q LOH in 10 of 43 informative cases (23%). N-myc amplification was found in 15 of the 59 cases (25%). This analysis confirmed that 1p LOH and 14q LOH occurred almost exclusively in patients with advanced stages of disease. Furthermore, LOH for 1p and 14q usually occurred independent of each other, and 1p LOH frequently was associated with N-myc amplification, whereas 14q LOH was not. Thus, our results demonstrate that neuroblastomas are complex genetically and that there are at least two distinct loci for putative suppressor genes that are deleted independently in this tumor, both of which are associated with advanced stages of disease.

Blotting, Southern↗
PubMed1992

The relationship of DNA aneuploidy to molecular genetic alterations in colorectal carcinoma.

Altered total nuclear DNA content is frequent in colorectal carcinomas, but the mechanisms producing aneuploidy are unknown. Therefore, DNA ploidy by flow cytometry was correlated with molecular genetic alterations and tumor characteristics in 50 colorectal carcinomas. The prognostic value of these alterations was also evaluated because aneuploidy has been associated with poor prognosis. Thirty-nine of the carcinomas (78%) were DNA aneuploid. When compared with diploid carcinomas, aneuploid tumors had greater mean fractional allelic loss, defined as the fraction of evaluable nonacrocentric autosomal arms with deletion (0.25 +/- 0.15, range 0-0.667, vs. 0.12 +/- 0.10, range 0-0.345; P = 0.006). DNA index by flow cytometry correlated with fractional allelic loss (r = 0.38, P = 0.006). Aneuploid tumors also had more frequent allelic loss on chromosome 17p (87% vs. 55%; P = 0.017), but less frequent ras gene mutation (44% vs. 82%; P = 0.025). Among the 25 right-sided and 25 left-sided tumors, DNA diploid tumors were more frequent on the right side (P = 0.002), whereas deletion of 17p was found predominantly on the left side. Aneuploidy was associated with moderate and poor differentiation of the carcinomas but not with distant metastasis. By contrast, high fractional allelic loss, deletion of 17p, and deletion of 18q were associated with distant metastasis. In survival analysis of patients with Dukes' B or C carcinoma, DNA aneuploidy was not a significant discriminator, but patients whose tumor had deletion of 17p or deletion of both 17p and 18q had poorer survival (P = 0.045 and 0.022, respectively). The results suggest that DNA aneuploidy is associated with some of the molecular genetic alterations and phenotypic characteristics of colorectal carcinomas but is not a reliable indicator of metastatic potential.

Adult↗
PubMed1992

Definition of a consensus binding site for p53.

Recent experiments have suggested that p53 action may be mediated through its interaction with DNA. We have now identified 18 human genomic clones that bind to p53 in vitro. Precise mapping of the binding sequences within these clones revealed a consensus binding site with a striking internal symmetry, consisting of two copies of the 10 base pair motif 5'-PuPuPuC(A/T)(T/A)GPyPyPy-3' separated by 0-13 base pairs. One copy of the motif was insufficient for binding, and subtle alterations of the motif, even when present in multiple copies, resulted in loss of affinity for p53. Mutants of p53, representing each of the four "hot spots" frequently altered in human cancers, failed to bind to the consensus dimer. These results define the DNA sequence elements with which p53 interacts in vitro and which may be important for p53 action in vivo.

Base Sequence↗
PubMed1992

The relationship of quantitative nuclear morphology to molecular genetic alterations in the adenoma-carcinoma sequence of the large bowel.

The relationship of abnormal nuclear morphology to molecular genetic alterations that are important in colorectal tumorigenesis is unknown. Therefore, Feulgen-stained isolated nuclei from 22 adenomas and 42 carcinomas that had been analyzed for ras gene mutations and allelic deletions on chromosomes 5q, 18q, and 17p were characterized by computerized image analysis. Both nuclear area and the nuclear shape factor representing irregularity correlated with adenoma-carcinoma progression (r = 0.57 and r = 0.52, P < 0.0001), whereas standard nuclear texture, a parameter of chromatin homogeneity, was inversely correlated with progression (r = -0.80, P < 0.0001). The nuclear parameters were strongly interrelated (P < 0.0005). In multivariate analysis, the nuclear parameters were predominantly associated with adenoma-carcinoma progression (P < or = 0.0001) and were not influenced significantly by the individual molecular genetic alterations. Nuclear texture, however, was inversely correlated with fractional allelic loss, a global measure of genetic changes, in carcinomas (r = -0.39, P = 0.011). The findings indicate that nuclear morphology in colorectal neoplasms is strongly related to tumor progression. Nuclear morphology and biologic behavior appear to be influenced by accumulated alterations in cancer-associated genes.

Adenoma↗
PubMed1991

Identification of p53 as a sequence-specific DNA-binding protein.

The tumor-suppressor gene p53 is altered by missense mutation in numerous human malignancies. However, the biochemical properties of p53 and the effect of mutation on these properties are unclear. A human DNA sequence was identified that binds specifically to wild-type human p53 protein in vitro. As few as 33 base pairs were sufficient to confer specific binding. Certain guanines within this 33-base pair region were critical, as methylation of these guanines or their substitution with thymine-abrogated binding. Human p53 proteins containing either of two missense mutations commonly found in human tumors were unable to bind significantly to this sequence. These data suggest that a function of p53 may be mediated by its ability to bind to specific DNA sequences in the human genome, and that this activity is altered by mutations that occur in human tumors.

Base Sequence↗
PubMed1991

Wild-type but not mutant p53 immunopurified proteins bind to sequences adjacent to the SV40 origin of replication.

The DNA from a wide variety of human tumors has sustained mutations within the conserved p53 coding regions. We have purified wild-type and tumor-derived mutant p53 proteins expressed from baculovirus vectors and examined their interactions with SV40 DNA. Using DNAase I footprinting assays, we observed that both human and murine wild-type p53 proteins bind specifically to sequences adjacent to the late border of the viral replication origin. By contrast, mutant p53 proteins failed to bind specifically to these sequences. SV40 T antigen prevented wild-type p53 from interacting with this region. These data show that normal but not oncogenic forms of p53 are capable of sequence-specific interactions with viral DNA. Furthermore, they provide insights into the mechanisms by which viral proteins might regulate the control of viral growth and cell division.

Animals↗