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C A Westbrook

Publications and source records attributed to C A Westbrook.

At least 37 records · Page 2Linked to original sources
PubMed1995

Chromosome 17p allelic loss in colorectal carcinoma. Clinical significance.

OBJECTIVE: To correlate allelic losses on chromosomes 5q, 8p, 17p, and 18q in colorectal adenocarcinomas with histopathologic features of known prognostic significance. DESIGN: DNA was extracted from paired samples of 56 fresh-frozen colorectal adenocarcinomas (one classified as Dukes' stage A, 22 as Dukes' stage B, 27 as Dukes' stage C, and six as Dukes'stage D) and adjacent normal mucosa. SETTING: Specimens were resected at the University of Chicago (Ill) and the University of Padova (Italy) in 1991. PATIENTS: Samples were obtained from consecutive patients. INTERVENTIONS: Chromosomes 5q, 8p, 17p, and 18q were studied for loss of heterozygosity by means of Southern hybridization blot analysis of restriction fragment length polymorphisms, and the results were correlated with pathologic tumor stage, degree of differentiation, and lymphatic and/or vascular microinvasion. RESULTS: Chromosomes 17p and 18q exhibited the highest frequency of loss of heterozygosity (40.6% and 48.8%, respectively). Most of the allelic losses were found in advanced tumors (60% in Dukes' stages C and D combined). A statistically significant correlation was found between loss of heterozygosity on chromosome 17p and the presence of lymphatic and/or vascular microinvasion (P < .01, Fisher's Exact Test). CONCLUSIONS: There was a significant correlation between loss of heterozygosity on chromosome 17p and the presence of lymphatic and/or vascular microinvasion in colorectal adenocarcinoma, a known stage-independent negative prognostic risk factor. Detection of loss of heterozygosity on chromosome 17p may identify a group of patients who may benefit from more aggressive surgical and/or early adjuvant therapy.

Alleles↗
PubMed1995

Loss of heterozygosity from the short arm of chromosome 8 is an early event in breast cancers.

Loss of heterozygosity (LOH) from the short arm of chromosome 8 (8p) is common to many human carcinomas, including those of the colon and prostate. It localizes to two discrete regions, 8p21 and 8p22. This suggests the presence of at least two tumor suppressor genes (TSGs) on this chromosome arm. Human breast cancers show consistent 8p deletions in cytogenetic studies, chromosome 8 aneusomy and isochromosome 8q, indicating that the relevant gene(s) may play a role, but the results of molecular analyses of chromosome 8 in breast cancer have been variable. We present here data for 8p LOH in an unselected series of human breast cancers with the use of three CA-repeat markers that showed high rates of LOH in other tumors. All cases were informative for at least one marker, and LOH was seen in 11 of 20 cases (55%). LOH was more frequent for the 8p22 markers D8S254 and D8S133 than for NEFL in 8p21. Regional metastases of the tumors showed allele profiles identical to those of their primaries regardless of whether there was LOH or retention of alleles. One case of microsatellite instability (RER+) was seen. LOH did not correlate with receptor status, ploidy, percentage of cells in S phase, or tumor size: We observed LOH at equal rates in small (< 2 cm) and in larger (> 2 cm) tumors. The data suggest that LOH from 8p is frequent in human breast cancers and that loss of the putative 8p TSG may be an important event in early stage breast cancer.

Adult↗
PubMed1995

Evidence for locus heterogeneity in autosomal dominant limb-girdle muscular dystrophy.

Limb-girdle muscular dystrophy (LGMD) is a diagnostic classification encompassing a broad group of proximal myopathies. A gene for the dominant form of LGMD (LGMD1A) has recently been localized to a 7-cM region of chromosome 5q between D5S178 and IL9. We studied three additional dominant LGMD families for linkage to these two markers and excluded all from localization to this region, providing evidence for locus heterogeneity within the dominant form of LGMD. Although patterns of muscle weakness were similar in all families studied, the majority of affected family members in the chromosome 5-linked pedigree have a dysarthric speech pattern, which is not present in any of the five unlinked families. The demonstration of heterogeneity within autosomal dominant LGMD is the first step in attempting to subclassify these families with similar clinical phenotypes on a molecular level.

Adolescent↗
PubMed1994

A novel transcriptional suppressor located within a downstream intron of the BCR gene.

A reciprocal translocation between chromosomes 9 and 22 creates the Philadelphia (Ph1) chromosome in chronic myelogenous leukemia. This translocation results in the fusion of the ABL and the BCR genes to form a BCR/ABL fusion gene, the product of which has a greatly increased protein tyrosine kinase activity in comparison with the normal ABL protein. The chromosome 22 translocation breakpoints are concentrated within a 5.8-kilobase region named the major break-point cluster region (Mbcr). Gel mobility shift and DNase I footprinting assays have defined binding sites for three proteins, BIF 1-3 (BCR intron factors 1-3), lying within a 427-base pair fragment of the Mbcr. This 427-base pair fragment functions as a transcriptional silencer with both the BCR as well as a heterologous promoter. The silencing is position- and orientation-independent. The transcriptional effects are greatest in chronic myelogenous leukemia cells, decreased in HeLa and B-cells, and absent in T-lymphocytes. Gel mobility shift assays show a corresponding difference in pattern when the T-lymphocyte nuclear extract is compared with other cell lines. The Mbcr appears to contain a novel group of transcriptional silencers that share a common binding motif with a recently described suppressor in the mouse Adh-1 gene.

Base Composition↗
PubMed1994

CGG-repeat polymorphism of the BCR gene rules out predisposing alleles leading to the Philadelphia chromosome.

The Philadelphia chromosome (Ph) is associated with leukemia, most frequently of the chronic myelogenous variety. The Ph chromosome is a translocation chromosome which gains oncogenic potential through the fusion of the ABL oncogene of chromosome 9 with the BCR gene of chromosome 22. The Ph is believed to arise from random chromosome rearrangement with a subsequent selective advantage of the malignant cell line. However, alleles may be present in the population which predispose toward this specific rearrangement. We used a highly polymorphic CGG-repeat polymorphism within the first exon of the BCR gene to determine BCR allele frequencies among 26 leukemia patients with the Ph chromosome and 63 control individuals. Eight BCR alleles of variable CGG-repeat length were present in both groups at statistically similar frequencies and in Hardy-Weinberg equilibrium. We therefore concluded that there are no alleles of the BCR gene that have a major predisposing influence on the development of the Ph chromosome and subsequent leukemia.

Alleles↗
PubMed1994

Deletion mapping reveals two regions of chromosome 8 allele loss in colorectal carcinomas.

Colorectal carcinogenesis is associated with the accumulation of genetic changes involving both dominant oncogenes and tumor suppressor genes. Although at least four different genes have been implicated in the process, the detection of allele loss from other regions of the genome suggests the involvement of additional genes. The short arm of chromosome 8 is one of these regions; loss of heterozygosity occurs at rates ranging from 30 to 50%. To define the region of common deletion containing the putative tumor suppressor gene, we analyzed a series of 87 carcinomas for allele loss in different regions of the short arm of chromosome 8 by using Southern blot analysis and a panel of polymorphic probes. We found allele loss in 33% of our cases, which involves two separate regions, one in the p-terminal region of the chromosome, 8p23.1-pter, where 45% of informative cases demonstrated loss, and the other in the mid-p region, at 8p21, where 31% of cases showed allele loss. No tumors showed loss of heterozygosity for both regions. These findings suggest the presence of two discrete genes related to colorectal carcinogenesis on the short arm of chromosome 8.

Alleles↗
PubMed1994

Loss of heterozygosity in 8p is associated with microinvasion in colorectal carcinoma.

Loss of heterozygosity (LOH) from the short arm of chromosome 8 is frequent in a variety of malignancies, suggesting the presence of a tumor suppressor gene in this region. Previous studies suggested that this deletion may correlate with higher clinicopathologic stages in colorectal cancer, but others did not support this finding; in part, this difficulty is due to the low heterozygosity of the RFLP markers that were used. Here we report on a preliminary investigation in which we used highly informative microsatellite markers to determine whether deletions of 8p are correlated with poor prognostic features. Paraffin-embedded tumor tissue from 15 patients was analyzed with a panel of three microsatellite markers that are known to be sites of frequent LOH. Fourteen of the 15 cases were informative with at least one marker, and 7 showed LOH. Analysis of clinical features showed that there was no relation of 8p LOH with patient age or tumor stage, grade, location, or pattern of growth. However, a statistically significant correlation was seen between LOH and lymphatic, vascular, or perineural microinvasion (Fisher exact test, P = 0.01). This histologic feature is known to be a stage-independent indicator of prognosis. Our data suggest that 8p LOH may be associated with poor outcome and demonstrate the utility of these microsatellite markers for its detection.

Adenocarcinoma↗
PubMed1994

Human APC gene expression in rodent colonic epithelium in vivo using liposomal gene delivery.

Mutations or loss of the APC tumor-suppressor gene is important for the development of colorectal polyps and cancers, but little is known about the function of this gene in normal tissue. To study the role of APC and other genes in colonocytes in vivo, a system was developed whereby transient expression of genes is established in normal rodent colonic epithelium, using liposomal gene delivery by rectal catheter infusion. Expression of a beta-galactosidase reporter gene and of the human APC gene under a constitutive promoter is demonstrated. A high efficiency of transfection is maintained, with close to 100% of epithelial cells expressing the introduced gene. Expression is transient and does not persist beyond 4 days, consistent with the normal turnover time of gut epithelium, but it can be maintained by repeated treatments. Human APC was expressed for three weeks under these conditions at approximately one-tenth the level of the endogenous APC gene, and no toxicity was observed beyond that attributed to repeated rectal enemas. These results reveal that in vivo expression of exogenous gene is feasible using a liposomal delivery system and suggest a method to further study the physiologic role of APC or other genes in the interrelated process of colonic epithelial proliferation and differentiation.

Animals↗
PubMed1994

Physical and genetic map of 5q31: use of fluorescence in situ hybridization data to identify errors in the CEPH database. Centre d'Etude de Polymorphisme Humain.

Chromosome 5, band q31, contains the genes responsible for a number of interesting genetic and malignant diseases, as well as many cloned genes. To prepare a high-resolution map of this region, eight anonymous DNA markers were mapped by combining genetic data derived from linkage analysis, with physical data obtained using two-color fluorescent in situ hybridization (FISH). Probe order was determined by FISH on metaphase cells, supplemented with interphase analysis, while genetic distance and likely order were determined by multipoint linkage analysis using genotype data from Centre d'Etude de Polymorphisme Humain (CEPH) pedigrees. Discrepancies between the genetic and physical maps suggested that there was a high rate of genotyping errors in the CEPH data for these markers, and prompted a statistical analysis to identify these errors. By assuming a known physical order (as determined by FISH) it was possible to identify markers which had the greatest degree of error. The average typing error was estimated at 1.8%, but several markers had much higher error rates; a 14% error rate was predicted for one locus, which was subsequently confirmed by retyping. The analysis led to the preparation of a revised map spanning 24.5 cM of 5q31. This study illustrates the power of FISH to determine physical order over a wide genomic distance, and demonstrates how order can be used as an adjunct to linkage analysis, particularly in the identification of genotyping errors.

Chromosome Mapping↗
PubMed1994

Detection of MLL gene rearrangements in adult acute lymphoblastic leukemia. A Cancer and Leukemia Group B study.

Specific structural rearrangements involving chromosome band 11q23 occur in a variety of hematologic malignancies, including an estimated 2-7% of patients with acute lymphoblastic leukemia (ALL). Translocations involving chromosome band 11q23 have been associated with a poor prognosis in patients with ALL. Recently, a gene known as MLL has been identified which is involved in acute lymphoid and myeloid leukemias with rearrangements at 11q23. A 0.74-kilobase (kb) cDNA probe from the MLL gene can detect both common and uncommon rearrangements involving MLL on conventional Southern blots. We studied 86 newly diagnosed adults entered on an ALL clinical trial to investigate the incidence of MLL gene rearrangements and to determine clinical, morphologic, immunologic and cytogenetic characteristics of such patients. Two of 86 patients had MLL gene rearrangements detected by Southern blot analysis. One of these 86 patients had an 11q23 translocation by cytogenetic analysis whereas the second patient was unevaluable by standard cytogenetic analysis. Southern blot identification of rearrangements involving MLL, especially in patients with limited material for cytogenetic analysis, can provide critical diagnostic and prognostic information which may be useful in the clinical management of patients with these abnormalities.

Adolescent↗
PubMed1993

Cytogenetic and molecular delineation of the smallest commonly deleted region of chromosome 5 in malignant myeloid diseases.

Loss of a whole chromosome 5 or a deletion of its long arm (5q) is a recurring abnormality in malignant myeloid neoplasms. To determine the location of genes on 5q that may be involved in leukemogenesis, we examined the deleted chromosome 5 homologs in a series of 135 patients with malignant myeloid diseases. By comparing the breakpoints, we identified a small segment of 5q, consisting of band 5q31, that was deleted in each patient. This segment has been termed the critical region. Distal 5q contains a number of genes encoding growth factors, hormone receptors, and proteins involved in signal transduction or transcriptional regulation. These include several genes that are good candidates for a tumor-suppressor gene, as well as the genes encoding five hematopoietic growth factors (CSF2, IL3, IL4, IL5, and IL9). By using fluorescence in situ hybridization, we have refined the localization of these genes to 5q31.1 and have determined the order of these genes and of other markers within 5q31. By hybridizing probes to metaphase cells with overlapping deletions involving 5q31, we have narrowed the critical region to a small segment of 5q31 containing the EGR1 gene. The five hematopoietic growth factor genes and seven other genes are excluded from this region. The EGR1 gene was not deleted in nine other patients with acute myeloid leukemia who did not have abnormalities of chromosome 5. By physical mapping, the minimum size of the critical region was estimated to be 2.8 megabases. This cytogenetic map of 5q31, together with the molecular characterization of the critical region, will facilitate the identification of a putative tumor-suppressor gene in this band.

Acute Disease↗
PubMed1993

Physical localization of 70 polymorphic markers to human chromosome 5 by fluorescence in situ hybridization.

We used fluorescence in situ hybridization (FISH) to prepare a cytogenetic framework map of 21 polymorphic markers that had been used previously to construct a genetic linkage anchor map of chromosome 5. In addition, we localized 49 other markers that have been genotyped on CEPH families. This study demonstrates that FISH can be used to confirm genetic linkage data, and that it can provide a means of determining the cytogenetic locations and relative order of markers whose order could not be assigned by genetic linkage analysis alone. The cytogenetic map prepared by FISH may help to identify probes of interest for regional mapping studies.

Chromosome Mapping↗
PubMed1992

Clinical significance of the BCR-ABL fusion gene in adult acute lymphoblastic leukemia: a Cancer and Leukemia Group B Study (8762).

The Philadelphia (Ph1) chromosome, or its molecular counterpart, the BCR-ABL fusion gene, is a rare but important prognostic indicator in childhood acute lymphoblastic leukemia (ALL), but its impact on adult ALL has not been well ascertained. A prospective study of the BCR-ABL fusion gene was begun on patients entered on clinical trials conducted by the Cancer and Leukemia Group B (CALGB). All patients received intensive, multiagent chemotherapy that included daunorubicin. Over 2 years, 56 patients were studied for molecular evidence of a BCR-ABL gene using Southern blot and pulsed-field gel hybridization analysis. Results were compared with cytogenetic detection of a Ph1 chromosome, and clinical features were compared for the BCR-ABL-positive and -negative groups. Molecular methods detected the BCR-ABL gene in 30% of cases compared with cytogenetic detection of the Ph1 chromosome in only 23%. The majority of cases (76%) showed the p190 gene subtype similar to pediatric ALL; the BCR-ABL-positive cases displayed a more homogeneous immunophenotype than the BCR-ABL-negative cases and were predominantly CALLA positive (86%) and B-cell surface antigen positive (82%). The rate of achieving complete remission was similar in the BCR-ABL-positive and -negative groups (71% and 77%, respectively, P = .72). There were more early relapses in the BCR-ABL-positive group, resulting in a shorter remission duration that was especially marked in the CALLA-positive and B-cell antigen-positive populations. These preliminary data suggest that the impact of the BCR-ABL gene on clinical outcome in ALL may be on maintenance of complete remission (CR) rather than achievement of CR when aggressive, multiagent chemotherapy is used. This study identifies the BCR-ABL gene as an important factor in adult ALL and demonstrates the utility of molecular methods for its accurate diagnosis.

Adolescent↗
PubMed1992

Complex translocation involving Ph chromosome in a patient with typical chronic myelogenous leukemia.

We report a cytogenetic study of a patient with chronic myelogenous leukemia (CML) who, while displaying a Philadelphia (Ph) chromosome, resulting from a standard t(9;22) at diagnosis, during the chronic phase (CP) showed disappearance of the Ph and occurrence of new chromosome changes, including a marker probably arising from a translocation involving chromosome 17 and the Ph. In situ hybridization confirmed the cytogenetic appearance and demonstrated that the breakpoint on the Ph marker occurred below the BCR-ABL fusion gene.

Chromosome Deletion↗
PubMed1992

The role of molecular techniques in the clinical management of leukemia. Lessons from the Philadelphia chromosome.

The Philadelphia chromosome (Ph1) was the first genetic change to be associated consistently with leukemia, and it is one of the best understood on the molecular level. Because of this, it is an excellent model to investigate the application of molecular techniques to the clinical setting. These techniques are reviewed as are their clinical use in chronic myelogenous leukemia (CML), acute lymphoblastic leukemia (ALL), and transplantation. The Ph1 is caused by the fusion of two genes on chromosomes 9 and 22, resulting in the BCR-ABL fusion gene. This new gene is believed to be the cause of these Ph1-positive leukemias. The ability to detect the BCR-ABL fusion gene evolved from cytogenetic detection to Southern blot analysis, and now includes sophisticated techniques such as polymerase chain reaction (PCR) methods and pulsed-field gels. Diagnosis of the BCR-ABL fusion gene by Southern blot detection of bcr genetic rearrangements is the prototype of molecular cancer diagnosis. The sensitivity and clinical uses of this test are reviewed, especially its application to monitoring the response to treatment. PCR methods enable the researcher to detect 1 CML cell in a population of 10(5) cells. Clinical experience with PCR, especially in transplantation medicine, is providing a better understanding of the meaning of the terms "remission" and "cure." Newer techniques using fluorescent in situ hybridization have considerable potential for BCR-ABL detection, but no clinical experience has been gained with these techniques currently. The diagnosis of the BCR-ABL fusion gene in ALL has important clinical implications because it is the most common molecular genetic change in adult ALL and is associated with short remissions and poor outcome in all age groups. Diagnosis of the BCR-ABL fusion in ALL is difficult because the molecular findings are more heterogeneous than they are in CML. The methods available and their accuracy and sensitivity are compared. A review of their clinical impact is included.

Fusion Proteins, bcr-abl↗