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Biomedical subjects

G A Dent

Publications and source records attributed to G A Dent.

At least 19 recordsLinked to original sources
PubMed2002

A case-control study of tobacco use and other non-occupational risk factors for t(14;18) subtypes of non-Hodgkin's lymphoma (United States).

OBJECTIVE: Non-Hodgkin's lymphoma (NHL) encompasses diverse subtypes, and analyzing NHL as a single outcome may mask associations. In a new approach we evaluated associations with subtypes defined by the t(14;18) translocation, reasoning that cases within these subtypes would have more common risk factors than all NHL combined. METHODS: Archival biopsies from cases in a population-based NHL study were assayed for t(14;18) using polymerase chain reaction amplification. Exposures in 68 t(14;18)-positive and 114-negative cases were compared with 1245 controls. The expectation-maximization algorithm was used to fit polytomous regression models based on all available information, including data from 440 unclassified cases. RESULTS: Family history of hemolymphatic cancer was associated with t(14;18)-negative NHL (odds ratio (OR) 2.4, 95% confidence interval (CI) 1.4 3.9). but not t(14;18)-positive NHL. Cigarette smoking was weakly associated with t(14;18)-positive NHL (OR 1.7, CI 0.9-3.3), but ORs decreased as smoking increased. Chewing tobacco was associated with t(14;18)-positive NHL, particularly when used before age 18 (OR 2.5. CI 1.0-6.0, 13 exposed cases). Odds ratios for both case-subtypes were doubled among hair-dye users. CONCLUSIONS: Cigarette smoking was not clearly associated with t(14;18)-positive NHL. Family history may be a marker for factors that act specifically through t(14;18)-negative pathogenic mechanisms.

Adolescent↗
PubMed2001

Agricultural risk factors for t(14;18) subtypes of non-Hodgkin's lymphoma.

The t(14;18) translocation is a common somatic mutation in non-Hodgkin's lymphoma (NHL) that is associated with bcl-2 activation and inhibition of apoptosis. We hypothesized that some risk factors might act specifically along t(14;18)-dependent pathways, leading to stronger associations with t(14;18)-positive than t(14;18)-negative non-Hodgkin's lymphoma. Archival biopsies from 182 non-Hodgkin's lymphoma cases included in a case-control study of men in Iowa and Minnesota (the Factors Affecting Rural Men, or FARM study) were assayed for t(14;18) using polymerase chain reaction amplification; 68 (37%) were t(14;18)-positive. We estimated adjusted odds ratios (OR) and 95% confidence intervals (CI) for various agricultural risk factors and t(14;18)-positive and -negative cases of non-Hodgkin's lymphoma, based on polytomous logistic regression models fit using the expectation-maximization (EM) algorithm. T(14;18)-positive non-Hodgkin's lymphoma was associated with farming (OR 1.4, 95% CI = 0.9-2.3), dieldrin (OR 3.7, 95% CI = 1.9-7.0), toxaphene (OR 3.0, 95% CI = 1.5-6.1), lindane (OR 2.3, 95% CI = 1.3-3.9), atrazine (OR 1.7, 95% CI = 1.0-2.8), and fungicides (OR 1.8, 95% CI = 0.9-3.6), in marked contrast to null or negative associations for the same self-reported exposures and t(14;18)-negative non-Hodgkin's lymphoma. Causal relations between agricultural exposures and t(14;18)-positive non-Hodgkin's lymphoma are plausible, but associations should be confirmed in a larger study. Results suggest that non-Hodgkin's lymphoma classification based on the t(14;18) translocation is of value in etiologic research.

Adult↗
PubMed1999

Intra-abdominal embryonal rhabdomyosarcoma in an adult.

Rhabdomyosarcoma is an uncommon neoplasm in the adult population. Sporadic cases of primary rhabdomyosarcoma arising in the abdomen have been reported, but these cases are limited almost exclusively to the pediatric population. We report a well-documented case of primary intra-abdominal rhabdomyosarcoma in a 57-year-old woman. The patient presented with a pelvic mass and an elevated serum CA 125 and was referred to gynecologic oncologists at our institution for a presumed primary gynecologic malignancy. Intraoperatively, amorphous gelatinous tumor comprised a large portion of the peritoneal cavity. Surgical exploration of the abdomen failed to implicate any specific organ as the site of origin of the tumor. The overall histologic pattern of the resected tumor was most consistent with embryonal type rhabdomyosarcoma. To our knowledge this is the first well-documented case report of non-hepatobiliary, adult, intra-abdominal embryonal rhabdomyosarcoma in the English language literature. The presentation of a rare adult sarcoma mimicking a gynecologic malignancy was an unusual feature that complicated the diagnosis in this case.

Abdominal Neoplasms↗
PubMed1999

MUC1 expression in hematopoietic tissues.

The MUC1 gene encodes the core protein of episialin, which is recognized by several antibodies. Reverse transcription-polymerase chain reaction (RT-PCR) detection of MUC1 transcripts has been proposed for the detection of micrometastases from breast cancers. MUC1 expression in hematopoietic tissues has been reported but not confirmed. Our preliminary RT-PCR studies confirmed MUC1 expression by MDA-231 breast cancer cells. Western blots of MDA-231 proteins stained with anti-MUC1 core gave one 68-kd (core protein) band, with an additional high molecular weight (HMW) band in blots stained with anti-epithelial membrane antigen (EMA). MUC1 expression was detectable by RT-PCR in 4 samples each of peripheral blood, bone marrow, and lymph node. MUC1 expression was detectable by Western blot analysis using anti-MUC1 core and anti-EMA in 2 peripheral blood samples and all bone marrow samples. Western blots from all lymph node samples stained positively with anti-EMA for the HMW product, but the 68-kd product was less prominent. Separated peripheral blood lymphocytes and granulocytes showed similar levels of MUC1 expression. RT-PCR studies demonstrated MUC1 expression in various hematopoietic cell lines. Western blots showed the 68-kd and HMW products in a granulopoietic line, with only the 68-kd product in 3 lymphoblastoid lines. MUC1 is expressed ubiquitously in hematopoietic tissues and is unsuitable for use as a marker for epithelial micrometastases.

Biomarkers, Tumor↗
PubMed1996

Focal adhesion kinase as a marker of invasive potential in differentiated human thyroid cancer.

BACKGROUND: The FAK gene encodes a 125-kDa tyrosine kinase (p125FAK) involved in signal transduction pathways used in cell adhesion, motility, and anchorage-independent growth. Because thyroid carcinomas have a wide variability in their propensity for invasion and metastasis, we studied the expression of FAK in a variety of thyroid tissues. METHODS: We synthesized a recombinant N-terminal fragment of the human FAK protein and developed a specific polyclonal antisera. Using Western blot analysis, we assessed the levels of p125FAK expression in 30 human thyroid tissue samples from 27 patients that included paired normal and malignant specimens. Levels of FAK protein in individual tumors were quantitated by densitometric scanning of the immunoblots, and the results were correlated with tumor histology and biologic behavior. RESULTS: The levels of FAK expression were directly correlated with thyroid carcinomas demonstrating the most aggressive phenotypes. The highest levels of p125FAK were seen in follicular carcinomas and tumors associated with distant metastatic foci. In contrast, neoplastic thyroid tissues with limited invasive potential, such as papillary carcinomas, follicular adenomas, and other nonmalignant thyroid lesions, showed minimal p125FAX expression. CONCLUSIONS: Overexpression of FAK may be part of a mechanism for invasion and metastasis of thyroid cancer. Furthermore, the levels of p125FAK may serve as a marker of biologic behavior in this disease.

Adenocarcinoma, Follicular↗
PubMed1995

Overexpression of the focal adhesion kinase (p125FAK) in invasive human tumors.

The focal adhesion kinase (FAK) gene encodes a tyrosine kinase (p125FAK) thought to be involved in signal transduction pathways used in cell adhesion, motility, and anchorage-independent growth. Because alterations in these cellular processes occur in tumor invasion and metastasis, we studied the protein expression of FAK in a variety of human tumors and found that in the 119 samples studied, increased levels of p125FAK correlated with the invasive potential of a tumor. By comparing FAK expression in tumors with normal tissue from the same patient, we found that p125FAK was significantly elevated in 17 (100%) of 17 invasive and metastatic colonic lesions and in 22 (88%) of 25 invasive and metastatic breast tumors. Additional studies of FAK expression in 13 high grade sarcomas showed high levels in all samples compared to benign, noninvasive mesenchymal specimens. Furthermore, FAK protein levels were elevated in preinvasive lesions, such as large (> 2 cm) colonic villous adenomas, whereas noninvasive, yet hypercellular, neoplastic tissues such as parathyroid and hepatocellular adenomas did not overexpress FAK. These data provide evidence that both epithelial and mesenchymal tumor progression are accompanied by increased p125FAK expression and suggest that the level of FAK expression might be a marker for the invasive potential of a tumor.

Adenofibroma↗
PubMed1995

Receptor tyrosine kinases expressed in metastatic colon cancer.

Using a PCR-based cloning technique, we have isolated a series of DNA fragments coding for tyrosine kinases that are expressed in a metastatic human colon tumor, and have subsequently analyzed their expression pattern at the protein level in human tumors. We identified both the alpha and the beta forms of the platelet-derived growth factor receptor (PDGFR), axl and 8 other genes, including 3 cytoplasmic tyrosine kinases. To study their expression in human colon cancer, we performed Western blots of matched sets of normal tissues and of carcinomas from the same patient. These revealed that the alpha-PDGFR migrates predominantly as a 200-kDa band in 8/8 normal tissues, and as a 170-kDa band in 17/17 malignant tissues, as well as in colonic polyps, suggesting that expression of an isoform of this receptor may be a marker for the progression of colon cancer. Additional studies showed that the Axl receptor tyrosine kinase was expressed at 10-fold higher levels in a peritoneal metastatic nodule than in other normal and malignant tissues. Immunohistochemistry revealed Axl over-expression specifically in the malignant cells of the tumor. This indicates that over-expression and possibly a differential processing event of tyrosine kinase receptors may be involved in colon cancer, and that they are potential markers for the progression of this disease.

Amino Acid Sequence↗
PubMed1995

Loss of heterozygosity on chromosome 17q11-21 in cancers of women who have both breast and ovarian cancer.

OBJECTIVE: Our purpose was to determine the frequency of allele loss in the region of the BRCA1 gene in cancers of women who have both breast and ovarian cancer. STUDY DESIGN: Four polymorphic microsatellite markers on chromosome 17q11-21 were examined by the polymerase chain reaction in deoxyribonucleic acid from paraffin blocks of normal tissues, breast cancers, and ovarian cancers in 24 women who had primary cancers in both sites. RESULTS: Loss of heterozygosity was seen in one or more markers on chromosome 17q11-21 in 46% of breast cancers and 78% of ovarian cancers. In 38% of cases allele loss was seen in both cancers, and in all these cases the same allele was lost in both cancers. Significantly younger ages at diagnosis of both breast and ovarian cancer were noted among cases with allele loss in both cancers compared with cases in which allele loss was found only in the ovarian cancer (p < 0.05). CONCLUSIONS: Because cases in which 17q11-21 allele loss was seen in both cancers had a young age of onset and the same allele was always deleted in both cancers, hereditary alterations in BRCA1 may play a role in this subset. The older age of onset in cases in which allele loss was seen only in the ovarian cancer suggests that the development of these cancers is not related to an inherited defect in BRCA1.

Alleles↗
PubMed1994

A comparative study of frozen-section immunoperoxidase and flow cytometry for immunophenotypic analysis of lymph node biopsies.

Immunophenotyping by flow cytometry and frozen-section immunoperoxidase was compared on 21 consecutive lymph node biopsy specimens, of which a diagnosis of lymphoma was made for 11 specimens. Samples for flow cytometry were obtained by a fine-needle aspiration technique. Concordance between frozen-section immunoperoxidase and flow cytometry for all routine markers on all specimens ranged from 76 to 100%. In general, B-cell markers showed poorer concordance than T-cell markers, with kappa and lambda light chains having the poorest concordance, at 76% each. Flow cytometry was significantly more sensitive (90 versus 30%; P < 0.006) and had a significantly higher negative predictive value (100 versus 63%; P < 0.006) than frozen-section immunoperoxidase for demonstrating light-chain restriction. There was no significant difference in the specificities (100 versus 91%) or positive predictive values (100% each) between the two methods. Both methods demonstrated characteristic immunophenotypes for intermediate cell lymphomas, small lymphocytic lymphomas, and T-cell lymphoblastic lymphomas. Frozen-section immunoperoxidase and flow cytometry appear to be significantly concordant methods for immunophenotypic analysis of lymph node biopsies. Light-chain restriction is more readily demonstrated by flow cytometry than frozen-section immunoperoxidase. We believe that ex vivo fine-needle aspiration is a simple and reliable method of obtaining cell suspensions of lymph nodes for flow cytometry.

Flow Cytometry↗
PubMed1993

Immunohistochemistry of the androgen receptor in human benign and malignant prostate tissue.

The role of the androgen receptor in the development and progression of prostatic carcinoma has not been defined. The development of androgen receptor antibodies has provided new opportunities for direct immunohistochemical analysis. We compared the androgen receptor staining characteristics of fresh human prostatic carcinoma with benign prostatic hyperplasia (BPH) using an avidin-biotin complex method. Cancer and BPH obtained from the same radical retropubic prostatectomy specimen in 10 prostate cancer patients (68.5 +/- 7.3 years old standard deviation) and BPH from 10 noncancer patients (71.5 +/- 7.7 years old) were incubated with AR52, a rabbit polyclonal antibody against a synthetic androgen receptor peptide. Nuclei within each section were graded for intensity of androgen receptor staining (0-absent, 1-weak, 2-moderate or 3-strong) and the percentage (0 to 100%) of nuclei sampled staining at each of these intensity levels was determined. A total intensity score (0 to 300) was the summation of the products of each intensity score (0 to 3) and their corresponding percentages. Cancer sections (166 +/- 69) stained less intensely and more heterogeneously than BPH in cancer patients (246 +/- 41, Student's t test p < 0.05) and noncancer patients (225 +/- 39, p < 0.05). The decreased intensity and greater heterogeneity of androgen receptor staining in cancer tissue may implicate a quantitative or functional difference in androgen receptor between prostatic carcinoma and BPH.

Aged↗
PubMed1992

Classification and staging of lymphoma by molecular genetics.

Recombinant DNA technology has provided a wealth of new observations in the study of lymphoma. Progress has been enhanced by the unique rearrangement of immune-specific genes during normal lymphocyte differentiation. Because these gene rearrangements are irreversible and are inherited in all cellular progeny, lymphoid tumors have a monoclonal genomic structure. Molecular analysis of genomic structure is a powerful new method of assessing clonality and lineage to supplement histologic examination in achieving accurate diagnosis and staging of lymphomas. Furthermore, the frequent occurrence of translocations in lymphoid neoplasms provides a second pathway for genomic analysis. In 57 B-cell lymphomas tested by Southern blot and polymerase chain reaction, the authors found evidence of bc12 gene translocation in 100% of follicular small cleaved cell lymphomas, 67% of diffuse small cleaved cell lymphomas, 33% of mixed lymphomas, 25% of diffuse large cell lymphomas, and 25% of small noncleaved lymphomas. They also describe their experience with immunoglobulin heavy chain and T-cell receptor beta chain genomic analysis as well as review the published literature on the utility of molecular genetics in the classification and staging of lymphoma. Future applications of molecular diagnostics in the clinical management of lymphoma patients are assessed.

Base Sequence↗
PubMed1992

p53 gene mutations in human endometrial carcinoma.

Although carcinoma of the uterine endometrium is the most frequently diagnosed malignancy of the female reproductive tract, the molecular genetic features of this tumor have yet to be described in significant detail. Since mutations of the p53 tumor suppressor gene are the single most common genetic alteration found in human malignancies, we examined the hypothesis that p53 mutations occur in human endometrial carcinoma. Sequencing analysis of exons 5-8 revealed point mutations in 3 of 21 (14%) tumors; one mutation was an unusual single-base insertion at codons 176-177, resulting in a premature stop codon, whereas the other two were CGG----TGG transitions at codon 248. Two of these tumors showed reduction to homozygosity at the p53 allele, but one tumor apparently retained heterozygosity. These data indicate that p53 mutations occur in human endometrial carcinoma, although relatively infrequently, and that loss of the normal p53 allele does not necessarily occur with point mutation of the p53 gene in this tumor type.

Alleles↗
PubMed1992

Mutations of the Ki-ras oncogene in endometrial carcinoma.

OBJECTIVE: The purpose of this study was to assess the extent of involvement of the ras oncogene in endometrial carcinoma. STUDY DESIGN: Genomic deoxyribonucleic acid from 30 samples of endometrial carcinoma was examined for point mutations in codons 12, 13, and 61 from the Ha-ras, Ki-ras, and N-ras genes by means of the polymerase chain reaction, slot-blotting, and deoxyribonucleic acid sequencing procedures. RESULTS: An apparent somatic mutation of Ki-ras codon 12 in one of 10 paraffin-embedded tumors was confirmed by deoxyribonucleic acid sequence analysis. Two of 20 frozen endometrial carcinoma specimens were also shown to contain a point mutation in Ki-ras codon 12. No correlation between ras mutation and a number of histologic or clinical parameters was observed. CONCLUSIONS: These data suggest a potential role for Ki-ras codon 12 mutations in the development of some (10%) endometrial cancers.

Cloning, Molecular↗
PubMed1991

Comparison of the digital rectal examination, endorectal ultrasound, and body coil magnetic resonance imaging in the staging of adenocarcinoma of the prostate.

A series of 25 patients with biopsy proven adenocarcinoma of the prostate underwent preoperative staging evaluation with a digital rectal examination, endorectal ultrasound, and body coil magnetic resonance imaging (MRI) before their radical retropubic prostatectomy. The sensitivity and specificity of the digital rectal examination for the detection of extracapsular disease were 17 and 100%, respectively. The sensitivity and specificity of endorectal ultrasound for the detection of extracapsular disease were 35 and 89%, respectively. The sensitivity and specificity of body coil MRI for the detection of extracapsular disease by adenocarcinoma of the prostate were 47 and 63%, respectively. Microscopic disease of the capsule and seminal vesicles was the principle reason for understaging by both imaging modalities. This small series suggests that both imaging modalities are marginally more sensitive, albeit less specific, for extracapsular disease of the prostate than the digital rectal examination, with ultrasound having a slight edge in specificity and MRI having a slight edge in sensitivity.

Adenocarcinoma↗
PubMed1991

Preoperative prediction of pathological tumor volume and stage in clinically localized prostate cancer: comparison of digital rectal examination, transrectal ultrasonography and magnetic resonance imaging.

Accurate preoperative staging is important for proper selection of patients for radical retropubic prostatectomy. Preoperative staging by digital rectal examination, transrectal ultrasound, magnetic resonance imaging (MRI), Gleason grade and prostate specific antigen was compared to pathological stage for 25 patients who underwent radical retropubic prostatectomy. The predictive value for tumor confinement was 36% by rectal examination, 37% by ultrasound and 30% by MRI. The predictive value for extracapsular disease was 100% by rectal examination, 83% by ultrasound and 66% by MRI. Preoperative determinations of tumor volume by any modality did not correlate with pathological tumor volume. Digital rectal examination, ultrasound and MRI clinically understage the disease in most patients but they may be reliable to predict extracapsular disease.

Aged↗
PubMed1991

Systemic idiopathic fibrosis with T-cell receptor gene rearrangement.

A case of systemic idiopathic fibrosis was analyzed by Southern blotting with probes to the immunoglobulin heavy chain and T-cell receptor genes. A 45-year-old man presented with bilateral neck swelling. He later developed lower back pain, and findings on a computed tomographic scan were consistent with idiopathic retroperitoneal fibrosis. A biopsy specimen of a neck lesion showed morphologic characteristics typical of idiopathic fibrosing cervicitis. Immunophenotyping of the lesion revealed a polymorphic lymphoid population. Molecular analysis with the use of probes to the immunoglobulin and T-cell receptor genes disclosed a germline DNA pattern for the immunoglobulin gene and a rearranged pattern for the T-cell receptor gene.

Antibodies, Monoclonal↗
PubMed1990

Bcr/abl recombinant DNA analysis versus karyotype in the diagnosis and therapeutic monitoring of chronic myeloid leukemia.

Karyotype and bcr/abl recombinant DNA analyses are two means of detecting the chromosomal aberration in chronic myeloid leukemia. The authors compared these two methods in a retrospective study of 36 patients with CML in which they found the bcr/abl DNA recombinant event in 100% (29 of 29) of those patients who had the Philadelphia chromosome. To achieve this sensitivity, a battery of two bcr probes and three restriction enzymes is necessary. The authors propose a sequential algorithm for efficient use of these probes and enzymes. In 76% of the patients, bcr/abl rearrangement can be detected with a Bgl II digest and a 3' commercial probe. An additional 21% of patients can be detected by a second assay in which the same membrane is rehybridized to a 3' and 5' combination bcr probe. One patient (3%) required an additional restriction enzyme digest with BamH I to detect the recombinant event by the same 3' probe. Karyotype analysis is used to determine cytogenetic remission in patients with CML under therapy. The authors studied the use of DNA analysis by the Southern blot technique to detect a decrease in the relative number of leukemic cells. By dilution studies and densitometric scanning of autoradiographs, the authors were able to detect a 15% decrease in the relative number of cells having the bcr/abl recombinant event. The authors report the preliminary results of three patients in whom they compared the karyotype and recombinant DNA analysis at multiple time points in their clinical course. In conclusion, the bcr/abl recombinant DNA analysis is superior to karyotype for the diagnosis of CML and can be used for monitoring treated patients.

Adolescent↗