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Biomedical subjects

R A Walker

Publications and source records attributed to R A Walker.

At least 91 records · Page 5Linked to original sources
PubMed1996

Allelic imbalance in the region of the BRCA1 gene in ductal carcinoma in situ of the breast.

Thirty-four cases of ductal carcinoma in situ (DCIS) of the breast, with or without associated benign or invasive disease, were analysed for allelic imbalance (AI) in the region of the BRCA1 gene. AI on 17q12-23 in DCIS was demonstrated in 74% of cases, and in the majority of cases the region of AI included the BRCA1 gene. However, two cases showed AI distal to BRCA1, supporting the presence of a second tumour-suppressor gene on 17q.

Alleles↗
PubMed1996

Microsatellite instability in early sporadic breast cancer.

We have studied the incidence of microsatellite instability at three trinucleotide repeats and seven dinucleotide repeats from five chromosomal regions, in a group of 30 mammographically detected 'early' invasive breast cancers and correlated its occurrence with clinicopathological parameters. The myotonic dystrophy (DM-1) trinucleotide repeat was analysed in 48 additional cases. In 4 out of 78 (5%) paired tumour-normal DNA samples we found evidence of somatic microsatellite instability at DM-1: a novel allele of a different size was seen in the tumour DNA which was not present in the normal DNA sample. All four tumours that showed evidence of instability were from the core group of 30 cases (13%) and were well or moderately differentiated, oestrogen receptor-positive, infiltrating ductal carcinomas. Two of these tumours were unstable at nine of ten loci studied, both trinucleotide and dinucleotide repeats. DNA prepared from different normal tissues showed no evidence of instability, for all four instability cases. These data indicate that microsatellite instability is specific to the tumour DNA and is an early event in the genesis of some sporadic breast cancers.

Breast Neoplasms↗
PubMed1996

E-cadherin relates to EGFR expression and lymph node metastasis in primary breast carcinoma.

Expression of the calcium-dependent cell-cell adhesion molecule E-cadherin has been examined in 187 primary breast carcinomas using an immunohistochemical technique. The pattern and extent of reactivity has been correlated with clinicopathological data including tumour type, grade and lymph node status and with other prognostic parameters including oestrogen receptor (ER) status, expression of c-erbB-2, pS2 protein and epidermal growth factor receptor (EGFR). Two patterns of E-cadherin staining were observed in carcinomas, membrane reactivity and a diffuse cytoplasmic staining. A marked difference in expression of E-cadherin was observed between infiltrating lobular carcinomas (ILC) and infiltrating ductal carcinomas (IDC), the former showing complete loss of membrane staining, whereas 93% of IDC retained some level of expression. In IDC reactivity was not related to tumour grade but there was a significant association between reduced membrane levels of E-cadherin and the presence of lymph node metastasis, and a highly significant correlation between the presence of cytoplasmic E-cadherin and metastasis. A significant relationship was also demonstrated between reduced E-cadherin reactivity and expression of EGFR. These findings emphasise the complexity of control of E-cadherin in breast carcinomas and provide evidence of a link between membrane signalling pathways and modulation of E-cadherin expression.

Breast Neoplasms↗
PubMed1996

Mutation of the TP53 gene and allelic imbalance at chromosome 17p13 in ductal carcinoma in situ.

A panel of 36 cases of preinvasive breast lesions, including 35 cases of ductal carcinoma in situ (DCIS), has been examined for mutation of TP53, allelic imbalance (AI) on 17p13, and expression of TP53, in a number of cases, has been studied using immunohistochemistry. Areas of DCIS, with or without adjacent invasive or benign cells, have been separately microdissected from paraffin-embedded sections and analysed by PCR for genetic changes to chromosome 17p13. TP53 mutations and AI on 17p have been identified in cases of 'pure' DCIS as well as those with associated invasive carcinoma and, furthermore, have been identified in well-differentiated lesions as well as poorly differentiated ones.

Alleles↗
PubMed1996

Breast carcinomas occurring in young women (< 35 years) are different.

One hundred and sixty-three breast carcinomas occurring in women aged between 26 and 44 years were examined for pathological features, oestrogen and progesterone receptor status, proliferation as determined by Ki-67 labelling and the presence of c-erbB-2 and p53 protein, and were compared with a control group of carcinomas from women in the 50-67 years age group. Carcinomas occurring in women aged under 35 years had a significantly high incidence of being poorly differentiated and of having high proliferation rates. This group also had a significantly high incidence of p53 protein staining. Carcinomas in the under 30 years age group had a lower incidence of oestrogen and progesterone receptor positivity. No differences were found in c-erbB-2-positive staining between the groups. Infiltrating lobular carcinomas were only identified in women aged 40 years and over. There was a higher incidence of a family history in the 35-44 years age group (18%) than in the under 35 years age group (11%). Breast carcinomas occurring in women aged under 35 years are more aggressive. An important finding is the high incidence of p53 positivity, which may indicate genetic instability.

Adult↗
PubMed1996

Effect of off-site transportation on detection of Neisseria gonorrhoeae in endocervical specimens.

OBJECTIVES: To evaluate both the effect of off-site transportation on detection of Neisseria gonorrhoeae in cultured endocervical specimens and the impact of transportation on viability of N. gonorrhoeae by comparison of culture with a nucleic acid probe assay. DESIGN: Three endocervical swabs were randomly collected; one was tested on-site using a nucleic acid-based assay (PACE 2NG System, Gen-Probe, Inc, San Diego, Calif), one was tested off-site following inoculation to modified Thayer-Martin agar (Remel, Lenexa, Kan), and a third swab was tested on-site by culture isolation. A nucleic acid amplification assay of the original swab for PACE 2NG testing was used to resolve discrepancies. SETTING: The emergency department of a university medical center. PATIENTS: Four hundred two patients were evaluated. The test population consisted of both asymptomatic and symptomatic patients. MAIN OUTCOME MEASURE: Positivity for N. gonorrhoeae by one or more of the test procedures, with discrepancy analysis when warranted. RESULTS: Of 402 specimens evaluated, the sensitivities for on-site and off-site testing using culture isolation for N. gonorrhoeae were 88.9% and 77.8%, respectively, in a population prevalence of 6.7%. However, the sensitivity for on-site PACE 2NG testing for N. gonorrhoeae was 96.3%. CONCLUSIONS: A decrease in sensitivity between on-site and off-site culture was found, which suggested transportation may have an adverse effect on the detection of N gonorrhoeae. However, with the limited population and prevalence, the difference was not found to be statistically significant. Further studies indicated that the nucleic acid probe assay was significantly more sensitive (P = .05) when compared with off-site testing using a culture isolation method, demonstrating that viability is an important consideration. These results suggested that a molecular probe assay should be considered in testing specimens for N. gonorrhoeae, especially when the specimen is to be transported off-site.

Bacteriological Techniques↗
PubMed1995

ncd and kinesin motor domains interact with both alpha- and beta-tubulin.

Motor domains of the Drosophila minus-end-directed microtubule (MT) motor protein ncd, were found to saturate microtubule binding sites at a stoichiometry of approximately one motor domain per tubulin dimer. To determine the tubulin subunit(s) involved in binding to ncd, mixtures of ncd motor domain and MTs were treated with the zero-length cross-linker 1-ethyl-3-(3-dimethylaminopropyl-carbodiimide) (EDC). EDC treatment generated covalently cross-linked products of ncd and alpha-tubulin and of ncd and beta-tubulin, indicating that the ncd motor domain interacts with both alpha- and beta-tubulin. When the Drosophila kinesin motor domain protein was substituted for the ncd motor domain, cross-linked products of kinesin and alpha-tubulin and of kinesin and beta-tubulin were produced. EDC treatment of mixtures of ncd motor domain and unassembled tubulin dimers or of kinesin motor domain and unassembled tubulin dimers produced the same motor-tubulin products generated in the presence of MTs. These results indicate that kinesin family motors of opposite polarity interact with both tubulin monomers and support a model in which some portion of each protein's motor domain overlaps adjacent alpha- and beta-tubulin subunits.

Animals↗
PubMed1995

Frequent alterations of chromosome 1 in ductal carcinoma in situ of the breast.

Ductal carcinoma in situ (DCIS) of the breast is commonly described as a premalignant lesion. Using PCR to amplify DNA from areas of tumour cells which have been microdissected from fixed material, we have studied the involvement of chromosome 1 in 19 cases of DCIS. A series of microsatellite repeat polymorphisms has been used to define regions of allelic imbalance and this has confirmed the involvement in DCIS of six of the regions previously implicated in studies of invasive breast tumours. This suggests that these regions may harbour tumour suppressor genes, the inactivation of which is important for the early stages of breast tumour development. Analysis of separate ducts from within the same tumour has revealed that the same genetic alterations are not necessarily present throughout the lesion. In addition we have found that in three cases where frank invasive carcinoma is also present, similar alterations can be detected in the in situ and invasive component.

Breast Neoplasms↗
PubMed1995

Determination of transforming growth factor beta 1 mRNA expression in breast carcinomas by in situ hybridization.

The expression of transforming growth factor beta 1 (TGF-beta 1) mRNA has been determined in 16 breast carcinomas using in situ hybridization and compared with TGF-beta protein as detected by antibodies against TGF-beta 1 and TGF-beta 1 plus TGF-beta 2. Digoxigenin-labelled riboprobes were used, with alkaline phosphatase and immunogold silver detection systems. TGF-beta 1 mRNA was only detected in carcinomas in which TGF-beta 1 protein was found (9 of 16 cases) and not in those with prominent reactivity for TGF-beta 2. RNA preservation was poor in two other cases in which TGF-beta 1 protein had been detected. In general, those tumours with greater numbers of cells labelled for TGF-beta 1 mRNA had prominent reactivity for TGF-beta 1 protein. The mRNA was localized to cancer cells with no labelling of stromal cells, although in a small number of cases scanty staining for TGF-beta 1 protein had been observed in stromal cells. The incidence of detection of TGF-beta 1 mRNA is lower than the published data from Northern analysis studies of breast carcinomas, suggesting that only higher levels of TGF-beta 1 mRNA expression are being detected by in situ hybridization. However, this approach has provided useful information about the cellular sites of expression of TGF-beta 1 in breast carcinomas.

Biomarkers, Tumor↗
PubMed1995

Pathological and biological features of mammographically detected invasive breast carcinomas.

The pathological and biological features of a consecutive series of impalpable invasive breast carcinoma, detected by mammography in the prevalent round of the breast screening programme, have been compared with a clinically presenting group of carcinomas in age-matched patients. There was a significantly higher prevalence of tubular carcinomas as well-differentiated infiltrating ductal carcinomas in the mammographically detected group, and a lower prevalence of poorly differentiated infiltrating ductal carcinomas. Lymph node metastasis was found in 6.5% of the impalpable group compared with 53% of the clinical group. The prevalence of oestrogen receptor was much higher in the impalpable group (96%) than in the control group (67%), although there were no significant differences for progesterone receptor. The prevalence of pS2 was also much higher in the impalpable group, as was cathepsin D. This finding is surprising in view of the reported relationship between cathepsin D and poorer survival. p53 and c-erb-2 proteins were detectable in fewer impalpable carcinomas. The mean MIBI (Ki-67) index was lower in the impalpable group (11.6) than in the clinical group (15.25). Within the mammographically detected group there was a significant difference in the MIBI index between tubular carcinomas and the different grades of infiltrating ductal carcinomas, with a wide range in each category but no association with size. The impalpable carcinomas detected by mammography differ from clinically presenting carcinomas in many ways, raising the question of whether a proportion or all would progress (dedifferentiate) with time.

Aged↗
PubMed1995

Monoclonal antibody LU-BCRU-G7 against a breast tumour-associated glycoprotein recognizes the disaccharide Gal beta 1-3GlcNAc.

The monoclonal antibody LU-BCRU-G7, that was generated by in vitro immunization, shows clinical value as a prognostic marker in early stage breast carcinoma. It has now been characterized with regard to its binding epitope. Using a recently described method based on the construction of N-substituted polyacrylamide (PAA) derivatives of carbohydrates (pseudopolysaccharides), the structure of the epitope for the monoclonal antibody LU-BCRU-G7 has been determined. Competitive binding assays and inhibitory enzyme-linked immunosorbent assays (ELISAs) using these pseudopolysaccharides have shown the LU-BCRU-G7 epitope to be a disaccharide Gal beta 1-3GlcNAc (Lec; where Gal is D-galactose, Glc is D-glucose and GlcNAc is N-acetyl-D-glucosamine). Both galactose and N-acetyl glucosamine moieties are essential for binding. Substitution on C-2 or C-3 of the terminal galactose abolished binding, as did galactose-alpha terminated oligosaccharides. The galactose moiety alone, as expressed by the Gal beta-PAA conjugate, appeared to be a more important feature of the epitope than the GlcNAc-PAA conjugate, which failed to bind or inhibit the LU-BCRU-G7 antibody. In the N-acetyl glucosamine moiety, binding was decreased but not eliminated by fucose substitution, as in Lea, or change in configuration of C-4, as in Gal beta 1-3GlcNAc. Omission of the NAc group resulted in complete loss of activity. The tetrasaccharide lacto-N-tetraose, although containing the terminal Lec disaccharide, does not react with the antibody, suggesting conformational interference of the binding site.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylglucosamine↗
PubMed1995

Evaluation of nucleic acid-based test (PACE 2C) for simultaneous detection of Chlamydia trachomatis and Neisseria gonorrhoeae in endocervical specimens.

A nucleic acid-based test (Gen-Probe PACE 2C System) was evaluated for the ability to detect Chlamydia trachomatis and Neisseria gonorrhoeae from endocervical specimens in a single assay. Three swab samples, randomized for collection order, were obtained from each patient and tested by N. gonorrhoeae and C. trachomatis culture and by the PACE 2C probe assay. Fifty of 395 specimens were culture positive for N. gonorrhoeae (17 specimens), C. trachomatis (26 specimens), or both (7 specimens), of which PACE 2C testing detected 48 specimens. The PACE 2C assay was positive for 56 specimens, including 8 specimens not positive by culture. Of the total of 10 discrepancies between culture and PACE 2C results, resolution testing yielded four false-negative culture, four false-positive PACE 2C, and two false-negative PACE 2C results. The sensitivity, specificity, and positive and negative predictive values for PACE 2C after reevaluation were 96.3, 98.8, 92.9 and 99.4%, respectively. The overall sensitivities for C. trachomatis and N. gonorrhoeae culture were 89.2 and 88.9%, respectively. The prevalence rate for C. trachomatis was 9.4%, and that for N. gonorrhoeae was 6.8%. The Gen-Probe PACE 2C System is a reliable alternative for screening endocervical specimens for both C. trachomatis and N. gonorrhoeae in a single assay.

Cervix Uteri↗
PubMed1994

Prognostic value of a breast cancer-associated glycoprotein detected by monoclonal antibody LU-BCRU-G7.

The immunohistochemical reactivity of a second generation murine monoclonal antibody (LU-BCRU-G7), raised against a novel fucosylated glycoprotein of M(r) 2300,000, has shown a significant association with prognosis of early stage carcinomas. Staining was observed in 72% of the 190 breast carcinomas tested. No relationship with steroid receptor status, stage or node status was found. An association with grade was observed (chi 2 7.83, 2 degrees of freedom, P = 0.02) only when the negative cut-off level was raised from < 10% cells staining to < 25%. Antibody reactivity was always cytoplasmic. Immunoblotting shows the antibody is reactive with a component of M(r) 230,000 not detected by HMFG 2. A significant association was found between lack of reactivity and improved disease-free interval (0.005 > P > 0.001) and survival (0.02 > P > 0.01). Subdivision of cases on the basis of node status showed that staining could refine survival data. A decreased reactivity of LU-BCRU-G7 was observed after pretreatment with beta-galactosidase but not a sialidase or beta-N-acetylhexosaminodase indicating that non-reducing terminal galactose residues in beta 1-3 or beta 1-4 linkages may be involved in the antibody binding site. This approach has identified a useful and novel prognostic marker in early stage human breast carcinoma.

Adenocarcinoma↗
PubMed1994

Relationship of transforming growth factor beta 1 to extracellular matrix and stromal infiltrates in invasive breast carcinoma.

Transforming growth factor beta (TGF-beta) comprises a group of multifunctional regulatory proteins, whose effects include stimulation of extracellular matrix formation and modification of immune function. The presence of TGF-beta 1 and TGF-beta 2 in invasive breast carcinomas has been determined and related to pathological features, the presence of fibronectin and tenascin and lymphocyte/macrophage infiltration, using immunohistochemistry. Differences were observed in the extent of reactivity within the same carcinoma and between tumours stained with an antibody detecting TGF-beta 1 ane one detecting TGF-beta plus TGF-beta 2, the latter having a higher level of reactivity. Prominent reactivity for TGF-beta 1 was associated with lymph node metastasis, (0.02 > P > 0.01), increased detection of cellular fibronectin, fine stromal fibronectin staining, more prominent reactivity for tenascin (0.02 > P > 0.01), the presence of tumour-associated macrophage infiltration and altered ratios of CD4 and CD8 lymphocyte populations, with CD8 lymphocytes predominating. These associations were not observed for carcinomas showing prominent staining with antibody detecting TGF-beta 2 as well as TGF-beta 1. The findings indicate that TGF-beta 1 may have a role in invasion and metastasis of breast carcinomas.

Antibodies↗
PubMed1993

Modulation of cell surface components of human breast cancer cells by retinoic acid: enhanced HLA-DR expression.

The effect of the differentiating agent all-trans-retinoic acid on the expression of components of the milk fat globule membrane and HLA-DR by breast cancer cell lines has been examined. Effects on proliferation were also considered, to determine whether any cell surface changes were related to or independent of proliferation effects. No significant differences were observed in the expression of components detected by the milk fat globule membrane antibodies HMFG1 and HMFG2 over 8 days culture with 10(-7)-10(-9)M retinoic acid for the cell lines MCF-7, T-47 D, ZR-75, MDA-MB-231, and BT-20. In contrast , there was enhanced expression of HLA-DR by two oestrogen receptor-positive cell lines T-47 D and ZR-75 and the oestrogen receptor-negative line MDA-MB-231, with differing sensitivities. These effects were independent of inhibition of proliferation, which was only observed for oestrogen receptor-positive cell lines and for different durations of exposure. The finding of enhanced HLA-DR expression after retinoic acid treatment has not previously been reported and is of interest regarding clinical potential for the induction of tumour immunity.

Antigens, Neoplasm↗
PubMed1993

Expression of the pS2 peptide in primary breast carcinomas: comparison of membrane and cytoplasmic staining patterns.

The pS2 protein is oestrogen-regulated in breast cancer cell lines. Previous studies have shown a relationship to oestrogen receptor in primary breast carcinomas. This study examined 178 breast carcinomas for pS2 using immunohistochemistry. A high frequency (77 per cent) of positive tumours was found, using a 10 per cent cut-off point to define a positive tumour. There was no relationship with menopausal status or node status, a significant association with differentiation, a weak association with oestrogen receptor, and no association with progesterone receptor or overall survival. Two patterns of cellular localization were observed: cytoplasmic and membrane. The former showed a stronger relationship with oestrogen receptor status, although there were oestrogen receptor-negative tumours with marked pS2 staining. Membrane staining showed a stronger relationship with differentiation, with a staining pattern similar to that observed for milk fat globule membrane. The staining patterns observed may support a role for pS2 in a secretory mechanism. However, the expression and function of pS2 in breast carcinomas remain complex, and are not simply related to oestrogen regulation.

Breast Neoplasms↗