Search PubMed⌕ Search

Biomedical subjects

R C Strange

Publications and source records attributed to R C Strange.

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

Identification of polymorphism at the glutathione S-transferase, GSTM3 locus: evidence for linkage with GSTM1*A.

Allelism in the glutathione S-transferase, GSTM3 gene has been identified using PCR with specific primers to exon 6/exon 7. Sequencing showed the mutant GSTM3*B allele to have a three-base deletion in intron 6 with a frequency of 0.158. The mutation generates a recognition sequence, 5'-AAGATA-3', for the negative transcription factor YY1. GSTM3*B was significantly associated with GSTM1*A.

Base Sequence↗
PubMed1995

Polyadenylation polymorphism in the acetyltransferase 1 gene (NAT1) increases risk of colorectal cancer.

Exposure to carcinogens present in the diet, cigarette smoke, or the environment may be associated with increased risk of colorectal cancer. Aromatic amines (aryl- and heterocyclic) are a class of carcinogens that are important in these exposures. These compounds can be N- or O-acetylated by the NAT1 or NAT2 enzymes, resulting in activation or in some cases detoxification. Recent studies have shown that both NAT2 and NAT1 genes exhibit variation in human populations and that rapid acetylation by the NAT2 enzyme may be a risk factor for colorectal cancer. In this study we have analyzed for genetic polymorphism in both NAT1 and NAT2 in a group of 202 colorectal cancer patients and 112 control subjects from Staffordshire, England. We find significantly increased risk (odds ratio, 1.9; 95% confidence interval, 1.2-3.2; P = 0.009) associated with the NAT1*10 allele of NAT1, an allele that contains a variant polyadenylation signal. Individuals with higher stage tumors (Duke's C) were more likely to inherit this variant allele (odds ratio, 2.5; 95% confidence interval, 1.3-4.7; P = 0.005). In contrast, rapid acetylation genotypes of NAT2 were not a significant risk factor in this English population. However, we found that the risk associated with the NAT1 variant allele (NAT1*10) was most apparent among NAT2 rapid acetylators (odds ratio, 2.8; 95% confidence interval, 1.4-5.7; P = 0.003), suggesting a possible gene-gene interaction between NAT1 and NAT2 (test for interaction; P = 0.12). This is the first study to test for cancer risk associated with the NAT1 gene, and these positive findings suggest that NAT1 alleles may be important genetic determinents of colorectal cancer risk.

Adenocarcinoma↗
PubMed1995

P53 protein accumulates in Cushings adenomas and invasive non-functional adenomas.

The p53 protein, a negative regulator of cell growth, plays an important role in the pathogenesis of many human tumours following gene mutation and/or deletion. We screened a large number of sporadic pituitary tumours for p53 protein accumulation suggestive of gene mutation. Samples were divided into benign adenomas (n = 95) and invasive tumours with local or distant invasion (n = 26). All main tumour classes were represented. Putative p53 mutations were detected by immunohistochemistry on paraffin-embedded sections using polyclonal CM-1 and monoclonal DO-7 and PAb1801 antibodies. Results were compared to normal post-mortem pituitary tissue controls (n = 17). p53 protein accumulation was detected in invasive tumours (16%), but only in corticotrophinomas (2/4) and non-functional tumours (4/15). In non-invasive adenomas, protein accumulation was observed only in ACTH-secreting tumours where 50% were positive (16/32). No protein accumulation was identified in any control tissue. These results indicate that p53 protein accumulation may play a role in the development of Cushings adenomas and in the progression of non-functional tumours to the invasive state.

Adenoma↗
PubMed1995

Potential contribution of the glutathione S-transferase supergene family to resistance to oxidative stress.

The glutathione S-transferase (GST) supergene family comprises gene families that encode isoenzymes that are widely expressed in mammalian tissue cytosols and membranes. Both cytosolic (particularly the isoenzymes encoded by the alpha, mu and theta gene families) and microsomal GST catalyse the conjugation of reduced glutathione (GSH) with a wide variety of electrophiles which include known carcinogens as well as various compounds that are products of oxidative stress including oxidised DNA and lipid. Indeed, several lines of evidence suggest certain of these isoenzymes play a pivotal role in protecting cells from the consequences of such stress. An assessment of the importance of these GST in humans is presently difficult however, because the number of alpha and theta class genes is not known and, the catalytic preferences of even identified isoforms is not always clear.

Animals↗
PubMed1995

Metabolic polymorphisms and cancer susceptibility.

The vast majority of cancers arise as a consequence of exposure to environmental agents that are toxic or mutagenic. In response to this, all higher organisms have evolved complex mechanisms by which they can protect themselves from environmental challenge. In many cases, this involves an adaptive response in which the levels of expression of enzymes active in the metabolism and detoxification of the foreign chemical are induced. The best characterized of these enzyme systems are the cytochrome P450s, the GSTs and the NATs. An unfortunate consequence of many of these reactions, however, is the creation of a toxic or mutagenic reaction product from chemicals that require metabolic activation before realizing their full carcinogenic potential. Altered expression of one or more of these drug metabolizing enzymes can therefore be predicted to have profound toxicological consequences. Genetic polymorphisms with well defined associated phenotypes have now been characterized in P450, GST and NAT genes. Indeed, many of these polymorphisms have been associated with decreased or increased metabolism of many tumour promoters and chemical carcinogens and hence offer protection against or increased susceptibility to many distinct tumour types.

Animals↗
PubMed1994

Glutathione S-transferase GSTM1 phenotypes and protection against cutaneous tumours.

Multiple allelism at loci encoding detoxicating enzymes is associated with cancer risk. We have studied genetic variation at the glutathione S-transferase GSTM1 locus to see whether phenotypes confer altered susceptibility to basal cell carcinoma (BCC), squamous cell carcinoma (SCC), malignant melanoma (MM), or multiple skin tumours of different histological types. The frequency of GSTM1 null in cases and controls (52%) was similar, except for patients with two or more tumours of different types (71%, p = 0.033). GSTM1 A/B was reduced in frequency (p < 0.05) in patients with single or multiple BCC. Thus GSTM1 A/B may be protective, and effectiveness of detoxication may be a factor determining susceptibility to skin cancer.

Aged↗
PubMed1994

Progression of cervical intraepithelial neoplasia to cervical cancer: interactions of cytochrome P450 CYP2D6 EM and glutathione s-transferase GSTM1 null genotypes and cigarette smoking.

The factors that determine progression of cervical intraepithelial neoplasia (CIN) to squamous cell carcinoma (SCC) are unknown. Cigarette smoking is an independent risk factor for cervical neoplasia, suggesting that polymorphism at detoxicating enzyme loci such as cytochrome P450 CYP2D6 and glutathione S-transferase GSTM1 may determine susceptibility to these cancers. We have studied the frequencies of genotypes at these loci in women suffering low-grade CIN, high-grade CIN and SCC. A non-cancer control group was provided by women with normal cervical histology suffering menorrhagia. Comparison of the frequency distributions of the CYP2D6 PM, HET and EM genotypes (G-->A transition at intron 3/exon 4 and base pair deletion in exon 5) revealed no significant differences between the menorrhagia and SCC groups. Frequency distributions in the menorrhagia group, however, were significantly different (P < 0.04) from those in the low- and high-grade CIN groups. Thus, the proportion of EM was significantly larger (P < 0.03) and of HET generally lower. We found that the frequency of GSTM1 null in the menorrhagia and case groups was not significantly different. Interactive effects of enzyme genotypes with cigarette smoking were studied by comparing the multinomial frequency distributions of CYP2D6 EM/GSTM1 null/smoking over mutually exclusive categories. These showed no significant differences between the menorrhagia group and SCC or low-grade CIN groups. The frequency distribution in high-grade CIN, however, was significantly different to that in the menorrhagia group and in both SCC and low-grade CIN groups. This study was identified, for the first time, an inherited characteristic in women with high-grade CIN who appear to be at reduced risk of SCC. Thus, women with CYP2D6 EM who smoke have increased susceptibility to high-grade CIN but are less likely to progress to SCC, possibly because they effectively detoxify an unidentified chemical involved in mediating disease progression.

Adult↗
PubMed1994

p53 Protein accumulates in Cushings adenomas and invasive non-functional adenomas.

The p53 protein, a negative regulator of cell growth, plays an important role in the pathogenesis of many human tumours following gene mutation and/or deletion. We screened a large number of sporadic pituitary tumours for p53 protein accumulation suggestive of gene mutation. Samples were divided into benign adenomas (n = 95) and invasive tumours with local or distant invasion (n = 26). All main tumour classes were represented. Putative p53 mutations were detected by immunohistochemistry on paraffin-embedded sections using polyclonal CM-1 and monoclonal DO-7 and PAb1801 antibodies. Results were compared to normal post-mortem pituitary tissue controls (n = 17). p53 protein accumulation was detected in invasive tumours (16%), but only in corticotrophinomas (2/4) and non-functional tumours (4/15). In non-invasive adenomas, protein accumulation was observed only in ACTH-secreting tumours where 50% were positive (16/32). No protein accumulation was identified in any control tissue. These results indicate that p53 protein accumulation may play a role in the development of Cushings adenomas and in the progression of non-functional tumours to the invasive state.

Adenoma↗
PubMed1993

Use of site-directed mutagenesis of allele-specific PCR primers to identify the GSTM1 A, GSTM1 B, GSTM1 A,B and GSTM1 null polymorphisms at the glutathione S-transferase, GSTM1 locus.

We describe the identification of the GSTM1 null, GSTM1 A, GSTM1 B and GSTM1 A,B polymorphisms at the glutathione S-transferase GSTM1 locus using a single-step PCR method. Target DNA was amplified using primers to intron 6 and exon 7 with site-directed mutagenesis being used to introduce a restriction site in DNA amplified from GSTM1 *A, thereby allowing differentiation of this allele and GSTM1 *B. The accuracy of this approach in identifying the GSTM1 A, GSTM1 B, GSTM1 A,B and GSTM1 null polymorphisms was confirmed by comparison with, firstly, an established PCR method that distinguishes GSTM1 *0 homozygotes from individuals with the other GSTM1 genotypes and, secondly, GSTM1 phenotypes determined using chromatofocusing.

Alleles↗
PubMed1993

Localisation of alpha, mu and pi class glutathione S-transferases in kidney: comparison with CuZn superoxide dismutase.

We describe studies in whole kidney, cortical and medullary homogenates and, glomerular cells in culture to determine the relative levels of expression of alpha (Ya, Yc, Yk), mu (Yb1/Yb2), pi (Yf) glutathione S-transferases (GST) and CuZn superoxide dismutase (CuZn SOD) in different regions of the nephron. Immunoblotting and immunohistochemistry were used to demonstrate relatively weak expression of alpha, mu GST and, CuZn SOD in the glomerulus compared to that in particularly distal tubules. Whilst expression of Ya was found within glomerular cells, Yc, Yk and Yf were not detected. Immunofluorescence showed that Ya and Yb1/Yb2 but not Yf were expressed in cultured epithelial and mesangial cells studied between passages 1 and 3. While Ya was distributed in cytosol, Yb1/Yb2 was primarily located in nuclei.

Animals↗
PubMed1993

Interactions of hydrogen peroxide with interleukin-6 and platelet-derived growth factor in determining mesangial cell growth: effect of repeated oxidant stress.

1. This study examined the influence of H2O2, interleukin-6 and platelet-derived growth factor on the proliferation of rat mesangial cells. Mesangial cells were exposed to either a single pulse or three daily pulses of H2O2 (10(-8)-10(-4) mol/l), alone or in combination with interleukin-6 (5 ng/ml) and/or platelet-derived growth factor (10 ng/ml). Proliferation was assessed after 24 h and 72 h of incubation using [3H]thymidine incorporation and cell counts. 2. Although one pulse of H2O2 had no significant effect on mesangial cell proliferation, three daily pulses of 10(-6) mol/l H2O2 resulted in a significant increase in [3H]thymidine incorporation of 31 (52.6, 10.3)% (median and 75th-25th interquartile range) (P < 0.001). Both interleukin-6 and platelet-derived growth factor were also mitogenic to mesangial cells, [3H]thymidine incorporation increasing by 19 (36.7, -6.7)% (P < 0.05) and 53.5 (107, 21.9)% (P < 0.001), respectively. The mitogenic effect of interleukin-6 was enhanced by 10(-6) mol/l H2O2 [49.9 (77.7, 12.3)%] (P < 0.01), whereas the addition of 10(-6) mol/l H2O2 to platelet-derived growth factor resulted in a summated increase in [3H]thymidine incorporation of 82.7 (113, 57.4)% (P < 0.001). Incubation with all three substances simultaneously resulted in down-regulation of growth compared with H2O2 plus platelet-derived growth factor by 55.4 (77.7, 10.3)% (P < 0.05). 3. These findings suggest that reactive oxygen species may play a major role in determining the mesangial cell proliferation that occurs in certain forms of glomerulonephritis, acting either alone or in combination with other growth factors.

Animals↗
PubMed1993

The glutathione S-transferases: polymerase chain reaction studies on the frequency of the GSTM1 0 genotype in patients with pituitary adenomas.

The frequency of the GSTM1 0 polymorphism at the glutathione S-transferase M1 locus has been determined in controls and patients with pituitary adenomas by using the polymerase chain reaction to amplify genomic DNA in the exon 4-5 region of the gene. The frequency of the genotype in patients with prolactinomas, non-functional adenomas, corticotrophinomas and somatotrophinomas varied between 52-67% compared with 44% in the controls. In the patients with prolactinomas the frequency of the genotype (67%) was significantly greater than in controls with odds ratio analysis indicating that GSTM1 0 individuals have a 2.56-fold greater risk of developing this adenoma.

Adenoma↗
PubMed1993

GSTM1 null polymorphism at the glutathione S-transferase M1 locus: phenotype and genotype studies in patients with primary biliary cirrhosis.

Studies were carried out to test the hypothesis that the GSTM1 null phenotype at the mu (mu) class glutathione S-transferase 1 locus is associated with an increased predisposition to primary biliary cirrhosis. Starch gel electrophoresis was used to compare the prevalence of GSTM1 null phenotype 0 in patients with end stage primary biliary cirrhosis and a group of controls without evidence of liver disease. The prevalence of GSTM1 null phenotype in the primary biliary cirrhosis and control groups was similar; 39% and 45% respectively. In the primary biliary cirrhosis group all subjects were of the common GSTM1 0, GSTM1 A, GSTM1 B or GSTM1 A, B phenotypes while in the controls, one subject showed an isoform with an anodal mobility compatible with it being a product of the putative GSTM1*3 allele. As the GSTM1 phenotype might be changed by the disease process, the polymerase chain reaction was used to amplify the exon 4-exon 5 region of GSTM1 and show that in 13 control subjects and 11 patients with primary biliary cirrhosis, GSTM1 positive and negative genotypes were associated with corresponding GSTM1 expressing and non-expressing phenotypes respectively. The control subject with GSTM1 3 phenotype showed a positive genotype.

Base Sequence↗
PubMed1993

Alpha, mu and pi class glutathione S-transferases in human synovium and cultured synovial fibroblasts: effects of interleukin-1 alpha, hydrogen peroxide and inhibition of eicosanoid synthesis.

We describe expression of alpha, mu and pi class glutathione S-transferase (GST) and, CuZn- and Mn superoxide dismutase (SOD) in human synovium and cultured synovial fibroblasts. Immunohistochemical and immunoblotting studies showed synovium and cultured cells expressed pi GST and both isoforms of SOD. Cellular localisation was largely perinuclear. No expression of alpha or mu GST was detected even though polymerase chain reaction analysis showed 4/6 subjects had positive genotypes at the polymorphic, mu class GSTM1 locus. Incubation of cultured synovial fibroblasts with H2O2, IL-1 alpha and the cyclooxygenase and lipoxygenase inhibitor, Tenidap, did not induce expression of alpha, mu or pi GST though treatment with IL-1 alpha caused a marked increase in the expression of Mn SOD.

Arthritis, Rheumatoid↗