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Biomedical subjects

A G Hall

Publications and source records attributed to A G Hall.

At least 55 records · Page 3Linked to original sources
PubMed1995

Corticosteroid resistance is increased in lymphoblasts from adults compared with children: preliminary results of in vitro drug sensitivity study in adults with acute lymphoblastic leukaemia.

The prognosis of acute lymphoblastic leukaemia (ALL) in adults is poor compared with children in terms of complete remission (CR) and leukaemia-free survival. In children in vitro resistance of leukaemic cells to various cytotoxic agents is an independent poor prognostic marker, but the relevance of in vitro drug resistance in adults to poor prognosis has not been described. Lymphoblasts from 16 adults and 32 children with ALL at initial presentation were assayed for in vitro drug sensitivity in a short-term culture system using the reduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) as an indicator of cell viability. The following drugs were tested: prednisolone, daunorubicin, mitozantrone, etoposide, melphalan and 6-thioguanine. At initial presentation, lymphoblasts from adults demonstrated a significantly higher degree of in vitro resistance to prednisolone than those from children (P < 0.01). Glucocorticoid resistance may be a fundamental difference between adult and childhood ALL which may underlie different biological aspects and also explain the difference in prognosis. Lymphoblasts from adults who achieved CR were more sensitive in vitro to prednisolone (P = 0.07), daunorubicin (P < 0.05), mitozantrone (P < 0.01) and melphalan (P < 0.05) than cells from those who did not. The MTT assay can predict response to induction chemotherapy in adults and therefore discriminate between standard- and high-risk patients. The assay, however, is not suitable for selection of the most effective agent for treatment because of in vitro cross-resistance of lymphoblasts to various drugs tested.

Adrenal Cortex Hormones↗
PubMed1995

Second primary head and neck squamous cell carcinoma predicted by the glutathione S-transferase expression in healthy tissue in the direct vicinity of the first tumor.

BACKGROUND: Glutathione S-transferases (GST) are known to play a role in the detoxification of carcinogens. Individual isoenzymes of the alpha-, mu-, and pi-class vary in substrate specificities, tissue distribution, and activities among individuals. GST-pi expression has been shown to be increased in preneoplastic and neoplastic lesions. GST-mu is known to play a role in detoxification of epoxides released from cigarette smoke, and individuals with low GST-mu activity have a relatively high risk to develop smoking-related lung and laryngeal cancer. The occurrence of a second primary tumor (SPT) in the whole respiratory and upper aerodigestive tract is an important factor for mortality in head and neck squamous cell carcinoma (HNSCC), and, at present, there are no markers that are available to predict which patient has increased chances of developing an SPT. Risk-assessment by use of biomarkers, particularly the ones that can be obtained with noninvasive techniques, are of great value in predicting prognosis and hence possibly more aggressive treatment and follow-up in selected patient groups. EXPERIMENTAL DESIGN: In a nested case control study, 20 patients who had previous history of oral cancer were used; 10 of the 20 had developed an SPT, and the other 10 patients were minimally 7 years free of disease. The expression of GST-pi, GST-mu, and GST-alpha was immunohistochemically analyzed using apparently normal oral mucosa, free of tumor or dysplasia, obtained from the resection edges around the primary tumor. In another experiment, the three GST isoenzymes were immunohistochemically analyzed using exfoliated cells, obtained noninvasively from several sites of the upper aerodigestive tract of the apparently normal-looking mucosa of HNSCC patients (n = 25) and of control individuals (n = 10). RESULTS: The expression of all GST was significantly higher (p < 0.001) in the suprabasal and superficial layers of the mucosa at risk. Also, in cell scrapes of clinically healthy mucosa of HNSCC patients, we observed a significantly higher expression (p < 0.001) of GST-pi and GST-mu compared with their matched controls. For GST-alpha, we observed a more heterogenous expression pattern in these exfoliated cells. CONCLUSIONS: Expression of GST-pi, -mu, and -alpha in normal tissue in the direct vicinity of the first tumor seems to have predictive value for the development of an SPT.

Adult↗
PubMed1994

Expression of mu class glutathione S-transferase correlates with event-free survival in childhood acute lymphoblastic leukemia.

Expression of the main classes (pi, mu, and alpha) of glutathione S-transferase (GST) was assessed in the blasts of children presenting with acute lymphoblastic leukemia using an immunohistochemical technique. Bone marrow trephine biopsies obtained at presentation from 71 cases were studied (42 boys, 29 girls; age range, 6 months-14 years; median age, 4 years) and expression was correlated with event-free survival. The period of follow-up was 12-108 months, during which time 21 patients (30%) relapsed. All the samples examined were negative for alpha class GST. Samples from 8 patients, all of whom remained in remission at the time of analysis, were found to be negative for pi class GST at presentation. Samples from 44 (patients were negative for mu class GST (62%); of these, 36 patients (82%) remained in remission. In comparison, of the 27 patients who were positive for mu class GST, only 14 (52%) remained in remission. Analysis of event-free survival demonstrated that expression of mu class GST predicts a 3-fold increased risk of relapse (95% confidence interval, 1.25-7.26). This risk factor appears to be independent of other recognized prognostic factors.

Adolescent↗
PubMed1994

Purification of an alpha class glutathione S-transferase from melphalan-resistant Chinese hamster ovary cells and demonstration of its ability to catalyze melphalan-glutathione adduct formation.

We have shown previously that a Chinese hamster ovary cell line (designated CHO-Chlr), generated by exposure to chlorambucil and demonstrating a greater than 20-fold collateral resistance to melphalan, showed increased expression of an alpha form of glutathione S-transferase (GST) associated with amplification of GST genes. Here, we demonstrate that GST purified from CHO-Chlr cells contains a form with a pI of 9, not present in CHO-K1 cells or Chinese hamster liver, which has the ability to accelerate the formation of glutathione-melphalan adducts. This result provides evidence that overexpression of the alpha class GST may be directly responsible for the development of resistance to bifunctional alkylating agents.

Amino Acid Sequence↗
PubMed1994

The relationship between bcl-2 expression and response to chemotherapy in acute leukaemia.

Immunocytochemistry was used to assess bcl-2 expression in blasts obtained from the bone marrow of 28 patients with acute lymphoblastic leukaemia (ALL) (16 children and six adults at presentation and three children and three adults on relapse) and 20 with acute myeloid leukaemia (AML) (19 adults and one child, 13 with de novo AML, 11 at presentation and two on relapse, and seven secondary to myelodysplasia or chronic myeloid leukaemia). Slides were examined both for the percentage of positive cells and for the intensity of staining using a five-point scale. There was a statistically significant increase in both the percentage of positive cells seen (P < 0.002) and the intensity of staining (P < 0.01) between samples obtained at relapse and those at presentation in ALL. There was a significantly greater intensity of staining in cells from patients with ALL (P < 0.05) and AML (P < 0.05) who failed to achieve remission after chemotherapy than in those who responded. The intensity of staining in cases of secondary AML was lower than that in de novo disease (P < 0.01). These results suggest that expression of bcl-2 may be an important prognostic feature in both de novo AML and in ALL, but not in secondary AML.

Adolescent↗
PubMed1994

Glutathione S-transferase in bone marrow metastases of disseminated neuroblastoma.

Antisera to each of the three main cytosolic forms of glutathione S-transferase (GST; alpha, mu, and pi) has been used to characterise GST expression by metastatic neuroblastoma in bone marrow trephine biopsies taken from 15 patients at presentation and from five of this group at relapse. There was no correlation between expression of extra-nuclear alpha or mu GST and outcome, and no consistent pattern at relapse. Seven of eight expressing nuclear pi GST at presentation died of resistant disease. Three of five cases with no detectable nuclear pi class GST remain alive and disease free. The results provide no encouragement for further investigation of alpha or mu GST in this disease but larger studies of uniformly treated patients may show whether nuclear pi GST expression at presentation indicates likely relapse.

Adolescent↗
PubMed1994

Raised intracellular glutathione levels correlate with in vitro resistance to cytotoxic drugs in leukaemic cells from patients with acute lymphoblastic leukemia.

Lymphoblasts were separated from the peripheral blood or bone marrow of 19 children (age 1-15, median 4 years) and 13 adults (age 18-59, median 47 years) with acute lymphoblastic leukaemia (ALL). Twenty-one samples were examined at presentation (16 from children and five from adults) and 13 at relapse (three children and ten adults). Glutathione (GSH) levels in leukaemic blasts were compared with in vitro sensitivity to a variety of cytotoxic drugs assessed using 3-(4-5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) as an indicator of cell viability. There was a statistically significant positive correlation between GSH levels and in vitro sensitivity to daunorubicin (Spearman's rank correlation coefficient rs = 0.38, p < 0.04), melphalan (rs = 0.39, p < 0.04) and prednisolone (rs = 0.48, p < 0.01), but not mitozantrone, etoposide or 6-thioguanine. There was no statistically significant difference in median GSH levels between blasts from children and adults or between samples taken at presentation or relapse. The sample median GSH levels in blasts from patients who responded to therapy (n = 21) and those who did not (n = 7) were 1.05 fmol/cell (97.3% confidence interval (CI) 0.78-1.52) and 2.66 fmol/cell (98.4% CI 0.53-5) respectively, and this difference was statistically significant (p < 0.02, Mann-Whitney U test). In two patients for whom paired samples were available, GSH levels in blasts on relapse were greater than 2-fold higher than on presentation. These results provide evidence that elevation of GSH in leukaemic blasts may be associated with resistance to drugs used in the treatment of children and adults with ALL.

Adolescent↗
PubMed1993

Identification of bovine glutamate dehydrogenase as an RNA-binding protein.

Two RNA binding activities were demonstrated in bovine liver homogenate. One binding protein was isolated by a simple ion exchange and gel filtration protocol and was shown by N-terminal protein sequence analysis to be glutamate dehydrogenase. Using identical RNA substrate and assay conditions, no detectable RNA binding was observed with equimolar amounts of other representative dehydrogenases and proteins. Furthermore, excesses of tRNA, salmon testis DNA, or each of the four homoribopolymers were unable to compete for the RNA-binding site. Total cytosolic RNA, however, successfully prevented binding of radiolabeled RNA substrate. These data are consistent with glutamate dehydrogenase containing a binding site for heteropolymeric RNA with highest affinity for an as yet undefined nucleotide consensus sequence or structure. The potential physiological relevance of these observations is discussed.

Animals↗
PubMed1992

Reduced topoisomerase II and elevated alpha class glutathione S-transferase expression in a multidrug resistant CHO cell line highly cross-resistant to mitomycin C.

We have isolated a multidrug-resistant derivative of Chinese hamster ovary CHO-K1 cells by exposure to progressively increasing concentrations of Adriamycin. This cell line, designated CHO-Adrr, was 27-fold more resistant than the parental line to Adriamycin and showed similar degrees of cross-resistance to several other topoisomerase II (topo II) inhibitors, including mitoxantrone, daunomycin and etoposide. CHO-Adrr cells showed a lower (4-fold) level of cross-resistance to vincristine and colchicine, drugs associated with the multidrug-resistant phenotype. While CHO-Adrr cells showed no enhanced resistance to several mono- and bi-functional alkylating agents or to UV and ionizing radiation, they were greater than 80-fold resistant to mitomycin C (MMC). There was a 5-fold decreased level of daunomycin accumulation in CHO-Adrr cells compared to CHO-K1 cells and this was associated with increased drug efflux. The resistant cells had amplified multidrug resistance gene (mdr) sequences and overexpressed (mdr) mRNA. Verapamil was able to completely reverse Adriamycin resistance but reversal of MMC resistance was only partial, with residual 23-fold resistance. CHO-Adrr cells expressed a 4-fold reduced level of topo II protein but overexpressed an alpha class (basic) glutathione S-transferase (GST). Analysis of cell hybrids showed that while the level of resistance to Adriamycin dropped by a factor of 3 in CHO-K1/CHO-Adrr hybrids compared to CHO-Adrr/CHO-Adrr hybrids, resistance to MMC dropped 10-fold. Thus, CHO-Adrr cells appear to exhibit simultaneously several different drug resistance mechanisms including MDR and GST overexpression, and topo II reduction.

Amsacrine↗
PubMed1992

Immunohistochemical demonstration of glutathione S-transferases in primary human breast carcinomas.

The expression of cytosolic glutathione S-transferase (GST) isoenzymes has been assessed in a series of 74 primary human breast carcinomas using an immunohistochemical method. GST pi was detected in sections from all 74 tumours; it was expressed by non-epithelial (stromal and inflammatory) cells in 62 tumours (84 per cent), but by tumour epithelium in only 35 (47 per cent). Non-neoplastic mammary epithelium was uniformly positive for GST pi. Expression of GST alpha and mu was observed in 19 and 42 per cent of the tumours, respectively, and was largely confined to the neoplastic component. Lack of staining of tumour epithelium for GST pi was significantly associated with poorer tumour differentiation (higher grade). There was no association between expression of any of the three isoenzymes and either menopausal status or expression of c-erbB-2 oncogene protein product. Immunohistochemistry is a useful method for the investigation of expression and cellular localization of GSTs within tumours; such data are needed to improve our understanding of the role of these enzymes in neoplasia and in resistance to cytotoxic drug therapy.

Adult↗
PubMed1992

Mechanisms of action of, and modes of resistance to, alkylating agents used in the treatment of haematological malignancies.

Although the alkylating agents were amongst the first non-hormonal compounds to be shown to be active against malignant cells they still rank as some of the most valuable cytotoxic drugs available for the treatment of patients with leukaemia and lymphoma. Melphalan, chlorambucil, busulfan, cyclophosphamide, ifosfamide and the nitrosoureas are all members of this class of drug, which are believed to exert their cytotoxic effects through the covalent linkage of alkyl groups to DNA. In the first report describing the use of alkylating agents in clinical practice the problem of drug resistance was recognised. In spite of this there is still comparatively little known about the mechanisms underlying the development of resistance as it occurs in patients. Studies using animal models and cell lines have suggested that both cellular and extracellular factors may be involved, but the precise relevance of these to the clinical setting is unclear. A greater understanding of the mode of action and mechanisms of resistance to alkylating agents should enable the development of modulators capable of the restoration of sensitivity to resistant cells, and the more effective use of these well established drugs.

Alkylating Agents↗
PubMed1992

Response to mitoxantrone in advanced breast cancer: correlation with expression of c-erbB-2 protein and glutathione S-transferases.

Sixty-eight patients with advanced breast cancer were treated with mitoxantrone and clinical responses assessed. Expression of c-erbB-2 protein and cytosolic glutathione S-transferase (GST) isoenzymes pi, alpha and mu by the primary tumours of these patients was determined immunohistochemically, and correlated with treatment response. Tumours overexpressing c-erbB-2 (n = 16, 23%) showed a lower response rate (50% vs 58%) and shorter duration of response to treatment, compared with c-erbB-2 negative tumours. These associations were not statistically significant but survival following start of treatment was significantly shorter in the c-erbB-2 positive group. For each GST isoenzyme, the response rate and duration of response of the group showing enzyme expression did not differ significantly from those with negatively staining tumours. These data do not support a role for expression of GSTs alone in resistance to mitoxantrone monotherapy in advanced breast cancer. The poorer post treatment survival of patients with c-erbB-2 positive tumours suggests they could be selected for more intensive treatment regimens.

Adult↗
PubMed1992

Glutathione S-transferases in neonatal liver disease.

AIMS: To investigate the distribution of alpha and pi class glutathione S-transferases (GST) in normal fetal, neonatal, and adult liver; and to examine changes in GST expression in neonatal liver disease. METHODS: alpha and pi class GST were immunolocalised in sections of formalin fixed liver tissue obtained from human fetuses (n = 21), neonates (n = 8), young children (n = 9) and adults (n = 10), and from neonates with extrahepatic biliary atresia (n = 15) and neonatal hepatitis (n = 12). Monospecific rabbit polyclonal antibodies were used with a peroxidase-antiperoxidase method. RESULTS: Expression of pi GST was localised predominantly within biliary epithelial cells of developing and mature bile ducts of all sizes from 16 weeks' gestation until term and in neonatal and adult liver. Coexpression of pi and alpha GST was seen in hepatocytes of developing fetal liver between 16 and 34 weeks' gestation. Although pi GST was seen in occasional hepatocytes up to six months of life, this isoenzyme was not expressed by hepatocytes in adult liver. By contrast, alpha GST continued to be expressed by hepatocytes in adult liver; this isoenzyme was also seen in some epithelial cells of large bile ducts in adult liver. No change was observed in the distribution of alpha GST in either neonatal hepatitis or extrahepatic biliary atresia. However, aberrant expression of pi GST was identified in hepatocytes of all but one case of extrahepatic biliary atresia but in only two cases of neonatal hepatitis. CONCLUSIONS: The phenotypic alterations noted in extrahepatic biliary atresia may result from the effect of cholate stasis. Evaluation of the pattern of pi and alpha GST distribution by immunohistochemical staining may provide valuable information in distinguishing between these two forms of neonatal liver disease.

Adult↗
PubMed1991

Drug resistance mechanisms in leukaemia.

Although considerable advances have been made over the past 20 years in the treatment of leukaemia, many patients still die either of their disease, or of the attempts made to cure it. A major contribution to this unacceptable level of mortality is the presence of drug resistance in the residual leukaemic cells. Although many laboratory studies have been performed which have indicated possible cellular mechanisms for the development of resistance, comparatively little is known of the relevance of these processes to resistance as it occurs in patients. Information from such studies should provide a basis for the rational design of agents capable of reversing resistance, and thereby improving the chances of achieving sustainable remission in the majority of patients presenting with leukaemia.

Antineoplastic Agents↗
PubMed1990

Isolation and partial characterisation of a mammalian cell mutant hypersensitive to topoisomerase II inhibitors and X-rays.

We have isolated, following one-step mutagenesis, a Chinese hamster ovary cell mutant hypersensitive to the intercalating agent, adriamycin (4-fold compared to parental CHO-K1 cells). This agent exerts at least part of its cytotoxic action via inhibition of the nuclear enzyme, topoisomerase II. The mutant, designated ADR-3, showed hypersensitivity to all classes of topoisomerase II inhibitors, including actinomycin D, amsacrine (m-AMSA), etoposide (VP16) and mitoxantrone. ADR-3 cells also showed cross-sensitivity to ionizing radiation, but not to UV light. Cellular accumulation of radiolabeled actinomycin D was similar in parental and mutant cells. At equimolar doses, adriamycin induced more protein-associated DNA single- and double-strand breaks in ADR-3 cells than in CHO-K1 cells. Topoisomerase II activity was elevated to a small but significant degree in ADR-3 cells, and this was reflected in a 1.5-fold higher level of topoisomerase II protein in ADR-3 than in CHO-K1 cells, as judged by Western blotting. ADR-3 cells were hypersensitive to cumene hydroperoxide but cross-resistant to hydrogen peroxide, suggesting possible abnormality in the detoxification of peroxides by glutathione peroxidase or catalase. Glutathione peroxidase activity against hydrogen peroxide was similar in CHO-K1 and ADR-3 cell extracts, but activity against cumene hydroperoxide was evaluated to a small but significant extent in mutant cells. Catalase levels were not significantly different in ADR-3 and CHO-K1 cells. ADR-3 cells were recessive in hybrids with parental CHO-K1 cells with respect to sensitivity to topoisomerase II inhibitors and X-rays, and represent a different genetic complementation group from the previously reported adriamycin-sensitive mutant, ADR-1 [Davies et al., J. Biol. Chem., 263 (1988) 17724-17729].

Animals↗
PubMed1988

Hodgkin's disease involving the large bowel.

A case is described in which Hodgkin's disease occurred in the descending colon and adjacent mesenteric nodes as the only site of relapse. This rare presentation is discussed, with a review of the available literature.

Adult↗