Medicine (St Vincent's) - Research Publications
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ItemSerum methotrexate in childhood ALL.(Springer Science and Business Media LLC, 1992-07)
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ItemRAPID UP-REGULATION OF MDR1 EXPRESSION BY ANTHRACYCLINES IN A CLASSICAL MULTIDRUG-RESISTANT CELL-LINE(STOCKTON PRESS, 1995-05)Studies were carried out in a variant human multidrug-resistant (MDR) cell line CEM/A7R, which expresses very low levels of mdr1 mRNA and P-glycoprotein (P-gp). The induction of mdr1 RNA expression by three anthracyclines, (doxorubicin, daunorubicin, epirubicin), VP-16 and two vinca alkaloids (vincristine, vinblastine) was semiquantitatively assessed by scanning Northern blots on a phosphorimager. The relative level of mdr1 expression was expressed as ratio of mdr1 to the internal RNA (actin). A significant increase (P < 0.02) in expression of mdr1 was noted within 4 hrs of exposure to 1.5 micrograms ml-1 daunorubicin or epirubicin. Neither vinblastine nor vincristine had any effect on mdr1 levels after an 8 h exposure. With increasing concentrations of daunorubicin or epirubicin in a fixed 24 h time period, mdr1 expression increased, although a biphasic response was seen. Based on MRK 16 binding, an increase in P-gp levels was seen in the CEM/A7R line after a 24 h exposure to 1 microgram ml-1 daunorubicin or epirubicin. The rapid increase in mdr1 expression after a short period of exposure to doxorubicin, daunorubicin or epirubicin suggests that induction of mdr1 expression may have an important role in the development of drug-resistant tumours.
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ItemAltered expression of the IGF-1 receptor in a tamoxifen-resistant human breast cancer cell line(CHURCHILL LIVINGSTONE, 1999-02)The relationship between oestrogen (E2) and insulin-like growth factor-one (IGF-1) was examined in both tamoxifen-sensitive (MCF 7/5-21) and tamoxifen-resistant (MCF 7/5-23) subclones of the MCF 7 cell line. Both subclones were grown in defined, serum-free (SF) medium over a period of 7 days with the addition of E2 or IGF-1 or a combination of both agents. Growth of both MCF 7/5-21 and 7/5-23 cells was stimulated (245% and 350%, respectively) by E2. However, only the growth of MCF 7/5-23 cells was stimulated (266%) by IGF-1. A combination of E2 and IGF-1 significantly enhanced MCF 7/5-21 and 7/5-23 cell growth (581% and 695%, respectively). E2-induced IGF-1 receptor (IGF-1R) levels (as measured by 125I-IGF-1 binding and Northern analyses) in only MCF 7/5-23 cells. This effect was partially inhibited by tamoxifen. In medium containing serum, the growth of only the MCF 7/5-23 cells was significantly inhibited by the IGF-1R monoclonal antibody, alphaIR-3. The detection of E2-induced expression of IGF-2 using RT-PCR was demonstrated in the MCF 7/5-23 cells. These experiments indicate that E2 may sensitize tamoxifen-resistant MCF 7/5-23 cells to the growth stimulatory actions of IGF-2 via up-regulation of the IGF-1R and describes a cell-survival mechanism that may manifest itself as tamoxifen resistance.
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ItemInduction of MDR1 gene expression by anthracycline analogues in a human drug resistant leukaemia cell line(CHURCHILL LIVINGSTONE, 1999-02)The effects of 4-demethoxydaunorubicin (idarubicin, IDA) and MX2, a new morpholino-anthracycline, on up-regulation of the MDR1 gene in the low-level multidrug resistant (MDR) cell line CEM/A7R were compared at similar concentrations (IC10, IC50 and IC90) over a short time exposure (4 and 24 h). The chemosensitivity of each drug was determined by a 3-day cell growth inhibition assay. Compared with epirubicin (EPI), IDA and MX2 were 17- and eightfold more effective in the CEM/A7R line respectively. No cross-resistance to 5-FU was seen in the CEM/A7R line. Verapamil (5 microM) and PSC 833 (1 microM), which dramatically reversed resistance to EPI in the CEM/A7R line, had no sensitizing effect on the resistance of this line to MX2, but slightly decreased resistance to IDA. The sensitivity to 5-FU was unchanged by these modulators. The induction of MDR1 mRNA expression by IDA, MX2 and 5-FU was analysed by Northern blotting and semiquantitatively assessed by scanning Northern blots on a phosphorimager. The relative level of MDR1 expression was expressed as a ratio of MDR1 mRNA to the internal RNA control glyceraldehyde-3-phosphate dehydrogenase (GAPDH). IDA, MX2 and 5-FU differentially up-regulated MDR1 mRNA in the CEM/A7R line in a dose-dependent manner. Both IDA and MX2 induced MDR1 expression within 4 h. 5-FU up-regulated MDR1 expression only when drug exposure was prolonged to 24 h. Based on MRK 16 binding, flow cytometric analysis of P-glycoprotein (Pgp) expression paralleled the increase in MDR1 mRNA levels. For the three anthracyclines, the increase in MDR1 expression was stable in cells grown in the absence of drug for more than 3 weeks after drug treatment. The induction of MDR1 expression by 5-FU was transient, associated with a rapid decrease in the increased Pgp levels which returned to baseline 72 h after the removal of 5-FU. This study demonstrates that MDR1 expression can be induced by analogues of anthracyclines not pumped by Pgp, and that this induction appears to be stable despite a 3-week drug-free period.
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ItemQUALITY OF PHARMACOKINETIC RESEARCH IN ONCOLOGY(STOCKTON PRESS, 1995-09)The usefulness of pharmacokinetically guided individualisation of drug therapy will depend, among other things, on the quality of the analytical and pharmacokinetic methods used. We surveyed the quality of analytical and pharmacokinetics methodology and reporting in a literature search of the oncology literature from 1987 to 1992, using the Medline database. Thirty articles that examined relationships between normal tissue toxicity and area under the plasma concentration-time curve (AUC) formed the study sample. Analytical procedures were adequately described in 77% of the articles, but details of validation of the assay were seriously deficient in the great majority of articles. Methods for calculation of AUC were also deficient in over half of the articles. The findings suggest that greater attention needs to be paid to the quality of pharmacokinetic investigation in oncology, otherwise progress in the use of pharmacokinetically guided individualisation of dosage may be hindered.
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ItemInheritance of chromosome 7 is associated with a drug-resistant phenotype in somatic cell hybrids(STOCKTON PRESS, 1996-01)A major form of drug resistance in tumour cells known as classical multidrug resistance (MDR) is associated with the overexpression of the mdr1 gene product, the membrane protein P-glycoprotein (P-gp), which acts as an energy-dependent drug efflux pump. In this study the inheritance of P-gp expression was examined using hybrids formed after somatic cell fusion between a drug-sensitive human T-cell leukaemia cell line, CEM/CCRF, and a drug-resistant derivative, CEM/A7, which is characterized by a clonal chromosomal duplication dup(7)(q11.23q31.2). Fourteen hybrids, chosen at random, were analysed by reverse transcriptase-polymerase chain reaction (RT-PCR) and by binding studies involving the monoclonal antibody MRK16, which recognises an external P-gp epitope. Only two hybrids were positive for both MRK16 antibody labelling and mdr1 mRNA. Partial karyotypic analysis of all hybrids revealed that only the MRK16-positive hybrids contained the duplication in chromosome 7 seen in the CEM/A7 parental MDR line. Therefore, P-gp overexpression in the MRK16-positive hybrids may be linked to the inheritance of chromosome 7 from CEM/A7 and possibly associated with the chromosome 7 abnormality.
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ItemA phase II study in advanced breast cancer: ZD1694 ('Tomudex') a novel direct and specific thymidylate synthase inhibitor(STOCKTON PRESS, 1996-08)ZD1694 ('Tomudex'), a novel, direct and specific thymidylate synthase (TS) inhibitor, was developed in a collaborative research programme between Zeneca Pharmaceuticals and the Institute of Cancer Research (UK) and entered clinical trials in 1991; phase II studies began in 1992, using 3.0 mg m-2 every 3 weeks as a short 15 min infusion. Forty-six patients entered a phase II study of ZD1694 in advanced breast cancer. A total of 74% of patients had received prior systemic therapy (either as adjuvant cytotoxic or hormonal therapy or hormone therapy for advanced disease); 39% had received prior adjuvant cytotoxic chemotherapy. All patients had measurable disease and 50% had liver metastases. In all 43 patients were evaluable for response. Of these patients 26% achieved complete (CR) or partial response (PR) (95% Cl 14-42%). A response rate of 44% was seen in liver metastases. Two patients achieved CR of 265 and 301 days' duration respectively, one in locoregional disease, and one in liver metastases. The most common grade 3/4 adverse events were nausea and vomiting (11%), diarrhoea (11%) and leucopenia (20%). Grade 3/4, self-limited and reversible increases in transaminases were seen in 22% of patients. ZD1694 has useful single agent activity in patients with hormone-refractory advanced breast cancer, comparable with that reported for other anti-metabolites, with acceptable tolerability.