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J Schupp

Publications and source records attributed to J Schupp.

12 recordsLinked to original sources
PubMed2001

Differential degradation rates of inactivated alkyltransferase in blood mononuclear cells and tumors of patients after treatment with O(6)-benzylguanine.

O(6)-Alkylguanine-DNA alkyltransferase (AGT) repairs O(6)-alkylating DNA adducts generated by alkylating therapeutic agents. Therefore, AGT activity may be an important marker of tumor and normal tissue sensitivity to chemotherapeutic agents and a predictor for the success of chemotherapeutic regimens. It is rapidly inactivated by O(6)-benzylguanine (BG) that mimics its substrates, O(6)-methylguanine and O(6)-chloroethylguanine DNA adducts. In a Phase I clinical trial, BG was given in increasing doses (from 10 to 120 mg/m(2)) by 1-h infusion. We previously reported depletion of AGT activity, and in this report, we demonstrate the relationship between degradation of BG-inactivated AGT protein and the depletion of AGT activity in peripheral blood mononuclear cells (PBMCs) and tumor samples obtained by computed tomography-guided cutting needle biopsy from patients prior to BG and either 2 or 18 h after BG. In PBMCs, BG inactivated AGT activity by over 95-100% at the end of a 1-h infusion, and depletion was maintained for 18 h. In contrast, AGT protein remained almost unchanged for up to 18 h after BG, suggesting that inactivated AGT proteins remain immunoreactive and are not rapidly degraded in PBMCs. In patient tumor biopsies, AGT activity was depleted approximately 90% 2 h after BG. Tumor AGT protein levels were reduced to approximately 40% of pretreatment values when detected by either Western blot or immunohistochemistry staining. In tumor samples obtained 18 h after BG, >95% inactivation of tumor AGT activity was observed at BG doses of 36-80 mg/m(2), and complete depletion of tumor AGT activity occurred at 120 mg/m(2) BG. However, residual AGT protein (5-10% of baseline) was detectable in all tumor samples. Therefore, the degradation of BG-inactivated AGT protein appeared to be much more rapid in tumors than that in PBMCs, which may impact on AGT regeneration rates as well. Because degradation of BG-inactivated AGT takes place slowly, antibody-based measurements of AGT protein correlate poorly with depletion of AGT activity immediately after BG. Thus, biochemical activity measurements remain the appropriate monitor of AGT during therapeutic modulation. These data provide the first and conclusive evidence of differential degradation rates of inactivated AGT in PBMCs and tumors of patients after treatment with BG and suggest that immunoreactive AGT measurements in PBMCs are a poor surrogate for AGT activity in tumor tissue.

Biopsy↗
PubMed2000

Preclinical toxicity and efficacy study of a 14-day schedule of oral 5-iodo-2-pyrimidinone-2'-deoxyribose as a prodrug for 5-iodo-2'-deoxyuridine radiosensitization in U251 human glioblastoma xenografts.

In anticipation of an initial clinical Phase I trial in patients with high-grade gliomas of p.o. administered 5-iodo2-pyrimidinone-2'-deoxyribose (IPdR) given daily for 14 days as a prodrug for 5-iodo-2'-deoxyuridine (IUdR)-mediated tumor radiosensitization, we determined the systemic toxicities and the percentage IUdR-DNA incorporation in normal athymic mouse tissues and a human glioblastoma xenograft (U251) after this dosing schedule of IPdR. Using a tumor regrowth assay of s.c. U251 xenografts, we also compared radiosensitization with this IPdR-dosing schedule to radiation therapy (XRT) alone (2 Gy/day for 4 days) or to XRT after continuous infusion IUdR for 14 days at the maximum tolerated dose in mice (100 mg/kg/day). Athymic mice with and without U251 s.c. xenografts tolerated 750 or 1500 mg/kg/day of p.o. IPdR (using gastric lavage) for 14 days without weight loss or activity level changes during treatment and for a 28-day posttreatment observation period. The percentage IUdR-DNA incorporation in U251 tumor cells was significantly higher after p.o. IPdR (750 and 1500 mg/kg/day) for 14 days (3.1 +/- 0.2% and 3.7 +/- 0.3%, respectively) than continuous infusion IUdR for 14 days (1.4 +/- 0.1%). Compared to XRT alone, a significant sensitizer enhancement ratio (SER) was found with the combination of p.o. IPdR (1500 mg/kg/d) + XRT (SER = 1.31; P = 0.05) but not for the combination of continuous infusion IUdR + XRT (SER = 1.07; P = 0.57) in the U251 xenografts. The percentage IUdR-DNA incorporation after IPdR at 1500 mg/kg/day for 14 days in normal bone marrow, normal small intestine, and normal liver were 1.2 +/-0.2%, 3.3 +/- 0.3%, and 0.2 +/- 0.1%, respectively. We conclude that a 14-day p.o. schedule of IPdR at up to 1500 mg/kg/day results in no significant systemic toxicity in athymic mice and is associated with significant radiosensitization using this human glioblastoma multiforme xenograft model. Based on these data and our previously published data using shorter IPdR dosing schedules, which also demonstrate an improved therapeutic index for IPdR compared to IUdR, an initial clinical Phase I and pharmacokinetic study of p.o. IPdR daily for 14 days is being designed.

Administration, Oral↗
PubMed1999

Leukocyte O6-alkylguanine-DNA alkyltransferase from human donors is uniformly sensitive to O6-benzylguanine.

O6-Alkylguanine-DNA alkyltransferase (AGT) is the key DNA repair protein responsible for resistance to chloroethylating and methylating agents that attack at the O6 position of guanine. O6-Benzylguanine (BG), a potent inhibitor of AGT, has recently entered clinical trials. A number of point mutations and at least one human polymorphism within AGT are associated with AGT resistance to inactivation by BG. In this study, we evaluated AGT inhibition by BG in an in vitro assay of peripheral blood mononuclear cell AGT from 56 normal donors, 42 Caucasians, and 14 Japanese. AGT activity ranged from 2.7 to 21.9 fmol/microg DNA and was similar in Japanese and Caucasian donors. Depletion of AGT by BG was uniform in all donors with mean ED50s of 037 microM BG in Caucasians and 0.36 microM BG in Japanese. To determine whether the gly160arg AGT polymorphism described in the Japanese population, and recently shown to be BG resistant, could be detected by this assay, we mixed purified gly160arg AGT protein with blood mononuclear cell extract and measured in vitro BG inactivation. The ED50 for the mixture of the gly160arg AGT and mononuclear cell extract was 9 microM BG. On the basis of results in 56 donors, we conclude that BG-resistant AGT, defined as an ED50 in mononuclear cells of >1 microM BG, is present in 0 of 56 donors, (95% confidence interval, 0-6%), suggesting that polymorphisms producing AGT-resistant BG are unusual in humans.

Alkyl and Aryl Transferases↗
PubMed1998

Heterogeneity of O6-alkylguanine-DNA-alkyltransferase measured by flow cytometric analysis in blood and bone marrow mononuclear cells.

Alkyltransferase (AGT) repairs alkylation at O6-guanine in DNA and is a major determinant of susceptibility to alkylating chemotherapeutic agents and carcinogens. Using a newly developed flow cytometry assay with the monoclonal anti-AGT antibody, mT3.1, we compared AGT expression in single-cell suspensions with standard biochemical and Western blot assays to validate the fluorescence-activated cell sorting (FACS) method and develop potential applications. From Chinese hamster ovary cells (CHO) transfected with human O6-methylguanine-DNA methyl-transferase cDNA, 6 CHO-O6-methylguanine-DNA methyl-transferase clones were isolated that expressed 0.3 to 64 fmol/microgram DNA (by biochemical assay) of human AGT. FACS yielded a linear relationship between mean fluorescence intensity and both AGT activity by biochemical assay and AGT protein by Western blot. Using this standard curve, FACS-analyzed AGT protein content in human peripheral blood mononuclear cells (PBMCs) from normal donors ranged from 6.1 to 12.8 fmol/microgram DNA, similar to those obtained by biochemical assay and Western blot. This suggests that the level of immunoreactive protein appears to be an accurate predictor of AGT activity in the steady state. FACS-AGT in PBMCs from normal donors had a low index of heterogeneity within the sample. In contrast, by FACS-AGT analysis of human bone marrow samples and granulocyte-colony-stimulating factor-mobilized PBMCs, AGT was lower and had an 8-fold higher index of heterogeneity than observed in PBMCs from normal donors. After treatment with O6-benzylguanine (O6-bG), Western and FACS-AGT detected significant levels of AGT protein for up to 24 h, whereas biochemical assay showed AGT activity less than 5% of the basal level. Because only the biochemical assay accurately measures net AGT activity, the AGT-FACS assay will not be useful in clinical trials to assess the efficacy of O6-bG or other AGT inhibitors. Thus, AGT-FACS can rapidly assess the heterogeneity of steady-state AGT in single-cell suspensions and may be useful for assay in lymphocytes, bone marrow cells, leukemic myeloma plasma cells, or cells transfected with the AGT gene; Western blot analysis is better for small samples such as tumor biopsies, whereas biochemical assay is best able to measure enzyme activity and its inactivation by O6-bG or other agents.

Animals↗
PubMed1997

Molecular evolution and diversity in Bacillus anthracis as detected by amplified fragment length polymorphism markers.

Bacillus anthracis causes anthrax and represents one of the most molecularly monomorphic bacteria known. We have used AFLP (amplified fragment length polymorphism) DNA markers to analyze 78 B. anthracis isolates and six related Bacillus species for molecular variation. AFLP markers are extremely sensitive to even small sequence variation, using PCR and high-resolution electrophoresis to examine restriction fragments. Using this approach, we examined ca. 6.3% of the Bacillus genome for length mutations and ca. 0.36% for point mutations. Extensive variation was observed among taxa, and both cladistic and phenetic analyses were used to construct a phylogeny of B. anthracis and its closest relatives. This genome-wide analysis of 357 AFLP characters (polymorphic fragments) indicates that B. cereus and B. thuringiensis are the closest taxa to B. anthracis, with B. mycoides slightly more distant. B. subtilis, B. polymyxa, and B. stearothermophilus shared few AFLP markers with B. anthracis and were used as outgroups to root the analysis. In contrast to the variation among taxa, only rare AFLP marker variation was observed within B. anthracis, which may be the most genetically uniform bacterial species known. However, AFLP markers did establish the presence or absence of the pXO1 and pXO2 plasmids and detected 31 polymorphic chromosomal regions among the 79 B. anthracis isolates. Cluster analysis identified two very distinct genetic lineages among the B. anthracis isolates. The level of variation and its geographic distribution are consistent with a historically recent African origin for this pathogenic organism. Based on AFLP marker similarity, the ongoing anthrax epidemic in Canada and the northern United States is due to a single strain introduction that has remained stable over at least 30 years and a 1,000-mile distribution.

Animals↗
PubMed1997

A randomized, double-blind, crossover comparative endoscopy study on the gastroduodenal tolerability of a highly specific cyclooxygenase-2 inhibitor, flosulide, and naproxen.

BACKGROUND: Inhibition of constitutively expressed cyclooxygenase (Cox-1) is thought to play an important role in the gastrointestinal toxicity of nonsteroidal anti-inflammatory drugs (NSAID), while their therapeutic action may be due to inhibition of the enzyme Cox-2, which is specifically expressed at sites of inflammation. NSAIDs with high affinity and specifity for Cox-2 hold the promise of maintaining efficacy without the gastrointestinal side effects of conventional NSAIDs. METHODS: We assessed the gastrointestinal tolerability of flosulide (20 mg twice a day), a highly selective Cox-2 inhibitor with that of naproxen (500 mg twice a day), which has equal affinity for Cox-1 and -2 in 19 patients with osteoarthrosis in a randomized, double blind, crossover endoscopy study. Subjects were treated for 2 weeks with a 2-week washout period. Gastroduodenal damage was primarily assessed as by Lanza (grades 0-4). RESULTS: No stomach damage was seen in 13 (68%) patients after flosulide and in 5 (37%) after naproxen (P < 0.001). Lanza scores were significantly lower after flosulide (0.58) than after naproxen (1.47) (P < 0.001; odds ratio, 84.4; 95% confidence interval, 1.45-4908). Flosulide was significantly better tolerated (P < 0.005) than naproxen. CONCLUSION: These results endorse the idea that highly selective Cox-2 inhibitors may be associated with lesser gastrointestinal side effects than conventional NSAIDs.

Adult↗
PubMed1979

Effect of furosemide (lasix) on acute severe experimental cerebral edema.

The effect of furosemide (Lasix) therapy on a standardized experimental cerebral edema, induced in rats by applying a cooling stamp to the right side of the skull over the right coronal suture by means of a stereotactic instrument, was examined. The hemispherically separated water and electrolyte contents of the brain were analyzed after 24 h. Following furosemide therapy, the behavior of these edema parameters was compared statistically with dexamethasone, glycerol and albumin. An increase of the water and sodium content, and a decrease of potassium was observed 24 h after the trauma, especially in the right hemisphere. Furosemide did not improve either the water content or the electrolyte balance. By contrast, the administration of dexamethasone, glycerol and albumin was followed by a significant improvement of the edema. In experiments with cats, the course of the edema and the effect of furosemide on the cold brain injury of the right hemisphere were observed by measuring the intracranial pressure (ICP) values, and by continuous monitoring of the EEG. The ventricular CSF pressure and epidural pressures were also recorded. The electrical brain activity was continuously compared with the course of the ICP by means of computer analysis. In addition, the blood osmolality and diuresis were monitored. The ICP increased rapidly after the trauma, establishing considerable pressure gradients, and the EEG power intensities decreased markedly on the right side. Histologically, there was an extended edema of the white matter of both hemispheres. The ICP was not lowered by single injections or high dose infusions of furosemide, and the EEG power intensities also did not improve. Infusions of large volumes of furosemide even resulted in an increase of ICP, but infusion of 40% sorbitol effected a rapid decrease of ICP and EEG recovery over the left hemisphere. Sorbitol infusion also caused a marked rise in the blood osmolality, whereas furosemide had no such effect. The results raise considerable doubts as to the propriety of the exclusive use of furosemide for cases of acute cerebral edema with raised ICP. The diuretic effect is insufficient to establish an osmotic gradient, and its general dehydrating effect does not acutely influence the ICP. The absence of effect on the experimental tissue edema would not appear to commend furosemide as basic therapy for cases of traumatic cerebral edema.

Albumins↗
PubMed1977

A new miniaturized system for monitoring the epidural pressure in children and adults.

A new miniaturized epidural pressure transducing system for monitoring intracranial pressure (ICP) has been developed. The system is of the as yet smallest known dimensions. The transducer is implanted automatically coplanar to the dura via a burr hole of 4 mm diameter in the conscious patient without special surgical equipment. Application is possible in adults, children and infants. We have achieved a maximal resolution of 10(-3) mm of Hg. At a full scale range of 100 mm of Hg the zero-point drift is less than 1 mm of Hg/24 h.

Adult↗