Biomedical subjects

X Luo

Publications and source records attributed to X Luo.

At least 163 records · Page 9Linked to original sources

PubMed1998

Probenecid alters topotecan systemic and renal disposition by inhibiting renal tubular secretion.

Topotecan is primarily eliminated by the kidneys, with 60 to 70% of the dose recovered as topotecan total in the urine. To elucidate the mechanisms of topotecan renal clearance, we evaluated the effect of probenecid on topotecan renal and systemic disposition in mice. Topotecan lactone or hydroxy acid (1.25 mg/kg i.v.) was administered alone or in combination with probenecid (600 or 1,200 mg/kg) given by oral gavage 30 min before and 3 hr after topotecan. Serial blood samples (three mice per time point) and urine samples (five mice per treatment arm) were collected during a 6-hr period. Compared with topotecan alone, coadministration of topotecan lactone or hydroxy acid with probenecid (600 mg/kg) decreased topotecan lactone, total, and hydroxy acid systemic clearance, and total renal clearance. The predominant effect of probenecid was to increase hydroxy acid area under the plasma concentration time curve after administration of topotecan lactone (238.8 vs. 109.9 ng.hr/ml alone, P < .05), or hydroxy acid (1297.2 vs. 355.0 ng.hr/ml alone, P < .05). By inhibiting renal tubular secretion, probenecid decreased renal and systemic clearance which led to an increase in topotecan systemic exposure. These data suggest that probenecid primarily inhibited secretion of the anionic hydroxy acid form, and by direct or indirect mechanisms increased topotecan lactone systemic exposure. Topotecan elimination through renal tubular secretion may have clinical relevance for the use of topotecan in patients with altered renal function.

Animals↗

PubMed1998

Studies of the efficacy and pharmacology of irinotecan against human colon tumor xenograft models.

Irinotecan, administered i.v. on days 1-5 and 8-12 [(dx5)2 i.v.] has demonstrated significant activity against advanced human tumor xenografts. To explore the feasibility of prolonged oral administration of irinotecan, we compared the efficacy of oral and i.v. irinotecan on the (dx5)2 schedule. We also evaluated oral therapy for 12 consecutive weeks [(dx5)12] at 25 and 50 mg/kg and two consecutive 5-day courses repeated every 21 days for up to four cycles ([(dx5)2]4) at 50 and 75 mg/kg/dose in a series of human colon carcinoma xenograft lines. In addition, we evaluated the effect of a sensitive (HC1) and resistant (ELC2) human colon adenocarcinoma xenograft on irinotecan and SN-38 lactone disposition after administration of irinotecan 10 mg/kg i.v. and 10 and 25 mg/kg p.o. Irinotecan i.v. at 40 mg/kg and oral at 50 and 75 mg/kg on the (dx5)2 schedule had similar activity against the panel of adult colon adenocarcinoma xenografts. Irinotecan given p.o. also demonstrated significant activity against a topotecan-resistant derivative, VRC5/TOPO. Oral administration of 75 mg/kg [(dx5)2]4 and 50 mg/kg (dx5)12 achieved complete response in five of seven xenograft lines evaluated. After i.v. administration, mice bearing HC1 xenografts had 43% greater SN-38 lactone systemic exposure compared to those with ELC2 xenografts and non-tumor-bearing mice. After oral (10 mg/kg) administration, there was a 5-fold higher molar formation of SN-38 lactone compared to i.v. (10 mg/kg) administration in tumor and non-tumor-bearing mice. SN-38 systemic exposure associated with the lowest oral dose (25 mg/kg) achieving complete response for HC1 was 942.6 ng/ml x h. These results emphasize the importance of pharmacokinetic studies as part of tumor response studies in xenograft models.

Adenocarcinoma↗

PubMed1998

Effects of dobutamine, norepinephrine and epinephrine on intramucosal pH and hemodynamics of dogs during endotoxic shock.

This study assessed the effects of dobutamine (DOB), epinephrine (EPI) and norepinephrine (NE) on gastric tissue oxygenation indicated by gastric intramucosal pH (pHi) and hemodynamics in dogs subjected to endotoxic shock. Twenty-four dogs were assigned to four groups of 6 dogs each: endotoxin without catecholamine and endotoxin with DOB, or EPI or NE. Endotoxic shock was induced by intravenous injection of 3 mg/kg of E. coli over 1 min, with an additional 3 mg/kg over the next 2 hrs. Dogs were resuscitated with normal saline to maintain pulmonary capillary wedge pressure (PCWP) near baseline levels. Catecholamines were infused at 0.1, 0.4 and 1.6 micrograms/kg/min (EPI and NE) and 2.5, 5.0 and 10.0 micrograms/kg/min (DOB) for 30 min at each rate. After 2 hrs of endotoxemia, mean arterial pressure (MAP) and cardiac index (CI) and oxygenation delivery index (DO2I) for all dogs decreased by 46.5%, 43.9% and 15.1% respectively, while pHi decreased from 7.47 to 7.10. Endotoxemia increased blood lactate by 142%. Following fluid resuscitation, EPI (1.6 micrograms/kg/min) further increased lactate by 178% (1.22 to 3.4 mmol/L). No correlation was found between tonometry pHi and lactate (R2 = 0.003), pHi and pHa (R2 = 0.231), pHi and DO2I (R2 = 0.056) nor between intramucosal PCO2 and PaCO2 (R2 = 0.005). pHi did not reflect the improvements in cardiovascular hemodynamics observed following administration of catecholamines. NE improved MAP, CI and DO2I whereas DOB produced similar effects as NE but further reduced SVR. EPI produced similar effects as NE. DOB, NE and EPI further decreased pHi. EPI significantly (P < 0.05) increased blood lactate levels more than DOB and NE.

Animals↗

PubMed1997

Comparison of primary osteosarcoma of flat bones with secondary osteosarcoma of any site.

BACKGROUND: The authors hypothesized that the outcomes for young patients who present with primary osteosarcoma of flat bones or secondary osteosarcoma after other primary malignancies are similar because the sites of these tumors rarely makes them amenable to complete surgical resection. METHODS: The authors reviewed their experience with 27 patients with primary osteosarcomas involving flat bones and 18 patients with secondary osteosarcomas of any site, evaluating treatment, metastatic patterns, and outcome. RESULTS: Eleven of the 27 primary osteosarcomas and 10 of the 18 secondary osteosarcomas were at least partially resectable at the time of initial diagnosis. At last follow-up, 10 of the 27 patients with primary flat bone osteosarcoma were alive, eight of whom were disease free. Three of 18 with the secondary osteosarcoma patients were alive, including one with locally recurrent disease after recent disease resections. Chemotherapy with single or combinations of agents rarely yielded responses for primary flat bone or secondary osteosarcomas. CONCLUSIONS: Outcome for both groups of patients was poor due to metastases and failure of local control. Sixteen of the 27 patients with primary osteosarcoma of flat bones died of their tumor; an additional patient died of doxorubicin-related cardiomyopathy and had microscopic disease in the primary site at autopsy. Thirteen of the 18 patients with secondary osteosarcoma died of their second metastatic cancer, 2 additional patients died of doxorubicin-related cardiomyopathy/coccidioidomycosis, and another of acute renal toxicity.

Adolescent↗

PubMed1997

Second malignant neoplasms occuring in survivors of osteosarcoma.

BACKGROUND: Second malignant neoplasms have been noted infrequently in survivors of osteosarcoma treated before 1970. METHODS: For the above reason, the authors surveyed their patients to determine the actuarial incidence and relative risk of second malignancies among patients treated with adjuvant chemotherapy for osteosarcoma. RESULTS: Between March 1962 and March 1996, 334 patients received chemotherapy for newly diagnosed primary or metastatic osteosarcoma. Of these patients, 47 presented with metastases, 14 had multifocal osteosarcoma, and 273 had localized disease. Nine patients developed second malignant neoplasms 0.45-17.8 years (median, 6.3 years) after receiving definitive surgery and adjuvant chemotherapy for primary osteosarcoma; 2 of these patients had pulmonary metastasectomies before receiving adjuvant chemotherapy. The second neoplasms comprised two cases of malignant fibrous histiocytoma and one case each of melanoma, glioblastoma multiforme, chondrosarcoma, and carcinoma of the breast: stomach, colon, rectum. The overall 10-year cumulative incidence of second malignancies was 2% +/- 1%; by comparison, this rate was 2% +/- 1% for patients with localized osteosarcoma but was 8% +/- 5% (P = 0.15) for those who presented with metastatic disease. CONCLUSIONS: Since the advent of successful adjuvant chemotherapy, more patients are surviving primary osteosarcoma; therefore, the number of osteosarcoma patients who develop second malignancies can be expected to increase. Recognition of osteosarcoma patients who are members of families with Li-Fraumeni syndrome may lead to earlier intervention for these individuals.

Adolescent↗

PubMed1997

Cyclin-dependent kinase 6 is the principal target of p27/Kip1 regulation of the G1-phase traverse in 1,25-dihydroxyvitamin D3-treated HL60 cells.

Control of cell proliferation remains of intense interest in cancer research. In the 1,25-dihydroxyvitamin D3 HL60 cell system, G1 arrest has been shown to be mediated by elevated levels of p27/Kip1 protein. We show here that the main target of the elevated p27/Kip1 in this system is cyclin-dependent kinase (Cdk) 6. The activity of Cdk2 is also down-regulated, and this is associated with altered and reduced levels of cyclin E in the kinase complex. Paradoxically, the kinase activity of Cdk4 is elevated, in spite of an almost complete G1 block. These data show that the functions of Cdk4 and Cdk6 are not redundant and that Cdk6 and Cdk2 activities are regulated by 1,25-dihydroxyvitamin D3.

Calcitriol↗

PubMed1997

Excessive formation of hydroxyl radicals and aldehydic lipid peroxidation products in cultured skin fibroblasts from patients with complex I deficiency.

Previous studies suggest oxygen free radicals' involvement in the etiology of cardiomyopathy with cataracts. To investigate the role of free radicals in the pathogenesis of the cardiomyopathy with cataracts and complex I deficiency, fibroblasts from patients were assessed for hydroxyl radical formation and aldehydic lipid peroxidation products with and without redox active agents that increase free radicals. The rate of hydroxyl radical formation in patient cells was increased over 2-10-fold under basal conditions, and up to 20-fold after menadione or doxorubicin treatment compared with normal cells. We also found an overproduction of aldehydes in patient cells both under basal conditions and after treatment. Both hydroxyl radicals and toxic aldehydes such as hexanal, 4-hydroxynon-2-enal, and malondialdehyde were elevated in cells from patients with three types of complex I deficiency. In contrast, acyloins, the less toxic conjugated products of pyruvate and saturated aldehydes, were lower in the patient cells. Our data provide direct evidence for the first time that complex I deficiency is associated with excessive production of hydroxyl radicals and lipid peroxidation. The resultant damage may contribute to the early onset of cardiomyopathy and cataracts and death in early infancy in affected patients with this disease.

Aldehydes↗

PubMed1997

Selective up-regulation of protein kinase C eta in phorbol ester-sensitive versus -resistant EL4 mouse thymoma cells.

Stimulation of sensitive EL4 mouse thymoma cells (s-EL4) with phorbol esters results in production of interleukin 2 (IL-2), adherence to a plastic substrate, and growth inhibition, whereas a phorbol ester-resistant variant (r-EL4) fails to respond. Previous studies revealed substantially decreased expression of protein kinase C (PKC) epsilon in the r-EL4 versus s-EL4 cells. This work has been extended to examine the more recently described PKC isozymes. Western and Northern analyses revealed a marked decrease in PKC eta and theta in r-EL4 as compared to s-EL4 cells. Treatment of these lines with phorbol ester for 24 h resulted in down-regulation of all PKC isozymes examined except PKC eta, which was up-regulated in the s-EL4 cells at the time of maximal IL-2 production. Two newly isolated EL4 clones, resistant to phorbol ester-induced growth inhibition but still exhibiting the phorbol ester-induced adherence and IL-2 production, both expressed PKC eta and theta. Collectively, these observations suggest a dissociation of growth inhibition from adherence and IL-2 production pathways and a potential role for PKC eta in the latter.

Animals↗

PubMed1997

Deficient tyrosine phosphorylation of c-Cbl and associated proteins in phorbol ester-resistant EL4 mouse thymoma cells.

Two tyrosine phosphoproteins in phorbol ester-sensitive EL4 (S-EL4) mouse thymoma cells have been identified as the p120 c-Cbl protooncogene product and the p85 subunit of phosphatidylinositol 3-kinase. Tyrosine phosphorylation of p120 and p85 increased rapidly after phorbol ester stimulation. Phorbol ester-resistant EL4 (R-EL4) cells expressed comparable amounts of c-Cbl and phosphatidylinositol 3-kinase protein but greatly diminished tyrosine phosphorylation. Co-immunoprecipitation experiments revealed complexes of c-Cbl with p85, and of p85 with the tyrosine kinase Lck in phorbol ester-stimulated S-EL4 but not in unstimulated S-EL4 or in R-EL4 cells. In vitro binding of c-Cbl with Lck SH2 or SH3 domains was detected in both S-EL4 and R-EL4 cells, suggesting that c-Cbl, p85, and Lck may form a ternary complex. In vitro kinase assays revealed phosphorylation of p85 by Lck only in phorbol ester-stimulated S-EL4 cells. Collectively, these results suggest that Cbl-p85 and Lck-p85 complexes may form in unstimulated S-EL4 and R-EL4 cells but were not detected due to absence of tyrosine phosphorylation of p85. Greatly decreased tyrosine phosphorylation of c-Cbl and p85 in the complexes may contribute to the failure of R-EL4 cells to respond to phorbol ester.

Animals↗

PubMed1997

Mapping of the novel protein kinase catalytic domain of Dictyostelium myosin II heavy chain kinase A.

Myosin heavy chain kinase A (MHCK A) in Dictyostelium was identified as a biochemical activity that phosphorylates threonine residues in the myosin II tail domain and regulates myosin filament assembly. The catalytic domain of MHCK A has now been mapped through the functional characterization of a series of MHCK A truncation mutants expressed in Escherichia coli. A recombinant protein comprising the central nonrepetitive domain of MHCK A (residues 552-841) was isolated in a soluble form and shown to phosphorylate Dictyostelium myosin II, myelin basic protein, and a synthetic peptide substrate. The functionally mapped catalytic domain of MHCK A shows no detectable sequence similarity to known classes of eukaryotic protein kinases but shares substantial sequence similarity with a transcribed Caenorhabditis elegans gene and with the mammalian elongation factor-2 kinase (calcium/calmodulin-dependent protein kinase III). We suggest that MHCK A represents the prototype for a novel, widely occurring protein kinase family.

Amino Acid Sequence↗

PubMed1997

Doxorubicin-induced acute changes in cytotoxic aldehydes, antioxidant status and cardiac function in the rat.

Doxorubicin (DOX)-induced cardiotoxicity is thought to be caused by free radical-mediated mechanisms. An in vivo rat model was developed to investigate the DOX-induced cascade of early biochemical changes focusing on the central role of the aldehydic lipid peroxidation products. Antioxidant status was evaluated by glutathione measurements. Creatine Kinase (CK) activity was measured as an index of cardiac injury. Development of functional abnormalities were documented by echocardiography. The results showed that aldehydes in rat plasma and heart tissues increased significantly following DOX treatment. The changes occurred early, peaked around 2 h after DOX administration, and the levels declined or returned to baseline value within 8-24 h. Toxic aldehyde levels including malondialdehyde, hexanal and 4-hydroxy-non-2-enal also increased. Acyloin levels, metabolic products of aldehydes, increased early and then decreased in plasma, and there was a significant decrease in heart tissues after DOX treatment. GSH levels decreased early, then increased by 24 h, while GSSG levels decreased initially, then increased after DOX treatment, suggesting early depletion of GSH and a later rebound phenomenon. CK levels were elevated after treatment. The functional abnormalities were documented by stress echocardiography in some rats although the changes were not consistent at such an early stage following treatment. Our data confirmed the involvement of free radicals, and suggested that the cytotoxic aldehydes play a central role in initiating the steps that lead to functional impairment of the myocardium following DOX administration. Scavengers and the metabolic removal of some of the aldehydes also play a role in protecting the myocardium against injury.

Aldehydes↗

PubMed1997

Phase I trial of subcutaneous interleukin-1 alpha in children with malignant solid tumors.

Interleukin-1 alpha (IL-1 alpha) is myeloprotective in a variety of animal models of cancer chemotherapy and is similarly beneficial in adults treated with carboplatin, 5-fluorouracil, and after autologous bone marrow transplantation. There are no trials of this agent in children. Our purpose was to determine the toxicity and maximum tolerated dose (MTD) of recombinant human interleukin-1 alpha (rhuIL-1 alpha) in children with solid tumors receiving intensive cancer chemotherapy and to evaluate its myelo-protective effects. Cohorts of patients received rhuIL-1 alpha in doses of 0.1-10 micrograms/m2 for 4 days by subcutaneous injection prior to ICF chemotherapy (ifosfamide, 2 g/m2/day x 3, carboplatin targeted to an area under the curve of 8 mg/ml x min on day 1, and etoposide, 100 mg/m2 daily for 3 days). Patients were randomized to receive rhuIL-1 alpha before either the first or second course of therapy. After the MTD of rhuIL-1 alpha was determined an additional group of patients received rhuIL-1 alpha at the dose immediately following ICE chemotherapy. The dose-limiting toxicities of rhuIL-1 alpha in the 27 children tested comprised systemic symptoms of fever, chills, headache, and hypotension. The MTD was 3 micrograms/m2/day. There were no differences in chemotherapy-induced hematologic toxicity with increasing doses of rhuIL-1 alpha or in comparisons before or after ICE chemotherapy. Although rhuIL-1 alpha can be given safely to children receiving myelosuppressive chemotherapy, clinical usefulness would mandate a significant hematopoietic benefit in view of the trouble some side effects identified. We saw no evidence of a hematoprotective effect.

Adolescent↗

PubMed1997

Multimodal therapy for children and adolescents with Ewing sarcoma: results of the First National Chilean Trial (1986-1991).

Thirty-seven patients with Ewing sarcoma were treated in the First National Chilean Trial for Ewing's Sarcoma (1986-1991), which comprised the St. Jude Ewing's 78 Study. All patients received cyclophosphamide, doxorubicin, vincristine, and Dactinomycin for a total treatment period of about 10 months, and all prescribed therapy was administered. Local therapy consisted of irradiation (RT) to the primary tumor, complete surgical resection, or a combination of both surgery and RT. Twenty-nine of these patients had localized tumors, 24% had pelvic primary tumors, 21 were males, and 20 were greater than 10 years of age at diagnosis. Twenty-one patients had tumors that were greater than 8 cm in largest diameter. Fourteen of the 29 patients with localized disease remain disease free at 23 to 91 months from diagnosis. Fourteen patients have died of-tumor-related complications and 1 of a secondary malignancy. Relapse was local only in 4, metastatic in 9, and local plus metastatic in 1. Only 1 of the 8 patients with metastatic disease at presentation remains disease free. Toxicity consisted primarily of myelosuppression and mucositis. We conclude that this form of relative intense multimodal therapy for children/adolescents with localized Ewing sarcoma is curative in about half of affected children as in the original St. Jude study, and that it can be safely given in a developing country, provided that careful attention to supportive care and treatment planning is given. Although these results represent improvement in outcome for our patients, more effective therapy is needed for children with Ewing sarcoma, especially those with metastatic disease at presentation.

Adolescent↗

PubMed1997

Neurotoxic effects of kainic acid on substantia nigra neurons in rat brain slices.

Excitatory amino acids (EAAs) have been implicated as mediators of cell death in neurodegenerative diseases involving catecholamine neurons. Few studies, however, have examined the toxic effects of EAAs on identified catecholamine neurons in vitro. We have investigated the neurotoxic effects of kainic acid in a rat brain substantia nigra (SN) slice preparation. Rats (60-80 g) were anesthetised with halothane and killed by cervical dislocation. SN slices, 300 microm thick, were incubated at 35 degrees C in a modified Krebs solution in the presence or absence of kainic acid and then fixed and processed for either immunohistochemistry (IHC) or electron microscopy (EM). In IHC experiments, SN neurons were labeled using antibody to tyrosine hydroxylase (TH) coupled to diaminobenzidine. In control slices, the antibody labeled not only the cell body but also the prolific dendritic arbor of SN neurons. Treatment with 50 microM kainic acid for 15 min or 2 h resulted in loss of TH staining and apparent fragmentation of the dendrites. EM provided ultrastructural evidence for kainic acid-induced degeneration of the dendritic arbor of SN neurons. Typically, the dendritic membrane was broken, or diffuse and collapsed. Ultrastructural damage, including clumping and marginalization of chromatin and vacuolation of the cytoplasm, was also observed in cell bodies. Damage to the dendritic arbor may occur early in the neurotoxic events leading to cell death, preceding the loss of the cell body. Our observations are consistent with the postulated role of EAAs as mediators of catecholamine neuron death.

Animals↗

PubMed1997

Determination of hydroxyl radicals using salicylate as a trapping agent by gas chromatography-mass spectrometry.

OBJECTIVES: To establish a sensitive method for measuring hydroxyl radical formation in biological systems using salicylate as probe. METHODS: Salicylate hydroxylation products and related aromatic compounds were extracted and converted to trimethylsilyl (TMS) derivatives. The derivatives were analyzed by gas chromatography-mass spectrometry (GC-MS). Quantitation was achieved by selected-ion-recording (SIR) with benzoic acid (ring-D5) as an internal standard. RESULTS: All compounds were well separated and specifically quantitated by a GC-MS procedure. Standard curves were linear in the concentration ranges investigated (0.1-10 nmol) for all individual compounds. Recovery from human plasma was in the range of 90-102%. The detection limit was between 50 fmol-1 pmol per 1 microL injection. The within-run and between-run coefficients of variation were between 4.6-9.1%. We were able to detect the baseline levels of hydroxylation products in human fibroblasts after incubation with salicylate. CONCLUSIONS: The GC-MS assay presented here can specifically identify and quantitate salicylate hydroxylation products and related aromatic compounds, which can be used as an in vivo marker of oxidative stress. This sensitive method has broad applications, both in the area of free radical medicine and in the pharmacological study of aspirin and its metabolites.

Free Radical Scavengers↗

PubMed1997

Complications of pelvic exenteration in children who have genitourinary rhabdomyosarcoma.

BACKGROUND: Rhabdomyosarcoma is the most frequently encountered soft tissue sarcoma in children younger than 15 years of age. METHODS: The authors reviewed the early and long-term morbidity rate and clinical outcome of pelvic exenteration for genitourinary rhabdomyosarcoma (GU-RMS) in children. Of 43 patients with this diagnosis who were seen at St Jude Children's Research Hospital between 1963 and 1994, 17 underwent pelvic exenteration. These 13 boys and four girls ranged in age from 6 months to 15 years (median, 3.5 years). Their primary sites included prostate (n = 12), bladder (n = 4), and uterus (n = 1). All patients received multiagent chemotherapy and either preoperative or postoperative radiation therapy. Anterior exenteration was performed in 15 patients and total exenteration in two. The complications were classified as early or late (occurring within or after 30 days from the date of surgery) and as major or minor (depending on the risk of death or physical or functional disability). RESULTS: Thirteen of the 17 patients (76%) had 49 surgery-related complications. Wound infection (24%), fistula, abscess, and malnourishment (12% each) were the most common early major complications, with hydronephrosis (35%), bowel obstruction (24%), acute pyelonephritis, fistula, lymphedema, and ureter stenosis (12% each) making up the majority of late complications in this category. Relatively frequent minor complications included protracted paralytic ileus and hematuria (18%), cholelithiasis, chronic diarrhea and, peristoma skin irritation (12%). Disease-free survival was associated with the timing of surgery (P = .002). All but one of the 12 patients who underwent surgery within 6 months of diagnosis are alive, compared with only one of five whose surgery was performed after a longer interval. Pelvic exenteration for GU-RMS was associated with a high rate of serious complications in this series of patients treated over 31 years. CONCLUSION: With recent advances in surgical techniques, as well as improvements in preoperative and postoperative care, this procedure should continue to be applied in cases resistant to conventional therapy.

Adolescent↗

PubMed1997

Cytotoxic aldehydes as possible markers for childhood cancer.

Concentrations of 22 known aldehydes (byproducts of lipid peroxidation), 5 acyloins, free and total carnitine and acylcarnitines were measured in plasma and urine obtained from pediatric patients with various forms of cancer before any treatment, and following treatment with doxorubicin or daunorubicin. Aldehydes, before the initiation of chemotherapy, were significantly elevated in cancer patients compared to controls. Aldehydes such as hexanal, heptanal, and malondialdehyde were strikingly higher in samples from cancer patients, while trans 4-cis-4-decenal was the prominent aldehyde in the blood of controls. In addition, in each form of cancer the pattern of aldehydes appeared to be unique when compared to controls, or to others forms of cancer. In cancer patients receiving chemotherapy there was a general trend toward a reduction 24 h after both the first and after the fifth doxorubicin dose. These changes however were not significant statistically due to large inter-patient variation. Free and total plasma carnitine levels remained in the normal range, and there were no abnormal acylcarnitines detected in urine. Possible hypotheses to explain the elevations in aldehydes, and the reasons for the changed aldehyde profiles in different forms of cancer are discussed.

Adolescent↗

PubMed1997

Efficacy of oral irinotecan against neuroblastoma xenografts.

The efficacy of the topoisomerase I inhibitor, 7-ethyl-10-(4-[1-piperidino]-1-piperidino)-carbonyloxy-camptotheci n (irinotecan, CPT-11), administered by oral gavage has been examined against a panel of six independently derived neuroblastoma xenografts. Irinotecan was administered either daily for 5 days on 12 consecutive weeks ¿(d x 5)12¿ or for 5 days on two consecutive weeks repeated every 21 days for 4 cycles ¿[(d x 5)2]4¿. Given on the (d x 5)12 schedule the maximum tolerated dose (MTD) was 50 mg/kg. For intermittent scheduling ¿[(d x 5)2]4¿, the MTD was 75 mg/kg, resulting in the same total dose being administered (3 g/kg) over the period of treatment. At the MTD for the 12 consecutive week schedule there were two of 42 toxicity related deaths, whereas intermittent scheduling at the MTD resulted in none of 42 deaths. The intermittent schedule ¿[(d x 5)2]4¿ was less toxic than therapy given (d x 5)12, as at the end of treatment mice weighed 92 +/- 4% (SD; n = 6 experiments) and 81 +/- 4% (SD; n = 6 experiments) of their body weight at the start of therapy, respectively. The latter schedule was associated with loose feces starting around week 8 of therapy, broken teeth and a high incidence of swelling of the orbital conjunctiva that developed late in the course of therapy. Given (d x 5)12, irinotecan caused complete regressions of all six neuroblastoma xenograft lines. Because mice tolerate significantly greater systemic exposure to SN-38 lactone than do patients (as determined by plasma AUC at the respective MTD), we evaluated the intermittent schedule of administration, reducing the dose/administration to determine the lowest dose levels that produced objective regressions of these neuroblastoma xenografts and determined the daily systemic exposure associated with these dose levels. In four lines examined objective responses were obtained at dose levels of 12.5 or 6.25 mg/kg. The daily plasma AUC exposures associated with minimum dose achieving response in NB1691 (12.5 mg/kg), NB1643 (6.25 mg/kg) and NBEB (12.5 mg/kg) for irinotecan lactone were 219, 152 and 653 ng-h/ml, respectively; and for SN-38 lactone were 704, 418 and 987 ng-h/ml, respectively. These results indicate that childhood neuroblastoma xenografts are highly sensitive to irinotecan given by oral administration and therapeutic activity is similar to i.v. irinotecan administered on similar schedules.

Administration, Oral↗