Effect of macrophage migration inhibition factor on the content of stromal precursor cells in mouse bone marrow and efficiency of bone marrow precursor cell cloning in vitro.

The content of stromal precursor cells in the bone marrow of mice decreased 2-5.7 times 24 h after injection of macrophage migration inhibition factor in doses of 0.1-50 ng/kg, this reduction depending on the dose of inhibition factor. The content of precursor cells in the bone marrow of mice increased 2-fold 24 h after injection of S. typhimurium bacterial mass. One day after injection of S. typhimurium bacterial mass, the count of precursor cells in mouse spleen was 7-fold higher than 24 h after injection of macrophage migration inhibition factor. The efficiency of cloning of mouse bone marrow stromal precursor cells in vitro was suppressed 1.7-2.8 times in the presence of macrophage migration inhibition factor in doses of 0.1 to 50 ng/ml culture medium. The effect of cloning inhibition was preserved, if macrophage migration inhibition factor was added to the culture medium after 2 days of bone marrow cell culturing. In general, macrophage migration inhibition factor inhibits stromal precursor cells in vivo and in vitro. The data also indicate that macrophage migration inhibition factor is not responsible for rapid and sharp increase in the count of stromal precursor cells after immunization of animals.

Identification of macrophage migration inhibitory factor isoforms in bovine brain.

In the course of the study of the primary structures and molecular mechanisms of action of immunologically active compounds of the nervous system we have isolated from the soluble fraction of total bovine brain two heat-stable proteins. The purification procedure was mainly based on DEAE-Servacel ion-exchange chromatography and reversed-phase HPLC. The proteins were identified by the N-terminal Edman microsequence analysis and database searching as macrophage migration inhibitory factor (MIF). The N-terminal sequences for MIF1 and MIF2 were found to be identical. According to mass spectral analysis, the molecular masses for MIF1 and MIF2 were determined respectively as 12,369.21 and 12,299.7 Da. In addition, we have also isolated a third peptide having the same N-terminal sequence and Mr 9,496.2 that seems to be a proteolytic fragment of MIF. Using p-hydroxyphenylpyruvate as a substrate, we have not revealed tautomerase activity of either MIF1 or MIF2. As both the immunologic and enzymatic activities were reported to be expressed by the oligomeric structure of MIF, we suggest that the present study may give additional information on MIF in terms of structural properties of this protein. A comparatively simple purification procedure is presented that may be widely used for simultaneous isolation in one run of MIF isoforms.

Stereoselective metabolism of ifosfamide by human P-450s 3A4 and 2B6. Favorable metabolic properties of R-enantiomer.

The anticancer prodrug ifosfamide (IFA) contains a chiral phosphorous atom and is administered clinically as a racemic mixture of R and S enantiomers. Animal model studies and clinical data indicate enantioselective differences in cytochrome P-450 (CYP) metabolism, pharmacokinetics, and therapeutic efficacy between the two enantiomers; however, the metabolism of individual IFA enantiomers has not been fully characterized. The role of CYP enzymes in the stereoselective metabolism of R-IFA and S-IFA was investigated by monitoring the formation of both 4-hydroxy (activated) and N-dechloroethyl (DCl) (inactive, neurotoxic) metabolites. In the 4-hydroxylation reaction, cDNA-expressed CYPs 3A4 and 3A5 preferentially metabolized R-IFA, whereas CYP2B6 was more active toward S-IFA. Enantioselective IFA 4-hydroxylation (R > S) was observed with six of eight human liver samples. In the N-dechloroethylation reaction, CYPs 3A4 and 2B6 both catalyzed a significantly higher intrinsic metabolic clearance (V(max)/K(m)) of S-IFA compared with R-IFA. Striking P-450 form specificity in the formation of individual DCl metabolites was evident. CYPs 3A4 and 3A5 preferentially produced (R)N2-DCl-IFA and (R)N3-DCl-IFA (derived from R-IFA and S-IFA, respectively), whereas CYP2B6 correspondingly formed (S)N3-DCl-IFA and (S)N2-DCl-IFA. In human liver microsomes, the CYP3A-specific inhibitor troleandomycin suppressed (R)N2- and (R)N3-DCl-IFA formation by >/=80%, whereas (S)N2- and (S)N3-DCl-IFA formation were selectively inhibited (>/=85%) by a CYP2B6-specific monoclonal antibody. The overall extent of IFA N-dechloroethylation varied with the CYP3A4 and CYP2B6 content of each liver, but was significantly lower for R-IFA (32 +/- 13%) than for S-IFA (62 +/- 17%, n = 8; p <.001) in all livers examined. R-IFA thus has more favorable liver metabolic properties than S-IFA with respect to less extensive N-dechloroethylation and more rapid 4-hydroxylation, indicating that R-IFA may have a distinct clinical advantage over racemic IFA.

Antitumor efficacy and pharmacokinetic analysis of 4-hydroperoxycyclophosphamide in comparison with cyclophosphamide +/- hepatic enzyme effectors.

4-Hydroperoxycyclophosphamide is an oxazaphosphorine which is readily converted without enzymatic involvement to 4-hydroxycyclophosphamide-a key intermediate in the antitumor activity of this class of drugs. The efficacy of 4-hydroperoxycyclophosphamide as a systemically administered antitumor drug was examined in mice bearing EMT-6 mammary carcinoma and in rats bearing 13762 mammary carcinoma in comparison with other oxazaphosphorines. 4-Hydroperoxycyclophosphamide was a more potent tumor cell killing agent than cyclophosphamide or ifosfamide in animals bearing the EMT-6 tumor. There were no significant differences in the toxicity to bone marrow amongst the three oxazaphosphorines. 4-Hydroperoxycyclophosphamide (90 mg/kg) on days 7, 9 and 11 produced 11.5 days of tumor growth delay compared with 10.4 days and 7.1 days for cyclophosphamide (150 mg/kg) and ifosfamide (150 mg/kg) administered on the same schedule, respectively. 4-Hydroperoxycyclophosphamide was tolerated at 90 mg/kg daily for 5 days and at 75 mg/kg twice daily for 4 days producing tumor growth delays of 14.4 days and 16.6 days, respectively. In rats bearing 13762 tumors, 4-hydroperoxycyclophosphamide (90 mg/kg) on days 8, 10 and 12 produced a tumor growth delay of 14.5 days compared with 8.9 days for cyclophosphamide (100 mg/kg) administered on the same schedule. Treatment of 13762 tumor-bearing rats with phenobarbital, pentobarbital or etanidazole increased the tumor growth delay produced by cyclophosphamide while treatment with cimetidine decreased the tumor growth delay produced by cyclophosphamide but not significantly. Administration of 4-hydroperoxycyclophosphamide (90 mg/kg) produced blood concentrations of 4-hydroxycyclophosphamide three-fold higher than those produced by administration of cyclophosphamide (100 mg/kg) at 15 min after drug injection. Treatment with phenobarbital or pentobarbital increased 4-hydroxycyclophosphamide blood concentration while pretreatment with cimetidine decreased 4-hydroxycyclophosphamide blood concentration from cyclophosphamide. 4-Hydroperoxycyclophosphamide is an effective antitumor agent worthy of further investigation.

Dose escalation of N,N',N"-triethylenethiophosphoramide combined with pentoxifylline for advanced breast cancer.

Pentoxifylline potentiates the cytotoxicity of alkylating agents in preclinical models. In this study we sought to define the maximum tolerated dose (MTD) of N,N',N"-triethylenethiophosphoramide (thioTEPA) with pentoxifylline, and to estimate the antitumor response to this combination in previously treated breast cancer patients. Thirty-five previously treated advanced breast cancer patients received 70 cycles (median, 2 cycles/patient; range, 1-6) of 1600 mg of oral sustained release pentoxifylline every 8 h for 4 doses in combination with escalating doses of i.v. bolus thioTEPA 40-65 mg/m2 administered 3 h after the second dose of pentoxifylline. Thrombocytopenia was dose limiting at 65 mg/m2 of thioTEPA, and the MTD was defined as 60 mg/m2. Among 25 patients treated at the MTD, leukopenia was grade 2 in 9 patients (36%), grade 3 in 4 patients (16%), and grade 4 in 2 patients (8%); thrombocytopenia was grade 2 in 3 patients (12%), grade 3 in 4 patients (16%), and grade 4 in 3 patients (12%). No other thioTEPA-related toxicity was observed. Plasma concentrations of thioTEPA, TEPA, and pentoxifylline were measured in 6 patients. The median (range) area under the plasma concentration versus time curve for thioTEPA was 29.4 microM/h (26. 2-40.5) and for TEPA was 16.3 microM/h (9.2-21.7 microM-h). The median (range) maximal plasma concentration of pentoxifylline and major metabolites I, IV, and V were 1.2 microgram/ml (0.2-7.8), 4.0 microgram/ml (0.5-16.4), 0.4 (range 0.1-0.8), and 2.9 (1.1-5.5), respectively. No objective responses were observed among 21 evaluable patients treated at the MTD (95% confidence interval, 0-15%). The combination of pentoxifylline and thioTEPA is well tolerated but not active in previously treated advanced breast cancer patients. Further clinical trials using commercially available oral sustained release pentoxifylline as a modulator of alkylating agents are not warranted.

Analysis of 4-hydroxycyclophosphamide in human blood.

Cyclophosphamide is a prodrug activated by cytochrome P450 isozymes in the liver. The product of hepatic activation of cyclophosphamide is 4-hydroxycyclophosphamide. Previously reported methods for determining 4-hydroxycyclophosphamide were either impractical or unreliable for monitoring infusion pharmacokinetics in conjunction with clinical trials. One procedure in which a fluorescent hydroxyquinoline derivative was prepared from 4-hydroxycyclophosphamide and analyzed by HPLC appeared to work at first, but gradually lost its selectivity due to degradation of the column by the strongly acidic mobile phase. An alternative procedure was developed using a weakly acidic eluent and postcolumn treatment with trifluoroacetic acid. This provided for protonation of the hydroxyquinoline, required for sensitive fluorescence detection, but spared the column. The resulting assay was sensitive, selective, reproducible, and accurate. The method was used to monitor 4-hydroxycyclophosphamide pharmacokinetics during and after 4 day infusions of 1.5 g/m2-day of cyclophosphamide given to three patients. It was also used to measure the time-dependent disappearance of acrolein and 4-hydroxycyclophosphamide added to human blood from healthy donors and that of metabolically derived 4-hydroxycyclophosphamide in the blood of a patient treated with cyclophosphamide. Slower decomposition was observed in the latter two cases than in the blood spiked with acrolein. Reliable data were obtained from > 1000 determinations using the same column without significant degradation of its stationary phase.

High-dose ifosfamide, carboplatin, and etoposide pharmacokinetics: correlation of plasma drug levels with renal toxicity.

An autologous bone marrow transplant regimen of ifosfamide, carboplatin, and etoposide (ICE) has been developed as treatment for certain malignancies. At maximum tolerated doses renal insufficiency precludes dose escalation. The objective was to examine whether measurement of plasma drug levels early during treatment would provide warning of renal failure. Nine patients received a 96-h continuous infusion of ifosfamide 16,000 mg/m2, carboplatin 1600 mg/m2, and etoposide 1200 mg/m2. Pharmacokinetics, including drug levels and plasma concentration-time curves, of ifosfamide, ultrafiltrable platinum (uPt) and etoposide were analyzed and correlated with renal function. One of the nine patients developed anuric renal failure requiring hemodialysis. By 17 h from the start of infusion, this patient showed substantially higher drug levels of ifosfamide (200 vs mean 217 microM) and uPt (19 vs mean 10 microM) than those patients with preserved renal function. The 95% confidence intervals suggested that a 16-22 h ifosfamide level > 153 microM and an uPt level > microM predict the development of significant renal dysfunction. Although drug levels were substantially higher at 56 h, the serum creatinine did not yet reflect kidney injury. This study suggests that high plasma ifosfamide and uPt levels, analyzed early in the course of a 96-h infusion of high-dose ICE, provide warning of severe and potentially fatal renal injury. Since ICE has substantial activity in a number of malignancies, but significant renal morbidity, real-time pharmacokinetic-guided dosing may reduce treatment-related toxicity.

Cyclophosphamide pharmacokinetics: correlation with cardiac toxicity and tumor response.

BACKGROUND: Cyclophosphamide, which forms the nucleus for virtually all preparative regimens for autologous bone marrow transplantation (ABMT), is an alkylating agent of which cytotoxicity is not directly caused by the parent compound but by its biologically active metabolites. Its nonmyelosuppressive toxicity in the ABMT setting is cardiomyopathy. We attempted to determine any correlation between plasma levels of total cyclophosphamide and the subsequent development of cardiac dysfunction. PATIENTS AND METHODS: Analyses of plasma levels and the derivation of plasma concentration-time curves (area under the curve [AUC]) were performed in 19 women with metastatic breast carcinoma, who received a continuous 96-hour infusion of cyclophosphamide, thiotepa, and carboplatin (CTCb) with ABMT. The assay for total cyclophosphamide measures the inactive parent compound; reliable assays of the active metabolites of cyclophosphamide are not yet available. RESULTS: Six of 19 women developed moderate, but transient, congestive heart failure (CHF) as assessed by clinical and radiologic criteria. These patients had a significantly lower AUC of total cyclophosphamide (median, 2,888 mumol/L/h) than patients who did not develop CHF (median, 6,121 mumol/L/h) (P less than .002). Median duration of tumor response in these patients was also more durable; at least 22 months in patients with lower AUCs versus a median of 5.25 months in those with higher AUCs (P = .008). CONCLUSION: These pharmacokinetic data support the premise that enhancement of cyclophosphamide activation may lead to both greater tumor cytotoxicity and increased but reversible end-organ toxicity. Early analysis of pharmacokinetic data may allow modulation of cyclophosphamide administration in an attempt to enhance therapeutic efficacy.