Inference of population history using a likelihood approach

We introduce an approach to revealing the likelihood of different population histories that utilizes an explicit model of sequence evolution for the DNA segment under study. Based on a phylogenetic tree reconstruction method we show that a Tamura-Nei model with heterogeneous mutation rates is a fair description of the evolutionary process of the hypervariable region I of the mitochondrial DNA from humans. Assuming this complex model still allows the estimation of population history parameters, we suggest a likelihood approach to conducting statistical inference within a class of expansion models. More precisely, the likelihood of the data is based on the mean pairwise differences between DNA sequences and the number of variable sites in a sample. The use of likelihood ratios enables comparison of different hypotheses about population history, such as constant population size during the past or an increase or decrease of population size starting at some point back in time. This method was applied to show that the population of the Basques has expanded, whereas that of the Biaka pygmies is most likely decreasing. The Nuu-Chah-Nulth data are consistent with a model of constant population.

Elevated maternal serum relaxin concentrations throughout pregnancy in singleton gestations after superovulation

OBJECTIVE

To test the hypothesis that superovulation results in elevated maternal circulating relaxin concentrations throughout the second and third trimesters of pregnancy, independent of the pattern of hCG secretion.

METHODS

Two groups of women with singleton gestations were studied: a group of nine women who achieved pregnancy after stimulation with human menopausal gonadotropin and a group of six women who achieved pregnancy without prior stimulation. Peripheral blood samples were drawn approximately every 5 weeks throughout the second and third trimesters. Serum relaxin concentrations were measured using a human relaxin-specific enzyme-linked immunosorbent assay; hCG was measured by an immunofluorometric assay.

RESULTS

The stimulated group had significantly higher relaxin levels throughout pregnancy (P=.007, multivariate analysis of variance) than did nonstimulated controls. The mean relaxin level in stimulated patients was 1.78 ng/mL (95% confidence interval [CI] 1.5, 2.17) and in nonstimulated subjects the level was 0.73 ng/mL (95% CI 0.59, 1.25). Spline fits demonstrated that stimulated patients had higher relaxin levels throughout the second and third trimesters. There was no significant difference in hCG concentrations between the two groups (P=.61).

CONCLUSION

In singleton gestations after superovulation, maternal serum relaxin concentrations are significantly higher throughout the second and third trimesters of pregnancy. These differences are independent of the pattern of hCG secretion. It appears that luteal relaxin secretion is controlled by factors in addition to hCG.

[Pharmacokinetics of a new fluid theophylline sustained-release drug form. Microcapsules in a sachet]

A new sustained release theophylline (CAS 58-55-9) formulation was especially designed for the elderly and children. Microcapsules of theophylline, administered as a suspension in water, proved to be a suitable dosage form for a clientele with impaired or difficult deglutition. Pharmacokinetic characteristics of 2 batches at the lower (T1) and upper (T2) in vitro dissolution specification range of this new formulation and a pellet formulation (R) as a comparator were evaluated in an open, randomised, 3-way, multiple dose, crossover study with an asymmetric dosage regimen of 400 mg and 200 mg theophylline. Smooth and safe plasma concentrations with a high and long-lasting plateau were achieved with this new formulation. Plateau times which are independent of the asymmetric dosage regimen ranged from 16.4 h (T1) to 13.8 h (T2) and could therefore cover sufficient time of the dosage interval. Maximum plasma levels of 9.6 micrograms/ml and 10.0 micrograms/ml were attained 6.6 and 6.1 h after dosing of T1 and T2, coinciding perfectly with the time of the critical morning dip at 2-6 a.m. With a nocturnal excess of 15.5% (T1) and 17.9% (T2), this circadian-tailored asymmetric dosage regimen proved to take into account the chronopathology of asthma and the chronopharmacokinetics of theophylline sustained release preparations. Bioequivalence of all 3 formulations compared with each other with regard to rate (Cmax ss) and extent (AUCss) of absorption could be established for the 2 batches at the upper and lower in vitro specification range and for both batches of the new formulation compared to the reference. All in all, the safety and efficacy of this new liquid sustained release theophylline preparation could be established. Furthermore, in vitro specifications were justified according to current EC guidelines.

[Manufacture and in vitro characterization of a new fluid theophylline sustained-release form. Sachets with microcapsules for administration in a drinkable sustained-release suspension]

The administration of currently available theophylline (CAS 58-55-9) sustained release preparations with high drug doses (hard capsules, tablets) presents difficulties for certain patient groups as children and elderly, due to the large geometry of these dosage forms. Therefore, a suspension for easy administration based on the novel Liquitard technology was developed using theophylline microcapsules. This paper describes the manufacturing procedure of the new dosage form and its in vitro release characteristics as a function of various parameters. During manufacturing, the suspension-forming excipients are first granulated and then filled into sachets together with the microcapsules. The sustained release suspension is prepared by the patient himself immediately before administration. The in vitro release of theophylline from the dosage form is neither affected by the suspension-forming excipients nor by the drug amount. This allows for the manufacture of sachets with different drug strength maintaining the same qualitative composition. Furthermore, the in vitro release is independent of pH, osmolality, agitation and of the addition of surfactants and native bile to the dissolution medium. The new dosage form thus meets the current EC-guidelines for oral sustained release dosage forms. The in vitro limits of the dissolution testing were verified on the basis of the bioequivalence of the batches at the upper and lower specification limits.

[The effect of different variables on the in vitro dissolution of a theophylline sustained-release preparation]

In vitro dissolution studies are valuable tools to judge quality and stability of sustained release dosage forms and are often utilised to predict the in vivo performance. For this reason, in vitro dissolution experiments with varying pH, osmolarity, rotation speed, and with addition of surfactants were performed with a sustained release theophylline (CAS 58-55-9) dosage form (Bronchoretard). In order to mimic the physiological situation of the gastrointestinal tract more closely, the pH of the dissolution media was changed and human bile was added at different time points. The results obtained show that the in vitro dissolution of the dosage form differs only slightly for the parameters pH, osmolarity and stirring speed and always lies within in vivo verified dissolution limits. However, the addition of sodium dodecyl sulphate to the dissolution medium markedly altered the dissolution rate whereas addition of the physiologically surface active human bile did not change the dissolution rate. A comparison with in vivo results indicated, that only the physiologically adapted model guarantees reliable results whereas the addition of synthetic surfactants cannot allow for the prediction of bile or food effects. The meaning of in vitro dissolution tests thus is limited to development studies of dosage forms and to routine quality and stability control testing. For judging the in vivo characteristics in vitro studies have only limited value and have to be verified by pharmacokinetic studies.

Microencapsulation of the renin inhibitor FK906 by phase separation of ethylcellulose in cyclohexane

Microencapsulation of the renin inhibitor FK906 (tripeptide) by phase separation of ethylcellulose in cyclohexane was performed to obtain sustained release of the drug for a once-a-day application. Owing to the binding characteristics and to the very low solubility of FK906 in cyclohexane, microencapsulation can be performed after granulation of the drug with an inert filler, and no additional binder is required. Microcapsules with a particle size of 180-590 microns are obtained in a yield of 70%. Drug content determinations and SEM-micrographs reveal the almost complete incorporation of the polymer for the coating and the high quality of the microcapsule wall. Despite the strongly pH-dependent solubility of FK906 (.HCl) in water, the microcapsules show almost identical sustained-release curves at pH 1.2 and 6.0 (0.05 M phosphate buffer). This is explained by an acidic microenvironment inside the microcapsules at both pHs investigated and was attributed to the intrinsic physico-chemical properties of FK906 which help to overcome the buffer capacity of the phosphate buffer, pH 6.0, inside the microcapsules. This theory was confirmed by solubility experiments at pH 6.0 using excess amounts of FK906 as well as by dissolution tests as a function of the buffer capacity and the osmolality of the dissolution medium. The buffer capacity was found to be the parameter with greater influence on the release rate.

Cerebrospinal fluid levels of biopterin, nitric oxide metabolites, and immune activation markers and the clinical course of human cerebral malaria

Cerebrospinal fluid samples from 130 children who presented with cerebral malaria were investigated to elucidate the impact of biopterin production, NO formation, and local immune activation on the clinical course of this disease. Biopterin levels were significantly lower in patients who were in a deeper coma (P = .02). Cerebrospinal fluid concentrations of NO were significantly higher in children who died than in survivors (P = .037); however, this was not the case for macrophage activation markers, neopterin, and soluble tumor necrosis factor receptor p75 (sTNFR-75). Biopterin, neopterin, and sTNFR-75 but not NO concentrations were significantly related to each other. Low biopterin levels in deep coma are compatible with an impaired local Th1 response, but the low levels could also be due to the scavenging of radicals or to decreased neurotransmitter synthesis. Local production of NO, most likely by nonimmune mechanisms, may be detrimental in cerebral malaria; however, this appears not to be the case for local Th1-mediated immune pathways.

Demonstration of a relaxin receptor and relaxin-stimulated tyrosine phosphorylation in human lower uterine segment fibroblasts

To elucidate the mechanism of relaxin action, we studied the binding characteristics of human relaxin and its effects on intracellular concentrations of cAMP and tyrosine phosphorylation of cellular proteins in a model system of human cervix, human lower uterine segment fibroblasts. Human relaxin labeled with 125I bound specifically to a single class of high-affinity relaxin binding sites, distinct from insulin receptors, with a mean (+/-SEM) dissociation constant (Kd) of 4.36 +/- 1.7 x 10(-9) M and a mean of 3220 +/- 557 binding sites per cell in human lower uterine segment fibroblasts. Relaxin, in quantities that were shown previously to stimulate intracellular levels of cAMP in other cell types, had no effect on intracellular levels of cAMP in human lower uterine segment fibroblasts even in the presence of the phosphodiesterase inhibitor 3-isobutyl-1-methyl-xanthine (IBMX). Incubation of the cells with relaxin caused a significant increase in tyrosine phosphorylation of a protein with an apparent Mr of approximately 220 kDa in these cells. In concert with results of recent studies that demonstrated that the Mr of the relaxin receptor is approximately 220 kDa, our data suggest that the phosphorylated protein is likely to be the relaxin receptor.

Prolonged macrophage activation and persistent anaemia in children with complicated malaria

OBJECTIVE

To determine if prolonged immune activation may be associated with the persistence of anaemia after treatment for severe malaria, we measured serum concentrations of neopterin and interleukin-4 during one week of antimalarial therapy and determined haemoglobin levels one month later. Neopterin is a clinically valuable marker for monitoring activation of macrophages by gamma-interferon and thus reflects the TH-1 immune response. Interleukin-4 is a major cytokine that tends to be inhibited by TH-1 activity.

METHOD

The study population consisted of 26 Zambian children < 6 years of age who presented with cerebral malaria to a rural hospital in 1994 and who were treated with quinine for seven days. Six children (23%) were anaemic (haemoglobin < 11 g/dl) one month after completing antimalarial therapy.

RESULTS

On admission, concentrations of neopterin were markedly elevated in all patients. During the seven days of anti-malarial therapy, neopterin levels remained elevated in the 6 children who proved to have persistent anaemia one month after finishing treatment but declined significantly (P = 0.008) in the 20 children who corrected their haemoglobin levels by that time. Conversely, interleukin-4 levels declined in the children with persistent anaemia (P = 0.043) but not in the other children.

CONCLUSION

Persistence of the TH-1 mediated immune response and associated activation of macrophages may be involved in the pathogenesis of lingering anaemia after treatment of malaria.

Interleukin-2-based therapy for metastatic renal cell cancer: the Cytokine Working Group experience, 1989-1997

PURPOSE

This article reviews long-term follow-up data from three phase II studies conducted by the Cytokine Working Group from 1989 to 1995 that evaluated various recombinant interleukin-2 (rIL-2) -based regimens in patients with metastatic renal cell cancer. Response rates, long-term response duration, and toxicity are compared.

PATIENTS AND METHODS

The Cytokine Working Group studies reviewed here investigated the safety and efficacy of two high-dose intravenous rIL-2-based regimens and two moderate-dose outpatient subcutaneous rIL-2-based regimens in patients with progressive metastatic renal cell cancer. A randomized phase II study, initiated in 1989, investigated the safety and efficacy of high-dose intravenous rIL-2 alone and high-dose intravenous rIL-2 plus recombinant interferon-alpha (rIFN-alpha). A second phase II study, initiated in 1992, tested the safety and efficacy of moderate-dose subcutaneous rIL-2 plus subcutaneous rIFN-alpha in the outpatient setting. The third trial, initiated in 1995, investigated a regimen consisting of the previous subcutaneous rIL-2 plus rIFN-alpha regimen alternating with intravenous bolus 5-fluorouracil (5-FU) plus subcutaneous rIFN-alpha. Median follow-up for these studies is 72 months, 48 months, and 24 months, respectively.

RESULTS

The overall response rates observed with each of these regimens were similar (17% with high-dose rIL-2 alone, 11% with high-dose rIL-2/rIFN-alpha, 17% with outpatient subcutaneous rIL-2/rIFN-alpha, and 16% with outpatient rIL-2/rIFN-alpha, plus 5-FU/rIFN-alpha). However, the high-dose rIL-2 regimen produced a 7% complete response rate, compared with 0%, 4%, and 4%, respectively, with each of the other regimens. Median response duration was also much longer with high-dose intravenous rIL-2 alone (53 months), compared with 7 months, 12 months, and 9 months, respectively, with each of the other regimens.

CONCLUSION

Complete response rate and response duration appear to favor the high-dose intravenous rIL-2 regimen. This will require verification in a randomized study comparing the best high-dose arm (rIL-2 alone) with the best outpatient regimen (rIL-2/IFN-alpha). The Cytokine Working Group is currently conducting such a study.

Mechanism of suppression of macrophage nitric oxide release by IL-13: influence of the macrophage population

IL-13 is a cytokine produced by T lymphocytes, mast cells, basophils, and certain B cell lines that up-regulates or inhibits various macrophage functions. In the present study we analyzed the mechanisms of suppression of nitric oxide (NO) release by IL-13 in the macrophage cell line J774A.1 and in thioglycolate-elicited mouse peritoneal macrophages. In both cell types efficient reduction (>80%) of NO production required treatment of the macrophages with IL-13 for at least 7 h before stimulation with IFN-gamma and LPS. In J774A.1 cells, increasing concentrations of IFN-gamma partially antagonized the suppression mediated by IL-13, whereas in peritoneal macrophages, the inhibitory effect of IL-13 was largely independent of the concentrations of IFN-gamma and LPS. In J774A.1 cells, IL-13 strongly reduced both the mRNA and protein levels of inducible nitric oxide synthase (iNOS, NOS-2), as determined by Northern blot analysis and immunoprecipitation. In peritoneal macrophages, in contrast, IL-13 decreased iNOS protein and enzyme activities after 8 to 48 h of stimulation, without altering the expression of iNOS mRNA. Pulse labeling with [35S]methionine revealed that IL-13 caused a 4.7-fold reduction of the de novo synthesis of iNOS protein in these cells. These data demonstrate for the first time that IL-13 is capable of regulating iNOS at both the mRNA and translational levels and underline the important influence of the macrophage population when studying mechanisms of cytokine functions.

Mechanism of suppression of macrophage nitric oxide release by IL-13: influence of the macrophage population

IL-13 is a cytokine produced by T lymphocytes, mast cells, basophils, and certain B cell lines that up-regulates or inhibits various macrophage functions. In the present study we analyzed the mechanisms of suppression of nitric oxide (NO) release by IL-13 in the macrophage cell line J774A.1 and in thioglycolate-elicited mouse peritoneal macrophages. In both cell types efficient reduction (&gt;80%) of NO production required treatment of the macrophages with IL-13 for at least 7 h before stimulation with IFN-gamma and LPS. In J774A.1 cells, increasing concentrations of IFN-gamma partially antagonized the suppression mediated by IL-13, whereas in peritoneal macrophages, the inhibitory effect of IL-13 was largely independent of the concentrations of IFN-gamma and LPS. In J774A.1 cells, IL-13 strongly reduced both the mRNA and protein levels of inducible nitric oxide synthase (iNOS, NOS-2), as determined by Northern blot analysis and immunoprecipitation. In peritoneal macrophages, in contrast, IL-13 decreased iNOS protein and enzyme activities after 8 to 48 h of stimulation, without altering the expression of iNOS mRNA. Pulse labeling with [35S]methionine revealed that IL-13 caused a 4.7-fold reduction of the de novo synthesis of iNOS protein in these cells. These data demonstrate for the first time that IL-13 is capable of regulating iNOS at both the mRNA and translational levels and underline the important influence of the macrophage population when studying mechanisms of cytokine functions.

Unidirectional upregulation of the synthesis of the major iron proteins, transferrin-receptor and ferritin, in HepG2 cells by the acute-phase protein alpha1-antitrypsin

BACKGROUND/AIMS

We have previously shown that the hepatic acute-phase protein alpha1-antitrypsin (alpha1-AT) is an important mediator of changes in iron metabolism in the course of anaemia of chronic disease. Alpha1-AT profoundly reduces growth of erythroid cells by interfering with transferrin-mediated iron uptake. In the present work we investigate the effects of alpha1-AT on hepatic iron metabolism, as the liver plays a central role in body iron metabolism and in metabolic changes during acute-phase response.

METHODS

The human hepatoma cell line Hep G2 was cultured in RPMI 1640+10% FCS. The effect of alpha1-AT on transferrin-receptor binding was investigated in equilibrium binding assays with 125I-transferrin. Expression of transferrin receptor was determined by saturation experiments and intracellular ferritin was measured in cell lysates after incubating cells either alone or with alpha1-AT. To determine iron regulatory protein binding activity to iron responsive elements we used gel retardation assays and Northern blot analysis was carried out to investigate transferrin receptor and ferritin mRNA expression.

RESULTS

Alpha1-AT completely prevented transferrin from binding to its receptor and internalization of the transferrin-transferrin receptor complex on HepG2. In addition, alpha1-AT caused a distinct increase in iron regulatory protein binding activity to iron responsive elements, which is characteristic of iron deprivation. Normally, the synthesis of transferrin receptor and ferritin is regulated bidirectionally, but alpha1-AT promoted a unidirectional regulation. Alpha1-AT increased the synthesis of both transferrin receptor and ferritin and, moreover, increased cellular amounts of transferrin receptor mRNA and ferritin H-chain mRNA.

CONCLUSIONS

The effect of alpha1-AT on transferrin receptor synthesis appears to be mediated via activation of iron responsive element binding affinity of iron regulatory protein leading to an increased stability of transferrin receptor mRNA. Changes in ferritin, however, may be related to a transcriptionally mediated, iron-independent pathway which overrides the influence of activated iron regulatory protein. These specific changes in iron metabolism are the very ones seen in the course of anaemia of chronic disease. Our results emphasize the central role of alpha1-AT as a mediator of altered iron metabolism, characteristic of anaemia of chronic disease, not only with respect to erythroid cells but also with respect to liver cells.

Phase I study of daily times five topotecan and single injection of cisplatin in patients with previously untreated non-small-cell lung carcinoma

BACKGROUND

The objectives were to determine the dose-limiting toxicity of topotecan in combination with cisplatin, to describe the principal toxicities, and to define the maximally-tolerated doses of the drugs in previously untreated patients with advanced non-small-cell lung carcinoma.

PATIENTS AND METHODS

The study was designed to evaluate escalated doses of topotecan (starting at 0.75 mg/m2/day) as a 30-minute infusion daily for five consecutive days with a fixed clinically-relevant dose of 75 mg/m2 cisplatin given on day 1, every three weeks.

RESULTS

Fifteen chemotherapy-naive patients entered the study and 14 were evaluable for toxicity. All 11 patients treated at the first topotecan/cisplatin dose level of 0.75/75 mg/m2, experienced at least one episode of grade 4 neutropenia. For six patients, absolute neutrophil counts were below 500/ml for more than five days, and two of them developed a grade 4 thrombocytopenia. At the next higher topotecan/cisplatin dose level (1.0/75 mg/m2), grade 4 neutropenia lasting longer than five days occurred in all three evaluable patients, including one patient who expired due to a severe neutropenia associated with sepsis. Non-hematologic toxicities, predominantly nausea and vomiting, were mild to moderate in severity and manageable. Four patients had partial responses (30.7%; 95% confidence interval (9%-61%) of relatively short duration.

CONCLUSION

Both severe neutropenia and thrombocytopenia precluded dose escalation of topotecan and cisplatin administered on this schedule. In previously untreated patients, the first topotecan/cisplatin dose level (0.75/75 mg/m2), was associated with intolerable myelosuppression, and, therefore, the dose levels evaluated in this study cannot be recommended for subsequent phase II investigations. The high toxicity of this schedule and the recent understanding of the pharmacokinetic interaction between those drugs may encourage the investigation of the alternate sequence of cisplatin after TPT in phase II studies.

A coalescent approach to the polymerase chain reaction

A versatile algorithm is developed to model PCR on a computer. The method is based on a modification of the coalescent process and provides a general framework to analyse data from PCR. It allows for incorporation of the dynamics of the replication process as described in terms of the number of starting template molecules and cycle-dependent PCR efficiency. The simulation method generates, as a first step, the genealogy of a set of sequences sampled from a final PCR product. In a second step a mutation process is superimposed and the resulting data set is analysed. The efficiency of our algorithm enables us to get reliable approximations of various sample distributions. We demonstrate the relevance of our method with two applications: maximum likelihood estimation of the error rate in PCR and a test of homogeneity of the template.

Divergent effects of hemodialysis and continuous ambulatory peritoneal dialysis on cardiac diastolic function

OBJECTIVE

To investigate the effects of dialysis procedures on cardiac diastolic function.

DESIGN

Comparative, nonrandomized matched pair study.

SETTING

Nephrology and cardiology departments at a university hospital.

PATIENTS

Thirty-four patients on hemodialysis (HD) (n = 17) and continuous ambulatory peritoneal dialysis (CAPD) (n = 17), matched by sex, age, duration of dialysis treatment, and presence/absence of diabetes.

MEASUREMENTS

Cardiac function was estimated by means of M-mode, two-dimensional, and spectral Doppler echocardiography, and results were statistically evaluated by means of univariate and multivariate analytical procedures.

RESULTS

Although not statistically significant, trends towards differences between the two patient groups were detected for left ventricular mass (p = 0.083) and parameters of diastolic function (p = 0.079). These differences in left ventricular performance and diastolic function between HD and CAPD patients were also evident when calculating Spearman rank correlation coefficients. Left ventricular mass and diastolic function were closely correlated to each other in all dialysis patients. Moreover, by means of a multivariate analytical procedure (Hotelling T-square test), diversities in diastolic function between the two patient groups could be clearly established (p = 0.037), with more impaired diastolic function in HD patients. In addition, cardiac performance was shown to depend to a certain extent on hemoglobin concentration.

CONCLUSION

Clear differences in diastolic function and cardiac performance were evident between CAPD and HD patients. From the data of our pilot study, it may be speculated whether decrease of left ventricular mass could be beneficial for the improvement of diastolic function and cardiac hemodynamics in dialysis patients.

Modulation of transferrin receptor expression by dexrazoxane (ICRF-187) via activation of iron regulatory protein

Dexrazoxane (ICRF-187) has recently been demonstrated to reduce cardiac toxicity induced by chemotherapy with anthracyclines, although the reason for this phenomenon has remained obscure thus far. In order to investigate whether ICRF-187 might exert its effects by modulating iron metabolism, we studied the drug's potential to influence the maintenance of iron homeostasis in two human cell lines. We demonstrate that ICRF-187 enhanced the binding affinity of iron regulatory protein (IRP), the central regulatory factor for posttranscriptional iron regulation, to RNA stem loop structures, called iron responsive elements (IRE), in THP-1 myelomonocytic as well as K562 erythroleukemic cells. Increased IRE/IRP interaction was paralleled by an elevation of transferrin receptor (trf-rec) mRNA levels which, according to the well-established mechanism of posttranscriptional iron regulation, was likely due to stabilisation of trf-rec mRNA by IRP. Subsequently, ICRF-187 treatment of cells increased trf-rec surface expression and enhanced cellular iron uptake. All these events, i.e. IRP activation, stabilisation of trf-rec mRNA and increased surface expression of the protein in response to ICRF-187, follow a dose-response relationship. Increased cellular uptake and sequestration of iron in response to ICRF-187 may contribute to the protective activity of ICRF-187 by reducing the iron-anthracycline complex and iron-catalysed generation of hydroxyl radicals via the Haber-Weiss reaction.

Outpatient subcutaneous interleukin-2 and interferon-alpha for metastatic renal cell cancer: five-year follow-up of the Cytokine Working Group Study

PURPOSE

A phase II trial of outpatient subcutaneous (SC) interleukin-2 (rIL-2) plus interferon-alpha (IFN-alpha 2B) was performed in patients with metastatic renal cell cancer. A 5-year follow-up of that Cytokine Working Group study is presented.

PATIENTS AND METHODS

Forty-seven patients meeting eligibility criteria of previous Cytokine Working Group studies were treated on an outpatient basis with SC rIL-2 (Chiron, Emeryville, CA), 5 x 10(6) IU/m2/dose q 8 hr x 3, then daily, 5 days per week, and IFN-alpha 2B (Schering-Plough, Kenilworth, NJ), 5 x 10(6) IU/m2/dose three times weekly for 4 weeks. After a 2- to 4-week break, patients were scheduled to continue treatment for up to six cycles.

RESULTS

There were two complete and six partial responders (17% response rate, 95% CI: 8%-31%). Median duration of response was 12 months (range 1-49+ months), with complete responses of 15 and 49+ months. Responding sites of disease included lung, nodes, soft tissue, bone, and liver. Dose and schedule were adjusted to control toxicity at grade 2/3 levels, with 50% requiring dosage alterations. Grade 2/3 toxicity included fatigue, nausea/vomiting, diarrhea, anorexia, fluid overload, rash, CNS, injection site pain, chest pain/palpitations (including atrial fibrillation requiring treatment, two patients), and hypotension. Grade 4 toxicity included dehydration (seven patients), vomiting (one patient), and irreversible renal failure with crescentic glomerulonephritis requiring dialysis (one patient).

CONCLUSION

SC rIL-2 plus IFN-a2B is tolerated in the outpatient setting with frequent dose adjustments. The overall response rate of this regimen is similar to that seen with high-dose rIL-2 alone; however, the response duration appears to be shorter.

Prospective randomized trial of lisofylline for the prevention of toxicities of high-dose interleukin 2 therapy in advanced renal cancer and malignant melanoma

The therapeutic application of high-dose interleukin (IL) 2 in human malignancy is limited by severe multiorgan toxicities that are mediated, in part, by tumor necrosis factor (TNF) and IL-1. CT1501R (lisofylline; LSF) is one of several methyl xanthine congeners that inhibit the effects of TNF by the interruption of specific signal transduction pathways. This randomized, placebo-controlled trial was designed to assess the activity of LSF in reducing the toxicities of high-dose IL-2 therapy. Fifty-three patients with metastatic renal cancer or malignant melanoma were treated with i.v. bolus IL-2, 600, 000 IU/kg every 8 h for 5 days (14 doses), followed by 9 days of rest and another 5-day course of IL-2. Patients were randomly assigned to LSF, 1.5 mg/kg i.v. bolus, or placebo every 6 h during IL-2 therapy. All patients were to be treated to individual maximum tolerance of IL-2 at the intensive care unit level of support. The end points for statistical analysis were the number of IL-2 doses administered during the first cycle of treatment (maximum, 28) and the toxicities experienced by each group after the first 8 planned IL-2 doses. There was no difference between the LSF and placebo groups in the mean number of IL-2 doses tolerated in the entire first cycle of therapy (19.6 +/- 5.4 versus 19.5 +/- 5.8, P = 0.86) or in the first or second 5-day course of IL-2. The only significant difference in toxicities occurring through the eighth dose of IL-2 was in the maximum elevation of serum creatinine (mean, 1.7 +/- 0.8 for placebo versus 1.5 +/- 0.6 mg/dl for LSF, P = 0.013). A Monte Carlo analysis of major toxicities over the first 14-dose course of therapy showed a statistically significant difference favoring the LSF-treated group (P = 0.025). LSF was well tolerated, associated only with mildly increased nausea (P = 0.006 after eight IL-2 doses, but not significant for the entire first cycle). The antitumor activity was comparable in both groups (objective responses, 2 of 28 with LSF versus 4 of 24 with placebo). The mean peak plasma concentrations of LSF on days 1, 5, and 19 were 6.24, 3.83, and 5.04 micromol/liter, respectively. In conclusion, with this dose and schedule, LSF did not alter the toxicities of high-dose i.v. IL-2 sufficiently to impact the overall dose intensity of IL-2. Successful IL-2 toxicity modulation may require the use of higher doses of LSF, the development of agents with more potent anti-TNF activity, and/or combined modulating agents that function via distinct mechanisms to interrupt cytokine-mediated signaling.

Regulation of cellular iron metabolism by erythropoietin: activation of iron-regulatory protein and upregulation of transferrin receptor expression in erythroid cells

Erythropoietin (Epo) is the central regulator of red blood cell production and acts primarily by inducing proliferation and differentiation of erythroid progenitor cells. Because a sufficient supply of iron is a prerequisite for erythroid proliferation and hemoglobin synthesis, we have investigated whether Epo can regulate cellular iron metabolism. We present here a novel biologic function of Epo, namely as a potential modulator of cellular iron homeostasis. We show that, in human (K562) and murine erythroleukemic cells (MEL), Epo enhances the binding affinity of iron-regulatory protein (IRP)-1, the central regulator of cellular iron metabolism, to specific RNA stem-loop structures, known as iron-responsive elements (IREs). Activation of IRP-1 by Epo is associated with a marked increase in transferrin receptor (trf-rec) mRNA levels in K562 and MEL, enhanced cell surface expression of trf-recs, and increased uptake of iron into cells. These findings are in agreement with the well-established mechanism whereby high-affinity binding of IRPs to IREs stabilizes trf-rec mRNA by protecting it from degradation by a specific RNase. The effects of Epo on IRE-binding of IRPs were not observed in human myelomonocytic cells (THP-1), which indicates that this response to Epo is not a general mechanism observed in all cells but is likely to be erythroid-specific. Our results provide evidence for a direct functional connection between Epo biology and iron metabolism by which Epo increases iron uptake into erythroid progenitor cells via posttranscriptional induction of trf-rec expression. Our data suggest that sequential administration of Epo and iron might improve the response to Epo therapy in some anemias.

Modulatory potential of iron chelation therapy on nitric oxide formation in cerebral malaria

To determine whether iron chelation modulates nitric oxide (NO) formation and cell-mediated immune effector function in children with cerebral malaria, serum concentrations were measured of the stable end products of NO, nitrite and nitrate (NO2-/NO3-), interleukin (IL)-4, -6, and -10, and neopterin in 39 Zambian children enrolled in a placebo-controlled trial of desferrioxamine B and quinine therapy. Mean concentrations of NO2-/NO3- increased significantly over 3 days in children receiving desferrioxamine plus quinine but not in those given placebo and quinine. Neopterin levels declined significantly with placebo but not with desferrioxamine. IL-4 levels increased progressively in the placebo group and ultimately decreased in the desferrioxamine group, but the trends were not statistically significant. IL-6 and IL-10 levels were elevated initially and decreased significantly in both groups over 3 days. These data are consistent with the hypothesis that iron chelation therapy in children with cerebral malaria strengthens Th1-mediated immune effector function involving increased production of NO.

[Cellular and humoral functions in acute pancreatitis]

Infectious complications are the leading cause of death in acute pancreatitis. Individual factors of immune defence could be of significance, whether or not a patient develops a severe course with infectious complications. In a prospective 5-year trial including 72 patients, we investigated 29 cellular and humoral markers of the body's defence system for their potential to indicate the severity and course of acute pancreatitis. Complement factors C3 and C4 as well as immunoglobulins IgG, IgM and IgA were normal, in general. Measurable levels of IL-1 alpha, IL-1 beta, IL-2 and sIL-2R could be detected only occasionally. Values of alpha 1-AT, TNF-alpha, TNF alpha-Rp75, neopterin, sICAM-1, IL-8, IL-1RA and sIL-6R did not correlate with a severe course. Due to the high magnitude of increase, CRP, IL-6 and granulocyte elastase were the best indicators of the inflammatory process. Delayed-type hypersensitivity response was the only early predictor of a severe course. It was superior over other cellular markers such as monocyte count or CD4+/CD8+ ratio. In vitro function of polymorphonuclear granulocytes (PMN) was not adequate to the severity of the disease already during the first week of illness. During further course, PMN motility and capacities to produce reactive oxygen species even worsened. The compromized PMN function could explain the frequent development of infectious complications in patients suffering from severe pancreatitis. These results should encourage new concepts of infection prophylaxis using stimulants of cellular defence.