Simplified method for the analysis of cellular karyotype and phenotype in leukemias

The objective of this study was to develop a simplified method for the simultaneous analysis of cellular karyotype and phenotype which would permit the identification of cell origin. We studied 6 patients with AML, 3 with CML (one of which was in blastic transformation) and one ALL. We used a method in which the suspension of bone marrow cells was incubated in TC 199 medium with colchicine and with hypotonic solution formed from glycerol, NaCl, KCl, CaCl2, MgCl2 and sucrose. The slides were prepared from this cell suspension by cytospin and stained for peroxidase, PAS, esterases and iron. The karyotype was studied by direct method and culture. It was possible to relate the cytogenetic marker with cytochemistry characteristics in the same cell in 3 cases, showing the feasibility of cytochemistry techniques in cytogenetical preparations. The best preparations were found through peroxidase. The presence of iron granules allowed identification of erythroblastic lineage in the combined staining. Mitosis with a marker chromosome of leukemic clone in an AML cell with negative peroxidase probably showed a proliferation of more primitive precursor not sufficiently differentiated to show markers.

The combination of quercetin and cytosine arabinoside synergistically inhibits leukemic cell growth

It has been demonstrated that quercetin (3,3',4',5,7-pentahydroxyflavone) inhibits the growth of several cancer cell lines and that the antiproliferative activity of this substance is probably mediated through a binding interaction with type II estrogen binding sites (type II EBS). The effect of quercetin and cytosine arabinoside (Ara-C) alone or in combination, was tested on HL-60 cell growth. Quercetin significantly synergized the inhibitory activity of Ara-C on HL-60 cell growth while rutin, the 3-rhamnosylglucoside of quercetin, neither competed with [3H]estradiol for type II EBS nor was effective alone or in combination with Ara-C. Based on these results, we studied by a clonogenic assay the effect of quercetin and Ara-C alone and in combination on colony formation by human leukemic cells (CFU-L). In all cases both drugs exhibited a dose-related inhibition of CFU-L in a range of concentrations between 10 nM and 10 microM and 0.01 nM and 10 microM for quercetin and Ara-C, respectively. The combination of the two drugs resulted in a synergistic inhibitory activity on CFU-L. Considering that plasma concentrations of quercetin effective in vitro were obtained in vivo without any apparent side effects, we conclude that this report represents further experimental evidence that quercetin could be used in the treatment of acute leukemias.

Polymerase chain reaction analysis of BCR-ABL sequences in adult Philadelphia chromosome-negative acute lymphoblastic leukemia patients

The Philadelphia (Ph) translocation is the most common cytogenetic abnormality in adult acute lymphoblastic leukemia (ALL) and is associated with an adverse prognosis. Using polymerase chain reaction (PCR) technology we recently observed a remarkably high incidence (55%) of BCR-ABL rearrangements in adult common ALL patients. In the present study we asked whether a subset of Ph-negative cALL, similarly to Ph-negative chronic myelocytic leukemia (CML) patients, exhibit BCR-ABL transcripts. PCR analysis of 58 adult Ph-negative cALL patients, including 47 cases with a normal karyotype revealed no evidence of chimeric BCR-ABL genes. We conclude that Ph-negative BCR/ABL-positive ALL is very rare entity if existing at all.

Comparison of a new high-performance liquid chromatography method with fluorescence polarization immunoassay for analysis of methotrexate

A simple high-performance liquid chromatography (HPLC) method for the determination of methotrexate (MTX) in biological fluids is described. The assay is rapid, the time required for analysis is less than 30 min, and it is sensitive, up to 0.01 microgram/ml, which is three times below the toxic MTX concentration. Fifty plasma samples drawn from acute lymphocytic leukemia (ALL) patients were used to compare this method with that of fluorescence polarization immunoassay (FPIA). A good correlation (r = 0.979) was obtained between the results of the two analyses. FPIA constantly overestimates the concentration in samples collected during elimination and underestimates those collected during infusion. The difference between the means of the two methods was 29% and 13% for the elimination and infusion samples, respectively. The means of the peak height ratio of the metabolite to MTX in the HPLC chromatograms were 3.39 and 0.33 during elimination and infusion, respectively. The results therefore indicate that HPLC is more specific when tracing the washout of MTX concentration. Because of this specificity and simplicity, the method is recommended for therapeutic drug monitoring. The stability of MTX in human saliva was investigated in this study. MTX was found to be stable at room temperature and at -20 degrees C for a minimum of 3 h and 3 weeks, respectively.

Compositional changes in vertebral bone marrow during treatment for acute leukemia: assessment with quantitative chemical shift imaging

A modified Dixon chemical shift imaging technique was used to quantify longitudinal changes in bone marrow that occur during induction chemotherapy in patients with acute leukemia. Results were correlated with those of bone marrow biopsy. Forty-seven quantitative images were obtained with a 0.6-T whole body imager in a total of 11 patients over the course of treatment. Quantitative measures of fat fractions and water and fat component T1 and T2 relaxation times were determined, as well as average relaxation times. Imaging results showed sequential increases in fat fractions among responding patients (n = 9), consistent with biopsy-confirmed clinical remission. In the two patients who later relapsed, sharp decreases in fat fractions were noted. In the two patients who failed to regenerate normal marrow, unchanging, low fat fractions were seen. Water component T1 values reflected posttherapeutic changes in the hematopoietic elements. Quantitative chemical shift imaging proved useful in assessing treatment response in acute leukemia during early bone marrow regeneration and, later, in ascertaining remission or relapse.

Low frequency of ras oncogene mutations in Philadelphia-positive acute leukemia and report of a novel mutation H61 Leu in a single case

Activating ras mutations are frequent (25-60%) in chronic myelomonocytic leukemia (CMML) and in acute myeloid leukemia (AML) (30%), in contrast to chronic myeloid leukemia (CML) in which the incidence is very low (0-3%). This might reflect that the leukemic cell in CML is at a level of differentiation in which ras gene activation is not involved or, alternatively, might be due to the presence in CML of the bcrlabl fused gene. We have analyzed the presence of point mutations in codons 12, 13, 59, 61 and 63 of N-, K-, and H-ras genes, in 26 cases of Philadelphia-chromosome-positive, bcrlabl-positive acute leukemia (Ph+ AL), and in eight CMML cases by using the polymerase chain reaction. Aberrant ras genes were detected in a single Ph+ AL case, and in four out of eight CMML patients. The Ph+ AL showing altered ras allele had an unusual point mutation in H-ras gene, substituting leucine for glutamine. This mutation has not been previously found in any hematological disease. Our findings suggest that ras mutations are probably not involved in the pathogenesis of those leukemias in which blast cells contain bcrlabl oncogene activation.

Porphyrin metabolism in some malignant diseases

Porphyrin metabolism was studied in 21 children of both sexes suffering from acute lymphoblastic leukaemia (ALL) and 34 adult patients of different ages and sexes suffering from ALL (n = 14), non-Hodgkin's lymphoma (NHL), n = 14, or Hodgkin's disease (HD), n = 6. In addition, two groups of healthy children (n = 14), and adults (n = 17) were studied for comparison. It was apparent from this study that the activity of uroporphyrinogen-1-synthetase (URO-1-S, E.C. 4.3.1.8) was highly significantly activated in the blood of children, while the activities of blood 5-aminolevulinic acid dehydrase (E.C. 4.2.1.24) and ferrochelatase (E.C. 4.99.1.1.), as expressed by protoporphyrin/haem ratio, were inhibited in those children. Also, free erythrocyte total porphyrins were increased, while the haem content was reduced. The concentrations of 5-aminolevulinic acid, coproporphyprin and uroporphyrin were increased in the urine of children with ALL. On the other hand, some dramatic changes were found in porphyrin metabolism in adult patients suffering from ALL, NHL and HD. The aforementioned disturbances were discussed in the light of some factors which may affect the enzymatic activities in the synthesis of porphyrins.

Rational use of methotrexate in maintenance therapy of childhood acute lymphoblastic leukemia

This study was undertaken to research the pharmacokinetics and bioavailability of methotrexate (MTX). Plasma concentrations were measured by fluorescent spectrometry in 20 normal SD rats, and 28 measurements were done in children with acute lymphoblastic leukemia (ALL). Both rats and children were divided into four groups. Either 20 mg/m2 or 40 mg/m2 of MTX was given IV or PO in each group. The plasma MTX concentrations were measured within 8 hours after administration. The concentration versus time curves were fitted by MCPKP program for pharmacokinetics (PK) and the parameters calculated. After PO administration, the peak concentration, duration of therapeutic concentration and bioavailability were much lower than that after IV administration. The differences were more obvious at 40 mg/m2 dosage. The higher the PO dosage, the lower the bioavailability. Absorption of PO MTX in children with ALL varied widely and uniform concentration was not expected even after equal dosage. Drug concentration was not necessarily increased with dosage. It is our conclusion that drug concentrations and PK parameters should be measured in patients receiving PO MTX therapy.

Energy intake and basal metabolic rate during maintenance chemotherapy

Energy intakes and basal metabolic rates were determined in 26 children receiving chemotherapy in remission from acute lymphoblastic leukaemia or solid tumours and 26 healthy controls matched for age and sex. Body weight and height on the two groups were comparable, although one patient was stunted (height for age) and three others wasted (weight for height). Energy intake in the patients at 7705 kJ/day (1842 kcal) and controls at 7773 kJ/day (1866 kcal)) and basal metabolic rate (BMR) in the patients at 4873 kJ/day (1172 kcal) and controls 4987 kJ/day (1196 kcal) for the two groups were not significantly different. Although the energy intake:BMR ratio for both groups was 1.59, the range of values for the patient group was large (0.96-2.73) and appeared to be greater than that observed in the control group (1.23-2.46). These results demonstrated that during this period of chemotherapy there was no evidence of raised energy expenditure at rest or reduced energy intake in the patient group. No indication of undernutrition in the patients as a group was evident, although some individuals might require further clinical nutritional assessment.

Effects of chemotherapy and remission on carbohydrate metabolism in dogs with lymphoma

After a 12-hour fast, blood samples were obtained from 27 dogs with previously untreated lymphoma before and 5, 15, 30, 45, and 60 minutes after an intravenous (IV) challenge with 500 mg/kg dextrose. This procedure was done for each dog before up to five treatments with the IV doxorubicin (30 mg/m2 every 3 weeks). All dogs achieved a complete remission. Samples were assayed for glucose, lactate, and insulin concentrations, and results were compared statistically with those from 16 normal control dogs of similar weight and age undergoing an identical dextrose challenge before and 3 weeks after receiving one dose of IV doxorubicin (30 mg/m2). Glucose, lactate, and insulin concentrations did not change significantly in response to glucose challenge in control dogs after doxorubicin chemotherapy. Lactate and insulin concentrations in untreated dogs with lymphoma were significantly higher than controls. This hyperlactatemia and hyperinsulinemia did not improve when dogs with lymphoma were put into remission with doxorubicin chemotherapy. The results indicate that carbohydrate metabolism is altered in dogs with lymphoma, and that these abnormalities do not improve when a complete remission is obtained with doxorubicin chemotherapy.

Phenotypic analysis of 1-B-D-arabinofuranosylcytosine deamination in patients treated with high doses and correlation with response

Two phenotypes for 1-B-D-arabinofuranosylcytosine (ara-C) deamination corresponding to a ratio of distribution for "slow" (ratio, less than or equal to 14) vs "fast" (ratio, greater than 14) deaminators of 70%:30%, have been determined on the basis of studies on plasma ratios of 1-B-D-arabinofuranosyluracil/ara-C (ara-U/ara-C) in 56 subjects treated with high-dose ara-C (3 g/m2 infused i.v. over 3 h). A positive correlation of age with the concentration of ara-U was observed. In a subgroup of 36 patients with leukemia, the ara-U/ara-C pattern was similar to that observed for all 56 subjects. In these leukemic patients, who were treated with combinations of ara-C plus other conventional agents, a tendency toward a positive response (complete response + partial response) was found for those showing low ara-U/ara-C ratios (slow deaminators). The phenotypic effect of deamination in acute leukemia needs to be evaluated prospectively.

Relationship between tumor cell density and drug concentration and the cytotoxic effects of doxorubicin or vincristine: mechanism of inoculum effects

When tumor cell density increases, the cytotoxic activity of certain anticancer agents, such as vincristine (VCR) and doxorubicin (DXR), progressively decreases. This phenomenon is termed the inoculum effect. Since VCR and DXR are less active in an acidic environment, we questioned whether the inoculum effects could have resulted from acidification of the medium that may have developed due to the high cell density. However, measurements of the cytotoxic activity of these agents in a pH-controlled medium revealed only a minor correction of the inoculum effects. Second, we wondered whether the inoculum effects that occurred at the high cell density might have been attributable to insufficient amounts of drugs to bind all the binding sites of the cells. To test this hypothesis, we used drug-resistant sublines, which required higher VCR or DXR concentrations for cell killing than did the parent cell line. When higher drug concentrations were used, the dose-response curves generated for low- and high-density cell populations became closer and overlapped each other, resulting in virtual disappearance of the inoculum effects. Measurements of cellular drug levels revealed that at a high cell density, cells accumulated much smaller amounts of both VCR and DXR in parallel with the positive inoculum effect. In contrast, when high concentrations of the drugs were used in drug-resistant cells, differences in the cellular drug contents between low and high cell densities became narrow. Cisplatin (DDP) belongs to a group of drugs that do not produce inoculum effects, and DDP's cytotoxic effects were not influenced by the pH-controlled medium or by the use of drug-resistant cell lines. These observations indicate that the inoculum effects are the result of the unavailability of VCR or DXR molecules to all cellular binding sites when cells at high densities are exposed to drugs. The drug concentration relative to cell density was apparently the major determinant for the inoculum effects seen in VCR- or DXR-induced cell killing.

[Expression of glucocorticoid receptors and blast cell clearance in children with different variants of acute lymphoblastic leukemia]

Glucocorticoid receptor (GR) levels were estimated in blast cells of 24 children with acute lymphoblastic leukemia, in different immunocytologic subvariants of the disease. No relationship was revealed between immunophenotype and GR number in blasts. It was found that the response to prednisolone therapy did not depend on the number of sites specifically bound to glucocorticoids. The response character is determined not by immunophenotype but by the initial number of blast cells in the peripheral blood (the higher blastosis, the worse response). High blastosis is probably dependent on the tumor growth rate.

Relationship between urinary and serum growth hormone and pubertal status

Urinary growth hormone (uGH) excretion and serum growth hormone concentrations have been compared in three groups of children. Group 1 consisted of 21 children who had had cranial irradiation as part of their treatment for acute lymphoblastic leukaemia; group 2, 18 normal children; and group 3, 12 boys with constitutional delay in growth and puberty who were in early puberty. Children in groups 1 and 2 each had a 24 hour serum growth hormone profile (sampling every 20 minutes) and concurrent urine collection. The 12 boys in group 3 had a total of 21 profiles (sampling every 15 minutes for 12 hours) and concurrent urine collections. In the prepubertal children (n = 17), in both groups 1 and 2, there was a significant correlation between mean serum growth hormone and total uGHng/g creatinine. There were also significant correlations between total uGHng/g creatinine and both peak serum growth hormone and mean amplitude of the pulses in the growth hormone profile. In the pubertal children (n = 22), in groups 1 and 2, whether combined or in separate groups, there was no significant correlation between total uGHng/g creatinine and mean serum growth hormone, peak serum growth hormone, or mean amplitude of the pulses in the growth hormone profile. In group 3 there were significant correlations between total uGHng/g creatinine and both the mean serum growth hormone and mean amplitude of the pulses in the profile. Therefore uGH estimations appear to correlate well with serum growth hormone profiles in children who are prepubertal or in early puberty, but not in those further advanced in pubertal development. These results may reflect a variation in the renal handling of growth hormone during pubertal development. uGH estimation may be an unreliable screening investigation for growth hormone sufficiency in mid to late puberty.

Differences in teniposide disposition and pharmacodynamics in patients with newly diagnosed and relapsed acute lymphocytic leukemia

Teniposide, a widely used investigational anticancer drug, is extensively bound to plasma proteins (greater than 95%). The present study evaluated the clearance and pharmacodynamics of total and unbound teniposide in patients with acute lymphocytic leukemia who were either in first complete remission or who had relapsed and achieved a subsequent complete remission. When compared to values of patients in first remission, the mean total systemic clearance of teniposide in relapsed patients was significantly lower at the time remission reinduction therapy was initiated, but increased to values greater than first remission patients after a subsequent remission was achieved. However, the mean clearance of unbound teniposide (ml/min/m2) was 3-fold lower in relapsed patients during reinduction therapy (1224 vs. 4261, P less than .0001), and improved but remained low after these patients achieved a subsequent remission (1965, P = .025). Changes in plasma protein binding accounted for the increase in total clearance when unbound clearance decreased. Continuous therapy with L-asparaginase was the major treatment difference in those patients with hypoalbuminemia and lower clearance of unbound teniposide. In 15 evaluable patients in complete remission, there was a statistically significant (P = .039) linear correlation between the percentage decrease in white blood cell count and the systemic exposure (AUC) to unbound teniposide, with higher exposure associated with a greater decrease in white blood cell count. There was not a significant correlation between the percent decrease in white blood cell count and the dosage given or the systemic exposure to total teniposide.(ABSTRACT TRUNCATED AT 250 WORDS)

Cellular kinetics of prednimustine versus chlorambucil plus prednisolone in vitro

Intracellular concentrations of prednimustine (PM), chlorambucil (CLB), phenylacetic acid mustard (PAAM) and prednisolone (P) were measured in different experimental tumor cell lines that had been incubated with either PM or CLB + P. For intracellular analytical determination, we modified a high-pressure liquid chromatographic method for the detection of these substances in plasma. Intact PM could be detected in the intracellular compartment of the incubated tumor cells. PM-incubated cells from PM-injected rats exhibited a higher intracellular concentration-time integral (PAAM) and longer concentration-time profiles for drugs with alkylating capacity than did cells exposed to the CLB + P mixture or to CLB. PAAM was not detectable after incubation of cells with PM, whereas in CLB-incubated cells the AUC of PAAM exceeded that of the parent drug CLB. Our in vitro results therefore favour the concept of a facilitated intracellular uptake and an increased antiproliferative effect for PM versus CLB and CLB + P.

Enhancement of etoposide and methotrexate sensitivity by indomethacin in vitro

The possibility of increasing the activity of etoposide (VP-16) by combining this anti-cancer agent with indomethacin (Indo) was investigated by treating murine and human cultured tumor cells with a combination of Indo and VP-16 and quantitating VP-16 cytotoxicity by the [3H]thymidine incorporation assay. Non-toxic concentrations of Indo were found to enhance the sensitivity to VP-16 in cultured Lewis lung carcinoma (LLC), YAC-1, P815, CCRF-CEM and K562 cells which were all relatively sensitive to VP-16. With the LLC, the Indo effect was dose dependent and near maximal at an Indo concentration of 0.5 micrograms/ml. Indo also increased the response of LLC cells to methotrexate, but not to bleomycin. Ibuprofen was less effective than Indo in enhancing VP-16 sensitivity in LLC cells. The enhanced sensitivity of VP-16 by Indo was not reversed by the prostaglandins PGE2 and PGD2, the analogs carbocyclic thromboxane A2 and carba-prostacyclin or conditioned medium removed after 24 h or 48 h of culture from near confluent LLC cell monolayers. This finding suggests that Indo is not augmenting VP-16 cytotoxicity by inhibiting cyclo-oxygenase activity and prostaglandin production. The lipoxygenase inhibitor, eicosatetraynoic acid (ETYA), was also ineffective in reversing the Indo augmentation of VP-16 sensitivity. This finding indicates that Indo is not acting by inhibiting cyclo-oxygenase and converting larger amounts of arachidonic acid to lipoxygenase products, such as leukotrienes, that could then interact with VP-16 to increase its sensitivity. In other studies, Indo was found to significantly increase the steady state accumulation of [3H]-VP-16 in all five cell lines studied. With the LLC cells, this increased steady state was achieved within 15 min after the addition of Indo to these cells and this enhanced VP-16 uptake was not reversed by the addition of prostaglandin E2 or prostaglandin D2. Thus, taken together, these studies indicate that Indo most likely enhances the cytotoxicity of VP-16 by increasing the cellular accumulation of VP-16. This newly identified function of Indo may be of potential clinical significance in the treatment of cancers in man.

[Biochemical and cytochemical criteria for predicting the course of acute lymphoblastic leukemia in children]

Cytochemical parameters of intracellular metabolism of leukemia cells and bone marrow polyamines were studied in 113 acute lymphoblastic leukemia patients aged from 1 to 14 years. The parameters analyzed characterized the severity of the disease course, cytostatic therapy effectiveness and primary resistance. It is shown that determination of biochemical and cytochemical criteria before the beginning of acute lymphoblastic leukemia therapy may be conducive to the correct choice of treatment.

Protein kinase C plays a role in the induction of tyrosine phosphorylation of lymphoid microtubule-associated protein-2 kinase. Evidence for a CD3-associated cascade that includes pp56lck and that is defective in HPB-ALL

Ligation of the CD3 receptor induces multiple signal transduction events that modify the activation state of the T cell. We have compared two lines that express biologically active CD3 receptors but differ in their biochemical activation pathways during ligation of this receptor. Jurkat cells respond to anti-CD3 with Ca2+ mobilization, PKC activation, induction of protein tyrosine phosphorylation, and activation of newly characterized lymphoid microtubule associated protein-2 kinase (MAP-2K). MAP-2K itself is a 43-kDa phosphoprotein that requires tyrosine phosphorylation for activation. Although ligation of the CD3 receptor in HPB-ALL could stimulate tyrosine phosphorylation of a 59- kDa substrate, there was no associated induction of [Ca2+]i flux, PKC, or MAP-2K activation. A specific PKC agonist, PMA, which bypasses the CD3 receptor, could, however, activate MAP-2K in HPB-ALL cells. This implies that defective stimulation of PKC by the CD3 receptor is responsible for its failure to activate MAP-2K in HPB-ALL. The defect in PKC activation is likely distal to the CD3 receptor as A1F14- failed to activate MAP-2K in HPB-ALL but was effective in Jurkat cells. The stimulatory effect of PMA on MAP-2K activity in HPB-ALL was accompanied by tyrosine phosphorylation of this kinase which implies that PKC may, in some way, regulate tyrosine phosphorylation of MAP-2K. A candidate for this role is pp56lck which underwent posttranslational modification (seen as mobility change on SDS-PAGE) during anti-CD3 and PMA stimulation in Jurkat or PMA treatment in HPB-ALL. There was, in fact, exact coincidence between induction of PKC activity, posttranslational modification of lck and tyrosine phosphorylation/activation of MAP-2K. Lck kinase activity in an immune complex kinase assay was unchanged during PMA treatment. An alternative explanation is that modification of lck may alter its substrate profile. We therefore looked at the previously documented ability of PKC to dissociate lck from the CD4 receptor and found that PMA could reduce the stoichiometry of the lck interaction with CD4 in HPB-ALL and to a lesser extent in Jurkat cells. These results imply the existence of a kinase cascade that is initiated by PKC and, in the course of which, lck and MAP-2K may interact.

Changes of zinc values in children during malignant disease

In 47 children with malignancy, zinc status, growth, and performance during standard treatment were compared with those in controls. At diagnosis, growth was retarded and hair zinc values were high, 2.4 +/- 0.7 mumol/g, as in chronic deficiency. During induction therapy, serum declined to 10.4 +/- 2.3 mumol/L and urinary excretion increased to 5.3 +/- 2.8 mumol/mol creatinine, as in acute exacerbation of deficiency. Control CSF values in children in remission, 0.04 +/- 0.01 mumol/L, were lower than reference values in adults. No difference in mean CSF zinc was observed during therapy, or in those with acute lymphoblastic leukemia (1) at high risk, (2) with central nervous system involvement, (3) with low performance, or (4) resistant to therapy. In six children unexplained values, up to 0.28 mumol/L during induction, were measured. No correlations between the various zinc parameters were found.

Increased expression of laminin receptors during myeloid differentiation

Variation of laminin receptor levels (LNR) during myeloid-cell differentiation and in acute leukemia were investigated by 125I-laminin-binding determination during HL60 cell differentiation and in cells of patients with different types of leukemia, characterized according to the FAB classification. LNR levels in HL60 cells increased during differentiation, being significantly higher in cells exposed to phorbol myristate acetate (PMA) and ethanol (55,391 +/- 27,845 and 29,314 +/- 6,435 sites/cell respectively) as compared with HL60 controls (8,549 +/- 4,000 sites/cell). The control cells do not adhere to laminin-coated surfaces, but differentiation with PMA results in their rapid adherence on this substratum. Short treatment with PMA does not increase the number of adherent cells or the receptor expression. Granulocytes also presented equally high LNR concentration (29,739 +/- 13,516 sites/cell). The lymphoid cells (lymphocyte, acute lymphoid leukemia and chronic lymphocytic leukemia) shared low LNR numbers (less than 6,500 sites/cell). Myeloid cells displayed a wide range of LN receptors with higher levels being associated with the more differentiated FAB subgroups. 125I-laminin binding to lymphoid or myeloid leukemic cells was mainly inhibited by P1 fragments, whereas granulocytes and differentiated HL60 cells displayed a dual binding pattern for laminin fragments P1 and E8. These results were confirmed by assays using 125I-labelled P1 and E8 fragments. We conclude that magnitude of LNR levels and variation in expression of P1 and E8 receptors appear to be linked to lineage and maturation status in hematopoietic cells.

2,4-diamino-7-hydroxy-pteridines, a new class of catabolites of methotrexate

Methotrexate remains a commonly used drug in the chemotherapy of various malignancies. The known catabolites are 7-hydroxy-methotrexate, formed in the liver, and diamino-methyl-pteroic acid formed in the gut. We report for the first time evidence that 2,4-diamino-7-hydroxy-pteridine derivatives are present in the biological fluids of patients on high-dose methotrexate protocols. So far, two major derivatives have been identified as 2,4-diamino-6-hydroxymethyl-7-hydroxy-pteridine and 2,4-diamino-6-methyl-7-hydroxy-pteridine. In regard to the actual knowledge of the catabolism of pteridines, these compounds are presumably formed by intestinal bacteria during enterohepatic circulation of the drug. Their slow clearance from the body raises the question of possible interference of these compounds on pteridine-dependent enzymes, which might explain in part some of the toxic effects of methotrexate.

Age-related differences in hepatic drug clearance in children: studies with lorazepam and antipyrine

The disposition of intravenous antipyrine and lorazepam, administered as model substrates for hepatic oxidative metabolism and conjugation, was evaluated in 50 children (mean age, 7.8 years; range, 2.3 to 17.8 years) with acute lymphocytic leukemia in complete remission and compared with a group of ten healthy adults. Antipyrine clearance normalized to body weight was significantly greater in children than in adults (0.91 versus 0.59 ml/min/kg; p = 0.012), but was not different when normalized to body surface area. In contrast, lorazepam total clearance (CL) and unbound clearance (CLu) normalized to body weight were not significantly different between children and adults but were smaller in children when normalized to body surface area (CL = 31.9 versus 40.6 ml/min/m2, p = 0.036; CLu = 352 versus 485 ml/min/m2, p = 0.010). The mean lorazepam fraction unbound in children was 0.087, which was not different from adult volunteers (0.084). This study has identified significant differences between children and adults in the disposition of these two compounds, with higher milliliter per minute per kilogram clearance for antipyrine but not lorazepam.

Heterogeneous expression of the product of the retinoblastoma susceptibility gene in primary human leukemia cells

To investigate the possible role of the product of the retinoblastoma susceptibility gene, pRB, in leukemogenesis, we examined fresh leukemia cells from 56 cases of primary leukemia (AML, 32; ALL, 12; CML-BC, 9; CLL, 3) for expression of pRB by using an immunoblotting assay with anti-pRB monoclonal antibodies PMG 3-245 or 3-340. Expression of the 70 kDa heat shock protein (Hsp70) was examined simultaneously as an internal control. pRB was found to be absent or expressed at an abnormally low level in 13 of 56 cases. Abnormal expression of pRB was most common in AML (8/32) and CML-BC (4/9), and less common in ALL (1/12). Expression of pRB was not induced in two cases of pRB- AML cultured for 24 h with GM-CSF, indicating that pRB expression could not be induced by increasing the rate of proliferation. The eight cases of AML lacking pRB protein were examined for RB1 mRNA by Northern blot. Two lacked RB1 mRNA and six had a normal-sized mRNA (approximately 4.7 kb), although the amount of RB mRNA was very low in some cases. RB1 gene structure was normal by Southern blot in all eight cases lacking pRB protein which were studied. These results show that lack of pRB expression is relatively common in human myeloid leukemias, and suggests that loss of pRB expression could contribute to the altered growth control of these cells.

P-glycoprotein expression and in vitro reversion of doxorubicin resistance by verapamil in clinical specimens from acute leukaemia and myeloma

The expression of the P-glycoprotein which is associated with the development of multidrug resistance in various cell lines was investigated in 87 fresh acute leukaemia and multiple myeloma samples using the specific mouse monoclonal antibody MRK16 in an indirect immunofluorescence assay. Considering a 10% positive cell cut-off value, a heterogeneous expression of P-glycoprotein was observed in 5/22 (22.7%) de novo acute leukaemias, 7/22 (31.8%) relapse or secondary acute leukaemias, 14/27 (51.8%) acute transformation of myeloproliferative or myelodysplastic syndromes and 5/16 (31.2%) multiple myelomas. This expression was not associated with specific cytogenetic abnormalities, especially alterations of chromosome 7q. Verapamil, a calcium channel blocker, has been demonstrated to circumvent the multidrug resistance in cell lines, possibly by interfering with P-glycoprotein function. Using the microculture tetrazolium assay, verapamil was demonstrated to increase the sensitivity of fresh leukaemic or myeloma cells to doxorubicin in 19/43 (43.1%) samples. The doxorubicin IC50 level and the capacity of verapamil to increase the sensitivity of blast cells to doxorubicin in vitro did not correlate with the expression of P-glycoprotein. We conclude that high non-cytotoxic concentrations of verapamil were able to increase the in vitro doxorubicin sensitivity of fresh acute leukaemia and myeloma cells without detectable expression of the P-glycoprotein.