A phase II trial testing interventions to shorten time to diagnosis and reduce abandonment of treatment of children with Burkitt lymphoma in Kenya

10032

Background: Burkitt Lymphoma (BL) is a common pediatric cancer in sub-Saharan Africa. Despite advances in care, prognosis is poor. The BL treatment protocol at our center in Kenya used since 2010, had a one-year survival of 29% (Martijn et al. BMJ Paed Open 2017). We hypothesized that financial burdens and delays in start of therapy impact outcomes. Methods: Our trial tested interventions aimed to: 1) Shorten time from presentation to start of treatment to improve survival; and 2) Support families during therapy to reduce abandonment. Initial eligibility included clinical suspicion of BL in a child 0-13 years of age. Patients with confirmed diagnosis of a mature B-cell lymphoma received support to complete therapy. Children with prior treatment of cancer were excluded. The trial was approved by human protection boards in Kenya and Indiana and consent was obtained prior to study entry. We enrolled 96 children with possible BL. Study personnel expedited routing of tissue samples to laboratories. Touch preps or smears were stained with Giemsa and reviewed by pathologists. Fresh tissue from all sources was used for flow cytometry. Tissue from core needle or incisional biopsies was processed for routine and immunohistochemical staining. Of 96 patients, 43 had BL confirmed by pathologic studies and were treated with combination chemotherapy given over 25 weeks. We paid families for transport costs for care, called after missed appointments, and provided direct monetary support (~$200 USD) for the 200 days children were on treatment. Results: Facilitating the biopsy shortened, by 3 days, the median time from admission to initiation of therapy for BL, because families did not need to raise funds for testing. Monetary support reduced abandonment of treatment by patients. Only 2 of 43 (5%) patients abandoned therapy, compared to abandonment by 22 of a cohort of 63 (35%) patients treated previously (p < 0.001). The combination of rapid diagnosis, early therapy, and financial support and communication with families improved event free survival of children with BL to 50% at 1 year (p = 0.045). Conclusions: Simple interventions to improve efficiency of diagnosis and reduce abandonment leads to improved outcomes for children with BL in Kenya.

Application of the steep ramp test for aerobic fitness testing in children with cancer

BACKGROUND

Children with and after cancer are found to have a decreased physical fitness, frequently resulting in decreased physical functioning. The gold standard test for assessing aerobic fitness, a component of physical fitness, is the respiratory gas analyses-based cardiopulmonary exercise test (CPET). However, equipment for gas analysis is often unavailable in local physical therapy centres and non-university hospitals. The steep ramp test (SRT), is a cycle ergometer test with a fast increase in workload, a short duration, and does not require respiratory gas analysis equipment.

AIM

The aim of this study was to compare the results of the CPET and the SRT, in children with cancer, and to assess whether the SRT can be used for aerobic fitness assessment in clinical practice in this population.

DESIGN

This study is a cross-sectional assessment using baseline data of a randomized controlled trial.

SETTING

The study was performed in a hospital setting.

POPULATION

Sixty-one children (mean age 12.9 years; 33 boys) with cancer were included in the analysis; 16 children were on non-intensive chemotherapy treatment, 45 were in the first year thereafter.

METHODS

Participants performed both the SRT and the CPET on a cycle ergometer with respiratory gas analysis. Data of the two tests were compared and regression analyses were performed.

RESULTS

CPET test results revealed a higher impact on the cardiovascular system, as shown by higher peak ventilation (47.8 versus 52.0 Litres per min) and peak heart rates (173 versus 191 beats per min), compared to the SRT. In addition, the test time was significantly longer (90 s versus 390 s). Yet, the primary outcome of the SRT (peak work rate) was able to reliably estimate the peak oxygen uptake of the CPET.

CONCLUSION

The peak oxygen uptake was comparable between the SRT and the CPET, although the peak work rate was significantly higher during the SRT. This study showed that the SRT is a valid instrument to assess aerobic fitness in children with cancer.

CLINICAL REHABILITATION IMPACT

The SRT is less time consuming and can be performed without gas analysis in a non-clinical setting, making it less demanding for children.

Methylation specific PCR to characterize methylation of the promoter of deoxycytidine kinase

Deoxycytidine kinase (dCK) is essential for phosphorylation of natural deoxynucleosides and analogs, such as gemcitabine and cytarabine, two widely used anticancer compounds. We hypothesized that DNA methylation of SP1 binding sites in the dCK promoter region might affect dCK expression. Using methylation specific PCR (MSP), methylation was detected in one of the SP1 binding sites of the dCK promoter, in most tested cancer cell lines and in patient samples from brain tumors and leukemia. This SP1 site is a 3'GC box, which upon hypomethylation negatively regulates dCK mRNA expression. In conclusion, we developed a new MSP method showing methylation of the 3' GC-box in the dCK promoter region in tumor cells and patient samples. Methylation might therefore regulate transcription of dCK, and should be studied further to understand its role in influencing gemcitabine and cytarabine activity.

Comparison of ovarian function markers in users of hormonal contraceptives during the hormone-free interval and subsequent natural early follicular phases

OBJECTIVE

The aim of this study was to evaluate whether values of FSH, LH, estradiol, anti-Müllerian hormone (AMH), inhibin B, antral follicle count (AFC) and ovarian volume (OV) determined on day 7 of the hormone-free interval are similar to values measured on days 2-5 of two subsequent natural menstrual cycles. In addition, values measured on day 7 of the hormone-free interval were examined for the purpose of predicting values measured on days 2-5 during the second natural cycle.

METHODS

In this study, 25 women using hormonal contraception provided a blood sample and underwent transvaginal ultrasound measurements on day 7 of the hormone-free interval and on cycle days 2-5 of two subsequent natural cycles. Changes were compared by repeated measures ANOVA and multivariate linear regression was used for prediction purposes.

RESULTS

Mean (SD) age of the participants was 26.3 (6.2) years. Overall significant decreases in FSH and inhibin B and significant increases in AMH, AFC and ovarian volume values were measured after discontinuation of hormonal contraception (P < 0.001, P = 0.04, P = 0.01, P < 0.001 and P = 0.004, respectively). Significant changes occurred both from day 7 of the hormone-free interval to natural cycle 1 as well as from natural cycle 1 to natural cycle 2. FSH, AMH and AFC values measured during days 2-5 of natural cycle 2 could be predicted by the corresponding values measured on day 7 of the hormone-free interval.

CONCLUSION

Hormonal and ultrasound markers of ovarian function in hormonal contraception users measured at the end of the hormone-free interval do not seem to represent subsequent natural early follicular phase values. However, these values can, in some cases (FSH, AMH and AFC), be used to predict early follicular phase values using calculated prediction equations, which need to be validated in future research.

Expression of deoxycytidine kinase in leukaemic cells compared with solid tumour cell lines, liver metastases and normal liver

Deoxycytidine kinase (dCK) is required for the phosphorylation of several deoxyribonucleoside analogues that are widely employed as chemotherapeutic agents. Examples include cytosine arabinoside (Ara-C) and 2-chlorodeoxyadenosine (CdA) in the treatment of acute myeloid leukaemia (AML) and gemcitabine to treat solid tumours. In this study, expression of dCK mRNA was measured by a competitive template reverse transcriptase polymerase chain reaction (CT RT-PCR) in seven cell lines of different histological origin, 16 childhood and adult AML samples, 10 human liver samples and 11 human liver metastases of colorectal cancer origin. The enzyme activity and protein expression levels of dCK in the cell lines were closely related to the mRNA expression levels (r=0.75, P=0.026 and r=0.86, P=0.007). In AML samples, dCK mRNA expression ranged from 1.16 to 35.25 (x10(-3)xdCK/beta-actin). In the cell line panel, the range was 2.97-56.9 (x10(-3)xdCK/beta-actin) of dCK mRNA expression. The enzyme activity in liver metastases was correlated to dCK mRNA expression (r=0.497, P=0.05). In the liver samples, these were not correlated. dCK mRNA expression showed only a 36-fold range in liver while a 150-fold range was observed in the liver metastases. In addition, dCK activity and mean mRNA levels were 2.5-fold higher in the metastases than in the liver samples. Since dCK is associated with the sensitivity to deoxynucleoside analogues and because of the good correlation between the different dCK measurements in malignant cells and tumours, the CT-RT PCR assay will be useful in the selection of patients that can be treated with deoxycytidine analogues.

Post-induction residual leukemia in childhood acute lymphoblastic leukemia quantified by PCR correlates with in vitro prednisolone resistance

Most prognostic factors in childhood acute lymphoblastic leukemia (ALL) are informative for groups of patients, whereas new approaches are needed to predict the efficacy of chemotherapy for the individual patient. The residual leukemia following 4 weeks of induction therapy with prednisolone, vincristine, doxorubicin and i.t. methotrexate and the in vitro resistance to prednisolone, vincristine, and doxorubicin were measured in 30 boys and 12 girls with B (n = 34) or T lineage (n = 8) ALL. The residual leukemia was quantified after 2 (MRD-D15, n = 29) and 4 weeks (MRD-PI, n = 42) of induction therapy with a precise and reproducible clone-specific PCR technique. The median MRD-D15 and MRD-PI were 0.50% (75% range 0.0088.1%) and 0.014% (75% range 0.001-2.0%), respectively, and these levels correlated significantly (n = 29, rs = 0.75, P < 0.001). Both the MRD-D15 and the MRD-PI were related to the age of the patient (MRD-D15: rs= 0.48, P= 0.009; MRD-PI: rs = 0.45, P = 0.003). Patients with T lineage ALL had higher MRD-PI than those with B lineage ALL (median MRD-PI: 0.5% vs 0.01%, P = 0.05). The median LC50 (concentration lethal to 50% of cells) for prednisolone was 2.3 microg/ml (75% range 0.05-668). Both MRD-D15 and MRD-PI correlated significantly with the in vitro resistance to prednisolone (MRD-D15: rs = 0.41, P = 0.03; MRD-PI: rs = 0.39, P = 0.01); but not to in vitro vincristine or doxorubicin resistance. The correlations between MRD and in vitro prednisolone resistance were even more pronounced when B cell precursor and T cell leukemia were analyzed separately (B cell precursor ALL: MRD-PI vs prednisolone LC50: n = 33, rs = 0.47, P = 0.006; T cell ALL: MRD-PI vs prednisolone resistance: n = 8, rs = 0.84, P = 0.009). After a median follow-up of 5.0 years (75% range 3.2-6.9) eight patients have relapsed. All of the 21 patients with a MRD-PI < or =0.5% and a prednisolone LC50 < or =10 microg/ml have remained in remission whereas the 7 year event-free survival for the remaining 20 patients was 0.45 +/- 0.16 (P= 0.002) Prospective studies in childhood ALL are needed to clarify whether combined monitoring of in vitro drug resistance and residual leukemia early during chemotherapy could offer new ways to classify patients and stratify the intensity of therapy.

A possible role for methotrexate in the treatment of childhood acute myeloid leukaemia, in particular for acute monocytic leukaemia

Acute myeloid leukaemia (AML) is thought to be methotrexate (MTX)-resistant. However, a small study suggested that acute monocytic leukemia (AML-M5) is sensitive to MTX. We measured MTX accumulation/polyglutamylation in 20 AML-nonM5, 37 AML-M5 and 83 common/preB-acute lymphoblastic leukaemia (c/preB-ALL) samples. Membrane transport was determined in 11 childhood AMLs (including 3 AML-M5) and in 25 c/preB-ALL samples. MTX sensitivity was determined in 23 AML-nonM5, 15 AML-M5 and 63 common/preB-ALL samples using the thymidylate synthase (TS) inhibition assay. MTX transport was higher in AML samples compared with c/preB-ALL precluding a transport defect in AML. Accumulation of long-chain polyglutamates MTX-Glu(4-6) was 3-fold lower for AML-nonM5 compared with c/preB-ALL cells (median 268 versus 889 pmol MTX-Glu(4-6)/10(9) cells; P < or = 0.001); for AML-M5 samples, median accumulation of MTX-Glu(4-6) was 0 pmol/10(9) cells (P < or = 0.001). After short-term MTX exposure, AML-nonM5 was 6-fold more resistant to MTX compared with c/preB-ALL cells (2.16 versus 0.39 microM; P < 0.001), while AML-M5 was 2-fold more resistant (P = 0.02). In both AML-nonM5 and AML-M5 cells, MTX resistance was circumvented by continuous MTX exposure (median TSI(50) values: 0.052 and 0.041 microM, respectively) compared with a c/preB-ALL value of 0.066 microM. In conclusion, AML-M5 is relatively sensitive to MTX compared with other AML-subtypes even though polyglutamylation of MTX is poor. Using continuous exposure, AML-nonM5 and AML-M5 cells were at least as sensitive to MTX as c/preB-ALL cells. This report suggests that MTX might be an overlooked drug in the treatment of childhood AML.

Cellular drug resistance profiles in childhood acute myeloid leukemia: differences between FAB types and comparison with acute lymphoblastic leukemia

Determining in vitro drug resistance may reveal clinically relevant information in childhood leukemia. Using the methyl-thiazol-tetrazolium assay, the resistance of untreated leukemic cells to 21 drugs was compared in 128 children with acute myeloid leukemia (AML) and 536 children with acute lymphoblastic leukemia (ALL). The differences between 3 French-American-British (FAB) types (M1/M2, M4, and M5) were also compared. AML was significantly more resistant than ALL to the following drugs, as noted by the median resistance: glucocorticoids (greater than 85-fold), vincristine (4.4-fold), L-asparaginase (6.9-fold), anthracyclines (1.8- to 3.4-fold), mitoxantrone (2.6-fold), etoposide (4.9-fold), platinum analogues (2.4- to 3.4-fold), ifosfamide (3.5-fold), and thiotepa (3.9-fold). For cytarabine and thiopurines, the median LC50 values (the drug concentration that kills 5% of the cells) were equal. Also, busulfan, amsacrine, teniposide, and vindesine showed no significant differences, but the numbers were smaller, and the median LC50 values were 1.3- to 5.2-fold higher in AML. None of the drugs demonstrated greater cytotoxicity in AML. FAB M5 was significantly more sensitive than FAB M4 to most drugs frequently used in AML, as indicated by the following ratios of median sensitivities: the anthracyclines (2.6- to 3.2-fold), mitoxantrone (12.5-fold), etoposide (8.7-fold), and cytarabine (2.9-fold). For etoposide and cytarabine (5.4- and 3.4-fold, respectively) FAB M5 was also significantly more sensitive than FAB M1/M2. FAB M5 was equally sensitive to L-asparaginase and vincristine as ALL. Only 15% of the AML samples were "intermediately" sensitive to glucocorticoids, mainly in FAB M1/M2. The poorer prognosis of childhood AML is related to resistance to a large number of drugs. Within AML, FAB M5 had a distinct resistance pattern. These resistance profiles may be helpful in the rational design of further treatment protocols. (Blood. 2000;96:2879-2886)

Asparagine synthetase activity in paediatric acute leukaemias: AML-M5 subtype shows lowest activity

Lack of sufficient cellular activity of asparagine synthetase (AS) in blast cells compared with normal tissue is thought to be the basis of the antileukaemic effect of L-asparaginase in acute lymphoblastic leukaemia (ALL). Although L-asparaginase is routinely used in ALL, its role and value in the treatment of acute myelogenous leukaemia (AML) is still being discussed. To evaluate the pharmacological basis for L-asparaginase treatment, we established pretreatment monitoring of the intracellular AS activity in blast cells of patients with AML and ALL. There was no general difference in AS activity between ALL and AML samples. Significantly lower AS activity, however, was found in the B-lineage ALL subgroups as well as AML-M5.

Bcl-2 family members in childhood acute lymphoblastic leukemia: relationships with features at presentation, in vitro and in vivo drug response and long-term clinical outcome

We have found that, in addition to Bcl-2 and Bax, the expression levels of apoptosis inducers (Bad, Bak) and inhibitors (Bcl-xL, Mcl-1) were highly variable in blasts from 78 children with newly diagnosed acute lymphoblastic leukemia (ALL). The patients were enrolled in the national study ALL-7 of the Dutch Childhood Leukemia Study Group. In contrast to Bcl-2 that inversely correlated with %S-phase cells and WBC, and was lower in T than in B-lineage ALL, the Bcl-2 family members were not found to be associated with features at presentation. These expression levels were also compared with drug resistance in in vitro MTT (methyl-thiazol-tetrazolium) assays for prednisolone, vincristine and asparaginase in 46 children. Protein expression levels of the Bcl-2 family were not found to correlate with in vitroresistance to the individual drugs or the combined drug resistance profile. In addition, neither peripheral blast reduction after 1 week of prednisone monotherapy nor long-term disease-free interval or survival showed a correlation with protein expression. Our results indicate that the anti-proliferative function of Bcl-2 dominates its anti-apoptotic function in ALL, but neither Bcl-2 nor the Bcl-2 family members gained prognostic information in the risk-adapted protocol ALL-7.

Cellular drug resistance in childhood acute myeloid leukemia. A mini-review with emphasis on cell culture assays

Cellular drug resistance is an important limiting factor in the success of chemotherapy in childhood acute myeloid leukemia (AML). We summarize the results of the studies published sofar that have focussed on drug resistance in childhood AML, using cell culture assays. We also briefly report our own results of an ongoing study. Finally, potential applications of cellular drug resistance testing are discussed. It appears that cellular drug resistance differs between AML and acute lymphoblastic leukemia and between subgroups of AML patients, that AML cells of relapsed patients are more resistance to cytarabine than those of untreated patients, and that in vitro resistance to cytarabine and daunorubicin is related to a worse prognosis. However, more and larger studies are required to determine the exact role of cellular drug resistance testing in the treatment of childhood AML.

BCL-2 expression in childhood leukemia versus spontaneous apoptosis, drug induced apoptosis, and in vitro drug resistance

The antileukemic activity of cytotoxic drugs is increasingly thought to be the result of induction of apoptosis. Several proto-oncogenes have been related to the regulation of this process. In this study we evaluated the relation between bcl-2 expression, spontaneous and dexamethasone (DXM) induced apoptosis, and in vitro resistance to DXM, prednisolone (PRD) and cytarabine (ARA) determined using the total cell kill colorimetric methyl-thiazol-tetrazolium salt (MTT) assay, in childhood acute lymphoblastic leukemia (ALL). Drug resistance was expressed as the LC50 value, the drug concentration lethal to 50% of the cells. Fourty-six samples taken at initial diagnosis (iALL) and 31 samples taken at relapse (rALL) were incubated in culture medium, with and without DXM. Bcl-2 expression and apoptosis were measured flowcytometrically, the latter using DNA histogram analysis. Bcl-2 expression was 1.4 fold higher in rALL than in iALL (p = 0.008). Both spontaneous and DXM induced apoptosis increased significantly from 0 to 48 hours (in up to 71%, 81% of the cells respectively). Bcl-2 expression was inversely correlated with the extent of spontaneous apoptosis after 24 hours in iALL (r = -0.40, p = 0.05). Relapsed samples, but not samples obtained at presentation, expressing high levels of bcl-2 displayed increased resistance to drug induced apoptosis (r = -0.63, p = 0.02). In iALL high bcl-2 expression appeared to be related to low LC50 values of ARA. No correlations were found for DXM or PRD. In conclusion, DXM excerts its cytotoxic effect at least partly by means of induction of apoptosis. Bcl-2 inhibits drug induced apoptosis in rALL. However in iALL bcl-2 expression is not associated with increased in vitro drug resistance, nor with increased resistance to drug induced apoptosis.

Lack of cross-resistance between prednisolone and methotrexate in childhood acute lymphoblastic leukemia? A preliminary analysis

We studied the cross-resistance between prednisolone (PRD) and methotrexate (MTX) in children with newly diagnosed acute lymphoblastic leukemia (ALL). This was done because of a previous observation that such patients could show a good clinical response to systemic PRD monotherapy plus intrathecal MTX, despite in vitro PRD resistant ALL cells (as determined with the MTT assay). This suggests an antileukemic effect of MTX, and thus the lack of cross-resistance between PRD and MTX. A systemic antileukemic effect of intrathecally administered MTX has been reported in the literature. Clinical good responders with PRD resistant ALL cells (n = 15) did not show unfavorable MTX-polyglutamylation nor unfavorable low inhibition of thymidylate synthase by MTX, as compared to a heterogeneous group of newly diagnosed ALL children (n = 47). In addition, we did not find a significant correlation between these two parameters and in vitro PRD resistance within the clinical good responders with PRD resistant ALL cells. In conclusion, we did not find a significant cross-resistance between PRD and MTX in vitro. It therefore may be that the good clinical response to systemic PRD plus intrathecal MTX in patients with in vitro PRD resistant ALL cells was caused by a systemic antileukemic activity of the intrathecally administered MTX.

Cellular drug resistance in acute myeloid leukemia: literature review and preliminary analysis of an ongoing collaborative study

Cellular drug resistance is one of the main causes of the frequent ultimate failure of chemotherapy in childhood acute myeloid leukemia (AML). We here summarize the results of a literature review on in vitro drug resistance in childhood AML, focusing on studies using so-called cell culture assays. We also briefly describe some results of an ongoing collaborative study between the Research Laboratory of Pediatric Oncology in Amsterdam (University Hospital Vrije Universiteit) and the German BFM-AML Group. In general, the literature and our preliminary data on in vitro cellular drug resistance in AML are promising in terms of clinical relevance. Cell biological features and clinical response to chemotherapy are related to in vitro drug resistance. However, a large study including multivariate analysis is required to more firmly establish the clinical value of cellular drug resistance testing in childhood AML, and the collaborative study will therefore be continued. Possible applications of cell culture assays include risk-group stratification, rational improvements of current treatment protocols for subgroups of patients based on specific drug resistance profiles, individualised tailored therapy, the study of cross-resistance patterns between drugs, the study of possibilities to modulate or circumvent drug resistance, the study of drug interactions, selection of patients for clinical phase II studies and drug screening.

Effects of interleukin 3, interleukin 7, and B-cell growth factor on proliferation and drug resistance in vitro in childhood acute lymphoblastic leukemia

Growth factors have been reported to enhance the cytotoxicity of anticancer agents. In our study we investigated the capacities of interleukin 3 (IL-3), interleukin 7 (IL-7), low-molecular-weight B-cell growth factor (lmw-BCGF), and IL-3 + 7 to induce proliferation and to modulate the drug resistance of childhood acute lymphoblastic leukemia (ALL) cells. Proliferation was assessed with the methyl-thiazole-tetrazolium (MTT) assay and other parameters. Cellular resistance to cytarabine, thioguanine, and prednisolone was measured using the MTT assay. In 19 samples containing >90% leukemic cells the proliferative response and the modulation of drug resistance was markedly heterogeneous between patient samples and between growth factors. All growth factors were able to stimulate proliferation significantly after 5 days of culture. lmw-BCGF was the most potent growth factor in this respect. Cytotoxicity of cytarabine and thioguanine was significantly increased by IL-7, that of thioguanine by IL-3 as well. IL-7 enhanced the cytotoxicity of thioguanine significantly more than IL-3 and lmw-BCGF and that of cytarabine more than IL-3. Cytotoxicity of prednisolone was not significantly influenced by any growth factor. In individual cases, growth factors reduced the cytotoxicity of the drugs. IL-3 + 7 did not add activity to the most potent single growth factor in both proliferation and drug resistance measurements. This study shows that IL-3, IL-7, and lmw-BCGF generally induce and occasionally inhibit proliferation of ALL cells. Furthermore, they may either increase or decrease cytotoxicity of anticancer drugs. This heterogeneous response to growth factors concerning induction of proliferation and modulation of drug resistance should be taken into account in their clinical use.

Different expression of glutathione S-transferase alpha, mu and pi in childhood acute lymphoblastic and myeloid leukaemia

Expression of three major classes of glutathione S-transferases (GSTs), i.e. alpha, mu and pi class, P-glycoprotein (P-gp) and multidrug resistance-associated protein (MRP) were studied in childhood acute lymphoblastic leukaemia (ALL), acute myeloid leukaemia (AML) and normal peripheral blood lymphocytes by flow cytometry. In vitro cytotoxicity of 4-hydroxy-ifosfamide (IFOS), daunorubicin (DNR) and prednisolone (PRED) was assessed by the MTT assay. Expression of alpha, mu and pi class GST did not significantly differ between leukaemic cells from 100 initial and 14 unrelated relapse ALL patients (GSTalpha P=026; GSTmu P=O009; GSTpi P=0.13). The expression of GSTalpha (1.4-fold, P=0.0004), GSTpi (13-fold, P = 0001) and to a lesser extent also GSTmu (1.1-fold, P=0.03) was higher in ALL compared with normal peripheral blood lymphocytes. Expression of GSTmu and GST7pi was significantly higher in 18 AML compared with 100 ALL patients at initial diagnosis (respectively 1.3-fold, P=0.0005 and 2-fold, P<0.0001). In contrast, GSTalpha was median 2-fold lower expressed in the AML samples (P< 0.0001). Expression levels of alpha, mu and pi class GSTs were not related to the degree of resistance to IFOS, DNR and PRED nor to immunophenotype, white blood cell count or age at presentation of childhood ALL. One exception was a remarkably low expression of GSTalpha in IFOS-sensitive samples compared with a heterogenous expression in IFOS-resistant samples (P= 0.02). Expression of GSTpi, but not of GSTalpha or GSTmu, weakly correlated with the expression of MRP (Rs 0.36, P = 0.002, n = 74) but not with P-gp. However, a high expression of both GSTpi and MRP was not associated with in vitro resistance to IFOS, DNR or PRED. The present data suggest that expression of GSTs is not linked to the degree of resistance to IFOS, DNR and PRED or clinical risk factors in childhood ALL. Whether the high expression of GSTmu and GSTpi in AML cells contributes to the relative resistance to IFOS, DNR and PRED compared with ALL samples (P < or = 0.0001) warrants further study.

Relation between age, immunophenotype and in vitro drug resistance in 395 children with acute lymphoblastic leukemia--implications for treatment of infants

The prognosis of infant ALL, characterized by a high incidence of the immature CD10 negative B-lineage ALL (proB ALL) is poor. This study aimed to determine the resistance profile of infant ALL cells. In vitro drug resistance was determined by the MTT assay of 395 children with ALL at initial diagnosis: there were 21 infants <1.5 years of which nine <1 year, 284 children aged 1.5-10 years (intermediate age group) and 90 children >10 years. Immunophenotyping resulted in 310 cALL/preB ALL, 69 T-ALL, 15 proB ALL and one unknown cases. The following drugs were tested: daunorubicin, doxorubicin, mitoxantrone, idarubicin (Ida), prednisolone (Pred), dexamethasone (DXM), vincristine (VCR), Asparaginase (Asp), 6-MP, 6-TG, AraC, VM26 and 4-HOO-ifosfamide (Ifos). Infants <1.5 years were significantly more resistant to Pred (>500-fold), Asp (11-fold) and VM26 (2.7-fold) but significantly more sensitive to Ara-C (2.3-fold) compared to the intermediate age group. When analyzing infants <1 year of age similar results were found. ProB ALL cells (seven infants <1.5 years; eight children >1.5 years) were significantly more resistant to glucocorticoids, Asp, thiopurines, anthracyclines and Ifos compared to cALL/preB ALL but more sensitive to Ara-C. Cells from children >10 years were significantly more resistant to Pred, DXM, Asp, Ida and 6-MP. T-ALL cells showed a strong resistance to Pred, Asp and VCR and a mild but significant resistance to all other drugs except thiopurines and VM26. We conclude that the poor prognosis of infant ALL is associated with a resistance to glucocorticoids and Asp. However, ALL cells from infants show a relatively high sensitivity to Ara-C which suggests that infants with ALL might benefit from treatment schedules that incorporate more Ara-C than the current treatment protocols.

Prednisolone resistance in childhood acute lymphoblastic leukemia: vitro-vivo correlations and cross-resistance to other drugs

As an important determinant of response to chemotherapy, accurate measurement of cellular drug resistance may provide clinically relevant information. Our objectives in this study were to determine the relationship between in vitro resistance to prednisolone (PRD) measured with the colorimetric methyl-thiazol-tetrazolium (MTT) assay, and (1) short-term clinical response to systemic PRD monotherapy, (2) long-term clinical outcome after combination chemotherapy within all patients and within the subgroups of clinical good and poor responders to PRD, and (3) in vitro resistance to 12 other drugs in 166 children with newly diagnosed acute lymphoblastic leukemia (ALL). The 12 clinical poor PRD responders had ALL cells that were median 88-fold more in vitro resistant to PRD than 131 good responders (P = .013). Within all patients, increased in vitro resistance to PRD predicted a significantly worse long-term clinical outcome, at analyses with and without stratification for clinical PRD response, and at multivariate analysis (P </= .001). Within both the clinical good and poor responder subgroups, increased in vitro resistance to PRD was associated with a worse outcome, which was significant within the group of clinical good responders (P < .001). LC50 values, ie, lethal concentrations to 50% of ALL cells, for PRD and each other drug correlated significantly with those of all other 12 drugs, with an average correlation coefficient of 0.44 (standard deviation 0.05). The highest correlations were found between structurally related drugs. In conclusion, in vitro resistance to PRD was significantly related to the short-term and long-term clinical response to chemotherapy, the latter also within the subgroup of clinical good responders to PRD. There was a more general in vitro cross-resistance between anticancer drugs in childhood ALL, although drug-specific activities were recognized.

Relationship between major vault protein/lung resistance protein, multidrug resistance-associated protein, P-glycoprotein expression, and drug resistance in childhood leukemia

Cellular drug resistance is related to a poor prognosis in childhood leukemia, but little is known about the underlying mechanisms. We studied the expression of P-glycoprotein (P-gp), multidrug resistance (MDR)-associated protein (MRP), and major vault protein/lung resistance protein (LRP) in 141 children with acute lymphoblastic leukemia (ALL) and 27 with acute myeloid leukemia (AML) by flow cytometry. The expression was compared between different types of leukemia and was studied in relation with clinical risk indicators and in vitro cytotoxicity of the MDR-related drugs daunorubicin (DNR), vincristine (VCR), and etoposide (VP16) and the non-MDR-related drugs prednisolone (PRD) and L-asparaginase (ASP). In ALL, P-gp, MRP, and LRP expression did not differ between 112 initial and 29 unrelated relapse samples nor between paired initial and relapse samples from 9 patients. In multiple relapse samples, LRP expression was 1.6-fold higher compared with both initial (P = .026) and first relapse samples (P = .050), which was not observed for P-gp and MRP. LRP expression was weakly but significantly related to in vitro resistance to DNR (Spearman's rank correlation coefficient 0.25, P = .016) but not to VCR, VP16, PRD, and ASP. No significant correlations were found between P-gp or MRP expression and in vitro drug resistance. Samples with a marked expression of two or three resistance proteins did not show increased resistance to the tested drugs compared with the remaining samples. The expression of P-gp, MRP, and LRP was not higher in initial ALL patients with prognostically unfavorable immunophenotype, white blood cell count, or age. The expression of P-gp and MRP in 20 initial AML samples did not differ or was even lower compared with 112 initial ALL samples. However, LRP expression was twofold higher in the AML samples (P < .001), which are more resistant to a variety of drugs compared with ALL samples. In conclusion, P-gp and MRP are unlikely to be involved in drug resistance in childhood leukemia. LRP might contribute to drug resistance but only in specific subsets of children with leukemia.

[Gentamicin administration in newborns: once daily]

OBJECTIVE

To determine the serum levels of gentamicin in newborn on one or two daily doses.

DESIGN

Retrospective and subsequently prospective, descriptive.

SETTING

Department of Pediatrics of the Deventer Hospital, the Netherlands.

METHOD

Gentamicin trough and peak plasma levels were analysed retrospectively in 30 neonates to whom gentamicin 3-4 mg/kg/day in two doses had been administered in 1995. In a subsequent prospective study in 1996, 52 neonates received gentamicin 4 mg/kg/day in one dose. Optimal levels were defined as a trough of < 2 mg/l and a peak of 6-12 mg/l. Levels were determined using a immunoassay.

RESULTS

Both groups were similar in gestational age, weight and age at the start of treatment. Both trough and peak plasma levels were not known in all patients. Adequate gentamicin trough levels were seen more often in the 'once daily' group than in the 'twice daily' group, in both the premature (12/14 = 86% versus 3/7 = 43%; p = 0.04) and non-premature (36/37 = 97% versus 18/23 = 78%; p = 0.017) neonates. Peak levels were higher in the 'once daily' group than in the 'twice daily' group, in both the prematures (11/13 = 85% versus 1/7 = 14%; p = 0.002) and non-prematures (25/28 = 89% versus 2/22 = 9%; p < 0.000001). Optimal trough and peak levels were found in 9/13 (69%) of the premature and 24/27 (89%) of the non-premature neonates treated according to the 'once daily' schedule, compared with 0 and 1/22 (5%) respectively in the neonates treated according to the 'twice daily' regimen (p = 0.003 and p < 0.0001, respectively).

CONCLUSION

In view of the reported levels and the literature, an initial dose of gentamicin of 4.0 mg/kg/day once a day is advised for neonates.

In vitro cellular drug resistance and prognosis in newly diagnosed childhood acute lymphoblastic leukemia

As an important determinant of the response to chemotherapy, measurements of cellular drug resistance may provide prognostically significant information, which could be useful for optimal risk-group stratification. The objective of this report is to determine the relation between in vitro resistance to 12 drugs, measured with the colorimetric methyl-thiazol-tetrazolium (MTT) assay, and long-term clinical response to chemotherapy in 152 children with newly diagnosed acute lymphoblastic leukemia. At risk-group stratified analyses, in vitro resistance to prednisolone, L-asparaginase, and vincristine were each significantly (P < .01) related to the probability of disease-free survival (pDFS) after combination chemotherapy. The combination of data for prednisolone, L-asparaginase, and vincristine provided a drug-resistance profile with prognostic independent significance superior to that of any single drug or any other factor. The 3-years pDFS was 100% for the group with the most sensitive profile, 20% of all patients, 84% (SE 6%) for the group with an intermediately sensitive profile, 40% of all patients, and 43% (SE 8%) for the remaining group with the most resistant profile (P < .001). In conclusion, the extent of in vitro cellular resistance to prednisolone, L-asparaginase, and vincristine, measured using the MTT assay, was significantly related to the clinical response to combination chemotherapy. Treatment failure in newly diagnosed childhood ALL can be predicted based on cellular drug resistance data.

Comparison of the antileukemic activity in vitro of dexamethasone and prednisolone in childhood acute lymphoblastic leukemia

It is generally assumed that prednisolone (PRD) and dexamethasone (DXM) have equal glucocorticoid activity of PRD is given at sevenfold higher doses. Results of clinical studies of childhood acute lymphoblastic leukemia (ALL) suggested that DXM is more potent relative to PRD than assumed. The purpose of this study was to determine the relative antileukemic activity of PRD phosphate and DXM phosphate in 133 untreated childhood ALL samples in vitro, using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium-bromide (MTT) assay. There was a marked variation in antileukemic activity of both agents among the patient samples. The median LC50 (drug concentration lethal to 50% of the ALL cells) for PRD phosphate was 3.50 microM, for DXM phosphate 0.20 microM. The individually calculated ratios of the LC50 values for PRD and DXM phosphate showed a large range from 0.7 to >500, with a median of 16.2. This 16-fold difference could not be explained by differences between these glucocorticoids in stability, hydrolysis into unesterified drug, adhesion to the wall of the microculture plates, or protein binding. ALL cells were cross-resistant to PRD and DXM phosphate (correlation coefficient = 0.85, P<0.000001). We conclude that the in vitro antileukemic activity of DXM phosphate is median 16-fold higher than that of PRD phosphate, which contrasts to the generally assumed factor of 7. Based on the higher potency of DXM, and its more favorable pharmacokinetics as reported in the literature, DXM may be preferred to PRD as the glucocorticoid in the treatment of ALL.

Prognostic significance of peanut agglutinin binding in childhood acute lymphoblastic leukemia

We previously reported the favorable prognosis associated with positive peanut agglutinin (PNA) binding in childhood T cell acute lymphoblastic leukemia (ALL), and hypothesized that this may be related to glucocorticoid sensitivity (Veerman et al. Cancer Res 1985, 45: 1890). The purposes of this prospective study involving 202 children with newly diagnosed ALL were to determine the relationship between PNA binding and (1) immunophenotype; (2) in vitro resistance to prednisolone (PRD) and dexamethasone and other drugs; (3) clinical response to a systemic PRD monotherapy (plus one intrathecal injection with methotrexate); and (4) multidrug chemotherapy. PNA positivity was more frequent in T cell ALL (65% of 43 cases) than in pro-B (0% of seven cases), common (17% of 106 cases) and pre-B (16% of 45 cases) ALL (P < 0.001). PNA binding was not associated with in vitro resistance to PRD or dexamethasone. However, in 38 evaluable T cell ALL patients, nine of 13 PNA-negative cases were clinically poor responders to PRD, while all 25 PNA-positive cases were good responders to PRD clinically (P < 0.0001). The four clinically poor PRD responders with B cell precursor (BCP)-ALL were also PNA negative. Within T cell ALL, PNA-positive patients had a 3.4-fold (95% Cl, 1.1-10.4, P = 0.03) lower relative risk of any event, than PNA-negative patients. Within BCP-ALL, PNA binding was not of prognostic significance. In conclusion, PNA positivity, especially frequent in T cell ALL, is a marker for a subgroup of childhood ALL patients who are very likely to respond well to systemic PRD 'monotherapy'. In addition, PNA positivity is a favorable prognostic factor in T cell ALL.

In vitro cellular drug resistance in children with relapsed/refractory acute lymphoblastic leukemia

Cellular drug resistance is thought to be an important cause of the poor prognosis for children with relapsed or refractory acute lymphoblastic leukemia (ALL), but it is unknown when, to which drugs, and to what extent resistance is present. We determined in vitro resistance to 13 drugs with the MTT assay. Compared with 141 children with initial ALL, cells from 137 children with relapsed ALL were significantly more resistant to glucocorticoids, L-asparaginase, anthracyclines, and thiopurines, but not to vinca-alkaloids, cytarabine, ifosfamide, and epipodophyllotoxins. Relapsed ALL cells expressed the highest level of resistance to glucocorticoids, with a median level 357- and >24-fold more resistant to prednisolone and dexamethasone, respectively, than initial ALL cells, whereas the resistance ratios for the other drugs differed from 0.8- to 1.9-fold, intraindividual comparisons between initial and relapsed samples from 16 children with ALL showed that both de novo and acquired drug resistance were involved. Specific in vitro drug-resistance profiles were associated with high-risk relapsed ALL groups. In vitro drug resistance was also related to the clinical response to chemotherapy in relapsed/refractory childhood ALL. We conclude that drug resistance may explain the poor prognosis for children with relapsed/refractory ALL. These day may be helpful to design alternative treatment regimens for relapsed childhood ALL.

In vitro chemosensitivity assessed with the MTT assay in childhood acute non-lymphoblastic leukemia

Cellular drug resistance is supposed to play a major role in chemotherapy failures which frequently occur in childhood acute non-lymphoblastic leukemia (ANLL). Therefore, we determined in vitro chemosensitivity to daunorubicin, doxorubicin, mitoxantrone, 6-thioguanine, etoposide, and cytosine arabinoside (Ara-C) in childhood ANLL using the colorimetric MTT assay. The 4-day MTT assay was successfully performed in 62/73 samples obtained from 53 children with ANLL. We obtained comparable results from bone marrow or peripheral blood samples, and from fresh or cryopreserved samples. In vitro chemosensitivity was not related to clinical features such as sex, age, white blood cell count, or FAB-types. The group of poor responders to chemotherapy was median 3-fold more resistant to Ara-C than the group of good responders, but identification of a threshold for Ara-C sensitivity predictive for individual responses was limited due to the great overlap of in vitro chemosensitivities between both groups. Children with relapsed ANLL were in vitro median 3-fold more resistant to Ara-C than the initial ANLL group. No significant differences for the other drugs were observed with respect to clinical response or disease status. These results suggest that in vitro resistance to Ara-C plays an important role in chemotherapy failures in childhood ANLL, but larger studies are necessary to establish the predictive value of Ara-C sensitivity assessed with the MTT assay.

Clinical and cell biological features related to cellular drug resistance of childhood acute lymphoblastic leukemia cells

Several clinical and cell biological features, such as sex, age, leukemic cell burden, morphologic FAB type, and immunophenotype, have prognostic value in childhood acute lymphoblastic leukemia (ALL). The explanation for their prognostic significance is unclear, but might be related to cellular drug resistance. We prospectively studied the relation between the above mentioned features with resistance to 13 drugs in 144 childhood ALL samples obtained at initial diagnosis. The MTT assay was used for drug resistance testing. The interindividual differences in drug resistance were very large and exceeded those between the several subgroups. There was generally no significant relation between sex, leukemic cell burden, and FAB type with drug resistance. However, subgroups with a worse prognosis as defined by age (< 18 months and > 120 months at diagnosis) or immunophenotype (pro-B ALL and T-ALL) did show relatively resistant drug resistance profiles as compared to the subgroups with a better prognosis (age 18-120 months, common and pre-B ALL). Within the group of common and pre-B ALL and compared to the intermediate age-group, samples of the younger children were significantly more resistant to daunorubicin, mitoxantrone and teniposide, and samples of the older children were significantly more resistant to prednisolone and mercaptopurine. Pro-B ALL samples were significantly more resistant to 1-asparaginase and thioguanine, and T-ALL samples were significantly more resistant to prednisolone, dexamethasone, 1-asparaginase, vincristine, vindesine, daunorubicin, doxorubicin, teniposide, and ifosfamide, than the group of common and pre-B ALL cases. We conclude that the prognostic significance of age and immunophenotype in particular may be explained, at least partly, by its relation with resistance to certain drugs. The results of this study may be useful for future rational improvements of chemotherapeutic regimens in childhood ALL.

Topoisomerase II alpha gene expression in childhood acute lymphoblastic leukemia

Previously, we showed that in vitro resistance to daunorubicin (DNR) at initial diagnosis was related to a poor long-term clinical outcome in childhood acute lymphoblastic leukemia (ALL), and that cells of relapsed ALL were in vitro more resistant to DNR than cells of untreated ALL. Topoisomerase II (Topo II) is an intracellular target for anthracyclines and epipodophyllotoxins. Decreased levels and/or activity of Topo II have been associated with multidrug resistance in cell lines. We investigated Topo II alpha gene expression in fresh leukemic samples from 19 children with untreated and 14 children with relapsed ALL using a sensitive RNase protection assay. The in vitro cytotoxicity of the Topo II inhibitors DNA and teniposide (VM26) was measured using the MTT assay, and the cell cycle distribution of leukemic samples was analyzed by DNA flow cytometry. Results showed that (1) relapsed ALL samples were more resistant to DNR, but not to VM26 compared to untreated samples; (2) large interpatient variations existed in both Topo II alpha gene expression and in vitro cytotoxicity results; (3) Topo II alpha gene expression was detectable in 29/33 childhood ALL samples with a median expression of 5% the level of a relatively chemosensitive human small cell lung cancer cell line; (4) Topo II alpha gene expression did not differ between untreated and relapsed ALL; (5) Topo II alpha gene expression was positively correlated with the percentage of ALL cells in S- and G2M-phase, but not with the in vitro cytotoxicity of the drugs tested. In conclusion, resistance to DNR in childhood ALL can not be explained by decreased levels of Topo II alpha gene expression, but additional Topo II activity studies in fresh leukemia samples may need further exploration.

Drug combination testing in acute lymphoblastic leukemia using the MTT assay

Drug resistance assays may be useful to identify drug interactions. For this purpose, we studied three drug combinations, each at 8-12 concentrations, with the MTT assay in acute lymphoblastic leukemia (ALL) samples from 34 children obtained at initial diagnosis. This resulted in a total of 518 comparisons between expected and observed leukemic cell survivals. The combinations prednisolone (PRD) with vincristine (VCR), PRD with mafosfamide (MAF), and PRD with daunorubicin (DNR) were tested without technical difficulties, and without an increased assay variation as compared to single drugs. We observed a marked heterogeneity in drug interactions between patients, between combinations, and between different concentrations within one specific combination. Between PRD+VCR, synergism was found in 46%, antagonism in 18%, and additivity in 36% of the 228 observations. Between PRD+MAF, synergism was found in 51%, antagonism in 20%, and additivity in 29% of the 140 observations. Between PRD+DNR, synergism was found in 35%, antagonism in 31%, and additivity in 34% of the 150 observations. PRD+VCR and PRD+MAF showed more often synergism than PRD+DNR, while antagonism was observed more frequently between PRD+DNR (p < 0.05). However, the magnitude of antagonism was not much different between the three drug combinations, nor was there a significant antagonistic interaction in any of the drug combinations tested, if all samples were considered together. We conclude that the MTT assay can be used to study drug interactions in vitro in ALL samples. The type of interaction was different between patients, and depends on the drug combination and concentrations. The combinations PRD+VCR and PRD+MAF generally showed additive and even synergistic interactions. The cytotoxicity of PRD+DNR was generally not markedly higher than that of the most active single drug.

Favorable prognosis of hyperdiploid common acute lymphoblastic leukemia may be explained by sensitivity to antimetabolites and other drugs: results of an in vitro study

DNA hyperdiploidy is a favorable prognostic factor in childhood acute lymphoblastic leukemia (ALL). The explanation for this prognostic significance is largely unknown. We have studied whether DNA ploidy was related to cellular resistance to 12 drugs, assessed with the methyl-thiazol-tetrazolium assay, in samples of 74 children with common (CD10+ precursor B-cell) ALL. Sixteen patients had hyperdiploid ALL cells and 58 patients had nonhyperdiploid ALL cells. Hyperdiploid ALL cells were more sensitive to mercaptopurine (median, 9.0-fold; P = .000003), to thioguanine (1.4-fold; P = .023), to cytarabine (1.8-fold; P = .016), and to I-asparaginase (19.5-fold; P = .022) than were nonhyperdiploid ALL cells. In contrast, these two ploidy groups did not differ significantly in resistance to prednisolone, dexamethasone, vincristine, vindesine, daunorubicin, doxorubicin, mitoxantrone, and teniposide. The percentage of S-phase cells was higher (P = .05) in the hyperdiploid ALL samples (median, 8.5%) than in the nonhyperdiploid ALL samples (median, 5.7%). However, the percentage of cells in S-phase was not significantly related to in vitro drug resistance. We conclude that the favorable prognosis associated with DNA hyperdiploidy in childhood common ALL may be explained by a relative sensitivity of hyperdiploid common ALL cells to antimetabolites, especially to mercaptopurine and to I-asparaginase.

Mononuclear cells contaminating acute lymphoblastic leukaemic samples tested for cellular drug resistance using the methyl-thiazol-tetrazolium assay

The methyl-thiazol-tetrazolium (MTT) assay is a drug resistance assay which cannot discriminate between malignant and non-malignant cells. We previously reported that samples with > or = 80% leukaemic cells at the start of culture give similar results in the MTT assay and the differential staining cytotoxicity assay, in which a discrimination between malignant and non-malignant cells can be made. However, the percentage of leukaemic cells may change during culture, which might affect the results of the MTT assay. We studied 106 untreated childhood acute lymphoblastic leukemia (ALL) samples with > or = 80% leukaemic cells at the start of culture. This percentage decreased below 80% in 28%, and below 70% in 13%, of the samples after 4 days of culture. A decrease below 70% occurred more often in case of 80-89% leukaemic cells (9/29) than in case of > or = 90% leukaemic cells at the start of culture (5/77, P = 0.0009). Samples with < 70% leukaemic cells after culture were significantly more resistant to 6 out of 13 drugs, and showed a trend towards being more resistant to two more drugs, than samples with > or = 80% leukaemic cells. No such differences were seen between samples with 70-79% and samples with > or = 80% leukaemic cells after culture. We next studied in another 30 ALL samples whether contaminating mononuclear cells could be removed by using immunoamagnetic beads. Using a beads to target cell ratio of 10:1, the percentage of leukaemic cells increased from mean 72% (s.d. 9.3%) to mean 87% (s.d. 6.7%), with an absolute increase of 2-35%. The recovery of leukaemic cells was mean 82.1% (range 56-100%, s.d. 14.0%). The procedure itself did not influence the results of the MTT assay in three samples containing only leukaemic cells. We conclude that it is important to determine the percentage of leukaemic cells at the start and at the end of the MTT assay and similar drug resistance assays. Contaminating mononuclear cells can be successfully removed from ALL samples using immunomagnetic beads. This approach may increase the number of leukaemic samples which can be evaluated for cellular drug resistance with the MTT assay or a similar cell culture drug resistance assay.

Cellular drug resistance in childhood leukemia

The response to chemotherapy is determined essentially by two factors: first, pharmacokinetic factors, determining which concentration of drug reaches the malignant cells, and second, cellular drug resistance of these cells, determining how many of them will be killed by that concentration of drug. The study of cellular drug resistance has been stimulated by the development of short-term 'total cell kill' assays, such as the MTT assay, for use on patient samples. The drug resistance profiles differed markedly between ALL and ANLL, between immunophenotypic and karyotypic subgroups within ALL, and between initial and relapsed ALL. The results of the MTT assay showed a significant relation between the antileukemic activity of prednisolone in vitro and the clinical response to systemic monotherapy with that drug. At multivariate analysis including several well-known prognostic factors (WBC, age, immunophenotype) only the in vitro resistance to prednisolone, dexamethasone, L-asparaginase, and daunorubicin was significantly related to clinical outcome. At multiple regression analysis, combination of the results for prednisolone, L-asparaginase, and vincristine made it possible to distinguish between three patient groups with increasing levels of drug resistance and markedly different probabilities of 2-year disease-free survival: 100%, 83%, and 60%. These results show that in vitro drug resistance testing can give a correct prediction of prognosis, superior to that of currently used prognostic factors. Stratification of prognostic groups based on the results of drug resistance testing is feasible and should be introduced into new clinical trials. Many questions now remaining could be answered within carefully designed preclinical and clinical studies.

Different cellular drug resistance profiles in childhood lymphoblastic and non-lymphoblastic leukemia: a preliminary report

The better prognosis of acute lymphoblastic leukemia (ALL) than of acute non-lymphoblastic leukemia (ANLL) in children, and the often observed better prognosis of myeloid-antigen (MyAg) negative ALL than of MyAg-positive ALL, may be related to differences in cellular drug resistance. We therefore compared the resistance to 12 drugs of 125 ALL and 28 ANLL samples with the MTT assay. ALL samples were median > 75-fold more sensitive to the glucocorticoids prednisolone and dexamethasone (p < 0.00001), and 2-fold more sensitive to vincristine (p = 0.05) than ANLL samples. Differences for the other drugs were not significant. MyAg-negative ALL samples were more sensitive to glucocorticoids than MyAg-positive ALL-samples (p < or = 0.04). Prednisolone, and dexamethasone if tested, had a stimulatory effect on leukemic cell survival in 36% of ANLL, but in only 2% of ALL samples (p < 0.0001). Vincristine, and vindesine if tested, had a similar effect in 11% of ANLL, and in 4% of ALL samples (p = 0.11). We conclude that the more favorable response of ALL against ANLL to combination chemotherapy in children may be explained by the higher antileukemic activity of glucocorticoids and of vincristine in ALL, while none of the drugs was more active in ANLL. Similarly, the better prognosis of MyAg-negative ALL than of MyAg-positive ALL may be explained by a relative sensitivity to glucocorticoids. Glucocorticoids and vinca-alkaloids induced leukemia cell proliferation in part of the samples, most frequently in ANLL. The findings may be useful in the design of new chemotherapeutic regimens for ALL and ANLL.

Glucocorticoid resistance in childhood leukemia

Glucocorticoids (GC) are being used in the treatment of childhood leukemia for several decades, most successfully in newly diagnosed acute lymphoblastic leukemia (ALL). However, GC resistance is seen in 10-30% of untreated ALL patients, and is much more frequent in relapsed ALL and in acute nonlymphoblastic leukemia (ANLL). Sensitivity or resistance to GC can be measured using a cell culture drug resistance assay. For this purpose, we use the colorimetric methyl-thiazol-tetrazolium (MTT) assay. We have shown that GC resistance in childhood leukemia is related to clinical and cell biological features, and to the clinical outcome after multi-drug chemotherapy. These results are summarized in this review. In addition, we describe the apoptotic 'cell-lysis pathway' by which GC exert their antileukemic activity. This description provides a model to discuss the mechanisms of GC resistance, and to summarize the relevant literature. Possible levels of resistance relate to the diffusion of GC through the cell membrane, binding to the GC receptor (GCR), activation of the GC-GCR complex, translocation of the complex into the nucleus, binding to DNA, endonuclease-mediated DNA fragmentation, and DNA repair. A low number of GCR has been shown to be the cause of resistance in some children with ALL. However, GC resistance is likely to be caused at the post-receptor level in most leukemias. Unfortunately, there is still a lack of knowledge relating to the clinical relevance of mechanisms of GC resistance at the post-receptor level. Studies on the mechanisms of GC resistance other than those directly related to the GCR should be initiated, especially if patient material is used, as the results might indicate ways to circumvent or modulate GC resistance. A further increase in our knowledge regarding the relation between GC resistance and patient and cell biological features, the clinical relevance of GC resistance, and the mechanisms of GC resistance in leukemia patients, may contribute to further improvement in the results of GC therapy in leukemia.

Clinical relevance of in vitro drug resistance testing in childhood acute lymphoblastic leukemia: the state of the art

Nowadays about two-thirds of children with acute lymphoblastic leukemia (ALL) can be cured with chemotherapy, but one-third die from the disease. The clinical response of leukemic cells to chemotherapy is roughly due to two factors: the effective drug levels reaching the cells and the resistance of these cells to the drugs. The clinical value of cellular drug resistance in children with ALL is not known. We developed an in vitro assay to study drug resistance in these children. In this article, the main results obtained with this MTT assay on samples from 137 children with ALL are summarized: (1) patients whose cells are resistant to several drugs at initial diagnosis have a poor prognosis; (2) relapsed leukemias show a considerable drug resistance which might partly explain the poor prognosis. Relapsed cases differ in their type and degree of resistance; (3) the poor outcome of high risk groups as defined by age and immunophenotype can partly be explained by specific patterns of drug resistance; (4) P-glycoprotein-mediated multidrug resistance is not an important cause of resistance in childhood ALL; and (5) no relation exists between the activities of the purine enzymes HGPRT, 5'NT, ADA, and PNP and drug resistance in childhood ALL. The conclusion is that in vitro drug resistance data have clinical relevance and can be used to develop more effective and less toxic treatment strategies in childhood ALL.

Cellular drug resistance profiles that might explain the prognostic value of immunophenotype and age in childhood acute lymphoblastic leukemia

Immunophenotype and age have prognostic value in childhood acute lymphoblastic leukemia (ALL) but how this operates is not understood. In 84 children with ALL at initial diagnosis we studied the correlation between these factors and the in vitro resistance to eight drugs, determined with the 3-(4,5-dimethylthiazol-2-yl-2, 5-diphenyl tetrazolium bromide (MTT) assay. B-lineage ALL samples were classified into four differentiation stages: the CD10- proB ALL; cALL; preB ALL with cytoplasmic mu positive ALL cells; and B-ALL with surface immunoglobulin-positive (Ig+) cells. cALL and preB ALL cases have the best prognosis; proB and T-ALL cases show a worse prognosis and B-ALL the poorest prognosis. Patients aged < 18 months and > 10 years have a poor prognosis compared to patients in the intermediate age group. Our results show that cALL and preB ALL cells were the most drug-sensitive cells compared to the other phenotypes. No differences were found between cALL and preB ALL cases with the exception that preB cells were more sensitive to mustine and mafosfamide (Maf). Compared to cALL and preB ALL cases, T-ALL cases were significantly more resistant to prednisolone (Pred), daunorubicin (DNR), L-asparaginase (L-Asp), cytosine arabinoside (AraC), and Maf; proB ALL cases were more resistant to Pred, DNR, L-Asp, and 6-thioguanine. The three B-ALL cases were resistant to vincristine and DNR. Two out of three B-ALL were resistant to Pred. Compared to cells from patients aged 18 months to 10 years, cells from children < 18 months were more resistant to Pred and DNR; cells from children > 10 years were more resistant to Pred. We conclude that cellular drug-resistance patterns might at least partly explain the prognostic value of immunophenotype and age in childhood ALL.

[The treatment of recurrence in children with acute lymphatic leukemia. Current results and various developments]

The results of current treatment of relapsed childhood acute lymphoblastic leukemia (ALL) are discussed, together with some recent developments which (might) influence such treatment. At present more than 95% of children with ALL will achieve a complete remission (CR), and +/- 70% will remain in CR. Nevertheless, 20-30% of the patients suffer a relapse, which implies a less favorable prognosis. However, after intensive treatment a part of these patients will have a prolonged second complete remission: 30-50% of children with a late relapse and 0-20% of children with an early relapse. It is important to prevent the occurrence of a relapse. The identification at diagnosis of patients at high risk for a relapse, and a subsequent more specific and more intensive treatment of these patients might contribute to that goal. Well-known risk factors are briefly mentioned, factors of which the prognostic significances is therapy-dependent. In addition, the treatment of relapsed ALL needs further improvement. Some alternatives to achieve this goal are discussed, including the role of in vitro cytostatic drug resistance testing.

In vitro drug sensitivity of normal peripheral blood lymphocytes and childhood leukaemic cells from bone marrow and peripheral blood

In vitro drug sensitivity of leukaemic cells might be influenced by the contamination of such a sample with non-malignant cells and the sample source. To study this, sensitivity of normal peripheral blood (PB) lymphocytes to a number of cytostatic drugs was assessed with the MTT assay. We compared this sensitivity with the drug sensitivity of leukaemic cells of 38 children with acute lymphoblastic leukaemia. We also studied a possible differential sensitivity of leukaemic cells from bone marrow (BM) and PB. The following drugs were used: Prednisolone, dexamethasone, 6-mercaptopurine, 6-thioguanine, cytosine arabinoside, vincristine, vindesine, daunorubicin, doxorubicin, mafosfamide (Maf), 4-hydroperoxy-ifosfamide, teniposide, mitoxantrone, L-asparaginase, methotrexate and mustine. Normal PB lymphocytes were significantly more resistant to all drugs tested, except to Maf. Leukaemic BM and PB cells from 38 patients (unpaired samples) showed no significant differences in sensitivity to any of the drugs. Moreover, in 11 of 12 children with acute leukaemia of whom we investigated simultaneously obtained BM and PB (paired samples), their leukaemic BM and PB cells showed comparable drug sensitivity profiles. In one patient the BM cells were more sensitive to most drugs than those from the PB, but the actual differences in sensitivity were small. We conclude that the contamination of a leukaemic sample with normal PB lymphocytes will influence the results of the MTT assay. The source of the leukaemic sample, BM or PB, does not significantly influence the assay results.

Primary spinal epidural extraosseous Ewing's sarcoma

The case of a 7-year-old boy with a spinal epidural extraosseous Ewing's sarcoma (EES) is presented. He is in complete remission without neurologic deficit 40 months after diagnosis. Another 15 cases were found in the literature and are discussed together with this patient. Twelve of them were male patients. The mean age of the patients was 17.5 years (range, 4 to 47). Symptoms included back pain and/or radicular pain (100%), paresis of one or both legs (83%), sensory disturbances, and bladder and bowel dysfunction. The mean diagnostic delay was 5.8 months. Each patient underwent laminectomy; complete resection of the tumor was impossible in more than 50% of the cases. Most patients received radiation therapy and/or chemotherapy. Four patients suffered from local recurrence, eight from metastases. Ten (63%) patients died, 1 to 48 months (mean, 16) after diagnosis. The differential diagnosis is discussed, including disk herniation and several benign and malignant tumors.

[Thrombocytopenia and absent radii syndrome (TAR). Case report and literature discussion]

A girl is described with the thrombocytopenia and absent radii (TAR) syndrome. The literature concerning this rare, autosomal recessive inherited syndrome is discussed. The main characteristics are bilateral radius aplasia in which the thumbs are present in combination with a a- or hypomegakaryocytic thrombocytopenia. Many other anomalies and associated disorders are described in the literature, especially in the haematological, skeletal, cardiac and intestinal fields. The treatment is mainly directed to the haemorrhagic diathesis and the orthopaedic problems. It is suggested that the mortality-rate--mainly a consequence of haemorrhage--which used to be 30-40%, has diminished thanks to the evolution of platelet transfusion therapy.