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Abstract Defining genetic factors impacting chemotherapy failure can help to better predict response and identify drug resistance mechanisms. However, there is limited understanding of the contribution of inherited noncoding genetic variation on inter-individual differences in chemotherapy response in childhood acute lymphoblastic leukemia (ALL). Here we map inherited noncoding variants associated with treatment outcome and/or chemotherapeutic drug resistance to ALL cis-regulatory elements and investigate their gene regulatory potential and target gene connectivity using massively parallel reporter assays and three-dimensional chromatin looping assays, respectively. We identify 54 variants with transcriptional effects and high-confidence gene connectivity. Additionally, functional interrogation of the top variant, rs1247117, reveals changes in chromatin accessibility, PU.1 binding affinity and gene expression, and deletion of the genomic interval containing rs1247117 sensitizes cells to vincristine. Together, these data demonstrate that noncoding regulatory variants associated with diverse pharmacological traits harbor significant effects on allele-specific transcriptional activity and impact sensitivity to antileukemic agents.

Not available.

CASZ1 is a conserved transcription factor involved in neural development, blood vessel assembly and heart morphogenesis. CASZ1 has been implicated in cancer, either suppressing or promoting tumor development depending on the tissue. However, the impact of CASZ1 on hematological tumors remains unknown. Here, we show that the T-cell oncogenic transcription factor TAL1 is a direct positive regulator of CASZ1, that T-cell acute lymphoblastic leukemia (T-ALL) samples at diagnosis overexpress CASZ1b isoform, and that CASZ1b expression in patient samples correlates with PI3K-AKT-mTOR signaling pathway activation. In agreement, overexpression of CASZ1b in both Ba/F3 and T-ALL cells leads to the activation of PI3K signaling pathway, which is required for CASZ1b-mediated transformation of Ba/F3 cells in vitro and malignant expansion in vivo. We further demonstrate that CASZ1b cooperates with activated NOTCH1 to promote T-ALL development in zebrafish, and that CASZ1b protects human T-ALL cells from serum deprivation and treatment with chemotherapeutic drugs. Taken together, our studies indicate that CASZ1b is a TAL1-regulated gene that promotes T-ALL development and resistance to chemotherapy.

Abstract Purpose Studies of the association between body mass index (BMI) at diagnosis and treatment outcome in children with acute lymphoblastic leukemia (ALL) have yielded inconsistent results. Hence, we conducted a retrospective study in a large cohort of Chinese children with ALL treated with contemporary protocols. Patients and Methods A total of 1437 children (62.1% male; median age at diagnosis 5.7 years, range: 2.3–16.3 years) were enrolled in two consecutive clinical trials at the Shanghai Children's Medical Center. The rates of overall survival, event‐free survival, relapse, treatment‐related mortality, and adverse events were compared among patients who were underweight (BMI 85th to

Abstract Objective Allergic reactions to pegaspargase during ALL therapy are typically due to antibodies against polyethylene glycol (PEG), which is also used as a stabilizing agent in mRNA‐based SARS‐CoV‐2 vaccines. To evaluate the safety of these vaccines in patients with anti‐pegaspargase antibodies. Methods We retrospectively reviewed the records of patients treated for ALL who had received SARS‐CoV‐2 vaccinations. All patients had antibodies against pegaspargase assayed during ALL therapy prospectively and in response to clinical allergies. Symptoms of intolerance to vaccination were gathered retrospectively from chart abstraction. Results SARS‐CoV‐2 vaccination was well tolerated in all 78 patients with prior exposure to pegaspargase as part of their leukemia therapy. No reactions were observed in the 54 patients without a history of anti‐pegaspargase antibodies or in 19 patients with antibodies who received mRNA vaccination. 1 patient who received the polysorbate containing Janssen vaccine experienced mild symptoms after vaccination not meeting the criteria of clinical allergy which spontaneously resolved within 25 minutes. Conclusion SARS‐CoV‐2 vaccination is safe in this population.

Venous thrombosis is a common adverse effect of modern therapy for acute lymphoblastic leukemia (ALL). Prior studies to identify risks of thrombosis in pediatric ALL have been limited by genetic screens of pre-identified genetic variants or genome- wide association studies (GWAS) in ancestrally uniform populations. To address this, we performed a retrospective cohort evaluation of thrombosis risk in 1,005 children treated for newly diagnosed ALL. Genetic risk factors were comprehensively evaluated from genome-wide single nucleotide polymorphism (SNP) arrays and were evaluated using Cox regression adjusting for identified clinical risk factors and genetic ancestry. The cumulative incidence of thrombosis was 7.8%. In multivariate analysis, older age, T-lineage ALL, and non-O blood group were associated with increased thrombosis while non-low-risk treatment and higher presenting white blood cell count trended toward increased thrombosis. No SNP reached genome-wide significance. The SNP most strongly associated with thrombosis was rs2874964 near RFXAP (G risk allele; P=4x10-7; hazard ratio [HR] =2.8). In patients of non-European ancestry, rs55689276 near the α globin cluster (P=1.28x10-6; HR=27) was most strongly associated with thrombosis. Among GWAS catalogue SNP reported to be associated with thrombosis, rs2519093 (T risk allele, P=4.8x10-4; HR=2.1), an intronic variant in ABO, was most strongly associated with risk in this cohort. Classic thrombophilia risks were not associated with thrombosis. Our study confirms known clinical risk features associated with thrombosis risk in children with ALL. In this ancestrally diverse cohort, genetic risks linked to thrombosis risk aggregated in erythrocyte-related SNP, suggesting the critical role of this tissue in thrombosis risk.

Different molecular subtypes defined by specific gene rearrangements have been described for acute lymphoblastic leukaemia (ALL). Here, the authors show that ZNF384 fusion activates FLT3 expression conferring a therapeutic vulnerability for ZNF384- rearranged ALL subtype.

This study explored results of therapy of children with acute lymphoblastic leukemia (ALL) in China, recent progress, and challenges. Included are a survey of therapy outcomes of ALL in Chinese children nationwide, comparison of these data with global ALL therapy outcomes, analyses of obstacles to improving outcomes, and suggestions of how progress can be achieved. Therapy outcomes at many Chinese pediatric cancer centers are approaching those of resource-rich countries. However, nationwide outcomes still need improvement. Obstacles include suboptimal clinical trials participation, children without adequate health care funding, human resource shortages, especially physicians expert in pediatric hematology and oncology, and social-economic disparities. We suggest how these obstacles have been and continue to be remedied including expanded access to protocol-based therapy, improved supportive care, health care reforms, recruitment of trained personnel, and international collaborations. China has made substantial progress treating children with ALL. We envision even better outcomes in the near future.

PURPOSESurvivors of childhood cancer often experience treatment-related chronic health conditions. Given its vast population, China shares a large proportion of the global childhood cancer burden. Yet, screening and treatment of late effects in survivors of childhood cancer remain underaddressed in most regions of China. This study aimed to identify high-priority late effects for harmonizing screening guidelines within the Chinese Children's Cancer Group (CCCG), as well as barriers and enablers of the implementation of surveillance recommendations in local practice.METHODSTo establish clinical consensus, 12 expert panelists who represent major institutions within the CCCG completed a Delphi survey and participated in a focus group discussion. The survey solicited ratings of the prevalence, severity, and priority for screening of 45 late effects. Major themes identified from the focus group were analyzed using thematic analysis.RESULTSThe Delphi survey identified eight high-priority late effects for harmonization within CCCG: osteonecrosis, osteoporosis, left ventricular dysfunction, secondary brain tumors, treatment-related myeloid leukemia, gonadal dysfunction, growth hormone deficiency, and neurocognitive deficits. The common barriers to implementing survivorship programs include lack of support and resources for clinicians to provide follow-up care. Patients were also concerned about privacy issues and lacked awareness of late effects. Many institutions also lacked rehabilitation expertise and referral pathways.CONCLUSIONBy identifying obstacles related to the professional setting, patient behavior, and organization of care, our study identified resources and a framework for establishing collaborative strategies to facilitate follow-up care of childhood cancer survivors in China.

PurposeAdult survivors of childhood acute lymphoblastic leukemia (ALL) have impaired adaptive physical function and poor health-related quality of life (HRQoL). Obesity may contribute to these impairments by increasing the physiological cost of walking. Due to treatment exposures during ALL therapy, survivors’ cost of walking may be more impacted by obesity than the general population. Therefore, we examined associations between obesity, persistent motor neuropathy, and energy cost of walking; and examined associations between energy cost of walking, adaptive physical function, and HRQoL, in adult survivors of childhood ALL vs. community controls.MethodsObesity was measured via body mass index (BMI) and body fat percentage. The physiological cost index (PCI) was calculated from the six-minute walk test. Adaptive physical functioning was measured using two tests: the timed up and go (TUG) test and the physical performance test. Persistent motor neuropathy was measured using the modified total neuropathy score; HRQoL was measured using the Short-Form-36 questionnaire. The associations between obesity and PCI were evaluated using multivariable linear regressions in adult survivors of childhood ALL (n = 1,166) and community controls (n = 491). Then, the associations between PCI, adaptive physical functioning and peripheral neuropathy were examined using multivariable linear regressions. Finally, to determine the association between obesity, and neuropathy on PCI, while accounting for potential lifestyle and treatment confounders, a three model, sequential linear regression was used.ResultsObese individuals (BMI > 40 kg/m2 and excess body fat percentage [males: >25%; females: >33%]) had higher PCI compared to those with normal BMI and body fat percentage (0.56 ± 0.01 vs. 0.49 ± 0.009 beats/meter p 95th percentile of community controls had lower HRQoL compared to un-impaired ALL survivors: 46.9 ± 0.56 vs. 50.4 ± 1.08, respectively (p

Abstract Vincristine (VCR) is one of the most widely prescribed medications for treating solid tumors and acute lymphoblastic leukemia (ALL) in children and adults. However, its major dose‐limiting toxicity is peripheral neuropathy that can disrupt curative therapy. Peripheral neuropathy can also persist into adulthood, compromising quality of life of childhood cancer survivors. Reducing VCR‐induced neurotoxicity without compromising its anticancer effects would be ideal. Here, we show that low expression of NHP2L1 is associated with increased sensitivity of primary leukemia cells to VCR, and that concomitant administration of VCR with inhibitors of NHP2L1 increases VCR cytotoxicity in leukemia cells, prolongs survival of ALL xenograft mice, but decreases VCR effects on human‐induced pluripotent stem cell‐derived neurons and mitigates neurotoxicity in mice. These findings offer a strategy for increasing VCR’s antileukemic effects while reducing peripheral neuropathy in patients treated with this widely prescribed medication.

Abstract Background Fluoroquinolone antibiotics are frequently utilized in pediatric oncology patients as prophylaxis or step‐down therapy following broad spectrum beta‐lactam therapy for febrile neutropenia. Concerns regarding neurotoxicity limit the use of these agents. No studies have evaluated the association between fluoroquinolone use and neurotoxicity in pediatric oncology patients receiving other neurotoxic agents such as vincristine. Methods An observational cohort study comprising patients aged 0‐18 at diagnosis enrolled on a prospective study for treatment of acute lymphoblastic leukemia (ALL) at a pediatric comprehensive cancer center between October 2007 and November 2018. Data for neuropathic pain and sensory or motor neuropathy were collected prospectively, and a Cox proportional hazards regression model was used to evaluate associations between administration of fluoroquinolone antibiotics during induction therapy and subsequent development of vincristine‐induced peripheral neurotoxicity (VIPN). Results A total of 598 participants were enrolled, including 338 (57%) who received fluoroquinolones during induction therapy; of these 470 (79%) were diagnosed with VIPN and 139 (23%) were diagnosed with high‐grade (Grade 3+) VIPN. On unadjusted analyses, and analyses adjusted for age and race, there was no evidence of an association between fluoroquinolone exposure and subsequent VIPN (hazard ratio [HR] 0.8, 95% CI 0.5‐1.04, P = .08) or high‐grade VIPN (HR 1.1, 95% CI 0.4‐2.2, P = .87). Conclusions The results of this observational study do not show an association between exposure to fluoroquinolone antibiotics during induction therapy for ALL and subsequent development of vincristine‐induced peripheral neuropathies, and suggest that a large increase in VIPN is unlikely.

B-cell acute lymphoblastic leukaemia (B-ALL) is a common childhood cancer. Here, the authors conducted a meta-analysis with four genome-wide association studies, totalling 5,321 cases and 16,666 controls of European descent, identifying B-ALL risk loci, whose integration with epigenomic profiling indicates cell-cycle and B-cell development deregulation as central mechanisms in B-ALL susceptibility, often in a subtype-specific fashion.

Chemotherapy dosages are often compromised, but most reports lack data on dosages that are actually delivered. In two consecutive acute lymphoblastic leukemia trials that differed in their asparaginase formulation, native E. coli L-asparaginase in St. Jude Total 15 (T15, n=365) and pegaspargase in Total 16 (T16, n=524), we tallied the dose intensities for all drugs on the low-risk or standard-risk arms, analyzing 504,039 dosing records. The median dose intensity for each drug ranged from 61-100%. Dose intensities for several drugs were more than 10% higher on T15 than on T16: cyclophosphamide (P

Abstract Consolidation therapies for children with intermediate- or high-risk acute myeloid leukemia (AML) are urgently needed to achieve higher cure rates while limiting therapy-related toxicities. We determined if adoptive transfer of natural killer (NK) cells from haploidentical killer immunoglobulin–like receptor (KIR)–human leukocyte antigen (HLA)-mismatched donors may prolong event-free survival in children with intermediate-risk AML who were in first complete remission after chemotherapy. Patients received cyclophosphamide (Day − 7), fludarabine (Days − 6 through − 2), and subcutaneous interleukin-2 (Days − 1, 1, 3, 5, 7, and 9). Purified, unmanipulated NK cells were infused on Day 0, and NK cell chimerism and phenotyping from peripheral blood were performed on Days 7, 14, 21, and 28. As primary endpoint, the event-free survival was compared to a cohort of 55 patients who completed chemotherapy and were in first complete remission but did not receive NK cells. Donor NK cell kinetics were determined as secondary endpoints. Twenty-one patients (median age at diagnosis, 6.0 years [range, 0.1–15.3 years]) received a median of 12.5 × 106 NK cells/kg (range, 3.6–62.2 × 106 cells/kg) without major side effects. All but 3 demonstrated transient engraftment with donor NK cells (median peak donor chimerism, 4% [range, 0–43%]). KIR–HLA-mismatched NK cells expanded in 17 patients (81%) and contracted in 4 (19%). However, adoptive transfer of NK cells did not decrease the cumulative incidence of relapse (0.393 [95% confidence interval: 0.182–0.599] vs. 0.35 [0.209–0.495]; P = .556) and did not improve event-free (60.7 ± 10.9% vs. 69.1 ± 6.8%; P = .553) or overall survival (84.2 ± 8.5% vs. 79.1 ± 6.6%; P = .663) over chemotherapy alone. The lack of benefit may result from insufficient numbers and limited persistence of alloreactive donor NK cells but does not preclude its potential usefulness during other phases of therapy, or in combination with other immunotherapeutic agents. Trial registration www.clinicaltrials.gov, NCT00703820. Registered 24 June 2008.

Although cure rates for pediatric acute lymphoblastic leukemia (ALL) have now risen to more than 90%, subsets of patients with high-risk features continue to experience high rates of treatment failure and relapse. Recent work in minimal residual disease stratification and leukemia genomics have increased the ability to identify and classify these high-risk patients. In this review, we discuss this work to identify and classify patients with high-risk ALL. Novel therapeutics, which may have the potential to improve outcomes for these patients, are also discussed.

Survival for pediatric patients diagnosed with cancer has improved significantly. This achievement has been made possible due to new treatment modalities and the incorporation of a systematic multidisciplinary approach for supportive care. Understanding the distinctive cardiovascular characteristics of children undergoing cancer therapies has set the underpinnings to provide comprehensive care before, during, and after the management of cancer. Nonetheless, we acknowledge the challenge to understand the rapid expansion of oncology disciplines. The limited guidelines in pediatric cardio-oncology have motivated us to develop risk-stratification systems to institute surveillance and therapeutic support for this patient population. Here, we describe a collaborative approach to provide wide-ranging cardiovascular care to children and young adults with oncology diseases. Promoting collaboration in pediatric cardio-oncology medicine will ultimately provide excellent quality of care for future generations of patients.

The outcomes of pediatric acute lymphoblastic leukemia (ALL) have improved remarkably during the last five decades. Such improvements were made possible by the incorporation of new diagnostic technologies, the effective administration of conventional chemotherapeutic agents, and the provision of better supportive care. With the 5-year survival rates now exceeding 90% in high-income countries, the goal for the next decade is to improve survival further toward 100% and to minimize treatment-related adverse effects. Based on genome-wide analyses, especially RNA-sequencing analyses, ALL can be classified into more than 20 B-lineage subtypes and more than 10 T-lineage subtypes with prognostic and therapeutic implications. Response to treatment is another critical prognostic factor, and detailed analysis of minimal residual disease can detect levels as low as one ALL cell among 1 million total cells. Such detailed analysis can facilitate the rational use of molecular targeted therapy and immunotherapy, which have emerged as new treatment strategies that can replace or reduce the use of conventional chemotherapy.

T-cell malignancies expressing the γδ T-cell receptor (TCR) are often associated with poor prognosis. Here, we determined the clinical outcome of pediatric patients with T-cell acute lymphoblastic leukemia (T-ALL) expressing the γδ TCR. Of 100 newly diagnosed T-ALL patients, 93 had γδ TCR analysis performed at diagnosis. Repertoire was evaluated by paired sequencing of the rearranged TCR. All patients received intensified chemotherapy and those with minimal residual disease (MRD) ≥ 1% on day 42–46 became candidates for hematopoietic cell transplantation. Of the 93 T-ALL patients, 12 (13%) had γδ T-ALL and 11 (12%) had early T-cell precursor (ETP) ALL. Compared to the remaining 70 T-ALL patients, the γδ T-ALL patients were more likely to have MRD ≥ 1% on day 15–19 (67% vs. 33%, P = 0.03) and day 42–49 (33% vs. 7%; P = 0.007) of remission induction. The 10-year overall survival for γδ T-ALL patients (66.7% ± 22.2%) were lower than that of T-ALL patients (93.3% ± 7.3%, P = 0.001). TCR analysis demonstrated a conserved clonotype. In conclusion, the data suggest that children with γδ T-ALL may have a poor response to remission induction, based on MRD levels and decreased survival than the other T-ALL patients, despite receiving risk-directed therapy.

Genomic landscapes of 92 adult and 111 pediatric patients with B-cell acute lymphoblastic leukemia (B-ALL) were investigated using next-generation sequencing and copy number alteration analysis. Recurrent gene mutations and fusions were tested in an additional 87 adult and 93 pediatric patients. Among the 29 newly identified in-frame gene fusions, those involving MEF2D and ZNF384 were clinically relevant and were demonstrated to perturb B-cell differentiation, with EP300-ZNF384 inducing leukemia in mice. Eight gene expression subgroups associated with characteristic genetic abnormalities were identified, including leukemia with MEF2D and ZNF384 fusions in two distinct clusters. In subgroup G4 which was characterized by ERG deletion, DUX4-IGH fusion was detected in most cases. This comprehensive dataset allowed us to compare the features of molecular pathogenesis between adult and pediatric B-ALL and to identify signatures possibly related to the inferior outcome of adults to that of children. We found that, besides the known discrepancies in frequencies of prognostic markers, adult patients had more cooperative mutations and greater enrichment for alterations of epigenetic modifiers and genes linked to B-cell development, suggesting difference in the target cells of transformation between adult and pediatric patients and may explain in part the disparity in their responses to treatment.

A risk variant located at 9p21.3 is associated with cancer risk in pediatric B-cell precursor acute lymphoblastic leukaemia. Here, the authors show that this variant affects the gene expression of the tumour suppressor gene Cdkn2b.

MicroRNAs are important regulators of gene expression, acting primarily by binding to sequence-specific locations on already transcribed messenger RNAs (mRNA) and typically down-regulating their stability or translation. Recent studies indicate that microRNAs may also play a role in up-regulating mRNA transcription levels, although a definitive mechanism has not been established. Double-helical DNA is capable of forming triple-helical structures through Hoogsteen and reverse Hoogsteen interactions in the major groove of the duplex, and we show physical evidence (i.e., NMR, FRET, SPR) that purine or pyrimidine-rich microRNAs of appropriate length and sequence form triple-helical structures with purine-rich sequences of duplex DNA, and identify microRNA sequences that favor triplex formation. We developed an algorithm (Trident) to search genome-wide for potential triplex-forming sites and show that several mammalian and non-mammalian genomes are enriched for strong microRNA triplex binding sites. We show that those genes containing sequences favoring microRNA triplex formation are markedly enriched (3.3 fold, p

Recent progress in risk-adapted treatment for childhood acute lymphoblastic leukemia has secured 5-year event-free survival rates of approximately 80% and 5-year survival rates approaching 90%. With improved systemic and intrathecal chemotherapy, it is now feasible to omit safely in all patients prophylactic cranial irradiation, which was once a standard treatment. As high-resolution, genome-wide analyses of leukemic and normal host cells continue to identify novel subtypes of lymphoblastic leukemia and provide new insights into leukemogenesis, we can look forward to the time when all cases of this disease will be classified according to specific genetic abnormalities, some of which will yield “druggable” targets for more effective and less toxic treatments. Meanwhile, it is sobering to consider that a significant fraction of leukemia survivors will develop serious health problems within 30 years of their initial diagnosis. This underlines the need to introduce early countermeasures to reduce late therapy-related effects. The ultimate challenge is to gain a clear understanding of the factors that give rise to childhood leukemia in the first place, and enable preventive strategies to be devised and implemented.

Somatic mutations affecting ETV6 often occur in acute lymphoblastic leukemia (ALL), the most common childhood malignancy. The genetic factors that predispose to ALL remain poorly understood. Here we identify a novel germline ETV6 p. L349P mutation in a kindred affected by thrombocytopenia and ALL. A second ETV6 p. N385fs mutation was identified in an unrelated kindred characterized by thrombocytopenia, ALL and secondary myelodysplasia/acute myeloid leukemia. Leukemic cells from the proband in the second kindred showed deletion of wild type ETV6 with retention of the ETV6 p. N385fs. Enforced expression of the ETV6 mutants revealed normal transcript and protein levels, but impaired nuclear localization. Accordingly, these mutants exhibited significantly reduced ability to regulate the transcription of ETV6 target genes. Our findings highlight a novel role for ETV6 in leukemia predisposition.

Osteonecrosis is one of the most common, serious, toxicities resulting from the treatment of acute lymphoblastic leukemia. In recent years, pediatric acute lymphoblastic leukemia clinical trials have used discontinuous rather than continuous dosing of dexamethasone in an effort to reduce the incidence of osteonecrosis. However, it is not known whether discontinuous dosing would compromise antileukemic efficacy of glucocorticoids. Therefore, we tested the efficacy of discontinuous dexamethasone against continuous dexamethasone in murine models bearing human acute lymphoblastic leukemia xenografts (n = 8 patient samples) or murine BCR-ABL+ acute lymphoblastic leukemia. Plasma dexamethasone concentrations (7.9 to 212 nM) were similar to those achieved in children with acute lymphoblastic leukemia using conventional dosages. The median leukemia-free survival ranged from 16 to 59 days; dexamethasone prolonged survival from a median of 4 to 129 days in all seven dexamethasone-sensitive acute lymphoblastic leukemias. In the majority of cases (7 of 8 xenografts and the murine BCR-ABL model) we demonstrated equal efficacy of the two dexamethasone dosing regimens; whereas for one acute lymphoblastic leukemia sample, the discontinuous regimen yielded inferior antileukemic efficacy (log-rank p = 0.002). Our results support the clinical practice of using discontinuous rather than continuous dexamethasone dosing in patients with acute lymphoblastic leukemia.

Background Long-term central venous catheters have improved the quality of care for patients with chronic illnesses, but are complicated by obstructions which can result in delay of treatment or catheter removal.Design and Methods This paper reviews thrombolytic treatment for catheter obstruction. Literature from Medline searches using the terms “central venous catheter”, “central venous access device” OR “central venous line” associated with the terms “obstruction”, “occlusion” OR “thrombolytic” was reviewed. Efficacy of thrombolytic therapy, central venous catheter clearance rates and time to clearance were assessed.Results Alteplase, one of the current therapies, clears 52% of obstructed catheters within 30 min with 86% overall clearance (after 2 doses, when necessary). However, newer medications may have higher efficacy or shorter time to clearance. Reteplase cleared 67–74% within 30–40 min and 95% of catheters overall. Occlusions were resolved in 70 and 83% of patients with one and 2 doses of tenecteplase, respectively. Recombinant urokinase cleared 60% of catheters at 30 min and 73% overall. Alfimeprase demonstrated rapid catheter clearance with resolution in 40% of subjects within 5 min, 60% within 30 min, and 80% within 2 h. Additionally, urokinase prophylaxis decreased the incidence of catheter occlusions from 16–68% in the control group to 4–23% in the treatment group; in some studies, rates of catheter infections were also decreased in the urokinase group.Conclusions Thrombolytic agents successfully clear central venous catheter occlusions in most cases. Newer agents may act more rapidly and effectively than currently utilized therapies, but randomized studies with direct comparisons of these agents are needed to determine optimal management for catheter obstruction.

Elevated homocysteine concentrations have been associated with methotrexate-induced neurotoxicity. Based on methotrexate and homocysteine plasma concentrations of 494 children with acute lymphoblastic leukemia treated with high-dose methotrexate in the TOTAL XV study, a pharmacokinetic/pharmacodynamic (PK/PD) model was built with NONMEM. Several compartment and indirect response models were investigated. The pharmacokinetic disposition of methotrexate was best described by a two-compartment model. Homocysteine concentrations were included by an indirect response model where methotrexate inhibition of the homocysteine elimination rate was described by an E(max) model. The homocysteine baseline level was found to be age-dependent. Simulations revealed that folinate rescue therapy does not affect peak concentrations of homocysteine but leads to a modestly reduced homocysteine exposure. In conclusion, our PK/PD model describes the increase of methotrexate-induced HCY concentrations with satisfactory precision and can be applied to assess the effect of folinate regimens on the HCY concentration-time course.

Methotrexate (MTX) is widely used for the treatment of childhood acute lymphoblastic leukemia (ALL). The accumulation of MTX and its active metabolites, methotrexate polyglutamates (MTXPG), in ALL cells is an important determinant of its antileukemic effects. We studied 194 of 356 patients enrolled on St. Jude Total XV protocol for newly diagnosed ALL with the goal of characterizing the intracellular pharmacokinetics of MTXPG in leukemia cells; relating these pharmacokinetics to ALL lineage, ploidy and molecular subtype; and using a folate pathway model to simulate optimal treatment strategies. Serial MTX concentrations were measured in plasma and intracellular MTXPG concentrations were measured in circulating leukemia cells. A pharmacokinetic model was developed which accounted for the plasma disposition of MTX along with the transport and metabolism of MTXPG. In addition, a folate pathway model was adapted to simulate the effects of treatment strategies on the inhibition of de novo purine synthesis (DNPS). The intracellular MTXPG pharmacokinetic model parameters differed significantly by lineage, ploidy, and molecular subtypes of ALL. Folylpolyglutamate synthetase (FPGS) activity was higher in B vs T lineage ALL (p

The degree to which gene expression covaries between different primary tissues within an individual is not well defined. We hypothesized that expression that is concordant across tissues is more likely influenced by genetic variability than gene expression which is discordant between tissues. We quantified expression of 11,873 genes in paired samples of primary leukemia cells and normal leukocytes from 92 patients with acute lymphoblastic leukemia (ALL). Genetic variation at >500,000 single nucleotide polymorphisms (SNPs) was also assessed. The expression of only 176/11,783 (1.5%) genes was correlated (p

Childhood acute lymphoblastic leukemia (ALL) is the most common cancer in children, and can now be cured in approximately 80% of patients. Nevertheless, drug resistance is the major cause of treatment failure in children with ALL. The drug methotrexate (MTX), which is widely used to treat many human cancers, is used in essentially all treatment protocols worldwide for newly diagnosed ALL. Although MTX has been extensively studied for many years, relatively little is known about mechanisms of de novo resistance in primary cancer cells, including leukemia cells. This lack of knowledge is due in part to the fact that existing in vitro methods are not sufficiently reliable to permit assessment of MTX resistance in primary ALL cells. Therefore, we measured the in vivo antileukemic effects of MTX and identified genes whose expression differed significantly in patients with a good versus poor response to MTX.We utilized measures of decreased circulating leukemia cells of 293 newly diagnosed children after initial "up-front" in vivo MTX treatment (1 g/m(2)) to elucidate interpatient differences in the antileukemic effects of MTX. To identify genomic determinants of these effects, we performed a genome-wide assessment of gene expression in primary ALL cells from 161 of these newly diagnosed children (1-18 y). We identified 48 genes and two cDNA clones whose expression was significantly related to the reduction of circulating leukemia cells after initial in vivo treatment with MTX. This finding was validated in an independent cohort of children with ALL. Furthermore, this measure of initial MTX in vivo response and the associated gene expression pattern were predictive of long-term disease-free survival (p < 0.001, p = 0.02).Together, these data provide new insights into the genomic basis of MTX resistance and interpatient differences in MTX response, pointing to new strategies to overcome MTX resistance in childhood ALL.Total XV, Therapy for Newly Diagnosed Patients With Acute Lymphoblastic Leukemia, http://www.ClinicalTrials.gov (NCT00137111); Total XIIIBH, Phase III Randomized Study of Antimetabolite-Based Induction plus High-Dose MTX Consolidation for Newly Diagnosed Pediatric Acute Lymphocytic Leukemia at Intermediate or High Risk of Treatment Failure (NCI-T93-0101D); Total XIIIBL, Phase III Randomized Study of Antimetabolite-Based Induction plus High-Dose MTX Consolidation for Newly Diagnosed Pediatric Acute Lymphocytic Leukemia at Lower Risk of Treatment Failure (NCI-T93-0103D).