Perspectives of genetic counseling supervisors regarding genetic counseling students' attainment of practice-based competencies in clinical care through remote supervision.

There are limited studies regarding the attainment of the Accreditation Council for Genetic Counseling Practice-Based Competencies by genetic counseling students who complete clinical rotations in an in-person setting versus in a remote setting that incudes telephone and/or video patient encounters. This study explored the perceptions of 17 patient-facing genetic counselors who had served as supervisors for genetic counseling students regarding student attainment of practice-based competencies in in-person compared to remote rotations. Participants were recruited through an American Board of Genetic Counseling eblast and were required to have at least 2 years of clinical experience and experience providing genetic counseling supervision for at least one in-person rotation and one remote rotation. Four focus groups were created comprising genetic counselors from various practice disciplines. Discussion focused on potential differences and similarities in supervisor perceptions of student attainment of each clinical practice-based competency, and whether there were any concerns about students being able to attain each competency in remote rotations. Overall, participants discussed that genetic counseling students' attainment of clinical competencies through remote rotations was comparable to in-person rotations; however, 15 themes were identified illustrating differences reported by participants in how they observed these skills being performed by students in in-person versus remote clinical settings. The findings of this study highlight important considerations when developing a remote rotation, as well as ways in which certain clinical skills may be further enhanced through a combination of both in-person and remote clinical experiences. A noted limitation of remote rotations is that students have less of an opportunity to interact with other providers, and so may require other opportunities for interprofessionalism and to understand their role as part of a larger organization. Further study is required to elucidate differences between telephone and video clinics, as well as potential differences pertaining to various specialty areas of practice.

Using Long-Term Follow-Up Data to Classify Genetic Variants in Newborn Screened Conditions.

With the rapid increase in publicly available sequencing data, healthcare professionals are tasked with understanding how genetic variation informs diagnosis and affects patient health outcomes. Understanding the impact of a genetic variant in disease could be used to predict susceptibility/protection and to help build a personalized medicine profile. In the United States, over 3.8 million newborns are screened for several rare genetic diseases each year, and the follow-up testing of screen-positive newborns often involves sequencing and the identification of variants. This presents the opportunity to use longitudinal health information from these newborns to inform the impact of variants identified in the course of diagnosis. To test this, we performed secondary analysis of a 10-year natural history study of individuals diagnosed with metabolic disorders included in newborn screening (NBS). We found 564 genetic variants with accompanying phenotypic data and identified that 161 of the 564 variants (29%) were not included in ClinVar. We were able to classify 139 of the 161 variants (86%) as pathogenic or likely pathogenic. This work demonstrates that secondary analysis of longitudinal data collected as part of NBS finds unreported genetic variants and the accompanying clinical information can inform the relationship between genotype and phenotype.

Outcomes and genotype correlations in patients with mitochondrial trifunctional protein or isolated long chain 3-hydroxyacyl-CoA dehydrogenase deficiency enrolled in the IBEM-IS database.

Purpose: Mitochondrial trifunctional protein deficiency (TFPD) and isolated long chain 3-hydroxyacyl-CoA dehydrogenase deficiency (LCHADD) are two related defects of fatty acid ß -oxidation. While NBS has decreased mortality, morbidity remains significant. Additionally, the relationship of genotype to clinical outcome remains unclear. To better understand these issues, we collected natural history data for these conditions by reviewing seven years of retrospective data from 45 cases of TFPD or LCHADD in the Inborn Errors of Metabolism - Information System. Methods: Available data included age at database entry, last datapoint, and development of various complications. Data were analyzed by clinical assigned diagnosis (LCHADD or TFPD), subdivided by method of ascertainment (newborn screening-NBS, or other than by newborn screening-NNBS), then re-analyzed based on four genotype groups: homozygous c.1528GC (p.E510Q) (common LCHAD variant); heterozygous c.1528GC (p.E510Q), other HADHA variants; and HADHB variants. Results: Forty-five patients from birth to 34 years of age were analyzed by assigned diagnosis (30 LCHADD and 15 TFPD) and method of ascertainment. Thirty had further analysis by genotype (22 biallelic HADHA variants and 8 biallelic HADHB variants). With regards to maternal complications, retinopathy, cardiomyopathy and hypoglycemia, patients with biallelic HADHA variants (with or without the common LCHAD variant) manifest a traditional LCHADD phenotype, while those with HADHB gene variants more commonly reported neuromusculoskeletal type TFPD phenotype. While retinopathy, rhabdomyolysis and peripheral neuropathy tended to present later in childhood, many features including initial report of cardiomyopathy and hypoglycemia presented across a wide age spectrum. Conclusion: This study demonstrates the utility of genotypic confirmation of patients identified with LCHADD/TFPD as variants in the HADHA and HADHB genes lead to different symptom profiles. In our data, biallelic HAHDA variants conferred a LCHADD phenotype, regardless of the presence of the common LCHAD variant.

The 2019 US medical genetics workforce: a focus on clinical genetics.

PURPOSE: This study characterizes the US clinical genetics workforce to inform workforce planning and public policy development. METHODS: A 32-question survey was electronically distributed to American Board of Medical Genetics and Genomics board-certified/eligible diplomates in 2019. We conducted a descriptive analysis of responses from practicing clinical geneticists. RESULTS: Of the 491 clinical geneticists responding to the survey, a majority were female (59%) and White (79%), worked in academic medical centers (73%), and many engaged in telemedicine (33%). Clinical geneticists reported an average of 13 new and 10 follow-up patient visits per week. The average work week was 50 hours and the majority (58%) worked over half-time in clinical duties. Providers indicated that 39% of new emergency patients wait 3 days or more, and 39% of nonemergency patients wait over 3 months to be seen. Respondents were geographically concentrated in metropolitan areas and many reported unfilled clinical geneticist job vacancies at their institution of more than 3 years. CONCLUSION: With the rapid expansion of genomic medicine in the past decade, there is still a gap between genetics services needed and workforce capacity. A concerted effort is required to increase the number of clinical geneticists and enhance interdisciplinary teamwork to meet increasing patient needs.

An Exploration of Genetic Test Utilization, Genetic Counseling, and Consanguinity within the Inborn Errors of Metabolism Collaborative (IBEMC).

The Inborn Errors of Metabolism Collaborative (IBEMC) includes clinicians from 29 institutions collecting data to enhance understanding of metabolic conditions diagnosable by newborn screening. Data collected includes hospitalizations, test results, services, and long-term outcomes. Through evaluation of this data, we sought to determine how frequently genetic counseling had been provided, how often genetic testing was performed, and also determine the consanguinity rate in this population. A data query was performed with the following elements abstracted/analyzed: current age, metabolic condition, whether genetic counseling was provided (and by whom), whether genetic testing was performed, and consanguinity. Genetic counseling was provided to families 95.8% of the time and in 68.6% of cases by a genetic counselor. Genetic testing was performed on 68.0% of subjects, with usage highest for fatty-acid-oxidation disorders (85.1%). The rate of consanguinity was 2.38%. Within this large national collaborative there is a high frequency of genetic counseling, though in one-third of cases a genetic counselor has not been involved. Additionally, while metabolic conditions have historically been diagnosed biochemically, there is currently high utilization of molecular testing suggesting DNA testing is being incorporated into diagnostic assessments - especially for fatty-acid-oxidation disorders where the underlying genotype helps predict clinical presentation.

Comparison of Methods of Initial Ascertainment in 58 Cases of Propionic Acidemia Enrolled in the Inborn Errors of Metabolism Information System Reveals Significant Differences in Time to Evaluation and Symptoms at Presentation.

OBJECTIVES: To compare time to evaluation and symptoms at diagnosis of propionic acidemia (PA) by method of ascertainment, and to explore correlations between genotype and biochemical variables. STUDY DESIGN: Clinical symptoms, genotype, and biochemical findings were analyzed retrospectively in 58 individuals with PA enrolled in the Inborn Errors of Metabolism Information System (IBEM-IS) based on the type of initial ascertainment: abnormal newborn screening (NBS), clinical presentation (symptomatic), or family history. RESULTS: The average age at initial evaluation and treatment was significantly younger in patients ascertained via abnormal NBS compared with those referred for clinical symptoms. Furthermore, the majority of individuals ascertained because of abnormal NBS were asymptomatic at diagnosis, compared with a minority of clinical presentations. A notable difference in the frequency of metabolic acidosis at initial presentation was observed between those with abnormal NBS (12.5%; 2 of 16) and those with an abnormal clinical presentation (79%; 19 of 24). The frequency of hyperammonemia was similar in the 2 groups. CONCLUSION: Our data support the continued value of NBS to identify individuals with PA, who are diagnosed and treated earlier than for other modes of ascertainment. There were no statistically significant correlations between genotype and NBS for C3 acylcarnitines. Although expanded use of NBS has allowed for early diagnosis and treatment, long-term outcomes of individuals with PA, especially with respect to mode of ascertainment, remain unclear and would benefit from a longitudinal study.

221 newborn-screened neonates with medium-chain acyl-coenzyme A dehydrogenase deficiency: Findings from the Inborn Errors of Metabolism Collaborative.

INTRODUCTION: There is limited understanding of relationships between genotype, phenotype and other conditions contributing to health in neonates with medium-chain acyl-coenzyme A dehydrogenase deficiency (MCADD) identified through newborn screening. METHODS: Retrospective analysis of comprehensive data from a cohort of 221 newborn-screened subjects identified as affected with MCADD in the Inborn Errors of Metabolism - Information System (IBEM-IS), a long term follow-up database of the Inborn Errors of Metabolism Collaborative, was performed. RESULTS: The average age at notification of first newborn screen results to primary care or metabolic providers was 7.45days. The average octanoylcarnitine (C8) value on first newborn screen was 11.2µmol/L (median 8.6, range 0.36-43.91). A higher C8 level correlated with an earlier first subspecialty visit. Subjects with low birth weight had significantly lower C8 values. Significantly higher C8 values were found in symptomatic newborns, in newborns with abnormal lab testing in addition to newborn screening and/or diagnostic tests, and in subjects homozygous for the c.985A>G ACADM gene mutation or compound heterozygous for the c.985A>G mutation and deletions or other known highly deleterious mutations. Subjects with neonatal symptoms, or neonatal abnormal labs, or neonatal triggers were more likely to have at least one copy of the severe c.985A>G ACADM gene mutation. C8 and genotype category were significant predictors of the likelihood of having neonatal symptoms. Neonates with select triggers were more likely to have symptoms and laboratory abnormalities. CONCLUSIONS: This collaborative study is the first in the United States to describe health associations of a large cohort of newborn-screened neonates identified as affected with MCADD. The IBEM-IS has utility as a platform to better understand the characteristics of individuals with newborn-screened conditions and their follow-up interactions with the health system.

Outcomes and genotype-phenotype correlations in 52 individuals with VLCAD deficiency diagnosed by NBS and enrolled in the IBEM-IS database.

Very long chain acyl-CoA dehydrogenase (VLCAD) deficiency can present at various ages from the neonatal period to adulthood, and poses the greatest risk of complications during intercurrent illness or after prolonged fasting. Early diagnosis, treatment, and surveillance can reduce mortality; hence, the disorder is included in the newborn Recommended Uniform Screening Panel (RUSP) in the United States. The Inborn Errors of Metabolism Information System (IBEM-IS) was established in 2007 to collect longitudinal information on individuals with inborn errors of metabolism included in newborn screening (NBS) programs, including VLCAD deficiency. We retrospectively analyzed early outcomes for individuals who were diagnosed with VLCAD deficiency by NBS and describe initial presentations, diagnosis, clinical outcomes and treatment in a cohort of 52 individuals ages 1-18years. Maternal prenatal symptoms were not reported, and most newborns remained asymptomatic. Cardiomyopathy was uncommon in the cohort, diagnosed in 2/52 cases. Elevations in creatine kinase were a common finding, and usually first occurred during the toddler period (1-3years of age). Diagnostic evaluations required several testing modalities, most commonly plasma acylcarnitine profiles and molecular testing. Functional testing, including fibroblast acylcarnitine profiling and white blood cell or fibroblast enzyme assay, is a useful diagnostic adjunct if uncharacterized mutations are identified.

Inborn Errors of Metabolism Collaborative: large-scale collection of data on long-term follow-up for newborn-screened conditions.

PURPOSE: The Inborn Errors of Metabolism Information System (IBEM-IS) collects data on the clinical history of inborn errors of metabolism (IBEMs). The IBEM-IS is accessible to metabolic clinics nationwide and seeks to (i) influence clinical management of affected individuals and (ii) provide information to support public health decision making. METHODS: Thirty centers in 21 states are enrolling persons with newborn-screened conditions, collecting information on diagnosis and treatment at the time of enrollment and all subsequent visits. Prospective data are collected using electronic capture forms allowing aggregation of information regarding outcomes for individuals affected with IBEMs. RESULTS: A total of 1,893 subjects have been enrolled in the IBEM-IS, and more than 540,000 individual data points have been collected. Data collection has been initiated for subjects with 41 of 46 conditions on the recommended uniform screening panel; 4 conditions have more than 100 subjects enrolled. Median follow-up time for subjects with more than one visit (n = 898) is 1.5 years (interquartile range = 2.2 years). Subjects with critical conditions are more likely to have emergency letters and sick-day plans. Mortality was exclusive to children with critical conditions. CONCLUSION: Large-scale prospective data can be collected for individuals with rare conditions, permitting enhanced decision making for clinical management and supporting decision making in public health newborn screening programs.Genet Med 18 12, 1276-1281.

Outcomes of cases with 3-methylcrotonyl-CoA carboxylase (3-MCC) deficiency - Report from the Inborn Errors of Metabolism Information System.

INTRODUCTION: 3-Methyl crotonyl CoA carboxylase (3MCC) deficiency is an inborn error of leucine metabolism whose detection was increased with the advent of expanded newborn screening. While most NBS-identified infants appear clinically normal, prior studies suggest a possible increased risk for developmental or metabolic abnormalities. As yet, no predictive markers are known that can identify children at risk for biochemical or developmental abnormalities. METHOD: All available 3-MCC cases diagnosed by newborn screening in the Inborn Errors of Metabolism Information System (IBEM-IS) were reviewed for markers that might be predictive of outcome. RESULTS: A limited number of cases were identified with traditional biochemical symptoms including acidosis, hyperammonemia or lactic acidosis, and 15% of those with available developmental information had recorded developmental disabilities not clearly attributable to other causes. There was no correlation between newborn screening (NBS) C5OH level and presence of metabolic, newborn, later-life or developmental abnormalities in these cases. DISCUSSION: This sample, obtained from the IBEM-IS database, attempts to avoid some of the ascertainment bias present in retrospective studies. An increase in developmental abnormalities and in traditionally described metabolic symptoms remains apparent, although no specific biochemical markers appear predictive of outcome. The role that prevention of fasting plays in outcome cannot be ascertained. These data suggest that C5OH level found on newborn screening by itself is not sufficient for diagnostic or predictive purposes.

Homozygous loss of mouse tetraspanin CD82 enhances integrin αIIbß3 expression and clot retraction in platelets.

Integrin αIIbß3 is critical for platelet-mediated blood clotting. Tetraspanins are well-established regulators of integrins and genetic loss of tetraspanin CD151 or TSSC6 in mice leads to increased bleeding due to inadequate integrin αIIbß3 outside-in signaling. Conversely, mild but enhanced integrin αIIbß3 activation and hyperaggregation is observed in CD9 and CD63 null mice respectively. CD82 is reportedly expressed in platelets; however its function is unknown. Using genetically engineered CD82 null mice, we investigated the role of the tetraspanin CD82 in platelet activation. Loss of CD82 resulted in reduced bleed times in vivo. CD82 was present on the surface of both human and mouse platelets, and its levels did not change upon platelet activation or degranulation. No differences in platelet activation, degranulation, or aggregation in response to ADP or collagen were detected in CD82 null mice. However, the kinetics of clot retraction was enhanced, which was intrinsic to the CD82-null platelets. Integrin αIIbß3 surface expression was elevated on the platelets from CD82 null mice and they displayed enhanced adhesion and tyrosine kinase signaling on fibrinogen. This is the first report on CD82 function in platelets; which we found intrinsically modulates clot retraction, integrin αIIbß3 expression, cell adhesion, and tyrosine signaling.

Host thiopurine methyltransferase status affects mercaptopurine antileukemic effectiveness in a murine model.

BACKGROUND: Thiopurines are used for many cancers, including acute lymphoblastic leukemia (ALL). Patients with an inherited host defect in thiopurine methyltransferase (TPMT) are at high risk for life-threatening toxicity if treated with conventional dosages, but the impact on antileukemic efficacy is less clear. MATERIALS AND METHODS: We treated thiopurine-sensitive BCR-ABL+Arf-null Tpmt+/+ ALL in Tpmt+/+, +/-, or -/- recipient mice to test the impact of the host polymorphism on antileukemic efficacy. RESULTS: Median survival was similar in untreated mice of different Tpmt genotypes (16-18 days). However, in mice treated with low-dose mercaptopurine (such as tolerated by TPMT-/- patients), the difference in 30-day leukemia-free survival by Tpmt genotype was profound: 5% (±9%) for Tpmt+/+ mice, 47% (±26%) for Tpmt+/- mice, and 85% (±14%) for Tpmt-/- mice (P=5×10), indicating a substantial impact of host Tpmt status on thiopurine effectiveness. Among Tpmt+/+ recipient mice, leukemia-free survival improved with higher doses of mercaptopurine (similar to doses tolerated by wild-type patients) compared with lower doses, and at higher doses was comparable (P=0.6) to the survival of Tpmt-/- mice treated with the lower dose. CONCLUSIONS: These findings support the notion that germline polymorphisms in Tpmt affect not only host tissue toxicity but also antitumor effectiveness.

Transient induction of ING4 by Myc drives prostate epithelial cell differentiation and its disruption drives prostate tumorigenesis.

The mechanisms by which Myc overexpression or Pten loss promotes prostate cancer development are poorly understood. We identified the chromatin remodeling protein, ING4, as a crucial switch downstream of Myc and Pten that is required for human prostate epithelial differentiation. Myc-induced transient expression of ING4 is required for the differentiation of basal epithelial cells into luminal cells, while sustained ING4 expression induces apoptosis. ING4 expression is lost in >60% of human primary prostate tumors. ING4 or Pten loss prevents epithelial cell differentiation, which was necessary for tumorigenesis. Pten loss prevents differentiation by blocking ING4 expression, which is rescued by ING4 re-expression. Pten or ING4 loss generates tumor cells that co-express basal and luminal markers, indicating prostate oncogenesis occurs through disruption of an intermediate step in the prostate epithelial differentiation program. Thus, we identified a new epithelial cell differentiation switch involving Myc, Pten, and ING4, which when disrupted leads to prostate tumorigenesis. Myc overexpression and Pten loss are common genetic abnormalities in prostate cancer, whereas loss of the tumor suppressor ING4 has not been reported. This is the first demonstration that transient ING4 expression is absolutely required for epithelial differentiation, its expression is dependent on Myc and Pten, and it is lost in the majority of human prostate cancers. This is the first demonstration that loss of ING4, either directly or indirectly through loss of Pten, promotes Myc-driven oncogenesis by deregulating differentiation. The clinical implication is that Pten/ING4 negative and ING4-only negative tumors may reflect two distinct subtypes of prostate cancer.

Differential effects of targeted disruption of thiopurine methyltransferase on mercaptopurine and thioguanine pharmacodynamics.

The recessive deficiency in thiopurine methyltransferase (TPMT), caused by germ-line polymorphisms in TPMT, can cause severe toxicity after mercaptopurine. However, the significance of heterozygosity and the effect of the polymorphism on thioguanine or in the absence of thiopurines is not known. To address these issues, we created a murine knockout of Tpmt. Pharmacokinetic and pharmacodynamic studies of mercaptopurine and thioguanine were done in Tpmt(-/-), Tpmt(+/-), and Tpmt(+/+) mice and variables were compared among genotypes. Methylated thiopurine and thioguanine nucleotide metabolites differed among genotypes after treatment with mercaptopurine (P < 0.0001 and P = 0.044, respectively) and thioguanine (P = 0.011 and P = 0.002, respectively). Differences in toxicity among genotypes were more pronounced following treatment with 10 daily doses of mercaptopurine at 100 mg/kg/d (0%, 68%, and 100% 50-day survival; P = 0.0003) than with thioguanine at 5 mg/kg/d (0%, 33%, and 50% 15-day survival; P = 0.07) in the Tpmt(-/-), Tpmt(+/-), and Tpmt(+/+) genotypes, respectively. Myelosuppression and weight loss exhibited a haploinsufficient phenotype after mercaptopurine, whereas haploinsufficiency was less prominent with thioguanine. In the absence of drug challenge, there was no apparent phenotype. The murine model recapitulates many clinical features of the human polymorphism; indicates that mercaptopurine is more affected by the TPMT polymorphism than thioguanine; and provides a preclinical system for establishing safer regimens of genetically influenced antileukemic drug therapy.

Inhibition of integrin-mediated crosstalk with epidermal growth factor receptor/Erk or Src signaling pathways in autophagic prostate epithelial cells induces caspase-independent death.

In vivo in the prostate gland, basal epithelial cells adhere to laminin 5 (LM5) via alpha3beta1 and alpha6beta4 integrins. When placed in culture primary prostate basal epithelial cells secrete and adhere to their own LM5-rich matrix. Adhesion to LM5 is required for cell survival that is dependent on integrin-mediated, ligand-independent activation of the epidermal growth factor receptor (EGFR) and the cytoplasmic tyrosine kinase Src, but not PI-3K. Integrin-mediated adhesion via alpha3beta1, but not alpha6beta4 integrin, supports cell survival through EGFR by signaling downstream to Erk. PC3 cells, which do not activate EGFR or Erk on LM5-rich matrices, are not dependent on this pathway for survival. PC3 cells are dependent on PI-3K for survival and undergo caspase-dependent death when PI-3K is inhibited. The death induced by inhibition of EGFR or Src in normal primary prostate cells is not mediated through or dependent on caspase activation, but depends on the induction of reactive oxygen species. In addition the presence of an autophagic pathway, maintained by adhesion to matrix through alpha3beta1 and alpha6beta4, prevents the induction of caspases when EGFR or Src is inhibited. Suppression of autophagy is sufficient to induce caspase activation and apoptosis in LM5-adherent primary prostate epithelial cells.

Lymphoid gene expression as a predictor of risk of secondary brain tumors.

Gene expression profiles are tissue-specific but may also reflect germ-line-driven expression patterns across tissue types. Previously, using a targeted pharmacologic approach, we identified germ-line polymorphisms in a single gene (thiopurine methyltransferase) associated with the risk of irradiation- and chemotherapy-induced secondary brain tumors in children with acute lymphoblastic leukemia (ALL). To identify additional candidate genetic risk factors, in identically treated patients, we compared the gene expression profiles of diagnostic ALL blasts of those who did develop irradiation-associated brain tumors (n = 9) with the profiles from those who did not (n = 33). Weighted rank regression was used to identify 33 probe sets associated with the time-dependent development of brain tumors; k-means clustering (k = 2) identified 2 groups that differed significantly in cumulative incidence of brain tumors (P = 0.012). Permutation analysis was used to estimate the probability (P = 0.18) of obtaining 2 such clusters by chance. Linear discriminant analysis (time-independent categorization of outcome) was used to identify 70 probe sets whose expression differentiated between the 2 groups of patients. Permutation analyses (n = 1,000) was used to estimate the probability of selecting these probe sets by chance (P = 0.055). Five probe sets were in common between the time-independent and time-dependent methods. The distinguishing genes are involved in neural growth (FGFR1) and in nuclear trafficking (HNRPL, KPNB1). These data suggest that gene expression profiling from accessible tissues may identify targets involved in therapy-related malignancies in unrelated tissues.

Etoposide induces chimeric Mll gene fusions.

MLL gene fusions are the hallmark of more than 70% of therapy-related leukemias (t-ML) associated with topoisomerase II inhibitors (e.g., etoposide) and cause leukemia in murine transgenic models. To determine whether Mll genomic fusions can occur after exposure to topoisomerase II inhibitors, we developed a long-distance inverse PCR DNA-based assay for chimeric Mll fusions in mouse embryonic stem cells. We detected Mll fusions at a higher frequency following 100 microM etoposide for 8 h (16x10(-6) cell(-1)) than in no-drug controls (1.0x10(-6) cell(-1), P=0.0002) or after treatment with a comparably cytotoxic exposure to the antimicrotubule drug vincristine (1.0x10(-6) cell(-1), P=0.0047). The fusion points in Mll chimeric products induced by etoposide were localized to a 1.5 kb region between exons 9 and 11, analogous to the MLL breakpoint cluster region in human leukemia. All 49 Mll fusion partners analyzed matched known genomic murine sequences, with 40 (82%) matching annotated genes covering eighteen murine autosomes. One partner was Runx1, the murine homologue of the transcription factor AML-1, a target of human translocations in therapy-related leukemia. These findings indicate that etoposide triggers the formation of Mll gene fusions, a critical step for the development of treatment-induced leukemic transformation.

Pharmacokinetics and pharmacodynamics of oral etoposide in children with relapsed or refractory acute lymphoblastic leukemia.

PURPOSE: To study the pharmacokinetics and pharmacodynamics of once- versus twice-daily oral etoposide in children with relapsed or refractory acute lymphoblastic leukemia (ALL). PATIENTS AND METHODS: Fifty-eight patients were randomly assigned to etoposide at 50 mg/m(2)/d with once- versus twice-daily doses for 22 days. On day 8, vincristine, asparaginase, and dexamethasone were started. Etoposide pharmacokinetics and pharmacodynamics were studied for 47, 28, and 26 patients on day 1, 8, and 22, respectively, of remission reinduction therapy. RESULTS: Of 48 patients with pharmacokinetic data, 42 (87.5%) achieved complete remission, three (6.3%) failed to achieve remission, and three (6.3%) died during induction. Median etoposide day 8 area under concentration-time curve (AUC) and cumulative AUC tended to be greater (P =.06 and P =.07, respectively) in patients (n = 23) who achieved complete remission (24 and 522 micro mol/L x h, respectively) than in patients (n = 3) who did not (14 and 303 micro mol/L x h, respectively). Three of eight patients with plasma concentrations exceeding 1.7 micro M (1 micro g/mL) for more than 8 hours daily, compared with one of 20 patients with concentrations exceeding 1.7 micro M for

Genetic polymorphisms in CYP3A5, CYP3A4 and NQO1 in children who developed therapy-related myeloid malignancies.

Therapy-related acute myeloid leukemia and myelodysplastic syndrome (t-ML) are serious complications that affect some patients after acute lymphoblastic leukemia (ALL) treatment. Genetic polymorphisms in the promoter of CYP3A4 (CYP3A4*1B) and in NAD(P)H:quinone oxidoreductase (NQO1609C-->T substitution) have been associated with the risk of t-ML. A polymorphism in CYP3A5 (CYP3A5*3) affects CYP3A activity and the wild-type allele (CYP3A5*1) is in partial linkage with the CYP3A4*1B allele. We compared the genotype frequencies for the CYP3A5*3, the CYP3A4*1B and the NQO1609C-->T substitution in 224 children with ALL who did not develop t-ML (controls) and in 53 children with ALL who did develop the complication. The allele frequencies differed significantly among whites, blacks and Hispanics (P < 0.001 for CYP3A5*3, P < 0.001 for CYP3A4*1B and P = 0.004 for NQO1609), thus we performed the comparisons between ALL controls and t-ML patients after accounting for race. We found no differences in the CYP3A4*1B allele distribution between ALL controls and t-ML patients in whites (P = 0.339, 6.6% vs. 9.8%), blacks (P = 0.498, 93.8% vs. 87.5%) or Hispanics (P = 0.523, 39.1% vs. 25.0%). The frequencies for the NQO1609C-->T allele did not differ between control and t-ML groups in whites (P = 0.191, 35.0% vs. 44.9%), blacks (P = 0.664, 37.5% vs. 37.5%) or Hispanics (P = 0.447, 65.2% vs. 50.0%). We found no differences between the control and t-ML group in the incidence of homozygous CYP3A5*3 genotypes: 82.0% vs. 85.4% in whites (P = 0.403), 6.5% vs. 12.5% in blacks (P = 0.508), and 69.6% vs. 75.0% in Hispanics (P= 0.663). Our data do not support an association between common CYP3A4, NQO1 or CYP3A5 polymorphisms and the risk of t-ML in children treated for ALL.