Mehmet Burcu

Pim-1 Kinase Protects P-Glycoprotein from Degradation and Enables Its Glycosylation and Cell Surface Expression

The oncogenic serine/threonine kinase Pim-1 phosphorylates and activates the ATP-binding cassette transporter breast cancer resistance protein (ABCG2). The ABC transporter P-glycoprotein (Pgp; ABCB1) also contains a Pim-1 phosphorylation consensus sequence, and we hypothesized that Pim-1 also regulates Pgp. Pgp is exported from the endoplasmic reticulum (ER) as a 150-kDa species that is glycosylated to 170-kDa Pgp, translocates to the cell surface, and mediates drug efflux; alternatively, 150-kDa Pgp is cleaved to a 130-kDa proteolytic product by ER proteases or undergoes ubiquitination and proteasomal degradation. Pim-1 and Pgp interaction was studied in GST pull-down and phosphorylation in in vitro kinase assays. Pim-1 knockdown and inhibition effects on Pgp expression were studied by immunoblotting and flow cytometry and on Pgp stability by immunoblotting after cycloheximide treatment. Pim-1 directly interacted with and phosphorylated Pgp in intact cells and in vitro. Pim-1 knockdown or inhibition decreased cellular and cell surface 170-kDa Pgp, in association with both transient increase in 130-kDa Pgp and increased Pgp ubiquitination and proteasomal degradation. Pim-1 inhibition also decreased expression of 150-kDa Pgp in the presence of the glycosylation inhibitor 2-deoxy-d-glucose. Finally, Pim-1 inhibition sensitized Pgp-overexpressing cells to doxorubicin. Thus, Pim-1 regulates Pgp expression by protecting 150-kDa Pgp from proteolytic and proteasomal degradation and enabling Pgp glycosylation and cell surface translocation and thus Pgp-mediated drug efflux. Pim-1 inhibitors are entering clinical trials and may provide a novel approach to abrogating drug resistance.

Trends and patterns of antidepressant use in children and adolescents from five western countries, 2005-2012

Following the FDA black box warning in 2004, substantial reductions in antidepressant (ATD) use were observed within 2 years in children and adolescents in several countries. However, whether these reductions were sustained is not known. The objective of this study was to assess more recent trends in ATD use in youth (0-19 years) for the calendar years 2005/6-2012 using data extracted from regional or national databases of Denmark, Germany, the Netherlands, the United Kingdom (UK), and the United States (US). In a repeated cross-sectional design, the annual prevalence of ATD use was calculated and stratified by age, sex, and according to subclass and specific drug. Across the years, the prevalence of ATD use increased from 1.3% to 1.6% in the US data (+26.1%); 0.7% to 1.1% in the UK data (+54.4%); 0.6% to 1.0% in Denmark data (+60.5%); 0.5% to 0.6% in the Netherlands data (+17.6%); and 0.3% to 0.5% in Germany data (+49.2%). The relative growth was greatest for 15-19 year olds in Denmark, Germany and UK cohorts, and for 10-14 year olds in Netherlands and US cohorts. While SSRIs were the most commonly used ATDs, particularly in Denmark (81.8% of all ATDs), Germany and the UK still displayed notable proportions of tricyclic antidepressant use (23.0% and 19.5%, respectively). Despite the sudden decline in ATD use in the wake of government warnings, this trend did not persist, and by contrast, in recent years, ATD use in children and adolescents has increased substantially in youth cohorts from five Western countries.

Pim-1 Kinase Phosphorylates and Stabilizes 130 kDa FLT3 and Promotes Aberrant STAT5 Signaling in Acute Myeloid Leukemia with FLT3 Internal Tandem Duplication

The type III receptor tyrosine kinase fms-like tyrosine kinase 3 (FLT3) is expressed on both normal hematopoietic stem cells and acute myeloid leukemia (AML) cells and regulates their proliferation. Internal tandem duplication (ITD) mutation of FLT3 is present in a third of AML cases, results in constitutive activation and aberrant signaling of FLT3, and is associated with adverse treatment outcomes. While wild-type (WT) FLT3 is predominantly a 150 kDa complex glycosylated cell surface protein, FLT3-ITD is partially retained in the endoplasmic reticulum as a 130 kDa underglycosylated species associated with the chaperones calnexin and heat shock protein (HSP) 90, and mediates aberrant STAT5 signaling, which upregulates the oncogenic serine/threonine kinase Pim-1. FLT3 contains a Pim-1 substrate consensus serine phosphorylation site, and we hypothesized that it might be a Pim-1 substrate. Pim-1 was indeed found to directly interact with and serine-phosphorylate FLT3. Pim-1 inhibition decreased the expression and half-life of 130 kDa FLT3, with partial abrogation by proteasome inhibition, in association with decreased FLT3 binding to calnexin and HSP90, and increased 150 kDa FLT3 expression and half-life, with abrogation by inhibition of glycosylation. These findings were consistent with Pim-1 stabilizing FLT3-ITD as a 130 kDa species associated with calnexin and HSP90 and inhibiting its glycosylation to form the 150 kDa species. Pim-1 knockdown effects were similar. Pim-1 inhibition also decreased phosphorylation of FLT3 at tyrosine 591 and of STAT5, and expression of Pim-1 itself, consistent with inhibition of the FLT3-ITD-STAT5 signaling pathway. Finally, Pim-1 inhibition synergized with FLT3 inhibition in inducing apoptosis of FLT3-ITD cells. This is, to our knowledge, the first demonstration of a role of Pim-1 in a positive feedback loop promoting aberrant signaling in malignant cells.

Atypical Antipsychotic Use Among Medicaid-Insured Children and Adolescents: Duration, Safety, and Monitoring Implications

OBJECTIVE Over the last two decades, the increased use of atypical antipsychotic medications, often for unlabeled indications including attention-deficit/hyperactivity disorder (ADHD), has been profound. This study aims to characterize duration of atypical antipsychotic use by age group and Medicaid eligibility category, and among youth with noncomorbid ADHD. METHODS Administrative data on 266,590 youth 2-17 years of age, and continuously enrolled in a mid-Atlantic state Medicaid program in 2006, were assessed in terms of median days of atypical antipsychotic use using bivariate analyses and multivariable quantile regression. Also, in a subanalysis of youth diagnosed with ADHD without any reported psychiatric comorbidities (i.e., noncomorbid ADHD), age-specific adjusted odds and adjusted median days of atypical antipsychotic use by Medicaid eligibility category were assessed. Additionally, patterns of use of single atypical antipsychotic regimens and two concomitant atypical antipsychotic regimens were described. RESULTS Overall, the median annual duration of atypical antipsychotic use was 180 days (interquartile range: 69-298 days). Children (2-12-year-olds) had longer durations of use than did adolescents (13-17-year-olds) (median 192 vs. 179 days), respectively. In the absence of any comorbid psychiatric diagnosis, ADHD-diagnosed foster care youth had more than threefold greater adjusted odds of atypical antipsychotic use than did youth enrolled in income-eligible Medicaid categories. Nearly one third of such ADHD-diagnosed foster care youth received atypical antipsychotics regardless of age group, with annual duration of use >250 median days in 2-12-year-olds. In concomitant atypical antipsychotic regimens, risperidone, aripiprazole, and quetiapine were the most common. CONCLUSIONS Exposure to atypical antipsychotics in Medicaid-insured youth, in particular for children in foster care and those diagnosed with ADHD, was substantial, warranting outcomes research for long-term effectiveness, safety, and oversight for appropriate cardiometabolic monitoring.

Medicaid Prior Authorization Policies for Pediatric Use of Antipsychotic Medications

Medicaid Prior Authorization Policies for Pediatric Use of Antipsychotic Medications Over the past 2 decades, antipsychotic prescribing to youth, almost exclusively comprising atypical antipsychotic medications, was estimated to have increased from 0.16% in 19931998 to 1.07% in 2005-2009 in office-based physician visits.1 Antipsychotic use is also 5-fold greater in Medicaid-insured youth than in privately insured youth,2 and occurs mostly for youth with clinician-reported externalizing behavior disorders1,2 rather than indications approved by the US Food and Drug Administration (FDA) and indications that are evidence-supported without FDA-approved labeling (eg, psychotic disorders, bipolar disorder, autism-related irritability, and tic disorders).3 The evidence for atypical antipsychotic use among preschoolers and younger children is particularly limited.3 In light of antipsychotic treatment-emergent cardiometabolic adverse events,4 several government reports called for efforts to improve pediatric psychotropic medication oversight in state Medicaid agencies.5 Such efforts include telephone access lines through which prescribers can consult with psychiatrists, letters to prescribers, and, recently, age-restricted prior authorization policies, which require clinicians to obtain preapproval from Medicaid agencies to prescribe atypical antipsychotics to children younger than a certain age as a condition for coverage. A distinct subset of these age-restricted prior authorization policies, classified as peer review policies, brings clinical expertise into the review process by requiring contracted clinicians (peer reviewers) to adjudicate antipsychotic prescriptions for children. Several studies in adults have shown Medicaid prior authorization policies can reduce antipsychotic use. To facilitate empirical evaluation of these policies in youth, we identified state Medicaid programs with a prior authorization policy in effect for pediatric atypical antipsychotic prescribing and characterized these policies according to agerestriction criteria and whether a peer review process was present.

Trends in Subthreshold Psychiatric Diagnoses for Youth in Community Treatment

IMPORTANCE Patterns and trends of subthreshold DSM-IV mental health diagnoses for youth within US community treatment settings merit systematic research. OBJECTIVE To quantify and assess temporal patterns of DSM-IV diagnoses not otherwise specified (NOS) among youth during physician office visits. DESIGN, SETTING, AND PARTICIPANTS We conducted a retrospective study using psychiatric diagnostic data from the US National Ambulatory Medical Care Survey and the National Hospital Ambulatory Medical Care Survey (n = 16,295) from 1999 through 2010, combined in 4-year intervals. Using diagnoses from visits to physicians, we compared trends of the proportional distribution of the major psychiatric diagnoses with subthreshold criteria (coded as NOS) with proportions of diagnoses reaching full criteria. MAIN OUTCOMES AND MEASURES Specific common psychiatric diagnoses NOS compared with full-criteria psychiatric diagnoses. RESULTS Between the 1999-2002 and 2007-2010 periods, the proportion of US medical visits reporting DSM-IV NOS psychiatric diagnoses compared with the proportion reporting full psychiatric diagnostic criteria for youth aged 2 to 19 years rose prominently for major mood diagnostic subtypes. Among all visits for mood disorders, NOS visits grew proportionally 1.5-fold from 45.3% in the 1999-2002 period to 68.8% in the 2007-2010 period (P < .001). Among visits for bipolar disorder, NOS visits increased more than 18-fold, from 3.6% in the 1999-2002 period to 72.6% in the 2007-2010 period (P < .001). In addition, anxiety disorder NOS increased from 44.6% in the 1999-2002 period to 58.1% in the 2007-2010 period. Overall, NOS visits constituted 35.0% of the total psychiatric visits in 2007-2010 but represented 55.9% when attention-deficit/hyperactivity disorder codes were excluded. CONCLUSIONS AND RELEVANCE The expansion of subthreshold (NOS) DSM-IV diagnoses of mood disorder, bipolar disorder, and anxiety disorder in youth that has occurred since 1999 in all likelihood will continue in the DSM-5 era unless administrative efforts are made to alter this practice. Unspecified diagnoses lack research reliability and potentially increase the likelihood of off-label prescribing of psychotropic medication.

Trends in ADHD medication use in children and adolescents in five western countries, 2005-2012

Over the last two decades, the use of ADHD medication in US youth has markedly increased. However, less is known about ADHD medication use among European children and adolescents. A repeated cross-sectional design was applied to national or regional data extracts from Denmark, Germany, the Netherlands, the United Kingdom (UK) and the United States (US) for calendar years 2005/2006-2012. The prevalence of ADHD medication use was assessed, stratified by age and sex. Furthermore, the most commonly prescribed ADHD medications were assessed. ADHD medication use prevalence increased from 1.8% to 3.9% in the Netherlands cohort (relative increase: +111.9%), from 3.3% to 3.7% in the US cohort (+10.7%), from 1.3% to 2.2% in the German cohort (+62.4%), from 0.4% to 1.5% in the Danish cohort (+302.7%), and from 0.3% to 0.5% in the UK cohort (+56.6%). ADHD medication use was highest in 10-14-year olds, peaking in the Netherlands (7.1%) and the US (8.8%). Methylphenidate use predominated in Europe, whereas in the US amphetamines were nearly as common as methylphenidate. Although there was a substantially greater use of ADHD medications in the US cohort, there was a relatively greater increase in ADHD medication use in youth in the four European countries. ADHD medication use patterns in the US differed markedly from those in western European countries.

Antipsychotic prescribing for behavioral disorders in US youth: physician specialty, insurance coverage, and complex regimens.

To assess antipsychotic prescribing patterns according to insurance coverage type and physician specialty in the outpatient treatment of behavioral disorders (BD) in US youth.

Association of Antidepressant Medications With Incident Type 2 Diabetes Among Medicaid-Insured Youths

Importance Antidepressants are one of the most commonly prescribed classes of psychotropic medications among US youths. For adults, there is emerging evidence on the increased risk of type 2 diabetes in association with antidepressant use. However, little is known about the antidepressant treatment–emergent risk of type 2 diabetes among youths. Objective To assess the association between antidepressant use and the risk of incident type 2 diabetes in youths by antidepressant subclass and according to duration of use, cumulative dose, and average daily dose. Design, Setting, and Participants A retrospective cohort study was conducted using Medicaid claims data from 4 geographically diverse, large states of youths 5 to 20 years of age who initiated antidepressant treatment from January 1, 2005, to December 31, 2009. Exposures Antidepressant use (selective serotonin reuptake inhibitors [SSRIs] or serotonin-norepinephrine reuptake inhibitors [SNRIs], tricyclic or other cyclic antidepressants, and other antidepressants) was assessed using the following 4 time-varying measures: current or former use, duration of use, cumulative dose, and average daily dose. Main Outcomes and Measures Incident type 2 diabetes was assessed using discrete-time failure models, adjusting for disease risk score estimated using more than 125 baseline and time-dependent covariates. Results In this cohort of 119 608 youths aged 5 to 20 years who initiated antidepressant treatment (59 087 female youths and 60 521 male youths; 54.7% between 5 and 14 years of age) with a mean follow-up of 22.8 months, 79 285 [66.3%] had SSRI or SNRI exposure. The risk of type 2 diabetes was significantly greater during current use than former use of SSRIs or SNRIs (absolute risk, 1.29 per 10 000 person-months vs 0.64 per 10 000 person-months; adjusted relative risk [RR], 1.88; 95% CI, 1.34-2.64) and tricyclic or other cyclic antidepressants (absolute risk, 0.89 per 10 000 person-months vs 0.48 per 10 000 person-months; RR, 2.15; 95% CI, 1.06-4.36), but not of other antidepressants (absolute risk, 1.15 per 10 000 person-months vs 1.12 per 10 000 person-months; RR, 0.99; 95% CI, 0.66-1.50). Furthermore, for youths currently using SSRIs or SNRIs, the risk of type 2 diabetes increased with the duration of use (RR, 2.66; 95% CI, 1.45-4.88 for >210 days and RR, 2.56; 95% CI, 1.29-5.08 for 151-210 days compared with 1-90 days) and with the cumulative dose (RR, 2.44; 95% CI, 1.35-4.43 for >4500 mg and RR, 2.17; 95% CI, 1.07-4.40 for 3001-4500 mg compared with 1-1500 mg in fluoxetine hydrochloride dose equivalents). By contrast, neither the duration nor the cumulative dose of other antidepressants was associated with an increased risk of type 2 diabetes. The risk of type 2 diabetes increased significantly with the average daily dose among youths with more than 150 days of SSRI or SNRI use (RR, 2.39; 95% CI, 1.04-5.52 for >15.0 vs ⩽15.0 mg/d) but not among youths with 1 to 150 days of SSRI or SNRI use. Conclusions and Relevance In a large cohort of youths insured by Medicaid, the use of SSRIs or SNRIs—the most commonly used antidepressant subclass—was associated with an increased risk of type 2 diabetes that intensified with increasing duration of use, cumulative dose, and average daily dose.

Construct validity and factor structure of survey-based assessment of cost-related medication burden.

Background:Millions of Americans are burdened by out-of-pocket prescription costs. Although many survey measures have been developed to assess this burden, the construct validity and the factor structure of these instruments have not been rigorously assessed. Objectives:To characterize the factor structure and the construct validity of items assessing cost-related medication burden. Methods:We applied exploratory factor and confirmatory factor analyses to the 2009 Medicare Current Beneficiary Survey, focusing on 10 items assessing cost-related mediation burden among a nationally representative sample of community-dwelling Medicare beneficiaries. The fit of competing models was compared using several indices. Results:The study population (N=8777) was predominantly aged over 65 years (83.3%), female (54.4%), and white (84.3%). Two distinct factors were present for the medication cost-reduction strategies: (1) cost-related medication nonadherence and (2) drug-shopping behaviors, not directly impacting medication compliance. The two factors were moderately correlated (r=0.55), highlighting the presence of a 2 distinct but related constructs for cost-related medication burden. An item assessing the use of mail or internet pharmacies did not load well on either factor and may not necessarily measure medication-related cost burden. An item assessing reduced spending on basic needs loaded strongly on the same factor with the cost-related medication nonadherence items, suggesting they together may represent extreme compensatory behaviors that may adversely affect health outcomes. Conclusions:Two distinct constructs were derived from these items examining cost-related medication burden. Although cost-related medication burden is often associated with nonadherence, drug-shopping behaviors that do not directly impact adherence are also important measure of this burden.