A Genetics-Focused Lens on Social Constructs in Pharmacy Education

OBJECTIVE

Incorporating diversity, equity, inclusion, and anti-racism principles into clinical and didactic education is essential because each influence cognitive and affective attitudes in pharmacy practice. Educators must learn from the past to enlighten the future. For example, race is a social construct, not a biological construct. However, it persistently acts as a surrogate for determining medical diagnoses and treatment.

FINDINGS

Precision medicine and pharmacogenomics can serve as a basis for deconstructing social constructs surrounding race and other social determinants of health.

SUMMARY

In this review, the authors highlight why using race in health education will lead to less-than-optimal clinical decisions and discuss best practices for incorporating diversity, equity, inclusion, and anti-racism into health education from a pharmacogenomic-based perspective.

Efficacy of personal pharmacogenomic testing as an educational tool in the pharmacy curriculum: A nonblinded, randomized controlled trial

Personal genomic educational testing (PGET) has been suggested as a strategy to improve student learning for pharmacogenomics (PGx), but no randomized studies have evaluated PGET’s educational benefit. We investigated the effect of PGET on student knowledge, comfort, and attitudes related to PGx in a nonblinded, randomized controlled trial. Consenting participants were randomized to receive PGET or no PGET (NPGET) during 4 subsequent years of a PGx course. All participants completed a pre‐survey and post‐survey designed to assess (1) PGx knowledge, (2) comfort with PGx patient education and clinical skills, and (3) attitudes toward PGx. Instructors were blinded to PGET assignment. The Wilcoxon Rank Sum test was used to compare pre‐survey and post‐survey PGx knowledge, comfort, and attitudes. No differences in baseline characteristics were observed between PGET (n = 117) and NPGET (n = 116) participants. Among all participants, significant improvement was observed in PGx knowledge (mean 57% vs. 39% correct responses; p < 0.001) with similar results for student comfort and attitudes. Change in pre/post‐PGx knowledge, comfort, and attitudes were not significantly different between PGET and NPGET groups (mean 19.5% vs. 16.7% knowledge improvement, respectively; p = 0.41). Similar results were observed for PGET participants carrying a highly actionable PGx variant versus PGET participants without an actionable variant. Significant improvement in Likert scale responses were observed in PGET versus NPGET for questions that assessed student engagement (p = 0.020) and reinforcement of course concepts (p = 0.006). Although some evidence of improved engagement and participation was observed, the results of this study suggest that PGET does not directly improve student PGx knowledge, comfort, and attitudes.

Racial disparities and treatment trends among young-onset colorectal cancer patients: An analysis of a hospital cancer registry

BACKGROUND

There is an increasing trend of colorectal cancer (CRC) incidence and mortality in individuals under the age of 50. The impact of age on the outcomes of CRC remains controversial. This study examined the characteristics and treatment trends of young-onset CRC by comparing patients < 50 years of age to those ≥50.

METHODS

Data were retrospectively obtained from one of the largest hospital systems in Virginia. The sample included patients diagnosed with CRC from 2008 to 2016. Bivariate analyses were used to describe patients' characteristics. Stratified and multivariate analyses were used to evaluate the association between treatments and age groups in different stages at diagnosis.

RESULTS

Approximately 11.6 % (n = 522) of the cohort were younger than 50 years old at diagnosis with a mean age of 42.7 (SD = 5.9) years. Compared to their older counterpart (50 and older), young-onset patients were more likely to be African American (28.7 % (n = 150) vs. 23.7 % (n = 944)), to own private insurance (68.5 % (n = 313) vs. 27.6 % (n = 1032)), to have never used tobacco products (50.4 % (n = 237) vs. 43.8 % (n = 1616)), and to be late stage at diagnosis (68.6 % (n = 358) vs. 52.5 % (n = 2090)) (all p < 0.05). For early stage diagnosis, over 98 % of the young-onset treatments were surgery. For late stage diagnosis, the cancer treatment for young onset patients were a combination of surgery (89.4 %), radiation (82.5 %), and chemotherapy (86.3 %). The results of the analyses also demonstrated that patients with young-onset CRC have higher odds for surgery [OR = 1.76, 95 %CI (1.26, 2.47)], radiation [OR = 1.31, 95 %CI (1.17, 1.47)], and chemotherapy [OR = 3.34, 95 %CI (2.62, 4.25)].

CONCLUSIONS

Findings confirmed late-stage prevalence among young-onset as well as significant demographic differences with patients' age ≥50. This study is one of few to explore the characteristics and assess treatment of young patients with CRC using U.S hospital data. Moreover, further studies need to clarify the effects of biological properties like genetic influences and environmental factors between races on cancer patient outcomes.

The Impact of African Ancestry on Prostate Cancer Disparities in the Era of Precision Medicine

Prostate cancer disproportionately affects men of African ancestry at nearly twice the rate of men of European ancestry despite the advancement of treatment strategies and prevention. In this review, we discuss the underlying causes of these disparities including genetics, environmental/behavioral, and social determinants of health while highlighting the implications and challenges that contribute to the stark underrepresentation of men of African ancestry in clinical trials and genetic research studies. Reducing prostate cancer disparities through the development of personalized medicine approaches based on genetics will require a holistic understanding of the complex interplay of non-genetic factors that disproportionately exacerbate the observed disparity between men of African and European ancestries.

Two-stage Study of Familial Prostate Cancer by Whole-exome Sequencing and Custom Capture Identifies 10 Novel Genes Associated with the Risk of Prostate Cancer

BACKGROUND

Family history of prostate cancer (PCa) is a well-known risk factor, and both common and rare genetic variants are associated with the disease.

OBJECTIVE

To detect new genetic variants associated with PCa, capitalizing on the role of family history and more aggressive PCa.

DESIGN, SETTING, AND PARTICIPANTS

A two-stage design was used. In stage one, whole-exome sequencing was used to identify potential risk alleles among affected men with a strong family history of disease or with more aggressive disease (491 cases and 429 controls). Aggressive disease was based on a sum of scores for Gleason score, node status, metastasis, tumor stage, prostate-specific antigen at diagnosis, systemic recurrence, and time to PCa death. Genes identified in stage one were screened in stage two using a custom-capture design in an independent set of 2917 cases and 1899 controls.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Frequencies of genetic variants (singly or jointly in a gene) were compared between cases and controls.

RESULTS AND LIMITATIONS

Eleven genes previously reported to be associated with PCa were detected (ATM, BRCA2, HOXB13, FAM111A, EMSY, HNF1B, KLK3, MSMB, PCAT1, PRSS3, and TERT), as well as an additional 10 novel genes (PABPC1, QK1, FAM114A1, MUC6, MYCBP2, RAPGEF4, RNASEH2B, ULK4, XPO7, and THAP3). Of these 10 novel genes, all but PABPC1 and ULK4 were primarily associated with the risk of aggressive PCa.

CONCLUSIONS

Our approach demonstrates the advantage of gene sequencing in the search for genetic variants associated with PCa and the benefits of sampling patients with a strong family history of disease or an aggressive form of disease.

PATIENT SUMMARY

Multiple genes are associated with prostate cancer (PCa) among men with a strong family history of this disease or among men with an aggressive form of PCa.

Abstract C050: Deleterious coding variants in African American Hereditary Prostate Cancer Study (AAHPC) families

Purpose: Prostate cancer is the most common cancer in males, with a ~1.5-2-fold higher incidence in African American men when compared with whites. Epidemiologic evidence supports a large heritable contribution to prostate cancer, with over 100 susceptibility loci identified to date that can explain ~33% of the familial risk. A portion of the undefined risk may be due to rare susceptibility variants. The African American Hereditary Prostate Cancer (AAHPC) Study, established in 1997, enrolled 77 African American families from seven clinical sites across the United States. The aim of this study is to identify rare, predictive, deleterious variants through exome sequencing of 99 cases from families selected from the AAHPC families and three 1000 Genome controls.

Methods: To explore the contribution of rare variation in coding regions to prostate cancer risk, we sequenced the exomes of 99 AAHPC cases at a mean coverage of 30x. Post-variant calling quality control (QC) was implemented using Golden Helix SVS 8 software with filters set for removal of variants with Read Depth &gt;10, Quality Score &gt;10, and Quality Score: Read Depth Ratio &gt; 0.5. Mendelian inconsistency was checked using PLINK. Prioritization of all candidate genes/variants was evaluated using online databases 1000 Genome and bioinformatics tool ANNOVAR for non-reference allele frequency and predictions of functional impact.

Conclusions: Through exome sequencing of 99 AAHPC cases and three 1000 Genome controls, we identified 37 nonsynonymous single-nucleotide variants that are considered damaging by at least one predictive scoring tool in our candidate genes. Interesting candidate variants were found in known cancer susceptibility loci BRCA2, MSR1, PCNT, STAT3, WRN and ZFHX3. Future results are pending additional QC and analyses to determine which variants are shared by related individuals within each family compared to those not seen in the controls.

Citation Format: Deyana D. Lewis, Shukmei Wong, Angela S. Baker, Joan E. Bailey-Wilson, John D. Carpten, Cheryl D. Cropp. Deleterious coding variants in African American Hereditary Prostate Cancer Study (AAHPC) families [abstract]. In: Proceedings of the Eleventh AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2018 Nov 2-5; New Orleans, LA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl):Abstract nr C050.

Associations of Mitochondrial and Nuclear Mitochondrial Variants and Genes with Seven Metabolic Traits

Mitochondria (MT), the major site of cellular energy production, are under dual genetic control by 37 mitochondrial DNA (mtDNA) genes and numerous nuclear genes (MT-nDNA). In the CHARGEmtDNA+ Consortium, we studied genetic associations of mtDNA and MT-nDNA associations with body mass index (BMI), waist-hip-ratio (WHR), glucose, insulin, HOMA-B, HOMA-IR, and HbA1c. This 45-cohort collaboration comprised 70,775 (insulin) to 170,202 (BMI) pan-ancestry individuals. Validation and imputation of mtDNA variants was followed by single-variant and gene-based association testing. We report two significant common variants, one in MT-ATP6 associated (p ≤ 5E-04) with WHR and one in the D-loop with glucose. Five rare variants in MT-ATP6, MT-ND5, and MT-ND6 associated with BMI, WHR, or insulin. Gene-based meta-analysis identified MT-ND3 associated with BMI (p ≤ 1E-03). We considered 2,282 MT-nDNA candidate gene associations compiled from online summary results for our traits (20 unique studies with 31 dataset consortia's genome-wide associations [GWASs]). Of these, 109 genes associated (p ≤ 1E-06) with at least 1 of our 7 traits. We assessed regulatory features of variants in the 109 genes, cis- and trans-gene expression regulation, and performed enrichment and protein-protein interactions analyses. Of the identified mtDNA and MT-nDNA genes, 79 associated with adipose measures, 49 with glucose/insulin, 13 with risk for type 2 diabetes, and 18 with cardiovascular disease, indicating for pleiotropic effects with health implications. Additionally, 21 genes related to cholesterol, suggesting additional important roles for the genes identified. Our results suggest that mtDNA and MT-nDNA genes and variants reported make important contributions to glucose and insulin metabolism, adipocyte regulation, diabetes, and cardiovascular disease.

The 677C→T variant of MTHFR is the major genetic modifier of biomarkers of folate status in a young, healthy Irish population

Background

Genetic polymorphisms can explain some of the population- and individual-based variations in nutritional status biomarkers.

Objective

We sought to screen the entire human genome for common genetic polymorphisms that influence folate-status biomarkers in healthy individuals.

Design

We carried out candidate gene analyses and genome-wide association scans in 2232 young, healthy Irish subjects to evaluate which common genetic polymorphisms influence red blood cell folate, serum folate, and plasma total homocysteine.

Results

The 5,10-methylenetetrahydrofolate reductase (MTHFR) 677C→T (rs1801133) variant was the major genetic modifier of all 3 folate-related biomarkers in this Irish population and reached genome-wide significance for red blood cell folate (P = 1.37 × 10-17), serum folate (P = 2.82 × 10-11), and plasma total homocysteine (P = 1.26 × 10-19) concentrations. A second polymorphism in the MTHFR gene (rs3753584, P = 1.09 × 10-11) was the only additional MTHFR variant to exhibit any significant independent effect on red blood cell folate. Other MTHFR variants, including the 1298A→C variant (rs1801131), appeared to reach genome-wide significance, but these variants shared linkage disequilibrium with MTHFR 677C→T and were not significant when analyzed in MTHFR 677CC homozygotes. No additional non-MTHFR modifiers of red blood cell or plasma folate were detected. Two additional genome-wide significant modifiers of plasma homocysteine were found in the region of the dipeptidase 1 (DPEP1) gene on chromosome 16 and the Twist neighbor B (TWISTNB) gene on chromosome 7.

Conclusions

The MTHFR 677C→T variant is the predominant genetic modifier of folate status biomarkers in this healthy Irish population. It is not necessary to determine MTHFR 677C→T genotype to evaluate folate status because its effect is reflected in concentrations of standard folate biomarkers. The MTHFR 1298A→C variant had no independent effect on folate status biomarkers. To our knowledge, this is the first genome-wide association study report on red blood cell folate and the first report of an association between homocysteine and TWISTNB.

ComPaSS-GWAS: A method to reduce type I error in genome-wide association studies when replication data are not available

Results from association studies are traditionally corroborated by replicating the findings in an independent data set. Although replication studies may be comparable for the main trait or phenotype of interest, it is unlikely that secondary phenotypes will be comparable across studies, making replication problematic. Alternatively, there may simply not be a replication sample available because of the nature or frequency of the phenotype. In these situations, an approach based on complementary pairs stability selection for genome-wide association study (ComPaSS-GWAS), is proposed as an ad-hoc alternative to replication. In this method, the sample is randomly split into two conditionally independent halves multiple times (resamples) and a GWAS is performed on each half in each resample. Similar in spirit to testing for association with independent discovery and replication samples, a marker is corroborated if its p-value is significant in both halves of the resample. Simulation experiments were performed for both nongenetic and genetic models. The type I error rate and power of ComPaSS-GWAS were determined and compared to the statistical properties of a traditional GWAS. Simulation results show that the type I error rate decreased as the number of resamples increased with only a small reduction in power and that these results were comparable with those from a traditional GWAS. Blood levels of vitamin pyridoxal 5'-phosphate from the Trinity Student Study (TSS) were used to validate this approach. The results from the validation study were compared to, and were consistent with, those obtained from previously published independent replication data and functional studies.

Abstract P3-04-02: Molecular analysis of breast cancers from individuals with hereditary cancer syndromes secondary to mutations in BRCA1, BRCA2, ATM, CHEK2, and PALB2

Background: Despite a growing understanding of the somatic landscape of breast tumors from BRCA1 and BRCA2 mutation carriers, less is known about breast tumors from carriers of germline mutations in other homologous recombination and DNA repair pathway genes such as ATM, CHEK2, and PALB2.

Methods: We identified 44 clinically annotated breast cancer cases that included carriers of germline mutations in BRCA1 (n=9), BRCA2 (n=9), ATM (n=5), CHEK2 (n=7), and PALB2 (n=6) from the Hereditary Cancer Risk Program at BUMC. Sporadic breast cancers cases (n=8) were also collected. Genomic DNA and RNA were extracted from macro-dissected FFPE tumor sections, adjacent normal FFPE tissue, along with constitutional genomic DNA from blood. Expanded whole exome sequencing (WES) was performed on normal/tumor pairs and RNA-seq from tumors for each case. Bioinformatics analysis was performed using industry standard methods for somatic characterization.

Results: All germline mutations were confirmed by WES. Somatic mutational analysis and copy number profiling from WES revealed the greatest similarities among BRCA1 and CHEK2 carriers. As expected, TP53 mutations were found in 8 of 9 BRCA1 carriers as all were triple negative subtype. We also detected somatic TP53 mutations in tumors from 4 of 7 CHEK2 carriers. Somatic TP53 mutations were found in only 1 of 7 BRCA2 tumors and 1 of 4 PALB2 tumors tested. Furthermore, BRCA1 and CHEK2 tumors showed trends of having higher mutation burden. Analysis of copy number BRCAness demonstrated stronger similarities between BRCA1, ATM, CHEK2, and PALB2 tumors. BRCA2 tumors were unique with fewer events and characterized by specific amplifications including 11q23 (CCND1) and 17q23 (BRIP1). Hierarchical clustering of RNA-seq data revealed strong clustering of BRCA1 tumors compared to all other tumors, predominantly attributed to breast cancer subtype. Furthermore, pathway analysis of genes that distinguish BRCA1 mutation positive versus non-BRCA mutated tumors showed strong correlation to pro-inflammatory and immune pathway signatures.

Conclusions: Molecular analysis of 44 breast cancers from individuals with inherited predisposition to breast cancer via BRCA1, BRCA2, ATM, CHEK2, and PALB2 germline mutations demonstrated strongest somatic similarities between BRCA1 and CHEK2 tumors although all BRCA1 were TNBC and all CHEK2 tumors were ER positive. Marked differential gene expression differences in RNA expression patterns were observed in BRCA1 mutation carriers compared with all other groups analyzed. Our study is among the first to interrogate the profile of non-BRCA mutated hereditary breast cancers.

Citation Format: Blum JL, Wong S, Pearson EJ, Nair A, Snipes GJ, Briones N, Baker A, Cropp CD, Carpten JD. Molecular analysis of breast cancers from individuals with hereditary cancer syndromes secondary to mutations in BRCA1, BRCA2, ATM, CHEK2, and PALB2 [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P3-04-02.

The FUT2 secretor variant p.Trp154Ter influences serum vitamin B12 concentration via holo-haptocorrin, but not holo-transcobalamin, and is associated with haptocorrin glycosylation

Vitamin B12 deficiency is common in older individuals. Circulating vitamin B12 concentration can be used to diagnose deficiency, but this test has substantial false positive and false negative rates. We conducted genome-wide association studies (GWAS) in which we resolved total serum vitamin B12 into the fractions bound to transcobalamin and haptocorrin: two carrier proteins with very different biological properties. We replicated reported associations between total circulating vitamin B12 concentrations and a common null variant in FUT2. This allele determines the secretor phenotype in which blood group antigens are found in non-blood body fluids. Vitamin B12 bound to haptocorrin (holoHC) remained highly associated with FUT2 rs601338 (p.Trp154Ter). Transcobalamin bound vitamin B12 (holoTC) was not influenced by this variant. HoloTC is the bioactive the form of the vitamin and is taken up by all tissues. In contrast, holoHC is only taken up by the liver. Using holoHC from individuals with known FUT2 genotypes, we demonstrated that FUT2 rs601338 genotype influences the glycosylation of haptocorrin. We then developed an experimental model demonstrating that holoHC is transported into cultured hepatic cells (HepG2) via the asialoglycoprotein receptor (ASGR). Our data challenge current published hypotheses on the influence of genetic variation on this clinically important measure and are consistent with a model in which FUT2 rs601338 influences holoHC by altering haptocorrin glycosylation, whereas B12 bound to non-glycosylated transcobalamin (i.e. holoTC) is not affected. Our findings explain some of the observed disparity between use of total B12 or holoTC as first-line clinical tests of vitamin B12 status.

Comparison of parametric and machine methods for variable selection in simulated Genetic Analysis Workshop 19 data

Current findings from genetic studies of complex human traits often do not explain a large proportion of the estimated variation of these traits due to genetic factors. This could be, in part, due to overly stringent significance thresholds in traditional statistical methods, such as linear and logistic regression. Machine learning methods, such as Random Forests (RF), are an alternative approach to identify potentially interesting variants. One major issue with these methods is that there is no clear way to distinguish between probable true hits and noise variables based on the importance metric calculated. To this end, we are developing a method called the Relative Recurrency Variable Importance Metric (r2VIM), a RF-based variable selection method. Here, we apply r2VIM to the unrelated Genetic Analysis Workshop 19 data with simulated systolic blood pressure as the phenotype. We compare the number of “true” functional variants identified by r2VIM with those identified by linear regression analyses that use a Bonferroni correction to calculate a significance threshold. Our results show that r2VIM performed comparably to linear regression. Our findings are proof-of-concept for r2VIM, as it identifies a similar number of functional and nonfunctional variants as a more commonly used technique when the optimal importance score threshold is used.

Abstract B40: Rare variant discovery in known cancer genes from whole-exome sequencingof African American hereditary prostate cancer families

African American Hereditary Prostate Cancer Study (AAHPC) was developed as a national collaboration to explore the role of genetics in the causation of hereditary prostate cancer (HPC) in African American (AA) men. AAHPC is in partnership with the International Consortium for Prostate Cancer Genetics (ICPCG), which conducts collaborative studies of HPC genetics in multiplex families. As part of an ICPCG sequencing study of 539 affected individuals from 366 HPC pedigrees, we performed whole exome sequencing in 21 ICPCG AA families, of which there were 14 AAHPC affected men from 11 pedigrees. The combined ICPCG AA cohort consisted of N=26 affected members. Post-variant calling quality control (QC) was implemented using Golden Helix SVS 8 software with filters set for removal of variants with Read Depth &lt; 10, Quality Score &lt; 20, Quality Score: Read Depth Ratio &lt; 0.5, Call Rate &lt; 0.75. Variants were additionally filtered by MAF based on the NHLBI ESP650051-V2 exomes variant frequencies for the AA population using a MAF threshold of 5%. Following QC, 176/299 SNVs and 20/39 INDELs remained for further analysis. In these analyses, we focused on 13 known cancer genes (MSR1, AR, BRCA1, BRCA2, BTNL2, EPHB2, CDH1, RNASEL, ELAC2, HOXB13, CHEK2, TP53 and NBN). Three sequenced families had &gt; 1 affected members sequenced (2 or 3 per family) and the remaining 18 families had one member sequenced. Under the dominant model, our preliminary results show that no rare variants in the 13 candidate genes were found in 3/3 affecteds in two families. Rare SNVs in seven candidate genes (AR, CDH1, ELAC2, HOXB13, RNASEL, BRCA2 and EPHB2) were found in 2/3 affecteds for two families and 2/2 affecteds in one family. Several of the remaining 18 affected men (1 sequenced per pedigree) shared the same rare SNV in these candidate genes. For INDELs, rare variants in three candidate genes were found in pedigrees with ≥ 2 affecteds. Several of the remaining 18 affected men (one sequenced per pedigree) shared the same rare INDEL. Additional QC is underway to validate these variants and bioinformatic analyses are being used to predict effects of the variants in an effort to unravel the complex genetic heterogeneity of HPC in AA.

Citation Format: Cheryl D. Cropp, Shannon K. McDonnell, Sumit Middha, Melissa DeRycke, Danielle M. Karyadi, Daniel Schaid, Stephen N. Thibodeau, William B. Isaacs, Elaine A. Ostrander, Janet Stanford, Kathleen A. Cooney, Joan E. Bailey-Wilson, John D. Carpten. Rare variant discovery in known cancer genes from whole-exome sequencingof African American hereditary prostate cancer families. [abstract]. In: Proceedings of the Eighth AACR Conference on The Science of Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; Nov 13-16, 2015; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2016;25(3 Suppl):Abstract nr B40.

Common Variants at Putative Regulatory Sites of the Tissue Nonspecific Alkaline Phosphatase Gene Influence Circulating Pyridoxal 5'-Phosphate Concentration in Healthy Adults

BACKGROUND

Vitamin B-6 interconversion enzymes are important for supplying pyridoxal 5'-phosphate (PLP), the co-enzyme form, to tissues. Variants in the genes for these enzymes [tissue nonspecific alkaline phosphatase (ALPL), pyridoxamine 5'-phosphate oxidase, pyridoxal kinase, and pyridoxal phosphatase] could affect enzyme function and vitamin B-6 status.

OBJECTIVES

We tested whether single-nucleotide polymorphisms (SNPs) in these genes influence vitamin B-6 status markers [plasma PLP, pyridoxal (PL), and 4-pyridoxic acid (PA)], and explored potential functional effects of the SNPs.

METHODS

Study subjects were young, healthy adults from Ireland (n = 2345). We measured plasma PLP, PL, and PA with liquid chromatography-tandem mass spectrometry and genotyped 66 tag SNPs in the 4 genes. We tested for associations with single SNPs in candidate genes and also performed genome-wide association study (GWAS) and gene-based analyses.

RESULTS

Seventeen SNPs in ALPL were associated with altered plasma PLP in candidate gene analyses (P < 1.89 × 10(-4)). In the GWAS, 5 additional ALPL SNPs were associated with altered plasma PLP (P < 5.0 × 10(-8)). Gene-based analyses that used the functional linear model β-spline (P = 4.04 × 10(-15)) and Fourier spline (P = 5.87 × 10(-15)) methods also showed associations between ALPL and altered plasma PLP. No SNPs in other genes were associated with plasma PLP. The association of the minor CC genotype of 1 ALPL SNP, rs1256341, with reduced ALPL expression in the HapMap Northern European ancestry population is consistent with the positive association between the CC genotype and plasma PLP in our study (P = 0.008). No SNP was associated with altered plasma PL or PA.

CONCLUSIONS

In healthy adults, common variants in ALPL influence plasma PLP concentration, the most frequently used biomarker for vitamin B-6 status. Whether these associations are indicative of functional changes in vitamin B-6 status requires more investigation.

8q24 risk alleles and prostate cancer in African-Barbadian men

BACKGROUND

African American men (AA) exhibit a disproportionate share of prostate cancer (PRCA) incidence, morbidity, and mortality. Several genetic association studies have implicated select 8q24 loci in PRCA risk in AA. The objective of this investigation is to evaluate the association between previously reported 8q24 risk alleles and PRCA in African-Barbadian (AB) men known to have high rates of PRCA.

METHODS

Ten previously reported candidate tag SNPs were genotyped and/or imputed in the 8q24 region in 532 AB men with PRCA and 513 AB controls from the Prostate Cancer in a Black Population (PCBP) study.

RESULTS

Rs2124036 was significant in AB men, (OR = 2.7, 95% CI (1.3-5.3), P = 0.005, Empirical (max (T), corrected for multiple testing) P = 0.03) for the homozygous C/C genotype. Only a single SNP from this region remained statistically significant in our analysis of our AB population. These results may indicate the presence of a founder effect or due to the chosen SNPs not tagging an ancestral haplotype bearing the 8q24 risk allele(s) in this population or could reflect inadequate power to detect an association. We conducted a meta-analysis including our AB population along with two additional African Caribbean populations from Tobago and Jamaica for SNPs rs16901979 and rs1447295. Meta-analysis results were most significant for rs16901979 A allele (Z score 2.73; P = 0.006) with a summary OR = 1.31 (95% CI: 1.09-1.58).

CONCLUSIONS

Additional studies are needed to provide deeper genotype coverage to further interrogate the 8q24 region to understand its contribution to PRCA in this population.

False-positive rates in two-point parametric linkage analysis

Two-point linkage analyses of whole genome sequence data are a promising approach to identify rare variants that segregate with complex diseases in large pedigrees because, in theory, the causal variants have been genotyped. We used whole genome sequence data and simulated traits provided by Genetic Analysis Workshop 18 to evaluate the proportion of false-positive findings in a binary trait using classic two-point parametric linkage analysis. False-positive genome-wide significant log of odds (LOD) scores were identified in more than 80% of 50 replicates for a binary phenotype generated by dichotomizing a quantitative trait that was simulated with a polygenic component (that was not based on any of the provided whole genome sequence genotypes). In contrast, when the trait was truly nongenetic (created by randomly assigning affected-unaffected status), the number of false-positive results was well controlled. These results suggest that when using two-point linkage analyses on whole genome sequence data, one should carefully examine regions yielding significant two-point LOD scores with multipoint analysis and that a more stringent significance threshold may be needed.

SLCO1B1 variants and urine arsenic metabolites in the Strong Heart Family Study

Arsenic species patterns in urine are associated with risk for cancer and cardiovascular diseases. The organic anion transporter coded by the gene SLCO1B1 may transport arsenic species, but its association with arsenic metabolites in human urine has not yet been studied. The objective of this study is to evaluate associations of urine arsenic metabolites with variants in the candidate gene SLCO1B1 in adults from the Strong Heart Family Study. We estimated associations between % arsenic species biomarker traits and 5 single-nucleotide polymorphisms (SNPs) in the SLCO1B1 gene in 157 participants, assuming additive genetics. Linear regression models for each SNP accounted for kinships and were adjusted for sex, body mass index, and study center. The minor allele of rs1564370 was associated with lower %MMA (p = .0003) and higher %DMA (p = .0002), accounting for 8% of the variance for %MMA and 9% for %DMA. The rs1564370 minor allele homozygote frequency was 17% and the heterozygote frequency was 43%. The minor allele of rs2291075 was associated with lower %MMA (p = .0006) and higher %DMA (p = .0014), accounting for 7% of the variance for %MMA and 5% for %DMA. The frequency of rs2291075 minor allele homozygotes was 1% and of heterozygotes was 15%. Common variants in SLCO1B1 were associated with differences in arsenic metabolites in a preliminary candidate gene study. Replication of this finding in other populations and analyses with respect to disease outcomes are needed to determine whether this novel candidate gene is important for arsenic-associated disease risks.

Reduced renal clearance of cefotaxime in asians with a low-frequency polymorphism of OAT3 (SLC22A8)

Organic anion transporter 3 (OAT3, SLC22A8), a transporter expressed on the basolateral membrane of the proximal tubule, plays a critical role in the renal excretion of organic anions including many therapeutic drugs. The goal of this study was to evaluate the in vivo effects of the OAT3-Ile305Phe variant (rs11568482), present at 3.5% allele frequency in Asians, on drug disposition with a focus on cefotaxime, a cephalosporin antibiotic. In HEK293-Flp-In cells, the OAT3-Ile305Phe variant had a lower maximum cefotaxime transport activity, Vmax , [159 ± 3 nmol*(mg protein)(-1) /min (mean ± SD)] compared with the reference OAT3 [305 ± 28 nmol*(mg protein)(-1) /min, (mean ± SD), p < 0.01], whereas the Michaelis-Menten constant values (Km ) did not differ. In healthy volunteers, we found volunteers that were heterozygous for the Ile305Phe variant and had a significantly lower cefotaxime renal clearance (CLR ; mean ± SD: 84.8 ± 32.1 mL/min, n = 5) compared with volunteers that were homozygous for the reference allele (158 ± 44.1 mL/min, n = 10; p = 0.006). Furthermore, the net secretory component of cefotaxime renal clearance (CLsec ) was reduced in volunteers heterozygous for the variant allele [33.3 ± 31.8 mL/min (mean ± SD)] compared with volunteers homozygous for the OAT3 reference allele [97.0 ± 42.2 mL/min (mean ± SD), p = 0.01]. In summary, our study suggests that a low-frequency reduced-function polymorphism of OAT3 associates with reduced cefotaxime CLR and CL(sec) .

Abstract 3648: Unraveling phenotype heterogeneity in prostate cancer susceptibility in Finland utilizing covariate-based analysis

Prostate cancer is the most common male cancer in developed countries. Previously, we reported a genome-wide linkage scan in 69 Finnish Hereditary Prostate Cancer (HPC) families, which replicated the HPC9 locus on 17q21-q22 and a locus on 2q37. We used ordered subset analysis (OSA) to detect other loci linked to HPC in subsets of families to detect other loci linked to HPC incorporating mean family age of onset as a trait-related covariate to address genetic heterogeneity. The overall mean age of onset across the families was 66.2±8.8 years while the range of individual onset ages ranged from 46-98 years and age of onset varies within families. The highest OSA LOD score was 2.876 (ΔLOD p=0.02) on 15q26.2-q26.3 in a subset of 40 families ascending by age at onset, suggesting that a subset of early age at onset families may be segregating a risk allele(s) at this locus. No other ΔLOD scores were significant after permutation testing. To better capture the effect of age on the linkage signals, we used LODPAL to perform a model-free linkage analysis in affected relative pairs, while adjusting for the age of each individual family member as a single covariate. Preliminary results revealed strong evidence of linkage to HPC on chromosome 15q (LOD=4.9, 132cM) and 8q (LOD=3.1, 157cM). Future analyses are planned which will use age of onset, PSA levels and other clinical characteristics to prioritize regions which may harbor genetic variants of large effect on PRCA.

Citation Format: Cheryl D. Cropp, Claire L. Simpson, Tiina Wahlfors, Asha George, MaryPat S. Jones, Ursula Harper, Damaris Ponciano-Jackson, Teuvo Tammela, Johanna Schleutker, Joan E. Bailey-Wilson. Unraveling phenotype heterogeneity in prostate cancer susceptibility in Finland utilizing covariate-based analysis. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3648. doi:10.1158/1538-7445.AM2013-3648

Gene expression profiling of transporters in the solute carrier and ATP-binding cassette superfamilies in human eye substructures

The barrier epithelia of the cornea and retina control drug and nutrient access to various compartments of the human eye. While ocular transporters are likely to play a critical role in homeostasis and drug delivery, little is known about their expression, localization and function. In this study, the mRNA expression levels of 445 transporters, metabolic enzymes, transcription factors and nuclear receptors were profiled in five regions of the human eye: cornea, iris, ciliary body, choroid and retina. Through RNA expression profiling and immunohistochemistry, several transporters were identified as putative targets for drug transport in ocular tissues. Our analysis identified SLC22A7 (OAT2), a carrier for the antiviral drug acyclovir, in the corneal epithelium, in addition to ABCG2 (BCRP), an important xenobiotic efflux pump, in retinal nerve fibers and the retinal pigment epithelium. Collectively, our results provide an understanding of the transporters that serve to maintain ocular homeostasis and which may be potential targets for drug delivery to deep compartments of the eye.

Analysis of Xq27-28 linkage in the international consortium for prostate cancer genetics (ICPCG) families

BACKGROUND

Genetic variants are likely to contribute to a portion of prostate cancer risk. Full elucidation of the genetic etiology of prostate cancer is difficult because of incomplete penetrance and genetic and phenotypic heterogeneity. Current evidence suggests that genetic linkage to prostate cancer has been found on several chromosomes including the X; however, identification of causative genes has been elusive.

METHODS

Parametric and non-parametric linkage analyses were performed using 26 microsatellite markers in each of 11 groups of multiple-case prostate cancer families from the International Consortium for Prostate Cancer Genetics (ICPCG). Meta-analyses of the resultant family-specific linkage statistics across the entire 1,323 families and in several predefined subsets were then performed.

RESULTS

Meta-analyses of linkage statistics resulted in a maximum parametric heterogeneity lod score (HLOD) of 1.28, and an allele-sharing lod score (LOD) of 2.0 in favor of linkage to Xq27-q28 at 138 cM. In subset analyses, families with average age at onset less than 65 years exhibited a maximum HLOD of 1.8 (at 138 cM) versus a maximum regional HLOD of only 0.32 in families with average age at onset of 65 years or older. Surprisingly, the subset of families with only 2-3 affected men and some evidence of male-to-male transmission of prostate cancer gave the strongest evidence of linkage to the region (HLOD = 3.24, 134 cM). For this subset, the HLOD was slightly increased (HLOD = 3.47 at 134 cM) when families used in the original published report of linkage to Xq27-28 were excluded.

CONCLUSIONS

Although there was not strong support for linkage to the Xq27-28 region in the complete set of families, the subset of families with earlier age at onset exhibited more evidence of linkage than families with later onset of disease. A subset of families with 2-3 affected individuals and with some evidence of male to male disease transmission showed stronger linkage signals. Our results suggest that the genetic basis for prostate cancer in our families is much more complex than a single susceptibility locus on the X chromosome, and that future explorations of the Xq27-28 region should focus on the subset of families identified here with the strongest evidence of linkage to this region.

Racial disparities in the association between variants on 8q24 and prostate cancer: a systematic review and meta-analysis

Recent studies implicate single nucleotide polymorphisms (SNPs) within the 8q24 region as a risk factor for prostate cancer (PCa). New developments suggest that 8q24 encodes regulators of the nearby MYC gene, a known oncogene. In order to better understand the implications of SNPs in this region, we performed meta-analyses, stratified by race, of seven SNPs and one microsatellite marker previously identified as risk loci on the 8q24 region of the genome. In addition, we reviewed the literature examining the possible associations between these polymorphisms and clinicopathological features of PCa. The results of the meta-analyses indicate that rs6983267, rs1447295, rs6983561, rs7837688, rs16901979, and DG8S737 are significantly associated with a higher risk for PCa for at least one race, whereas the variants rs13254738 and rs7000448 are not. The degree of association and frequency of the causative allele varied among men of different races. Though several studies have demonstrated an association between certain 8q24 SNPs and clinicopathological features of the disease, review of this topic revealed conflicting results.

Association between variants on 8q24 and prostate cancer: A review and meta-analysis

28

Background: Racial disparities in the incidence prostate cancer exist but remain unexplained. Recent studies implicate single nucleotide polymorphisms (SNPs) within the 8q24 region as a risk factor for prostate cancer (PCa) and the frequency of variant alleles at these SNPs appear to differ by race. To determine the association between 8q24 polymorphisms and PCa among men of different races, we performed meta-analyses, stratified by race.

Methods: Twenty-nine studies of seven SNPs and one microsatellite marker located within the 8q24 region were included in the meta-analyses. Allelic odds ratio (OR) values and confidence intervals were calculated using the Mantel-Haenszel test. This test assumes homogeneity so we first used the Breslow-Day test to determine whether or not the assumption of homogeneity was valid in each population.

Results: PCa risk was associated with the following SNPs in all included races: rs6983267, rs1447295, rs6983561, rs7837688, rs16901979, and DG8S737(-8). PCa risk in Caucasians was conferred by rs6983267 (OR = 1.22 (1.17-1.27)), rs1447295 (OR = 1.43 (1.45-1.49)), rs6983561 (OR = 1.45 (1.30-1.61), rs7837688 (OR = 1.55 (1.39-1.73)), rs16902979 (OR = 1.39 (1.29-1.49)), and DG8S737(-8) (OR = 1.32 (1.12-1.56)). In African American men, a significant association was found for rs1447295 (OR = 1.1 (1.02-1.18)), rs6983561 (OR = 1.43 (1.29-1.59)), rs16901979 (OR = 1.39 (1.29-1.49)), and DG8S737(-8) (OR =1.34 (1.19-1.50)). Alleles associated with PCa risk in Asians were rs6983267 (OR = 1.15 (1.04-1.26)), rs1447295 (OR = 1.39 (1.25-1.54)), rs6983561 (OR = 1.68 (1.51-1.88)), and rs16901979 (OR = 1.65 (1.48-1.85)). The risk allele at rs1447295 was also associated with PCa risk among Hispanic men.

Conclusions: 8q24 contains SNPs that are associated with PCa risk, but the strength of this association depended on race. Racial disparities in the incidence of PCa may in part be accounted for by 8q24 variants.

Comparison of results from tests of association in unrelated individuals with uncollapsed and collapsed sequence variants using tiled regression

Tiled regression is an approach designed to determine the set of independent genetic variants that contribute to the variation of a quantitative trait in the presence of many highly correlated variants. In this study, we evaluate the statistical properties of the tiled regression method using the Genetic Analysis Workshop 17 data in unrelated individuals for traits Q1, Q2, and Q4. To increase the power to detect rare variants, we use two methods to collapse rare variants and compare the results with those from the uncollapsed data. In addition, we compare the tiled regression method to traditional tests of association with and without collapsed rare variants. The results show that collapsing rare variants generally improves the power to detect associations regardless of method, although only variants with the largest allelic effects could be detected. However, for traditional simple linear regression, the average estimated type I error is dependent on the trait and varies by about three orders of magnitude. The estimated type I error rate is stable for tiled regression across traits.

Abstract B28: Organic anion transporting polypeptide 1B3 as a novel biomarker for hypoxia in prostate cancer

The organic anion transporting polypeptide 1B3 (OATP1B3) is aberrantly expressed in prostate cancer. We showed that OATP1B3 expression correlated to Gleason score in primary prostate cancer samples. As a transporter, OATP1B3 functions to influx both endogenous small molecules and xenobiotics. We also demonstrated that decreased survival and decreased progression in patients with prostate cancer was associated with a polymorphism in SLCO1B3, the gene encoding OATP1B3. However, OATP1B3 has not been validated as a clinical biomarker and the cause of expression in cancer is unknown. The purpose of this study was to identify a molecular regulation that explains OATP1B3 expression in cancer. In this study, we show that hypoxia increases the transcriptional and translational expression of OATP1B3 in cancer, that hypoxia-inducible factor 1-alpha (HIF1-alpha) binds putative hypoxia response elements in the SLCO1B3 promoter region by chromatin immunoprecipitation, and show co-localization of hypoxia and OATP1B3 by immunohistochemistry in clinical tissue samples. Additionally, cooperation between androgen- and hypoxia-signaling pathways explains the increased expression of OATP1B3 in prostate cancer xenografts under castration conditions. These data provide a foundation for the use of OATP1B3 as a biomarker of cancerous disease.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr B28.

Genome-wide linkage scan for prostate cancer susceptibility in Finland: evidence for a novel locus on 2q37.3 and confirmation of signal on 17q21-q22

Genome-wide linkage studies have been used to localize rare and highly penetrant prostate cancer (PRCA) susceptibility genes. Linkage studies performed in different ethnic backgrounds and populations have been somewhat disparate, resulting in multiple, often irreproducible signals because of genetic heterogeneity and high sporadic background of the disease. Our first genome-wide linkage study and subsequent fine-mapping study of Finnish hereditary prostate cancer (HPC) families gave evidence of linkage to one region. Here, we conducted subsequent scans with microsatellites and SNPs in a total of 69 Finnish HPC families. GENEHUNTER-PLUS was used for parametric and nonparametric analyses. Our microsatellite genome-wide linkage study provided evidence of linkage to 17q12-q23, with a heterogeneity LOD (HLOD) score of 3.14 in a total of 54 of the 69 families. Genome-wide SNP analysis of 59 of the 69 families gave a highest HLOD score of 3.40 at 2q37.3 under a dominant high penetrance model. Analyzing all 69 families by combining microsatellite and SNP maps also yielded HLOD scores of > 3.3 in two regions (2q37.3 and 17q12-q21.3). These significant linkage peaks on chromosome 2 and 17 confirm previous linkage evidence of a locus on 17q from other populations and provide a basis for continued research into genetic factors involved in PRCA. Fine-mapping analysis of these regions is ongoing and candidate genes at linked loci are currently under analysis.

Organic anion transporter 2 (SLC22A7) is a facilitative transporter of cGMP

The second messenger, cGMP, mediates a host of cellular responses to various stimuli, resulting in the regulation of many critical physiologic functions. The existence of specific cGMP transporters on the plasma membrane that participate in the regulation of cGMP levels has been suggested in a large number of studies. In this study, we identified a novel plasma membrane transporter for cGMP. In particular, we showed that hOAT2 (SLC22A7), a member of the solute carrier (SLC) superfamily, was a facilitative transporter for cGMP and other guanine nucleotides. hOAT2, which is ubiquitously expressed at high levels in many cell types, was previously thought to primarily transport organic anions. Among purine and pyrimidine nucleobases, nucleosides, and nucleotides, hOAT2 showed the greatest preference for cGMP, which transported cGMP with a K(m) value of 88 +/- 11 muM and exhibited between 50- and 100-fold enhanced uptake over control cells. Our data revealed that hOAT2 is a bidirectional facilitative transporter that can control both intracellular and extracellular levels of cGMP. In addition, we observed that a common alternatively spliced variant of hOAT2 demonstrated a complete loss of transport function as a result of a low expression level on the plasma membrane. We conclude that hOAT2 is a highly efficient, facilitative transporter of cGMP and may be involved in cGMP signaling in many tissues. Our study suggests that hOAT2 represents a potential new drug target for regulating cGMP levels.

Validation of the Hartford nomogram in trauma surgery patients

OBJECTIVE

To validate the Hartford nomogram for once-daily aminoglycoside dosing in trauma surgery patients.

METHODS

A chart review was performed in trauma surgery patients who were started on once-daily aminoglycoside therapy. A peak aminoglycoside concentration was drawn 30 minutes after the end of the first or second infusion, and a random concentration was drawn approximately 10 hours after the dose. The 10-hour random concentration was used to validate the Hartford nomogram by predicting the actual dosing interval (determined by extrapolating the peak and random concentrations to achieve a trough concentration <1 mg/L). The percentage of intervals accurately predicted by the nomogram was determined.

RESULTS

Forty-nine patients (34 men and 15 women), age 43.0+/-15.9 y, total body weight 81.3+/-24.5 kg, ideal body weight 68.1+/-10.7 kg, dosing body weight (DBW) 72.0+/-14.4 kg, and estimated creatinine clearance [Cl(cr)] 89.5+/-20.6 mL/min/1.73 m2 were evaluated. Patients received 505+/-105 mg (7.0+/-0.4 mg/kg) of either gentamicin or tobramycin per dose. The concentration 30 minutes after the infusion was 22.4+/-5.9 mg/L, the concentration at the end of the dosing interval was 0.20+/-0.46 mg/L, the 10-hour random concentration was 2.6+/-1.8 mg/L, the elimination rate constant was 0.26+/-0.08 h(-1), the elimination half-life was 3.0+/-1.2 hours, and the volume of distribution was 19.9+/-7.9 L (0.28+/-0.09 L/kg of DBW). Ninety-eight percent (48/49) of the intervals were accurately predicted by the nomogram.

CONCLUSIONS

In trauma surgery patients with Cl(cr) of more than 60 mL/min/1.73 m2, the Hartford nomogram using a single random aminoglycoside concentration accurately predicted the same once-daily aminoglycoside intervals as determined by two concentrations. Less aggressive therapeutic drug monitoring in this patient subpopulation can lead to significant cost savings.

Clinical pharmacokinetics in the 21st century. Does the evidence support definitive outcomes?

Clinical pharmacokinetics emerged as a clinical discipline in the late 1960s and early 1970s. Clinical pharmacokinetic monitoring (CPM) helped many pharmacists to enter the clinical arena, but the focus was more on the pharmacists and tools. With the widespread acceptance of pharmaceutical care and patient-focused pharmacy, we now must take a sobering look at how clinical pharmacokinetics fits into the pharmaceutical care process. The existing literature is laden with articles that evaluate the effect of CPM on surrogate end-points. Many pharmacists have also had personal experiences that attest to the usefulness of CPM. Decreased mortality, decreased length of treatment, decreased length of hospital stay, decreased morbidity, and decreased adverse effects from drug therapy have been examined in an effort to measure and evaluate the impact of CPM on patient outcomes. While many of these studies demonstrated significant positive outcomes, several showed that CPM did not have a significant impact on specific patient outcomes. A few studies even found a negative impact on specific patient outcomes. Ultimately, there is good evidence in only a few specific patient groups to support the benefit of CPM. Despite the limitations of data supporting the routine use of CPM in managing drug therapy in diverse populations, many pharmacists continue to expend considerable time and effort in this activity. We need to define those patients who are most likely to benefit from CPM and incorporate this into our provision of pharmaceutical care, while minimising the time and money spent on CPM that provides no value. In redefining the patients who will benefit from CPM, we need to critically re-evaluate clinical studies on the relationship between drug concentration and response. Similarly, we need to pay special attention to recent studies evaluating the impact of CPM on outcomes in specific subpopulations. In the absence of specific studies demonstrating the value of CPM in particular patients, we propose that a more comprehensive decision-making process be undertaken that culminates in the quintessential question: 'Will the results of the drug assay make a significant difference in the clinical decision-making process and provide more information than sound clinical judgement alone?' We also need to consider opportunities to expand the use of CPM for new drugs and where new evidence suggests benefit. Even when there is strong evidence that CPM is useful in managing therapy in particular patient groups, clinicians need to remember that the therapeutic range is no more than a confidence interval and, therefore, we need to 'treat the patient and not the level'. We need to incorporate the patient-specific and outcome-oriented principles of pharmaceutical care into our CPM, even as we utilise CPM as an essential tool in pharmaceutical care.

Evaluation of aminoglycoside pharmacokinetics in postpartum patients using Bayesian forecasting

Many postpartum women have suboptimal serum concentrations after standard doses of aminoglycosides. The purpose of this study was to characterize the pharmacokinetics of aminoglycosides in postpartum patients through the use of Bayesian forecasting and to test the ability of these subpopulation parameters to predict actual aminoglycoside serum concentrations. In phase I, 28 postpartum patients who received empiric gentamicin therapy were identified and Bayesian subpopulation parameters generated. In phase II, additional gentamicin concentrations (peaks and troughs) were evaluated to test bias and precision of Bayesian subpopulation versus traditional estimates in predicting actual aminoglycoside serum concentrations. In phase I, 56 gentamicin serum concentrations in 28 patients, (age, 26 +/- 7 years; actual body weight [ABW], 84.3 +/- 18.4 kg; ideal body weight [IBW], 54.6 +/- 5.1 kg; dosing weight [DW], 66.3 +/- 9.4 kg; creatinine clearance [Clcr], 140.4 +/- 34.0 ml/min / 1.73 m2), were evaluated to calculate subpopulation pharmacokinetic parameters of volume of distribution (Vd) 0.29 +/- 0.07 l/kg (DW); elimination rate constant (ke) 0.29 +/- 0.05 h-1 and half-life (t1/2) 2.5 +/- 0.5 hours. In phase II, 50 gentamicin serum concentrations in 25 patients (age, 23 +/- 4 years; ABW 79.4 +/- 17.5 kg; IBW 55.0 +/- 7.3 kg; DW 64.8 +/- 9.6 kg; Clcr 139.7 +/- 29.3 ml/min/1.73 m2) were evaluated to calculate subpopulation pharmacokinetic parameters of Vd 0.30 +/- 0.04 l/kg (DW); ke 0.27 +/- 0.06 h-1; and t1/2 2.9 +/- 0.8 hours. Predictive performance tests (95% confidence intervals) demonstrate that subpopulation postpartum Bayesian parameters show greater precision for peak concentrations and less bias for trough concentrations than do traditional population estimates (p < 0.05). Definition of the Bayesian subpopulation parameters will allow us to dose aminoglycosides optimally in postpartum patients who have fragmented data.

Ondansetron use for smoking cessation

Cigarette smoking continues to make an important impact on the health status and costs of care in the US. Animal studies demonstrated that ondansetron is effective in decreasing withdrawal behaviour and have led to interest in its role in smoking cessation. One small trial tested the effects of ondansetron as an aid to change smoking behaviors. The results did not support a beneficial effect of ondansetron use. There were several limitations of this study, including small sample size and potentially inadequate duration of therapy and follow-up. An oral ondansetron formulation recently has become available. There are several disadvantages to an oral versus an intravenous formulation of ondansetron. Patients taking oral therapy are at less risk, the administration of an oral preparation does not require trained personnel, and a study can be performed in an environment in which the influences of daily living can affect smoking behavior (e.g., early morning, and after a meal). Ultimately, well-defined, large-scale clinical studies are necessary to determine whether ondansetron has a positive effect on smoking cessation.