Pharmacogenetic considerations in therapy with novel antiplatelet and anticoagulant agents.

Antiplatelets and anticoagulants are extensively used in cardiovascular medicine for the prevention and treatment of thrombosis in the venous and arterial circulations. Wide inter-individual variability has been observed in response to antiplatelets and anticoagulants, which triggered researchers to investigate the genetic basis of this variability. Data from extensive pharmacogenetic studies pointed to strong evidence of association between polymorphisms in candidate genes and the pharmacokinetics and pharmacodynamic action and clinical response of the antiplatelets clopidogrel and the anticoagulant warfarin. In this review, we conducted an extensive search on Medline for the time period of 2009-2023. We also searched the PharmGKB website for levels of evidence of variant-drug combinations and for drug labels and clinical guidelines. We focus on the pharmacogenetics of novel antiplatelets and anticoagulants while excluding acetylsalicylic acid, warfarin and heparins, and discuss the current knowledge with emphasis on the level of evidence.

Re-conceptualizing medical education in the post-COVID era.

PURPOSE: The COVID-19 pandemic has forced changes in the delivery of medical education. We aimed to explore these changes and determine whether they will impact the future of medical education in any way. METHODS: We invited leaders in medical education from all accessible US-based medical schools to participate in an online individual semi-structured interview. RESULTS: Representatives of 16 medical schools participated. They commented on the adequacy of online education for knowledge transfer, and the logistical advantages it offered, but decried its negative influence on social learning, interpersonal relationships and professional development of students, and its ineffectiveness for clinical education. Most participants indicated that they would maintain online learning for didactic purposes in the context of flipped classrooms but that a return to in-person education was essential for most other educational goals. Novel content will be introduced, especially in telemedicine and social medicine, and the students' roles and responsibilities in patient care and in curricular development may evolve in the future. CONCLUSIONS: This study is the first to document the practical steps that will be adopted by US medical schools in delivering medical education, which were prompted and reinforced by their experience during the COVID-19 pandemic.

Cross-Ancestry Genome-Wide Association Study Defines the Extended CYP2D6 Locus as the Principal Genetic Determinant of Endoxifen Plasma Concentrations.

The therapeutic efficacy of tamoxifen is predominantly mediated by its active metabolites 4-hydroxy-tamoxifen and endoxifen, whose formation is catalyzed by the polymorphic cytochrome P450 2D6 (CYP2D6). Yet, known CYP2D6 polymorphisms only partially determine metabolite concentrations in vivo. We performed the first cross-ancestry genome-wide association study with well-characterized patients of European, Middle-Eastern, and Asian descent (n = 497) to identify genetic factors impacting active and parent metabolite formation. Genome-wide significant variants were functionally evaluated in an independent liver cohort (n = 149) and in silico. Metabolite prediction models were validated in two independent European breast cancer cohorts (n = 287, n = 189). Within a single 1-megabase (Mb) region of chromosome 22q13 encompassing the CYP2D6 gene, 589 variants were significantly associated with tamoxifen metabolite concentrations, particularly endoxifen and metabolic ratio (MR) endoxifen/N-desmethyltamoxifen (minimal P = 5.4E-35 and 2.5E-65, respectively). Previously suggested other loci were not confirmed. Functional analyses revealed 66% of associated, mostly intergenic variants to be significantly correlated with hepatic CYP2D6 activity or expression (ρ = 0.35 to -0.52), and six hotspot regions in the extended 22q13 locus impacting gene regulatory function. Machine learning models based on hotspot variants (n = 12) plus CYP2D6 activity score (AS) increased the explained variability (~ 9%) compared with AS alone, explaining up to 49% (median R2 ) and 72% of the variability in endoxifen and MR endoxifen/N-desmethyltamoxifen, respectively. Our findings suggest that the extended CYP2D6 locus at 22q13 is the principal genetic determinant of endoxifen plasma concentration. Long-distance haplotypes connecting CYP2D6 with adjacent regulatory sites and nongenetic factors may account for the unexplained portion of variability.

C-peptide is a predictor of telomere shortening: A five-year longitudinal study.

Aim: Relative telomere length (RTL) predicts the development of many age-related diseases. Yet, few studies have evaluated their longitudinal effect on RTL. We investigated longitudinally the association between cardiometabolic risk factors and RTL. Methods: This was a longitudinal study with a 5-year follow-up period, based on data collected in 2014 and 2019. Of 478 participants in 2014, 198 consented to be followed-up in 2019. The associations between RTL and risk factors were analyzed using t-test, ANOVA or simple linear regression as applicable. Results: RTL was significantly shortened after 5 years (P<0.001). Older age (P=0.018) and gender (P=0.05) were significantly associated with shorter RTL at follow-up. Higher baseline C-peptide correlated with shorter RTL (P=0.04) and shortening of RTL (P=0.03) after 5 years. Multivariate linear regression including both age and gender revealed a significant trend for C-peptide and change in RTL after 5 years (P=0.04). Interestingly, there was a trend of shorter RTL at follow-up with diabetes, though the findings were not statistically significant. Conclusions: Higher C-peptide level contributes to telomere shortening over time, suggesting that metabolic dysregulation may play a role in early aging. Further understanding of this relationship and addressing high C-peptide levels can be important to prevent premature aging.

Pharmacogenetics in developing countries and low resource environments.

While significant advances have been made in pharmacogenetics (PGx), especially in countries with developed economies, this field remains at its infancy in developing countries and low resource environments. Herein, we provide insights into the gap and challenges of PGx at the research and clinical fronts, and some perspectives to bridge the gap and move forward with PGx in the developing world. We show that developing countries fall behind in PGx research, evidenced by a lower number of researchers, citations, and research output. In addition, the implementation of PGx in the clinic has been progressing at a much slower pace than research, and more so in developing countries. To bridge this gap, we recommend fostering regional and multinational collaborations to secure funds for high-throughput genotyping and local capacity building while preserving individual countries' identity, implementing next-generation sequencing, and organizing specialized training and exchange programs to move PGx research and clinical applications forward in developing countries.

Do Medical Students' Learning Styles and Approaches Explain Their Views and Behavior Regarding Lecture Attendance?

INTRODUCTION: Medical students' attendance at lectures, particularly in the preclinical years, has been steadily declining over the years. One of the many explanations offered for this observation is that students have different learning styles and approaches, such that not all of them benefit from attending lectures; however, no studies have specifically examined this possibility. While there is evidence against learning styles as affecting objective measures of learning, they are associated with subjective measures of learning and may therefore influence student behavior. We hypothesized that students' learning styles and/or approaches influence their views about the value and purpose of lectures and their motivation to attend them, which, in turn will affect their behavior. MATERIALS AND METHODS: A LimeSurvey was distributed to all preclinical students at the American University of Beirut. The survey included questions about demographic data, self-reported attendance rates in Year 1 of medical school, two validated and standardized questionnaires assessing the students' learning styles (visual, auditory, kinesthetic, tactile, group, individual) and learning approaches (superficial, deep, strategic), and a series of questions exploring the students' views about the purpose and value of lectures and their motivation to attend lectures. RESULTS: No associations were found between learning styles or approaches and attendance rates, but this may have been confounded by the mandatory attendance policy at the time. There were, however, a few positive associations between some learning styles or approaches and the students' views about the value of attending lectures. In particular, students with high scores as auditory learners tended to see absolutely no value in attending lectures, and those with high scores as group, auditory or visual learners, tended to see less value in taking their own notes in lectures. Students with superficial approaches to learning felt that watching videos of a lecture provides equivalent education to attending a lecture. There were no statistically significant associations with either the perceived purpose of lectures or the motivation to attend lectures after correction for multiple testing. CONCLUSIONS: This study reveals that except for some interesting findings related to auditory learners, differences in learning styles or approaches among students cannot adequately explain differences in their attitudes, and likely, behavior, regarding lecture attendance. The idea that learning styles and approaches can influence educational preferences and outcomes, while attractive and intuitive, continues to require supporting evidence. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s40670-021-01362-3.

A GRIN3A polymorphism may be associated with glucocorticoid-induced symptomatic osteonecrosis in children with acute lymphoblastic leukemia.

Aim: To evaluate the association between candidate genetic polymorphisms and glucocorticoid-induced osteonecrosis in Arab children treated for acute lymphoblastic leukemia. Methods: A total of 189 children treated for acute lymphoblastic leukemia were genotyped for four SNPs with allele discrimination assays. The incidence and timing of radiologically confirmed symptomatic grade 4 osteonecrosis were classified based on the Ponte di Legno toxicity working group consensus definition. Results: Thirteen children developed grade 4 osteonecrosis (6.8%), of whom 12 received the intermediate/high-risk treatment protocol. GRIN3A variant allele carriers had to stop dexamethasone therapy earlier resulting in significantly shorter duration of dexamethasone treatment (mean [95% CI]: 75.17 [64.28-86.06] vs 85.90 [81.22-90.58] weeks; p = 0.054) and lower cumulative dose (mean [95% CI]: 1118.11 [954.94-1281.29] vs 1341.14 [1264.17-1418.11] mg/m2; p = 0.011). Conclusion: This is the first pharmacogenomics evaluation of the association between GRIN3A variants and glucocorticoid-induced osteonecrosis in Arab children.

Lay abstract This study aimed at uncovering variants in the genetic material of Arab children, that might predispose them to develop a specific treatment-related adverse effect, during their therapy for acute lymphoblastic leukemia (a type of blood cancer). We looked at specific changes in the DNA of our patient cohort that might predispose them to develop treatment-induced osteonecrosis. Osteonecrosis is by definition a loss of blood flow to the bone tissue in one's body, causing the bone to die. Osteonecrosis may be caused by long-term exposure to steroid-based medication, among which dexamethasone. Dexamethasone a main component of the combination of chemotherapeutic agents used to treat acute lymphoblastic leukemia. Our findings suggested that children who had one of the variants detected in a specific location of DNA, the GRIN3A gene, were more likely to develop osteonecrosis earlier and had to stop dexamethasone earlier during therapy.

A Signature of Four Circulating microRNAs as Potential Biomarkers for Diagnosing Early-Stage Breast Cancer.

Breast cancer (BC) is the most predominant type of cancer among women. The aim of this study is to find new biomarkers that can help in early detection of BC, especially for those who are too young to be screened using mammography as per guidelines. Using microRNA microarray, we previously showed dysregulation of 74 microRNAs in tumors from early BC patients as compared with normal adjacent tissues, which we were interested in studying in blood circulation. In this study, we investigated the expression of 12 microRNA (miR-21/miR-155/miR-23a/miR-130a/miR-145/miR-425-5p/miR-139-5p/miR-451/miR-195/miR-125b/miR-100, and miR-182) in the plasma of 41 newly diagnosed Lebanese BC patients with early invasive ductal carcinoma as compared with 32 healthy controls. Total RNA was extracted from plasma, and expression levels of miRNA of interest were measured using RT-qPCR followed by statistical analysis; miR-21, miR-155, miR-23a, miR-130a, miR-145, miR-425-5p, and miR-139-5p were significantly upregulated and miR-451 was significantly downregulated, in the plasma of BC patients as compared with healthy controls. The positively correlated miR-23a, miR-21, and miR-130a had a high diagnostic accuracy (86%). Importantly, the combination of miR-145/miR-425-5p/miR-139-5p/miR-130a scored the highest diagnostic accuracy of 95% with AUC = 0.97 (sensitivity 97% and specificity 91%). MicroRNAs are promising non-invasive diagnostic biomarkers for early-stage BC with the panel of miR-145/miR-425-5p/miR-139-5p/miR-130a having the highest diagnostic accuracy.

LINE-1 methylation mediates the inverse association between body mass index and breast cancer risk: A pilot study in the Lebanese population.

INTRODUCTION: Lebanon is among the top countries worldwide in combined incidence and mortality of breast cancer, which raises concern about risk factors peculiar to this country. The underlying molecular mechanisms of breast cancer require elucidation, particularly epigenetics, which is recognized as a molecular sensor to environmental exposures. PURPOSE: We aim to explore whether DNA methylation levels of AHRR (marker of cigarette smoking), SLC1A5 and TXLNA (markers of alcohol consumption), and LINE-1 (a genome-wide repetitive retrotransposon) can act as molecular mediators underlying putative associations between breast cancer risk and pertinent extrinsic (tobacco smoking and alcohol consumption) and intrinsic factors [age and body mass index (BMI)]. METHODS: This is a cross-sectional pilot study which includes breast cancer cases (N = 65) and controls (N = 54). DNA methylation levels were measured using bisulfite pyrosequencing on available peripheral blood samples (N = 119), and Multivariate Imputation by Chained Equations (MICE) was used to impute missing DNA methylation values in remaining samples. Multiple mediation analysis was performed to assess direct and indirect (via DNA methylation) effects of intrinsic and extrinsic factors on breast cancer risk. RESULTS: In relation to exposure, AHRR hypo-methylation was associated with cigarette but not waterpipe smoking, suggesting potentially different biomarkers of these two forms of tobacco use; SLC1A5 and TXLNA methylation were not associated with alcohol consumption; LINE-1 methylation was inversely associated with BMI (ß-value [95% confidence interval (CI)] = -0.04 [-0.07, -0.02]), which remained significant after adjustment for age, smoking and alcohol consumption. In relation to breast cancer, there was no detectable association between AHRR, SLC1A5 or TXLNA methylation and cancer risk, but LINE-1 methylation was significantly higher in breast cancer cases when compared to controls (mean ± SD: 72.00 ± 0.66 versus 70.89 ± 0.73, P = 4.67 × 10-14). This difference remained significant after adjustment for confounders (odds ratio (OR) [95% CI] = 9.75[3.74, 25.39]). Moreover, LINE-1 hypo-methylation mediated 83% of the inverse effect of BMI on breast cancer risk. CONCLUSION: This pilot study demonstrates that alterations in blood LINE-1 methylation mediate the inverse effect of BMI on breast cancer risk. This warrants large scale studies and stratification based on clinic-pathological types of breast cancer.

The Role of Angiotensin Converting Enzyme 1 Insertion/Deletion Genetic Polymorphism in the Risk and Severity of COVID-19 Infection.

Background: Individuals infected with the COVID-19 virus present with different symptoms of varying severity. In addition, not all individuals are infected despite exposure. Risk factors such as age, sex, and comorbidities play a major role in this variability; however, genetics may also be important in driving the differences in the incidence and prognosis of the disease. An Insertion/Deletion (I/D) polymorphism in the ACE1 gene (rs1799752) may explain these genetic differences. The aims of this study were to determine the potential role of ACE1 I/D genetic polymorphism in the risk of contracting COVID-19 as well as predicting the severity of COVID-19 infection. Methods: Three-hundred and eighty-seven non-related Lebanese subjects, 155 controls and 232 cases, who presented to the American University of Beirut Medical Center (AUBMC) for COVID-19 PCR testing were recruited. Clinical data were collected via filling a questionnaire and accessing the medical records. Peripheral blood was withdrawn for DNA isolation, and genotyping performed with standard PCR followed by band visualization on agarose gel. Results: In our study population, previously described risk factors such as gender, age, and comorbidities were associated with increase in disease susceptibility and severity. ACE1 I was the least common allele, and there was a positive association between ACE1 I and the risk of contracting the COVID-19 disease. More specifically, the frequency of II genotype was significantly higher among cases when compared to controls (P = 0.035) with individuals with the II genotype having greater risk for contracting the COVID-19 disease: OR = 2.074, P = 0.048 in the multivariate analysis. As for disease severity, the DD genotype and D allele were associated with increased risk for developing severe symptoms (OR = 2.845, P = 0.026 and OR = 2.359, P = 0.014, respectively), and the DD genotype with necessitating hospitalization (OR = 2.307, P = 0.042). In parallel, D allele carriers showed a significantly increased risk for developing hypoxia: OR = 4.374, P = 0.045. Conclusion: We found a positive association between ACE1 I and the risk of contracting the COVID-19 disease, and between ACE1 D and a worse outcome of the COVID-19 infection. Therefore, genotyping for ACE1 I/D polymorphism could be used to assess risk and predict severity for better prognosis and management of the disease.

Knowledge, beliefs, and practices related to cancer screening and prevention in Lebanon: community and social media users' perspectives.

OBJECTIVE: Common to many countries in the Middle East, Lebanon has an increasing cancer burden; however, national screening programs are limited to breast cancer. The literature on cancer screening practices and beliefs is scarce. This cross-sectional study investigates the knowledge, beliefs, and practices related to the prevention and screening for breast, cervical, colon, lung, and skin cancers among Lebanese residents, recruited through social media advertisements and community outreach activities. METHODS: Participants filled an anonymous questionnaire either via a web-based interface or using tablets distributed at primary health clinics. The characteristics of the two cohorts were compared with chi-square and t-tests. We performed descriptive analysis, followed by multivariate logistic regression for predictors of cancer screening. RESULTS: A total of 407 participants completed the survey online, and 262 filled the study in tablets available at primary care clinics. The two samples were significantly different in terms of age, education, and perceived socioeconomic status. Online participants demonstrated higher knowledge and higher participation in screening practices than their counterparts recruited through community outreach. Mammography (44.7% online and 39.9% in-person), and cervical cancer screening (44.5% online and 36.7% community) had the highest participation rates. In both samples, participants who were older and more educated were more likely to report engagement with cancer screening practices. CONCLUSIONS: Our study revealed significant knowledge gaps in cancer prevention and screening. Different sampling techniques accessed diverse populations, highlighting the need for educational messages and targeted screening programs to be inclusive of socio-economically disadvantaged communities with low education and health literacy.

Effect of Targeted Curricular Reform on the Learning Environment, Student Empathy, and Hidden Curriculum in a Medical School: A 7-Year Longitudinal Study.

OBJECTIVE: The American University of Beirut Faculty of Medicine follows the American model of medical education. In 2013-2014, a carefully designed new curriculum replaced the previous, largely traditional curriculum, and aimed to improve student wellbeing, upgrade the learning environment, enhance student empathy, and counter the negative influences of the hidden curriculum. This longitudinal study assessed the effectiveness of the new curriculum in those domains over a period of 7 years. METHODS: Three cohorts of medical students anonymously filled a paper-based survey at the end of years 1, 2, 3, and 4 of the 4-year curriculum. These included the Class of 2016, the last batch of students who followed the old curriculum, and 2 cohorts that followed the new curriculum (Class of 2017 and Class of 2019). The perceived learning environment was assessed by the Dundee Ready Education Environment Measurement survey; the student's empathy was assessed by the Jefferson Scale of Physician Empathy-Student version; and the hidden curriculum was examined using a locally developed survey. RESULTS: The scores on the learning environment survey were significantly higher among the cohorts following the new curriculum relative to those following the old curriculum. Similar significant results appeared when looking at each of the subscales for the learning environment. The students' empathy scores were also significantly higher in both cohorts of the new curriculum when compared with the old curriculum. Nevertheless, there was a significant decrease in empathy in both third and fourth years relative to second year. The new curriculum also improved aspects of the students' perceptions and responses to the hidden curriculum. CONCLUSION: In conclusion, a well-planned and well-researched curricular intervention, based on sound educational theories, practices, and standards can indeed transform the learning environment, as well as the attitudes, values, and experiences of medical students.

Implementation of Pharmacogenetics to Individualize Treatment Regimens for Children with Acute Lymphoblastic Leukemia.

Despite major advances in the management and high cure rates of childhood acute lymphoblastic leukemia (ALL), patients still suffer from many drug-induced toxicities, sometimes necessitating dose reduction, or halting of cytotoxic drugs with a secondary risk of disease relapse. In addition, investigators have noted significant inter-individual variability in drug toxicities and disease outcomes, hence the role of pharmacogenetics (PGx) in elucidating genetic polymorphisms in candidate genes for the optimization of disease management. In this review, we present the PGx data in association with main toxicities seen in children treated for ALL in addition to efficacy, with a focus on the most plausible germline PGx variants. We then follow with a summary of the highest evidence drug-gene annotations with suggestions to move forward in implementing preemptive PGx for the individualization of treatment regimens for children with ALL.

Obesity Alters Endoxifen Plasma Levels in Young Breast Cancer Patients: A Pharmacometric Simulation Approach.

Endoxifen is one of the most important metabolites of the prodrug tamoxifen. High interindividual variability in endoxifen steady-state concentrations (CSS,min ENDX ) is observed under tamoxifen standard dosing and patients with breast cancer who do not reach endoxifen concentrations above a proposed therapeutic threshold of 5.97 ng/mL may be at a 26% higher recurrence risk compared with patients with endoxifen concentrations exceeding this value. In this investigation, 10 clinical tamoxifen studies were pooled (1,388 patients) to investigate influential factors on CSS,min ENDX using nonlinear mixed-effects modeling. Age and body weight were found to significantly impact CSS,min ENDX in addition to CYP2D6 phenotype. Compared with postmenopausal patients, premenopausal patients had a 30% higher risk for subtarget CSS,min ENDX at tamoxifen 20 mg per day. In treatment simulations for distinct patient subpopulations, young overweight patients had a 3.1-13.8-fold higher risk for subtarget CSS,min ENDX compared with elderly low-weight patients. Considering ever-rising obesity rates and the clinical importance of tamoxifen for premenopausal patients, this subpopulation may benefit most from individualized tamoxifen dosing.

Effect of bisphenols on telomerase expression and activity in breast cancer cell lines.

Bisphenol A (BPA), a monomer of polycarbonates and resins, was shown to induce the expression of telomerase enzyme which has been associated with breast cancer development and progression. However, the effects of BPA analogues, bisphenol F (BPF) and bisphenol S (BPS) on telomere-linked pathway have not been evaluated. Herein, MCF-7 (estrogen receptor (ER)-positive) and MDA-MB-231 (ER-negative) cells were treated with BPA, BPF and BPS ± estrogen receptor inhibitor (ERI), for 24 and/or 48 h. RNA expression and enzymatic activity of telomerase were measured using reverse transcription quantitative polymerase chain reaction (RT-qPCR) and telomeric repeat amplification protocol (TRAP); respectively. Relative telomere length (RTL) was also measured using quantitative PCR. After 24 h, the three bisphenols resulted in a 2-3 folds increase in expression and activity of telomerase in MCF-7 but not in MDA-MB-231 cells, and this increase was prevented upon co-treatment with ERI. The observed increase in the expression and activity of telomerase after 24 h of treatment with bisphenols was associated with differential and modest ER-dependent lengthening in RTL at 48 h. Our results show that telomerase potentially mediates the effects of the three bisphenols in ER-positive breast carcinoma. Hence, further investigation is warranted to elucidate the telomerase-linked pathways that could underlie bisphenol-related effects.

Factors That Determine the Perceived Effectiveness of Peer Feedback in Collaborative Learning: a Mixed Methods Design.

INTRODUCTION: Peer assessment has been promoted as a valuable approach to formative assessment to support learning and peer professionalism. This mixed methods study employed a conceptual framework to explore the factors that enhance the perceived effectiveness of formative peer assessment in the context of team-based learning as a form of collaborative learning. MATERIALS AND METHODS: The volume and quality of written peer comments of two medical school classes at three time points were analyzed. Focus groups were then conducted to clarify issues that appeared in the quantitative data and to explore other emerging dimensions. RESULTS: There was a notable deficiency in both the volume and quality of the comments provided, with no improvement over time. Several factors were identified, including some that are logistical and operational and can be corrected easily, such as the timing of the assignments. Others that stood out as major substantive issues and/or limitations related to the students' conceptions of the purpose of the peer assessment and to their interpersonal variables. DISCUSSION: There were social disincentives for students to provide constructive feedback to peers with whom a continuing working relationship is necessary. There was also an inconsistency between the quality of the peer feedback being typically shallow and lacking in substance, and students considering it beneficial. CONCLUSION: The findings identify factors that need to be addressed in order to ensure the quality and effectiveness of formative peer assessment among medical students.

ITPA, TPMT, and NUDT15 Genetic Polymorphisms Predict 6-Mercaptopurine Toxicity in Middle Eastern Children With Acute Lymphoblastic Leukemia.

Background: Acute lymphoblastic leukemia (ALL) is the most common cancer seen in children worldwide and in the Middle East. Although there have been major advances in treatment approaches for childhood ALL, serious toxicities do occur but with significant inter-individual variability. The aim of this study is to measure the frequency of polymorphisms in candidate genes involved in 6-Mercaptopurine (6-MP) disposition in a combined cohort of Middle Eastern Children with ALL, and evaluate whether these polymorphisms predict 6-MP intolerance and toxicity during ALL maintenance therapy. Methods: The study includes children treated for ALL on two treatment protocols from two cohorts; one from Lebanon (N = 136) and another from Kurdistan province of Iran (N = 74). Genotyping for the following six candidate genetic polymorphisms: ITPA 94C > A (rs1127354) and IVS2+21A > C (rs7270101), TPMT*2 238G > C (rs1800462), TPMT*3B 460G > A (rs1800460) and *3C 719A > G (rs1142345), and NUDT15 415C > T (rs116855232) was performed and analyzed in association with 6-MP dose intensity and toxicity. Results: As expected, TPMT and NUDT15 variants were uncommon. As for ITPA, both polymorphisms were more common in the Lebanese as compared to the Kurdish cohort with a minor allele frequency of 0.05 for 94C > A and 0.14 for IVS2+21A > C in the Lebanese only (N = 121), and of 0.01 for either ITPA polymorphism in Kurds. The most significant toxic effects were depicted with the NUDT15 polymorphism with a median 6-MP dose intensity of 33.33%, followed by 46.65% for TPMT*3A polymorphism, followed by 65.33% for two ITPA risk allele carriers and 74% for one ITPA risk allele carriers, in comparison to a median of 100% for the homozygous wild type in the combined cohort (P < 0.001). In addition, the onset of febrile neutropenia was significantly higher in variant allele carriers in the combined cohorts. Conclusions: These data confirm the predictive role of TPMT, NUDT15, and ITPA in 6-MP intolerance in Middle Eastern children with ALL. Given the relatively high frequency of ITPA variants in our study and their significant association with 6-MP dose intensity, we recommend that physicians consider genotyping for ITPA variants in conjunction with TPMT and NUDT15 prior to 6-MP therapy in these children.

Genetic polymorphisms in candidate genes are not associated with increased vincristine-related peripheral neuropathy in Arab children treated for acute childhood leukemia: a single institution study.

OBJECTIVE: The aim of this study was to evaluate the potential association between candidate genetic polymorphisms and vincristine-related peripheral neuropathy in Arab children with acute lymphoblastic leukemia (ALL). PATIENTS AND METHODS: This is a retrospective evaluation of 133 Arab children treated for ALL at the Children's Cancer Center of Lebanon. Incidence and severity of, as well as the timing (in weeks) at which grade 2 or higher peripheral neuropathy occurred were recorded. Genotyping for ABCB1 (rs1045642), ABCB1 (rs1128503), ABCC2 (rs717620), CEP72 (rs924607), ETAA1 (rs17032980), and MTNR1B (rs12786200) was performed. RESULTS: A total of 26 (19.5%) individuals developed peripheral neuropathy, three of which occurred during the induction phase. No statistically significant associations were revealed for any of the polymorphisms with either incidence of vincristine-related toxicity, toxicity severity, or time to the first episode of grade 2 or higher vincristine-related peripheral neuropathy. CONCLUSION: This study presents the first pharmacogenetic analysis of vincristine-related peripheral neuropathy in children with ALL in an Arab country. We have shown that genetic polymorphisms in candidate genes are not associated with peripheral neuropathy secondary to chronic therapy with high-dose vincristine (2 mg/m) during the continuation phase. Concerning CEP72, our results are in line with the findings from the St Jude cohort of children treated for ALL with higher vincristine doses during chronic treatment. Larger high-throughput genetic analyses may be warranted to evaluate variants in other candidate genes such as CYP3A5 and reveal new nonpreviously reported alleles that may be peculiar to this region of the world.