Understanding the impact of ABCG2 polymorphisms on drug pharmacokinetics: focus on rosuvastatin and allopurinol.

INTRODUCTION: In addition to the well-established understanding of the pharmacogenetics of drug-metabolizing enzymes, there is growing data on the effects of genetic variation in drug transporters, particularly ATP-binding cassette (ABC) transporters. However, the evidence that these genetic variants can be used to predict drug effects and to adjust individual dosing to avoid adverse events is still limited. AREAS COVERED: This review presents a summary of the current literature from the PubMed database as of February 2024 regarding the impact of genetic variants on ABCG2 function and their relevance to the clinical use of the HMG-CoA reductase inhibitor rosuvastatin and the xanthine oxidase inhibitor allopurinol. EXPERT OPINION: Although there are pharmacogenetic guidelines for the ABCG2 missense variant Q141K, there is still some conflicting data regarding the clinical benefits of these recommendations. Some caution appears to be warranted in homozygous ABCG2 Q141K carriers when rosuvastatin is administered at higher doses and such information is already included in the drug label. The benefit of dose adaption to lower possible side effects needs to be evaluated in prospective clinical studies.

BTK acts as a modulator of the response to imatinib in chronic myeloid leukemia.

The use of tyrosine kinase inhibitors, such as imatinib, against the chronic myeloid leukemia (CML)-causing kinase BCR::ABL1 has become the model for successful targeted therapy. Nevertheless, drug resistance remains a clinical problem. Analysis of genome-wide expression and genetic aberrations of an in vitro imatinib-resistant CML cell line revealed downregulation of Bruton's tyrosine kinase (BTK), predominantly associated with B cell malignancies, and a novel BTK kinase domain variant in imatinib resistance. This raised the question of the role of BTK in imatinib-resistant CML. In the present study, BTK downregulation and the presence of the BTK variant c.1699_1700delinsAG p.(Glu567Arg) were confirmed in imatinib resistance in vitro. Similarly, BTK inhibition or small interfering RNA-mediated BTK knockdown reduced imatinib susceptibility by 84 and 71%, respectively. BTK overexpression was detrimental to CML cells, as proliferation was significantly reduced by 20.5% under imatinib treatment. In addition, BTK rescue in imatinib-resistant cells restored imatinib sensitivity. The presence of the BTK p.(Glu567Arg) variant increased cell numbers (57%) and proliferation (37%) under imatinib exposure. These data demonstrate that BTK is important for the development of imatinib resistance in CML: Its presence increased drug response, while its absence promotes imatinib resistance. Moreover, the BTK p.(Glu567Arg) variant abrogates imatinib sensitivity. These findings demonstrate a context-dependent role for BTK as an oncogene in B cell malignancies, but as a tumor suppressor in other neoplasms.

Molecular biomarkers of leukemia: convergence-based drug resistance mechanisms in chronic myeloid leukemia and myeloproliferative neoplasms.

Leukemia represents a diverse group of hematopoietic neoplasms that can be classified into different subtypes based on the molecular aberration in the affected cell population. Identification of these molecular classification is required to identify specific targeted therapeutic approaches for each leukemic subtype. In general, targeted therapy approaches achieve good responses in some leukemia subgroups, however, resistance against these targeted therapies is common. In this review, we summarize molecular drug resistance biomarkers in targeted therapies in BCR::ABL1-driven chronic myeloid leukemia (CML) and JAK2-driven myeloproliferative neoplasms (MPNs). While acquisition of secondary mutations in the BCR::ABL1 kinase domain is the a common mechanism associated with TKI resistance in CML, in JAK2-driven MPNs secondary mutations in JAK2 are rare. Due to high prevalence and lack of specific therapy approaches in MPNs compared to CML, identification of crucial pathways leading to inhibitor persistence in MPN model is utterly important. In this review, we focus on different alternative signaling pathways activated in both, BCR::ABL1-mediated CML and JAK2-mediated MPNs, by combining data from in vitro and in vivo-studies that could be used as potential biomarkers of drug resistance. In a nutshell, some common similarities, especially activation of PDGFR, Ras, PI3K/Akt signaling pathways, have been demonstrated in both leukemias. In addition, induction of the nucleoprotein YBX1 was shown to be involved in TKI-resistant JAK2-mediated MPN, as well as TKI-resistant CML highlighting deubiquitinating enzymes as potential biomarkers of TKI resistance. Taken together, whole exome sequencing of cell-based or patients-derived samples are highly beneficial to define specific resistance markers. Additionally, this might be helpful for the development of novel diagnostic tools, e.g., liquid biopsy, and novel therapeutic agents, which could be used to overcome TKI resistance in molecularly distinct leukemia subtypes.

Encouraging medical students to become surgeons? Impact of psychological and surgical factors on career choice at medical school.

Aim: Training decisions are viewed as a problem by the majority of medical students.In the present study we compared sociodemographic and psychological characteristics of students who are interested in surgical training to those who preferred a non-surgical specialty. Furthermore, we examined whether students who wish to be trained as surgeons performed better than their non-surgical counterparts in a course designed to acquire skills in minimally invasive surgery. Method: From October 2020 to January 2021 we performed a cross-sectional survey among 116 medical students prior to their year of practical training at Christian-Albrechts University in Kiel. Based on their intended field of specialization, the students were divided into a non-surgical and a surgical group. Sociodemographic and psychological characteristics such as self-efficacy expectations, resilience and stress perception were evaluated and compared between groups. Simultaneously, we compared their surgical performance in two laparoscopic exercises and their self-assessment as surgeons. Statistical differences between the training groups were determined by the Mann-Whitney U test or Pearson's Chi square test. Results: Ninety-two students participated in the study, of whom 64.1% intended to train in a non-surgical specialty and 35.9% in a surgical specialty. Students who wished to be trained as surgeons had higher general self-efficacy expectations (p<0.001) and greater resilience (p=0.009). However, on comparison they had a lower stress level (p=0.047). The inter-group comparison of training results and self-assessment as surgeons revealed no unequivocal differences in surgical performance. Conclusion: Interest in surgical specialties is correlated, among other factors, with the strength of psychological skills such as general self-efficacy expectations, resilience and stress perception. Early attention to these psychological resources in academic training might assist medical students in future career choices.

Phenotype-Genotype Correlation Applying a Cocktail Approach and an Exome Chip Analysis Reveals Further Variants Contributing to Variation of Drug Metabolism.

Although great progress has been made in the fine-tuning of diplotypes, there is still a need to further improve the predictability of individual phenotypes of pharmacogenetically relevant enzymes. The aim of this study was to analyze the additional contribution of sex and variants identified by exome chip analysis to the metabolic ratio of five probe drugs. A cocktail study applying dextromethorphan, losartan, omeprazole, midazolam, and caffeine was conducted on 200 healthy volunteers. CYP2D6, 2C9, 2C19, 3A4/5, and 1A2 genotypes were analyzed and correlated with metabolic ratios. In addition, an exome chip analysis was performed. These SNPs correlating with metabolic ratios were confirmed by individual genotyping. The contribution of various factors to metabolic ratios was assessed by multiple regression analysis. Genotypically predicted phenotypes defined by CPIC discriminated very well the log metabolic ratios with the exception of caffeine. There were minor sex differences in the activity of CYP2C9, 2C19, 1A2, and CYP3A4/5. For dextromethorphan (CYP2D6), IP6K2 (rs61740999) and TCF20 (rs5758651) affected metabolic ratios, but only IP6K2 remained significant after multiple regression analysis. For losartan (CYP2C9), FBXW12 (rs17080138), ZNF703 (rs79707182), and SLC17A4 (rs11754288) together with CYP diplotypes, and sex explained 50% of interindividual variability. For omeprazole (CYP2C19), no significant influence of CYP2C:TG haplotypes was observed, but CYP2C19 rs12777823 improved the predictability. The comprehensive genetic analysis and inclusion of sex in a multiple regression model significantly improved the explanation of variability of metabolic ratios, resulting in further improvement of algorithms for the prediction of individual phenotypes of drug-metabolizing enzymes.

Tuning of liver circadian transcriptome rhythms by thyroid hormone state in male mice.

Thyroid hormones (THs) are important regulators of systemic energy metabolism. In the liver, they stimulate lipid and cholesterol turnover and increase systemic energy bioavailability. It is still unknown how the TH state interacts with the circadian clock, another important regulator of energy metabolism. We addressed this question using a mouse model of hypothyroidism and performed circadian analyses. Low TH levels decreased locomotor activity, food intake, and body temperature mostly in the active phase. Concurrently, liver transcriptome profiling showed only subtle effects compared to elevated TH conditions. Comparative circadian transcriptome profiling revealed alterations in mesor, amplitude, and phase of transcript levels in the livers of low-TH mice. Genes associated with cholesterol uptake, biosynthesis, and bile acid secretion showed reduced mesor. Increased and decreased cholesterol levels in the serum and liver were identified, respectively. Combining data from low- and high-TH conditions allowed the identification of 516 genes with mesor changes as molecular markers of the liver TH state. We explored these genes and created an expression panel that assesses liver TH state in a time-of-day dependent manner. Our findings suggest that the liver has a low TH action under physiological conditions. Circadian profiling reveals genes as potential markers of liver TH state.

Liver microRNA transcriptome reveals miR-182 as link between type 2 diabetes and fatty liver disease in obesity.

Background: The development of obesity-associated comorbidities such as type 2 diabetes (T2D) and hepatic steatosis has been linked to selected microRNAs in individual studies; however, an unbiased genome-wide approach to map T2D induced changes in the miRNAs landscape in human liver samples, and a subsequent robust identification and validation of target genes are still missing. Methods: Liver biopsies from age- and gender-matched obese individuals with (n=20) or without (n=20) T2D were used for microRNA microarray analysis. The candidate microRNA and target genes were validated in 85 human liver samples, and subsequently mechanistically characterized in hepatic cells as well as by dietary interventions and hepatic overexpression in mice. Results: Here, we present the human hepatic microRNA transcriptome of type 2 diabetes in liver biopsies and use a novel seed prediction tool to robustly identify microRNA target genes, which were then validated in a unique cohort of 85 human livers. Subsequent mouse studies identified a distinct signature of T2D-associated miRNAs, partly conserved in both species. Of those, human-murine miR-182-5 p was the most associated with whole-body glucose homeostasis and hepatic lipid metabolism. Its target gene LRP6 was consistently lower expressed in livers of obese T2D humans and mice as well as under conditions of miR-182-5 p overexpression. Weight loss in obese mice decreased hepatic miR-182-5 p and restored Lrp6 expression and other miR-182-5 p target genes. Hepatic overexpression of miR-182-5 p in mice rapidly decreased LRP6 protein levels and increased liver triglycerides and fasting insulin under obesogenic conditions after only seven days. Conclusions: By mapping the hepatic miRNA-transcriptome of type 2 diabetic obese subjects, validating conserved miRNAs in diet-induced mice, and establishing a novel miRNA prediction tool, we provide a robust and unique resource that will pave the way for future studies in the field. As proof of concept, we revealed that the repression of LRP6 by miR-182-5 p, which promotes lipogenesis and impairs glucose homeostasis, provides a novel mechanistic link between T2D and non-alcoholic fatty liver disease, and demonstrate in vivo that miR-182-5 p can serve as a future drug target for the treatment of obesity-driven hepatic steatosis. Funding: This work was supported by research funding from the Deutsche Forschungsgemeinschaft (KI 1887/2-1, KI 1887/2-2, KI 1887/3-1 and CRC-TR296), the European Research Council (ERC, CoG Yoyo LepReSens no. 101002247; PTP), the Helmholtz Association (Initiative and Networking Fund International Helmholtz Research School for Diabetes; MB) and the German Center for Diabetes Research (DZD Next Grant 82DZD09D1G).