Dihydropyrimidine Dehydrogenase Research Articles

Dihydropyrimidine dehydrogenase (DPD), encoded by DPYD, is a key enzyme in pyrimidine catabolism, and its deficiency leads to severe toxicity in patients treated with 5-fluorouracil (5-FU). While pathogenic DPYD variants account for many cases of DPD deficiency, they do not fully explain all instances of 5-FU sensitivity, suggesting additional genetic factors are involved. Recent studies have implicated variants in CIAO1, a gene encoding a subunit of the cytosolic iron-sulfur (Fe-S) cluster assembly targeting complex, in reducing DPD stability and function. In this study, we established a C. elegans model to assess DPD deficiency and 5-FU sensitivity. Using a dpyd-1 knockout and CRISPR-generated ciao-1 variants that mirror patient-derived variants (p.Trp184Cys, p.His193Tyr, and p.Arg65Trp), we provide the first in vivo evidence that pathogenic variants in CIA complex components can lead to DPD deficiency and, consequently, heightened 5-FU toxicity. Our findings highlight the critical role of CIAO1 in DPD function and 5-FU tolerance, expanding the genetic landscape of DPD deficiency and offering a robust platform for functional evaluation of pathogenic variants.

PreTA-mediated metabolism of 5-fluorouracil by intratumoral Citrobacter freundii drives chemoresistance in pancreatic cancer.

5-Fluorouracil (5-FU) and its prodrug, capecitabine, are widely used in chemotherapy for various cancers, including colorectal, breast, and gastrointestinal malignancies. While their common toxicities are well documented, uncommon, and severe side effects, such as cardiotoxicity, neurotoxicity, and hyperammonemia-related encephalopathy, remain poorly understood, particularly in certain populations. This study aimed to investigate the prevalence and severity of these rare adverse effects in patients with cancer in Saudi Arabia. This cross-sectional observational study was conducted at King Saud University Medical City over a 2-year period and enrolled 272 patients who received 5-FU or capecitabine. Collected data included demographics, cancer type, treatment regimen, and reported adverse effects. Statistical analyses assessed the frequency, severity, and risk factors associated with uncommon toxicities. A total of 39.7% of patients experienced side effects, with neurological symptoms (39.6%) being the most common, followed by ocular (12.6%) and cardiac (11.8%) toxicities. Most adverse effects occurred during the initial chemotherapy cycles. Factors such as sex, body mass index, and cancer stage influenced toxicity risk, with capecitabine showing a stronger association with side effects than 5-FU. These findings emphasize the need for population-specific studies to improve early detection and management of rare toxicities related to 5-FU and capecitabine. Understanding the genetic and environmental contributors to adverse reactions could enhance treatment safety and efficacy in Saudi patients with cancer. Although dihydropyrimidine dehydrogenase deficiency is a recognized risk factor for severe 5-FU toxicity, routine dihydropyrimidine dehydrogenase genetic testing was not conducted in this cohort. This limitation underscores the need for further research in this area, particularly among Saudi patients.

Abstract Background 5-Fluorouracil (5-FU) and its prodrug Capecitabine are widely used chemotherapy drugs for treating various solid tumours, including colorectal, breast, and gastrointestinal cancers). Annually, around two million patients receive treatment with these drugs. However, a significant challenge with 5-FU treatment is toxicity. Between 10-30% of patients experience severe side effects, and in about 0.5-1% of cases, these toxicities can become life-threatening. The primary cause of this toxicity is a deficiency in the enzyme Dihydropyrimidine Dehydrogenase (DPD), critical for metabolizing 5-FU. Variants in the DPYD gene, which encodes DPD, reduce or lose the enzyme activity of DPD. Patients with DPD enzyme deficiency are at great risk of severe toxicity. In this study, we validated and implemented the DPYD genotyping assay for cancer patients in Saskatchewan, Canada, to guide fluoropyrimidine dosing. We further assessed the clinical outcome post-implementation in Saskatchewan. Methods Six clinically relevant variants of the DPYD gene associated with DPD deficiency recommended by the 2017 Clinical Pharmacogenetics Implementation Consortium (CPIC) guideline were included in the assay (transcript NM_000110.4), including *2A (rs3918290; c.1905+1G>A), *13 (rs55886062; c.1679T>G), c.2846A>T (rs67376798), and c.1129-5923C>G (rs75017182). The HapB3 haplotype was assessed by the c.1129-5923C>G (rs75017182) variant in combination with c.1236G>A (rs56038477) and c.483+18G>A (rs56276561). The Elucigene DPYD genotyping kit (Yourgene Health, UK) was used to detect these six semi-qualitatively. The validation process follows the technical standards for clinical pharmacogenomic testing and reporting established by the American College of Medical Genetics and Genomics. The assay*s sensitivity, specificity, accuracy, repeatability and reproducibility in detecting DPYD variants were included. Six months post-implementation of DPYD genotyping assays, patient outcomes were retrospectively evaluated. Patient demographics and clinical data were collected, including tumour types and staging, treatment regimen and dosage adjustment based on DPYD genotyping lab results, and toxicity incidence. This study adhered to institutional ethics guidelines. Results The DPYD pharmacogenomic assay demonstrated excellent performance with 100% sensitivity, specificity, accuracy, reproducibility, and repeatability. The detection limit was 1.25 ng/µL of DNA, ensuring high sensitivity. Over six months, 301 patient samples were tested, identifying 22 patients carrying at least one of the six DPYD variants. The most frequently observed allele was the HapB3 heterozygous genotype detected in 18 patients (5.9%). All detected variants exhibited reduced function or no function, with assigned DPD activity scores ranging from 1 to 1.5, indicating impaired fluoropyrimidines metabolism. Outcomes were evaluated for 21 enzyme-deficient patients, with 5-FU dose adjustments applied clinically. The majority of patients tolerate chemotherapy well without significant toxicity. Outcome evaluation for the 301 tested patients is ongoing. Conclusion DPYD testing allows for the early detection of DPD deficiencies, allowing personalized chemo drug dosing. These approaches improve patient outcomes and reduce the risk of severe side effects, highlighting the important roles in pharmacogenomics in personalized cancer treatment.

451 Background: Variants in the DPYD gene, which encodes the enzyme dihydropyrimidine dehydrogenase (DPD), are associated with impaired metabolism of fluoropyrimidines including fluorouracil (5-FU) and its oral prodrug, capecitabine. Patients with these variants are at increased risk for severe and potentially life-threatening toxicities. In December 2022, Dana-Farber Cancer Institute (DFCI) implemented a standardized, institution-wide program to support preemptive DPYD genotyping and genotype-guided dosing for patients initiating fluoropyrimidine-based therapy. The initiative included automated electronic health record prompts, pharmacist-led genotype-based dosing recommendations, as well as provider, pharmacist, nurse, and patient education. Methods: In September 2024, a new pharmacist-driven workflow was launched to enhance re-escalation rates in patients undergoing dose reduction based on DPYD genotyping and to operationalize genotype-guided dose initiation and adjustment in the outpatient setting. The workflow includes systematic identification of patients without prior exposure to 5-fluorouracil (5-FU) or capecitabine, automated prompts for DPYD testing, and a closed-loop notification system for abnormal results. Pharmacists provide dose modification and re-escalation recommendations based on standardized guidelines. The process also includes structured documentation and tracking of genotyping results and corresponding dose recommendations. Targeted training was delivered to clinical staff to ensure consistent adoption and adherence to the workflow. Results: Following the implementation of the pharmacist-driven DPYD workflow, DPYD gene deficiencies were identified in 28 patients receiving 5-fluorouracil and 17 patients receiving capecitabine out of the 810 patients that were tested from September 2024 to May 2025. Pharmacist-led genotype-guided dose reduction recommendations were provided for all identified patients, with 40/45 recommendations accepted by oncologist. Among these,14 patients were dose re-escalated based on clinical tolerability and in accordance with the standardized dosing recommendations. Conclusions: The implementation of a pharmacist-driven workflow for DPYD genotype interpretation and dose recommendations is both feasible and impactful in the outpatient oncology setting. This proactive approach supports personalized chemotherapy dosing, potentially reducing both the risk of over- and undertreatment.

Reply to: Dihydropyrimidine Dehydrogenase Enzyme-Guided Dosing of 5-Fluorouracil: Prioritizing Precision Over Dose Reduction.

Testing for four dihydropyrimidine dehydrogenase (DPYD) variants (DPYD*2 A, DPYD*13, c.2846 A > T, DPYD-HapB3) is currently implemented in clinical practice to prevent fluoropyrimidines (FLs) related toxicity but with limited sensitivity. This study aimed to identify novel genetic factors in FL-related genes to enhance risk prediction using data from the PREPARE trial (NCT03093818). Two hundred seventy-four patients receiving FL-based chemotherapy with severe toxicity were sequenced for 60 candidate genes. Gene and pathway-level association analyses focusing mainly on rare variants were performed using dedicated statistical tests, including gene-wise variant burden (GVB) analysis. DPYD germline variant burden beyond the four routinely tested markers emerged to contribute to toxicity, indicating that rarer genetic variants could help in refining the optimal FL dosage (p < 0.1). Functional rare variant burden in ABCB5, PARP1, ENOSF1, CYP3A4 and nuclear receptors pathway impacted on toxicity risk (p < 0.05 in at least one statistical test). GVB analysis confirmed ABCB5 as a significant risk gene and highlighted ABCC4, HNF4A, and XRCC3 as additional candidates. A predictive model combining genetic burden scores with clinical variables improved the identification of high-risk patients (sensitivity=0.71, specificity=0.74, accuracy=0.73). This study indicated a paradigm shift from population to individual-level arguing for an extension of testing beyond the four DPYD currently considered variants to predict FL-related toxicity.

5-Fluorouracil (5-FU) is widely used for colorectal cancer (CRC) treatment. Its administration is challenged by wide variability in patient toxicity. Genetic polymorphisms in dihydropyrimidine dehydrogenase (DYPD) and circulating microRNAs (miRNAs) are promising biomarkers to predict 5-FU-associated toxicity. The present study aimed to assess the association between miRNA expression profiles, three DPYD polymorphisms (85T>C, 1627A>G, 1896T>C) and hematological toxicity in patients with CRC receiving 5-FU. A total of 48 patients with CRC treated with 5-FU-based regimens were prospectively enrolled. Genotyping for DPYD 85T>C, 1627A>G and 1896T>C was performed by TaqMan Realtime PCR. Hematological toxicity was assessed by Common Terminology Criteria for Adverse Events v5.0 across two chemotherapy cycles. In a subset (n=9 for 85T>C; n=6 for 1896T>C), plasma levels of 43 candidate miRNAs related to 5-FU metabolism were quantified using a custom miRNA PCR array. The variant allele frequencies of DPYD were 0.14 for both 85T>C and 1896T>C, and 0.17 for 1627A>G. Although no associations were significant, carriers of 85T>C exhibited a higher incidence of grade ≥1 anemia in cycle two (69.2 vs. 40.0%, TC and CC; P=0.070). No significant trends were observed for other toxicities. miRNA profiling revealed that 20 miRNAs were differentially expressed in 85T>C carriers (9 up- and 11 downregulated) and 14 miRNAs in 1896T>C carriers (5 up- and 9 downregulated) vs. wild-type (P<0.05). The present findings suggest that the DPYD 85T>C polymorphism may predispose patients with CRC to cumulative hematological toxicity and is associated with distinct plasma miRNA signatures. Integration of DPYD genotyping with miRNA profiling warrants further investigation as a strategy to optimize 5-FU dosing and minimize toxicity in CRC.

To investigate the relationship between uracilemia (U)and dihydropyrimidine dehydrogenase (DPD) activity in peripheral blood mononuclear cells (PBMC) and whether they are influenced by renal or hepatic impairment. This retrospective study included 176 cancer patients with pre-treatment U (UPLC-MSMS assay) and PBMC-DPD (radioenzymatic assay) analyzed the same day (routine phenotyping). Blood renal (creatinine, BUN) and hepatic (ALT, AST, GGT, ALP, albumin, bilirubin) work-up was performed within 15days before or up to 4days after DPD phenotyping. Biochemical markers were categorized according to CTCAEv5.0 grade (G). Glomerular filtration rate (eGFR) was estimated (CKD-EPI and EKFC). Non-parametric statistical tests wereused. Prevalence of partial deficiency was 3.4 % based on PBMC-DPD (i.e.≤100 pmol/min/mg) and 6.3 % based on U (i.e.≥16 μg/L). No complete deficiency was observed. Fifteen patients out of 176 (8.5 %) exhibited discordant DPD status between PBMC activity and U. The correlation between PBMC-DPD and U was significant but weak (r=-0.309, p<0.001). PBMC-DPD (mean 246, median 235, range 62-926 pmol/min/mg prot) was not influenced by renal or hepatic impairment. U (mean 9.6, median 8.5, range 1.7-57.8 μg/L) was significantly higher in patients with elevated BUN (normal vs. >1-UNL, p=0.009), GGT (G0 vs. G1 vs. G2 vs. G3, p<0.001), AST (G0 vs. G≥1, p=0.015), or with hypoalbuminemia (G0 vs. G≥1, p=0.045). Categorized creatinine or eGFR did not influenceU. It remains unclear whether renal and/or hepatic impairment acts as a confounding factor affecting the accuracy of uracilemia testing, or whether truly impacts DPD activity, suggesting caution in U interpretation.

Clinical implementation and outcome evaluation of dihydropyrimidine dehydrogenase (DPYD) pharmacogenomic testing for fluoropyrimidine dosing in a Canadian Provincial Healthcare center.

Dihydropyrimidine dehydrogenase from Escherichia coli (EcDPD) reduces the 5,6-vinylic bond of pyrimidines using electrons from NADH. Here, we expand on our previous results that demonstrated that EcDPD undergoes reductive activation, that turnover is enhanced in the presence of NADH, and that EcDPD will reoxidize completely in the absence of excess NADH (Alt, T.B. et al. Arch. Biochem. Biophys., 2023, 748, 109772). A linear free energy relationship analysis using halogenated uracils revealed that reduction of the pyrimidine is not rate-limiting in turnover. In addition, mutating the catalytic cysteine to serine (C137S) slowed pyrimidine reduction but did not make it rate-limiting. [4S-2H] NADH kinetic isotope effects (KIE) were observed only for reductive activation. Together, these results demonstrate that electron transmission from the FAD to the FMN is rate-limiting in EcDPD turnover. An NAD+·FADH2 charge transfer absorption showed that the reductively activated enzyme is in the FADH2·4(Fe4S4)·FMN state. The electrostatic environment around the FAD of Sus scrofa DPD (SsDPD) was made more positive by point mutations in an attempt to retain electrons on the FAD; however, the reductively activated state remained unchanged, indicating that this process is controlled by something other than the electrostatics near the FAD cofactor. 5-ethynyluracil inactivation was used as a reporter for the position of the mobile loop containing Cys137, establishing that the loop exists in the "out" position in the oxidized enzyme, but is biased inward upon reductive activation.

Anticancer drug 5FU is extensively metabolized by dihydropyrimidine dehydrogenase (DPD), an enzyme with high interindividual variability. Poor metabolizer (PM, i.e., DPD deficient) patients are at risk of life-threatening toxicities. Whether ultra-rapid metabolizer (UM) status could conversely compromise 5FU efficacy remains to be investigated. In this real-world study, 352 adult patients treated with a 5FU-containing regimen were screened. Patients were classified as normal (extensive metabolizer, EM), PM, or UM on DPD function based upon baseline plasma uracil monitoring. The impact of DPD status on efficacy and safety endpoints was investigated. Patients were categorized on DPD as UM (11.9%), EM (75.9%), and PM (12.2%). The response rate was 54.5%, with median PFS and OS of 13.9 and 19 months, respectively. PM patients were treated with an average 13% lower 5FU starting dose. There was no statistical difference in efficacy between UM and other patients. Severe toxicities were observed in less than 5% of patients, an incidence significantly lower than commonly reported with 5FU-containing regimen and was comparable between UM, EM, and PM patients. Our observations suggest that UM status is not associated with the lack of efficacy of 5FU. In addition, upfront DPD testing with adaptive dosing helps to reduce the incidence of severe toxicities, as PM patients on reduced doses did not have more severe toxicities than other patients treated with standard doses, while exhibiting similar efficacy in terms of response rate and survival. When upfront DPD screening with adaptive dosing is performed, no difference is observed between UM, EM, and PM patients in terms of efficacy and safety. #PADSA3GKW7.

Chemotherapeutic treatment for colorectal cancer (colorectal cancer) allows for increased patient overall survival. However, current therapeutic regimens are often associated with the development of adverse drug reactions, which represent a morbidity, mortality and economic issue. We propose to identify novel germline markers that allow us to predict adverse drug reactions development after colorectal cancer chemotherapy. For that purpose, we selected 163 colorectal cancer patients with severe adverse drug reactions (CTCAE grades 3-4) and 52 controls and applied whole-exome sequencing (WES) to discover novel germline toxicity variants. We found 13 cases carrying actionable dihydropyrimidine dehydrogenase gene (DPYD) variants and a novel, potentially pathogenic DPYD variant - c.2071G > T, p.(V691L), rs202212118. Moreover, we found 30 novel rare, high-impact variants in 14 reported genes. We also identified seven patients carrying more than one variant in the same gene or pathway, with one patient hinting at a potential digenic inheritance. Using an exome-wide approach, we discovered and independently validated three novel candidate toxicity genes (ALDH9A1, FAM83A and EPX). Gene-based analyses also provided 14 genes significantly associated with neuropathy, skin toxicity and cardiotoxicity. Overall, the present work has utilised state-of-the-art approaches to uncover several novel candidate toxicity variants/genes.

Unpredictable, dose-limiting toxicity remains a challenge in cancer treatment. We evaluated dihydropyrimidine dehydrogenase (DPD) and UDP-glucuronosyltransferase 1A1 (UGT1A1) plasma levels in the context of chemotherapy-induced toxicity and disease progression. Seventy gastrointestinal cancer patients (30 FOLFOX; 40 FOLFIRI) were enrolled. DPD and UGT1A1 plasma levels were determined using ELISA. Univariable and bivariable analyses and a general linear model (GLM) framework were used. Post-infusional reductions in white blood cell and granulocyte counts were observed. For FOLFOX, the granulocyte counts decreased by 17% (r = 0.54; p = 0.0030), while FOLFIRI caused a 41% reduction (r = 0.43; p = 0.0063). DPD levels were lower in FOLFOX than in FOLFIRI (2.543 vs. 3.579; p = 0.0363; Cohen’s d = 0.52). The multiple linear regression models associated DPD levels with cancer progression (b* = 0.258, p = 0.034). The bivariate analysis and multiple linear regression indicated some trends of association between UGT1A1 levels and reduction in white blood cell (b* = 0.359, p = 0.042) and granulocyte counts (b* = 0.383, p = 0.030) among FOLFIRI-treated patients. These preliminary observations suggest that DPD and UGT1A1 might contribute to evaluating response assessment.

Managing elderly patients presents several challenges because of age-related declines; however, age should not be the sole determinant for adjuvant treatment decisions in patients with non-small cell lung cancer (NSCLC). Moreover, age may affect the expression of 5-fluorouracil (5-FU) biomarkers. The present study assessed: i) The effect of age on the expression levels of 5-FU biomarkers by analyzing a public database; and ii) the ability of these biomarkers to predict clinical outcomes in elderly patients with NSCLC who underwent complete resection in the Setouchi Lung Cancer Group Study 1201 (SCLG1201) followed by S-1 adjuvant chemotherapy. Changes in gene expression levels across age groups were assessed by analyzing The Cancer Genome Atlas (TCGA) database. The expression of 5-FU biomarkers, including thymidylate synthase (TS), dihydropyrimidine dehydrogenase (DPD), orotate phosphoribosyltransferase, epidermal growth factor receptor (EGFR) and excision repair cross-complementation group 1 (ERCC1), were assessed via quantitative reverse-transcription PCR assays in 89 elderly patients (≥75 years) with NSCLC who received adjuvant chemotherapy with oral fluoropyrimidine prodrug S-1 in the SLCG1201 trial. TCGA database analysis (n=955) showed that TS expression decreased significantly with aging, especially in the age group ≥75. In the SCLG1201 trial, univariate analysis revealed that EGFR upregulation and TS downregulation were correlated with favorable recurrence-free survival (RFS) and overall survival (OS), respectively. Multivariate analysis demonstrated that pathological stage was an independent prognostic factor for both RFS and OS. EGFR mutations were associated with upregulation of DPD and EGFR, and downregulation of TS and ERCC1. In conclusion, although pathological stage is an independent prognostic factor for survival, EGFR upregulation and TS downregulation may be a greater predictor of clinical outcomes in elderly patients with NSCLC treated with S-1 adjuvant chemotherapy. The age-related decrease in TS expression supports the potential benefit of 5-FU therapies in elderly patients. Nonetheless, further research is warranted to validate these results.

Introduction: Pharmacogenetics (PGx) plays a crucial role in precision medicine by identifying genetic variations that influence drug metabolism. For example, variants in dihydropyrimidine dehydrogenase (DPYD) have an impact on DPD enzyme activity and consequently on the metabolization of 5-fluorouracil, which can lead to severe adverse drug reactions. Therefore, pre-emptive DPYD genotyping was endorsed by the European Medicines Agency (EMA) in mid-2020 and subsequently included in national guidelines. In this study, we evaluated the impact of these guidelines on the request behavior for DPYD genotyping at a German university hospital in Mannheim (UMM) and on participation in external quality assessment (EQA) schemes in the European setting. Methods: A retrospective analysis was conducted on 386 DPYD genetic tests performed as part of standard care at the University Medical Center Mannheim from 2015 to 2021. Patient data, including demographics, diagnosis, and treatment, were obtained from electronic health records. Additionally, EQA data from the Reference Institute for Bioanalytics from 2015 to 2023 were analyzed to evaluate the adoption of DPYD testing across European laboratories. Results: The study observed a significant increase in DPYD genotyping requests at UMM following the EMA recommendation in 2020, with an up to 29-fold increase compared to previous years. Furthermore, a shift from post-treatment to pre-treatment genotyping was observed. DPYD variants were detected in 6.5% of cases, with DPYD HapB3 being the most frequent. EQA data from 23,114 genotypes demonstrated a growing participation in proficiency testing across Europe, indicating broader clinical adoption, and confirmed the impact on testing requirements in national guidelines on integration into clinical workflows. Conclusion: The integration of DPYD testing into national guidelines has significantly increased its clinical adoption, enhancing patient safety in oncology. However, standardization challenges remain. Further harmonization of guidelines and expansion of PGx testing may further optimize chemotherapy safety in the future.

To assess the impact and outcomes of a novel program for routine preemptive DPYD testing in fluoropyrimidine (FP)-naïve patients. This single-center, retrospective cohort study included adult patients who either received a systemic FP or had a DPYD test result between July 1, 2022, and June 30, 2023. Patients were categorized into preemptive or standard cohorts on the basis of the timing of their DPYD test relative to their initial FP dose. Primary outcomes measured were 90-day all-cause mortality, and FP-related hospitalizations and emergency department (ED) visits after the first FP dose. Secondary outcomes included the incidence of empiric dose reductions, FP avoidance, and dose escalation tolerability among patients with dihydropyrimidine dehydrogenase (DPD) deficiency. Among 1,281 patients, 90-day all-cause mortality was 5.78% in the preemptive cohort versus 8.23% in the standard cohort (adjusted hazard ratio [HR], 0.69 [95% CI, 0.43 to 1.10]; P = .12), with a notable overrepresentation of patients treated with curative intent in the preemptive group (53.0% v 39.4%, P < .0001). Deaths attributed to DPD deficiency were one (0.18%) in the preemptive cohort and four (0.72%) in the standard cohort (not statistically significant with limited power). Hospitalizations and ED visits related to FP toxicity were paradoxically higher in the preemptive cohort (13.99% v 8.69%, adjusted HR, 1.67 [95% CI, 1.15 to 2.43]; P = .007). Among patients with DPD deficiency in the preemptive cohort, 84.6% received an empiric FP dose reduction, and dose escalation was attempted in 52.2% of these cases. Preemptive DPYD testing did not significantly reduce treatment-related mortality, although a numerical decrease suggests potential benefits that may be substantiated with greater statistical power. Nearly half of the patients managed with a dose reduction did not undergo dose escalation.

BackgroundCapecitabine (CAP) is widely used in cancer treatment for its oral convenience and tumor targeting. However, its effectiveness in hepatocellular carcinoma (HCC) is suboptimal, possibly due to metabolic enzyme expression differences. This study aims to analyze these enzymes’ expression differences and explore their correlation with clinical pathological factors, to inform personalized CAP treatment.MethodsThis retrospective study used Immunohistochemistry (IHC) to analyze tumor and non-tumorous samples from HCC patients for CAP metabolic enzyme expression. PRM protein quantification was performed on 10% of samples to validate IHC results. Clinical and pathological data were collected, and multivariable linear regression was used to identify independent risk factors.ResultsThis study analyzed 60 HCC patients with hepatitis B and cirrhosis, revealing significant differences in CAP metabolic enzymes expression between tumor and non-tumorous tissues, with greater individual differences in tumors. Cytidine deaminase (CDA) levels in tumors decreased as liver function deteriorated (P = 0.023), while thymidine phosphorylase (TP) levels increased (P < 0.001). Tumor tissue had lower levels of carboxylesterase 1–2 (CES1-2), CDA, and dihydropyrimidine dehydrogenase (DPYD) but higher TP levels than non-tumorous and normal liver tissues. In tumor tissue, CDA (CV: 118.70%, SD: 3.897) and CES2 (CV: 94.90%, SD: 2.910) showed the greatest individual variability. Multivariable linear regression identified independent risk factors affecting CAP metabolic enzyme expression.ConclusionThis study has found significant variability in the expression of CAP metabolic enzymes across individuals and tissues. Developing a treatment flowchart based on metabolic enzymes provides a foundation for personalized HCC treatment and enhances the effectiveness of CAP therapy.Clinical Trial Number: Not applicable.

Xenobiotics, including pharmaceutical drugs, can be metabolized by both host and microbiota, in some cases by homologous enzymes. We conducted a systematic search for all known human proteins with gut microbial homologs. Because gene fusion and fission can obscure homology detection, we built a pipeline to identify not only full-length homologs, but also cases where microbial homologs were split across multiple adjacent genes in the same neighborhood or operon (“split homologs”). We found that human proteins with full-length gut microbial homologs disproportionately participate in xenobiotic metabolism. While this included many different enzyme classes, short-chain and aldo-keto reductases were the most frequently detected, especially in prevalent gut microbes, while cytochrome P450 homologs were largely restricted to lower-prevalence facultative anaerobes. In contrast, human proteins with split homologs tended to play roles in central metabolism, especially of nucleobase-containing compounds. We identify twelve specific drugs that gut microbial split homologs may metabolize; 2 of these, 6-mercaptopurine by xanthine dehydrogenase and 5-fluorouracil by dihydropyrimidine dehydrogenase, have been recently confirmed in mouse models. This work provides a comprehensive map of homology between the human and gut microbial proteomes, indicates which human xenobiotic enzyme classes are most likely to be shared by gut microorganisms, and finally demonstrates that split homology may be an underappreciated explanation for microbial contributions to drug metabolism.

1618 Background: DPD deficiency is the most important risk factor for developing fluoropyrimidine-related adverse events. Genetic variants causing DPD deficiency are found in 6-8% of Caucasian patients. However, there is limited information on their prevalence in underrepresented ethnic groups, such as Hispanics and Latinos, and testing for these variants is not routinely recommended in Latin America. Our goal was to assess the allele frequency of clinically actionable dihydropyrimidine dehydrogenase ( DPYD) risk variants defined by the Clinical Pharmacogenetics Implementation Consortium (CPIC) and the European Medicines Agency (EMA) among admixed Mexican patients with GI malignancies. Methods: Patients with recently diagnosed GI cancer candidates for fluropyrimidine therapy were recruited from a single institution in Mexico City. After providing informed consent, a blood sample and clinical characteristics were collected. We utilized the Illumina Infinium Global Screening Array (GSA)-to genotype 34 DPYD variants, six of which are known to lead to an increased risk of fluoropyrimidine toxicity and are considered clinically actionable. Results: Two hundred and eight patients with a mean age of 62 years (SD 13.2) were included. 47% were female. The most common type of cancer was colorectal (38%) followed by pancreas (22%) and biliary tract (18%). DNA samples from 192 patients passed quality control, of which 156 (62%) received fluoropyrimidines during follow-up. Only 2 patients (1%) were heterozygous for actionable DPYD intermediate metabolizer risk variant alleles: one with c.2846A &gt; T ( rs67376798 , D949V) and one with c.1129–5923C &gt; G [ rs75017182; HapB3 SNP c.1236G &gt; A; rs56038477]. No patients were found to have other CPIC-listed DPYD risk variants . Additionally, we investigated the allele frequencies of other 30 DPYD variants and observed low-frequency variation (between 0.260 and 0.0032) in rs56038477, rs1801160, rs17376848, rs1801159, rs1801158, rs45589337, rs2297595, rs200562975, and rs1801265. Several of these may be related to decreased DPYD activity and warrant further analysis regarding their impact on adverse drug reactions. Conclusions: In contrast with reports from Caucasic populations, we found a very low allele frequency of DPYD actionable variants. Our findings highlight the limitation of current pharmacogenomic testing recommendations and panels, which may not be appropriate for admixed ethnic populations such as Hispanics/Latinos due to disparities in representation. There is a need to study the role of other DPYD variants in larger patient samples to understand their role in the toxicity risk of admixed populations in Mexico and Latin America, to explore the use of novel techniques such as Next Generation Sequencing, and to investigate the effect of other related genes on toxicity risk.