Dihydropyrimidine Dehydrogenase Research Articles

Tamoxifen resistance alters sensitivity to 5-fluorouracil in a subset of estrogen receptor-positive breast cancer.

Sequential treatment with endocrine or chemotherapy is generally used in the treatment of estrogen receptor (ER)-positive recurrent breast cancer. To date, few studies have investigated the effect of long-term endocrine therapy on the response to subsequent chemotherapy in ER-positive breast cancer. We examined whether a preceding endocrine therapy affects the sensitivity to subsequent chemotherapy in ER-positive breast cancer cells. Three ER-positive breast cancer cell lines (T47D, MCF7, BT474) and tamoxifen-resistant sublines (T47D/T, MCF7/T, BT474/T) were analyzed for sensitivity to 5-fluorouracil, paclitaxel, and doxorubicin. The mRNA levels of factors related to drug sensitivity were analyzed by RT-PCR. MCF7/T cells became more sensitive to 5-fluorouracil than wild-type (wt)-MCF7 cells. In addition, the apoptosis induced by 5-fluorouracil was significantly increased in MCF7/T cells. However, no difference in sensitivity to chemotherapeutic agents was observed in T47D/T and BT474/T cells compared with their wt cells. Dihydropyrimidine dehydrogenase (DPYD) mRNA expression was significantly decreased in MCF7/T cells compared with wt-MCF7 cells. The expression of DPYD mRNA was restored with 5-azacytidine treatment in MCF7/T cells. In addition, DPYD 3'-UTR luciferase activity was significantly reduced in MCF7/T cells. These data indicated that the expression of DPYD mRNA was repressed by methylation of the DPYD promoter region and post-transcriptional regulation by miRNA in MCF7/T cells. In the mouse xenograft model, capecitabine significantly reduced the tumor volume in MCF7/T compared with MCF7. The results of this study indicate that endocrine therapy could alter the sensitivity to chemotherapeutic agents in a subset of breast cancers, and 5-fluorouracil may be effective in tamoxifen-resistant breast cancers.

Overexpression and characterization of Escherichia coli dihydropyrimidine dehydrogenase: a four iron-sulphur cluster containing flavoprotein.

Escherichia coli dihydropyrimidine dehydrogenase (EcDPD) catalyses the NADH-dependent reduction of uracil and thymine to the corresponding 5,6-dihydropyrimidines to control their metabolite pools. EcDPD consists of two subunits, PreT and PreA, and requires FAD, FMN and Fe-S clusters for activity. Recombinant EcDPD with a C-terminal His6-tagged-PreA subunit was overproduced in a DPD-lacking E. coli cells with augmented Fe-S cluster synthesis. Anaerobic purification resulted in purified enzyme with a specific activity of 13 μmol min-1 mg-1. The purified EcDPD was a heterotetramer and contained 0.81 FAD, 0.99 FMN, 14 acid-labile sulphur and 15 iron per PreT-PreA dimer. The enzyme exhibited Michaelis-Menten kinetics for both the forward and reverse reactions, which is distinct from mammalian DPDs showing substrate inhibition kinetics. For uracil reduction, the kcat, kcat/KNADH and kcat/Kuracil values were constant over the pH range of 5.5-10. For dihydrouracil (DHU) dehydrogenation, the pH-dependence of the kcat and kcat/KNAD+ values indicated that a residue with a pKa of 6.6 must be deprotonated for activity. Biochemical and kinetic comparisons with pig DPD revealed that protonation sates of the catalytically competent forms of EcDPD are distinct from those of pig enzyme.

Assessment of Oral Vancomycin-Induced Alterations in Gut Bacterial Microbiota and Metabolome of Healthy Men.

Several classes of antibiotics have reduced the mortality caused by infectious diseases; however, orally administered antibiotics alter the composition of gut microbiota, leading to dysbiosis-related disease. Therefore, in this study, we used 16S rRNA gene sequencing- and metabolomics-based approaches to investigate the effects of oral vancomycin on gut bacterial microbiota and the metabolome in biospecimens collected from healthy men. Samples collected from 11 healthy men were analyzed using 16S rRNA gene sequencing and metabolomics. 16S rRNA gene sequencing was performed to analyze the gut bacterial microbiota, and GC-TOFMS-based untargeted metabolomics was performed to analyze fecal, urine, and plasma metabolomics. Spearman’s rank correlation was utilized to explore the associations between gut bacterial microbiota and metabolome. Fecal 16S rRNA gene sequencing analysis showed decreased relative abundance of genera belonging to the phyla Bacteroidetes and Firmicutes, and increased relative abundance of genera of the phyla Proteobacteria and Fusobacteria. Fecal metabolomics analysis showed that levels of uracil, L-aspartic acid, lithocholic acid, and deoxycholic acid were significantly higher at baseline, whereas that of dihydrouracil was significantly higher after vancomycin administration. No significant metabolic markers were selected from urine and plasma metabolomics analysis. This study demonstrates that oral vancomycin administration induces alterations in gut bacterial microbiota and metabolome. Correlation analysis between our two datasets shows that alteration of the gut bacterial microbiota, induced by oral vancomycin, potentially affected the systemic activity of dihydropyrimidine dehydrogenase. This correlation should be further examined in future studies to define the effects of gut bacterial microbiota on drug-metabolizing enzymes, thereby contributing to the development of personalized therapy.

Eastern Canadian Gastrointestinal Cancer Consensus Conference 2019.

The annual Eastern Canadian Gastrointestinal Cancer Consensus Conference 2019 was held in Morell, Prince Edward Island, 19–21 September 2019. Experts in medical oncology, radiation oncology, and surgical oncology who are involved in the management of patients with gastrointestinal malignancies participated in presentations and discussion sessions for the purpose of developing the recommendations presented here. This consensus statement addresses multiple topics in the management of anal, colorectal, biliary tract, and gastric cancers, including: radiotherapy and systemic therapy for localized and advanced anal cancer; watch and wait strategy for the management of rectal cancer; role of testing for dihydropyrimidine dehydrogenase (DPD) deficiency prior to commencement of fluoropyrimidine therapy; radiotherapy and systemic therapy in the adjuvant and unresectable settings for biliary tract cancer; and radiotherapy and systemic therapy in the perioperative setting for early-stage gastric cancer.

Perturbing the Movement of Hydrogens to Delineate and Assign Events in the Reductive Activation and Turnover of Porcine Dihydropyrimidine Dehydrogenase.

The native function of dihydropyrimidine dehydrogenase (DPD) is to reduce the 5,6-vinylic bond of pyrimidines uracil and thymine with electrons obtained from NADPH. NADPH and pyrimidines bind at separate active sites separated by ∼60 Å that are bridged by four Fe4S4 centers. We have shown that DPD undergoes reductive activation, taking up two electrons from NADPH [Beaupre, B. A., et al. (2020) Biochemistry 59, 2419-2431]. pH studies indicate that the rate of turnover is not controlled by the protonation state of the general acid, cysteine 671. The activation of the C671 variants is delineated into two phases particularly at low pH values. Spectral deconvolution of the delineated reductive activation reaction reveals that the initial phase results in the accumulation of charge transfer absorption added to the binding difference spectrum for NADPH. The second phase results in reduction of one of the two flavins. X-ray crystal structure analysis of the C671S variant soaked with NADPH and the slow substrate, thymine, in a low-oxygen atmosphere resolved the presumed activated form of the enzyme that has the FMN cofactor reduced. These data reveal that charge transfer arises from the proximity of the NADPH and FAD bases and that the ensuing flavin is a result of rapid transfer of electrons to the FMN without accumulation of reduced forms of the FAD or Fe4S4 centers. These data suggest that the slow rate of turnover of DPD is governed by the movement of a mobile structural feature that carries the C671 residue.

Feasibility of implementing a pharmacist-led DPYD gene testing service for patients commencing 5-fluorouracil (5FU) or capecitabine.

e18644 Background: Polymorphisms in the DPYD gene, which encodes for dihydropyrimidine dehydrogenase (DPD), may impair DPD metabolism of fluoropyrimidines (FP) and cause life-threatening toxicities. The European Medicines Agency (EMA) recommend testing for DPD activity before FP therapy, but the Australian Therapeutic Goods Administration and the US Food and Drug Administration do not currently recommend this. At our hospital, pre-emptive DPYD gene screening was established in response to 7 cases of severe FP-toxicity and significant challenges for timely access to the life-saving antidote, uridine triacetate (UT), in the preceding 3 years. This study assessed the feasibility of a pharmacist-led DPYD gene testing service in an Australian cancer centre. Methods: Patients planned for FP therapy, without previous FP exposure, were referred to the Clinical Pharmacogenetics (CPGx) pharmacist for consenting, before a blood or buccal swab sample was taken. An external genomics company screened for the five Clinical Pharmacogenetics Implementation Consortium (CPIC) recommended gene variants (c.1905+1G > A, c.1679T > G, c.2846A > T, c.1236G > A and c.557A > G). Dose recommendations based on CPIC guidelines and phenotype were made to the treating clinician. Patients were followed-up for toxicity (graded according to CTCAE v5.0) at 3-5 days post first FP exposure and pre-cycle 2. Results: Between 16 December 2019 and 11 December 2020, 311 patients were planned for FP therapy. Genetic testing did not occur for 13 patients, in the first two months of program implementation mostly due to unfamiliarity with procedures. Of the 298 genotyped patients (median age 59.5 years, 52.7% female, 67.8% Upper and Lower Gastrointestinal, 18.1% Breast), 274 (91.9%) were seen by the CPGx pharmacist within 1 day of referral. Median time from samples being taken to result availability was 6 days. 286 patient (96.0%) results were reported and acted upon prior to the planned cycle 1 FP commencement date. Overall, 1 patient (0.3%, 95%CI 0.1-1.9) was identified as a poor metaboliser and avoided FP therapy. Ten patients (3.4%, 95%CI 1.8-6.0) were identified as intermediate metabolisers, of which 2 patients did not receive chemotherapy due to changes in goals of care, 1 patient received only one cycle at 100% of the full dose but passed away due to disease progression, 1 patient required UT administration after cycle 2 despite 50% dose reductions for both cycles and 6 patients received an initial 50% dose reduction, where for subsequent cycles, 3 continued at this dose level, 2 had dose increases and 1 had a further dose reduction. 17 patients experienced at least one grade 3/4 toxicity pre-cycle 2; all had normal metaboliser phenotypes. Conclusions: A pharmacist-led DPYD gene testing service is feasible, with acceptable test result turnaround times and phenotype identification rates similar to that reported by the EMA.

The association of renal function with safety and efficacy of cisplatin plus S-1 (CS) therapy and docetaxel plus cisplatin plus S-1 (DCS) therapy in patients with advanced gastric cancer (AGC): An additional analysis of JCOG1013.

e16035 Background: A phase III study, JCOG1013, did not show the superiority of docetaxel plus cisplatin plus S-1 (DCS) to cisplatin plus S-1 (CS) in overall survival (OS) (Yamada Y, Lancet GH 2019). It is known that cisplatin and gimeracil (an inhibitor of dihydropyrimidine dehydrogenase contained in S-1) are excreted in urine. We previously reported (abstr 197, ASCO-GI 2021) exploratory analysis of JCOG1013 which showed creatinine clearance (CrCl) was associated with safety (Grade [G]4 hematological toxicity for CS, and G3-4 non-hematological toxicity for CS and DCS), but not with efficacy in either group. Here, we report the additional detail results of this exploratory analysis. Methods: Among 741 participants in JCOG1013, patients with serum creatinine level < 1.2 mg/dL were included in this analysis and categorized by CrCl and treatment into A1 (CrCl ≥ 80 mL/min, CS), A2 (60 < CrCl < 80, CS), A3 (CrCl < 60, CS), B1 (CrCl > 80, DCS), B2 (60 < CrCl < 80, DCS), and B3 (CrCl < 60, DCS). The dose (mg/m2) of C/S was 60/80 regardless renal function in group A (A1, A2 and A3), and that of D/C/S was adjusted in group B as follows: 40/60/80 in B1, 40/50/80 in B2, and 40/40/65 in B3. Adverse events, OS, progression-free survival (PFS), and objective response rate (ORR) were compared by CrCl in group A (A1 vs. A2 vs. A3) and group B (B1 vs B2 vs B3), respectively. Results: Of 723 pts (169/136/57 in A1/A2/A3 and 170/138/53 in B1/B2/B3), the median CrCl (mL/min) was 94.1/71.9/53.4 in A1/A2/A3 and 98.2/70.0/55.6 in B1/B2/B3. The relative dose intensity of C/S was 90.4/75.3%, 87.8/74.9% and 85.7/72.8% in A1, A2 and A3, and that of D/C/S was 87.5/77.7/74.9%, 85.8/61.2/72.7% and 87.8/49.4/58.3% in B1, B2 and B3. The incidence of G4 white blood cell decreased, G4 neutrophil count decreased, and G3-4 anorexia were 1.2/4.4/9.3% (P < 0.01), 4.8/11.1/18.5% (P < 0.01), 14.4/28.1/28.6% (P < 0.01) in A1/A2/A3, and 1.8/3.0/4.0% (P = 0.36), 27.3/24.8/20.0% (P = 0.28), 22.4/29.3/32.0% (P = 0.11) in B1/B2/B3, respectively. No significant association between CrCl and other adverse events was observed either in CS or in DCS group. The median OS was 15.4/15.5/15.4 months in A1/A2/A3 (P = 0.89) and 15.3/13.7/13.7 months in B1/B2/B3 (P = 0.72). The median PFS was comparable among A1/A2/A3 (7.1/6.8/6.2 months, P = 0.88) and B1/B2/B3 groups (7.5/7.2/7.8 months, P = 0.85). ORR showed no significant difference in A1/A2/A3 (58.9/57.8/46.9%, P = 0.31) and B1/B2/B3 groups (62.0/61.5/51.5%, P = 0.36). Conclusions: Dose modification according to renal function in the DCS arm could control the increase of severe toxicities, which were observed frequently in patients with low renal function in patients receiving fixed dose of CS. Clinical trial information: 000007652.

Randomized double-blind, placebo-controlled study of topical diclofenac in prevention of hand-foot syndrome in patients receiving capecitabine.

TPS12135 Background: The pathophysiology of capecitabine induced hand-foot syndrome (HFS) includes activation of cyclooxygenase (COX)-2, leading to an upregulation of the inflammatory cascade. Prophylaxis with oral celecoxib was previously reported to be associated with a significantly lower frequency of HFS (grade 1 [29.0% vs. 72.0%, p < 0.001] and grade 2 [11.8% vs. 30.0%, p=0.024]) (1). The findings were confirmed in a phase III trial (2). However, the associated systemic adverse events limit routine prophylactic use. Till date, no clinical trials have assessed the role of topical non-steroidal anti-inflammatory drugs (NSAIDs) in preventing HFS. Methods: In this investigator-initiated randomised phase III double-blind, placebo controlled, parallel group trial, a total of 264 patients with any stage breast or gastrointestinal cancer planned to receive capecitabine as a single agent or in combination with other chemotherapy will be randomised (1:1) to 1% topical diclofenac or placebo (base for 1% topical diclofenac) arm at a single tertiary care cancer centre in India. Randomization will be done by stratified (male vs female, and capecitabine mono therapy vs combination) permuted block method using a computer generated random sequence and allocation concealment will be done by using sealed opaque envelopes. In both the arms, patients will be asked to apply 1 fingertip unit (FTU) of topical medication on both surfaces of bilateral hands twice daily for a total duration of 12 weeks or till development of grade 2 or higher HFS, whichever is earlier. The primary objective is to compare the effect of topical diclofenac with placebo in preventing clinically significant HFS (incidence of the National Cancer Institute (NCI) Common Terminology Criteria for Adverse Events (CTCAE) version 5.0 grade 2 or higher HFS). The secondary objectives include comparison of topical diclofenac with placebo on (i) incidence of NCI CTCv5.0 all grade HFS, (ii) time to develop grade ≥2 HFS from start of capecitabine, (iii) patient-reported outcomes using HFS-14 questionnaire (iv) adherence with topical application using self-reported adherence diary, (v) capecitabine dose reductions, delays and cessation due to HFS and (vi) safety profile (NCICTCv5.0). The tertiary correlative endpoint is to correlate the occurrence and severity of HFS with serum COX-2 levels and polymorphism of dihydropyrimidine dehydrogenase (DPPD) enzyme. The trial is registered at the Clinical Trial Registry of India (CTRI/2021/01/030592). Till date, we have enrolled 12/264 patients. (1) Zhang RX et al. J Cancer Res Clin Oncol. 2011;137(6):953-957. (2) Zhang RX et al. Annals of oncology. 2012;23(5):1348-1353. Clinical trial information: CTRI/2021/01/030592.

Dihydropyrimidine dehydrogenase deficiency in patients treated with 5FU or capecitabine based regimens: A single center experience from South India.

e15517 Background: DPYD deficiency is present in 3-5% of patients. The risk of treatment-related death in DPYD mutation carriers who receive fluoropyrimidine chemotherapy has been estimated at 3-10%. There is growing data in support of widespread screening for DPYD deficiency prior to fluoropyrimidine chemotherapy. The purpose of our study was to identify the prevalence of DPYD deficiency among patients receiving 5-fluorouracil (5FU) or capecitabine based combination chemotherapy, and to analyse the toxicity profile among the DPYD deficient group. Methods: The study involved patients who have received 5FU and capecitabine based chemotherapy for the treatment for gastrointestinal, breast and head and neck cancers between 2019-2020. Four DPYD variants were checked using real-time PCR based Genotyping assay. Three common DPYD variants recommended by the CPIC guidelines (IVS14+1 G>A (*2A), c.1679T>G (*13), c.2846A>T) and a common variant in Asian population (c.496A>G), based on previous studies, was included in our analysis. These variants were assessed prior to the initiation of the chemotherapy and dose was modified based on the activity score and the toxicity profile was assessed. Descriptive statistics was performed using SPSS version 20. Results: 375 patients were included in this analysis. The median age of the cohort was 61years (21-84 years). 51.3% were males and 49.7% females. Among the 375 patients, 47 patients had DPYD mutation (12.5%). The median age of the DPYD mutated patients were 68 years; 29 (61.7%) males and 18 (38.2%) females. 32 (68.8%) had deleterious mutation in DPYD variant c.496A>G (rs2297595) and 15 (31.9%) showed mutation IVS14+1 G>A (rs3918290). 35 out 47 patients had grade II-III toxicity even after dose reduction during the first cycle of chemotherapy. The commonly seen adverse events were hand and foot syndrome in 18 (38.3%), mucositis in 7 (14.9%), diarrrhoea in 15 (31.9%) and neutropenia in 25 (31.9%) patients. Four patients had febrile neutropenia. One patient experience myocardial infarction. There was no mortality. Chi square analysis showed DPYD mutation had significant association with presence of severe adverse reaction (74.5%, p-value. 0.002). Conclusions: Prevalence of DPYD mutation in our patients was 12.5%. They experienced more toxicities while receiving 5-FU/Capecitabine even after dose modification. c.496A>G (rs2297595) was the most common variant seen in our patients. Screening of patients for DPYD mutations prior to administration of 5-FU/capecitabine using pharmacogenetic methods may help identify those patients who are at risk for adverse effects, allowing a more individualized approach to their chemotherapy management. c.496A>G (rs2297595) variant should also be in included routinely in DPYD screening among South Asian population.

Force Field Parameters for Fe2+4S2-4 Clusters of Dihydropyrimidine Dehydrogenase, the 5-Fluorouracil Cancer Drug Deactivation Protein: A Step towards In Silico Pharmacogenomics Studies.

The dimeric dihydropyrimidine dehydrogenase (DPD), metalloenzyme, an adjunct anti-cancer drug target, contains highly specialized 4 × Fe2+4S2−4 clusters per chain. These clusters facilitate the catalysis of the rate-limiting step in the pyrimidine degradation pathway through a harmonized electron transfer cascade that triggers a redox catabolic reaction. In the process, the bulk of the administered 5-fluorouracil (5-FU) cancer drug is inactivated, while a small proportion is activated to nucleic acid antimetabolites. The occurrence of missense mutations in DPD protein within the general population, including those of African descent, has adverse toxicity effects due to altered 5-FU metabolism. Thus, deciphering mutation effects on protein structure and function is vital, especially for precision medicine purposes. We previously proposed combining molecular dynamics (MD) and dynamic residue network (DRN) analysis to decipher the molecular mechanisms of missense mutations in other proteins. However, the presence of Fe2+4S2−4 clusters in DPD poses a challenge for such in silico studies. The existing AMBER force field parameters cannot accurately describe the Fe2+ center coordination exhibited by this enzyme. Therefore, this study aimed to derive AMBER force field parameters for DPD enzyme Fe2+ centers, using the original Seminario method and the collation features Visual Force Field Derivation Toolkit as a supportive approach. All-atom MD simulations were performed to validate the results. Both approaches generated similar force field parameters, which accurately described the human DPD protein Fe2+4S2−4 cluster architecture. This information is crucial and opens new avenues for in silico cancer pharmacogenomics and drug discovery related research on 5-FU drug efficacy and toxicity issues.

Leukoencephalopathy with transient splenial lesions related to 5-fluorouracil or capecitabine.

5-Fluorouracil (5-FU) and its oral prodrug capecitabine have been rarely but consistently associated with acute central nervous system toxicity, including transient leukoencephalopathies involving the splenium of the corpus callosum. We performed a retrospective search in the French Pharmacovigilance database (FPDB) (January 1985-July 2020) for adult patients affected by solid cancers who developed acute toxic leukoencephalopathies with splenial lesions following treatment with 5-FU or capecitabine. A comprehensive review of the literature helped to circumstantiate our findings. Our research in the FPDB identified six patients who, within 3days from their first cycle of 5-FU or capecitabine, developed acute neurological symptoms, including gait ataxia (n=4), dysarthria (n=3), dysmetria (n=2), headache (n=2), and confusion (n=2). Brain magnetic resonance imaging (MRI) showed T2/FLAIR (fluid-attenuated inversion recovery) hyperintensities in the corpus callosum, with diffusion restriction and no contrast enhancement, generally accompanied by additional alterations in the bilateral supratentorial white matter (n=5). All patients discontinued the agent supposedly responsible for the toxicity and experienced full recovery after a median of 8.5days from symptom onset. Control MRI showed a progressive normalization of acute MRI abnormalities. Literature review identified 26 cases with similar clinical and paraclinical characteristics. A single patient from the literature resumed 5-FU at a lower dose, with no recurrent toxicity. 5-FU and capecitabine might be responsible for acute leukoencephalopathies with transient splenial lesions that are generally reversible upon drug discontinuation. Resuming the agent responsible for toxicity might be feasible in selected cases, after having excluded dihydropyrimidine dehydrogenase deficiency, if expected benefits outweigh the risks.

Haplotype structure defines effects of common DPYD variants c.85T > C (rs1801265) and c.496A > G (rs2297595) on dihydropyrimidine dehydrogenase activity: Implication for 5-fluorouracil toxicity.

AimsThe aim of this study was to identify risk variants and haplotypes that impair dihydropyrimidine dehydrogenase (DPD) activity and are, therefore, candidate risk variants for severe toxicity to 5‐fluorouracil (5‐FU) chemotherapy.MethodsPlasma dihydrouracil/uracil (UH2/U) ratios were measured as a population marker for DPD activity in a total of 1382 subjects from 4 independent studies. Genotype and haplotype correlations with UH2/U ratios were assessed.ResultsSignificantly lower UH2/U ratios (panova < 2 × 10−16) were observed in carriers of the 4 well‐studied 5‐FU toxicity risk variants with mean differences (MD) of −43.7% for DPYD c.1905 + 1G > A (rs3918290), −46.0% for DPYD c.1679T > G (rs55886062), −37.1%, for DPYD c.2846A > T (rs67376798), and −13.2% for DPYD c.1129‐5923C > G (rs75017182). An additional variant, DPYD c.496A > G (rs2297595), was also associated with lower UH2/U ratios (P < .0001, MD: −12.6%). A haplotype analysis was performed for variants in linkage disequilibrium with c.496A > G, which consisted of the common variant c.85T > C (rs1801265) and the risk variant c.1129‐5923C > G. Both haplotypes carrying c.496A > G were associated with decreased UH2/U ratios (H3, P = .003, MD: −9.6%; H5, P = .002, MD: −16.9%). A haplotype carrying only the variant c.85T > C (H2) was associated with elevated ratios (P = .004, MD: +8.6%).ConclusionsBased on our data, DPYD‐c.496A > G is a strong candidate risk allele for 5‐FU toxicity. Our data suggest that DPYD‐c.85T > C might be protective; however, the deleterious impacts of the linked alleles c.496A > G and c.1129‐5923C > G likely limit this effect in patients. The possible protective effect of c.85T > C and linkage disequilibrium with c.496A > G and c.1129‐5923C > G may have hampered prior association studies and should be considered in future clinical studies.

An Evaluation of the Diagnostic Accuracy of a Panel of Variants in DPYD and a Single Variant in ENOSF1 for Predicting Common Capecitabine Related Toxicities.

Simple Summary5-Fluorouracil (5-FU) is a chemotherapy drug that can cause severe toxicity in some patients. A protein, an action molecule in our cells, called dihydropyrimidine dehydrogenase, or DPD for short, is important in clearing 5-FU from the body. Some people have versions of DPD that do not clear 5-FU very well. This causes active drug to stay in the body too long, causing toxicities such as diarrhoea or low levels of blood cells important for fighting infections. Current guidelines identify four sequence changes in the gene that encodes DPD with high level evidence of an impact on protein activity. Our study aims to calculate the frequency of a set of variants identified in patients with DPD deficiency in patients that were part of a clinical trial called QUASAR 2. We go on to test how well the DPD deficiency variants and a set of common variants previously shown to be associated with 5-FU toxicity can predict a person’s risk of 5-Fluorouracil induced toxicity. Our research is important for working out the best way to identify patients at risk of toxicity so high risk patients can be given lower doses of 5-Fluorouracil or be treated with a different drug all together.Efficacy of 5-Fluorouracil (5-FU)-based chemotherapy is limited by significant toxicity. Tests based upon variants in the Clinical Pharmacogenetics Implementation Consortium (CPIC) guidelines with high level evidence of a link to dihydropyrimidine dehydrogenase (DPD) phenotype and 5-FU toxicity are available to identify patients at high risk of severe adverse events (AEs). We previously reported associations between rs1213215, rs2612091, and NM_000110.3:c.1906-14763G>A (rs12022243) and capecitabine induced toxicity in clinical trial QUASAR 2. We also identified patients with DPD deficiency alleles NM_000110.3: c.1905+1G>A, NM_000110.3: c.2846C>T, NM_000110.3:c.1679T>G and NM_000110.3:c.1651G>A. We have now assessed the frequency of thirteen additional DPYD deficiency variants in 888 patients from the QUASAR 2 clinical trial. We also compared the area under the curve (AUC)—a measure of diagnostic accuracy—of the high-level evidence variants from the CPIC guidelines plus and minus additional DPYD deficiency variants and or common variants associated with 5-FU toxicity. Including additional DPYD deficiency variants retained good diagnostic accuracy for serious adverse events (AEs) and improved sensitivity for predicting grade 4 haematological toxicities (sensitivity 0.75, specificity 0.94) but the improvement in AUC for this toxicity was not significant. Larger datasets will be required to determine the benefit of including additional DPYD deficiency variants not observed here. Genotyping two common alleles statistically significantly improves AUC for prediction of risk of HFS and may be clinically useful (AUC difference 0.177, sensitivity 0.84, specificity 0.31).

Conjugation of Sinapic Acid Analogues with 5-Fluorouracil: Synthesis, Preliminary Cytotoxicity, and Release Study

Tripartite prodrug approach is a promising strategy to improve the therapeutic efficacy of orally administrated drugs having a low bioavailability. 5-Fluorouracil is a primary chemotherapeutic agent used in the treatment of many solid tumors. The oral use of 5-fluorouracil suffers from many challenges, which are principally contributed to the erratic activity of dihydropyrimidine dehydrogenase in the GIT. In this work, five integrates were prepared as tripartite mutual prodrugs by connecting sinapic acid and four of its analogues to 5-fluorouracil through amenable ester bond. Chemical structures of the prepared integrates were defined by studying their FTIR, 1H-NMR, and 13C-NMR spectra. Initiatory cytotoxicity study was verified for these integrates via MTT test versus four cancer cell lines including HeLa, MCF-7, AMN3, and SKG. The in vitro study of releasing the active drug from the synthesized integrates was followed spectrometerically using a human serum. The results of the cytotoxicity study after 24 hr of treatment revealed that the synthesized integrates by themselves have a non-toxic activity toward the test cell lines. In contrast, the results of the same study but after 72 hr of treatment indicated the potential antitumor activity of the tested prodrugs which indicates the effective release of the active components from these prodrugs. Also, the data gathered from the release study utilizing a human serum indicated that these integrates can release the active agents pursued pseudo first order kinetics. It is concluded that the synthesized integrates could be considered as mutual prodrugs and that may be improved the clinical applications of 5-Fluorouracil.

The Interaction of Porcine Dihydropyrimidine Dehydrogenase with the Chemotherapy Sensitizer: 5-Ethynyluracil.

Dihydropyrimidine dehydrogenase (DPD) is a complex enzyme that reduces the 5,6-vinylic bond of pyrimidines, uracil, and thymine. 5-Fluorouracil (5FU) is also a substrate for DPD and a common chemotherapeutic agent used to treat numerous cancers. The reduction of 5FU to 5-fluoro-5,6-dihydrouracil negates its toxicity and efficacy. Patients with high DPD activity levels typically have poor outcomes when treated with 5FU. DPD is thus a central mitigating factor in the treatment of a variety of cancers. 5-Ethynyluracil (5EU) covalently inactivates DPD by cross-linking with the active-site general acid cysteine in the pyrimidine binding site. This reaction is dependent on the simultaneous binding of 5EU and nicotinamide adenine dinucleotide phosphate (NADPH). This ternary complex induces DPD to become activated by taking up two electrons from the NADPH. The covalent inactivation of DPD by 5EU occurs concomitantly with this reductive activation with a rate constant of ∼0.2 s-1. This kinact value is correlated with the rate of reduction of one of the two flavin cofactors and the localization of a mobile loop in the pyrimidine active site that places the cysteine that serves as the general acid in catalysis proximal to the 5EU ethynyl group. Efficient cross-linking is reliant on enzyme activation, but this process appears to also have a conformational aspect in that nonreductive NADPH analogues can also induce a partial inactivation. Cross-linking then renders DPD inactive by severing the proton-coupled electron transfer mechanism that transmits electrons 56 Å across the protein.

Unusual case of colorectal carcinoma with sarcoid-like mediastinal adenopathy and near-fatal DPD deficiency

The liver is the commonest site for metastases in colorectal carcinoma; other isolated sites are considered extremely rare. 5-fluorouracil (5-FU) is the backbone of treatment for metastatic colorectal carcinoma (mCRC) and without it survival may be significantly reduced. It is primarily metabolised by dihydropyrimidine dehydrogenase (DPD). Testing for DPD deficiency is not a routine practice and toxicity will only manifest following drug challenge. There are limited standardised treatment guidelines in managing patients with severe drug reactions following 5-FU exposure. We describe a delayed presentation of life-threatening DPD deficiency in a patient with colorectal carcinoma and mediastinal lymphadenopathy. We describe our experience with chemotherapy in this difficult clinical scenario and highlight the importance of histological confirmation in unusual sites of metastatic disease.

Potential Impact of DPYD Variation on Fluoropyrimidine Drug Response in sub-Saharan African Populations.

Cancer is a critical health burden in Africa, and mortality rates are rising rapidly. Treatments are expensive and often cause adverse drug reactions (ADRs). Fluoropyrimidine treatments can lead to severe toxicity events which have been linked to variants within the dihydropyrimidine dehydrogenase (DPYD) gene. There are clinical guidelines to improve safety outcomes of treatment, but these are primarily based on variants assessed in non-African populations. Whole genome sequencing data from the 1000 Genomes Project and the African Genome Variation Project were mined to assess variation in DPYD in eight sub-Saharan African populations. Variant functional annotation was performed with a series of bioinformatics tools to assess potential likelihood of deleterious impact. There were 29 DPYD coding variants identified in the datasets assessed, of which 25 are rare, and some of which are known to be deleterious. One African-specific variant (rs115232898-C), is common in sub-Saharan Africans (1–4%) and known to reduce the function of the dihydropyrimidine dehydrogenase enzyme (DPD), having been linked to cases of severe toxicity. This variant, once validated in clinical trials, should be considered for inclusion in clinical guidelines for use in sub-Saharan African populations. The rs2297595-C variant is less well-characterized in terms of effect, but shows significant allele frequency differences between sub-Saharan African populations (0.5–11.5%; p = 1.5 × 10−4), and is more common in East African populations. This study highlights the relevance of African-data informed guidelines for fluorouracil drug safety in sub-Saharan Africans, and the need for region-specific data to ensure that Africans may benefit optimally from a precision medicine approach.

Cancer-Specific Targeting of Taurine-Upregulated Gene 1 Enhances the Effects of Chemotherapy in Pancreatic Cancer.

Overcoming drug resistance is one of the biggest challenges in cancer chemotherapy. In this study, we examine whether targeting the long noncoding RNA taurine upregulated gene 1 (TUG1) could be an effective therapeutic approach to overcome drug resistance in pancreatic ductal adenocarcinoma (PDAC). TUG1 was expressed at significantly higher levels across 197 PDAC tissues compared with normal pancreatic tissues. Overall survival of patients with PDAC who had undergone 5-FU-based chemotherapy was shorter in high TUG1 group than in low TUG1 group. Mechanistically, TUG1 antagonized miR-376b-3p and upregulated dihydropyrimidine dehydrogenase (DPD). TUG1 depletion induced susceptibility to 5-FU in BxPC-3 and PK-9 pancreatic cell lines. Consistently, the cellular concentration of 5-FU was significantly higher under TUG1-depleted conditions. In PDAC xenograft models, intravenous treatment with a cancer-specific drug delivery system (TUG1-DDS) and 5-FU significantly suppressed PDAC tumor growth compared with 5-FU treatment alone. This novel approach using TUG1-DDS in combination with 5-FU may serve as an effective therapeutic option to attenuate DPD activity and meet appropriate 5-FU dosage requirements in targeted PDAC cells, which can reduce the systemic adverse effects of chemotherapy. SIGNIFICANCE: Targeting TUG1 coupled with a cancer-specific drug delivery system effectively modulates 5-FU catabolism in TUG1-overexpressing PDAC cells, thus contributing to a new combinatorial strategy for cancer treatment. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/81/7/1654/F1.large.jpg.

DPYD, down-regulated by the potentially chemopreventive agent luteolin, interacts with STAT3 in pancreatic cancer

The 5-year survival rate of pancreatic ductal carcinoma (PDAC) patients is <10% despite progress in clinical medicine. Strategies to prevent the development of PDAC are urgently required. The flavonoids Luteolin (Lut) and hesperetin (Hes) may be cancer-chemopreventive, but effects on pancreatic carcinogenesis in vivo have not been studied. Here, the chemopreventive effects of Lut and Hes on pancreatic carcinogenesis are assessed in the BOP-induced hamster PDAC model. Lut but not Hes suppressed proliferation of pancreatic intraepithelial neoplasia (PanIN) and reduced the incidence and multiplicity of PDAC in this model. Lut also inhibited the proliferation of hamster and human pancreatic cancer cells in vitro. Multi-blot and microarray assays revealed decreased phosphorylated STAT3 (pSTAT3) and dihydropyrimidine dehydrogenase (DPYD) on Lut exposure. To explore the relationship between DPYD and STAT3 activity, the former was silenced by RNAi or overexpressed using expression vectors, and the latter was inactivated by small molecule inhibitors or stimulated by IL6 in human PDAC cells. DPYD knock-down decreased, and overexpression increased, pSTAT3 and cell proliferation. DPYD expression was decreased by inactivation of STAT3 and increased by its activation. The frequency of pSTAT3-positive cells and DPYD expression was significantly correlated and was decreased in parallel by Lut in the hamster PDAC model. Finally, immunohistochemical analysis in 73 cases of human PDAC demonstrated that DPYD expression was positively correlated with the Ki-67 labeling index, and high expression was associated with poor prognosis. These results indicate that Lut is a promising chemopreventive agent for PDAC, targeting a novel STAT3-DPYD pathway.

Analysis of very important pharmacogene variants in the Tibetan population from China.

Personalized medicine, the treatment best suited for an individual, is a hot field of clinical research in the world. Many recent studies have shown that genetic variations have a great influence on the treatment. This study aimed to identify the distribution differences of very important pharmacogene (VIP) variants between the Tibetan population and the other 26 populations from the 1000 Genomes project. Based on the PharmGKB database, we successfully genotyped 50 VIP variants located in 27 genes in the Tibetan population. We also compared the genotype frequencies of VIP variants between Tibetan population and the other 26 populations. Without adjustment, the Chi-square test showed that the only significant variant between Tibetans and every other group was rs1801159 in dihydropyrimidine dehydrogenase (DPYD), followed by rs1800566 in NAD(P)H quinone dehydrogenase 1 (NQO1) and rs1051296 in solute carrier family 19 member 1 (SLC19A1). After Bonferroni's multiple adjustments, the genotype frequencies distribution of DPYD rs1801159 was found to be different in Tibetans compared to the other 26 groups, apart from ACB and ASW. Moreover, genetic structure/F-statistics (Fst) analysis and the phylogenetic tree illustrated that Tibetans had a closer affinity with CDX, CHB, CHS, JPT and KHV. Our data will complement pharmacogenomics information of the Tibetan population and provide theoretical support for the realization of individualized medical treatment for Tibetans in the future.