Evaluating the role of ENOSF1 and TYMS variants as predictors in fluoropyrimidine-related toxicities: An IPD meta-analysis.

To assess the proposed associations of the c.742-227G>A (rs2612091) polymorphism within the Enolase Superfamily Member 1 gene (ENOSF1) and two variants in the adjacent Thymidylate Synthase gene (TYMS): the 5'VNTR 28bp-repeat (rs45445694) and 3'UTR 6bp-indel (rs11280056) with severe toxicity in fluoropyrimidine-treated cancer patients, we performed an individual patient data meta-analysis. Only studies investigating all three-abovementioned variants with fluoropyrimidine-related toxicities were considered for meta-analysis. Associations were tested individually for each study using multivariate regression. Meta-analysis was performed using a random-effects model. One-stage multivariate regressions including tests for independent SNP effects were applied to investigate individual effects of the variants. Multivariate haplotype regression analyses were performed on a pooled dataset to test multi-SNP effects. Of four studies including 2'067 patients, 1'912 were eligible for meta-analysis. All variants were exclusively associated with severe hand-foot-syndrome (HFS) (TYMS 2R: OR = 1.50, p = 0.0002; TYMS 6bp-ins: OR = 1.42 p = 0.0036; ENOSF1 c.742-227G: OR = 1.64 p < 0.0001, per allele). We observed independent effects for ENOSF1 c.742-227G>A and the TYMS 28bp-repeat: each toxicity-associated allele increased the risk for severe HFS (OR = 1.32 per allele, p < 0.0001). Patients homozygous for both variants were at the 3-fold higher risk for severe HFS compared to wild-type patients. Our results confirm an essential role for ENOSF1 c.742-227G and TYMS 2R-alleles in the development of fluoropyrimidine-related HFS. This suggests an important function of these genes in the development of severe HFS. Furthermore, these variants might help stratify patients in studies investigating measures of HFS prevention.

Dihydropyrimidinase and ß-ureidopropionase gene variation and severe fluoropyrimidine-related toxicity.

AIMS: To assess the association of DPYS and UPB1 genetic variation, encoding the catabolic enzymes downstream of dihydropyrimidine dehydrogenase, with early-onset toxicity from fluoropyrimidine-based chemotherapy. PATIENTS & METHODS: The coding and exon-flanking regions of both genes were sequenced in a discovery subset (164 patients). Candidate variants were genotyped in the full cohort of 514 patients. RESULTS & CONCLUSIONS: Novel rare deleterious variants in DPYS (c.253C > T and c.1217G > A) were detected once each in toxicity cases and may explain the occurrence of severe toxicity in individual patients, and associations of common variants in DPYS (c.1-1T > C: p(adjusted) = 0.003; OR = 2.53; 95% CI: 1.39-4.62, and c.265-58T > C: p(adjusted) = 0.039; OR = 0.61; 95% CI: 0.38-0.97) with 5-fluorouracil toxicity were replicated.

Predicting 5-fluorouracil toxicity: DPD genotype and 5,6-dihydrouracil:uracil ratio.

AIM: Decreased DPD activity is a major cause of 5-fluorouracil (5-FU) toxicity, but known reduced-function variants in the DPD gene (DPYD) explain only a part of DPD-related 5-FU toxicities. Here, we evaluated the baseline (pretherapeutic) plasma 5,6-dihydrouracil:uracil (UH2:U) ratio as a marker of DPD activity in the context of DPYD genotypes. MATERIALS & METHODS: DPYD variants were genotyped and plasma U, UH2 and 5-FU concentrations were determined by liquid chromatography-tandem mass spectrometry in 320 healthy blood donors and 28 cancer patients receiving 5-FU-based chemotherapy. RESULTS: Baseline UH2:U ratios were strongly correlated with generally low and highly variable U concentrations. Reduced-function DPYD variants were only weakly associated with lower baseline UH2:U ratios. However, the interindividual variability in the UH2:U ratio was reduced and a stronger correlation between ratios and 5-FU exposure was observed in cancer patients during 5-FU administration. CONCLUSION: These results suggest that the baseline UH2:U plasma ratio in most individuals reflects the nonsaturated state of DPD and is not predictive of decreased DPD activity. It may, however, be highly predictive at increased substrate concentrations, as observed during 5-FU administration.

Signal control by self-assembly of fluorophores in a molecular beacon--a model study.

Pyrene excimer fluorescence is efficiently regulated through formation of π-stacked aggregates between dialkynylpyrene (Y) and perylenediimide (E) residues located in the stem region of a molecular beacon (MB). The building blocks form organized, multichromophoric complexes in the native form. Hybridization to the target results in a conformational reorganization of the chromophores. The nature of the aggregates was investigated by changing the number of chromophores and natural base pairs in the beacon stem. The formation of different types of complexes (EYEY→YEY→EY) is revealed by characteristic spectroscopic changes. The data show that signal control is an intrinsic property of the interacting chromophores. The directed assembly of non-nucleosidic chromophores can be used for the generation of an on/off switch of a fluorescence signal. The concept may find applications in various types of light-based input/output systems.