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Purpose: Dihydropyrimidine dehydrogenase (DPD)-deficient cancer patients have been shown to develop severe toxicity after administration of 5-fluorouracil. Routine determination of DPD activity is limited by time-consuming and labor-intensive methods. The purpose of this study was to develop a simple and rapid 2-13 C-uracil breath test, which could be applied in most clinical settings to detect DPDdeficient cancer patients.Experimental Design: Fifty-eight individuals (50 "normal," 7 partially, and 1 profoundly DPD-deficient) ingested an aqueous solution of 2-13 C-uracil (6 mg/kg). 13 CO 2 levels were determined in exhaled breath at various time intervals up to 180 min using IR spectroscopy (UBiT-IR 300 ). DPD enzyme activity and DPYD genotype were determined by radioassay and denaturing high-performance liquid chromatography, respectively.Results: The mean (؎SE) C max , T max , ␦ over baseline values at 50 min (DOB 50 ) and cumulative percentage of 13 C dose recovered (PDR) for normal, partially, and profoundly DPD-deficient individuals were 186.4 ؎ 3.9, 117.1 ؎ 9.8, and 3.6 DOB; 52 ؎ 2, 100 ؎ 18.4, and 120 min; 174.1 ؎ 4.6, 89.6 ؎ 11.6, and 0.9 DOB 50 ; and 53.8 ؎ 1.0, 36.9 ؎ 2.4, and <1 PDR, respectively. The differences between the normal and DPD-deficient individuals were highly significant (all Ps <0.001).Conclusions: We demonstrated statistically significant differences in the 2-13 C-uracil breath test indices (C max , T max , DOB 50 , and PDR) among healthy and DPDdeficient individuals. These data suggest that a single time-point determination (50 min) could rapidly identify DPD-deficient individuals with a less costly and timeconsuming method that is applicable for most hospitals or physicians' offices.

Purpose: Dihydropyrimidine dehydrogenase (DPD) deficiency, a known pharmacogenetic syndrome associated with 5-fluorouracil (5-FU) toxicity, has been detected in 3% to 5% of the population. Genotypic studies have identified >32 sequence variants in the DPYD gene; however, in a number of cases, sequence variants could not explain the molecular basis of DPD deficiency. Recent studies in cell lines indicate that hypermethylation of the DPYD promoter might downegulate DPD expression. The current study investigates the role of methylation in cancer patients with an unexplained molecular basis of DPD deficiency. Experimental Design: DPD deficiency was identified phenotypically by both enzyme assay and uracil breath test, and genotypically by denaturing high-performance liquid chromatography. The methylation status was evaluated in PCR products (209 bp) of bisulfite-modified DPYD promoter, using a novel denaturing high-performance liquid chromatography method that distinguishes between methylated and unmethylated alleles. Clinical samples included five volunteers with normal DPD enzyme activity, five DPD-deficient volunteers, and five DPD-deficient cancer patients with a history of 5-FU toxicity. Results: No evidence of methylation was detected in samples from volunteers with normal DPD. Methylation was detected in five of five DPD-deficient volunteers and in three of five of the DPD-deficient cancer patient samples. Of note, one of the two samples from patients with DPD-deficient cancer with no evidence of methylation had the mutation DPYD*2A, whereas the other had DPYD*13. Discussion: Methylation of the DPYD promoter region is associated with down-regulation of DPD activity in clinical samples and should be considered as a potentially important regulatory mechanism of DPD activity and basis for 5-FU toxicity in cancer patients.Dihydropyrimidine dehydrogenase (DPD) enzyme deficiency, a known pharmacogenetic syndrome detected in 3% to 5% of the population (1), has been associated with toxicity to 5-fluorouracil (5-FU) cancer chemotherapy and death in some cases with profound deficiency of the enzyme (2). DPD is the first enzyme in a three-step catabolic pathway responsible for the degradation of f85% of administered 5-FU. Genotypic studies have identified >32 sequence variants in the DPYD gene (1, 3). Expression analysis of these variants showed that many were polymorphisms with no obvious functional significance (4), with the exception of a few mutations. One example commonly associated with DPD deficiency and severe toxicity to 5-FU is an intronic sequence variation (IVS14 + 1 G > A, DPYD*2A), which results in a truncated protein that lacks 55 amino acids due to the skipping of exon 14 (5). A second example is a less common mutation (1679T > G, I560S, DPYD*13), which is associated with decreased DPD activity and 5-FU toxicity (6) due to a nonconservative amino acid change from isoleucine to serine at codon 560 (I560), which is 100% conserved among human, mouse, rat, bovine, and pig species, suggesting its imp...

Histone deacetylase (HDAC) inhibitors are a new group of anticancer agents that have a potential role in the regulation of gene expression, induction of cell death, apoptosis and cell cycle arrest of cancer cells by altering the acetylation status of chromatin and other non-histone proteins. In clinical trials, HDAC inhibitors have demonstrated promising antitumour activity as monotherapy in cutaneous T-cell lymphoma and other haematological malignancies. In solid tumours, several HDAC inhibitors have been shown to be efficacious as single agents; however, results of most clinical trials were in favour of using HDAC inhibitors either prior to the initiation of chemotherapy or in combination with other treatments. Currently, the molecular basis of response to HDAC inhibitors in patients is not fully understood. In this review, we summarize the current status of HDAC inhibitors, as single agents or in combination with other agents in different phases of clinical trials. In most of the clinical trials, HDAC inhibitors were tolerable and exerted biological or antitumor activity. HDAC inhibitors have been studied in phase I, II and III clinical trials with variable efficacy. The combination of HDAC inhibitors with other anticancer agents including epigenetic or chemotherapeutic agents demonstrated favourable clinical outcome.