SN-38 is the active metabolite of irinotecan and it is metabolised through conjugation by uridine diphosphate glucuronosyl transferase (UGT1A1). The major toxicity of irinotecan therapy is diarrhoea, which has been related to the enzymatic activity of UGT1A1. We examined the influence of the UGT1A1 gene promoter polymorphism in the toxicity profile, in the response rate and in the overall survival (OS) in 95 patients with metastatic colorectal cancer treated with an irinotecan-containing chemotherapy. Genotypes were determined by analysing the sequence of TATA box of UGT1A1 of genomic DNA from the patients. Clinical parameters and genotypes were compared by univariate and multivariate statistical methods. The more frequent adverse effects were asthenia (34 patients), diarrhoea (29 patients) and neutropenia (20 patients). Severe diarrhoea was observed in 7/10 homozygous (70%) and 15/ 45 heterozygous (33%) in comparison to 7/40 (17%) wild-type patients (P ¼ 0.005). These results maintained the statistical significance in logistic regression analysis (P ¼ 0.01) after adjustment for other clinical relevant variables. The presence of severe haematological toxicity increased from wild-type patients to UGT1A1*28 homozygotes, but without achieving statistical significance. No relationship was found between the UGT1A1*28 genotypes and infection, nausea or mucositis. In univariate studies, patients with the UGT1A1*28 polymorphism showed a trend to a poorer OS (P ¼ 0.09). In the multivariate analysis, the genotype was not related to clinical response or to OS. The role of the UGT1A1 genotype as a predictor of toxicity in cancer patients receiving irinotecan demands the performance of a randomized trial to ascertain whether genotype-adjusted dosages of the drug can help to establish safe and effective doses not only for patients with the UGT1A1*28 homozygous genotype but also for those with the most common UGT1A1 6/6 or 6/7 genotype.

Thymidylate synthase (TS) is the primary target of 5-fluorouracil (5-FU).A VNTR polymorphism in the TS promoter region is associated with the efficacy of 5-FU-based chemotherapy in colorectal cancer. A common G>C SNP at the 12th nucleotide of the second repeat in the TS*3 alleles has been recently described. The combination of SNP and VNTR allows the definition of 3 TS alleles: *2, *3G and *3C. The aim of our study was to evaluate the predictive value of clinical response and survival of these new defined TS alleles. TS genotypes of 89 patients diagnosed with metastatic colorectal cancer and undergoing 5-FU-based chemotherapy were carried out. The clinical outcome was evaluated according to the genotype (high expression genotype: *2R/*3G; *3C/*3G; *3G/*3G; and low expression genotype: *2R/*2R; *2R/*3C; *3C/*3C. A higher overall response was observed in the group of patients with a low expression genotype (p ‫؍‬ 0.035). The probability of achieving a clinical response of patients with a low expression-related genotype was 2.9 higher than that of the other group (95% CI ‫؍‬ 1.03-5.6, p ‫؍‬ 0.04). The median time to progression was 12 months and 9 months in the low and high expression groups, respectively (p ‫؍‬ 0.07, log rank test). Overall survival was significantly longer in the low expression group. In this group the median OS was not achieved at 50 months of follow-up in contrast to the 20 months observed in the high expression group (p ‫؍‬ 0.03). TS genotype was an independent predictor of progression-free and overall survival in the Cox regression models after adjustment to the other clinical variables. The selection of patients who are likely to respond to 5-FU therapy may be considerably improved if the TS genotype were to include both the VNTR and the SNP located within the promoter region of the gene. © 2004 Wiley-Liss, Inc. Key words: 5-FU resistance; TS-polymorphism; colorectal cancer; fluoropyrimidine chemotherapyA high proportion of colorectal cancer, which is a leading cause of cancer-related morbidity and mortality in the Western world, is diagnosed at advanced stages when chemotherapy is required for its management. 5-Fluorouracil (5-FU) is a folate-pathway inhibitor that has been available for 50 years, and continues to be a mainstay of treatment of advanced disease. 1 This drug is a fluoropyrimidine that, on activation to the nucleotide form, develops a stable complex with thymidylate synthase (TS), inhibiting the activity of the enzyme. 2 TS catalyzes the reductive methylation of dUMP by 5,10-methylenetetrahydrofolate to form dTNP, which is a critical reaction for cell proliferation. 3 Early in vitro studies have demonstrated more resistance to 5-FU of cell lines with high TS expression 4 or transfected with wild-type TS cDNA. 5 A number of studies have been published indicating that patients with high tumor levels of TS are unlikely to respond to infusion treatment with 5-FU, whereas patients with low levels have response rates that are higher than expected. 6 -13 The agreement between these...

Fluorouracil (5-FU) is widely used in the treatment of colorectal cancer. Methylenetetrahydrofolate reductase (MTHFR) may play a central role in the action of 5-FU, an inhibitor of thymidylate synthase, by converting 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate. The aim of this study was to ascertain whether two polymorphisms in the MTHFR gene (677C>T and 1298 A>C) could be used as genomic predictors of clinical response to fluoropyrimidine-based chemotherapy (in combination with irinotecan or oxaliplatin). Ninety-four patients diagnosed with metastatic colorectal cancer and undergoing 5-FU-containing chemotherapy as a first line treatment were studied. The results suggest that the MTHFR genotype cannot be considered as an independent factor of outcome in colorectal cancer patients under 5-FU-based chemotherapy.

The CYP2D6 gene codes for a P450 monooxygenase which is involved in the biotransformation of a large number of commonly prescribed drugs. Adverse drug effects and therapeutic failure can be related to abnormal CYP2D6 activity. We investigated the allele and genotype frequencies of cytochrome P4502D6 in a Spanish population to predict the prevalence of ultra-rapid and poor metabolizer phenotypes in our population and to design a feasible CYP2D6 genotyping protocol. The study included 105 healthy unrelated Spanish Caucasian volunteers. CYP2D6 genotyping was performed by a combination of long-PCR, direct sequencing and allele-specific real-time PCR. The frequency of the wild-type CYP2D6*1 allele was 31%. The alleles coding for slightly (CYP2D6*2) or moderately (*9 and *10) reduced activity showed frequencies of 40.47, 2.38 and 1.90%, respectively. Frequencies of defective alleles *3, *4, *5 and *6 were 0.95, 13.8, 3.33 and 0.95%, respectively. The defective CYP2D6 alleles *7, *8, *12, *14, *15 and *21 were not found. Duplicated CYP2D6 alleles were detected at a frequency of 4.27%. Our protocol allows the identification of the four inactive CYP2D6 alleles (*3, *4, *5 and *6) and the detection of alleles with CYP2D6 *1, CYP2D6 *2 and CYP2D6*4 gene duplications. Testing for this reduced CYP2D6 allele set would facilitate its use in clinical practice by assisting in the development of individualized pharmacotherapy.

Summary Chronic lymphocytic leukaemia (CLL) is the commonest form of leukaemia in adults in Western countries. We performed multiplex ligation‐dependent probe amplification (MLPA) analysis in 50 CLL patients to identify multiple genomic CLL‐specific targets, including genes located at 13q14, 17p13 (TP53), 11q23 (ATM) and chromosome 12, and compared the results with those obtained with fluorescence in situ hybridization (FISH). There was a good correlation between MLPA and FISH results, as most alterations (89%) were detected by both techniques. Only three cases with a low percentage (<25%) of cells carrying the alterations were not detected by MLPA. On the other hand, as MLPA uses multiple probes it identified intragenic or small alterations undetected by FISH in three cases. MLPA also detected alterations in 8q24 (MYC) and 6q25–26. In summary, unlike interphase FISH, MLPA enabled the simultaneous analysis of many samples with automated data processing at a low cost. Therefore, the combination of robust multiplexing and high throughput makes MLPA a useful technique for the analysis of genomic alterations in CLL.