Early Assessment of Thiopurine Metabolites Identifies Patients at Risk of Thiopurine-induced Leukopenia in Inflammatory Bowel Disease.

BACKGROUND AND AIMS: Only a quarter of thiopurine-induced myelotoxicity in inflammatory bowel disease [IBD] patients is related to thiopurine S-methyltransferase deficiency. We determined the predictive value of 6-thioguanine nucleotide [6-TGN] and 6-methylmercaptopurine ribonucleotide [6-MMPR] concentrations 1 week after initiation [T1] for development of leukopenia during the first 8 weeks of thiopurine treatment. METHODS: The study was performed in IBD patients starting thiopurine therapy as part of the Dutch randomized controlled TOPIC trial [ClinicalTrials.gov NCT00521950]. Blood samples for metabolite measurement were collected at T1. Leukopenia was defined by leukocyte counts of <3.0 × 109/L. For comparison, patients without leukopenia who completed the 8 weeks on the stable dose were selected from the first 272 patients of the TOPIC trial. RESULTS: Thirty-two patients with, and 162 patients without leukopenia were analysed. T1 threshold 6-TGN concentrations of 213 pmol/8 × 108 erythrocytes and 3525 pmol/8 × 108 erythrocytes for 6-MMPR were defined: patients exceeding these values were at increased leukopenia risk (odds ratio [OR] 6.2 [95% CI: 2.8-13.8] and 5.9 [95% CI: 2.7-13.3], respectively). Leukopenia rates were higher in patients treated with mercaptopurine, compared with azathioprine (OR 7.3 [95% CI: 3.1-17.0]), and concurrent anti-TNF therapy (OR 5.1 [95% CI: 1.6-16.4]). Logistic regression analysis of thiopurine type, threshold concentrations, and concurrent anti-tumour necrosis factor [TNF] therapy revealed that elevations of both T1 6-TGN and 6-MMPR resulted in the highest risk for leukopenia, followed by exceeding only the T1 6-MMPR or 6-TGN threshold concentration (area under the curve 0.84 [95% CI: 0.76-0.92]). CONCLUSIONS: In ~80% of patients, leukopenia could be explained by T1 6-TGN and/or 6-MMPR elevations. Validation of the predictive model is needed before implementing in clinical practice.

The Prevalence of Nodular Regenerative Hyperplasia in Inflammatory Bowel Disease Patients Treated with Thioguanine Is Not Associated with Clinically Significant Liver Disease.

BACKGROUND: Nodular regenerative hyperplasia (NRH) of the liver is associated with inflammatory-mediated diseases and certain drugs. There is conflicting data on the prevalence of NRH and its clinical implications in inflammatory bowel disease (IBD) patients treated with thioguanine. METHODS: A retrospective cohort study involving 7 Dutch centers comprised all IBD patients who were being treated with thioguanine and underwent a liver biopsy as part of the standard toxicity screening. Liver biopsy specimens were reviewed by 2 experienced liver pathologists. Clinical data as well as liver chemistry, blood counts, and abdominal imaging were collected. RESULTS: One hundred eleven IBD patients who submitted to liver biopsy were treated with thioguanine in a daily dose of 0.3 mg/kg for a median duration of 20 (4-64) months. NRH was detected in 6% of patients (7; 95% confidence interval, 3-14 patients). Older age (P = 0.02), elevated gamma-glutamyl transferase (P = 0.01) and alkaline phosphatase (P = 0.01) levels, a higher mean corpuscular volume (P = 0.02), and a lower platelet or leukocyte count (P < 0.01 and P = 0.02, respectively) were associated with NRH. Three of the 7 patients with NRH did not have any associated clinical symptoms or signs. The other 4 had minor biochemical abnormalities only. Ultrasonography revealed splenomegaly in 3 of the 78 patients (4%; 95% confidence interval, 0%-9%), only one of whom had NRH. There was no clinically overt portal hypertension. CONCLUSIONS: The prevalence of NRH was 6% in liver biopsies obtained from IBD patients treated with thioguanine. Histopathological irregularities including NRH were not associated with clinically significant findings over the period of observation.

Adherence to surveillance guidelines after removal of colorectal adenomas: a large, community-based study.

OBJECTIVE: To determine adherence to recommended surveillance intervals in clinical practice. DESIGN: 2997 successive patients with a first adenoma diagnosis (57% male, mean age 59 years) from 10 hospitals, who underwent colonoscopy between 1998 and 2002, were identified via Pathologisch Anatomisch Landelijk Geautomatiseerd Archief: Dutch Pathology Registry. Their medical records were reviewed until 1 December 2008. Time to and findings at first surveillance colonoscopy were assessed. A surveillance colonoscopy occurring within ± 3 months of a 1-year recommended interval and ± 6 months of a recommended interval of 2 years or longer was considered appropriate. The analysis was stratified by period per change in guideline (before 2002: 2-3 years for patients with 1 adenoma, annually otherwise; in 2002: 6 years for 1-2 adenomas, 3 years otherwise). We also assessed differences in adenoma and colorectal cancer recurrence rates by surveillance timing. RESULTS: Surveillance was inappropriate in 76% and 89% of patients diagnosed before 2002 and in 2002, respectively. Patients eligible under the pre-2002 guideline mainly received surveillance too late or were absent (57% of cases). For patients eligible under the 2002 guideline surveillance occurred mainly too early (48%). The rate of advanced neoplasia at surveillance was higher in patients with delayed surveillance compared with those with too early or appropriate timed surveillance (8% vs 4-5%, p<0.01). CONCLUSIONS: There is much room for improving surveillance practice. Less than 25% of patients with adenoma receive appropriate surveillance. Such practice seriously hampers the effectiveness and efficiency of surveillance, as too early surveillance poses a considerable burden on available resources while delayed surveillance is associated with an increased rate of advanced adenoma and especially colorectal cancer.

Features of adenoma and colonoscopy associated with recurrent colorectal neoplasia based on a large community-based study.

BACKGROUND & AIMS: We investigated adenoma and colonoscopy characteristics that are associated with recurrent colorectal neoplasia based on data from community-based surveillance practice. METHODS: We analyzed data of 2990 consecutive patients (55% male; mean age 61 years) newly diagnosed with adenomas from 1988 to 2002 at 10 hospitals throughout The Netherlands. Medical records were reviewed until December 1, 2008. We excluded patients with hereditary colorectal cancer (CRC) syndromes, a history of CRC, inflammatory bowel disease, or without surveillance data. We analyzed associations among adenoma number, size, grade of dysplasia, villous histology, and location with recurrence of advanced adenoma (AA) and nonadvanced adenoma (NAA). We performed a multivariable multinomial logistic regression analysis to estimate odds ratios (ORs) and 95% confidence intervals (CIs). RESULTS: During the surveillance period, 203 (7%) patients were diagnosed with AA and 954 (32%) patients with NAA. The remaining 1833 (61%) patients had no adenomas during a median follow-up of 48 months. Factors associated with AA during the surveillance period included baseline number of adenomas (ORs ranging from 1.6 for 2 adenomas; 95% CI: 1.1-2.4 to 3.3 for ≥5 adenomas; 95% CI: 1.7-6.6), adenoma size ≥10 mm (OR = 1.7; 95% CI: 1.2-2.3), villous histology (OR = 2.0; 95% CI: 1.2-3.2), proximal location (OR = 1.6; 95% CI: 1.2-2.3), insufficient bowel preparation (OR = 3.4; 95% CI: 1.6-7.4), and only distal colonoscopy reach (OR = 3.2; 95% CI: 1.2-8.5). Adenoma number had the greatest association with NAA. High-grade dysplasia was not associated with AA or NAA. CONCLUSIONS: Large size and number, villous histology, proximal location of adenomas, insufficient bowel preparation, and poor colonoscopy reach were associated with detection of AA during surveillance based on data from community-based practice. These characteristics should be used jointly to develop surveillance policies for adenoma patients.

[Irritable bowel syndrome: from guideline to made-to-measure care?]. / Prikkelbaredarmsyndroom: van richtlijn tot maatwerk?

The new guideline on irritable bowel syndrome (IBS) advocates distinguishing IBS patients who predominantly suffer from constipation from those who mainly suffer from diarrhoea or from alternating bouts of diarrhoea and constipation. In the latter two groups, coeliac disease should be excluded, as should lactose intolerance if at all possible. Since there is no gold standard for the treatment of IBS a thorough explanation of the condition to patients is recommended.

Therapeutic drug monitoring of thiopurine metabolites in adult thiopurine tolerant IBD patients on maintenance therapy.

BACKGROUND AND AIMS: Therapeutic drug monitoring of active metabolites of thiopurines, azathioprine and 6-mercaptopurine, is relatively new. The proposed therapeutic threshold level of the active 6-thioguanine nucleotides (6-TGN) is ≥235 pmol/8×10(8) erythrocytes. The aim of this prospective cross-sectional study was to compare 6-TGN levels in adult thiopurine tolerant IBD patients with an exacerbation with those in remission, and to determine the therapeutic 6-TGN cut-off level. METHODS: Hundred IBD patients were included. Outcome measures were thiopurine metabolite levels, calculated therapeutic 6-TGN cut-off level, CDAI/CAI scores, thiopurine dose and TPMT enzyme activity. RESULTS: Forty-one patients had an exacerbation, 59 patients were in remission. In 17% of all patients 6-TGN levels were compatible with non-compliance. The median 6-TGN levels were not significantly different between the exacerbation and remission group (227 versus 263 pmol/8×10(8) erythrocytes, p=0.29). The previous reported therapeutic 6-TGN cut-off level of 235 pmol/8×10(8) erythrocytes was confirmed in this study. Twenty-six of the 41 patients (63%) with active disease had 6-TGN levels below this threshold and 24 of 59 IBD patients (41%) in clinical remission (p=0.04). CONCLUSIONS: Thiopurine non-compliance occurs frequently both in active and quiescent disease. 6-TGN levels below or above the therapeutic threshold are associated with a significant higher chance of IBD exacerbation and remission, respectively. These data support the role of therapeutic drug monitoring in thiopurine maintenance therapy in IBD to reveal non-compliance or underdosing, and can be used as a practical tool to optimize thiopurine therapy, especially in case of thiopurine non-response.

Red meat intake-induced increases in fecal water genotoxicity correlate with pro-carcinogenic gene expression changes in the human colon.

Red meat consumption is associated with an increased colorectal cancer (CRC) risk, which may be due to an increased endogenous formation of genotoxic N-nitroso compounds (NOCs). To assess the impact of red meat consumption on potential risk factors of CRC, we investigated the effect of a 7-day dietary red meat intervention in human subjects on endogenous NOC formation and fecal water genotoxicity in relation to genome-wide transcriptomic changes induced in colonic tissue. The intervention showed no effect on fecal NOC excretion but fecal water genotoxicity significantly increased in response to red meat intake. Colonic inflammation caused by inflammatory bowel disease, which has been suggested to stimulate endogenous nitrosation, did not influence fecal NOC excretion or fecal water genotoxicity. Transcriptomic analyses revealed that genes significantly correlating with the increase in fecal water genotoxicity were involved in biological pathways indicative of genotoxic effects, including modifications in DNA damage repair, cell cycle, and apoptosis pathways. Moreover, WNT signaling and nucleosome remodeling pathways were modulated which are implicated in human CRC development. We conclude that the gene expression changes identified in this study corroborate the genotoxic potential of diets high in red meat and point towards a potentially increased CRC risk in humans.

N-nitroso compound exposure-associated transcriptomic profiles are indicative of an increased risk for colorectal cancer.

Endogenous formation of N-nitroso compounds (NOCs), which are known animal carcinogens, could contribute to human carcinogenesis but definitive evidence is still lacking. To investigate the relevance of NOCs in human colorectal cancer (CRC) development, we analyzed whole genome gene expression modifications in human colon biopsies in relation to fecal NOC exposure. We had a particular interest in patients suffering from intestinal inflammation as this may stimulate endogenous NOC formation, and consequently predispose to CRC risk. Inflammatory bowel disease (IBD) patients diagnosed with ulcerative colitis and irritable bowel syndrome patients without inflammation, serving as controls, were therefore recruited. Fecal NOC were demonstrated in the majority of subjects. By associating gene expression levels of all subjects to fecal NOC levels, we identified a NOC exposure-associated transcriptomic response that suggests that physiological NOC concentrations may potentially induce genotoxic responses and chromatin modifications in human colon tissue, both of which are linked to carcinogenicity. In a network analysis, chromatin modifications were linked to 11 significantly modulated histone genes, pointing towards a possible epigenetic mechanism that may be relevant in comprehending NOC-induced carcinogenesis. In addition, pro-inflammatory transcriptomic modifications were identified in visually non-inflamed regions of the IBD colon. However, fecal NOC levels were slightly but not significantly increased in IBD patients, suggesting that inflammation did not strongly stimulate NOC formation. We conclude that NOC exposure is associated with gene expression modifications in the human colon that may suggest a potential role of these compounds in CRC development.

Psychometric validation of the Dutch translation of the quality of life in reflux and dyspepsia (QOLRAD) questionnaire in patients with gastroesophageal reflux disease.

BACKGROUND: The Quality of Life in Reflux and Dyspepsia (QOLRAD) questionnaire is one of the best-characterized disease-specific instruments that captures health-related problems and symptom-patterns in patients with gastroesophageal reflux disease (GERD). This paper reports the psychometric validation of a Dutch translation of the QOLRAD questionnaire in gastroenterology outpatients with GERD. METHODS: Patients completed the QOLRAD questionnaire at visit 1 (baseline), visit 2 (after 2, 4 or 8 weeks of acute treatment with esomeprazole 40 mg once daily), and visit 4 (after 6 months with on-demand esomeprazole 40 mg once daily or continuous esomeprazole 20 mg once daily). Symptoms were assessed at each visit, and patient satisfaction was assessed at visits 2 and 4. RESULTS: Of the 1166 patients entered in the study, 97.3% had moderate or severe heartburn and 55.5% had moderate or severe regurgitation at baseline. At visit 2, symptoms of heartburn and regurgitation were mild or absent in 96.7% and 97.7%, respectively, and 95.3% of patients reported being satisfied with the treatment. The internal consistency and reliability of the QOLRAD questionnaire (range: 0.83-0.92) supported construct validity. Convergent validity was moderate to low. Known-groups validity was confirmed by a negative correlation between the QOLRAD score and clinician-assessed severity of GERD symptoms. Effect sizes (1.15-1.93) and standardized response means (1.17-1.86) showed good responsiveness to change. GERD symptoms had a negative impact on patients' lives. CONCLUSIONS: The psychometric characteristics of the Dutch translation of the QOLRAD questionnaire were found to be satisfactory, with good reliability and responsiveness to change, although convergent validity was at best moderate.

Methylation status of CpG islands in the promoter region of genes differentially expressed in colonic mucosa from adenoma patients and controls in response to altered vegetable intake.

Vegetables may protect against colorectal cancer (CRC) via changes in gene expression involved in anticarcinogenic mechanisms. There is considerable evidence that aberrant DNA methylation plays an important role in carcinogenesis. Furthermore, DNA methylation can be affected by dietary components. Therefore, in the present study, we investigated the DNA methylation status of CpG dinucleotides within the promoter region of the four genes protein kinase C b 1, ornithine decarboxylase 1, fos proto-oncogene and 5,10-methylenetetrahydrofolate reductase in the colon of female sporadic adenoma patients and healthy controls. These genes were chosen because their expression was modulated in response to altered vegetable intake, they are functionally relevant for CRC; they have CpG islands in their promoter region, and a methylation-specific restriction enzyme is available to permit quantitative assay. No significant differences in extent of methylation in colon DNA were detected for any of the four genes in both adenoma polyp patients and healthy controls after altering vegetable intake. Interestingly, before the intervention, ornithine decarboxylase 1 promoter methylation was lower in the colonic mucosa of the adenoma polyp patients when compared with healthy control subjects, which may explain the increased ornithine decarboxylase 1 activity in CRC reported in the literature. In conclusion, we found no evidence that changes in promoter methylation were responsible for differences in expression of four genes in the human colonic mucosa in response to altered vegetable intake. The mechanism(s) responsible for this altered gene expression and, indeed, potential effects on methylation of other genes remain to be determined.

Dose-dependent influence of 5-aminosalicylates on thiopurine metabolism.

INTRODUCTION: Studies indicated that 5-aminosalicylates (5-ASA) may influence the metabolism of thiopurines; however, conclusions were restricted as a result of number of patients or study design. AIM: To determine the influence of 5-ASA on thiopurine metabolism, we performed a prospective multicenter pharmacokinetic interaction study of two different 5-ASA dosages (2 g daily followed by 4 g daily) in 26 inflammatory bowel disease (IBD) patients during steady-state AZA or 6-MP therapy. RESULTS: The 4-wk coadministration of 2 g 5-ASA daily, followed by a 4-wk period of 4 g 5-ASA daily, led to a statistical significant increase of 40% (absolute 84 pmol/8x10(8) RBC) and 70% (absolute 154 pmol/8x10(8) RBC) in 6-thioguaninenucleotide levels (6-TGN), respectively. A rise in 6-TGN levels was observed in 100% of patients after a 4-wk period of 4 g 5-ASA daily. The 6-methylmercaptopurine-ribonucleotide levels did not change. Signs of myelotoxicity were observed in 7.7% of patients (N=2). CONCLUSIONS: The level of the pharmacologically active 6-TGN significantly increases in a dose-dependent manner during 5-ASA coadministration. IBD patients who are unresponsive or refractory to standard thiopurine therapy may benefit from the coadministration of 5-ASA, leading to an increase in 6-TGN levels.

Treatment of irritable bowel syndrome with osteopathy: results of a randomized controlled pilot study.

BACKGROUND AND AIM: Effective treatment for irritable bowel syndrome (IBS) is not yet available. Osteopathy is a manual treatment which relies on mobilizing and manipulating procedures in order to relieve complaints. In the present study, a randomized controlled trial was carried out to evaluate the effects of osteopathic treatment for IBS. METHODS: Eligible IBS patients were randomized between osteopathy and standard care. Follow-up was 6 months and validated means of follow-up were used. After 1, 3 and 6 months an overall assessment of symptoms was noted and a symptom score was obtained on a 5-point Likert scale. Quality of life (QOL) was scored with the standardized IBSQOL 2000 questionnaire and the Functional Bowel Disorder Severity Index was used. RESULTS: Twenty patients were randomized into the osteopathy group (OG) and 19 patients were included in the standard care group (SCG). Sixty-eight percent of patients in the OG noted definite overall improvement in symptoms and 27% showed slight improvement. One patient (5%) was free of symptoms at the end of the study. In the SCG, 18% noted definite improvement, 59% showed slight improvement, and in 17% worsening of symptoms was present. The difference in change in overall symptomatic improvement was statistically significant in favor of the osteopathic treatment (P < 0.006). Mean Functional Bowel Disorder Severity Index (FBDSI) score in the OG decreased from 174 to 74 at 6 months (P < 0.0001). Also, a significant decrease was noted in the SCG from 171 to 119 (P < 0.0001). However, the decrease in the OG was significantly higher compared with the standard treatment (P = 0.02). Mean symptom score in the OG decreased from 9.1 to 6.8 but this did not reach statistical significance. In the SCG, no change in symptom score occurred (8.7 vs 10). At 6 months, the score in the OG was significantly lower (6.8 vs 10; P = 0.02). The QOL score increased in the OG at 111 versus 129 (P < 0.009). In the SCG an increase was also noted, but this was not statistically significant (109 vs 121). CONCLUSION: Osteopathic therapy is a promising alternative in the treatment of patients with IBS. Patients treated with osteopathy overall did better, with respect to symptom score and QOL.

Pharmacokinetics of 6-thioguanine in patients with inflammatory bowel disease.

6-Thioguanine (6-TG) seems to be an attractive alternative in both AZA- and 6-MP-intolerant and -resistant IBD populations. However, little is known of 6-TG pharmacokinetics, metabolite levels, and their correlation with drug efficacy and toxicity in IBD patients. This study reports the 6-TG pharmacokinetics in a population of IBD patients and the predictive value of metabolite concentrations. Red blood cell (RBC) 6-thioguanine nucleotide (6-TGN) concentrations were measured in 28 IBD patients at t = 1, 2, 4, and 8 weeks after starting 6-TG, 20 mg once daily. Outcome measures included mean 6-TGN concentrations (+/-95% confidence interval [CI95%]) and their associations with TPMT genotype, 6-TG dose, and hematological, hepatic, pancreatic, and efficacy parameters during the 8 week period. Steady-state 6-TGN concentrations were reached after 4 weeks, indicating a half-life of approximately 5 days, and measured 856 (CI95% 715-997) pmol/8 x 10 RBCs. Large interpatient variability occurred at all time-points. No correlation was found between steady-state 6-TGN concentrations and drug dose per kilogram body weight. No significant differences in 6-TGN concentrations were found between patients with adverse events and patients without any event. Also, mean 6-TGN concentrations did not differ in patients with active disease versus patients in remission. In IBD patients on 6-TG treatment, large interindividual differences in metabolite concentrations occur. In our population, we could not demonstrate a clear relationship between 6-TGN concentrations on one hand and toxicity and efficacy on the other, as exist in AZA- and 6-MP-treated patients.

On tolerability and safety of a maintenance treatment with 6-thioguanine in azathioprine or 6-mercaptopurine intolerant IBD patients.

AIM: To determine the tolerability and safety profile of a low-dose maintenance therapy with 6-TG in azathioprine (AZA) or 6-mercaptopurine (6-MP) intolerant inflammatory bowel disease (IBD) patients over a treatment period of at least 1 year. METHODS: Database analysis. RESULTS: Twenty out of ninety-five (21%) patients discontinued 6-TG (mean dose 24.6 mg; mean 6-TGN level 540 pmol/8 x 10(8) RBC) within 1 year. Reasons for discontinuation were GI complaints (31%), malaise (15%) and hepatotoxicity (15%). Hematological events occurred in three patients, one discontinued treatment. In the 6-TG-tolerant group, 9% (7/75) could be classified as hepatotoxicity. An abdominal ultrasound was performed in 54% of patients, one patient had splenomegaly. CONCLUSION: The majority of AZA or 6-MP-intolerant IBD patients (79%) is able to tolerate maintenance treatment with 6-TG (dosages between 0.3 and 0.4 mg/kg per d). 6-TG may still be considered as an escape maintenance immunosuppressant in this difficult to treat group of patients, taking into account potential toxicity and efficacy of other alternatives. The recently reported hepatotoxicity is worrisome and 6-TG should therefore be administered only in prospective trials.

The CYP1A2-164A-->C polymorphism (CYP1A2*1F) is associated with the risk for colorectal adenomas in humans.

Colorectal cancer (CRC) is believed to be related to the intake of processed meat and the formed heterocyclic aromatic amines (HCA) herein, which are metabolically activated by the enzymes cytochrome P4501A2 (CYP1A2) and N-acetyltransferase 2 (NAT2). The influence of genotypic and phenotypic variations for CYP1A2 and NAT2 on the risk for colorectal adenomas was investigated in 94 individuals at different risk of developing CRC. Significant associations were found between the CYP1A2-164A-->C polymorphism (CYP1A2*1F) and the risk of colorectal adenomas, suggesting that the studied polymorphism plays an important role in CRC risk in humans.

Neutrophil-mediated formation of carcinogenic N-nitroso compounds in an in vitro model for intestinal inflammation.

In order to study neutrophil-mediated formation of carcinogenic N-nitroso compounds as a mechanism of inflammation-related colon carcinogenesis, we designed an in vitro model for intestinal inflammation, consisting of a coincubation system with human colon cells (Caco-2 cells) and activated human neutrophils (PMN), as important immunoreactive cells. We investigated whether nitrosamines and nitrosamides could be formed upon addition of dimethylamine, morpholine and methylurea to the coincubations as nitrosatable precursors, which are known to produce carcinogenic N-nitroso compounds. Incubations of pure nitric oxide with dimethylamine and morpholine showed that NO-mediated formation of nitrosodimethylamine and nitrosomorpholine is possible under the incubation conditions. During the coincubations of activated PMN and Caco-2 cells, 0.34 nmol nitrite/10(6) PMN was produced. Dose-dependent formation of NMOR was observed in this PMN/Caco-2 system; addition of 5mM morpholine resulted in a significantly increased NMOR formation of 4.2 nM. However, no detectable NDMA and methylnitrosourea were formed in this coincubation system. These results suggest that activated human neutrophils are able to synthesize carcinogenic N-nitrosamines, e.g. NMOR, which implies a risk of colon carcinogenesis during chronic inflammation. However, the observed relatively low level of nitrosation suggests that also other risk factors are contributing to the association between chronic inflammation and colon cancer risk.

Altered vegetable intake affects pivotal carcinogenesis pathways in colon mucosa from adenoma patients and controls.

The evidence from epidemiological and experimental studies that vegetables reduce the risk of colorectal cancer is convincing. However, the involved genes and genetic pathways are not clear. The aim of this study was to identify genes that are modulated in vivo in colorectal mucosa by vegetables, and to investigate whether colon adenoma patients respond differently compared with healthy controls. Twenty female adenoma patients and eight healthy controls were randomly split into two groups of ten and four persons, respectively, receiving either a 50% decreased (=75 g/day) or doubled (=300 g/day) intake of vegetables for 2 weeks. In order to assess the effects on gene expression at the target level, colorectal biopsies were collected before and after the intervention. Total RNA was isolated from the biopsies to measure gene expression of 597 genes relevant for responses to xenobiotics by microarray technology, followed by confidence analyses to identify differentially expressed genes. Mainly genes related to cell cycle control and genes for oxidoreductase activities were over-represented in the list of modulated genes. Twenty genes were modulated, which are known to be related to (colon)carcinogenesis. Seven genes were similarly modulated in patients and controls, for example fos proto-oncogene and ornithine decarboxylase. Thirteen genes were modulated differently in patients compared with controls, including cyclooxygenase-2 and human mdm2-A in patients and cytochrome P45027B1, -2C19, -2D6, -2C9 and -3A4 in controls. Almost all the effects on modulating the expression of genes by altering vegetable intake can be mechanistically linked to cellular processes that explain either prevention of colorectal cancer risk by high vegetable intake or increased colorectal cancer risk by low vegetable intake. Furthermore, it seems that vegetables in patients affect genes involved in the late stage of colorectal cancer, whereas in controls genes involved in the initiation phase are modulated.

Some cases demonstrating the clinical usefulness of therapeutic drug monitoring in thiopurine-treated inflammatory bowel disease patients.

The thiopurines azathioprine and 6-mercaptopurine (6-MP) are effective drugs in steroid-dependent and refractory inflammatory bowel disease patients. Therapeutic drug monitoring (TDM) is a new concept to improve drug efficacy and prevent toxic adverse events. As thiopurine metabolism is influenced by genetic polymorphisms of methylating enzymes, metabolite levels may vary considerably, enabling significant adverse effects. In the present paper five patients are described to demonstrate the clinical usefulness of TDM when applying thiopurines for inflammatory bowel disease. Emphasized are patients with liver function test abnormalities and myelosuppression due to inappropriate 6-MP metabolite levels, and subsequently the treatment of these events. In addition, sophisticated 6-MP metabolite level-guided therapy, including non-compliance, is demonstrated. These cases demonstrate that TDM may improve effectivity and safety of thiopurine treatment.

Pharmacokinetics of 6-mercaptopurine in patients with inflammatory bowel disease: implications for therapy.

Proper prospective pharmacokinetic studies of 6-mercaptopurine (6-MP) in inflammatory bowel disease (IBD) patients are lacking. As a result, conflicting recommendations have been made for metabolite monitoring in routine practice. The authors have evaluated 6-MP pharmacokinetics in IBD patients, including the genetic background for thiopurine methyltransferase (TPMT). Red blood cell (RBC) 6-thioguanine nucleotide (6-TGN) and 6-methylmercaptopurine ribonucleotide (6-MMPR) concentrations were measured in 30 IBD patients at 1, 2, 4, and 8 weeks after starting 6-MP, 50 mg once daily. Outcome measures included mean 6-TGN and 6-MMPR concentrations (+/- 95% confidence interval, CI95%) and their associations with TPMT genotype, 6-MP dose, and hematologic, hepatic, pancreatic, and efficacy parameters during the 8-week period. Steady-state concentrations were reached after 4 weeks, indicating a half-life of approximately 5 days for both 6-TGN and 6-MMPR; the concentrations were 368 (CI95% 284-452) and 2837 (CI95% 2101-3573) pmol/8 x 10 RBCs, respectively. Large interpatient variability occurred at all time points. TPMT genotype correlated with 6-TGN concentrations (0.576, P < 0.01), and patients with mutant alleles had a relative risk (RR) of 12.0 (CI95% 1.7-92.3) of developing leukopenia. A 6-MMPR/6-TGN ratio less than 11 was associated with therapeutic efficacy. Based on this pharmacokinetic analysis, therapeutic drug monitoring is essential for rational 6-MP dosing.