Double-balloon enteroscopy in Ireland in the capsule endoscopy era

BACKGROUND

The availability of double-balloon enteroscopy (DBE) and small bowel capsule endoscopy (SBCE) in Ireland has revolutionised our approach to the diagnosis and treatment of small bowel disorders.

AIMS

To evaluate the use of DBE in Ireland and to compare the diagnostic yield with and without prior SBCE in order to improve the efficiency of our resources for small bowel endoscopy.

METHODS

A retrospective comparison study of all DBEs performed between two centres, one with SBCE available, was undertaken. Information was obtained by review of endoscopy reports, referral letters, radiology reports and charts. A review of the SBCE database was undertaken to identify patients who had undergone SBCE prior to DBE.

RESULTS

A total of 242 DBE procedures were carried out between both centres. SBCE was performed prior to DBE in 20 % (n = 46). The overall diagnostic yield of DBE was 47 % (n = 115). There was a statistically significant difference in diagnostic yield between the DBE only and the DBE with prior SBCE groups 44 versus 61 %, respectively, p < 0.0001. There was also a significant difference in the DBE approach, with 73 % of procedures being anterograde in centre 1 versus 56 % in centre 2. A subgroup analysis of centre 1 data revealed a negative predictive value of 100 % and a positive predictive value of 74 % for SBCE when DBE findings were considered as a gold standard.

CONCLUSION

SBCE as a screening tool prior to DBE is extremely valuable and increases the diagnostic yield considerably as a consequence of a high negative predictive value.

Cyclopentenyl cytosine increases gemcitabine radiosensitisation in human pancreatic cancer cells

The deoxycytidine analogue 2′,2′-difluoro-2′-deoxycytidine (dFdC, gemcitabine) is a potent radiosensitiser, but has limited efficacy in combination with radiotherapy in patients with pancreatic cancer due to acute toxicity. We investigated whether cyclopentenyl cytosine (CPEC), targetting the ‘de novo’ biosynthesis of cytidine triphosphate (CTP), could increase dFdC cytotoxicity alone or in combination with irradiation in a panel of human pancreatic cancer cells (Panc-1, Miapaca-2, BxPC-3). To investigate the role of deoxycytidine kinase (dCK), the rate-limiting enzyme in the activation of dFdC, human lung cancer cells without (dFdC-resistant SWg) and with an intact dCK gene (dFdC-sensitive SWp) were included. We found that CPEC (100–1000 nmol l⁻¹) specifically reduced CTP levels in a dose-dependent manner that lasted up to 72 h in all cell lines. Preincubation with CPEC resulted in a dose-dependent increase in dFdC incorporated into the DNA only in dFdC-sensitive cells. Consequently, CPEC increased the effectiveness of dFdC (300 nmol l⁻¹ for 4 h) only in dFdC-sensitive cells, which was accompanied by an increase in apoptosis. We also found that CPEC enhanced the radiosensitivity of cells treated with dFdC (30–300 nmol l⁻¹ for 4 h). These results indicate that CPEC enhances the cytotoxicity of dFdC alone and in combination with irradiation in several human tumour cell lines with an intact dCK gene.

Increased cytotoxicity of 2',2'-difluoro-2'-deoxycytidine in human leukemic cell-lines after a preincubation with cyclopentenyl cytosine

The in vitro modulating effect of Cyclopentenyl cytosine (CPEC) on the metabolism of gemcitabine was studied in lymphocytic and myeloid leukemic cell-lines. In MOLT-3 cells, that were pretreated with CPEC, the incorporation of 2',2'-difluoro-2'-deoxycytidine triphosphate (dFdCTP) into DNA was significantly increased by 57-99% in comparison with cells that were only treated with gemcitabine. The increased incorporation of dFdCTP into DNA in CPEC pretreated cells was paralleled by an increase in apoptotic and necrotic cells of 17-34%. In HL-60 cells that were preincubated with CPEC, increased concentrations of the mono-/di- and triphosphate form of gemcitabine were observed, as well as an increased incorporation of dFdCTP into DNA (+773%). This increased incorporation was paralleled by a significant increase in apoptosis and necrosis. We conclude that CPEC enhances the incorporation of dFdCTP into DNA and thus increases the cytotoxicity of gemcitabine in lymphocytic and myeloid leukemic cell-lines.

Cyclopentenyl cytosine induces apoptosis and increases cytarabine-induced apoptosis in a T-lymphoblastic leukemic cell-line

Cyclopentenyl cytosine (CPEC) is a nucleoside-analogue that decreases the concentrations of cytidine triphosphate (CTP) and deoxycytidine triphosphate (dCTP) in leukemic cells by inhibiting the enzyme CTP synthetase, resulting in a decreased synthesis of RNA and DNA. Low concentrations of dCTP facilitate the phosphorylation of 1-beta-D arabinofuranosyl cytosine (araC) and the incorporation of arabinofuranosyl cytosine triphosphate (araCTP) into DNA. Apoptosis and necrosis were analyzed by flow cytometric detection of fluorescence-labeled Annexin V in a human T-lymphoblastic MOLT-3 cell-line after incubations with CPEC and/or araC. CPEC induced apoptosis and necrosis in a concentration- (50-300 nM) and time-dependent (8-16 h) way. The observed necrosis proved to be secondary to apoptosis as the caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (zVAD-fmk) completely blocked the CPEC-induced apoptosis and necrosis. Coincubation of various concentrations of CPEC and araC for 16h showed a significant additive effect on the occurrence of apoptosis and (secondary) necrosis. In contrast, a preincubation with 37.5 nM of CPEC for 24 h, which by itself caused only minor apoptosis (4%), followed by a coincubation for 16 h with 62.5 nM of araC (7% of apoptotic cells), showed a synergistic effect on the induction of apoptosis (27%, P<0.001). Growth-inhibition experiments with CPEC and araC under various conditions showed an additive effect on the araC-induced growth-inhibition after 48 h. The results indicate that the cytotoxicity of araC can be increased in T-lymphoblasts by CPEC.

In vitro inhibition of cytidine triphosphate synthetase activity by cyclopentenyl cytosine in paediatric acute lymphocytic leukaemia

Cytidine triphosphate (CTP) synthetase is a key enzyme for the synthesis of cytosine (deoxy)ribonucleotides, catalysing the conversion of uridine triphosphate (UTP) into CTP, and has a high activity in several malignancies. In this preclinical study, the enzyme activity and mRNA expression of the enzyme and (deoxy)ribonucleotide concentrations were analysed in leukaemic cells of 57 children suffering from acute lymphocytic leukaemia (ALL). In addition, in vitro experiments were performed with the CTP synthetase inhibitor cyclopentenyl cytosine (CPEC). A significantly higher activity of CTP synthetase (6.5 +/- 3.9 nmol CTP/mg/h) was detected in ALL cells than in lymphocytes of healthy controls (1.8 +/- 0.9 nmol CTP/mg/h, P < 0.001) that was independent of white blood cell (WBC) count, blast percentage, age, gender or type of ALL. The enzyme activity was not correlated with the CTP synthetase mRNA expression. The activity of CTP synthetase in ALL cells compared with non-malignant CD34+ bone marrow controls (5.6 +/- 2.4 nmol CTP/mg/h) was not statistically different. In vitro treatment of ALL cells with CPEC induced a dose-dependent decrease of the CTP concentration. The lowest concentration of CPEC (0.63 microM) induced a depletion of CTP of 41 +/- 20% and a depletion of dCTP of 27 +/- 21%. The degree of CTP depletion of ALL cells after treatment with CPEC was positively correlated with the activity of CTP synthetase. The inhibition of CTP synthetase in situ was confirmed by flux studies using radiolabelled uridine. From these results, it can be expected that CPEC has a cytostatic effect on lymphoblasts of children with ALL.

Cyclopentenyl cytosine inhibits cytidine triphosphate synthetase in paediatric acute non-lymphocytic leukaemia: a promising target for chemotherapy

Cytidine triphosphate (CTP) synthetase is a key enzyme in the anabolic pathways of cytosine and uracil ribonucleotide metabolism. The enzyme catalyses the conversion of uridine triphosphate (UTP) into CTP, and has a high activity in various malignancies, which has led to the development of inhibitors of CTP synthetase for therapeutic purposes. We studied both CTP synthetase activity and ribonucleotide concentrations in leukaemic cells of 12 children suffering from acute non-lymphocytic leukaemia (ANLL), and performed incubation experiments with cyclopentenyl cytosine (CPEC), a nucleoside analogue that is capable of inhibiting CTP synthetase. The CTP synthetase activity in ANLL cells (5.1+/-2.3 nmol CTP/mg/h) was significantly higher compared with granulocytes of healthy controls (0.6+/-0.4 nmol CTP/mg/h, P=0.0002), but was not different from the CTP synthetase activity in non-malignant CD34+ bone marrow cells (5. 6+/-2.4 nmol CTP/mg/h). Major shifts were observed in the various ribonucleotide concentrations in ANLL cells compared with granulocytes: the absolute amount of ribonucleotides was increased with a substantial rise of the CTP (2.4 versus 0.4 pmol/microg protein, P=0.0007) and UTP (8.7 versus 1.6 pmol/microg protein, P=0. 0007) concentrations in ANLL cells compared with granulocytes. Treatment of ANLL cells in vitro with CPEC induced a major depletion (77% with 2.5 microM of CPEC) in the concentration of CTP, whilst the concentrations of the other ribonucleotides remained unchanged. Therefore, the high activity of CTP synthetase in acute non-lymphocytic leukaemic cells can be inhibited by CPEC, which provides a key to a new approach for the treatment of ANLL.