The value of dihydrouracil/uracil plasma ratios in predicting 5-fluorouracil-related toxicity in colorectal cancer patients.

This study investigated the relationship between the dihydrouracil/uracil (UH(2)/U) plasma ratio, a surrogate marker of dihydropyrimidine dehydrogenase (DPD) activity, and 5-fluorouracil (5-FU)-related early toxicity. Plasma UH(2)/U ratios were determined in 68 colorectal cancer patients and 100 healthy controls. A cut-off value indicative of DPD deficiency was calculated using receiver operator characteristics. Patients experiencing toxicity were screened for the DPD G-to-A point mutation within the 5'-splicing donor site of intron 14 (IVS14+1G>A). Overall, 24/68 patients (35%) experienced toxicity (all grades) and abnormal UH(2)/U ratios were demonstrated in 21/24 (87.5%) patients. Drug concentrations up to 130 times the recommended level were found in 13/24 (54%) patients experiencing toxicity. One patient experiencing toxicity was a heterozygous carrier of the IVS14+1G>A mutation. A low UH(2)/U plasma ratio had a sensitivity of 0.87 and specificity of 0.93 for predicting 5-FU-induced toxicity. Systematic detection of DPD-deficient patients using the UH(2)/U ratio could optimize 5-FU-based chemotherapy and minimize life-threatening toxicity.

Variants in the dihydropyrimidine dehydrogenase, methylenetetrahydrofolate reductase and thymidylate synthase genes predict early toxicity of 5-fluorouracil in colorectal cancer patients.

Adverse drug reactions to 5-fluorouracil (5-FU)-based chemotherapy have been reported to be due, in part, to genetic variants of the genes for the drug-related enzymes thymidylate synthase (TS; TYMS gene), methylenetetrahydrofolate reductase (MTHFR gene) and dihydropyrimidine dehydrogenase (DPD; DPYD gene). This study investigated whether selected genetic variants of the TYMS, MTHFR and DPYD genes predict 5-FU-related early toxicity. The prevalence of the genetic variants was determined in 122 colorectal cancer patients and in a reference population of 320 blood donors. Subgroup analysis of 68 of the colorectal cancer patients was carried out to determine the relationship between selected gene variants detected in peripheral mono nuclear cells and tolerability during the first or second cycle of 5-FU based treatment. Toxicity was linked to the TYMS 2R/2R variant (relative risk [RR] 1.66; sensitivity 0.37; specificity 0.77) and to the MTHFR c1298 C/C genetic variant (RR 1.77; sensitivity 0.17; specificity 0.91). Patients with the genetic variant IVS14+1 G/A or c1896 C/T in the DPYD gene had a statistically significant increased risk of experiencing toxicity (RR 2 and 6, respectively), both having a high specificity (0.97 and 0.98, respectively) and low sensitivity (0.04 and 0.13, respectively). It is concluded that pre-treatment detection of genetic variants can help to predict early toxicity experienced by patients receiving 5-FU-based chemotherapy.

Correlation between thymidylate synthase gene variants, RNA and protein levels in primary colorectal adenocarcinomas.

This study was designed to compare thymidylate synthase (TS) genotype, mRNA and protein levels in primary colorectal adenocarcinoma, and to examine the correlation between microsatellite instability (MSI) and TS expression. The TS genotype of 68 patients with colorectal cancer was determined by polymerase chain reaction (PCR) and restriction fragment length polymorphism analysis in peripheral blood mononuclear cells and tumour tissue. The TS mRNA levels in tumour tissue were measured by reverse-transcription PCR, and TS protein levels and MSI status were assessed using immunohistochemistry. Significantly higher mRNA and protein levels were observed in patients with the TS 3R/3R versus the 2R/2R and 2R/3R genotypes. There was no correlation between TS single nucleotide polymorphism and TS expression. Individuals homozygous for the six base-pair insertion in the 3'-untranslated region had significantly higher TS mRNA levels than heterozygous and homozygous wild type individuals. The TS mRNA and protein levels were significantly higher in microsatellite unstable tumours compared with microsatellite stable tumours. There was a significant association between the number of TS enhancer region repeats (in blood) and intratumoural TS mRNA and protein levels. A larger case series investigating the role of TS gene polymorphisms as predictors of sensitivity to 5-fluorouracil-based chemotherapy is required.

A randomized study comparing short-time infusion of oxaliplatin in combination with capecitabine XELOX(30) and chronomodulated XELOX(30) as first-line therapy in patients with advanced colorectal cancer.

BACKGROUND: Chronotherapy is one of the several approaches to increase efficacy and reduce toxicity of chemotherapy. In a phase II study in the second-line in patients with metastatic colorectal cancer (mCRC), we found that chronomodulated XELOX (XELOX(30Chron)) was a well-tolerated regimen with potentially reduced toxicity. PATIENTS AND METHODS: One hundred and forty-one patients with unresectable mCRC were enrolled in a randomized study comparing standard XELOX (XELOX(30)), arm A, and XELOX(30Chron), arm B-both with short-time infusion of oxaliplatin-with the primary aim of reducing overall toxicity. RESULTS: Overall toxicity grade 2-4 was 90% versus 85%, P = 0.47 and grade 3-4 was 31% versus 37%, P = 0.6 in arm A and B, respectively. We found no significant differences in median overall survival (17.6 versus 15.5 months; P = 0.068) and median progression-free survival (8.9 versus 8.8 months; P = 0.7). The incidence of grade 3 neuropathy was 16% in arm A and 19% in arm B (P = 0.7) after a cumulative dose of oxaliplatin of 1000 mg/m(2). CONCLUSION: XELOX(30Chron) does not reduce toxicity or improve efficacy. A 30-min infusion of oxaliplatin is safe and does not increase the severity of chronic neuropathy.

Increased ratio between deoxycytidine kinase and thymidine kinase 2 in CLL lymphocytes compared to normal lymphocytes.

Deoxycytidine kinase (dCK) is important in the 5'-phosphorylation of deoxynucleoside analogs. Like dCK, thymidine kinase 2 (TK2) catalyzes the initial step of the phosphorylation of dcyd to dCTP. Thymidine is a strong inhibitor of the dCK activity of TK2. We examined the ratio of the dcyd phosphorylation carried out by dCK and by TK2 (dCK/TK2-dcyd) in lymphocytes from CLL patients and from donors. In the CLL lymphocytes we found a 3.5-fold average increase. Therefore, we conclude that addition of thymidine in the treatment of CLL with deoxynucleoside analogs will not be of any advantage. Furthermore, our results can explain earlier findings in CML and AML lymphocytes where the ara-C phosphorylation was twice the dcyd phosphorylation.

Features of the initial metabolism of 1-beta-D-arabinofuranosylcytosine in human myeloid leukemic cells.

With the aim of improving the treatment of AML patients the activities of selected nucleoside metabolizing enzymes of possible implication for the initial metabolism of Ara-C have been studied in leukemic and normal cells. An increased ADA activity, a slightly changed PNP activity, a decreased CDD activity and an increased dCK activity, including deviation in substrate specificity, were found in myeloid leukemic cells. The increase of ADA may in part be related to immaturity of the cells. This is supported by the finding of a decrease in the ADA activity during experimental induced differentiation of myeloid cells. On the other hand differentiation is not dependent on the ADA decrease, since differentiation can occur without the decrease of ADA. The correlation between myeloid blast counts in peripheral blood from AML patients and the ADA activity also supports the connection between the development stage of the cells and the ADA activity. Minor changes of the ADA activity in myeloid cells from patients with liver cirrhosis have been observed without changes in the maturity of the cells indicating that other factors than the differentiation of the cells are of importance for the activity of ADA in myeloid cells. Only minor changes have been observed in the activity of PNP related to myeloid leukemic cells. CDD activity is decreased in myeloid leukemic cells. Differentiation is probably of major importance for the activity, experimentally supported by the increase observed concurrently with induced differentiation of myeloid cells. An inverse correlation between the CDD activity and the blast counts in patients with AML is also supportive.(ABSTRACT TRUNCATED AT 250 WORDS)

Modulation of the effect of 1-beta-D-arabinofuranosylcytosine based on changes of cytidine deaminase activity in HL60 cells.

The effect of changes in cytidine deaminase activity on the growth inhibitory effect of 1-beta-D-arabinofuranosylcytosine (Ara-C) has been investigated in the human promyelocytic cell line, HL60. 1,25 Dihydroxy vitamin D3 (vit. D3), which is an inducer of differentiation, caused an increase of cytidine deaminase in HL60 cells simultaneous with an inhibition of the effect of Ara-C. On the other hand, retinoic acid, which also induces differentiation had no influence on either the activity of cytidine deaminase or the effect of Ara-C. An atoxic inhibitor of cytidine deaminase tetrahydrouridine, THU, enhanced the effect of Ara-C. THU also enhanced the effect of Ara-C, even if the Ara-C effect was inhibited by deoxycytidine. These results show that it is possible to modulate the effect of Ara-C by changing the activity of cytidine deaminase. Furthermore, changes in the activity of cytidine deaminase and the effect on the Ara-C growth inhibition vary dependent on the differentiating inducer used.

Changes in the activities of cytidine deaminase during differentiation of HL60 cells induced by 1,25 dihydroxy D3.

The activities of the enzymes cytidine deaminase (CDD), deoxycytidine kinase (dCK), adenosine deaminase (ADA), and purine nucleoside phosphorylase (PNP), have been investigated in the promyelocytic leukemia cell line HL60. The activities of the enzymes corresponded well with that seen in acute myeloid leukemia cells except, that the CDD activity was very low in the HL60 cells. Induction of differentiation in HL60 cells by 1,25 dihydroxy D3 resulted in an increase in CDD from 12 to 247 nmol/h/mg and a decrease in ADA from 1326 to 896 nmol/h/mg, while the activities of dCK, and PNP were unchanged. Retinoic acid, another used inducer of differentiation, gave no changes of the enzyme activities. The increase in CDD activity induced by 1,25 dihydroxy D3 was prevented by inhibition of protein synthesis, whereas inhibition of proliferation of the cells did not abolish the increase of CDD. The changes correspond well with the differences seen between immature and mature myeloid cells. The results may have consequences for the interpretation of results obtained with cytostatics, which are metabolized by the enzymes.

Purine metabolizing enzymes in lymphocytes from patients with solid tumors.

The activities of five clinically important enzymes of purine metabolism have been determined in lymphocytes from 62 patients with various types of solid tumors. The activity of purine nucleoside phosphorylase was increased in all patient groups studied, i.e. small cell bronchogenic carcinoma (n = 30), carcinoma of the breast (n = 17) and other tumors (n = 15), compared to cells form normal donors. Activities of adenosine deaminase, adenine phosphoribosyltransferase (APRT), hypoxanthine (guanine) phosphoribosyltransferase (HGPRT), and 5'-nucleotidase (5'-NUC) vary little from control values, except for lower levels of APRT in lymphocytes from patients with carcinoma of the breast. In patients with small cell bronchogenic carcinoma, enzyme levels were also determined in granulocytes, where increased APRT activity was found. Following cytostatic treatment of these patients, significant decreases were seen in lymphocytic HGPRT and 5'-NUC activities.

Changes in some nucleoside metabolizing enzymes of lymphocytes and granulocytes from patients with cirrhosis of the liver.

Some purine metabolizing enzymes of lymphocytes and granulocytes were determined in 13 patients with cirrhosis of the liver and in a control group consisting of 18 healthy blood donors. Furthermore cytidine deaminase (EC 3, 5, 4, 5) (CRD) activity was determined in the granulocytes of these patients and in 16 controls. An increase of adenosine deaminase (EC 3, 5, 4, 4) (ADA) activity was found in granulocytes (P less than 0.01) as well as in lymphocytes (P less than 0.01) of the cirrhotic patients as compared to controls. Purine nucleoside phosphorylase (EC 2, 4, 2, 1) (PNP) activity in granulocytes and lymphocytes was identical in the two groups. In lymphocytes of cirrhotic patients decreased hypoxanthine guanine phosphoribosyltransferase (EC 2, 4, 2, 8) (HGPRT) (P less than 0.01), adenine phosphoribosyltransferase (EC 2, 4, 2, 7) (APRT) (P less than 0.02) and adenosine kinase activities (EC 2, 7, 1, 20) (AK) (P less than 0.05) were demonstrated. 5'-nucleotidase (5'-N (EC 3, 1, 3, 5) activity in lymphocytes of cirrhotic patients was slightly increased, the increase being correlated to the level of serum gamma globulin. Granulocytes from cirrhotic patients showed a decrease of CRD (P less than 0.05). The finding that ADA activity is increased in mature lymphocytes and granulocytes from cirrhotic patients argues against the possibility that increase of lymphocytes ADA activity is a consequence of malignant transformation or immaturity.

Enzymatic studies on possible improvement of cytosine arabinoside treatment.

Initial phosphorylation and deamination of cytosine arabinoside (Ara-C) and the natural metabolite deoxycytidine (CdR) were estimated in cell free extracts of leucocytes from patients with CML and controls. Phosphorylation of CdR had been increased while deamination of CdR in extracts of CML cells from peripheral blood had been decreased compared with normal leucocytes. Comparing the ratios between Ara-C and CdR phosphorylation it was revealed that these were twice as high in CML cells as in normal leucocytes, whereas no difference was found when comparing ratios between Ara-C and CdR deamination. From these discoveries it is proposed that Ara-C can be combined with CdR with advantage, because apparently CdR protects the normal cells more than the malignant ones.