XRCC3 5′-UTR and IVS5-14 polymorphisms and breast cancer susceptibility: a meta-analysis

Published data on the association between XRCC3 5′-UTR and IVS5-14 polymorphisms and breast cancer risk are inconclusive. In order to derive a more precise estimation of the relationship, a meta-analysis was performed. Crude ORs with 95% CIs were used to assess the strength of association between these polymorphisms and breast cancer risk. The pooled ORs were performed for codominant model, dominant model, and recessive model, respectively. A total of four studies were involved in the meta-analysis with 6,303 cases and 6,563 controls for XRCC3 5′-UTR polymorphism and with 6,270 cases and 6,682 controls for XRCC3 IVS5-14 polymorphism. For XRCC3 5′-UTR A/G polymorphism, significantly elevated breast cancer risk was associated with variant genotype when all studies were pooled into the meta-analysis (AG vs. AA: OR = 1.11, 95% CI = 1.03–1.19; dominant model: OR = 1.09, 95% CI = 1.01–1.17). For XRCC3 IVS5-14 A/G polymorphism, significantly decreased breast cancer risk was associated with variant genotype (GG vs. AA: OR = 0.86, 95% CI = 0.77–0.96). In conclusion, this meta-analysis suggests that the variant G allele of XRCC3 5′-UTR polymorphism is a low-penetrant risk factor for developing breast cancer, while the variant G allele of XRCC3 IVS5-14 polymorphism has a protective effect on breast cancer development.     

Activities of adenosine deaminase and 5′-nucleotidase in cancerous and noncancerous human colorectal tissues

In order to characterize human colorectal cancer, much attention has been paid to enzyme studies. However, little is known about the correlation between the levels of key enzymes of purine nucleotide pathway and some clinical and biological indicators of tumor invasiveness and aggressiveness. Adenosine deaminase (ADA) and 5′-nucleotidase (5′-NT) were measured in cancerous and cancer-free adjacent large bowel tissues from 38 patients with colorectal carcinoma. We have analyzed the relationship between the enzyme levels and some clinical and pathological parameters. The enzymes' activities were markedly higher in primary tumors than in corresponding normal mucosae. The ADA level in tumor tissue was significantly correlated with lymph node metastasis, histologic type, tumor location, and patient's age, whereas the 5′-NT level showed a significant correlation with tumor grade and tumor location. ADA activity in tumor tissues was significantly higher in patients whose clinical course remained stable than in those with recurrent diseases. The purine metabolism and salvage pathway activity of purine nucleotides are accelerated in the cancerous human colorectal tissue. Although our findings suggest that these enzymes' activities are most likely retated to the same histomorphological architecture of the tumor, the authors believe that long-term follow-up studies are needed to evaluate the prognostic value of purine enzymes for colorectal cancer.     

Cell cycle effects and cellular pharmacology of 5-AZA-2′-deoxycytidine

Summary The cytotoxic action of 5-aza-2-deoxycytidine (5-AZA-CdR) in synchronized cells and logarithmic- and plateau-phase cultures of EMT₆ murine tumor cells was investigated. 5-AZA-CdR produced a greater cell kill of S phase cells than of cells in G₁ phase. Cells in the logarithmic phase of growth were more sensitive to the cytotoxic effects of 5-AZA-CdR than cells in the plateau phase of growth. These results indicate that 5-AZA-CdR produces a preferential kill of cells in the S phase of the cell cycle. 5-AZA-CdR did not block the cell cycle progression of cells into S phase. The survival curve of EMT₆ cells exposed to 5-AZA-CdR suggests that the cytotoxic action of this analogue is not self-limiting. The mutagenic activity of 5-AZA-CdR was investigated using induction of 6-thioguanine resistance in Chinese hamster ovary cells. 5-AZA-CdR was not a detectable mutagen in this assay system.     

Phase I and pharmacologic evaluation of intraperitoneal 5-fluoro-2′-deoxyuridine

Summary Intraperitoneal (i.p.) 5-fluoro-2-deoxyuridine (Floxuridine, FUdR, FdUrd) was evaluated in a phase I study at a starting level of 500 mg given on 1 day in 2 I 1.5% dialysate. Escalations within patients were allowed every other cycle. A total of 23 patients (age, 32–78 years) received 108 treatment courses. Local tolerance at all dose levels was excellent, with no cases of drug-related peritonitis being observed. Nausea and vomiting increased in severity in relation to dose and was universal at >3,000 mg ×3 days. One patient each developed grade 1 mucositis as well as diarrhea at a dose of 3,000 mg×3 days and leukopenia and thrombocytopenia at 5,000 mg×3 days. Peritoneal fluid (PF) and plasma (PL) FdUrd profiles were monitored by an HPLC method in 13 subjects, with 7 being studied serially at 2–4 increment doses for up to 6 h. Profiles that exhibited apparent linear pharmacokinetics gave PF drug levels 2–4 logs higher than the PL counterparts, with the latter essentially declining in parallel to the former, indicating that the disposition of FdUrd from the peritoneal compartment is rate-determining. The mean terminal half-life for PF FdUrd was found to be 115 min and mean peritoneal clearance was 25 ml/min. The vast differences in drug levels and AUC found between the PF and the PL profiles suggests a high systemic clearance of FdUrd, which was confirmed in two patients receiving 2 g FdUrd by short i.v. infusion. A disproportionate increase in the plasma FdUrd levels and the corresponding AUC values was found with increasing dose, suggesting a disproportionate increase in the systemic partitioning of FdUrd when doses were escalated within a patient. Substantial levels of peritoneal 5-fluorouracil (FUra) were also detected in most of the subjects. Thus, FdUrd was found to have several desirable properties for i.p. administration: (1) a 2- to 4-log pharmacologic advantage, (2) the absence of local toxicities, and (3) a favorable antitumor spectrum and some evidence of antitumor effects in this phase I and pharmacology study. A 3,000-mg dose given in 2 l 1.5% dialysate for 3 consecutive days exhibited antitumor activity and produced no systemic toxicity except nausea and vomiting, which was controlled by antiemetics. This dose schedule is therefore recommended for phase II trials directed against small-volume disease in the peritoneal cavity, such as may be found in some stages of ovarian and gastrointestinal cancers. In addition, it is suitable for further exploration as a part of regimens including systemic therapy or drugs that modulate the action of fluoropyrimidines.Supported in part by Cancer Center Core Grant CA 14089, by ROI CA 50 412, by an ACS Institutional Grant (IN21Z, to C. R.) and by the Italian-American Foundation award (to N. C.)Deceased     

Novel DNA methyltransferase-1 (DNMT1) depleting anticancer nucleosides, 4′-thio-2′-deoxycytidine and 5-aza-4′-thio-2′-deoxycytidine

Purpose

Currently approved DNA hypomethylating nucleosides elicit their effects in part by depleting DNA methyltransferase I (DNMT1). However, their low response rates and adverse effects continue to drive the discovery of newer DNMT1 depleting agents. Herein, we identified two novel 2′-deoxycytidine (dCyd) analogs, 4′-thio-2′-deoxycytidine (T-dCyd) and 5-aza-4′-thio-2′-deoxycytidine (aza-T-dCyd) that potently deplete DNMT1 in both in vitro and in vivo models of cancer and concomitantly inhibit tumor growth.

Methods

DNMT1 protein levels in in vitro and in vivo cancer models were determined by Western blotting and antitumor efficacy was evaluated using xenografts. Effects on CpG methylation were evaluated using methylation-specific PCR. T-dCyd metabolism was evaluated using radiolabeled substrate.

Results

T-dCyd markedly depleted DNMT1 in CCRF-CEM and KG1a leukemia and NCI-H23 lung carcinoma cell lines, while it was ineffective in the HCT-116 colon or IGROV-1 ovarian tumor lines. On the other hand, aza-T-dCyd potently depleted DNMT1 in all of these lines indicating that dCyd analogs with minor structural dissimilarities induce different DNMT1 turnover mechanisms. Although T-dCyd was deaminated to 4′-thio-2′-deoxyuridine, very little was converted to 4′-thio-thymidine nucleotides, suggesting that inhibition of thymidylate synthase would be minimal with 4′-thio dCyd analogs. Both T-dCyd and aza-T-dCyd also depleted DNMT1 in human tumor xenografts and markedly reduced in vivo tumor growth. Interestingly, the selectivity index of aza-T-dCyd was at least tenfold greater than that of decitabine.

Conclusions

Collectively, these data show that 4′-thio modified dCyd analogs, such as T-dCyd or aza-T-dCyd, could be a new source of clinically effective DNMT1 depleting anticancer compounds with less toxicity.     

5′-deoxy-5-fluorouridine, medroxyprogestrone acetate and mitoxantrone hydrochloride for advanced or recurrent Breast Cancer

BACKGROUND: In treating advanced or recurrent breast cancer, anthracycline-containing chemotherapy is used for palliation and to maintain quality of life. However, there are several drawbacks including therapeutic failure and cardiotoxicity. We evaluated the efficacy and toxicity of combination chemotherapy with 5'-deoxy-5-fluorouridine (5'-DFUR), medroxyprogestrone acetate (MPA) and mitoxantrone hydrochloride (MIT). METHODS: Sixteen patients with advanced or recurrent breast cancer were enrolled. Chemotherapy was given in a 28-day cycle, starting with MIT 10 mg/m2 intravenously on day 1, then oral 5'-DFUR 800 mg and MPA 800 mg daily. Two or more cycles were given. RESULTS: Fifteen patients were assessable for response and toxicity. Thirteen patients had been treated previously with an anthracycline containing regimen and 2 with CMF. There were 2 partial response patients (13.3%) and 1 complete response patient (6.7%). There were 11 patients showing no change (NC) (73.3%), one of whom was a minor responder and 7 with a long period of NC. There was only one with progressive disease patient. The overall response rate was 20.0%. Adverse events occurred in 5 patients (33.3%). Myelosuppression was the most common with 5 patients becoming leukopenic (33.3%). Nausea/vomiting was the second most common side effect, affecting 2 patients (13.3%). CONCLUSION: Given its high efficacy and preservation of QOL, the combination of MIT, 5'-DFUR and MPA can be a 2nd or 3rd line therapy for advanced or recurrent breast cancer, especially for anthracycline-resistant cases.     

Concurrent allopurinol and 5-fluorouracil: 5-fluoro-2′-deoxyuridylate formation and thymidylate synthase inhibition in rat colon carcinoma and in regenerating rat liver

Summary The formation of FdUMP and the inhibition of TS were studied in a subcutaneously growing transplantable rat colon carcinoma and in regenerating rat liver following bolus administration of 5-FU, with or without HPP pretreatment.In tumor, peak levels of FdUMP at 30 min following bolus 5-FU, 100 mg/kg, averaged 4931±587 pmol/g. Pretreatment with HPP, 50 mg/kg, 24 h and 1 h before 5-FU, reduced the peak FdUMP level to 2085±387 pmol/g. The inhibition of TS by 5-FU treatment was greater than 95% by 30 min, and after 48 h residual enzyme inhibition averaged 40%. No effect on TS inhibition by 5-FU treatment could be observed as a result of HPP pretreatment. The levels of TS_tot increased linearly after 5-FU treatment and doubled within 48 h.In regenerating rat liver, neither FdUMP levels nor TS inhibition, studied at 1 h after bolus 5-FU, were affected by HPP pretreatment.Abbreviations BSA bovine serum albumin - DMH dimethylhydrazine - 5-FU 5-fluorouracil - HPP allopurinol (4-hydroxypyrazolopyrimidine) - CH₂FH₄ 5, 10-methylenepteroylmonoglutamic acid - FUMP 5-fluorouridine-5-monophosphate - FUTP 5-fluorouridine-5-triphosphate - FdUMP 5-fluoro-2-deoxyuridylate - TS thymidylate synthase (EC 2.1.1.45, dTMP synthase) - TS_f free, non-FdUMP-bound TS - TS_b ternary complex-bound TS - TS_tot total TS TS_f+TS_b - PRPP phosphoribosylpyrophosphate This study was supported by grants from the Swedish Cancer Society, The Medical Society of Göteborg, the University of Göteborg, the Wellcome Foundation, and NCI Grant 39629.     

The efficacy of long-term oral chemotherapy with 5′-deoxy-5-fluorouridine and cyclophosphamide for recurrent breast cancer

Background 5-Deoxy-5-fluorouridine (5-DFUR) is a prodrug of 5-fluorouracil (5-FU), which is known to be converted by thymidine phosphorylase (dThdPase). A recent preclinical study revealed that cyclophosphamide (CPA) upregulated dThdPase activity, specifically in tumor cells. The purpose of the present study was to examine the efficacy of long-term administration of 5-DFUR/CPA for patients with recurrent breast cancer.Methods Fifteen breast cancer patients with recurrent tumors entered this study. Ten patients had bone metastasis, five had lung metastasis, and two had liver metastasis. Three patients had multiorgan metastases. All patients had had previous exposure to standard chemotherapy such as CAF (CPA, doxorubicin, and 5-FU) and CMF (CPA, methotrexate, and 5-FU). The patients were orally administered with daily doses of 5-DFUR at 800–1200mg and CPA at 200mg for 2 weeks as induction therapy, followed by 2 weeks rest (one to two cycles). Daily doses of 800mg of 5-DFUR and 100mg of CPA (as maintenance therapy) were continuously administered thereafter. Ten of the 15 patients received the maintenance therapy alone. The treatment was continued for at least 24 months (average, 35.2 months).Results The main findings included a significant decrease in pain in nine patients with bone metastasis, and this effect continued for more than 2 years. As the pain decreased, the patients quality of life (QOL) was improved. Liver metastasis was diminished in two out of two patients. Hematological toxicity of more than grade 3 was recognized in three patients, but only during the induction therapy.Conclusion Oral administration of 5-DFUR/CPA is well tolerated and useful for patients with recurrent breast cancer.     

Potentiation of the chemotherapeutic action of 5′-deoxy-5-fluorouridine in combination with guanosine and related compounds

Summary The effect of inosine, guanosine, and guanosine 5-monophosphate (GMP) on the antitumor activity of 5-deoxy-5-fluorouridine (5-DFUR) was investigated using P388 leukemia and P815 mastocytoma.The antitumor activity of 5-DFUR was markedly enhanced by coadministration of inosine or guanosine. The increase in lifespan (ILS) of mice treated with 5-DFUR was augmented by the combination with guanosine or inosine in a dose-dependent fashion, and the maximum ILS was about 160% with the combination, while that in the case of 5-DFUR alone was only 48% in the P388 leukemia system. The therapeutic ratio (dose at ILS_max/dose at ILS₃₀) of the combination with guanosine or inosine was 333 and 136, respectively, whereas that of 5-DFUR alone was 3.6. GMP also markedly potentiated the antitumor activity of 5-DFUR in both P388 leukemia and P815 mastocytoma systems, just as it potentiated the activity of 5-fluorouracil in the latter system.The uric acid level in the serum was elevated after IP injection of guanosine or inosine but the value was much lower in the case of guanosine than in inosine.     

Cytokines induce thymidine phosphorylase expression in tumor cells and make them more susceptible to 5′-deoxy-5-fluorouridine

The present study shows that various cytokines such as tumor necrosis factor (TNF), interleukin-1 (IL-1), and interferon- (IFN) make tumor cells much more susceptible to the cytostatic 5-deoxy-5-fluorouridine (5-dFUrd) than to 5-fluorouracil (5-FUra) and other cytostaties. These three cytokines increased the susceptibility of human cancer cell lines (COLO201, MKN45 and WiDr) but did not affect that of normal fibroblast WI38 cells. The cytokine mixture induced a 50-fold increase in the susceptibility of COLO201 to 5-dFUrd, whereas a 12-fold increase and a less than 5-fold enhancement in the susceptibility to 5-FUra and other cytostatics, respectively, were observed. The increased susceptibility would be a result of the induction of thymidine phosphorylase (TdR Pase), which is the essential enzyme for the conversion of 5-dFUrd to 5-FUra. The cytokine mixture increased TdR Pase activity by up to 47 times and greatly induced its mRNA expression in the cancer cell lines. These results suggest that the therapeutic benefit of 5-dFUrd would be improved by its use in combination with the cytokines.     

Chemotherapy of L1210 and L1210/ARA-C leukemia with 5-aza-2′-deoxycytidine and 3-deazauridine

Summary The in vitro and in vivo antineoplastic activity of 5-aza-2-deoxycytidine (5-AZA-dCyd) and 3-deazauridine (3-DU) against L1210 and L1210/ARA-C (resistant to cytosine arabinoside) leukemic cells were investigated. L1210/ARA-C cells were more sensitive to the inhibitory effects of 3-DU than L1210 cells. Deoxycytidine completely reversed the in vitro cytotoxic effects produced by 3-DU on L1210 cells, but not those produced in L1210/ARA-C cells. L1210/ARA-C cells, which are deficient in deoxycytidine kinase, were completely resistant to the antileukemic effects of 5-AZA-dCyd, whereas this analogue produced a very potent antileukemic effect against L1210 cells. To study the in vivo interaction of 5-AZA-dCyd and 3-DU with respect to drug resistance, mice were simultaneously injected i. v. with 10⁴ L1210 cells plus 10² L1210/ARA-C cells. A 9-h i. v. infusion of 5-AZA-dCyd (12.8 mg/kg) or 3-DU (186 mg/kg) produced an increase in life span of 56% and 26%, respectively. However, the sequential administration of 5-AZA-dCyd followed by 3-DU produced a 265% increase in life span and 7/10 longterm survivor, a very potent antileukemic effect. These results suggest that 3-DU is an excellent agent for use in combination chemotherapy to overcome drug resistance to the deoxycytidine analogue, 5-AZA-dCyd.This investigation was supported by grant MA-6356 from the Medical Research Council of Canada and by LEUCAN     

BCR基因5′启动子区多态性分析

背景与目的:bcr-abl融合基因被认为是慢性髓系白血病(chronic myelogenous leukemia,CML)的分子标志,该融合基因的表达受 bcr基因启动子的调控.本实验目的是研究 bcr基因启动子区的多态性,并探讨其与 CML之间可能存在的联系.方法:采用 PCR方法扩增 bcr基因 5′启动子区 1.13 kb的序列范围,通过测序获得了 30例 CML和 19例对照的启动子区序列.应用软件和在线工具对启动子序列进行转录因子结合位点分析和重复序列分析.结果:在所研究片段范围内共发现 4处新的单核苷酸多态性(single nucleotide polymorphism,SNP)和 3处与参考序列不一致的碱基变异.其中 2处 SNPs和 1处碱基插入位于转录因子结合位点中或邻近几个碱基内.各多态性基因频率在 CML和对照人群中无统计学差异.结论:bcr基因的 5′启动子区存在一定的序列多态性,主要为 SNPs,未能证实其与 CML之间存在相关性,但部分 SNPs的定位使其有可能对基因的转录和表达产生影响.     

Studies on the mechanism of the synergistic interaction between 2′-deoxy-5-azacytidine and cisplatin

Summary 2-Deoxy-5-azacytidine (5-aza-CdR) and cisplatin interact to produce synergistic cytotoxicity against many human tumor cell lines. Preliminary experiments designed to explore the mechanism of this synergy suggested a poor correlation between synergy and the degree of genomic hypomethylation measured following exposure to 5-aza-CdR. Subsequent studies using plasmid DNA suggested that rather than DNA hypomethylation, incorporation of 5-aza-CdR into DNA mediated increased cisplatin binding to DNA and could therefore be essential to the synergistic interaction between these two agents. In this series of experiments, we evaluated the degree of synergy with cisplatin produced against two human melanoma cell lines by two additional antimetabolites that were chosen on the basis of their biochemical properties. In addition, we investigated the synergy between 5-aza-CdR and cisplatin in parental and 5-aza-CdR-resistant murine cell lines, which differed in their sensitivity to 5-aza-CdR and DNA methylation status but incorporated similar amounts of 5-aza-CdR into DNA when exposed to this antimetabolite. In the studies testing additional antimetabolites, cytosine arabinoside, which is incorporated into DNA but does not hypomethylate it, produced synergy with cisplatin that was similar or superior to that obtained using 5-aza-CdR. With 3-deaza-adenosine, which is not incorporated into DNA but produces DNA hypomethylation through inhibition of S-adenosylhomocysteine hydrolase, a primarily antagonistic interaction was observed in the two cell lines studied. In the 5-aza-CdR-sensitive and-resistant cell lines, a very similar synergistic interaction was documented for 5-aza-CdR and cisplatin despite the significant difference observed in DNA methylation levels. Taken as a whole, these data suggest that DNA hypomethylation was not critical to the synergistic cytotoxicity produced by 5-aza-CdR and cisplatin. This finding suggests additional strategies that could further modulate this interaction.Supported in part by grants CA39853 and CA41524 from the United States Public Health Service     

骨髓瘤细胞5′-核苷酸酶染色研究

骨髓瘤细胞５′－核苷酸酶染色研究刘永春李彦会郝冀洪陈一丽用５′－核苷酸酶（５′－Ｎ）染色对血细胞进行观察，国外研究材料较多，国内仅李顺义等［１］用于巨核细胞研究。Ｅｌ－Ｍｏｈａｎｄｅｓ等［２］发现骨髓瘤细胞中５′－核苷酸酶活性较高，但以后报道材料较少...     

BCR基因5′启动子区多态性分析

背景与目的：bcr-abl融合基因被认为是慢性髓系白血病(chronic myelogenous leukemia,CML)的分子标志,该融合基因的表达受bcr基因启动子的调控。本实验目的是研究bcr基因启动子区的多态性,并探讨其与CML之间可能存在的联系。方法：采用PCR方法扩增bcr基因5’启动子区1．13kb的序列范围,通过测序获得了30例CML和19例对照的启动子区序列。应用软件和在线工具对启动子序列进行转录因子结合位点分析和重复序列分析。结果：在所研究片段范围内共发现4处新的单核苷酸多态性(single nucleotide polymorphism,SNP)和3处与参考序列不一致的碱基变异。其中2处SNPs和1处碱基插入位于转录因子结合位点中或邻近几个碱基内。各多态性基因频率在CML和对照人群中无统计学差异。结论：bcr基因的5’启动子区存在一定的序列多态性,主要为SNPs,未能证实其与CML之间存在相关性,但部分SNPs的定位使其有可能对基因的转录和表达产生影响。     

Anticancer efficacy of cisplatin and trichostatin A or 5-aza-2′-deoxycytidine on ovarian cancer

Background:

To evaluate the anticancer efficacy of the combination of epigenetic modifiers and cisplatin in human ovarian cancer.

Methods:

The effect of trichostatin A (TSA) and 5-aza-2′-deoxycytidine alone or in combination with low-dose cisplatin was evaluated on human ovarian cancer cell lines in vitro. We measured drug interaction by MTS assay, migration by transwell assay, expression of epithelial to mesenchymal transition (EMT) markers (Twist, Snail, Slug, E-cadherin, and N-cadherin), pluripotency markers (Oct4, Sox2, and Nanog), and epigenetic markers (DNMT3A, LSD1 and H3K4me2, H3K4me3, H3K9me2, and H3K9me3) by western blot, and the impact on and characteristics of spheroid growth when exposed to these drugs. Mouse xenografts were used to evaluate the anticancer effect of sequential drug treatment.

Results:

Combination treatment had greater efficacy than single drugs and significantly suppressed cell viability, migration, and spheroid formation and growth. Sequential treatment of cisplatin (1 mg kg⁻¹) followed by TSA (0.3 mg kg⁻¹) significantly suppressed tumorigenicity of HEY xenografts through inhibition of EMT and decreased pluripotency of ovarian cancer cells.

Conclusion:

Epigenetic modifiers potentiate the anticancer efficacy of low-dose cisplatin in ovarian cancer through regulation of EMT and pluripotency, and may provide a promising treatment for ovarian cancer patients.     

Antitumor activity of 3′, 5′-diesters of 5-fluoro-2′-deoxyuridine against murine leukemia L1210 cells

Summary Antitumor activity of several 3,5-diesters of 5-fluoro-2-deoxyuridine (FUdR) against L1210 leukemia cells following intraperitoneal administration was examined. Esters of FUdR with aromatic acid or aliphatic acid of longer chain length were markedly active. Their activities, with respect to ILS₃₀, were as much as 100 times that of unesterified FUdR. 3,5-ditoluoyl FUdR also had an improved therapeutic effect: its therapeutic ratio was increased to 8.1, as against 2.0 for FUdR. On the other hand, 3,5-diesters of FUdR with aliphatic acid of shorter chain length do not appear to be as active as FUdR. The relationship between the antitumor activity and plasma levels has also been examined. After 3,5-diacetyl FUdR, which is one of the drug group showing low cytotoxicity, the plasma concentration rapidly decreased to unmeasurable level 3 h after dosing. This tendency is similar to that shown in FUdR. On the other hand, with 3,5-dipalmitoyl FUdR and 3,5-dibenzoyl FUdR, each of which has a marked antitumor effect, plasma concentrations decreased slowly and were maintained for as long as 48 h after dosing. The results show that the cytotoxicity of diesters of FUdR is correlated with the duration of a high plasma level of FUdR.     

Polymorphisms in the 5′- and 3′-untranslated region of the <Emphasis Type="Italic">VEGF</Emphasis> gene and sporadic breast cancer risk and clinicopathologic characteristics

The wild and the variant alleles of the C936T and G634C vascular endothelial grow factor (VEGF) polymorphisms seem to be linked to higher angiogenic phenotype than the remaining alleles and may act on breast cancer (BC) origin. We investigated the influence of the VEGF C936T and G634C polymorphisms on the occurrence and clinicopathologic characteristics of sporadic breast cancer (SBC) in 235 patients and 235 controls. Peripheral blood samples of all individuals were analysed by the polymerase chain reaction for identification of genotypes and by enzyme-linked immunosorbent assay (ELISA) for quantification of serum VEGF levels. The variant 634CC genotype isolated (16.2% versus 10.7%, P  = 0.01) and in combination with the wild 936CC genotype (10.6% versus 5.5%, P  = 0.01) were more common in patients than in controls. The carriers of the respective genotypes were under a 2.20-fold and a 3.08-fold increased risks for the disease. Additionally, the frequency of the wild 936CC genotype was higher in patients with tumours of histological grade III compared to those with tumours of I+II histological grades (84.0% versus 64.7%, P  = 0.004) and in patients with positive oestrogen receptor tumours compared to those with tumours lacking oestrogen receptor expression (84.7% versus 73.9%, P  = 0.02). Similar serum values of VEGF were seen in patients and controls with the distinct genotypes of the VEGF. The data suggest that the VEGF wild 936CC and the variant 634CC genotypes constitute inherited determinants of SBC and SBC aggressiveness in Brazil, but are not significant predictors of circulating VEGF levels.     

Renal handling of 2′-deoxyadenosine and adenosine in humans and mice

Summary In a child lacking adenosine deaminase and in patients treated with deoxycoformycin (a potent inhibitor of the enzyme), apparent renal secretion of 2-deoxyadenosine (dAdo) and reabsorption of adenosine (Ado) were observed. The renal clearance of dAdo in humans was approximately five-fold that of creatinine, whereas the renal clearance of Ado was only one-fifth that of creatinine. In mice treated with deoxycoformycin, a similar paradigm was observed. Specifically, plasma levels of Ado and dAdo were elevated to detectable levels and apparent renal secretion and reabsorption of these purine nucleosides became manifest. Thus, the mouse may serve as a suitable model to study the renal handling of these two compounds. The active renal secretion of dAdo may occur because the compound has not been appreciably synthesized by mouse kidney in situ, and ion-trapping of dAdo in acid urine could not explain the net secretion. The differential transport of these similar purine nucleosides suggests a very selective transport system in mammalian kidney. Although carrier-mediated, facilitated diffusion of purine nucleosides across cell membranes is a well-known phenomenon, the present data indicate the existence of (an) active transport sysem(s) for the transepithelial secretion of dAdo, and possibly for the reabsorption of Ado.The abbreviations used in this paper are ADA adenosine aminohydrolase EC 3.5.4.4 - Ado adenosine - dAdo 2-deoxyadenosine - DCF 2-deoxycoformycin - HPLC high-performance liquid chromatography - PBS 0.14 M NaCl plus 0.01 M phosphate buffer, pH 7.4 - PNPase purine nucleoside: orthophosphate ribosyltransferase EC 2.4.2.1 - SCID: ADA^- severe combined immunodeficiency disease associated with ADA deficiency