Colonic transcriptional response to 1α,25(OH)2 vitamin D3 in African- and European-Americans.

Colorectal cancer (CRC) is a significant health burden especially among African Americans (AA). Epidemiological studies have correlated low serum vitamin D with CRC risk, and, while hypovitaminosis D is more common and more severe in AA, the mechanisms by which vitamin D modulates CRC risk and how these differ by race are not well understood. Active vitamin D (1α,25(OH)2D3) has chemoprotective effects primarily through transcriptional regulation of target genes in the colon. We hypothesized that transcriptional response to 1α,25(OH)2D3 differs between AA and European Americans (EA) irrespective of serum vitamin D and that regulatory variants could impact transcriptional response. We treated ex vivo colon cultures from 34 healthy subjects (16 AA and 18 EA) with 0.1µM 1α,25(OH)2D3 or vehicle control for 6h and performed genome-wide transcriptional profiling. We found 8 genes with significant differences in transcriptional response to 1α,25(OH)2D3 between AA and EA with definitive replication of inter-ethnic differences for uridine phosphorylase 1 (UPP1) and zinc finger-SWIM containing 4 (ZSWIM4). We performed expression quantitative trait loci (eQTL) mapping and identified response cis-eQTLs for ZSWIM4 as well as for histone deacetylase 3 (HDAC3), the latter of which showed a trend toward significant inter-ethnic differences in transcriptional response. Allele frequency differences of eQTLs for ZSWIM4 and HDAC3 accounted for observed transcriptional differences between populations. Taken together, our results demonstrate that transcriptional response to 1α,25(OH)2D3 differs between AA and EA independent of serum 25(OH)D levels. We provide evidence in support of a genetic regulatory mechanism underlying transcriptional differences between populations for ZSWIM4 and HDAC3. Further work is needed to elucidate how response eQTLs modify vitamin D response and whether genotype and/or transcriptional response correlate with chemopreventive effects. Relevant biomarkers, such as tissue-specific 1α,25(OH)2D3 transcriptional response, could identify individuals likely to benefit from vitamin D for CRC prevention as well as elucidate basic mechanisms underlying CRC disparities.

Enzymatic synthesis of 2'-deoxyuridine by whole cell catalyst co-expressing uridine phosphorylase and thymidine phosphorylase through auto-induction system.

Genes encoding uridine phosphorylase (UP) and thymidine phosphorylase (TP) from Escherichia coli K12 were cloned and recombined respectively into plasmids pET-21a(+) and pET-28a(+). The recombinant plasmids BL21/pET21a-UP and BL21/pET28a-TP were co-transformed into E. coli BL21(DE3) to construct highly effective BTU strain (BL21/pET28a-TP, pET21a-UP) overexpressing both of UP and TP. BTU was cultivated in ZYM-Fe-5052 medium for 10 h and used as catalyst to synthesize 2'-deoxyuridine (dUR). It was found to increase the productivity of dUR by 8-9 fold when compared to wild E. coli K12 and E. coli BL21(DE3) strains. A series of experiments were carried out to find out the optimal conditions for synthesis of dUR. At 50°C, with 0.25‰ dry wt./v to catalyze the reaction of 2:1 ß-thymidine: uracil (60 mM ß-thymidine, 30 mM uracil), the conversion rate of dUR would reach 61.6% at 1 h, which was much higher than the rates obtained by BTU strain cultured in LB medium and induced by IPTG. This result proved co-expression and auto-induction were efficient methods in enhancing the expression quantity and activity of nucleoside phosphorylases, and they also had significant implications for large-scale industrial production of dUR and synthesis of other nucleoside derivatives.

Peroxisome proliferator-activated receptor gamma coactivator-1alpha enhances antiproliferative activity of 5'-deoxy-5-fluorouridine in cancer cells through induction of uridine phosphorylase.

Peroxisome proliferator-activated receptor gamma coactivator-1alpha (PGC-1alpha) is capable of coactivating several nuclear receptors and transcription factors that participate in the regulation of multiple metabolic processes, including gluconeogenesis, mitochondrial biogenesis, and adaptive thermogenesis. Uridine phosphorylase (UPase) catalyzes the reversible conversion of uridine into uracil and contributes to the antineoplastic activity of 5'-deoxy-5-fluorouridine (5'-DFUR) and homeostasis of uridine levels in plasma and tissues. This study demonstrates uridine phosphorylase as a novel target gene of PGC-1alpha, which induces the transcription and enzymatic activity of UPase in various cancer cells and thus augments their susceptibility to 5'-DFUR. PGC-1alpha-induced activation of UPase expression occurs at its transcription level that is mediated by an estrogen-related receptor (ERR) binding site (-1078 to -1070 base pairs) mapped in the promoter region of UPase gene. Our mutational studies using luciferase reporter construct together with electrophoretic mobility shift assays confirm the binding of ERR to PGC-1alpha-responsive element. Moreover, the inhibition of PGC-1alpha/ERRalpha-dependent signaling by 3-[4-(2,4-bis-trifluoromethylbenzyloxy)-3-methoxyphenyl]-2-cyano-N-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)acrylamide (XCT790) compromises the ability of PGC-1alpha to induce the transcript of UPase, indicating PGC-1alpha-dependent and ERRalpha-mediated up-regulation of UPase. Finally, the overexpression of PGC-1alpha sensitizes breast and colon cancer cells to growth inhibition by 5'-DFUR presumably by inducing apoptosis in tumor cells and XCT790 can inhibit the process. Taken together, our results corroborate the regulatory function of PGC-1alpha in uridine homeostasis and imply its links with the energy metabolism. The mechanistic elucidation of this association between both cellular pathways should advance the clinical use of 5-fluorouracil-based chemotherapy.

Uridine phosphorylase in breast cancer: a new prognostic factor?

Uridine phosphorylase (UPase) is an enzyme that converts the pyrimidine nucleoside uridine into uracil. Upon availability of ribose-1-phosphate, UPase can also catalyze the formation of nucleosides from uracil as well as from 5-fluorouracil, therefore involved in fluoropyrimidine metabolism. UPase gene expression is strictly controlled at the promoter level by oncogenes, tumor suppressor genes, and cytokines. UPase activity is usually elevated in various tumor tissues, including breast cancer, compared to matched normal tissues and this induction appears to contribute to the therapeutic efficacy of fluoropyrimidines in cancer patients. In this review, we will discuss in detail the role of UPase in the activation of fluoropyrimidines and its effect on the prognosis of breast cancer patients.

Up-regulated expression of the uridine phosphorylase gene in human gastric tumors is correlated with a favorable prognosis.

Uridine phosphorylase (UP) is one of the enzymes involved in 5-fluorouracil (5-FU) activation. The expression was compared in paired specimens from cancerous and non-cancerous regions of gastric, colon and lung cancer patients. Among 28 paired gastric samples, 20 cases showed greater expression in tumors than in normal surrounding tissues and 8 cases showed equal or lower expression levels in tumors. All the gastric patients received 5-FU before and/or after the surgical resection and the prognosis of the patients, whose UP tumor expression increased, was relatively better than that of the patients with equal or less UP gene tumor expression. In contrast, most of the colon (22 cases in total) and all the lung cancer patients (14 in total) did not receive 5-FU and the majority of the colon (12 cases) and lung (10 cases) specimens showed lower expression in the cancerous region. The differential expression between cancerous and non-cancerous regions in colon and lung cancers was not linked with the prognosis. These data suggest that the paired expression level of the UP gene in gastric cancer is a possible prognostic marker for the patients who received 5-FU.

Expression of genes for 5-FU-metabolizing enzymes and response to irinotecan plus 5-FU-leucovorin in colorectal cancer.

BACKGROUND: 5-Fluorouracil (5-FU) is initially catabolized by dihydropyrimidine dehydrogenase. Thymidylate synthase (TS) is the target enzyme of 5-FU. In addition, activation of 5-FU to form various nucleotides via three pathways requires phosphorylation by orotate phosphoribosyltransferase, thymidine phosphorylase and uridine phosphorylase, respectively. The aim of this study was to assess the predictive value of the expression of these genes in patients receiving irinotecan plus 5-FU/leucovorin therapy (IFL) for colorectal cancer. PATIENTS AND METHODS: Twenty-seven patients with metastatic, or recurrent colorectal cancer were studied. Enzyme gene expression was measured in primary tumors by the real-time reverse transcription PCR method. RESULTS: The TS mRNA level was significantly higher in the responders than in the non-responders (p=0.0409). CONCLUSION: The effect of IFL therapy may be determined by the extent of TS mRNA expression. It is suggested that assay of TS mRNA may be useful for predicting the effect of intravenous regimens such as FOLFIRI.

Functional analysis of the EWS/ETS target gene uridine phosphorylase.

The EWS/ETS fusion proteins associated with Ewings family tumors (EFTs) are thought to promote oncogenesis by acting as aberrant transcription factors. Uridine phosphorylase is a gene that is up-regulated by structurally distinct EWS/ETS fusions. Ectopic expression of uridine phosphorylase was able to support anchorage-independent cell growth, indicating that it plays an active role in the oncogenic process. Transcriptional up-regulation of uridine phosphorylase is shown to be mediated in a DNA binding-dependent manner, and reporter gene assays demonstrated that EWS/FLI1 and RAS mediate activation through a single activator protein 1/ETS site located in the uridine phosphorylase promoter. Chromatin immunoprecipitation assays reveal that EWS/FLI1 directly associates with the uridine phosphorylase promoter in vivo. Up-regulation of uridine phosphorylase by EWS/FLI1 sensitizes cells to growth inhibition by the pyrimidine analogue, 5'-deoxy-5'fluorouridine, both in tissue culture and in vivo model systems.

Expression of uridine and thymidine phosphorylase genes in human breast carcinoma.

Uridine phosphorylase (UPase) and an angiogenic enzyme, thymidine phosphorylase (dThdPase) are involved in degradation of the pyrimidine nucleosides through phosphorolysis. The expression levels of UPase and dThdPase are higher in human solid tumors including breast carcinomas than in normal tissues. To clarify the correlation between the expression levels of UPase and dThdPase genes and the clinicopathological factors, mRNA levels of these enzymes were examined by RT-PCR in 43 breast carcinomas. UPase gene expression was not correlated with dThdPase gene expression (regression coefficient R = 0.032). Although the expression level of the dThdPase gene was correlated with angiogenesis, detected by immunostaining endothelial cells (R = 0.66), that of UPase gene was not (R = 0.044). These results suggest that UPase does not have a strong angiogenic activity. The UPase gene expression levels in tumors of patients who relapsed were significantly higher than in those from patients who did not (p = 0.039). Although the expression levels of neither UPase or dThdPase were associated with age, pT, pN, pM, estrogen or progesterone receptor positivity, the patients with the higher levels of UPase gene expression had worse survival (p = 0.0038) than those with lower levels. In contrast, the expression of dThdPase gene was not related to relapse or survival of these patients with breast carcinoma. Our findings suggest that the expression level of UPase gene may be an independent prognostic marker in human breast carcinoma.

Overexpression of Escherichia coli genes encoding nucleoside phosphorylases in the pET/Bl21(DE3) system yields active recombinant enzymes.

The Escherichia coli genes encoding purine nucleoside phosphorylase, uridine phosphorylase, and thymidine phosphorylase were cloned into pET plasmids to generate highly effective E. coli BL21(DE3) strains producing each of these enzymes. Optimum conditions for biosynthesis of each enzyme as a soluble protein with intact biological activity were found. The crude preparations are approximately 80% pure and can be used immediately for enzymatic transglycosylation. The enzyme preparations were purified to homogeneity by two steps including fractional precipitation with ammonium sulfate and subsequent chromatography on Sephadex G-100 and DEAE-Sephacel.

p53-dependent suppression of uridine phosphorylase gene expression through direct promoter interaction.

Uridine phosphorylase (UPase) is a key enzyme in the pyrimidine salvage pathway. It reversibly catalyzes the catabolism of uridine to uracil; controls the homeostatic regulation of uridine concentration in plasma and tissues; and plays a role in the intracellular activation of 5-fluorouracil. We cloned the murine UPase gene promoter, a 1703-bp fragment, and determined the transcription initiation sites located at +1 and +92 bp of the cDNA sequence. Through transient expression analysis of the 5'-flanking region of UPase gene, we have evaluated the promoter activity for a series of fragments with 5'- to 3'-deletion in murine breast cancer EMT-6 cells and immortalized murine fibroblast NIH 3T3 cells. Cotransfection of the UPase promoter constructs (from -1619 to -445) containing p53 binding motif with the wild-type p53 construct resulted in a significant reduction of luciferase activity; however, this effect disappeared with the additional deletion of the -445 to -274 sequence to suggest the existence in this promoter region of a putative p53 recognition element. Similar cotransfection in murine embryo fibroblasts p53-/- confirmed the inhibitory role of p53 on the UPase promoter activity. The specificity of the interaction is demonstrated by nuclear protein-specific binding to the putative p53 recognition sequence using gel mobility shift assay and DNase I footprinting analysis. These data indicate the UPase gene is a novel target of p53, and its expression is down-regulated by p53 at the promoter level.

Fluoropyrimidine sensitivity of human MCF-7 breast cancer cells stably transfected with human uridine phosphorylase.

The relationship between uridine phosphorylase (UP) expression level in cancer cells and the tumour sensitivity to fluoropyrimidines is unclear. In this study, we found that UP overexpression by gene transfer, and the subsequent efficient metabolic activation of 5-fluorouracil (5-FU) by the ribonucleotide pathway, does not increase the fluoropyrimidine sensitivity of MCF-7 human cancer cells.

Expression, characterization, and detection of human uridine phosphorylase and identification of variant uridine phosphorolytic activity in selected human tumors.

Uridine phosphorylase (UPase) catalyzes the reversible phosphorolysis of uridine to uracil. We purified the enzyme from the murine colon 26 tumor using a two-step procedure through 5-amino-benzylacyclouridine affinity chromatography. Antibodies raised in rabbits against the purified protein revealed single bands in Western blots of normal human tissue and tumor extracts. The polyclonal antibody used to screen a human liver expression library allowed the isolation of a 1.2-kb clone that contained the entire open reading frame of the human UPase. The UPase cDNA has been expressed as a fusion protein in Escherichia coli using the pMal-C2 vector. The kinetic analysis demonstrated that the recombinant UPase preferentially uses uridine, 5-fluorouracil, and uracil as substrates, although lower levels of activity were observed with 2-deoxyuridine and thymidine. Clinical samples of human tumors and adjacent normal tissues were assayed for phosphorolytic activity and sensitivity to 5-benzylacyclouridine (BAU), a potent inhibitor of the enzyme presently in Phase I-II clinical trial. Activity in normal tissues appeared to be low but very sensitive to BAU (approximately 90% inhibition at 10 microM). Tumors had generally 2-3-fold greater activity compared with adjacent normal tissues. In breast cancer specimens and head-neck squamous carcinomas, however, uridine cleavage was only partially inhibited (40-60%) by 10 or 100 microM BAU. The BAU-insensitive activity requires phosphate and pH conditions similar to the normal enzyme, and the new phosphorolytic activity was independent from thymidine phosphorylase. The BAU-insensitive phosphorolytic activity in selected tumors, coupled with the potent inhibitory activity of BAU against the "classical" uridine phosphorylase in normal human tissues, provides the rationale for combining BAU with 5-fluorouracil in the treatment of breast and head-neck tumors.

[Protein engineering of uridine phosphorylase from Escherichia coli K-12. I. Cloning and expression of uridine phosphorylase genes from Klebsiella aerogenes and Salmonella typhimurium in E. coli]. / Belkovaia inzheneriia uridinofosforilazy iz Escherichia coli K-12. I. Klonirovanie i ékspressiia v E. coli genov uridinofosforilaz iz Klebsiella aerogenes i Salmonella typhimurium.

Genes of uridine phosphorylases (udp) from Klebsiella aerogenes and Salmonella typhimurium were cloned and expressed. Highly effective producer strains of the corresponding proteins were constructed. Enzymic properties of the UPases obtained were studied and compared with those from the Escherichia coli enzyme. Mutant forms of UPase from E. coli (D5E, D5N, D5A) were prepared by site-directed mutagenesis techniques. It was shown that the Asp5 residue plays an insignificant role in the formation of the active form of the protein.

Cloning and expression of human uridine phosphorylase.

Using a mouse cDNA probe we have identified a human uridine phosphorylase cDNA clone from the cDNA library of a human colorectal tumor cell line, HCT116. The recombinant human uridine phosphorylase expressed in COS-7 cells demonstrated specific enzyme activity with uridine as the substrate; this activity was inhibited by the competitive inhibitor 2,2'-anhydro-5-ethyluridine. Northern blot analysis with the cDNA as a probe demonstrated high levels of mRNA expression in several tumor cell lines but very low level in normal cell, WI-38. The expression of uridine phosphorylase mRNA in HCT-116 cells was further enhanced by treating the cells with vitamin D3 and the inflammatory cytokines: tumor necrosis factor alpha, interleukin 1 alpha and interferon gamma.

Purification, cloning, and expression of murine uridine phosphorylase.

Uridine phosphorylase was purified 10,300-fold from tumors of the murine colorectal adenocarcinoma cell line, Colon-26. Degenerate DNA probes were synthesized corresponding to partial amino acid sequences and used to screen a Colon-26 cDNA library. A cDNA clone of 1327 base pairs that contains a 5' untranslated region, a coding region of 933 base pairs, and a 3' nontranslated region with a polyadenylated tail was identified. The cDNA was confirmed to be uridine phosphorylase by 1) sequence comparison to uridine phosphorylase of Escherichia coli, 2) substrate specificity studies with recombinant protein expressed in COS-7 cells that demonstrated relatively high enzyme activity with uridine as substrate compared low levels when thymidine was used, and 3) inhibition of enzyme activity by the competitive inhibitor 2,2'-anhydro-5-ethyluridine. Northern blot analysis using the cDNA as a probe, demonstrated high levels of mRNA expression in Colon-26. Expression was low in NIH3T3 cells, but high in DMBA-3 and PH-1 cells, which are NIH3T3-derived cells that have been transformed with mutated murine Ha-ras and viral Ha-ras, respectively. Expression of uridine phosphorylase mRNA in these cell lines was further enhanced by treating the cells with the inflammatory cytokines, tumor necrosis factor-alpha, interleukin 1 alpha, and interferon gamma.

Tn10-mediated inversions fuse uridine phosphorylase (udp) and rRNA genes of Escherichia coli.

Two strains carrying metE::Tn10 insertions (upstream of the udp gene) were used to isolate mutants of Escherichia coli overexpressing udp. These strains differ in their gene order; one contains an inversion between the rrnD and rrnE rRNA operons. Selection was based on the ability of overexpressed Udp to complement thymine auxotrophy. Chromosomal rearrangements that connect the udp gene and promoters of different rrn operons were obtained by this selection. Seven of 14 independent mutants selected in one of the initial strains contained similar inversions of the metE-rrnD segment of the chromosome (about 12% of its length). Another mutant contained traces of a more complicated event, inversion between rrnB and rrnG operons, which was followed by reinversion of the segment between metE and the hybrid rrnG/B operon. Similar inversions (udp-rrn) in a strain already carrying an rrnE-rrnD inversion flip the chromosomal segment between metE and rrnD/E in the opposite direction. In this case, inversions are also accompanied by duplications of the chromosomal region between the rrnA and hybrid udp-rrnD/E operons. PCR amplification with a set of oligonucleotides from the rrn, Tn5, and met genes was used for more detailed mapping. Amplified fragments of the rearranged chromosomes connecting rrnD sequences and insertion elements were sequenced, and inversion endpoints were established.

Cytokines induce uridine phosphorylase in mouse colon 26 carcinoma cells and make the cells more susceptible to 5'-deoxy-5-fluorouridine.

The antiproliferative activity of 5-fluorouracil (5-FUra) and 5'-deoxy-5-fluorouridine (5'-dFUrd), used in combination with typical cytokines and growth factors, was investigated in mouse colon 26 carcinoma cells. Tumor necrosis factor alpha (TNF alpha), interleukin-1 alpha (IL-1 alpha), and interferon gamma (IFN gamma) at low doses showing < 50% inhibition of cell growth by themselves enhanced the susceptibility of the cells to the activity of 5'-dFUrd. In particular, a mixture of these cytokines greatly enhanced the activity of 5'-dFUrd and 5-FUra by up to 12.4- and 2.7-fold, respectively, whereas the activity of other cytostatics was only slightly changed (< 1.5-fold). Basic fibroblast growth factor also increased the susceptibility, but only to 5'-dFUrd. This preferential enhancement of the activity of 5'-dFUrd would be due to induction by the cytokines of uridine phosphorylase (Urd Pase), by which 5'-dFUrd is converted to 5-FUra. TNF alpha, IL-1 alpha, IFN gamma, and a mixture of these factors increased the enzyme activity by up to 3.7-fold in colon 26 cells. Consequently, the anabolism of 5'-dFUrd to fluoronucleotides and the incorporation of 5-FUra into RNA in colon 26 cells were increased by TNF alpha treatment. In addition, the increase by the cytokine mixture in the susceptibility to 5'-dFUrd was abolished by an inhibitor of Urd Pase, 2,2'-anhydro-5-ethyluridine. These results indicate that induction of Urd Pase activity by cytokines is a critical event that increases the susceptibility to 5'-dFUrd.

[Regulation of uridine phosphorylase gene activity in Escherichia coli K-12. II. A study of the nature of the constitutive synthesis of uridine phosphorylase in the rho15(ts) genome]. / Reguliatsiia aktivnosti gena uridinfosforilazy u Escherichia coli K-12. soobshchenie II. Izuchenie prirody knostitutivnogo sinteza uridinfosforilazy v genome rho15(ts).

The nature of uridine phosphorylase constitutive synthesis was studied in the rho15(ts) mutant strain of Escherichia coli. The rho15 mutation causes the 8-10 fold increase in uridine phosphorylase activity under conditions of both induction of enzyme synthesis by cytidine and complete inhibition of the udpP promoter activity in the crp background. These data indicate that regulation of the udp gene which is controlled by the cytR repressor protein and by cyclic AMP -- CRP complex, is disturbed in the presence of the mutated rho factor. Introduction of the rho15 mutation into the udpP1 and udpP18 promoter mutants which are characterized by cytR and (or) CRP independent expression of the udp gene, leads to 2 fold reduction in uridine phosphorylase activity. From this, it may be concluded that the presence in bacteria of the rho15 mutation prevents transcription initiation from the intact udpP+ promoter and also leads to udpP1 and udpP18 mutant promoters inhibition. On the basis of these data, it is proposed that the effect of rho15 mutation on the udp gene expression is rather due to read-through transcription from an upstream highly efficient foreign promoter, than to relief of attenuation within the udp gene regulatory region. The uridine phosphorylase activity under control of this foreign promoter, i.e. in the rho15 genome, is reduced 2-3 fold when bacteria are grown on the minimal medium supplemented with L-methionine or casaamino acids. Based on these dat, it is suggested that increased udp gene expression in the rho15 background is due to read-through transcription, possibly, from the promoter of the neighbouring metE gene.

[Effect of the ts 15 mutation of transcription termination factor rho on expression of the uridine phosphorylase gene of Escherichia coli]. / Vliianie mutatsii po faktoru terminatsii transkriptsii rho ts 15 na vyrazhenie uridinfosforilaznogo gena u Escherichia coli.

The expression of nucleoside-catabolizing genes was studied in two isogenic strains, SA1030(rho+) and AD1600(rho ts 15). The deo-enzymes activities do not differ markedly in these two strains, though when cells were grown on glycerol medium the deo-enzymes level appeared to be higher than on glucose medium. The synthesis of uridine phosphorylase in AD1600 strain was found to be constitutive. It was found also that the cytR regulation system was not altered in AD1600 strain and a wild-type allele of udp gene was present in the genome of AD1600 strain. A conclusion is made that constitutive synthesis of uridine phosphorylase is due to the presence of rho ts 15 mutation in the genome of the strain AD1600.