Levels Of Dihydrofolate Reductase Research Articles

Procyanidin B2 ameliorates endothelial dysfunction induced by nicotine via the induction of tetrahydrobiopterin synthesis

• Nicotine decreases the expression of DHFR and GCH1 to inhibit BH 4 and NO production. • PCB2 prevents nicotine-induced DHFR and GCH1 loss. • PCB2 improves endothelium-dependent vasorelaxation impaired by nicotine. • PCB2 induces vasorelaxation through a PPARδ-BH 4 dependent manner. Smoking is an independent risk factor for the cardiovascular diseases. Nicotine, a major component of tobacco, is responsible for the impaired endothelial-dependent vasorelaxation in smokers. Procyanidin B2 (PCB2), a natural flavonoid, has been reported to possess several potential beneficial effects on the cardiovascular system. However, whether PCB2 prevents nicotine-induced endothelial dysfunction remains unknown. In this study, we demonstrated that PCB2 improved nicotine-impaired endothelium-dependent vasorelaxation in mouse thoracic aortas. Mechanistically, PCB2 increased the expression levels of dihydrofolate reductase (DHFR) and GTP cyclohydrolase 1 (GCH1), two important enzymes in the synthesis of tetrahydrobiopterin (BH 4 ), in mouse aortas and cultured ECs. GSK0660, a selective antagonist of peroxisome proliferator-activated receptor δ (PPARδ), abolished the PCB2-induced effects on BH 4 synthesis, nitric oxide (NO) production and vasodilation. Collectively, we demonstrated that PCB2 mitigates nicotine-induced endothelial dysfunction through a PPARδ-BH 4 dependent manner, thereby suggesting a novel role of PCB2 in preventing vascular dysfunction caused by nicotine exposure.

Endothelial NOX4 aggravates eNOS uncoupling by decreasing dihydrofolate reductase after subarachnoid hemorrhage.

Endothelial malfunction is a major contributor to early or delayed vasospasm after subarachnoid hemorrhage (SAH). As a representative form of endothelial dysfunction, endothelial nitric oxide synthase (eNOS) uncoupling leads to a reduction in nitric oxide (NO) generated by endothelial cells. In this study, we investigated how the interaction between endothelial NOX4 (nicotinamide adenine dinucleotide phosphate oxidase 4) and DHFR (dihydrofolate reductase) contributes to eNOS uncoupling after SAH. Setanaxib and the adeno-associated virus (AAV) targeting brain vascular endothelia were injected through the tail vein and the expression and localization of proteins were examined by western blot and immunofluorescence staining. The NO content was measured using the NO assay kit, and laser speckle contrast imaging was used to assess cortical perfusion. ROS (reactive oxygen species) level was detected by DHE (dihydroethidium) staining, DCFH-DA (2',7'-dichlorofluorescin diacetate) staining and H2O2 (hydrogen peroxide) measurement. The Garcia score was employed to examine neurological function. Setanaxib is widely used for its preferential inhibition for NOX1/4 over other NOX isoforms. After endothelial NOX4 was inhibited by Setanaxib in a mouse model of SAH, the endothelial DHFR level was significantly elevated, which attenuated eNOS uncoupling, increased cortical perfusion, and improved the neurological function. The protective role of inhibiting endothelial NOX4, however, disappeared after knocking down endothelial DHFR. Our results suggest that endothelial DHFR decreased significantly because of the elevated level of endothelial NOX4, which aggravated eNOS uncoupling after SAH, leading to decreased cortical perfusion and worse neurological outcome.

Palbociclib regulates the expression of dihydrofolate reductase and the cell cycle to inhibit t (11;14) multiple myeloma.

BackgroundMultiple myeloma (MM) with t (11;14) has a unique biology. New combinations of novel agents are needed to improve the prognosis of patients with t (11;14) MM. As a selective inhibitor of cyclin-dependent kinases 4 and 6 (CDK4/6), palbociclib (PAL) has been used to treat various malignancies, including breast cancer, ovarian cancer, and so on. However, the effects of PAL on MM remain unclear, and thus, further investigations are warranted.MethodsTwo t (11;14) MM cell lines, U266 and KMS27, were used in this study. The cell viability and cell cycle were detected to evaluate the anti-myeloma effect of the combination of pralatrexate (PTX) and methotrexate (MTX) with PAL. Three-dimensional (3D) spheroid and mouse models were built to verify the effect of the combination treatment. Western blot was used to detect the expressions of Minichromosome Maintenance Complex Component 2 (MCM2), Minichromosome Maintenance Complex Component 3 (MCM3), and dihydrofolate reductase (DHFR).ResultsIt was observed that PAL had obvious anticancer effects on U266 and KMS27 cells, which had synergistic effects together with PTX and MTX. Importantly, it was found that PAL could promote cell cycle genes including MCM2 and MCM3, and increase the number of MM cells in the G1 phase. Moreover, PAL reduced the expression level of DHFR and exerted its anticancer effects on MM cells by targeting DHFR. It was also determined that PAL exerted anticancer effects on MM in the spheroid and mouse models.ConclusionsPAL exerted obvious anticancer effects on t (11;14) MM cells, which had synergistic effects together with PTX and MTX. PAL could promote cell cycle genes and the G1 phase of MM cells. Moreover, PAL reduced the expression level of DHFR and exerted its anticancer effects on t (11;14) MM cells by targeting DHFR.

Inhibition of Protein Kinase CK2 Affects Thymidylate Synthesis Cycle Enzyme Level and Distribution in Human Cancer Cells.

Thymidylate synthase (TS), dihydrofolate reductase (DHFR), and serine hydroxymethyltransferase (SHMT) constitute the thymidylate synthesis cycle providing thymidylate for DNA synthesis and repair. Our previous studies indicated that TS and DHFR are the substrates of protein kinase CK2. This work has been aimed at the elucidation of the effect of CK2 activity on cell cycle progression, thymidylate synthesis enzyme expression and localization, and the role of CK2-mediated TS phosphorylation in in vitro di- and trimolecular complex formation. The results were obtained by means of western blot, confocal microscopy, flow cytometry, quantitative polymerase chain reaction (QPCR), quartz crystal microbalance with dissipation monitoring (QCM-D), and microthermophoresis (MST). Our research indicates that CK2 inhibition does not change the levels of the transcripts; however, it affects the protein levels of DHFR and TS in both tested cell lines, i.e., A549 and CCRF-CEM, and the level of SHMT1 in CCRF-CEM cells. Moreover, we show that CK2-mediated phosphorylation of TS enables the protein (pTS) interaction with SHMT1 and leads to the stability of the tri-complex containing SHMT1, DHFR, and pTS. Our results suggest an important regulatory role of CK2-mediated phosphorylation for inter- and intracellular protein level of enzymes involved in the thymidylate biosynthesis cycle.

MiR-192 overexpression effect on DHFR and TYMS in acute lymphoblastic leukemia

PurposeNon-coding RNAs play a critical role in gene regulation in cancer cells. Reduced expression of microRNA-192 has been detected in many cancers. Here, we investigated the role of miR-192 in Dihydrofolate reductase (DHFR) and Thymidylate Synthase (TYMS) expression level and in an acute lymphoblastic leukemia cell line. Basic procedures20 patients diagnosed with acute lymphoblastic leukemia (ALL) were studied for the level of (micro RNA-192) miR-192, DHFR and TYMS expression level by qRT-PCR. NALM-6 cells were transduced using recombinant lentiviruses for overexpression of miR-192 and its backbone, then the relative changes in DHFR and TYMS genes expression were studied by qRT-PCR. DHFR Protein level changes were analyzed by Western blotting. Main findingsALL patients with relapse, experience lower levels of miR-192 and higher levels of DHFR and TYMS in comparison with treated patients. Overexpression of miR-192 in NALM-6 cells resulted in decreased expression of DHFR and TYMS. Moreover, the protein level of DHFR was decreased after overexpression of miR-192. Principal conclusionsThese results suggest the tumor suppression effects of miR-192 and its correlation with decreased DHFR and TYMS level in acute lymphoblastic leukemia cells for the first time.

Propolis Potentiates Methotrexate Anticancer Mechanism and Reduces its Toxic Effects

Egyptian propolis is a powerful antioxidant and free radical scavenger produced by bees. The current study was designed to characterize Egyptian propolis, investigate its anticancer effect in vitro and its protective role against methotrexate (MTX) toxicity in Ehrlich ascites carcinoma (EAC) experimental model. Our results revealed a high content of total phenolics, flavonoids and dihydroflavonols in propolis ethanolic extract (PEE). PEE prompted cytotoxic effects in cancer cell lines and antitumor effects against EAC mice model by reducing tumor volume, count of viable tumor cells with a significant elevation in the life span as well as the mean survival time of mice. The hepatic and renal biochemical and toxicity parameters of EAC-bearing mice treated with MTX were improved by PEE. Also, it elevates the expression of Bax, caspase-3 and cytochrome-C and reduces the Bcl2 expression in EAC cells. Moreover, PEE with MTX induced cell cycle arrest at the G0/G1 phase. Interestingly, the combination of PEE with MTX showed potent apoptosis as shown by DNA fragmentation gel, comet assay and dihydrofolate reductase level (DHFR). These findings demonstrate that Egyptian propolis extract had high chemical diversity and different antioxidant effects. Also, it optimizes the antitumor potential of MTX and declined its toxic effects.

PPARδ agonist prevents endothelial dysfunction via induction of dihydrofolate reductase gene and activation of tetrahydrobiopterin salvage pathway.

Impaired endothelium-dependent relaxation (EDR) is a hallmark of endothelial dysfunction. A deficiency of tetrahydrobiopterin (BH4 ) causes endothelial NOS to produce ROS rather than NO. PPARδ is an emerging target for pharmacological intervention of endothelial dysfunction. Thus, the present study examined the role of PPARδ in the regulation of dihydrofolate reductase (DHFR), a key enzyme in the BH4 salvage pathway. Gene expression was measured by using qRT-PCR and western blotting. Biopterins and ROS were determined by using HPLC. NO was measured with fluorescent dye and electron paramagnetic resonance spectroscopy. Vasorelaxation was measured by Multi Myograph System. The PPARδ agonist GW501516 increased DHFR and BH4 levels in endothelial cells (ECs). The effect was blocked by PPARδ antagonist GSK0660. Chromatin immunoprecipitation identified PPAR-responsive elements within the 5'-flanking region of the human DHFR gene. The promoter activity was examined with luciferase assays using deletion reporters. Importantly, DHFR expression was suppressed by palmitic acid (PA, a saturated fatty acid) but increased by docosahexaenoic acid (DHA, a polyunsaturated fatty acid). GSK0660 prevented DHA-induced increased DHFR expression. Conversely, the suppressive effect of PA was mitigated by GW501516. In mouse aortae, GW501516 ameliorated the PA-impaired EDR. However, this vasoprotective effect was attenuated by DHFR siRNA or methotrexate. In EC-specific Ppard knockout mice, GW501516 failed to improve vasorelaxation. PPARδ prevented endothelial dysfunction by increasing DHFR and activating the BH4 salvage pathway. These results provide a novel mechanism for the protective roles of PPARδ against vascular diseases.

Luminespib plus pemetrexed in patients with non-squamous non-small cell lung cancer

BackgroundLuminespib (AUY922) is a second-generation heat shock protein 90 (HSP90) inhibitor with demonstrated activity in non-small cell lung cancer (NSCLC). Since luminespib reduces levels of dihydrofolate reductase (DHFR), a key enzymatic target of pemetrexed, we assessed the safety and tolerability of luminespib in combination with pemetrexed in patients with previously treated metastatic non-squamous non-small cell lung cancer (NSCLC). We also sought to study the pharmacokinetics and correlate tumor dihydrofolate reductase (DHFR) expression with clinical response. MethodsPatients received weekly luminespib at either 40 mg/m2, 55 mg/m2, or 70 mg/m2 according to a standard 3 + 3 dose-escalation design along with pemetrexed at 500 mg/m2 followed by an expansion at the maximum tolerated dose (MTD). ResultsTwo-dose limiting toxicities (DLTs) were experienced in the 70 mg/m2 cohort, therefore the MTD was determined to be 55 mg/m2. 69% (N = 9) of patients experienced ophthalmologic toxicity related to luminespib. Maximum serum concentration (Cmax) of luminespib was associated with increased grade 2 drug related adverse events (DRAEs) (rs = 0.74, P < 0.01), with volume of distribution (VD) inversely associated with the number of DRAEs (rs = − 0.81, P = 0.004) and ophthalmologic related DRAEs (rs = − 0.65, P = 0.04). The best response was partial response in one patient for 20 months, prior to expiration of all luminespib. Amongst patients treated at the MTD, the objective response rate was 14%. ConclusionIn patients with previously treated metastatic NSCLC, the MTD of luminespib in combination with pemetrexed was 55 mg/m2 per week. The combination of luminespib and pemetrexed demonstrated clinical activity. Tolerability of luminespib with pemetrexed is limited by ocular toxicity.

MiRNA-24 Gene Sequence, DHFR -829C-T Genotypes, and Methotrexate Response in Mexican Patients with Rheumatoid Arthritis.

Aim: The present study looked for variation in the miRNA-24 sequence, and evaluated the associations between the dihydrofolate reductase (DHFR) gene-829 C-T polymorphism and plasma DHFR concentrations with response to methotrexate (MTX) treatment in Mexican patients with rheumatoid arthritis (RA).Methods: A total of 135 women with RA were classified as responders (disease activity score [DAS28] <3.2) or nonresponders to MTX (DAS28 > 3.2). We determined the genotype of the patients using the polymerase chain reaction-restriction fragment length polymorphism method. Plasma DHFR enzyme levels and mi-RNA24 sequences were assessed by enzyme-linked immunosorbent assay (ELISA) and Sanger sequencing, respectively. Allelic frequencies and the genotypic distribution of the polymorphism were analyzed by the chi-square test.Results: The genotype frequencies of the DHFR −829C-T polymorphism among responders were 37.0% CC, 52.1% CT, and 10.9% TT and for nonresponders were 33.9% CC, 56.4% CT, and 9.7% TT. No significant differences in genotype frequencies were found between the groups (p = 0.88). The DHFR levels relative to genotype for responders were 6.8 ± 2.7, 6.1 ± 2.7, and 6.5 ± 1.5 ng/mL for CC, CT, and TT, respectively, and for nonresponders were 6.5 ± 2.0, 6.1 ± 3.1, and 7.4 ± 1.8 ng/mL for CC, CT, and TT, respectively. No significant differences were found between the two groups. Similarly, both groups showed no sequence variations in miRNA-24 gene.Conclusion: The −829C-T polymorphism of DHFR gene was not associated with response to MTX by RA patients, and no variations were found in the miRNA-24 sequence that might modify the response to treatment or DHFR enzyme levels in a Mexican population with RA.

Clinical efficacy and mechanism of Pralatrexate combined with Palbociclib Isethionate in treatment of bladder cancer patients.

The clinical efficacy and mechanism of Pralatrexate (PTX) combined with Palbociclib Isethionate (PAL) in the treatment of bladder cancer patients was investigated. A retrospective analysis of medical records of 82 bladder cancer patients admitted to Shengjing Hospital of China Medical University from February 2015 to February 2018 was performed. Patients treated with PTX combined with PAL served as study group (42 cases) and patients with conventional GC (gemcitabine plus cisplatin) chemotherapy regimen were the control group (40 cases). Changes in liver function indexes before and after treatment were observed, including alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), and total bilirubin (TBil). RT-qPCR was used for detection of relative expression levels of serum dihydrofolate reductase (DHFR) and vascular endothelial growth factor (VEGF) before and after treatment in the two groups. The clinical efficacy after treatment and adverse reactions during treatment were observed in the two groups. There was no significant difference in the clinical remission rate (RR) nor in the serum ALT, AST, ALP and TBil levels between the study and the control groups (P>0.05). Concentrations of serum ALT, AST, ALP and TBil were significantly higher than those before treatment in both groups (P<0.05). Serum ALT, AST, ALP and TBil concentrations in study group were significantly lower than those in control group (P<0.05). There was no significant difference in the incidence of thrombocytopenia and leukopenia between the two groups (P>0.05). There was no significant difference in relative expression levels of serum DHFR mRNA and VEGF mRNA before treatment between the study and control groups (P>0.05). Those after treatment were significantly lower than those before treatment in both groups (P<0.05), and those after treatment in study group were significantly lower than those in control group (P<0.05). PTX combined with PAL can reduce adverse reactions of nausea and vomiting and liver function impairment during treatment and suppress tumor neovascularization. This is achieved possibly by inhibiting expression levels of DHFR and VEGF, thereby killing cancer cells. PTX combined with PAL may become a new method for the treatment of bladder cancer patients. DHFR and VEGF are expected to become novel therapeutic targets for the treatment of bladder cancer.

Stachydrine protects eNOS uncoupling and ameliorates endothelial dysfunction induced by homocysteine

BackgroundHyperhomocysteinemia (HHcy) is an independent risk factor for cardiovascular diseases (CVDs). Stachydrine (STA) is an active component in Chinese motherwort Leonurus heterophyllus sweet, which has been widely used for gynecological and cardiovascular disorders. This study is aimed to examine the effects of STA on homocysteine (Hcy)-induced endothelial dysfunction.MethodsThe effects of STA on vascular relaxation in rat thoracic aortas (TA), mesenteric arteries (MA) and renal arteries (RA) were measured by using Multi Myograph System. The levels of nitric oxide (NO), tetrahydrobiopterin (BH4) and guanosine 3′, 5′ cyclic monophosphate (cGMP) were determined. Endothelial nitric oxide synthase (eNOS) dimers and monomers were assayed by using Western blotting. GTP cyclohydrolase 1 (GTPCH1) and dihydrofolate reductase (DHFR) expressions were measured by using quantitative reverse transcriptase-PCR (qRT-PCR) and Western blotting.ResultsSTA effectively blocked Hcy-induced impairment of endothelium-dependent vasorelaxation in rat TA, MA and RA. STA-elicited arterial relaxations were reduced by NOS inhibitor NG-nitro-L-arginine methyl ester (L-NAME) or the NO-sensitive guanylyl cyclase inhibitor 1H- [1, 2, 4] Oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), but not by inducible iNOS inhibitor 1400 W nor the nonselective COX inhibitor indomethacin. Hcy caused eNOS uncoupling and decreases in NO, cGMP and BH4, which were attenuated by STA. Moreover, STA prevented decreases of GTPCH1 and DHFR levels in Hcy-treated BAECs.ConclusionWe demonstrated that STA effectively reversed the Hcy-induced endothelial dysfunction and prevented eNOS uncoupling by increasing the expression of GTPCH1 and DHFR. These results revealed a novel mechanism by which STA exerts its beneficial vascular effects.

A-to-I RNA Editing Up-regulates Human Dihydrofolate Reductase in Breast Cancer

Dihydrofolate reductase (DHFR) plays a key role in folate metabolism and is a target molecule of methotrexate. An increase in the cellular expression level of DHFR is one of the mechanisms of tumor resistance to methotrexate. The present study investigated the possibility that adenosine-to-inosine RNA editing, which causes nucleotide conversion by adenosine deaminase acting on RNA (ADAR) enzymes, might modulate DHFR expression. In human breast adenocarcinoma-derived MCF-7 cells, 26 RNA editing sites were identified in the 3'-UTR of DHFR. Knockdown of ADAR1 decreased the RNA editing levels of DHFR and resulted in a decrease in the DHFR mRNA and protein levels, indicating that ADAR1 up-regulates DHFR expression. Using a computational analysis, miR-25-3p and miR-125a-3p were predicted to bind to the non-edited 3'-UTR of DHFR but not to the edited sequence. The decrease in DHFR expression by the knockdown of ADAR1 was restored by transfection of antisense oligonucleotides for these miRNAs, suggesting that RNA editing mediated up-regulation of DHFR requires the function of these miRNAs. Interestingly, we observed that the knockdown of ADAR1 decreased cell viability and increased the sensitivity of MCF-7 cells to methotrexate. ADAR1 expression levels and the RNA editing levels in the 3'-UTR of DHFR in breast cancer tissues were higher than those in adjacent normal tissues. Collectively, the present study demonstrated that ADAR1 positively regulates the expression of DHFR by editing the miR-25-3p and miR-125a-3p binding sites in the 3'-UTR of DHFR, enhancing cellular proliferation and resistance to methotrexate.

Assessment of Folic Acid Supplementation in Pregnant Women by Estimation of Serum Levels of Tetrahydrofolic Acid, Dihydrofolate Reductase, and Homocysteine.

Background. Status of folic acid use in pregnant women of the hilly regions in North India was little known. This study was carried out to assess the folic acid use and estimate folate metabolites in pregnant women of this region. Materials and Methods. This cross-sectional study is comprised of 76 pregnant women, whose folic acid supplementation was assessed by a questionnaire and serum levels of homocysteine, tetrahydrofolic acid (THFA), and dihydrofolate reductase (DHFR) were estimated using Enzyme Linked Immunoassays. Results. The study data revealed awareness of folic acid use during pregnancy was present in 46.1% and 23.7% were taking folic acid supplements. The study depicted that there was no statistically significant difference between serum levels of THFA and DHFR in pregnant women with and without folic acid supplements (p = 0.790). Hyperhomocysteinemia was present in 15.78% of the participants. Conclusion. Less awareness about folic acid supplementation and low use of folic acid by pregnant women were observed in this region. Sufficient dietary ingestion may suffice for the escalated requirements in pregnancy, but since this cannot be ensured, hence folic acid supplementation should be made as an integral part of education and reproductive health programs for its better metabolic use, growth, and development of fetus.

Folic Acid Promotes Recycling of Tetrahydrobiopterin and Protects Against Hypoxia-Induced Pulmonary Hypertension by Recoupling Endothelial Nitric Oxide Synthase.

Nitric oxide (NO) derived from endothelial NO synthase (eNOS) has been implicated in the adaptive response to hypoxia. An imbalance between 5,6,7,8-tetrahydrobiopterin (BH4) and 7,8-dihydrobiopterin (BH2) can result in eNOS uncoupling and the generation of superoxide instead of NO. Dihydrofolate reductase (DHFR) can recycle BH2 to BH4, leading to eNOS recoupling. However, the role of DHFR and eNOS recoupling in the response to hypoxia is not well understood. We hypothesized that increasing the capacity to recycle BH4 from BH2 would improve NO bioavailability as well as pulmonary vascular remodeling (PVR) and right ventricular hypertrophy (RVH) as indicators of pulmonary hypertension (PH) under hypoxic conditions. In human pulmonary artery endothelial cells and murine pulmonary arteries exposed to hypoxia, eNOS was uncoupled as indicated by reduced superoxide production in the presence of the nitric oxide synthase inhibitor, L-(G)-nitro-L-arginine methyl ester (L-NAME). Concomitantly, NO levels, BH4 availability, and expression of DHFR were diminished under hypoxia. Application of folic acid (FA) restored DHFR levels, NO bioavailability, and BH4 levels under hypoxia. Importantly, FA prevented the development of hypoxia-induced PVR, right ventricular pressure increase, and RVH. FA-induced upregulation of DHFR recouples eNOS under hypoxia by improving BH4 recycling, thus preventing hypoxia-induced PH. FA might serve as a novel therapeutic option combating PH.

Pre-Clinical Analysis Of The Novel Antifolate Pralatrexate In Multiple Myeloma Reveals Functional Biomarkers Correlated With Response

Multiple myeloma (MM) is a neoplasia of plasma cells and is the second most common hematologic malignancy. Current combination therapies for MM typically include proteasome inhibitors (PIs) and/or immunomodulatory drugs (ImiDs). Although these regimens are effective, relapse and resistance to these agents are inevitable. There is a need to develop new classes of drugs with activity against MM and to identify biomarkers associated with response to these agents, in order to tailor salvage therapy for individuals most likely to respond and minimize exposure to therapies that are unlikely to be of benefit. We investigated these principles with the novel antifolate pralatrexate (PDX) in laboratory models of MM. Antifolates such as methotrexate (MTX) are not commonly used in the treatment of MM; however, combination chemotherapy regimens containing MTX have demonstrated clinical efficacy. In addition, case reports of the application of intrathecal MTX have shown activity against MM in the central nervous system. PDX was designed to be a preferred substrate for the reduced folate carrier (RFC) and folylpolyglutamate synthetase (FPGS) as compared to MTX, and it is approved for the treatment of peripheral T cell lymphoma. PDX induced intrinsic apoptosis with greater potency than MTX in a subset of human myeloma cell lines (HMCLs). Interestingly, other HMCLs were resistance to antifolate-induced apoptosis. This dichotomy among HMCLs provided a platform to identify functional biomarkers associated with sensitivity or resistance to PDX-induced apoptosis. We examined expression of the genes that are determinants of antifolate actions: RFC, FPGS, gamma-glutamyl hydrolase (GGH), and dihydrofolate reductase (DHFR) in sensitive and resistant HMCLs. Higher pre-treatment levels of RFC mRNA by qRT-PCR correlated with increased sensitivity to PDX and higher rates of RFC-mediated transport. We then quantified mRNA for folate metabolism genes by qRT-PCR in total RNA from CD138-selected MM cells from patients and detected a broad range of expression for RFC, indicating that further studies with primary MM cells are warranted to assess RFC expression as a biomarker of antifolate sensitivity. Interestingly, PDX-resistant HMCLs also demonstrated dose-dependent increases in DHFR protein, one of the major antifolate targets, after treatment whereas PDX-sensitive HMCLs did not. Messenger RNA expression was unchanged under these conditions, suggesting a translational or post-translational mechanism for this activity. Sensitivity to PDX-induced apoptosis was not suppressed by co-incubation with recombinant human interleukin-6 or by co-culture with HS-5 bone marrow stromal cells. Finally, we used a previously validated bioluminescent xenograft mouse model to examine the effects of PDX in vivo. PDX-sensitive MM.1s cells stably-transduced with a dual cassette construct expressing both green fluorescent protein (GFP) and luciferase were introduced by tail-vein injection into NOD/Shi-scid/IL-2Rγnull (NOG) mice. These cells engrafted in the marrow of the femur, pelvis, vertebral bodies, and sternum, recapitulating human disease, and tumor burden was quantified by in vivo imaging after luciferin injection. PDX treated mice demonstrated reductions in tumor burden compared to vehicle treated controls. These results demonstrate that the novel antifolate PDX has potent activity against a subset of HMCLs in vitro and in vivo. Baseline mRNA expression of RFC and post-treatment protein levels of DHFR correlated with response in HMCLs. These findings support further clinical studies to assess the potential role of PDX in the treatment of MM coupled with correlative studies to validate the clinical utility of the biomarkers identified in HMCLs. PDX may be an effective addition to individualized therapy for relapsed multiple myeloma. Disclosures: O'Connor: Spectrum Pharmaceuticals: Membership on an entity’s Board of Directors or advisory committees; Allos Pharmaceuticals: Consultancy.

Increase in tetrahydrobiopterin concentration with aging in the cerebral cortex of the senescence-accelerated mouse prone 10 strain caused by abnormal regulation of tetrahydrobiopterin biosynthesis

6R-L-Erythro-5,6,7,8-tetrahydrobiopterin (BH4) is an essential cofactor for tyrosine hydroxylase (TH) activity and is a risk factor for cognitive decline and brain atrophy. Previous studies have shown that the decline in TH activity in the cerebral cortex of senescence-accelerated mouse prone 10 (SAMP10) mice is caused, at least in part, by a decrease in Fe, ferritin, and TH phosphorylation. We determined the concentrations of BH4 and the enzymes GTP cyclohydrolase-1,6-pyruvoyltetrahydropterin synthase and sepiapterin reductase (SPR) in the de novo pathway of BH4 biosynthesis. Dihydrofolate reductase (DHFR), which converts BH2 to BH4 in the salvage pathway of BH4 synthesis was also determined in the cerebral cortex of SAM mice at 3 and 12months of age. The BH4 concentration was measured by HPLC, and the protein levels of enzymes involved in BH4 synthesis were measured by western blot analysis. At 12months of age, BH4 concentration in the cerebral cortex of SAMP10 mice showed significantly higher values as compared to that of control mice. Further, the protein level of SPR in SAMP10 mice was significantly higher than that in SAMR1 mice at 3 and 12months of age. In contrast to SPR, the protein level of DHFR in SAMP10 mice was significantly lower than that in SAMR1 mice. These results indicate that abnormal regulation of BH4 metabolism occurs in the cerebral cortex of SAMP10 where the dysfunction of the salvage pathway of BH4 synthesis may cause overproduction of BH4 through the de novo pathway, which is considered characteristic in the cerebral cortex of SAMP10 with aging. Therefore, there is a possibility that the excess amounts of BH4 lead to age-related brain dysfunction in the cerebral cortex of SAMP10.

Correlation study between DHFR enzyme and some biochemical parameters in diabetic type II patients

Dihydrofolatereductase (DHFR)enzyme , Fasting Blood Sugar and some biochemical parameters were determined in (88) sample, (20) the control group which(10 males & 10 females) & (68) the patients(24 male &44 female) how were out-patient clinic in Baghdad hospital and had diabetic type II. There are significant differences in mean value between patient (male ,female) group and control group in FBG, urea, TG chol. HDL, creatinine, Na & K , while there is significant difference in mean value of ALP between patient group & control group and mean value of chloride between patient group & control group and there are highly significant differences in mean value between patient group and control group in ALT & AST. There was correlation between the DHFR and FBG,ALP, chl. TG in male patients and positive non significant between DHFR and ALT, AST. DHFR levels were negative significant correlated with urea HDL, Creat. Na but non- significant with K but the correlation was in female patients between the DHFR and FBG, ALP, Chl., TG, AST and positive non significant between DHFR and ALT. DHFR levels were negative significant correlated with Na but non- significant with urea,HDL,Creat. and K.

The Emerging Role of Unmetabolized Folic Acid in Human Diseases: Myth or Reality?

An increase in folate intake before and during pregnancy can prevent many neural tube defects. This prompted over 50 countries worldwide to mandate fortification of breakfast cereals or staple foods with folic acid (FA), which is the synthetic oxidised form of the vitamin used in supplements and fortified foods. After ingestion, FA is reduced by dihydrofolate reductase (DHFR) and then converted to the biologically active forms. The presence of detectable amounts of unmetabolised FA in blood of individuals who have consumed supplements or fortified foods has attracted attention in recent years. A direct correlation exists between FA intake and unmetabolised FA in serum and suggests that a saturable level of DHFR exists. Factors affecting FA reduction, such as age, intestinal pH, alcohol, FA dose and duration of supplement usage, and possibly polymorphisms of folate-metabolising enzymes, can affect the presence of FA in blood. However, minor amounts of FA might also be produced during sample preparation. In pregnant women taking supplements, FA does not seem to accumulate in the newborns. Concentrations of unmetabolized FA are correlated to and predicted by those of total folate or 5-MTHF. Evidence of a negative health effect of free FA in blood is not consistent and suggests rather artificial factors. FA has no known cofactor function that would increase the likelihood of a causal role for free FA in disease development.

High-throughput Screening and Sensitized Bacteria Identify an M. tuberculosis Dihydrofolate Reductase Inhibitor with Whole Cell Activity

Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis, is a bacterial pathogen that claims roughly 1.4 million lives every year. Current drug regimens are inefficient at clearing infection, requiring at least 6 months of chemotherapy, and resistance to existing agents is rising. There is an urgent need for new drugs that are more effective and faster acting. The folate pathway has been successfully targeted in other pathogens and diseases, but has not yielded a lead drug against tuberculosis. We developed a high-throughput screening assay against Mtb dihydrofolate reductase (DHFR), a critical enzyme in the folate pathway, and screened a library consisting of 32,000 synthetic and natural product-derived compounds. One potent inhibitor containing a quinazoline ring was identified. This compound was active against the wild-type laboratory strain H37Rv (MIC99 = 207 µM). In addition, an Mtb strain with artificially lowered DHFR levels showed increased sensitivity to this compound (MIC99 = 70.7 µM), supporting that the inhibition was target-specific. Our results demonstrate the potential to identify Mtb DHFR inhibitors with activity against whole cells, and indicate the power of using a recombinant strain of Mtb expressing lower levels of DHFR to facilitate the discovery of antimycobacterial agents. With these new tools, we highlight the folate pathway as a potential target for new drugs to combat the tuberculosis epidemic.

Insulin‐like growth factor‐1 receptor inhibitor, AMG‐479, in cetuximab‐refractory head and neck squamous cell carcinoma

Recurrent head and neck squamous cell carcinoma (HNSCC) remains a difficult cancer to treat. Here, we describe a patient with HNSCC who had complete response to methotrexate (MTX) after progressing on multiple cytotoxic agents, cetuximab, and AMG-479 (monoclonal antibody against insulin-like growth factor-1 receptor [IGF-1R]). The clinical information was collected by a retrospective medical record review under an Institutional Review Board-approved protocol. From 4 tumors and 2 normal mucosal epithelia, global gene expression, and IGF-1R and dihydrofolate reductase (DHFR) protein levels were determined. Effective target inhibition in the tumor was confirmed by the decreased protein levels of total and phospho-IGF-1R after treatment with AMG-479. Decreased level of DHFR and conversion of a gene expression profile associated with cetuximab-resistance to cetuximab-sensitivity were also observed. This suggests that the combination of AMG-479 and MTX or cetuximab may be a promising therapeutic approach in refractory HNSCC.