Folylpolyglutamate Synthetase Research Articles

A comprehensive review of synthesized derivatives of methotrexate in relation to their anticancer potential.

Methotrexate (MTX) is a chemotherapeutic agent with certain side effects. Efforts were made to synthesize analogues of MTX to enhance the activity and reduce side effects. Various derivatives were synthesized by structural modification of parent drug and mainly assayed for anticancer activity and binding affinity with dihydrofolatereductase (DHFR) and folylpolyglutamate synthetase (FPGS). In vitro study was carried out on cell lines CCRF. CEM, ATCC8, L. Casei, P388, L1210, L1210/R81, and H35. These synthesized derivatives have been assayed for human squamous cell carcinoma namely SSC25, SSC68, SSC78, SSC25/R1, SSC68/R1, and SSC78/R1. Some modification proved to enhance anticancer activity while others are detrimental. Some of derivatives were also tested for other biological activity like anti-malarial, anti-bacterial and anti-diabetic and show better activity. This article deals with a comprehensive overview of the synthesized derivatives by structural modifications and the impact of these modifications on its activity.

Histone deacetylase inhibition enhances the therapeutic effects of methotrexate on primary central nervous system lymphoma.

BackgroundPolyglutamylation is a reversible protein modification that commonly occurs in tumor cells. Methotrexate (MTX) in tumor cells is polyglutamylated and strongly binds to dihydrofolate reductase (DHFR) without competitive inhibition by leucovorin. Therefore, tumor cells with high polyglutamylation levels are supposed to be selectively killed, whereas normal cells with lower polyglutamylation are rescued by leucovorin. This study investigated the combined effects of MTX plus histone deacetylase inhibitors (HDACIs), which upregulate MTX polyglutamylation, in primary central nervous system lymphoma (PCNSL).MethodsWe evaluated cell viability after MTX treatment and leucovorin rescue and compared the expression of folylpolyglutamate synthetase (FPGS), γ-glutamyl hydrolase (GGH), and DHFR in 2 human PCNSL-derived cell lines (HKBML and TK) and a human Burkitt lymphoma cell line (TL-1). Combination treatments were created using 4 HDACIs: panobinostat, vorinostat, sodium butyrate, and valproic acid. The expression of DHFR was examined as well as ratios of FPGS/GGH expression. The combined effects of MTX plus HDACIs were evaluated using a cell viability assay, mass spectroscopy imaging, and subcutaneous and intracranial xenograft models.ResultsHDACIs upregulated the ratio of FPGS/GGH expression resulting in increased polyglutamylation of MTX, but also downregulated expression of the target molecule of MTX: DHFR. The combination of MTX and vorinostat decreased cell viability in vitro (P < .05) and tumor volumes in a subcutaneous model (P < .0001), and prolonged survival in an intracranial model (P < .01), relative to controls.ConclusionHDACIs enhanced the therapeutic effect of MTX through increased polyglutamylation of MTX and concomitant downregulation of DHFR expression.

Glutamic Acid Increased Methotrexate Polyglutamation and Cytotoxicity in a CCRF-SB Acute Lymphoblastic Leukemia Cell Line.

Background and Objectives: Acute lymphoblastic leukemia (ALL) is the most common type of cancer in childhood. The majority of patients respond to treatment, but those with resistant phenotypes suffer relapse or death. The antifolate methotrexate (MTX) is the most commonly used drug against ALL due to its efficacy. Once inside leukemic cells, MTX is metabolized into methotrexate polyglutamates (MTX-PG) by action of the enzyme folylpolyglutamate synthetase (FPGS), leading to a longer action compared to that of MTX alone. Materials and Methods: In this work, we demonstrated that the combination treatment of methotrexate and 5 and 10 mM glutamic acid could enhance methotrexate cytotoxicity in CCRF-SB (B-ALL) cells. In addition, MTX plus 20 mM glutamic acid was able to improve the synthesis of MTX-PG5. Results: All treatments induced an increase in FPGS expression compared to that of the control group. Furthermore, we detected different cellular expression patterns of FPGS in the different treatments. Conclusion: Based on these findings, we demonstrated that levels of methotrexate polyglutamates (MTX-PGs) could be a key determinant of methotrexate-induced cytotoxicity in CCRF-SB acute lymphoblastic leukemia cells.

High gamma-glutamyl hydrolase and low folylpolyglutamate synthetase expression as prognostic biomarkers in patients with locally advanced gastric cancer who were administrated postoperative adjuvant chemotherapy with S-1

PurposeThe enzymes gamma-glutamyl hydrolase (GGH) and folylpolyglutamate synthetase (FPGS) regulate intracellular folate concentrations needed for cell proliferation, DNA synthesis, and repair. High GGH expression affects 5-FU thymidylate synthase (TS) inhibition and is a risk factor for various malignancies. Here, the clinical significance of GGH and FPGS expression was investigated in Stage II/III gastric cancer patients undergoing postoperative adjuvant chemotherapy with S-1.MethodsSurgical specimens of cancer tissue and adjacent normal mucosa, obtained from 253 patients with previously untreated gastric cancer, were examined. GGH and FPGS mRNA expression was measured by qPCR to evaluate their clinicopathological significance in gastric cancer patients after curative resection.ResultsWhile FPGS expression showed no significant differences between the cancerous and normal samples, GGH expression was higher in cancer tissue than in adjacent normal mucosa. High GGH expression was correlated with age, histological type, and vascular invasion. Overall survival (OS) of patients with high GGH mRNA expression was significantly poorer than of patients with low GGH expression. Multivariate analysis showed that high GGH expression was an independent prognostic factor of OS (HR: 2.58, 95% CI 1.29–5.16). Patients who received S-1 adjuvant treatment showed a significantly poor OS between high GGH/low FPGS and low GGH/high FPGS. Patients without adjuvant treatment showed no significant difference.ConclusionGGH expression was significantly higher in gastric cancer tissue than in adjacent normal mucosa. High GGH and low FPGS expression is a useful independent predictor of poor outcomes in stage II/III gastric cancer patients undergoing postoperative adjuvant chemotherapy with S-1.

Inactivation of folylpolyglutamate synthetase Met7 results in genome instability driven by an increased dUTP/dTTP ratio.

The accumulation of mutations is frequently associated with alterations in gene function leading to the onset of diseases, including cancer. Aiming to find novel genes that contribute to the stability of the genome, we screened the Saccharomyces cerevisiae deletion collection for increased mutator phenotypes. Among the identified genes, we discovered MET7, which encodes folylpolyglutamate synthetase (FPGS), an enzyme that facilitates several folate-dependent reactions including the synthesis of purines, thymidylate (dTMP) and DNA methylation. Here, we found that Met7-deficient strains show elevated mutation rates, but also increased levels of endogenous DNA damage resulting in gross chromosomal rearrangements (GCRs). Quantification of deoxyribonucleotide (dNTP) pools in cell extracts from met7Δ mutant revealed reductions in dTTP and dGTP that cause a constitutively active DNA damage checkpoint. In addition, we found that the absence of Met7 leads to dUTP accumulation, at levels that allowed its detection in yeast extracts for the first time. Consequently, a high dUTP/dTTP ratio promotes uracil incorporation into DNA, followed by futile repair cycles that compromise both mitochondrial and nuclear DNA integrity. In summary, this work highlights the importance of folate polyglutamylation in the maintenance of nucleotide homeostasis and genome stability.

Development and Validation of a Sensitive UHPLC-MS/MS-Based Method for the Analysis of Folylpolyglutamate Synthetase Enzymatic Activity in Peripheral Blood Mononuclear Cells: Application in Rheumatoid Arthritis and Leukemia Patients.

Folylpolyglutamate synthetase (FPGS) is a crucial enzyme in both cellular folate homeostasis and the intracellular retention of folate analogue drugs such as methotrexate (MTX), which is commonly used for the treatment of (pediatric) leukemia and the anchor drug in rheumatoid arthritis (RA) treatment. To date, assessment of FPGS catalytic activity relies on assays using radioactive substrates that are labor-intensive and require relatively large numbers of cells. Here, we describe a nonradioactive, ultra-high-performance liquid chromatography-tandem mass spectrometer (UHPLC-MS/MS)-based method allowing for sensitive and accurate measurements of FPGS activity in low cell numbers (ie, 1-2 × 10) of biological specimens, including leukemic blast cells of acute lymphoblastic leukemia patients and peripheral blood mononuclear cells of patients with RA. The UHPLC-MS/MS assay was validated with 2 CCRF-CEM human leukemia cells, one proficient and one deficient in FPGS activity. Linearity of time and protein input were tested by measuring FPGS activity at 30-180 minutes of incubation time and 10-300 mcg protein extract. In addition, FPGS enzyme kinetic parameters were assessed. The FPGS enzymatic assay showed a linear relation between FPGS activity and protein input (R ≥ 0.989) as well as incubation time (R ≥ 0.996). Moreover, the UHPLC-MS/MS method also allowed for evaluation of FPGS enzyme kinetic parameters revealing Km values for the substrates MTX and L-glutamic acid of 64 µmol/L and 2.2 mmol/L, respectively. The mean FPGS activity of acute lymphoblastic leukemia blast cells (n = 4) was 3-fold higher than that of CCRF-CEM cells and 44-fold and 88-fold higher than that of peripheral blood mononuclear cells from MTX-naive (n = 9) and MTX-treated RA patients (n = 6), respectively. Collectively, given its sensitivity with low cell numbers and avoidance of radioactive substrates, UHPLC-MS/MS-based analysis of FPGS activity may be eligible for routine therapeutic drug monitoring of MTX in RA and leukemia for therapy (non)response evaluations.

Structural Analyses of Helicobacter Pylori FolC Conducting Glutamation in Folate Metabolism

FolC plays important roles in the folate metabolism of cells by attaching l-Glu to dihydropteroate (DHP) and folate, which are known activities of dihydrofolate synthetase (DHFS) and folylpolyglutamate synthetase (FPGS), respectively. Here, we determined the crystal structure of Helicobacter pylori FolC (HpFolC) at 1.95 Å resolution using the single-wavelength anomalous diffraction method. HpFolC has globular N- and C-terminal domains connected by a single loop, and a binding site for ATP is located between the two domains. Apo-HpFolC was crystallized in the presence of citrate in a crystallization solution, which was held in the ATP-binding site. Structural motifs such as the P-loop and Ω-loop of HpFolC for binding of ATP and two magnesium ions are well conserved in spite of the low overall sequence similarity to other FolC/FPGSs. The Ω-loop would also recognize a folate molecule, and the DHP-binding loop of HpFolC is expected to exhibit a unique recognition mode on DHP, compared with other FolCs. Because human FolC is known to only exhibit FPGS activity, the DHFS activity of bacterial FolC is an attractive target for the eradication of pathogenic bacteria. Consequently, our structural analyses of HpFolC provide a valuable foundation for a universal antibacterial strategy against H. pylori as well as other pathogenic bacteria.

Cell-type-specific sensitivity of bortezomib in the methotrexate-resistant primary central nervous system lymphoma cells.

Methotrexate (MTX) is used in first-line treatment of primary central nervous system lymphoma (PCNSL), but most cases result in relapse-acquired resistance to MTX. However, only few studies have reported on internal changes and chemotherapies in PCNSL. In this study, we generated two MTX-resistant PCNSL cell lines, designated MTX-HKBML and MTX-TK, in addition to a MTX-resistant Burkitt lymphoma cell line, designated MTX-RAJI. We examined gene expression changes and drug sensitivity to a proteasome inhibitor, bortezomib, in these cells. Cytotoxic tests revealed that the 50% inhibitory concentration for MTX in MTX-HKBML is markedly higher than that in the other two cell lines. Expression of the genes in MTX and folate metabolisms, including gamma-glutamyl hydrolase and dihydrofolate reductase, are upregulated in both MTX-HKBML and MTX-TK, whereas the gene expression of folylpolyglutamate synthetase, thymidylate synthase, and methylenetetrahydrofolate dehydrogenase 1 were upregulated and downregulated in MTX-HKBML and MTX-TK, respectively, on the other hand, bortezomib sensitivity was observed in MTX-TK, as compared with control TK, but not in MTX-HKBML. These results indicate the cell-type-specific changes downstream of metabolic pathways for MTX and folate, bortezomib sensitivity, and purine and pyrimidine syntheses, in each PCNSL cell line. The MTX-resistant lymphoma cell lines established may be useful for in vitro relapse models for MTX and development of salvage chemotherapy and drug discovery.

Pralatrexate-Resistant Cell Lines Show Intact Internalization Via RFC1 but Collateral Sensitivity to Nucleoside Analogs

BackgroundPralatrexate (PDX) is a novel dihydrofolate reductase (DHFR) inhibitor which is designed to have a high affinity for reduced folate carrier (RFC1), DHFR, and folylpolyglutamate synthetase (FPGS), resulting in greater internalization and accumulation in tumor cells than methotrexate. PDX has been approved by the U.S. FDA and many international health care ministries for the treatment of relapsed and refractory peripheral T-cell lymphoma (R/R PTCL). A recent case match control analysis has confirmed a survival advantage for patients enrolled on PROPEL compared to a well-matched population of patients receiving standard of care. Recently, PDX has demonstrated compelling activity in combination with romidepsin in R/R PTCL patients, where is role is likely to expand. In this study we explored the mechanisms of resistance to PDX and approaches to overcome them, including combination strategies using PDX-resistant (PDX-R) leukemic cell lines.MethodsT-lymphoblastic leukemia cell lines, CCRF-CEM (CEM), MOLT-4 (MOLT4), and MOLT-3 (MOLT3), were used. To establish PDX-R cell lines, the cells were initially incubated with low-concentrations of PDX, and then concentrations of the drug were gradually increased. After acquisition of PDX-R, the single-cell separation was performed by a limiting dilution. Microarray analysis was performed in CEM, MOLT4 and each PDX-R counterpart.ResultsThe 50% inhibitory concentration (IC50) values of PDX against CEM, MOLT4 and MOLT3 were 0.6 nM, 2.4 nM and 1.4 nM, respectively, while the PDX-R cell lines exhibited IC50 values of 20 nM, 80 nM and 40 nM, respectively. After 48-hour treatment with PDX, annexin-V positivity was significantly reduced in PDX-R cells (in CEM, MOLT4 and MOLT3 was 78.7%, 77.7%, 97.4% vs 4.4%, 5.9%, 6.6%, respectively). The expression of RFC1 was not altered in PDX-R cells, nor was any acquired mutation of RFC1 detected in cell lines. Intracellular uptake of [14C]-PDX was modestly decreased in CEM/PDX-R, while there was no difference of it in MOLT4/PDX-R, suggesting that the resistance mechanism was not due to the inability to internalize drug. Gene expression array revealed that the expression of DNA-methyltransferase 3 beta (DNMT3b) was significantly elevated in both CEM/PDX-R (12.8 times) and MOLT4/PDX-R (2.8 times) cells, whereas there was no significant difference in that of DHFR, FPGS and thymidylate synthase. When we explored the profile of cross-resistances in PDX-R cells, it was surprising that PDX-R cells were more sensitive to nucleoside analogs, including cytarabine (AraC) and forodesine (FDS). After 72 hours of FDS-treatment, induction of apoptosis was seen in both parental and PDX-R cells, suggesting that the mechanisms of PDX-R is not cross resistant. In addition, there was no cross-resistance to bortezomib or panobinostat in PDX-R cell lines.DiscussionWe established PDX-R cell lines which were around 30-fold resistant to PDX compared to their parental counterparts. The characteristics of PDX-R cells are as follows: (i) intact internalization of PDX, (ii) intact apoptotic mechanisms, (iii) no cross-resistance to BOR or LBH, (iv) collateral sensitive to nucleoside analogs, such as AraC and FDS. These data suggest that the mechanism of acquired resistance to PDX may be associate with not only cellular uptake of PDX, but also DNA methylation and/or nucleic-acid metabolism. These findings may be underscored by the fact that nucleoside analogs exhibited greater potency in the PDX-R cells in vitro. Next steps are focused on exploring the methylation status of these genes involved in PDX activity, and their merits of combining with hypomethylating agents.ConclusionsWe established PDX-R T-lymphoblastic leukemia cell lines which show collateral sensitivity to nucleoside analogs. The mechanisms of PDX resistance is not always cellular uptake of PDX, epigenetic alteration might contribute to the development PDX-resistance. Nevertheless, the new T-lymphoma-targeting agent, FDS can be effective in this setting. Our results may encourage further investigation to overcome resistance of PDX for patients with R/R PTCL. DisclosuresO'Connor:ADC Therapeutics: Research Funding; Seattle Genetics: Research Funding; Celgene: Research Funding.

Genome-wide screening of potential RNase Y-processed mRNAs in the M49 serotype Streptococcus pyogenes NZ131.

RNase Y is a major endoribonuclease in Group A streptococcus (GAS) and other Gram‐positive bacteria. Our previous study showed that RNase Y was involved in mRNA degradation and processing in GAS. We hypothesized that mRNA processing regulated the expression of important GAS virulence factors via altering their mRNA stabilities and that RNase Y mediated at least some of the mRNA‐processing events. The aims of this study were to (1) identify mRNAs that were processed by RNase Y and (2) confirm the mRNA‐processing events. The transcriptomes of Streptococcus pyogenes NZ131 wild type and its RNase Y mutant (Δrny) were examined with RNA‐seq. The data were further analyzed to define GAS operons. The mRNA stabilities of the wild type and Δrny at subgene level were determined with tiling array analysis. Operons displaying segmental stability in the wild type but not in the Δrny were predicted to be RNase Y processed. Overall 865 operons were defined and their boundaries predicted. Further analysis narrowed down 15 mRNAs potentially processed by RNase Y. A selection of four candidates including folC1 (folylpolyglutamate synthetase), prtF (fibronectin‐binding protein), speG (streptococcal exotoxin G), ropB (transcriptional regulator of speB), and ypaA (riboflavin transporter) mRNAs was examined with Northern blot analysis. However, only folC1 was confirmed to be processed, but it is unlikely that RNase Y is responsible. We conclude that GAS use RNase Y to selectively process mRNA, but the overall impact is confined to selected virulence factors.

A transcriptomics approach uncovers novel roles for poly(ADP-ribosyl)ation in the basal defense response in Arabidopsis thaliana.

Pharmacological inhibition of poly(ADP-ribose) polymerase (PARP) or loss of Arabidopsis thaliana PARG1 (poly(ADP-ribose) glycohydrolase) disrupt a subset of plant defenses. In the present study we examined the impact of altered poly(ADP-ribosyl)ation on early gene expression induced by the microbe-associate molecular patterns (MAMPs) flagellin (flg22) and EF-Tu (elf18). Stringent statistical analyses and filtering identified 178 genes having MAMP-induced mRNA abundance patterns that were altered by either PARP inhibitor 3-aminobenzamide (3AB) or PARG1 knockout. From the identified set of 178 genes, over fifty Arabidopsis T-DNA insertion lines were chosen and screened for altered basal defense responses. Subtle alterations in callose deposition and/or seedling growth in response to those MAMPs were observed in knockouts of At3g55630 (FPGS3, a cytosolic folylpolyglutamate synthetase), At5g15660 (containing an F-box domain), At1g47370 (a TIR-X (Toll-Interleukin Receptor domain)), and At5g64060 (a predicted pectin methylesterase inhibitor). Over-represented GO terms for the gene expression study included "innate immune response" for elf18/parg1, highlighting a subset of elf18-activated defense-associated genes whose expression is altered in parg1 plants. The study also allowed a tightly controlled comparison of early mRNA abundance responses to flg22 and elf18 in wild-type Arabidopsis, which revealed many differences. The PARP inhibitor 3-methoxybenzamide (3MB) was also used in the gene expression profiling, but pleiotropic impacts of this inhibitor were observed. This transcriptomics study revealed targets for further dissection of MAMP-induced plant immune responses, impacts of PARP inhibitors, and the molecular mechanisms by which poly(ADP-ribosyl)ation regulates plant responses to MAMPs.

Impact of Genetic Variants of ATP Binding Cassette B1, AICAR Transformylase/IMP Cyclohydrolase, Folyl-polyglutamate Synthetase, and Methylenetetrahydrofolate Reductase on Methotrexate Toxicity

ObjectiveTo analyze the effect of single nucleotide polymorphisms (SNPs) with well-known functional impact of methylenetetrahydrofolate reductase (MTHFR; rs1801131 and rs1801133), the membrane transporter ABCB1 (rs1045642), the AICAR transformylase/IMP cyclohydrolase (ATIC; rs2372536) and folyl-polyglutamate synthetase (FPGS; rs1544105), on liver and bone marrow toxicity of methotrexate (MTX). Patients and methodsWe analyzed 1415 visits from 350 patients of the PEARL (Princesa Early Arthritis Register Longitudinal) study: (732 with MTX, 683 without MTX). The different SNPs were genotyped using specific TaqMan probes (Applied Biosystems). Multivariate analyzes were performed using generalized linear models in which the dependent variables were the levels of serum alanine aminotransferase (liver toxicity), leukocytes, platelets or hemoglobin (hematologic toxicity) and adjusted for clinical variables (disease activity, etc.), analytical (renal function, etc.), sociodemographic (age, sex, etc.) and genetic variants of MTHFR, ABCB1, ATIC and FPGS. The effect of these variables on the MTX doses prescribed throughout follow-up was also analyzed through multivariate analysis nested by visit and patient. ResultsWhen taking MTX, those patients carrying the CC genotype of rs1045642 in ABCB1 showed significantly higher GPT levels (7.1±2.0U/L; P<.001). Carrying at least one G allele of rs1544105 in FPGS was associated with lower leukocyte (−0.67±0.32; 0.038), hemoglobin (−0.34±0.11g/dL; P=.002), and platelet (−11.8±4.7; P=.012) levels. The presence of the G allele of rs1544105 in FPGS, and the T allele of rs1801133 in MTHFR, was significantly associated with the use of lower doses of MTX. DiscussionOur data suggest that genotyping functional variants in FGPS and MTHFR enzymes and the transporter ABCB1 could help to identify patients with increased risk of MTX toxicity.

Abstract 4870: Mutational landscape and timing of resistant clone emergence in 104 Chinese pediatric patients with relapsed acute lymphoblastic leukemia

Abstract Relapsed pediatric acute lympoblastic leukemia (ALL), occurring in 15-20% of cases, is one of the leading causes of cancer-related death in children, conferring a dismal survival rate of less than 40% primarily due to drug resistance. We performed whole-genome sequencing (WGS) and RNA-seq of matched diagnosis and relapse tumors as well as WGS of remission DNA from 104 pediatric ALL patients treated at Shanghai Children’s Medical Center (n=89), Institute of Hematology &amp; Blood Disease Hospital in Tianjin (n=14) and the Second Hospital of Anhui Medical University (n=1) between 2003 and 2014. The median age at diagnosis was 6.29 (range, 0.23-16.05) years. Relapse occurred during chemotherapy in 85 patients and after completion of therapy in 19 patients. Somatic mutation rate in ALL increased significantly from an average of 0.23 per Mb at diagnosis to 0.65 per Mb at relapse. We identified 34 potential driver genes at diagnosis and 45 at relapse based on significance of mutation recurrence and pathogenicity. The four most significant relapse-specific driver genes harbor known point mutations on purine metabolism genes NT5C2 (n=13) and PRPS1/PRPS2 (n=7), novel alterations affecting glucocorticoids receptor NR3C1 (n=13) and folylpolyglutamate synthetase FPGS (n=8). Functional characterization showed that all NR3C1 mutations resulted in significant loss of transcription activator function and subcellular mislocalization. Ectopic expression of mutant NR3C1 in ALL cell lines consistently led to prednisone resistance. Five driver genes (TP53, CREBBP, SMARCA4, WHSC1 and NIPBL) showed the highest increase (2-5 fold) of mutation frequency from diagnosis to relapse with mutations collectively present in 28% of relapsed ALL. Truncation mutations in DNA mismatch repair genes MLH1, MSH2, MSH6 and PMS2 occurred exclusively at relapse in four ALL with the highest mutation burden. Targeted ultra-deep sequencing at 5,000X of 268 somatic alterations was performed on 214 serial bone-marrow samples collected during ALL therapy for 17 cases. The resulting mutant allele fraction (MAF) values showed high concordance with minimum residual disease (MRD) measured by flow cytometry, indicating suitability for quantifying leukemia burden. Temporal change of MAF in the serial samples also allows us to track clonal identity and emergence of drug-resistant clones during and after therapy. For example, one case had deep sequencing performed on 11 somatic lesions from 10 bone barrow samples collected during the 15 months between diagnosis and relapse. We found that a minor clone present in 0.5-1% of ALL blasts at diagnosis emerged five months prior to relapse, from which two new subclones arose harboring NT5C2 mutations L406&amp;gt;SSF and D407&amp;gt;DRD. Preliminary data generated from serial bone marrow samples provides the first insight into the use of somatic alterations for monitoring leukemia progress during relapse. Citation Format: Benshang Li, Yongjin Li, Shuhong Shen, Xiaofan Zhu, Xiaotu Ma, Ningling Wang, Yanling Liu, Yu Liu, Hui Zhang, Ting-Nien Lin, Michael Rusch, Michael Edmonson, John Easton, Yingchi Zhang, Jingliao Zhang, Cheng Cheng, Jingyan Tang, James R. Downing, Ching-Hon Pui, Jun J. Yang, Jinghui Zhang. Mutational landscape and timing of resistant clone emergence in 104 Chinese pediatric patients with relapsed acute lymphoblastic leukemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4870. doi:10.1158/1538-7445.AM2017-4870

Plastidial Folate Prevents Starch Biosynthesis Triggered by Sugar Influx into Non-Photosynthetic Plastids of Arabidopsis.

Regulation of sucrose–starch interconversion in plants is important to maintain energy supplies necessary for viability and growth. Arabidopsis mutants were screened for aberrant responses to sucrose to identify candidates with a defect in the regulation of starch biosynthesis. One such mutant, fpgs1-4, accumulated substantial amounts of starch in non-photosynthetic cells. Dark-grown mutant seedlings exhibited shortened hypocotyls and accumulated starch in etioplasts when supplied with exogenous sucrose/glucose. Similar starch accumulation from exogenous sucrose was observed in mutant chloroplasts, when photosynthesis was prevented by organ culture in darkness. Molecular genetic analyses revealed that the mutant was defective in plastidial folylpolyglutamate synthetase, one of the enzymes engaged in folate biosynthesis. Active folate derivatives are important biomolecules that function as cofactors for a variety of enzymes. Exogenously supplied 5-formyl-tetrahydrofolate abrogated the mutant phenotypes, indicating that the fpgs1-4 mutant produced insufficient folate derivative levels. In addition, the antifolate agents methotrexate and 5-fluorouracil induced starch accumulation from exogenously supplied sucrose in dark-grown seedlings of wild-type Arabidopsis. These results indicate that plastidial folate suppresses starch biosynthesis triggered by sugar influx into non-photosynthetic cells, demonstrating a hitherto unsuspected link between plastidial folate and starch metabolism.

Effect of the Polymorphism of Folylpolyglutamate Synthetase on Treatment of High-Dose Methotrexate in Pediatric Patients with Acute Lymphocytic Leukemia.

BackgroundThe aim of this study was to investigate the association of the polymorphism of folylpolyglutamate synthetase (FPGS) with the dynamic plasma concentration of methotrexate (MTX) in pediatric patients with acute lymphocytic leukemia (ALL), as well as the prognosis.Material/Methods57 ALL patients and 31 age and sex-matched children (control) were included in this study. Polymerase chain reaction-restriction fragment length polymorphism was performed for the analysis of the genotype of FPGS rs1544105 and high-performance liquid chromatography for measurement of MTX plasma concentration after 24-h and 44-h treatment. Overall survival was analyzed by Kaplan-Meier method.ResultsNo differences were observed between patients and controls regarding the distribution frequency of genotype and alleles of rs1544105. Patients carrying AA genotype had a significantly higher plasma concentration of MTX after 24 h than those carrying GG or GA (P<0.05) and no differences were found after 44 h. Kaplan-Meier survival analysis showed a longer median survival time in patients with AA than other genotypes with significant difference in overall survival.ConclusionsPolymorphism of FPGS rs1544105 might be used as an effective approach for prediction of the treatment outcome of MTX.

Pralatrexate: Phase 1/2 Study in Japanese Patients with Relapsed or Refractory Peripheral T-Cell Lymphoma (PTCL)

Pralatrexate: Phase 1/2 Study in Japanese Patients with Relapsed or Refractory Peripheral T-Cell Lymphoma (PTCL)

Arabidopsis plastidial folylpolyglutamate synthetase is required for nitrogen metabolism under nitrate-limited condition in darkness

Folates play an important role in plant metabolism. Here we report a T-DNA insertion mutant (atdfb-3) of the plastidial folylpolyglutamate synthetase gene (AtDFB) was defective in folate metabolism and nitrogen metabolism under nitrate-limited conditions in darkness. Exogenous applied 5-formyl-tetrahydrofolate (5-F-THF) completely restored nitrogen content, soluble protein, total amino acids, individual amino acids including Glu, Gln, Asp, Asn, Pro, Arg and Met, nitrate, and endogenous 5-F-THF in atdfb-3 to the wild-type level. At the same time the application of 5-F-THF partially restored the content of Ser and nitrite in the mutant. Taken together, these results indicated that intact folate metabolism was necessary for nitrogen metabolism in Arabidopsis thaliana under nitrate-limited condition in darkness, providing novel insights into function of folate.

Loss of function of folylpolyglutamate synthetase 1 reduces lignin content and improves cell wall digestibility in Arabidopsis.

BackgroundOne-carbon (C1) metabolism is important for synthesizing a range of biologically important compounds that are essential for life. In plants, the C1 pathway is crucial for the synthesis of a large number of secondary metabolites, including lignin. Tetrahydrofolate and its derivatives, collectively referred to as folates, are crucial co-factors for C1 metabolic pathway enzymes. Given the link between the C1 and phenylpropanoid pathways, we evaluated whether folylpolyglutamate synthetase (FPGS), an enzyme that catalyzes the addition of a glutamate tail to folates to form folylpolyglutamates, can be a viable target for reducing cell wall recalcitrance in plants.ResultsConsistent with its role in lignocellulosic formation, FPGS1 was preferentially expressed in vascular tissues. Total lignin was low in fpgs1 plants leading to higher saccharification efficiency of the mutant. The decrease in total lignin in fpgs1 was mainly due to lower guaiacyl (G) lignin levels. Glycome profiling revealed subtle alterations in the cell walls of fpgs1. Further analyses of hemicellulosic polysaccharides by NMR showed that the degree of methylation of 4-O-methyl glucuronoxylan was reduced in the fpgs1 mutant. Microarray analysis and real-time qRT-PCR revealed that transcripts of a number of genes in the C1 and lignin pathways had altered expression in fpgs1 mutants. Consistent with the transcript changes of C1-related genes, a significant reduction in S-adenosyl-l-methionine content was detected in the fpgs1 mutant. The modified expression of the various methyltransferases and lignin-related genes indicate possible feedback regulation of C1 pathway-mediated lignin biosynthesis.ConclusionsOur observations provide genetic and biochemical support for the importance of folylpolyglutamates in the lignocellulosic pathway and reinforces previous observations that targeting a single FPGS isoform for down-regulation leads to reduced lignin in plants. Because fpgs1 mutants had no dramatic defects in above ground biomass, selective down-regulation of individual components of C1 metabolism is an approach that should be explored further for the improvement of lignocellulosic feedstocks.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-015-0403-z) contains supplementary material, which is available to authorized users.

Folylpolyglutamate synthetase splicing alterations in acute lymphoblastic leukemia are provoked by methotrexate and other chemotherapeutics and mediate chemoresistance

Methotrexate (MTX), a folate antagonist which blocks de novo nucleotide biosynthesis and DNA replication, is an anchor drug in acute lymphoblastic leukemia (ALL) treatment. However, drug resistance is a primary hindrance to curative chemotherapy in leukemia and its molecular mechanisms remain poorly understood. We have recently shown that impaired folylpolyglutamate synthetase (FPGS) splicing possibly contributes to the loss of FPGS activity in MTX-resistant leukemia cell line models and adult leukemia patients. However, no information is available on the possible splicing alterations in FPGS in pediatric ALL. Here, using a comprehensive PCR-based screen we discovered and characterized a spectrum of FPGS splicing alterations including exon skipping and intron retention, all of which proved to frequently emerge in both pediatric and adult leukemia patient specimens. Furthermore, an FPGS activity assay revealed that these splicing alterations resulted in loss of FPGS function. Strikingly, pulse-exposure of leukemia cells to antifolates and other chemotherapeutics markedly enhanced the prevalence of several FPGS splicing alterations in antifolate-resistant cells, but not in their parental antifolate-sensitive counterparts. These novel findings suggest that an assortment of deleterious FPGS splicing alterations may constitute a mechanism of antifolate resistance in childhood ALL. Our findings have important implications for the rational overcoming of drug resistance in individual leukemia patients.

Mutation Screening and Association Study of the Folylpolyglutamate Synthetase (FPGS) Gene with Susceptibility to Childhood Acute Lymphoblastic Leukemia

Folylpolyglutamate synthetase (FPGS), an important enzyme in the folate metabolic pathway, plays a central role in intracellular accumulation of folate and antifolate in several mammalian cell types. Loss of FPGS activity results in decreased cellular levels of antifolates and consequently to polyglutamatable antifolates in acute lymphoblastic leukemia (ALL). During May 1997 and December 2003, 134 children diagnosed with ALL were recruited from one hospital in Thailand. We performed a mutation analysis in the coding regions of the FPGS gene and the association between single nucleotide polymorphisms (SNPs) within FPGS in a case-control sample of childhood ALL patients. Mutation screening was conducted by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) and subsequently with direct sequencing (n=72). Association analysis between common FPGS variants and ALL risk was done in 98 childhood ALL cases and 95 healthy volunteers recruited as controls. Seven SNPs in the FPGS coding region were identified by mutation analysis, 3 of which (IVS13+55C>T, g.1297T>G, and g.1508C>T) were recognized as novel SNPs. Association analysis revealed 3 of 6 SNPs to confer significant increase in ALL risk these being rs7039798 (p= 0.014, OR=2.14), rs1544105 (p=0.010, OR= 2.24), and rs10106 (p=0.026, OR= 1.99). These findings suggested that common genetic polymorphisms in the FPGS coding region including rs7039789, rs1544105, and rs10106 are significantly associated with increased ALL risk in Thai children.