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Science (New York, N.Y.) Jan 2014The bacterial clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 system for genome editing has greatly expanded the toolbox for mammalian genetics,...
The bacterial clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 system for genome editing has greatly expanded the toolbox for mammalian genetics, enabling the rapid generation of isogenic cell lines and mice with modified alleles. Here, we describe a pooled, loss-of-function genetic screening approach suitable for both positive and negative selection that uses a genome-scale lentiviral single-guide RNA (sgRNA) library. sgRNA expression cassettes were stably integrated into the genome, which enabled a complex mutant pool to be tracked by massively parallel sequencing. We used a library containing 73,000 sgRNAs to generate knockout collections and performed screens in two human cell lines. A screen for resistance to the nucleotide analog 6-thioguanine identified all expected members of the DNA mismatch repair pathway, whereas another for the DNA topoisomerase II (TOP2A) poison etoposide identified TOP2A, as expected, and also cyclin-dependent kinase 6, CDK6. A negative selection screen for essential genes identified numerous gene sets corresponding to fundamental processes. Last, we show that sgRNA efficiency is associated with specific sequence motifs, enabling the prediction of more effective sgRNAs. Collectively, these results establish Cas9/sgRNA screens as a powerful tool for systematic genetic analysis in mammalian cells.
Topics: Antigens, Neoplasm; Antimetabolites, Antineoplastic; Antineoplastic Agents, Phytogenic; Clustered Regularly Interspaced Short Palindromic Repeats; DNA Mismatch Repair; DNA Topoisomerases, Type II; DNA-Binding Proteins; Drug Resistance, Neoplasm; Etoposide; Gene Knockout Techniques; Gene Library; Genetic Testing; Genome-Wide Association Study; Humans; Poly-ADP-Ribose Binding Proteins; RNA; Thioguanine
PubMed: 24336569
DOI: 10.1126/science.1246981 -
Clinical Pharmacology and Therapeutics May 2019Thiopurine methyltransferase (TPMT) activity exhibits a monogenic codominant inheritance and catabolizes thiopurines. TPMT variant alleles are associated with low enzyme...
Thiopurine methyltransferase (TPMT) activity exhibits a monogenic codominant inheritance and catabolizes thiopurines. TPMT variant alleles are associated with low enzyme activity and pronounced pharmacologic effects of thiopurines. Loss-of-function alleles in the NUDT15 gene are common in Asians and Hispanics and reduce the degradation of active thiopurine nucleotide metabolites, also predisposing to myelosuppression. We provide recommendations for adjusting starting doses of azathioprine, mercaptopurine, and thioguanine based on TPMT and NUDT15 genotypes (updates on www.cpicpgx.org).
Topics: Antimetabolites, Antineoplastic; Azathioprine; Dose-Response Relationship, Drug; Drug Dosage Calculations; Humans; Inactivation, Metabolic; Mercaptopurine; Methyltransferases; Pharmacogenetics; Pharmacogenomic Testing; Pyrophosphatases; Thioguanine
PubMed: 30447069
DOI: 10.1002/cpt.1304 -
Leukemia Jul 2022Maintenance therapy (MT) with oral methotrexate (MTX) and 6-mercaptopurine (6-MP) is essential for the cure of acute lymphoblastic leukemia (ALL). MTX and 6-MP interfere... (Review)
Review
Maintenance therapy (MT) with oral methotrexate (MTX) and 6-mercaptopurine (6-MP) is essential for the cure of acute lymphoblastic leukemia (ALL). MTX and 6-MP interfere with nucleotide synthesis and salvage pathways. The primary cytotoxic mechanism involves the incorporation of thioguanine nucleotides (TGNs) into DNA (as DNA-TG), which may be enhanced by the inhibition of de novo purine synthesis by other MTX/6-MP metabolites. Co-medication during MT is common. Although Pneumocystis jirovecii prophylaxis appears safe, the benefit of glucocorticosteroid/vincristine pulses in improving survival and of allopurinol to moderate 6-MP pharmacokinetics remains uncertain. Numerous genetic polymorphisms influence the pharmacology, efficacy, and toxicity (mainly myelosuppression and hepatotoxicity) of MTX and thiopurines. Thiopurine S-methyltransferase (encoded by TPMT) decreases TGNs but increases methylated 6-MP metabolites (MeMPs); similarly, nudix hydrolase 15 (encoded by NUDT15) also decreases TGNs available for DNA incorporation. Loss-of-function variants in both genes are currently used to guide MT, but do not fully explain the inter-patient variability in thiopurine toxicity. Because of the large inter-individual variations in MTX/6-MP bioavailability and metabolism, dose adjustments are traditionally guided by the degree of myelosuppression, but this does not accurately reflect treatment intensity. DNA-TG is a common downstream metabolite of MTX/6-MP combination chemotherapy, and a higher level of DNA-TG has been associated with a lower relapse hazard, leading to the development of the Thiopurine Enhanced ALL Maintenance (TEAM) strategy-the addition of low-dose (2.5-12.5 mg/m/day) 6-thioguanine to the 6-MP/MTX backbone-that is currently being tested in a randomized ALLTogether1 trial (EudraCT: 2018-001795-38). Mutations in the thiopurine and MTX metabolism pathways, and in the mismatch repair genes have been identified in early ALL relapses, providing valuable insights to assist the development of strategies to detect imminent relapse, to facilitate relapse salvage therapy, and even to bring about changes in frontline ALL therapy to mitigate this relapse risk.
Topics: Humans; Mercaptopurine; Methotrexate; Methyltransferases; Precursor Cell Lymphoblastic Leukemia-Lymphoma; Recurrence; Thioguanine
PubMed: 35654820
DOI: 10.1038/s41375-022-01591-4 -
Blood Apr 1995The goal of this phase II multicenter clinical trial was to evaluate a new intensive chemotherapy program for adults with untreated acute lymphoblastic leukemia (ALL)... (Clinical Trial)
Clinical Trial
The goal of this phase II multicenter clinical trial was to evaluate a new intensive chemotherapy program for adults with untreated acute lymphoblastic leukemia (ALL) and to examine prospectively the impact of clinical and biologic characteristics on the outcome. One hundred ninety-seven eligible and evaluable patients (16 to 80 years of age; median, 32 years of age) received cyclophosphamide, daunorubicin, vincristine, prednisone, and L-asparaginase; 167 patients (85%) achieved a complete remission (CR), 13 (7%) had refractory disease, and 17 (9%) died during induction. A higher CR rate was observed in younger patients (94% for those < 30 years old, 85% for those 30 to 59 years old, and 39% for those > or = 60 years old, P < .001) and in those who had a mediastinal mass (100%) or blasts with a T-cell immunophenotype. Eighty percent of B-lineage and 97% of T-cell ALL patients achieved a CR (P = .01). The coexpression of myeloid antigens did not affect the response rate or duration. Seventy percent of those with cytogenetic or molecular evidence of the Philadelphia (Ph) chromosome and 84% of those without such evidence achieved a CR (P = .11). Patients in remission received multiagent consolidation treatment, central nervous system prophylaxis, late intensification, and maintenance chemotherapy for a total of 24 months. After a median follow-up time of 43 months, the median survival for all 197 patients is 36 months; the median remission duration for the 167 CR patients is 29 months. Favorable pretreatment characteristics relative to remission duration or survival are younger age, the presence of a mediastinal mass or lymphadenopathy, a white blood cell count (WBC) less than 30,000/microL, L1 morphology, T or TMy immunophenotype, and the absence of the Ph chromosome. The estimates of the proportion surviving at 3 years are 69% for patients less than 30 years old, 39% for those 30 to 59 years old, 89% for those who had a mediastinal mass, 59% with WBC less than 30,000/microL, 63% with L1 morphology, 69% for T or TMy antigen expression, and 62% for those who lack the Ph chromosome. Fifteen patients (8%) had no unfavorable prognostic factors and have an estimated probability of survival at 5 years of 100% (95% confidence interval, 77% to 100%). This intensive chemotherapy regimen produces a high remission rate and a high proportion of durable remissions in adults with ALL.
Topics: Adolescent; Adult; Aged; Aged, 80 and over; Antineoplastic Combined Chemotherapy Protocols; Asparaginase; Combined Modality Therapy; Cranial Irradiation; Cyclophosphamide; Cytarabine; Daunorubicin; Doxorubicin; Drug Administration Schedule; Female; Humans; Immunophenotyping; Life Tables; Male; Mercaptopurine; Methotrexate; Middle Aged; Multivariate Analysis; Precursor Cell Lymphoblastic Leukemia-Lymphoma; Prednisone; Prospective Studies; Remission Induction; Risk Factors; Survival Analysis; Thioguanine; Treatment Outcome; Vincristine
PubMed: 7718875
DOI: No ID Found -
Journal of Gastrointestinal and Liver... Dec 2020Thiopurine-derivates azathioprine and mercaptopurine are frequently used to maintain remission in inflammatory bowel diseases (IBD). Despite their efficacy, more than... (Review)
Review
Thiopurine-derivates azathioprine and mercaptopurine are frequently used to maintain remission in inflammatory bowel diseases (IBD). Despite their efficacy, more than 50% of patients discontinue therapy, mainly due to the development of adverse events. Thioguanine is an alternative thiopurine and has been conditionally licensed in The Netherlands as IBD treatment for patients after conventional thiopurine therapy failure. In this review we will provide practical information on initiating and maintaining thioguanine therapy in IBD and provide information concerning safety issues and future perspectives. The thioguanine toxicity profile is relatively mild and the reported incidence of nodular regenerative hyperplasia related to thioguanine use seems comparable to conventional thiopurines and the background incidence in IBD patients. Routine monitoring of laboratory parameters and adverse events is recommended, comparable to the monitoring of patients on conventional thiopurine therapy.
Topics: Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Thioguanine
PubMed: 33331335
DOI: 10.15403/jgld-2765 -
British Journal of Cancer Sep 1974Seventy-eight adult patients with acute leukaemia were classified cytologically into 3 categories: acute lymphoblastic leukaemia (ALL), acute myelogenous leukaemia (AML)...
Seventy-eight adult patients with acute leukaemia were classified cytologically into 3 categories: acute lymphoblastic leukaemia (ALL), acute myelogenous leukaemia (AML) or acute undifferentiated leukaemia (AUL). The periodic acid-Schiff stain was of little value in differentiating the 3 groups. The treatment response in each group was different: 94% of patients with ALL (16/17) achieved complete remission with prednisone, vincristine and other drugs in standard use in childhood ALL; 59% of patients with AML (27/46) achieved complete remission with cytosine arabinoside and daunorubicin (22 patients), or 6-thioguanine and cyclophosphamide (2 patients), 6-thioguanine, cyclophosphamide and Adriamycin (1 patient), and cytosine and Adriamycin (1 patient); only 2 out of 14 patients (14%) with acute undifferentiated leukaemia achieved complete remission using cytosine and daunorubicin after an initial trial of prednisone and vincristine had failed. Prednisone and vincristine would seem to be of no value in acute undifferentiated leukaemia. It would seem also that no benefit is obtained by classifying all patients with acute leukaemia over 20 years of age as "adult acute leukaemia" and treating them with the same polypharmaceutical regimen. The problems posed by each disease are different and such a policy serves only to obscure them.
Topics: Acute Disease; Administration, Oral; Adult; Aged; Antineoplastic Agents; Cyclophosphamide; Cytarabine; Cytosine; Daunorubicin; Doxorubicin; Drug Therapy, Combination; Humans; Injections, Intravenous; Leukemia; Leukemia, Lymphoid; Leukemia, Myeloid, Acute; Middle Aged; Prednisone; Remission, Spontaneous; Staining and Labeling; Thioguanine; Vincristine
PubMed: 4141625
DOI: 10.1038/bjc.1974.191 -
British Journal of Clinical Pharmacology Apr 2014The activity of the enzyme thiopurine methyltransferase (TPMT) is regulated by a common genetic polymorphism. One in 300 individuals lack enzyme activity and 11% are...
The activity of the enzyme thiopurine methyltransferase (TPMT) is regulated by a common genetic polymorphism. One in 300 individuals lack enzyme activity and 11% are heterozygous for a variant low activity allele and have an intermediate activity. The thiopurine drugs azathioprine, mercaptopurine and thioguanine are substrates for TPMT; these drugs exhibit well documented myelosuppressive effects on haematopoietic cells and have a track record of idiosyncratic drug reactions. The development of severe bone marrow toxicity, in patients taking standard doses of thiopurine drugs, is associated with TPMT deficiency whilst the TPMT heterozygote is at an increased risk of developing myelosuppression. Factors influencing TPMT enzyme activity, as measured in the surrogate red blood cell, are discussed in this review to enable an appreciation of why concordance between TPMT genotype and phenotype is not 100%. This is particularly important for lower/intermediate TPMT activities to avoid misclassification of TPMT status. TPMT testing is now widely available in routine service laboratories. The British National Formulary suggests TPMT testing before starting thiopurine drugs. Dermatologists were quick to adopt routine TPMT testing whilst gastroenterologists do not specifically recommend TPMT screening. TPMT testing is mandatory prior to the use of mercaptopurine in childhood leukaemia. Thiopurine drug dose and other treatment related influences on cell counts explain some of the differing recommendations between clinical specialities. TPMT testing is cost-effective and the major role is in the identification of the TPMT deficient individual prior to the start of thiopurine drugs.
Topics: Antimetabolites, Antineoplastic; Azathioprine; Cost-Benefit Analysis; Drug Hypersensitivity; Drug Labeling; Genetic Testing; Genotype; Humans; Mercaptopurine; Methyltransferases; Phenotype; Purine-Pyrimidine Metabolism, Inborn Errors; Thioguanine
PubMed: 23962279
DOI: 10.1111/bcp.12226 -
World Journal of Gastroenterology Oct 2016To critically assess the available literature regarding the efficacy of thioguanine treatment in inflammatory bowel disease (IBD) patients, irrespective of the (hepato-)... (Review)
Review
AIM
To critically assess the available literature regarding the efficacy of thioguanine treatment in inflammatory bowel disease (IBD) patients, irrespective of the (hepato-) toxicity profile.
METHODS
A systematic literature search of the MEDLINE database using PubMed was performed using the keywords "thioguanine", "6-TG", "thioguanine", "inflammatory bowel disease", "IBD", "Crohn's disease", "Ulcerative colitis" and "effectiveness" in order to identify relevant articles published in English starting from 2000. Reference lists of the included articles were cross-checked for missing articles. Reviewed manuscripts concerning the effectiveness of thioguanine treatment in IBD were reviewed by the authors and the data were extracted. Data were subsequently analyzed with descriptive statistics. Due to the lack of standardized outcomes, a formal meta-analysis was not performed.
RESULTS
A total of 11 applicable studies were found that involved the effectiveness of thioguanine therapy in IBD. Eight studies were conducted in a prospective manner, in the remaining three studies, data was collected retrospectively. In total, 353 IBD-patients (225 patients with Crohn's disease, 119 with ulcerative colitis and nine with unclassified IBD) with prior azathioprine/mercaptopurine resistance and/or intolerance ( = 321) or thioguanine administration ( = 32) were included for analysis, of which 228 (65%) had clinical improvement on thioguanine therapy, based on standard IBD questionnaires, biochemical parameters or global physician assessments. Short-term results were based on 268 treatment years (median follow-up 9 mo, range 3-22 mo) with a median daily dose of 20 mg (range 10-80 mg). Discontinuation, mostly due to adverse events, was reported in 72 patients (20%).
CONCLUSION
The efficacy of thioguanine therapy in IBD patients intolerant to conventional thiopurine therapy is observed in 65%, with short term adverse events in 20% of patients.
Topics: Antimetabolites, Antineoplastic; Humans; Inflammatory Bowel Diseases; Thioguanine
PubMed: 27833392
DOI: 10.3748/wjg.v22.i40.9012