-
Journal of Chromatography. B,... Mar 1996Thiopurine methyltransferase (TPMT) is an important enzyme in the metabolism of 6-mercaptopurine (6MP), which is used in the treatment of acute lymphoblastic leukemia... (Review)
Review
Thiopurine methyltransferase (TPMT) is an important enzyme in the metabolism of 6-mercaptopurine (6MP), which is used in the treatment of acute lymphoblastic leukemia (ALL). TPMT catalyzes the formation of methylthioinosine monophosphate (MetIMP), which is cytotoxic for cultured cell lines, and it plays a role in detoxification of 6MP. Population studies show a genetic polymorphism for TPMT with both high and low activity alleles. About 1 of 300 subjects is homozygous for the low activity. The function TPMT plays in detoxification or therapeutic efficacy of 6MP in vivo is not clear. In this article the genetic polymorphism of TPMT is reviewed and the contribution of TPMT to the cytotoxic action, or detoxification, of 6MP in children with ALL is discussed. Induction of TPMT activity has been described during the treatment for ALL. We performed a pilot study on the influence of high-dose 6MP infusions (1300 mg/m2 in 24 h) on TPMT activity of peripheral blood mononuclear cells (pMNC) of eleven patients with ALL. The TPMT activities were in, or, above the normal range. There was no statistically significant difference between the TPMT activities before and after the 6MP infusions. MetIMP levels in pMNC increased during successive courses. This might be explained by TPMT induction, but other explanations are plausible as well. Twenty five percent of the TPMT assays failed, because less than the necessary 5.10(6) pMNC could be isolated from the blood of leukopenic patients. Red blood cells can not be used for TPMT measurements, since transfusions are frequently required during the treatment with 6MP infusions. Therefore, the influence of high-dose 6MP infusions on TPMT activity can only be investigated further when a TPMT assay which requires less pMNC has been developed.
Topics: Antimetabolites, Antineoplastic; Humans; Inactivation, Metabolic; Mercaptopurine; Methyltransferases; Pilot Projects; Polymorphism, Genetic; Precursor Cell Lymphoblastic Leukemia-Lymphoma
PubMed: 8861653
DOI: 10.1016/0378-4347(95)00432-7 -
Biochemical Pharmacology Mar 1996Treatment with a combination (PMA) of (N-phosphonacetyl)-L-aspartic acid (PALA), methylmercaptopurine riboside (MMPR), and 6-aminonicotinamide (6AN) induced partial...
Treatment with a combination (PMA) of (N-phosphonacetyl)-L-aspartic acid (PALA), methylmercaptopurine riboside (MMPR), and 6-aminonicotinamide (6AN) induced partial regressions of CD8F1 murine mammary tumors and provided for tumor growth inhibition without regression of Colon 38 tumors. HPLC-nucleotide pool analysis of CD8 mammary tumors obtained at various times after treatment with PMA revealed that MMPR-5'-phosphate, which inhibits de novo purine nucleotide biosynthesis, was constant at levels of approximately 2.5 nmol/mg protein for 72 hr after treatment. In contrast, the MMPR-5'-phosphate levels of C38 tumors decreased from 24-hr levels at 1.5 nmol/mg protein with a half-time of about 24 hr. Treatment of CD8 tumor-bearing mice with iodotubercidin, a potent inhibitor of adenosine/MMPR kinase, at various times after PMA, reversed both the accumulation of high levels of MMPR-5'-phosphate and the number of partial tumor regressions. These data demonstrate that a cycle of MMPR rephosphorylation is active in the CD8 mammary tumor and suggest that this recycling of MMPR is important for the optimal effect of PMA treatment.
Topics: 6-Aminonicotinamide; Adenosine Kinase; Adenosine Triphosphate; Animals; Antineoplastic Combined Chemotherapy Protocols; Aspartic Acid; Mammary Neoplasms, Experimental; Methylthioinosine; Mice; Mice, Inbred BALB C; Mice, Inbred DBA; Phosphonoacetic Acid
PubMed: 8615898
DOI: 10.1016/s0006-2952(95)02197-3 -
Biochemical Pharmacology Nov 1995DNA-damaging agents, e.g. Adriamycin (ADR), are reported to cause tumor regression by induction of apoptosis. A reduction in the intracellular content of ATP is part of...
DNA-damaging agents, e.g. Adriamycin (ADR), are reported to cause tumor regression by induction of apoptosis. A reduction in the intracellular content of ATP is part of the biochemical cascade of events that ultimately results in programmed death of the cell, or apoptosis. A chemotherapeutic three-drug combination (PMA) consisting of N-(phosphonacetyl)-L-aspartate (PALA) + 6-methylmercaptopurine riboside (MMPR) + 6-aminonicotinamide (6AN) significantly lowers levels of ATP in CD8F1 murine breast tumors in vivo and produces tumor regression by apoptosis. Addition of the DNA-damaging antitumor agent ADR to PMA was found to further significantly deplete ATP in CD8F1 murine breast tumors in vivo with a concomitant significant increase in the number of tumor regressions. The correlative biochemical and therapeutic results are consistent with, and support, the hypothesis that ATP depletion is a significant factor and, therefore, is a worthy therapeutic target in the production of apoptosis.
Topics: 6-Aminonicotinamide; Adenosine Triphosphate; Animals; Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Aspartic Acid; Doxorubicin; Mammary Neoplasms, Animal; Methylthioinosine; Mice; Mice, Inbred Strains; Neoplasm Transplantation; Phosphonoacetic Acid; Time Factors
PubMed: 8615876
DOI: 10.1016/0006-2952(95)02094-2 -
Journal of Chromatography. B,... Oct 1995The thiopurine antimetabolites 6-thioguanine and 6-mercaptopurine are important chemotherapeutic drugs in the treatment of childhood acute lymphoblastic leukaemia....
The thiopurine antimetabolites 6-thioguanine and 6-mercaptopurine are important chemotherapeutic drugs in the treatment of childhood acute lymphoblastic leukaemia. Measurement of metabolites of these thiopurines is important because correlations exist between levels of these metabolites and the prognosis in childhood acute lymphoblastic leukaemia. The reversed-phase method for the determination of extracellular thiopurine nucleosides and bases was previously developed and has been modified such that methylthiopurine nucleosides, bases, thioxanthine and thiouric acid can be measured also. The anion-exchange method enables the determination of intracellular mono-, di- and triphosphate (methyl)thiopurine nucleotides in one run. Extraction on ice with perchloric acid and dipotassium hydrogenphosphate results in good recoveries for (methyl)thiopurine nucleotides in lymphoblasts and peripheral mononuclear cells and for methylthioinosine nucleotides in red blood cells. Measurement of the low concentrations of mono-, di- and triphosphate thioguanine nucleotides in red blood cells (detection limit 20 pmol/10(9) cells) is possible after extraction with methanol and methylene chloride, followed by oxidation of thioguanine nucleotides with permanganate and fluorimetric detection.
Topics: Calibration; Chromatography, High Pressure Liquid; Erythrocytes; Extracellular Space; Humans; Oxidation-Reduction; Purine Nucleosides; Purine Nucleotides; Purines; Spectrometry, Fluorescence; Thionucleosides; Thionucleotides; Uric Acid
PubMed: 8590937
DOI: 10.1016/0378-4347(95)00206-x -
Biochemical Pharmacology Jan 19956-Methylmercaptopurine ribonucleoside-5'-phosphate (MeSPuRMP), the sole metabolite of 6-methylmercaptopurine ribonucleoside (MeSPuRib), is a strong inhibitor of purine...
6-Methylmercaptopurine ribonucleoside-5'-phosphate (MeSPuRMP), the sole metabolite of 6-methylmercaptopurine ribonucleoside (MeSPuRib), is a strong inhibitor of purine de novo synthesis, inducing depletion of intracellular purine nucleotides and subsequent cell death in several tumor cell lines. In this study prevention of MeSPuRib cytotoxicity by compounds of the purine salvage pathway was studied in Molt F4 human malignant T-lymphoblasts. Adenosine, adenine and inosine were able to prevent depletion of the adenine nucleotide pool when used in combination with 0.5 microM MeSPuRib, but had virtually no effect on depletion of guanine nucleotides. Nevertheless, these three purine compounds were able to reduce the cytotoxic effects induced by MeSPuRib. Addition of guanosine to cells treated with 0.5 microM MeSPuRib normalized the guanine nucleotide pool, but adenine nucleotides remained depleted. Under these conditions, inhibition of cell growth was significantly decreased. With the combination of guanosine and 10 microM MeSPuRib, cytotoxicity was increased compared to 10 microM MeSPuRib alone, associated with a depletion of adenine nucleotides to 9% of untreated cells. Since cell growth and cell viability of Molt F4 cells are less inhibited by MeSPuRib under conditions where adenine nucleotide depletion is prevented by purine compounds (and where the other nucleotides are depleted) we conclude that depletion of adenine nucleotides is an important factor in MeSPuRib cytotoxicity.
Topics: Adenine; Adenosine; Antineoplastic Agents; Cell Division; Cell Survival; Cells, Cultured; Guanosine; Humans; Inosine; Mercaptopurine; Methylthioinosine; Nucleosides; Nucleotides; Purine Nucleosides; Ribonucleosides; T-Lymphocytes; Thioinosine; Thionucleotides
PubMed: 7840782
DOI: 10.1016/0006-2952(94)00387-2 -
Cancer Investigation 1994A quadruple drug combination--consisting of a triple-drug combination of N-(phosphonacetyl)-L-aspartate (PALA) + 6-methylmercaptopurine riboside (MMPR) +...
Biochemical modulation of tumor cell energy in vivo: II. A lower dose of adriamycin is required and a greater antitumor activity is induced when cellular energy is depressed.
A quadruple drug combination--consisting of a triple-drug combination of N-(phosphonacetyl)-L-aspartate (PALA) + 6-methylmercaptopurine riboside (MMPR) + 6-amino-nicotinamide (6-AN), designed to primarily deplete cellular energy in tumor cells, + Adriamycin (Adria)--yielded significantly enhanced anticancer activity (i.e., tumor regressions) over that produced by either Adria alone at maximum tolerated dose (MTD) or by the triple-drug combination, against large, spontaneous, autochthonous murine breast tumors. The adenosine triphosphate (ATP)-depleting triple-drug combination administered prior to Adria resulted in a 100% tumor regression rate (12% complete regression; 88% partial regression) of spontaneous tumors. Histological examination of treated tumors demonstrated that the treatment-induced mechanism of cancer cell death was by apoptosis. The augmented therapeutic results (100% tumor regressions) were obtained with approximately one-half the MTD of Adria as a single agent and suggest the potential clinical benefit of longer, more effective, and safer treatment by low doses of Adria when combined with the triple-drug combination. Two likely mechanisms of action are discussed: (1) prevention of DNA repair; (2) complementary disruption of biochemical pathways by both the triple-drug combination and the biochemical cascade of apoptosis that is induced by a DNA-damaging anticancer agents such as Adria.
Topics: 6-Aminonicotinamide; Animals; Apoptosis; Aspartic Acid; Dose-Response Relationship, Drug; Doxorubicin; Drug Therapy, Combination; Energy Metabolism; Mammary Neoplasms, Experimental; Methylthioinosine; Phosphonoacetic Acid
PubMed: 8187007
DOI: 10.3109/07357909409023028 -
Investigational New Drugs 1994The biochemical modulators PALA, an inhibitor of aspartate transcarbamylase which depletes uridine nucleotide pools, and 6-methylmercaptopurine riboside (MMPR) which... (Clinical Trial)
Clinical Trial
The biochemical modulators PALA, an inhibitor of aspartate transcarbamylase which depletes uridine nucleotide pools, and 6-methylmercaptopurine riboside (MMPR) which inhibits purine metabolism, selectively potentiate the antitumor activity of 5-fluorouracil (5-FU) in preclinical models. Based on a phase I trial of this combination, we performed a phase II trial in patients with advanced pancreatic cancer. PALA 250 mg/m2 was administered i.v. on day 1, followed 24h later by MMPR 150 mg/m2 as a bolus i.v. injection, and 5-FU 2300 mg/m2 by 24h infusion. Treatments were repeated weekly. Seventeen patients, all previously untreated with chemotherapy, were entered, of whom 14 are evaluable for response. Toxicity > or = grade 2 included nausea (6/17), vomiting (4/17), diarrhea (3/17), stomatitis (5/17), and neurotoxicity (2/17). Among 14 evaluable patients there were no partial responses, and two patients with stable disease. Pretreatment with PALA and MMPR is insufficient to enhance the activity of 5-FU in pancreatic cancer.
Topics: Adenocarcinoma; Adult; Aged; Antineoplastic Combined Chemotherapy Protocols; Aspartate Carbamoyltransferase; Aspartic Acid; Female; Fluorouracil; Humans; Male; Methylthioinosine; Middle Aged; Pancreatic Neoplasms; Phosphonoacetic Acid
PubMed: 7775133
DOI: 10.1007/BF00873047 -
Cancer Treatment and Research 1994
Review
Topics: Antimetabolites, Antineoplastic; Aspartic Acid; Clinical Trials as Topic; Colorectal Neoplasms; Drug Design; Drug Resistance, Multiple; Fluorouracil; Humans; Interferons; Methylthioinosine; Multicenter Studies as Topic; Phosphonoacetic Acid; Purines; Pyrimidines; Thymidylate Synthase; Tumor Cells, Cultured
PubMed: 7536018
DOI: No ID Found -
Biochemical Pharmacology Aug 1993Cytotoxicity of 6-mercaptopurine (6MP) and 6-methylmercaptopurine ribonucleoside (Me-MPR) was studied in Molt F4 human malignant lymphoblasts. Both drugs are converted...
Reversal of 6-mercaptopurine and 6-methylmercaptopurine ribonucleoside cytotoxicity by amidoimidazole carboxamide ribonucleoside in Molt F4 human malignant T-lymphoblasts.
Cytotoxicity of 6-mercaptopurine (6MP) and 6-methylmercaptopurine ribonucleoside (Me-MPR) was studied in Molt F4 human malignant lymphoblasts. Both drugs are converted into methylthioIMP (Me-tIMP), which inhibits purine de novo synthesis. Addition of amidoimidazole carboxamide ribonucleoside (AICAR) circumvented inhibition of purine de novo synthesis, and thus partly prevented 6MP and Me-MPR cytotoxicity. Purine nucleotides, and especially adenine nucleotides, were recovered by addition of AICAR. Under these conditions, Me-tIMP formation decreased. The results of this study indicate that formation of Me-tIMP may be important for 6MP cytotoxicity in Molt F4 cells. These data suggest that depletion of adenine nucleotides is the main cause for Me-tIMP cytotoxicity.
Topics: Adenine Nucleotides; Aminoimidazole Carboxamide; Cell Count; Cell Death; Drug Interactions; Guanine Nucleotides; Humans; Mercaptopurine; Methylthioinosine; Ribonucleosides; Thioinosine; Thionucleosides; Thionucleotides; Time Factors; Tumor Cells, Cultured
PubMed: 8347177
DOI: 10.1016/0006-2952(93)90534-4 -
Biochimica Et Biophysica Acta Apr 1993The importance of methyl-thioIMP (Me-tIMP) formation for methylmercaptopurine ribonucleoside (Me-MPR) cytotoxicity was studied in Molt F4 cells. Cytotoxicity of Me-MPR... (Comparative Study)
Comparative Study
The importance of methyl-thioIMP (Me-tIMP) formation for methylmercaptopurine ribonucleoside (Me-MPR) cytotoxicity was studied in Molt F4 cells. Cytotoxicity of Me-MPR is caused by Me-tIMP formation with concomitant inhibition of purine de novo synthesis. Inhibition of purine de novo synthesis resulted in decreased purine nucleotide levels and enhanced 5-phosphoribosyl-1-pyrophosphate (PRPP) levels, with concurrent increased pyrimidine nucleotide levels. The Me-tIMP concentration increased proportionally with the concentration of Me-MPR. High Me-tIMP concentration also caused inhibition of PRPP synthesis. Maximal accumulation of PRPP thus occurred at low Me-MPR concentrations. As little as 0.2 microM Me-MPR resulted already after 2 h in maximal inhibition of formation of adenine and guanine nucleotides, caused by inhibition of purine de novo synthesis by Me-tIMP. Under these circumstances increased intracellular PRPP concentrations could be demonstrated, resulting in increased levels of pyrimidine nucleotides. So, in Molt F4 cells, formation of Me-tIMP from Me-MPR results in cytotoxicity by inhibition of purine de novo synthesis.
Topics: Cell Division; Cell Survival; Humans; Inosine Monophosphate; Mercaptopurine; Methylthioinosine; Phosphoribosyl Pyrophosphate; Purine Nucleotides; T-Lymphocytes; Thioinosine; Thionucleosides; Thionucleotides; Tumor Cells, Cultured
PubMed: 7683208
DOI: 10.1016/0925-4439(93)90110-m