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J Jolivet

Publications and source records attributed to J Jolivet.

At least 19 recordsLinked to original sources
PubMed1997

5-Formyltetrahydrofolate regulates homocysteine remethylation in human neuroblastoma.

The metabolic role of 5-formyltetrahydrofolate is not known; however, it is an inhibitor of several folate-dependent enzymes including serine hydroxymethyltransferase. Methenyltetrahydrofolate synthetase (MTHFS) is the only enzyme known to metabolize 5-formyltetrahydrofolate and catalyzes the conversion of 5-formyltetrahydrofolate to 5,10-methenyltetrahydrofolate. In order to address the function of 5-formyltetrahydrofolate in mammalian cells, intracellular 5-formyltetrahydrofolate levels were depleted in human 5Y neuroblastoma by overexpressing the human cDNA encoding MTHFS (5YMTHFS cells). When cultured with 2 mM exogenous glycine, the intracellular serine and glycine concentrations in 5YMTHFS cells are elevated approximately 3-fold relative to 5Y cells; 5YMTHFS cells do not contain measurable levels of free methionine and display a 30-40% decrease in cell proliferation rates compared with 5Y cells. Medium supplemented with pharmacological levels of exogenous folinate or methionine ameliorated the glycine induced growth inhibition. Analysis of the folate derivatives demonstrated that 5-methyltetrahydrofolate accounts for 30% of total cellular folate in 5Y cells when cultured with 5 mM exogenous glycine. 5YMTHFS cells do not contain detectable levels of 5-methyltetrahydrofolate under the same culture conditions. These results suggest that 5-formyltetrahydrofolate inhibits serine hydroxymethyltransferase activity in vivo and that serine synthesis and homocysteine remethylation compete for one-carbon units in the cytoplasm.

Antidotes↗
PubMed1997

Mitoxantrone, 5-fluorouracil, and high dose leucovorin (NFL) versus intravenous cyclophosphamide, methotrexate, and 5-fluorouracil (CMF) in first-line chemotherapy for patients with metastatic breast carcinoma: a randomized phase II trial.

BACKGROUND: Previous Phase II studies using the combination of mitoxantrone, 5-fluorouracil, and high dose leucovorin (NFL) in the treatment of metastatic breast carcinoma have shown this regimen to be active and well tolerated. In this randomized Phase II study, the authors compared the NFL regimen with a standard CMF regimen in the first-line therapy of patients with metastatic breast carcinoma. METHODS: One hundred twenty-eight women receiving their first chemotherapy for metastatic breast carcinoma were entered into this randomized study. Sixty-four patients were treated with NFL: mitoxantrone 12 mg/m2 IV on Day 1; leucovorin 300 mg IV over 30-60 minutes on Days 1, 2, and 3, immediately preceding administration of 5-fluorouracil; and 5-fluorouracil 350 mg/m2 IV bolus on Days 1, 2, and 3. Sixty-four patients received CMF: cyclophosphamide 600 mg/m2 IV on Day 1; methotrexate 40 mg/m2 IV on Day 1; and 5-fluorouracil 600 mg/m2 IV on Day 1. Both regimens were repeated at 21-day intervals; responding patients received at least 8 courses. RESULTS: Patients treated with NFL had a higher response rate than patients treated with the CMF regimen (45% vs. 26%, respectively; P = 0.021). Median duration of response was 9 months with NFL and 6 months with CMF (P = 0.10); 11 patients had long responses (>12 months) with NFL versus 4 patients with CMF (P = 0.06). Median survival was similar for both groups. Both regimens were well tolerated, with infrequent Grade 3 or 4 toxicities. CONCLUSIONS: NFL is an active, well-tolerated regimen for the treatment of metastatic breast carcinoma; it produced a higher response rate than the CMF regimen used in this study. Although more intense CMF regimens or regimens containing doxorubicin would likely increase the response rate, they would almost certainly do so with the consequence of greater toxicity as compared with NFL. NFL is an excellent initial palliative treatment option for elderly patients or patients who have exhibited poor tolerance for other chemotherapy regimens.

Adult↗
PubMed1997

Confocal microscopy visualization of antifolate uptake by the reduced folate carrier in human leukaemic cells.

Confocal microscopy was used to visualize the intracellular uptake of the fluorescent methotrexate analogue, fluorescein-MTX (F-MTX), in human leukaemic cell lines and leukaemic blasts. Cytosolic labelling of wild-type K562 human erythroleukaemia cells was detected during 3-60 min incubations with F-MTX (1 microM) and was completely inhibited by co-exposure to either methotrexate or the thymidylate synthase inhibitor, ZD1694. There was no significant intracellular F-MTX accumulation over this period in a K562 subline (K500E) with a documented defect (approximately 10% of wild type) in membrane transport by the reduced folate carrier (RFC). F-MTX uptake was re-established in K500E cells transfected with a cDNA to human RFC, establishing a role for RFC in the cellular uptake of this compound. High levels of intracellular labelling were detected in all cell lines after prolonged (24 h) F-MTX incubations, however F-MTX accumulation at this time was not inhibited by ZD1694. F-MTX uptake by RFC was also detected in leukaemic blasts from children with acute lymphoblastic leukaemia and could be blocked with ZD1694. In leukaemic blasts with a documented defect in MTX uptake, F-MTX accumulation was abolished in almost all the cells. These results display the power of confocal microscopy for directly visualizing RFC-mediated anti-folate uptake. Over short intervals, F-MTX uptake is mediated by RFC, however, RFC-independent processes predominate during long drug exposures. Direct assay by confocal microscopy may be better suited than other indirect methods (i.e. flow cytometry) for detecting low levels of RFC transport in leukaemic blasts from patients undergoing chemotherapy with methotrexate.

Biological Transport↗
PubMed1996

Biochemical and molecular studies of human methenyltetrahydrofolate synthetase.

5-FormylH4folate is administered clinically under the name Leucovorin in association with the antineoplastic agent 5-fluorouracil (5-FU) to enhance the cytotoxic effects of 5-FU. The combination has been shown to be superior to 5-FU alone in the treatment of patients with metastatic colorectal carcinoma. Methenyltetrahydrofolate synthetase (MTHFS) catalyzes the transformation of 5-formyl-tetrahydrofolate to methenylH4folate, which is the obligatory initial metabolic step prior to the intracellular conversion of 5-formylH4folate to other reduced folates and the increase in intracellular folate pools required for 5-FU potentiation. In the following paper, we will summarize results of biochemical and molecular studies of human MTHFS.

Animals↗
PubMed1996

Functional aspects of membrane folate receptors in human breast cancer cells with transport-related resistance to methotrexate.

Two methotrexate (MTX)-resistant human breast-cancer cell lines with impaired transport via the reduced folate carrier (RFC), one established in vitro (MTX(R)-ZR-75-1) and another inherently resistant (MDA-231), were adapted to grow in medium containing 2 nM folic acid. This induced the expression of previously undetectable membrane folate receptors (MFR) to levels of 8.2 and 2.3 pmol/10(7) cells, respectively. Polymerase chain reaction (PCR) quantitation revealed that MFR messenger-RNA levels of the isoform first described in human nasopharyngeal carcinoma KB cells (MFR-alpha) were increased in low-folate-adapted MTX(R)-ZR-75-1 cells, whereas placental transcripts (MFR-beta) coincided with MFR-alpha expression in low-folate (LF)-adapted MDA-231 cells. These cell lines were used to study the role of MFR in the uptake and growth-inhibitory effects of five different antifolates with varying affinities for MFR: N10-propargyl-5, 8-dideazafolic acid (CB3717) > 5,10-dideazatetra-hydrofolic acid (DDATHF) > N-5-[N-(3,4-dihydro-2-methyl-4-oxoquinazolin-6-methyl) -N-methyl-amino]-2-theonyl}-glutamic acid (ZD1694) >> MTX > edatrexate (EDX). Expression of MFR only slightly decreased the resistant phenotype for MTX, EDX, and ZD1694, suggesting that these drugs are not transported intracellularly to cytotoxic concentrations at these levels of MFR expression. On the other hand, both cell lines became from at least 180- to 400-fold more sensitive to growth inhibition by CB3717 and DDATHF, which may be correlated with their high affinity for MFR. These sensitivity/resistance profiles were largely similar following cell culture in medium containing 1 nM L-leucovorin, a folate with an affinity for MFR 10-fold lower than that of folic acid, the one exception being the increased sensitivity for ZD1694 seen in the LF-adapted cells with the highest level of MFR expression (MTX(R)-ZR-75-1). These results illustrate that the efficacy of MFR in mediating antifolate transport and cytotoxicity depends on their affinity for the folate antagonist, their degree of expression, and the levels of competing folates.

Aminopterin↗
PubMed1995

Cloning and characterization of the human 5,10-methenyltetrahydrofolate synthetase-encoding cDNA.

Methenyltetrahydrofolate synthetase (MTHFS) catalyses the obligatory initial metabolic step in the intracellular conversion of 5-formyltetrahydrofolate to other reduced folates. We have isolated and sequenced a human MTHFS cDNA which is 872-bp long and codes for a 203-amino-acid protein of 23,229 Da. Escherichia coli BL21(DE3), transfected with pET11c plasmids containing an open reading frame encoding MTHFS, showed a 100-fold increase in MTHFS activity in bacterial extracts after IPTG induction. Northern blot studies of human tissues determined that the MTHFS mRNA was expressed preferentially in the liver and Southern blot analysis of human genomic DNA suggested the presence of a single-copy gene.

Amino Acid Sequence↗
PubMed1995

Identification and characterization of human mitochondrial methenyltetrahydrofolate synthetase activity.

We present evidence for the presence of the folate metabolism enzyme methenyltetrahydrofolate synthetase (MTHFS) in mitochondria. MTHFS activity was identified in the matrix of mitochondria purified from human liver biopsies. Mitochondrial and cytoplasmic MTHFS specific activities are similar, 85% of the total cellular MTHFS activity is in the cytoplasm and both native enzymes have similar molecular weights (approximately 25 kDa). Studies using purified mitochondrial MTHFS from CA46 human Burkitt lymphoma cells reveal that mitochondrial MTHFS behaves kinetically like the cytoplasmic enzyme with Km values of 4.7, 0.8 and 22 microM respectively for (6R,S)-5-formyltetrahydrofolate monoglutamate, (6S)-5-formyltetrahydrofolate pentaglutamate and ATP. This finding adds to previous observations that various folate-dependent enzymes reside in the mitochondria of eucaryotic cells. Intracellular tetrahydrofolate metabolism is highly compartmentalized and mitochondrial MTHFS activity is necessary for the entry of mitochondrial 5-formyltetrahydrofolate into the mitochondrial folate pool.

Burkitt Lymphoma↗
PubMed1995

Phase II study of topotecan (NSC 609 699) in patients with recurrent or metastatic soft tissue sarcoma.

BACKGROUND: New drugs are needed for treatment of unresectable or metastatic soft tissue sarcoma. Topotecan, a semisynthetic derivative of the alkaloid, camptothecin, exerts its cytotoxic effect through inhibition of topoisomerase I. PATIENTS AND METHODS: Thirty-two adult patients with locally advanced or metastatic soft tissue sarcoma entered this phase II study of topotecan, administered at 1.5 mg/m2/day IV x 5 days every 3 weeks. All had measurable disease and none had received previous chemotherapy. RESULTS: There were 3 partial responses (10.3%; 95% CI 2.2-27.4%) in 29 evaluable patients. Grade 3 or 4 neutropenia occurred in 25 patients, and there was a 17% incidence of infection/neutropenic fever leading to one toxic death. CONCLUSIONS: Topotecan, in this dose and schedule, has low activity in adult soft tissue sarcoma.

Adolescent↗
PubMed1994

Leucovorin rescue of human cancer and bone marrow cells following edatrexate or methotrexate.

We have examined the cytotoxic activities of edatrexate (EDX) and methotrexate (MTX) and their reversal by leucovorin in nine human cancer cell lines and in human bone marrow CFU-GM cells. EDX was 3.7- to 123-fold more toxic than MTX against the cancer cell lines and 25-fold against the bone marrow cells. Lower EDX concentrates generally were needed to inhibit cancer cell growth relative to bone marrow cells, however, whereas bone marrow and cancer cell growth were more often susceptible to the same MTX concentrations. The new antifolate was metabolized to long-chain polyglutamates to a greater extent than MTX in seven cell lines. Leucovorin at 0.2 microM rescued two breast cancer and two non-small cell lung cancer cell lines to a lesser extent following EDX than MTX, but significant rescue was observed in two head and neck cancer cell lines that formed large amounts of polyglutamates. These cell lines also accumulated reduced folates to a greater extent than the other cell lines following leucovorin exposure. Leucovorin rescued bone marrow cells following MTX but only partially following the highest EDX concentrations. EDX may enjoy a better therapeutic index than MTX against some cancer cell lines relative to bone marrow precursor cells, especially after leucovorin rescue.

Aminopterin↗
PubMed1994

The importance of dose scheduling with mitoxantrone, 5-fluorouracil and leucovorin in metastatic breast cancer.

We have studied a mitoxantrone, 5-fluorouracil (5-FU) and leucovorin chemotherapy regimen in metastatic breast cancer. 8 patients received mitoxantrone 10 mg/m2 on day 1, leucovorin 200 mg/m2 and 5-FU 300 mg/m2 on days 1-5 by intravenous bolus every 28 days in a pilot study. Grades 3-4 granulocytopenia followed 55% of the courses, with 2 patients admitted for febrile neutropenia. Only a 29% objective response rate was seen in a subsequent phase II trial using reduced mitoxantrone doses. Comparison with other trials suggested that 5-day bolus 5-FU administration adversely affects the combination's therapeutic index.

Adenocarcinoma↗
PubMed1994

Docetaxel in advanced renal carcinoma. A phase II trial of the National Cancer Institute of Canada Clinical Trials Group.

BACKGROUND: Most patients diagnosed with renal carcinoma developed metastatic disease at some time during their course, with available therapy inducing response in only a small proportion of patients. Docetaxel (Taxotere, RP56976) a semi-synthetic analogue of paclitaxel with a broad range of in vitro antitumor activity, was evaluated in a phase II study. METHODS: Eligibility criteria included histologically proven metastatic or advanced, bidimensionally measurable disease, no prior chemotherapy, immunotherapy, or hormonal therapy, adequate hematologic (neutrophils > or = 2.0 x 10(9)/L, platelets > or = 100 x 10(9)/L) and biochemical (serum creatinine and bilirubin < or = 1.5 x normal, transaminases < or = 3 x normal) parameters, WHO performance status of at least 2, and a life expectancy of > 12 weeks. Docetaxel was administered in a dose of 100 mg/m2 as a 1 hour intravenous infusion every 3 weeks. The first 2 patients entered onto the study were not premedicated for hypersensitivity reactions; subsequent patients received dexamethasone 10 mg and diphenhydramine 50 mg i.v. 30 minutes prior to docetaxel. RESULTS: Twenty patients were entered onto the study, with 2 considered inevaluable for response. Sixty cycles of therapy were administered, with only 2 cycles delivered at a dose of 55 mg/m2 or less. No objective responses were seen; 1 patient demonstrated a mixed response. Neutropenia was significant, with 42/60 cycles developing grade 3/4 granulocytopenia. Fifty-five percent of patients demonstrated hypersensitivity reactions despite the premedication regimen employed, higher than that of the phase I studies which established the dose and schedule used in this trial. CONCLUSIONS: 1) Docetaxel is an ineffective agent in advanced renal carcinoma. 2) The high rate of hypersensitivity reactions suggests the need for more intensive premedication and/or slower infusion times at this dose level.

Adult↗
PubMed1993

Phase I pharmacokinetic study of DUP-937, a new anthrapyrazole.

DUP-937 is a new anthrapyrazole intercalator that inhibits DNA synthesis. A phase I trial was conducted in which DUP-937 was given in an intravenous bolus weekly for 3 weeks. Cycles were repeated every 5 weeks. Twenty men and 13 women with median ECOG performance status of 1 completed 74 cycles. The starting dose was 0.55 mg/m2/week and doses were escalated to 16 mg/m2/week. Non-hematological toxicity was generally mild or moderate and consisted mainly of gastro-intestinal effects, fatigue, alopecia and local reactions. Grade 3 neutropenia was first documented at 7.36 mg/m2 and became more common at higher dose levels. Three of four patients had > or = grade 3 neutropenia at the 16 mg/m2 dose level. Thrombocytopenia was minimal. The dose-limiting toxicity was neutropenia and the maximum tolerated dose was 16 mg/m2 weekly for 3 weeks. Mean area under the curve (AUC) values increased with dose. Linear pharmacokinetics were observed as total body clearance (CLtb), half-life (t1/2) and volume of distribution (Vss) did not change with increasing doses. One partial remission in a patient with prostate carcinoma was documented.

Adult↗
PubMed1992

Factors that influence the therapeutic activity of 5-fluorouracil [6RS]leucovorin combinations in colon adenocarcinoma xenografts.

The therapeutic activity of FUra alone or combined with [6RS]LV doses ranging from 50 to 1,000 mg/m2 was examined in eight colon adenocarcinoma xenografts, of which five were established from adult neoplasms (HxELC2, HxGC3, HxVRC5, HxHC1, and HxGC3/c1TK-c3 selected for TK deficiency) and three were derived from adolescent tumors (HxSJC3A, HxSJC3B, and HxSJC2). The growth-inhibitory effects of FUra were potentiated by higher doses of [6RS]LV (500-1,000 mg/m2) in three lines (HxGC3/c1TK-c3, HxSJC3A, and HxSJC3B) and by a low dose of [6RS]LV in only one tumor (HxVRC5). Expansion of pools of CH2-H4PteGlun+H4PteGlun (greater than or equal to 2.4-fold) in response to higher doses of [6RS]LV was obtained in all lines except HxHC1. Metabolism of [6RS]LV was high in HxVRC5, with high levels of 5-CH3-H4PteGlu being detected, but not in HxHC1, in which levels of 5-CH3-H4PteGlu and CH = H4PteGlu+10-CHO-H4PteGlu remained relatively low. In the adolescent tumors, levels of CH = H4PteGlu+10-CHO-H4PteGlu were consistently higher than those of 5-CH3-H4PteGlu following [6RS]LV administration, and in HxSJC3A, in which pools of CH2-H4PteGlun+H4PteGlun were significantly expanded, 5-CH3-H4PteGlu concentrations were lower than those observed in the other two lines. The sensitivity of tumors to FUra +/- [6RS]LV and the characteristics of [6S]LV metabolism did not correlate with the activity of CH = H4PteGlu synthetase, the enzyme responsible for the initial cellular metabolism of [6S]LV to CH = H4PteGlu. Thus, no single metabolic phenotype correlated with the [6RS]LV-induced expansion of CH2-H4PteGlun+H4PteGlun pools. Potentiation of the therapeutic efficacy of FUra by [6RS]LV was observed in HxGC3/c1TK-c3 xenografts but not in parent HxGC3 tumors, demonstrating the influence of dThd salvage capability in the response to FUra-[6RS]LV combinations. Plasma dThd concentrations in CBA/CaJ mice were high (1.1 microM). The present data therefore demonstrate the importance of (1) higher doses of [6RS]LV, (2) expansion of pools of CH2-H4PteGlun+H4PteGlun, and (3) dThd salvage capability in potentiation of the therapeutic efficacy of FUra in colon adenocarcinoma xenografts. The plasma levels of FUra achieved in mice are presented.

Adenocarcinoma↗
PubMed1989

Lack of interference by the unnatural isomer of 5-formyltetrahydrofolate with the effects of the natural isomer in leucovorin preparations.

Leucovorin, a mixture of the natural (6S) and unnatural (6R) diastereomers of 5-formyltetrahydrofolate, is administered clinically to enhance the antitumor activity of 5-fluorouracil. Because the 6R isomer persists at high concentrations in plasma for prolonged periods after iv leucovorin administration (J Clin Oncol 4:685-696, 1986), we have examined it to ascertain whether the 6R isomer could interfere with the cellular effects of the 6S isomer. The 6R compound had a poorer uptake into human CCRF-CEM lymphoblastic cells than the 6S compound, but the 6R compound could competitively inhibit the uptake of the natural isomer as determined in defined buffers. However, the 6R compound failed to interfere with cell growth support and enhancement of 5-fluorouracil cytotoxicity by the 6S isomer in CCRF-CEM cells in tissue culture experiments at concentrations up to 1 mM. Thus, the unnatural isomer of 5-formyltetrahydrofolate present in leucovorin preparations seems unlikely to have clinically relevant consequences.

Cell Division↗
PubMed1989

Methenyltetrahydrofolate synthetase prevents the inhibition of phosphoribosyl 5-aminoimidazole 4-carboxamide ribonucleotide formyltransferase by 5-formyltetrahydrofolate polyglutamates.

Methenyltetrahydrofolate synthetase (EC 6.3.3.2) catalyzes the irreversible ATP and Mg2+-dependent transformation of 5-formyltetrahydrofolate (N5-HCO-H4-pteroylglutamic acid (PteGlu] to 5,10-methenyltetrahydrofolate. The physiological function of this reaction remains unknown even though it is potentially involved in the intracellular metabolism of the large doses of N5-HCO-H4-PteGlu (leucovorin) administered to cancer patients. We have tried to elucidate methenyltetrahydrofolate synthetase's physiological role by examining the consequences of its inhibition in MCF-7 human breast cancer cells by the folate analog 5-formyltetrahydrohomofolate (fTHHF), a potent competitive inhibitor with a Ki of 1.4 microM. fTHHF inhibited MCF-7 cell growth with an IC50 of 2.0 microM during 72-h exposures, and this effect was fully reversible by hypoxanthine but not thymidine, indicating specific inhibition of de novo purine synthesis. A correlation was observed between increases in intracellular N5-HCO-H4-PteGlu concentrations following fTHHF and cell growth inhibition. De novo purine synthesis was inhibited at the second folate-dependent enzyme, phosphoribosyl aminoimidazole-carboxamide formyltransferase (AICAR transferase; EC 2.1.2.3), as determined by aminoimidazole carboxamide rescue and azaserine inhibition studies. N5-HCO-H4-PteGlu pentaglutamate was a potent inhibitor of purified MCF-7 cell AICAR transferase with a Ki of 3.0 microM while the monoglutamate was not an inhibitor up to 10 microM and fTHHF was only weakly inhibitory with a Ki of 16 microM. These findings suggest that methenyltetrahydrofolate synthetase activity is needed to prevent de novo purine synthesis inhibition by N5-HCO-H4-PteGlu polyglutamates.

Acyltransferases↗