Safety and efficacy of oral anticoagulants in extreme weights.

BACKGROUND: The 2021 International Society on Thrombosis and Haemostasis' (ISTH) recommends standard doses of apixaban and rivaroxaban regardless of high body mass index (BMI) and weight, but had not compare DOACs head-to-head in obesity or address underweight patients. METHODS: Our aim is to evaluate the safety and efficacy of DOACs in underweight and obese patients compared to warfarin. The primary endpoints include incidence of thromboembolic and bleeding events. Descriptive statistics was used for continuous variables. The Kruskal-Wallis test was used to compare the four-groups for continuous measures and the chi-square test or Fisher's exact test was used to analyze categorical data. The chi-square test or Fisher's exact test, was used for categorical variables, and the Mann-Whitney test (the non-parametric counterpart to the two-sample t-test) for continuous data. RESULTS: Of 2940 patients receiving anticoagulation for venous thromboembolism (VTE) treatment or atrial fibrillation (AF), 492 met eligibility criteria. Within each group, 248 patients received warfarin, 101 received apixaban, 100 received rivaroxaban and 43 received dabigatran. Patients were characterized in 4 body mass index (BMI) categories, in which 80 were underweight and 412 were obese. CONCLUSIONS: When each DOAC was compared to warfarin in rates of VTE, apixaban showed statistically significant lower rate of VTE (p = 0.0149). However, no statistical significance was identified in the rate of VTE between DOACs combined vs. warfarin (p = 0.1529). When each DOAC was compared to warfarin, apixaban showed the lowest rate of overall bleeding (p = 0.0194). However, no statistical difference in the rate of bleeding was observed between DOACs combined vs. warfarin (p = 0.3284). Patients with extreme body weights requiring anticoagulation for VTE and AF may safety benefit from DOAC therapy. This evaluation showed apixaban with the lowest rate of VTE and bleeding compared to warfarin, rivaroxaban, and dabigatran. These results provide experience for the clinician to use DOACs, particularly apixaban, in underweight and obese populations.

Complete and sustained remission of refractory cervical cancer following a single cycle of capecitabine. A case report.

Cervical cancer with distant metastasis is almost always incurable. The treatment goal is to palliate the patient's symptoms with pain medications and localized radiation therapy. Chemotherapy generally has a limited role, with responses that are short lived. Newer agents investigated as potential therapy include fluorouracil prodrugs. We report on a case where capecitabine was used in metastatic cervical cancer with progression of disease outside the radiation field, following multiple drug regimens including one dose of cisplatin (discontinued due to transient renal toxicity), paclitaxel, and carboplatin and continuous infusion 5-fluorouracil (5-FU) The patient was treated with capecitabine 1100 mg/m2 twice daily for two weeks. After the first week of the cycle, the patient developed grade 2 toxicities consisting of mucositis and hand-foot Syndrome but she continued on therapy through day 14. On day 20 she was hospitalized with grade 4 toxicity, which included febrile neutropenia, urinary tract infection, pancytopenia, mucositis, hand-foot syndrome, and renal failure, all of which have subsequently completely resolved. Restaging demonstrated complete remission. Although the patient suffered toxicity related to capecitabine, 3.5 years post a single cycle of capecitabine, the patient remains in remission, with no evidence of disease reoccurence.

Sustained complete remission in a patient with platinum-resistant ovarian yolk sac tumor.

BACKGROUND: Yolk sac tumors of the ovary are generally very responsive to chemotherapy; however, they are difficult to manage in the setting of platinum resistance where treatment options are limited and outcomes are poorer. CASE: We present a 39-year-old woman who had a platinum-resistant yolk sac ovarian tumor. She achieved complete remission on an innovative regimen of docetaxel, gemcitabine, and thalidomide. CONCLUSION: The combination of docetaxel, gemcitabine, and thalidomide might be an active regimen for platinum-resistant ovarian nondysgerminomas and further investigation of this combination is warranted.

Late recurrence in ovarian dysgerminoma with successful response to standard adjuvant chemotherapy: a case report and review of the literature.

BACKGROUND: Ovarian dysgerminomas are quite amenable to treatment and very good cure rates are achieved even with advanced disease. However, recent literature suggests that late recurrence may be associated with a poorer prognosis and bleomycin/etoposide/cisplatin (BEP) chemotherapy may play only a limited role in its management. We present a patient who had a late recurrence of ovarian dysgerminoma with successful treatment outcome. CASE: A 25-year-old woman was diagnosed with a stage IC ovarian dysgerminoma in 1983 and did not undergo adjuvant treatment. She had late recurrence 12 years later with good treatment response to BEP chemotherapy given in a semiadjuvant fashion. CONCLUSION: Our case demonstrates that BEP chemotherapy still plays an important role in treatment of late recurrence in ovarian dysgerminomas provided there is small volume disease at time of detection. Also important is long-term surveillance in an effort to detect recurrence while still small in volume and potentially curable.

Identification of a malignant counterpart of the monocyte-dendritic cell progenitor in an acute myeloid leukemia.

Myeloblasts derived from the peripheral blood of a patient with acute myelogenous leukemia (ORL47) were found to represent the malignant counterpart of the newly elucidated monocyte-dendritic cell colony-forming unit (mono-DC-CFU). The specific cytokine conditions require to achieve intermediate and terminal maturation of DCs and monocytes from these progenitors were defined. With tumor necrosis factor (TNF) + granulocyte-macrophage colony-stimulating factor (GM-CSF) + stem cell factor treatment numerous colony-like clusters developed. In contrast with normal DC development, further advancement of mono-DC-CFU and terminal DC maturation from the leukemic cells were dependent on the addition of interleukin-6. Functional and phenotypic analysis showed that the capacity to differentiate was maintained fully in the DC compartment, but only partially in the monocyte compartment, as judged by the lack of CD14 surface expression. Cells found at intermediate stages of DC development were potent stimulators of a mixed leukocyte reaction, a function usually attributed to mature DCs. As previously shown for normal DC development, antibodies to TNF alpha and GM-CSF blocked proliferative responses and DC growth. The importance of these observations in the classification of leukemias, normal DC development, and potential clinical strategies is discussed.

A phase I study of a combination of allopurinol, 5-fluorouracil and leucovorin followed by hydroxyurea in patients with advanced gastrointestinal and breast cancer.

Twenty patients with advanced carcinomas of the colorectum, pancreas, stomach, and breast were enrolled in a Phase I study of a sequential administration of 5-fluorouracil-leucovorin (FU-LV) combination followed by hydroxyurea (HU) with allopurinol protection (HALF regimen). As a weekly regimen for 6 weeks, followed by a rest period of 2 weeks, FU was administered intravenously (i.v.) during infusion of a 2-hour i.v. infusion of LV at a dose of 500 mg/m2. Six hours following the FU-LV combination, HU (1 gm/m2) was administered orally. Allopurinol (300 mg every 8 hours, orally) was given the day before and on the day of the administration of the FU-LV combination. The starting dose of FU was 300 mg/m2, with escalations to 900 mg/m2. Mucositis, diarrhea, and hematologic toxicities were mild and sporadic with FU doses up to 750 mg/m2 and occurred in patients who had received prior treatment with FU and/or radiotherapy. Dose-limiting neurocerebellar toxicity was observed in 2 out of 6 patients who received a FU dose of 900 mg/m2. Three additional patients experienced moderate neuromotor toxicity at this dose level. Among 17 patients evaluable for response, partial responses were seen in 3 of the 9 patients with colorectal cancer, 1 of the 3 patients each with carcinoma of breast and pancreas. Three of the 5 responses occurred in patients who had received prior treatment with FU and/or radiation therapy. An FU dose of 750 mg/m2 is recommended for a Phase II trial of the HALF regimen.

Subcellular distribution of daunorubicin in P-glycoprotein-positive and -negative drug-resistant cell lines using laser-assisted confocal microscopy.

Four well defined multidrug-resistant cell lines and their drug-sensitive counterparts were examined for intracellular distribution of daunorubicin (DNR) by laser-assisted confocal fluorescence microscopy: P-glycoprotein-negative HL-60/AR cells, and P-glycoprotein-positive P388/ADR, KBV-1, and MCF-7/ADR cells. Both drug sensitive cell lines (HL-60/S, P388/S, KB3-1, and MCF-7/S) and drug-resistant cell lines (HL-60/AR, P388/ADR, KBV-1, and MCF-7/ADR) exposed to DNR showed a similar rapid distribution of drug from the plasma membrane to the perinuclear region within the first 2 min. From 2-10 min, the drug sensitive HL-60/S, P388/S, and MCF-7/S cells redistributed drug to the nucleus and to the cytoplasm in a diffuse pattern. In contrast, drug-resistant HL-60/AR, P388/ADR, and MCF-7/ADR redistributed DNR from the perinuclear region into vesicles distinct from nuclear structures, thereby assuming a "punctate" pattern. This latter redistribution could be inhibited by glucose deprivation (indicating energy dependence), or by lowering the temperature of the medium below 18 degrees C. The differences in distribution between sensitive and resistant cells did not appear to be a function of intracellular DNR content, nor the result of drug cytotoxicity. Drug-sensitive KB3-1 and -resistant KBV-1 cells did not fully follow this pattern in that they demonstrated an intracellular DNR distribution intermediate between HL-60/S and HL-60/AR cells with both "punctate" and nuclear/cytoplasmic uptake sometimes in the same cell. These data indicate that the intracellular distribution of DNR is an important determinant of drug resistance regardless of the overexpression of P-glycoprotein. The intracellular movement of drug requires the presence of glucose and a temperature above 18 degrees C, implicating energy-dependent processes and vesicle fusion in the distribution process. This intracellular transport of DNR away from the nucleus in multidrug-resistant cells may protect putative cell targets such as DNA against drug toxicity.

Human leukemic myeloblasts and myeloblastoid cells contain the enzyme cytidine 5'-monophosphate-N-acetylneuraminic acid:Gal beta 1-3GalNAc alpha (2-3)-sialyltransferase.

We have examined the role of CMP-NeuAc:Gal beta 1-3GalNAc-R alpha(2-3)-sialyltransferase in fresh leukemia cells and leukemia-derived cell lines. Enzyme activity in normal granulocytes using Gal beta 1-3GalNAc alpha-o-nitrophenyl as substrate was 1.5 +/- 0.7 nmol/mg/h whereas activity in morphologically mature granulocytes from 6 patients with chronic myelogenous leukemia (CML) was 4.2 +/- 1.6 nmol/mg/h (P less than 0.05). Myeloblasts from 5 patients with CML in blast crisis showed enzyme activity levels of 6.5 +/- 2.5 nmol/mg/h. From 2 patients with CML, both blasts and granulocytes were obtained, with higher enzyme activity in the patients' blasts (7.1 nmol/mg/h) than in their granulocytes (4.9 nmol/mg/h) in both cases, suggesting that the increase in enzyme activity is related to the differentiation or proliferation status of the CML cells. However, similarly high enzyme levels were also seen in myeloblasts from acute myeloblastic leukemia patients (5.6 +/- 1.4 nmol/mg/h) and in some acute myeloblastic leukemia-derived cell lines (KG1a and HL60), suggesting that increased levels of this enzyme are not directly correlated with the presence of the Ph1 chromosome. This alpha(2-3)-sialyltransferase activity can also be detected in normal peripheral blood lymphocytes and exhibits increased activity in chronic lymphocytic leukemia cells and acute lymphoblastic leukemia. These data suggest that the level of enzyme activity may vary with growth rate and maturation status in myeloid and lymphoid hemopoietic cells. Finally, we have identified a glycoprotein in acute myeloblastic leukemia cells that serves as a substrate for the alpha(2-3)-sialyltransferase. The desialylated form of the glycoprotein was resialylated in vitro by the purified placental form of this alpha(2-3)-sialyltransferase and exhibits a molecular weight of about 150,000.

Effect of duration of exposure to verapamil on vincristine activity against multidrug-resistant human leukemic cell lines.

Verapamil sensitizes multidrug-resistant cell lines to various heterocyclic anticancer drugs by inhibition of energy-dependent release of drug, presumably by interaction with membrane glycoproteins involved in drug efflux. This work assessed verapamil sensitization of human multidrug-resistant lymphocytic and myeloid leukemic cell lines (CEM/VLB100, HL-60/AR) to vincristine during exposures of short duration (4 h). When cells were transferred to drug-free medium immediately after simultaneous 4-h exposures to vincristine and verapamil, the antiproliferative activity of vincristine was not altered in CEM/VLB100 cells and was only moderately increased in HL-60/AR cells. In contrast, when cells were transferred to verapamil-containing medium, vincristine activity was greatly increased against both CEM/VLB100 and HL-60/AR cells. Verapamil enhanced accumulation and inhibited release of [3H]vincristine by CEM/VLB100 and HL-60/AR cells, indicating that the sensitization was due to an increase in cell-associated vincristine after transfer of cells to vincristine-free medium. Slot blot analysis of cellular RNA with the pMDR1 probe revealed high levels of expression of the mdr1 gene in CEM/VLB100 cells but no detectable expression in HL-60/AR cells. Consistent with this finding, polypeptides (Mr 170,000 to 180,000) that were recognized by a monoclonal antibody (C219) against P-glycoprotein were greatly overexpressed in CEM/VLB100 cells, but were expressed at low levels, if at all, in HL-60/AR cells. These results demonstrate the importance of duration of exposure to verapamil in reversing multidrug resistance, not only in cells that overexpress P-glycoprotein but also in cells, such as HL-60/AR, that express little, if any, P-glycoprotein.

Intracellular distribution and pharmacokinetics of daunorubicin in anthracycline-sensitive and -resistant HL-60 cells.

Anthracycline-sensitive (HL-60) and -resistant (HL-60/AR) cells, which do not overexpress the P-glycoprotein, each transport and distribute daunorubicin (DNR) into distinct intracellular locations, as visualized by digitized video fluorescence microscopy. At pH 7.4, the fluorescence of DNR in HL-60 cells appears distributed diffusely in both the nucleus and cytoplasm. In contrast, HL-60/AR cells show much less fluorescence in the nucleus and cytoplasm; most of the fluorescence localizes first to the Golgi apparatus and is then gradually shifted to the lysosomes and/or mitochondria. In pharmacokinetic studies, HL-60/AR cells exposed to different extracellular concentrations of [14C]DNR consistently accumulated less radioactive drug than the parent HL-60 cells. Incubation of HL-60/AR cells with sodium azide and deoxyglucose blocked the efflux of [14C]DNR and also prevented the shift of DNR fluorescence from the Golgi apparatus to the lysosomes/mitochondria. The efflux and the intracellular shift of DNR could also be inhibited by lowering the temperature to 18 degrees C, which stops endosomal membrane fusion. When DNR was allowed to accumulate in HL-60 or HL-60/AR cells at pH 5 there was an increase in the proportion of drug fluorescence in the membranes of both HL-60 and HL-60/AR cells; a decrease in the amount of drug retained by HL-60, but not by HL-60/AR cells; and a decrease in the cytostatic effects of DNR on both HL-60 and HL-60/AR cells. These data suggest that DNR resistance is associated with a failure of DNR to pass through membranes and to bind to cytoplasmic and nuclear structures. Instead, most of the drug is taken up by the Golgi apparatus from which it is then shifted to the lysosomes or to mitochondria, or out of the cell.

Role of glutathione and dependent enzymes in anthracycline-resistant HL60/AR cells.

We studied the cellular enzymatic defenses against anthracycline-induced free radical damage in the HL60 human myelogenous leukemia cell line and in its anthracycline-resistant subline, HL60/AR. Intracellular glutathione (GSH) levels and gamma-glutamyl transpeptidase activity were lower in HL60/AR than in HL60 cells. Glutathione-S-transferase (GST) and glutathione peroxidase activities were similar in both cell lines. The intracellular distribution of GSH/GST was visualized by digitized video fluorescence microscopy, utilizing the fluorescent probe monochlorobimane fluorescence microscopy, utilizing the fluorescent probe monochlorobimane (MBCl), which is specifically conjugated to GSH by GST. In HL60 cells stained with the MBCl probe, a bright diffuse cytoplasmic and nuclear fluorescence pattern was observed, whereas in HL60/AR cells, the fluorescence was mostly localized to the Golgi apparatus with a lesser component of diffuse cytoplasmic and nuclear fluorescence. Pretreatment of HL60/AR cells with buthionine sulfoximine (BSO) partially reversed resistance to daunorubicin. This effect of BSO on resistance was associated not only with the abolition of localized MBCl fluorescence to the Golgi apparatus but also with increased intracellular accumulation and retention of daunorubicin. The results of our studies demonstrate that inhibition of GSH synthesis in HL60/AR cells results in significant sensitization to daunorubicin and suggest that changes in the intracellular distribution of GSH/GST and/or increased drug retention may be involved in mediating this effect.

Presence of cytidine 5'-monophospho-N-acetylneuraminic acid:Gal beta 1-3GalNAc-R alpha(2-3)-sialyltransferase in normal human leukocytes and increased activity of this enzyme in granulocytes from chronic myelogenous leukemia patients.

We have examined granulocytes from patients with chronic myelogenous leukemia (CML) and from normal subjects to determine whether activity of a specific sialyltransferase might account for the aberrant sialylation of O-linked membrane oligosaccharides in CML cells. Total membrane preparations of morphologically mature CML and normal granulocytes were tested for sialyltransferase activity using the substrates galactosyl-beta 1-3-N-acetyl-D-galactosamine-alpha-O-nitrophenyl and N-acetyl-D-galactosamine-alpha-phenyl. N-Acetyl-D-galactosamine-alpha-phenyl was not an acceptor with either CML or normal cells. With galactosyl-beta 1-3-N-acetyl-D-galactosamine-alpha-O-nitrophenyl, sialyltransferase activity was 2.8 times higher in CML cells compared to normal cells. Product identification by high performance liquid chromatography showed that enzyme from both normal and CML granulocytes linked sialic acid to galactosyl-beta 1-3-N-acetyl-D-galactosamine-R by the alpha(2-3) and not the alpha(2-6) linkage. The enzyme CMP-N-acetylneuraminic acid: galactosyl-beta 1-3-N-acetyl-D-galactosamine-R alpha(2-3)-sialyltransferase has not previously been described in human granulocytes. The marked increase in activity of this enzyme in CML and the resulting increase in sialylation may contribute to the pathophysiological behavior of CML granulocytes.

Effect of verapamil and other agents on the distribution of anthracyclines and on reversal of drug resistance.

We studied the intracellular distribution of drugs within anthracycline-sensitive and -resistant cells by computer-assisted digitized video fluorescence microscopy. We found that the antitumor antibiotic, daunorubicin, distributes differently in anthracycline-sensitive and -resistant human leukemia cells (HL-60). Verapamil and other agents known to circumvent resistance in pleiotropic drug-resistant cell lines were able to change the pattern of distribution of daunorubicin in the anthracycline-resistant HL-60 cells back to the distribution found in anthracycline-sensitive HL-60 cells. To investigate the biochemical basis for this effect, we studied the distribution of daunorubicin and doxorubicin in a hydrophobic/hydrophilic (membrane/cytoplasmic) environment using the two-compartment cell-free system of Folch. Our results demonstrate that various unrelated drugs known to overcome resistance will also change the distribution of the anthracyclines in the hydrophobic/hydrophilic compartments. Our data allow the hypothesis that various unrelated agents known to circumvent resistance may act by altering the hydrophobic/hydrophilic solubility of anthracyclines in the resistant cell.

Changes in the granulocyte membrane following chemotherapy for chronic myelogenous leukaemia.

Granulocytes from patients with chronic myelogenous leukaemia (CML) have been previously shown to have aberrant sialylation of membrane glycoproteins. We have examined the granulocytes from CML patients receiving intermittent chemotherapy to determine the relationship of the oligosaccharide changes to treatment. Compared to cells from non-leukaemic patients, granulocytes from untreated CML patients showed less adherence to nylon wool, decreased reactivity with peanut lectin, and decreased binding of the synthetic chemotactic peptide formyl-methionine-leucine-phenylalanine (FMLP). Granulocytes from CML patients treated with chemotherapy showed nylon wool adherence, peanut lectin reactivity and FMLP binding comparable to non-leukaemic cells. Chemotherapeutic agents may interfere with oligosaccharide synthesis with a resulting change in the composition of cell surface glycoconjugates.

Increased activity of a specific sialyltransferase in chronic myelogenous leukemia.

Granulocytes from patients with chronic myelogenous leukemia (CML) are morphologically identical to their normal counterparts but show marked differences in circulation patterns and in some membrane properties. We have previously shown that there is abnormal lectin binding to CML granulocytes, and aberrant sialylation of membrane glycoproteins. To examine the changes in sialylation of CML granulocytes further, we have studied membrane preparations from CML and normal granulocytes for specific sialyltransferase activity. Because sialyltransferase enzymes are specific for the configuration of the acceptor group, enzyme activity was assayed by measuring transfer of sialic acid from CMP-14C-sialic acid to substrates of defined structure. As compared with those of normal counterparts, CML extracts catalyzed a 50% higher overall rate of sialylation of asialofetuin, a substrate possessing both N- and O-linked acceptors. Studies of enzyme specificity utilizing porcine and ovine submaxillary mucins, antifreeze glycoprotein and alpha-1 acid glycoprotein as acceptors showed that the increased sialylation by CML extracts was due primarily to substrates with the O-linked Gal beta 1----3GaINAc acceptor group. These data suggest that sialyltransferase activity is increased in CML granulocytes compared to normal granulocytes and that the increased enzyme activity is specific for O-linked Gal beta 1----3GaINAc. This enzyme activity may be directly responsible for the abnormal membrane sialylation and pathophysiological behavior of these cells.

Isolation and characterization of an anthracycline-resistant human leukemic cell line.

An anthracycline-resistant subline of HL-60 promyelocytic leukemia cells (HL-60/AR) has been isolated in vitro by subculturing in progressively higher concentrations of Adriamycin. The resistant cells are capable of sustaining continuous growth in 10(-6) M Adriamycin which is more than 50 times the 50% inhibitory dose for the parent line. HL-60/AR expressed variable degrees of cross-resistance to daunorubicin, dihydroxyanthracenedione, vincristine, vinblastine, and actinomycin D, but it remained sensitive to methotrexate and 1-beta-D-arabinofuranosylcytosine. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of glycoproteins of HL-60/AR revealed two prominent glycoproteins with molecular weights of 160,000 +/- 10,000 and 110,000 +/- 10,000 which were not detected in the sensitive cells. Cellular uptake and retention of daunorubicin was studied in the resistant and sensitive cells utilizing digitized video fluorescence microscopy. The sensitive cells accumulated more drug and showed at least 2-fold greater levels of brightness than the resistant cells. Studies of total intracellular accumulation, utilizing 10(-6) M [14C]-daunorubicin as a marker, showed a 1-h accumulation of 98 +/- 20 pmol/10(6) cells in HL-60/AR versus 255 +/- 25 pmol/10(6) cells in HL-60. Exposure to nontoxic concentrations of the calcium channel blocker Verapamil (10(-5) M) led to enhanced accumulation (175 +/- 8 pmol/10(6) cells) and retention of the drug in HL-60/AR, resulting in increased cytotoxicity in HL-60/AR. These anthracycline-resistant leukemic cells may serve as a valuable experimental model in studying the phenomenon of multiple drug resistance as well as strategies to circumvent it in human myeloid leukemia.

Effects of pyrimidine antagonists on sialic acid regeneration in HL-60 cells.

Because alterations in cell membrane sialoglycoconjugates can affect the behavior of neoplastic cells, we investigated the effects of in vitro treatment with antimetabolites used in cancer therapy on the expression of membrane sialic acid in cultured HL-60 leukemic cells. In these studies, cells were incubated with Vibrio cholerae neuraminidase to remove surface sialic acid. Reappearance of membrane sialic acid during drug treatment was followed (a) by measuring changes in radioactive surface labeling of viable cells with sodium metaperiodate-sodium[3H]-borohydride, (b) by measuring the decline in accessible surface galactosyl receptor sites which occurred coincident with membrane sialic acid replacement, and (c) by measuring the incorporation of [3H]glucosamine into membrane-associated neuraminidase-labile sialic acid. We were especially interested in learning whether drugs that affect intracellular pools of cytidine triphosphate (CTP), an important nucleotide intermediate in sialylation reactions, could inhibit regeneration of membrane sialic acid. 3-Deazauridine, a competitive inhibitor of CTP synthetase, depleted CTP pools and curtailed surface membrane resialylation with little or no effect on synthesis of de novo sialic acid from precursor sugars. The addition of cytidine restored CTP pools and sialic acid regeneration. Acivicin, a glutamine antagonist, also depleted CTP pools and curtailed surface membrane resialylation. In addition, it retarded de novo synthesis of sialic acid. The addition of cytidine restored intracellular CTP pools and sialic acid regeneration. However, both cytidine and guanosine were required to restore sialic acid synthesis from precursor sugars. 1-beta-D-Arabinofuranosylcytosine, a competitive inhibitor of sialic acid synthetase and of sialyltransferase, inhibited both de novo sialic acid synthesis and membrane resialylation. Only the latter effect was reversed by the addition of exogenous cytidine. Hydroxyurea, an agent shown previously to inhibit glycoconjugate production in hamster fibroblasts, curtailed membrane resialylation and de novo synthesis of sialic acid without depleting CTP pools. Doxorubicin, at levels that caused marked arrest of cell proliferation, had no effect on sialic acid synthesis or expression on the membrane surface. These data suggest that antimetabolites, apart from their cytotoxic effects or effects on cellular growth, may directly inhibit the expression of membrane sialic acid.(ABSTRACT TRUNCATED AT 400 WORDS)

Regeneration of membrane sialic acid after neuraminidase treatment of leukemic granulocytes.

Granulocytes from patients with chronic myelogenous leukemia (CML) were studied for their ability to regenerate surface sialic acid following treatment with Vibrio cholera neuraminidase (VCN) in vitro. Immediately after neuraminidase treatment, CML and normal granulocytes showed similar incorporation of radioactivity after surface labelling with sodium periodate/potassium-H3-borohydride (PI/BH3(4)). CML granulocytes treated with neuraminidase then incubated for 18 h in nutrient medium showed strikingly increased PI/BH3(4) labelling, usually greater than initial pretreatment values, consistent with a rapid reappearance of sialic acid in the cell membrane. This pattern was not seen in normal granulocytes. The aberrant regeneration of sialic acid in CML granulocytes in vitro could be inhibited by addition of 3 X 10(-6) M retinoic acid, suggesting either a direct effect on membrane glycoconjugate synthesis or an association with granulocyte differentiation.

Aberrant sialylation of granulocyte membranes in chronic myelogenous leukemia.

Peripheral blood granulocytes from patients with chronic myelogenous leukemia (CML) were studied for accessibility of membrane sialic acid and galactose residues to sodium borohydride-3H radiolabeling after oxidation with sodium metaperiodate (PI/B3H4) or with galactose oxidase (GO/B3H4). Granulocytes from untreated patients with chronic myelogenous leukemia showed increased radiolabeling with PI/B3H4, and decreased labeling with GO/B3H4 when compared to normal granulocytes. Granulocytes from leukemic patients receiving chemotherapy showed normal labeling patterns. Gel electrophoresis of membrane extracts showed that the changes in PI/B3H4 and GO/B3H4 reactivity of CML cells were distributed over all membrane protein bands. Our data suggest that CML granulocyte membrane proteins are aberrantly sialylated, with decreased accessibility of galactose residues, and that these changes may be reversed by clinical drug treatment.