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R L Fine

Publications and source records attributed to R L Fine.

At least 55 records · Page 3Linked to original sources
PubMed1991

Multidrug resistance in MCF-7 human breast cancer cells is associated with increased expression of nucleoside transporters and altered uptake of adenosine.

The rate of adenosine uptake and the corresponding expression of nucleoside transporters were studied in several MCF-7 human breast-cancer cell lines that express different levels of multidrug resistance (MDR). Kinetic studies of adenosine transport in these cell lines revealed that the mean apparent Km and Vmax values for the nucleoside transporters increased with increasing MDR. The apparent Km and the apparent Vmax of Adriamycin-resistant (ADR10) cell lines were respectively 3.2- and 1.8- fold those of Adriamycin-sensitive wild-type (WT) cells (P less than 0.001). A partially revertant cell line (ADR10rev) that was derived from the ADR10 line and was partially sensitive to Adriamycin exhibited apparent Km and Vmax parameters that lay between those of the ADR10 and WT cells (P less than 0.001 vs ADR10 cells; P less than 0.05 vs WT cells). ADR10 cell membranes bound greater than 4 times more of the nucleoside transporter blockers [3H]-nitrobenzylthioinosine [( 3H]-NBI) and [3H]-dipyridamole [( 3H]-DPR) than did WT cell membranes per unit protein (P less than 0.0001). Scatchard analysis revealed a 2-3 times greater density for nucleoside transporters in ADR10 membranes as compared with those in WT membranes. ADR10rev membranes bound less [3H]-NBI and [3H]-DPR than did ADR10 membranes (P less than 0.001), but they bound more of the blockers than did WT membranes (P less than 0.05). A 2.5-h exposure to 200 nM phorbol-12,13-dibutyrate (PDBu), which activates protein kinase C (PKC) and induces WT cells to exhibit a 4-fold increased transient MDR phenotype, increased the apparent Km of WT cells for adenosine transport by greater than 2 times (P less than 0.001) to a value close to that found for the ADR10 cells. An identical exposure of ADR10 cells to PDBu produced no significant effect. The apparent Km of ADR10rev cells was increased 1.4 times by a 2.5-h PDBu exposure. None of the cell lines were affected by a 2.5-h exposure to 200 nM phorbol-13,10-diacetate (PDA), a much less active phorbol, or vehicle. These results suggest that MDR in MCF-7 cells is associated with changes in nucleoside transport, including both the number of transporters and their rate of transport, and that such changes can be partially mimicked by stimulation of PKC.

Adenosine↗
PubMed1991

Personal choices--communication among physicians and patients when confronting critical illness.

Communication among physicians and patients when confronting life-threatening or terminal illness is often flawed. Medical ethics authorities have suggested the physician or the hospital is responsible to determine a patient's wishes for ongoing therapy; yet, few pragmatic suggestions have been made as to how to fulfill this responsibility. Although advance directives are generally available, they are often misunderstood and rarely used. An educational brochure has been designed to facilitate communication by exposing patients and others to some of the technical and ethical issues that come into focus in the setting of critical illness. The brochure includes a living will. Early experience with this device has been favorable. The hospital ethics committee that developed this brochure believes it can be adapted to other institutions and urges its widespread use.

Choice Behavior↗
PubMed1990

In vitro inhibition of the infectivity and replication of human immunodeficiency virus type 1 by combination of antiretroviral 2',3'-dideoxynucleosides and virus-binding inhibitors.

We tested the in vitro inhibitory activities of three 2',3'-dideoxynucleosides and two inhibitors of viral binding in combinations against the infectivity and cytopathic effect of human immunodeficiency virus type 1. 3'-Azido-2',3'-dideoxythymidine, 2',3'-dideoxyinosine, or 2',3'-dideoxycytidine, combined with recombinant soluble CD4 (sCD4), brought about synergistic antiretroviral activity without toxicity at clinically achievable concentrations. Combinations of 2',3'-dideoxynucleosides plus dextran sulfate exerted similar synergistic antiviral effects without concomitant increases in toxicities. When sCD4 and dextran sulfate were combined, apparent antagonism was observed. We confirmed that no combination of sCD4 plus 3'-azido-2',3'-dideoxythymidine, 2',3'-dideoxyinosine, or 2',3'-dideoxycytidine significantly increased the inhibitory effect on colony formation of human myeloid-monocytic bone marrow cells in vitro at the concentrations used in this study. These data might have clinical relevance for the treatment of patients infected with human immunodeficiency virus.

Antiviral Agents↗
PubMed1990

Cyclobut-A and cyclobut-G, carbocyclic oxetanocin analogs that inhibit the replication of human immunodeficiency virus in T cells and monocytes and macrophages in vitro.

Two newly synthesized carbocyclic oxetanocin analogs, (+/-)-9-[(1 beta,2 alpha,3 beta)-2,3-bis(hydroxymethyl)-1-cyclobutyl]adenine (cyclobut-A) and (+/-)-9-[(1 beta,2 alpha,3 beta)-2,3-bis(hydroxymethyl)-1-cyclobutyl]guanine (cyclobut-G) were tested for activity against the infectivity of human immunodeficiency virus (HIV) in vitro. A number of other carbocyclic oxetanocin analogs failed to exert good antiretroviral effects. Both cyclobut-A and cyclobut-G protected CD4+ ATH8 cells against the infectivity and cytopathic effect of HIV type 1 (HIV-1) and suppressed proviral DNA synthesis in ATH8 cells exposed to HIV-1 in vitro at concentrations of 50 to 100 microM. These compounds also inhibited the in vitro infectivity of another human pathogenic retrovirus, HIV-2. Furthermore, both compounds completely suppressed the replication of a monocytotropic strain of HIV-1 in monocytes and macrophages at concentrations as low as 0.5 microM, as assessed by inhibition of HIV-1 p24 gag protein production. We also found that 2'-deoxyguanosine readily reversed the antiretroviral activity of cyclobut-G in our system, whereas the activity of cyclobut-A was hardly reversed by 2'-deoxyadenosine or 2'-deoxycytidine. We noted, however, that these compounds inhibited the proliferation of peripheral blood mononuclear cells at concentrations of greater than or equal to 100 microM in vitro. Although both cyclobut-A and cyclobut-G appear to have a certain level of in vitro toxicity, our observations may have theoretical and clinical implications in understanding the structure-activity relationships of antiretroviral agents active against HIV.

Adenine↗
PubMed1989

Dipyridamole potentiates the inhibition by 3'-azido-3'-deoxythymidine and other dideoxynucleosides of human immunodeficiency virus replication in monocyte-macrophages.

Dipyridamole (DPM) is commonly used as a coronary vasodilator and inhibitor of platelet aggregation in the treatment of cardiovascular diseases. We report here that DPM potentiates the inhibitory effects of 3'-azido-3'-deoxythymidine (AZT) and 2',3'-dideoxycytidine against human immunodeficiency virus type 1 (HIV-1) in human monocyte-macrophages. At the same concentrations, DPM does not potentiate the toxic effects of AZT on these cells or on human bone marrow (granulocyte-monocyte) progenitor cells. Since monocyte-macrophage lineage cells appear to be the major reservoir for HIV-1 in vivo, these findings suggest the possibility of using DPM or its analogues in combination chemotherapy of HIV infections.

Antiviral Agents↗
PubMed1988

Phorbol esters induce multidrug resistance in human breast cancer cells.

Mechanisms responsible for broad-based resistance to antitumor drugs derived from natural products (multidrug resistance) are incompletely understood. Agents known to reverse the multidrug-resistant phenotype (verapamil and trifluoperazine) can also inhibit the activity of protein kinase C. When we assayed human breast cancer cell lines for protein kinase C activity, we found that enzyme activity was 7-fold higher in the multidrug-resistant cancer cells compared with the control, sensitive parent cells. Exposure of drug-sensitive cells to the phorbol ester phorbol 12,13-dibutyrate [P(BtO)2] led to an increase in protein kinase C activity and induced a drug-resistance phenotype, whereas exposure of drug-resistant cells to P(BtO)2 further increased drug resistance. In sensitive cells, this increased resistance was accompanied by a 3.5-fold increased phosphorylation of a 20-kDa particulate protein and a 35-40% decreased intracellular accumulation of doxorubicin and vincristine. P(BtO)2 induced resistance to agents involved in the multidrug-resistant phenotype (doxorubicin and vincristine) but did not affect sensitivity to an unrelated alkylating agent (melphalan). The increased resistance was partially or fully reversible by the calcium channel blocker verapamil and by the calmodulin-antagonist trifluoperazine. These data suggest that stimulation of protein kinase C plays a role in the drug-transport changes in multidrug-resistant cells. This may occur through modulation of an efflux pump by protein phosphorylation.

Antineoplastic Agents↗
PubMed1988

Multidrug resistance.

The understanding of the mechanism(s) of multidrug resistance has increased at a rapid rate over the past year. Many new inhibitors, new agents equitoxic to MDR and sensitive cells, techniques for screening, and application to therapies will no doubt be within the grasp of the clinical oncologist over the next few years. However, whether in-vitro MDR is synonymous with clinical resistance is still an unanswered question, and other forms of resistance may be co-existing in patient tumors.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1987

Increased fragile sites and sister chromatid exchanges in bone marrow and peripheral blood of young cigarette smokers.

Cigarette smoking is considered to be the single most important acquired cause of cancer mortality. Studies of chromosome aberrations, sister chromatid exchanges, and fragile sites in peripheral blood or bone marrow are useful methods to detect the effects of the environmental mutagens or carcinogens found in cigarette smoke. The effects of smoking on the immature cells in the bone marrow have not been studied. Here, we examine the peripheral blood and bone marrow in 18 smokers (15 females and 3 males) with a median age of 25 years (range, 21-40) and an average cigarette use corresponding to 6 pack years. In both bone marrow cells and peripheral blood lymphocytes, we were able to show a significantly increased frequency of sister chromatid exchanges in smokers with a 5 or more cigarette pack year history, but not in those who smoked less than 5 pack years. We also found a higher frequency of sister chromatid exchanges in peripheral blood lymphocytes than in bone marrow cells. In addition, the peripheral lymphocytes of smokers demonstrated (a) a significantly higher frequency of fragile sites, (b) an increased number of metaphases with extensive breakage; and (c) elevated expression of fragile sites at the cancer breakpoints 3p14.2, 11q13.3, 22q12.2, and 11p13-p14.2 and at the oncogene sites bcl 1, erb B, erb A, and sis. Our results suggest that chromosomal DNA of peripheral blood lymphocytes is sensitive to cigarette smoking. Studies of the chromosomal changes in these cells provide an index of the mutagenic damage caused by these exogenous agents in individual patients and the ability of individuals to repair that damage, and might predict susceptibility to malignant events.

Adult↗
PubMed1987

Enhanced melphalan cytotoxicity in human ovarian cancer in vitro and in tumor-bearing nude mice by buthionine sulfoximine depletion of glutathione.

The development of acquired resistance to alkylating agents frequently limits the effectiveness of chemotherapy in the treatment of ovarian cancer. While the resistance to alkylating agents is multifactorial, the association of drug resistance with elevations in glutathione (GSH) is of potential clinical relevance since there exist pharmacologic means to lower intracellular GSH levels. We have used in vitro and in vivo models of human ovarian cancer to demonstrate that selective inhibition of GSH synthesis with L-buthionine-S,R-sulfoximine (L-BSO) leads to a lowering of GSH levels and an increase in cytotoxicity of the alkylating agent melphalan. In the human ovarian cancer cell line NIH:OVCAR-3, derived from a patient clinically refractory to alkylating agents, L-BSO resulted in a 3.6-fold enhancement of melphalan cytotoxicity. This cell line was also adapted for intraperitoneal growth in athymic nude mice. In this in vivo model, in which the mice die of massive ascites and intraabdominal carcinomatosis, L-BSO given orally in drinking water for 5 days decreased GSH levels in the tumor cells by 96% compared to a 79 and 86% reduction in GSH levels in the bone marrow and gastrointestinal mucosa respectively. Lowering of GSH levels with BSO was not accompanied by an increase in lethality for melphalan in non-tumored nude mice. However, in tumor-bearing nude mice, a single melphalan (5 mg/kg) treatment following GSH depletion with L-BSO was markedly superior to treatment with melphalan alone, producing a 72% increase in median survival time. Furthermore, L-BSO treatment of human bone marrow cells prior to melphalan exposure had little effect on melphalan toxicity as assessed in a CFUc-GM assay. These results suggest that treatment with the GSH synthesis inhibitor BSO may preferentially enhance the cytotoxic effects of alkylating agents against human ovarian cancer and overcome acquired resistance.

Animals↗
PubMed1987

Effect of methotrexate on intracellular folate pools in purified myeloid precursor cells from normal human bone marrow.

We investigated the effects of the antifolate methotrexate on intracellular folate pools of human myeloid precursor cells (MPCs). Immature MPCs, representing 3.2% of the original marrow population, were selected from normal human bone marrow by immune rosetting. The intracellular folate pools were labeled by incubation with 5 X 10(-8) M [3H]5-formyl-FH4 and were quantitated by high performance liquid chromatography. The predominant folates were 5-methyl-tetrahydrofolate (5-methyl-FH4) (36%), 10-formyl-FH4 (41.4%), 5-formyl-FH4 (12.3%), and FH4 (10.3%). A 12-h exposure to 1 microM methotrexate (MTX) resulted in a 34% reduction in the intracellular concentration of 10-formyl-FH4, a 61% decrease in 5-formyl-FH4, and a 62% decrease in 5-methyl-FH4, as well as the appearance and progressive expansion of the FH2 and 10-formyl-FH2 pools. These changes were maximal after 4 h of incubation with MTX. Paralleling the changes in folates, particularly the increase in FH2, were a 64% reduction in myeloid colony formation and a 77% depression of de novo purine synthesis after 4 h of MTX. We conclude that MTX does not produce quantitative depletion of 10-formyl-FH4 and that its antipurine effect may be mediated by direct inhibition of de novo purine synthesis by FH2 and, at later time points, by MTX polyglutamates.

Bone Marrow Cells↗
PubMed1987

Effect of calcium channel blockers on human CFU-GM with cytotoxic drugs.

Calcium channel blockers (CCBs) such as verapamil and nitrendipine are capable of increasing drug sensitivity in resistant murine and human tumor cells. This finding has potential value in the treatment of acquired drug resistance in human malignancies. Thus, we tested the ability of CCBs of two different structural classes to enhance the toxicity of doxorubicin (DOX), vinblastine (VBL), and vincristine (VCR) for normal myeloid and macrophage colony formation (marrow colony forming units-granulocyte-monocyte [CFU-GM]). Drug effects on colony formation from 35 normal volunteer marrows and from seven patient marrows in the recovery phase after cytotoxic chemotherapy were determined. No enhancement of toxicity was mediated by verapamil or nitrendipine when these drugs were co-incubated with the cytotoxic drugs for one hour or 24 hours before plating marrow cells in a semisolid agar system.

Adolescent↗
PubMed1987

Multidrug resistance.

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ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1986

The effect of methotrexate on intracellular folate pools in human MCF-7 breast cancer cells. Evidence for direct inhibition of purine synthesis.

This report details the effects of methotrexate on the intracellular folate pools of the MCF-7 human breast cancer cell line. To achieve this goal, we designed a high-pressure liquid chromatography system capable of separating the physiologic folates. The folate pools were quantitated following growth and equilibration in 2.25 microM radiolabeled folic acid. Each of the intracellular folates was identified by coelution with standard folates and by chemical/biochemical tests unique to each of the various folates. The 10-formyl-H4PteGlu (where H4PteGlu represents dl-tetrahydrofolic acid) pool accounted for 20.5% of the total intracellular folate pool in untreated cells, whereas 5-formyl-H4PteGlu and H4PteGlu accounted for 6.5 and 10.6%, respectively. The levels of these three folates remained stable throughout cell growth. The 5-methyl-H4PteGlu pool accounted for less than 10% in early growth phase cells but assumed greater than 60% of the total pool by the mid- and late-log phases of cell growth. When the MCF-7 cells were exposed to 1 microM methotrexate, de novo purine synthesis and de novo thymidylate synthesis were rapidly inhibited to less than 20% of control within 3 h. During this time period, rapid alterations in the folate pools also occurred such that dihydrofolic acid levels rose from less than 1% in untreated cells to greater than 30% of the total pool. This rise was accompanied by a parallel fall in 5-methyl-H4PteGlu. H4PteGlu and 5-formyl-H4PteGlu were undetectable following 2 h of methotrexate exposure, but 10-formyl-H4PteGlu, the required cosubstrate for de novo purine synthesis, was preserved at greater than 80% of pretreatment values following a 1 microM methotrexate exposure of up to 21 h. The rapid inhibition of de novo purine synthesis in these cells following methotrexate exposure coupled with a relatively preserved 10-formyl-H4PteGlu pool suggests direct inhibition of this synthetic pathway by the temporally coincident accumulation of dihydrofolic acid and/or methotrexate polyglutamates. This inhibition cannot be ascribed to depletion of the folate cofactor 10-formyl-H4PteGlu.

Breast Neoplasms↗
PubMed1985

Phase I and pharmacokinetic study of tiazofurin (TCAR, NSC 286193) administered by continuous infusion.

Tiazofurin (2-beta-D-ribofuranosylthiazole-4-carboxamide, TCAR) is a synthetic C-nucleoside that demonstrated significant in vivo activity against a variety of animal tumors as well as in vitro activity against human tumor-derived cell lines. Thirteen patients were treated with TCAR administered as a 5-day continuous infusion in this Phase I trial. Seventeen complete cycles were administered in three dose levels ranging from 550 to 1450 mg/M2. Dose-limiting toxicities were myelosuppression and neurotoxicity including severe lethargy. Other toxicities including superficial skin peeling, myalgias, and tearing were seen at all doses. One patient had chest pain on day 4 resulting in stopping the drug, however, there was no evidence of cardiac or pericardial disease. Uric acid levels rose within one day in the absence of allopurinol treatment. There were no treatment related deaths. HPLC measurement of drug levels demonstrated steady-state plasma levels during the infusion, and a half-life following the infusion of 7.7 +/- 0.6 hours. Minor abnormalities in renal function were associated with dramatic changes in pharmacokinetics and toxicity. No clinical responses were observed in this trial.

Adult↗
PubMed1985

Clinical pharmacology of high-dose cisplatin.

Although nephrotoxicity has frequently limited conventional treatment with cisplatin to doses of 100-120 mg/m2 per cycle, vigorous chloruresis can permit the administration of high-dose cisplatin (200 mg/m2 per cycle) with minimal nephrotoxicity. Systemic toxicities are worsened, but therapeutic response seems to be enhanced. The pharmacokinetics of cisplatin in plasma and urine were examined to assess the causes of these effects. Plasma disappearance of ultrafiltrable platinum was well-described by a single exponential for each patient. The mean t1/2 was 50% longer for patients receiving high-dose cisplatin than for patients receiving conventional doses. The total systemic exposure was three times greater in the high-dose group, which tends to explain the systemic toxicity and improved tumor efficacy, but not the lack of nephrotoxicity. It is suggested that the kidneys of patients in the high-dose group were relatively protected by dilution of active Pt species in the urine in the tubule lumen as well as by high chloride ion concentrations in the urine.

Adult↗
PubMed1985

Clinical pharmacology of 5-iodo-2'-deoxyuridine and 5-iodouracil and endogenous pyrimidine modulation.

We describe the clinical pharmacology and metabolism of 5-iodo-2'-deoxyuridine (IdUrd) during and after a 12-hour infusion. The kinetics of IdUrd were linear between 250 and 1200 mg/m2. The plasma IdUrd concentration reached steady state in less than 1 hour. Total body clearance of IdUrd was 750 ml/min/m2 and the disappearance t1/2 at the end of the infusion was less than 5 minutes. The primary metabolite, 5-iodouracil (IUra), did not reach steady state during the infusion. At the end of the 1200 mg/m2 infusion, the maximum plasma IUra concentration was 100 mumol/L, or about 10 times the simultaneous IdUrd plasma concentration. During the infusion there was at least a fifty- to 100-fold increase in uracil and thymine plasma concentrations. After the infusion, IUra disappearance from plasma was nonlinear, with an apparent Michaelis constant of 30 mumol/L. Plasma uracil and thymine levels slowly decreased after the IdUrd infusion until IUra fell to less than 30 mumol/L. There was subsequently a parallel and more rapid decrease in the plasma concentrations of uracil and thymine. Uridine, 2'-deoxyuridine, and thymidine plasma levels did not change significantly as a result of IdUrd therapy. These changes in endogenous pyrimidine pools are consistent with competitive inhibition of dihydrouracil dehydrogenase by IUra. An in vitro human bone marrow assay was used to determine the relative toxicity of IdUrd and IUra. Although exposure to IUra was tenfold higher than that to IdUrd, IdUrd was at least 100 times more cytotoxic to marrow cells.

Chromatography, High Pressure Liquid↗