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Biomedical subjects

M E Lippman

Publications and source records attributed to M E Lippman.

At least 343 records · Page 19Linked to original sources
PubMed1975

Glucocorticoid binding proteins in myeloblasts of acute myelogenous leukemia.

The myeloblasts of 16 patients with untreated acute myelogenous leukemia were examined for specific glucocorticoid binding proteins. In only 3 of the 16 patients were such high affinity receptors found. The presence of glucocorticoid binding protein activity was positively correlated with inhibition of macromolecular synthesis of myeloblasts in vitro whereas absence of binding protein activity was associated with lack of glucocorticoid inhibition of the cells. Since glucocorticoids appear efficacious in only a small fraction of cases of acute myelogenous leukemia, determination of glucocorticoid binding protein activity may provide assistance in planning chemotherapeutic regimens.

Bone Marrow↗
PubMed1975

Competitive protein binding assay for methotrexate.

A competitive protein binding assay has been developed for methotrexate based on the tight binding of this drug to Lactobacillus casei dihydrofolate reductase (= tetrahydrofolate dehydrogenase; 5,6,7,8-tetrahydrofolate: NADP+ oxidoreductase; EC 1.5.1.3). Free drug may be separated from that bound to reductase by adsorption with dextran--albumin coated charcoal. Scatchard plot analysis of the enzyme--drug interaction confirmed the presence of a single homogeneous class of binding sites with an association constant Ka of 2.1 X 10(8) M-1. This high affinity binding permits detection of methotrexate in the range of 0.3--30 pmol with a coefficient of variation of 15% or less. The predominant circulating folate, 5-methyl tetrahydrofolate, and the clinically useful rescue agent leucovorin (5-formyl tetrahydropteroyl-glutamic acid) do not interfere with the assay, nor does the methotrexate metabolite 4-amino-4-deoxy-10-methylpteroic acid. Assay of clinical samples, including plasma and cerebrospinal fluid, showed close agreement between the previously described enzyme inhibition assay and the more rapid competitive binding method.

Binding Sites↗
PubMed1975

Interaction of spironolactone and digitalis with the 5 alpha-dihydrotestosterone (DHT) receptor of rat ventral prostate.

The aldosterone antagonist, spironolactone, has been shown to block the effects of exogenously administered androgen in rat. This suggests that interaction of the drug with androgen at the target tissues may occur. In this paper we have studied the possible interaction of spironolactone with the 5alpha-dihydrotestosterone (DHT)1 receptor of rat ventral prostate. The competitive receptor assay used involves precipitation of the 105,000 X g supernatant of the homogenized tissue with protamine sulfate, removal of the unprecipitated cytosol, and incubation of the precipitate in the presence of the appropriate [3H]DHT steroid solution at 0 C for 18 hours. Using this method the Kd (dissociation constant) for DHT in the rat prostate was in the range of 1.9-4.0 X 10(-9)M and the binding capacity was 0.21 pmol/mg protein. Spironolactone was found to interfere with the binding of DHT to the precipitated cytosol and displayed an estimated Kd of 1.3-4.6 X 10(-8)M. Several digitalis preparations were similarly studied. Digitoxin and digitoxigenin also interfered with the binding of [3H]DHT and had an estimated Kd of 0.8-3.6 X 10(-8)M. Digoxin interacted less strongly and its estimated Kd was 10(-6)M. We believe these results suggest an interaction of spironolactone and digitalis with the DHT receptor and may help explain some of their antiandrogenic actions in the rat and in man.

Animals↗
PubMed1973

Glucocorticoid-binding proteins in human acute lymphoblastic leukemic blast cells.

The first known step in steroid hormone action is the association of the steroid with specific cytoplasmic steroid-binding proteins (SBP). Using a competitive binding assay, we detected, quantified, and partially characterized such a SBP in cytosol from glucocorticoid-sensitive human lymphoblastic leukemic blasts. The affinity of steroids for the SBP was directly related to their known killing potency. For example, steroids without glucocorticoid effect such as androstenedione, etiocholanolone, and tetrahydrocortisol were unable to displace radiolabeled dexamethasone from the SBP in the binding reaction. The dose-response curve for in vitro inhibition of [(3)H]thymidine uptake in leukemic blasts correlated closely with the binding affinity of glucocorticoids to the SBP, providing additional support for an essential physiologic role for SBP in steroid action. SBP activity was either greatly diminished or absent in glucocorticoid-resistant cells. Six patients who intially had SBP in their blasts and were responsive to combinations of drugs including glucocorticoids no longer had SBP activity detectable at a time when they no longer responded to combinations of drugs including glucocorticoids. In vitro [(3)H]thymidine uptake was not inhibited by steroids in leukemic blast cells lacking SBP activity. Other patients who had received some antileukemic therapy including glucocorticoids and who still had SBP in their leukemic blasts, were still responsive to drug combinations that included glucocorticoids. This appears to be the first study demonstrating glucocorticoid receptors in a human tissue.

Androstenedione↗
PubMedDate not supplied

Molecular biology of breast carcinoma.

During the last several years basic research has resulted in the identification of many of the factors involved in signal transduction pathways, leading us to a greater understanding of the mechanisms of growth control in breast cancer cells. Many of these factors are the products of proto-oncogenes or suppressor genes. This review describes the role of some of these factors in breast cancer development, progression, and metastasis and discusses implications for future directions.

Breast Neoplasms↗
PubMedDate not supplied

Melatonin increases oestrogen receptor binding activity of human breast cancer cells.

Breast cancer is frequently a hormone-dependent tumour, and several studies have suggested that the pineal gland hormone melatonin may influence the growth and development of this malignancy. Subcutaneous injections of melatonin have been shown to inhibit, and pinealectomy to enhance, the development of dimethyl benz(a)anthracene (DMBA)-induced mammary tumours in rats. Use of the psychotropic drug thorazine, which increases plasma melatonin levels, has been associated with a decreased incidence of breast cancer in psychiatric patients. Calcification of the pineal gland has been correlated with an increased incidence of breast cancer in women. While the mechanism by which melatonin influences these tumours is unknown, both human breast cancer and DMBA-induced tumours contain oestrogen receptors (ER) and respond to changes in the oestrogen milieu. We therefore wondered whether melatonin might be altering ER binding activity of these tumours. We report here that in vitro incubation of MCF-7 human breast cancer cells with melatonin in physiological conditions increased the cytoplasmic and nuclear ER activity of these cells within 40 min, giving no change in the equilibrium dissociation constant (Kd) of the receptor. This induction was blocked by cycloheximide, and thus requires continuous protein synthesis. The modulation of ER binding activity of breast cancer by another endogenous hormone may be important for understanding the behaviour and treatment of this disease, and may provide insight into the factors regulating the synthesis and metabolism of steroid hormone receptors.

Breast Neoplasms↗
PubMedDate not supplied

Effects of temperature, nucleotides and sodium molybdate on activation and DNA binding of estrogen, glucocorticoid, progesterone and androgen receptors in MCF-7 human cancer cells.

We studied the effects of temperature, ribonucleotides and sodium molybdate on the activation and DNA cellulose binding of estrogen, glucocorticoid, progesterone and androgen receptor complexes in MCF-7 cells. Using DNA cellulose binding as a measure of receptor activation, we found that ribonucleotides activated all four of these receptor complexes. Temperature also activated glucocorticoid receptor complexes efficiently but activated progesterone and androgen receptor complexes less well. Temperature did not activate estrogen receptor complexes. Sodium molybdate blocked either ATP or temperature induced activation of glucocorticoid, progesterone and androgen receptor complexes but only partially blocked estrogen activation. Sodium molybdate also prevented the formation of multiple forms of estrogen and glucocorticoid receptor complexes seen on DEAE cellulose and hydroxylapatite chromatography of crude cytosol. The mechanism by which ribonucleotide enhances and molybdate inhibits activation are discussed.

Cells, Cultured↗