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Query: UMLS:C0025202 (melanoma)
 69,561 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cultured melanoma cells were labeled with 3H-leucine over a period of 1-3 days. The labeled cells were mechanically disrupted and a preparation of "extranuclear membranes" was obtained by differential centrifugation. The membrane fragments were solubilized by the nonionic detergent NP-40 and the soluble material was double precipitated with antisera from melanoma patients and anti-human immunoglobulin sera. Because of the small quantitative differences of precipitated radiolabeled material between control and melanoma patients' sera, the precipitates were further analyzed on SDS-containing polyacrylamide gels. The labeled profiles of experimental and control gels now revealed clearcut differences usually seen in 2-3 characteristic peaks in the molecular weight range from 130,000-330,000.
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PMID:Membrane associated antigens of human malignant melanoma. I. Internal labeling, detergent solubilization and characterization by homologous antisera and polyacrylamide gel electrophoresis. 12 75

Sera of patients with various malignancies are known to contain DNA-binding proteins (DBP) which are not present in sera of normal individuals. In this paper sera of patients with malignant melanoma (MM) were examined as to whether characteristic DBP are present, too. DBP are isolated by DNA-affinity chromatography and represent 0.5-0.9% of all serum proteins. After separation of the DBP by SDS slab gel electrophoresis no typical DBP is detectable in sera of MM-patients. However, quantitative differences are found in sera of patients in the clinical stages I-III and/or tumor level 3-5: 1. All 9 sera of patients who had clinical signs of MM contain more DBP with molecular weight (mw) of 20,000-24,000 dalton than control sera. However, these DBP are only increased in 30% of the 22 sera from MM-patients who had clinical signs for 13-73 months after tumor excision. 2. All sera of the 10 MM-patients of whom sera were drawn twice after tumor excision at an interval of 7-46 months without clinical signs, showed a reduction of DBP with mw 30,000, 68,000, and 165,000.
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PMID:DNA-binding proteins in the sera of patients with malignant melanoma. 22 3

Murine melanoma cells provide an excellent system for studying the proposed role of nuclear nonhistone proteins (NHP's) as regulators of gene expression. Cloudman mouse melanoma cells (S91, NCTC 3960, CCL 53), grown in culture, are normally lightly pigmented, but in the presence of melanocyte stimulating hormone (MSH) show a large increase in melanin content. Cells were grown in medium with and withoug MSH and labeled with either 14C- or 3H-leucine, respectively. Following 48 hr of incubation, the cells were harvested, combined, and nuclei isolated. The NHPs were extracted from these nuclei in a series of steps which yielded 4 major fractions. Each fraction was further separated on DEAE cellulose columns into a total of 40 subfractions, each of which was electrophoresed on SDS gels. Each gel was sliced and counted and the 14C/3H ratio was determined for each slice. A number of differences in 14C/3H ratios were observed between the NHPs isolated from MSH-treated and control cells which reflect changes in the synthesis and/or transport of NHPs in MSH-treated cells.
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PMID:Nuclear nonhistone proteins in murine melanoma cells: II. changes following exposure to MSH. 41 35

Serine proteases or esterases released from cell cultures into the growth medium were converted to radioactive derivatives by active site labeling with tritiated DFP, both in the presence and absence of other competing active site reagents. The individual labeled enzymes were then identified by SDS-polyacrylamide gel electrophoresis and scintillation autoradiography. Conditioned medium from embryonal mouse fibroblasts transformed by mouse sarcoma virus contained five serine enzymes that were not present in medium from normal cells; two serine enzymes were released by both cell types, and one serine enzyme was found only in medium from normal cells. Two of the enzymes released by transformed cells were identified as plasminogen activators; these accounted for most of the serine enzyme labeling in transformed culture media and for most of the serine enzyme difference between normal and transformed cultures. The culture fluids from two cell strains of human neoplastic origin were examined by the same method. A rhabdomyosarcoma strain released eight serine enzymes (mol wt ranging from 22,500 to 102,000), four of which were plasminogen activators; seven serine enzymes (mol wt 26,000-102,000), including two plasminogen activators, were detected in medium from human melanoma cultures. In terms of electrophoretic mobility two of the plasminogen activators from rhabdomyosarcoma were identical with those from melanoma cultures, while the remaining two rhabdomyosarcoma activators coincided with activators found in commerical urokinase.
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PMID:Serine enzymes released by cultured neoplastic cells. 63 49

Melanosomes from B-16 mouse melanoma cells in culture were isolated by treatment of pigmented cells with 2% SDS, sonication, and heating at 100 degrees C. The total number of melanosomes in cultures of B-16 mouse melanoma cells increased exponentially during the rapid phase of sigmoid growth. The numbers of melanosomes per cell decreased during rapid phase of growth, and repigmentation was observed only when the cultures attained the stationary growth phase. BUdr at a minimum concentration of 0.5 mug/ml decreased both cell growth and numbers of melanosomes per cell, and completely inhibited repigmentation following a period of active growth. Cells cultured in 0.1 mug/ml BUdr grew at the same rate as untreated cells but contained fewer melanosomes/cell and lower total numbers of melanosomes during the late stages of the growth cycle.
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PMID:Variation in melanosome numbers in cultured B-16 melanoma cells. 97 63

Nuclear nonhistone proteins (NHP's) have been implicated as regulatory agents involved in controlling genetic expression. Utilizing murine melanoma cells, we describe a method for isolating and fractionating NHP's which greatly increases the yield of these proteins as well as the level of resolution required for detecting small differences in particular NHP's. Mouse melanoma cells were grown in medium labeled with [(3)H]leucine. Following 48 hr of incubation, the cells were harvested and nuclei isolated. The NHP's were extracted from the nuclei in a series of steps which yielded four major fractions: NHP(1), NHP(2), NHP(3), NHP(4). This method solubilized 80-90% of the protein from the nuclear homogenate. The NHP fractions were then separated on DEAE-cellulose columns in a series of salt steps increasing in concentration from 0.05 to 0.50 M NaCl, followed by steps of 2 M NaCl and 4 and 7 M guanidine-hydrochloride. The 40 NHP fractions eluted from these columns were further separated on polyacrylamide-SDS gels and ranged in molecular weight from 9000 to 110,000 daltons. Differences were observed in the electrophoretic pattern of each of these 40 fractions. The high resolution of these fractionation procedures greatly enhances the possibility of observing small changes in proteins which may play a role in gene regulation.
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PMID:Nuclear nonhistone proteins in murine melanoma cells. I. Quantitative isolation and fractionation. 99 93

Expression of apical cell surface proteins and glycoproteins was examined in polarized primary cultures of mouse uterine epithelial cells (UEC). Lectin-gold cytochemistry revealed that wheat germ agglutinin (WGA) bound specifically to the components of the apical glycocalyx as well as intracellular vesicles. Double labeling with the pH sensitive dye 3-(2,4-dinitroanilino)-3'amino-N-methyldipropylamine (DAMP) demonstrated the acidic nature of the WGA-staining intracellular vesicles. The enzymatic and chemical sensitivities of the WGA binding sites on the apical cell surface were monitored both by WGA-gold staining as well as by 125I-WGA binding assays. In thin sections, a large fraction of these sites were removed by pronase; however, application of a wide variety of proteases, glycosidases, or chemical treatments to the apical surface of intact UEC failed to reduce WGA binding. In no case did treatments designed to remove sialic acids reduce 125I-WGA binding more than 12%. In contrast, endo-beta-galactosidase as well as a combination of beta-galactosidase with beta-hexosaminidase succeeded in removing 28% and 77% of these sites, respectively. These studies suggested that the majority of the apically disposed WGA binding sites involved N-acetylglucosamine residues rather than sialic acids and included lactosaminoglycans. Many of the proteins detected at the apical cell surface by lactoperoxidase-catalyzed radioiodination were WGA-binding glycoproteins. A major class of these glycoproteins displayed Mr > 200 kDa by SDS-PAGE and was heavily labeled metabolically by 3H-glucosamine or by vectorial labeling at the apical cell surface with galactosyl transferase and UDP-3H-galactose. Analyses of the 3H-labeled oligosaccharides labeled by either procedure indicated that a large fraction of the apically disposed WGA-binding oligosaccharides consisted of neutral, O-linked mucin-type structures with median MW of approximately 1,500. Oligosaccharides in this fraction were partially (15%) sensitive to endo-beta-galactosidase digestion and bound to Datura stramonium agglutinin (68%), demonstrating the presence of lactosaminoglycan sequences. UEC were an extremely effective barrier to attachment or invasion by either a highly invasive melanoma cell line, B16-BL6, or implantation-competent mouse blastocysts. In contrast, neither uterine stromal cells nor a non-polarizing UEC cell line, RL95, prevented B16-BL6 attachment.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:WGA-binding, mucin glycoproteins protect the apical cell surface of mouse uterine epithelial cells. 129 97

In this study we have compared the effects of different pro-opiomelanocortin (POMC) peptides on melanogenesis and metastasis and their relationship to MSH receptor expression in B16F1 melanoma cells. All peptides, apart from beta-endorphin, increased melanogenesis and the order of potency was Nle4DPhe7-alpha-MSH greater than alpha-MSH greater than ACTH[1-39] greater than des-acetyl alpha-MSH greater than ACTH[1-24]. A similar order of potency was found for metastasis, except for ACTH [1-24], which had a relatively greater effect on metastasis. These findings suggest that the effects on melanogenesis and metastasis are mediated via the same receptor. The results of ligand binding studies also indicated the presence of a single receptor with a KD value for Nle4DPhe7-alpha-MSH of 62 +/- 16pM. This was consistent with crosslinking studies using [125I] Nle4DPhe7-alpha-MSH which produced a single 50-55 kD band on analysis by SDS-PAGE. However, the relative binding affinities of the different peptides, measured by displacement of [125I]-Nle4DPhe7-alpha-MSH, did not closely correlate with the relative potencies in stimulating melanogenesis and metastasis. This suggests that receptor activation and the subsequent biological response is not determined solely by binding affinity.
Melanoma Res 1992 May
PMID:MSH receptor expression and the relationship to melanogenesis and metastatic activity in B16 melanoma. 132 55

The alpha-melanocyte-stimulating hormone (alpha-MSH) receptor of B16 mouse melanoma cells was characterized by photoaffinity labelling using radiolabelled photoactive derivatives of alpha-MSH. A doublet band of 43-46 kDa representing a ligand-receptor complex was identified. A novel adaptation of the streptovadin/biotin-based affinity system was used to isolate the alpha-MSH receptor. A probe was synthesized which contained biotin connected to a photolabelled alpha-MSH analogue via a cleavable disulphide linker and which displayed high affinity for the alpha-MSH receptor. Streptavidin-coated magnetic beads were used as a solid support instead of an affinity column. Covalently linked probe-receptor complexes solubilized in Triton X-100 were equilibrated with the beads, and after magnetic separation and washing, specifically bound complexes were treated with dithiothreitol to cleave the disulphide bridge in the biotin-peptide spacer arm and so release the receptor-ligand complex. The identity of the isolated protein was established by SDS/PAGE analysis. Methods to achieve purification to homogeneity and to allow quantitative isolation of the receptor are discussed.
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PMID:Isolation and partial purification of a melanocyte-stimulating hormone receptor from B16 murine melanoma cells. A novel approach using a cleavable biotinylated photoactivated ligand and streptavidin-coated magnetic beads. 132 40

Tyrosinase induction in murine malignant melanocytes by alpha MSH is well known, but its molecular basis has not been characterized. Treatment of B16 melanoma cells with theophylline or alpha MSH mediates a larger induction of tyrosine hydroxylase than of dopa oxidase activity in total cell extracts, and in the melanosomal and microsomal fractions. No evidence for the modulation of a tyrosinase effector was found. SDS-PAGE and specific activity stain demonstrated two forms of tyrosinase, with different degrees of induction by theophylline. These results agree with the recent proposal that two tyrosinases, encoded by different genes, are present in murine melanocytes.
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PMID:Melanocyte stimulating hormone activation of tyrosinase in B16 mouse melanoma cells. Evidence for a differential induction of two distinct isoenzymes. 135 58


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