Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0025202 (melanoma)
 69,561 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Results of hemacytometer cell counts and of tyrosinase measurements made by the Pomerantz method demonstrate that imidazole added to the medium of cultured B16 mouse melanoma cells can stimulate tyrosinase specific activity and inhibit cell division. These effects are greater than with adenosine 3',5' cyclic monophosphate (cAMP) or the cAMP-phosphodiesterase inhibitor theophylline. The effects of imidazole on cell division and tyrosinase are enhanced by theophylline and antagonized by cAMP. Cyclic AMP-phosphodiesterase activity in cell-free extracts can be inhibited by theophylline and stimulated by imidazole. However, imidazole does not affect cAMP-phosphodiesterase specific activity in vivo, nor does it affect intracellular cAMP concentrations as determined by competitive protein-binding assays. In contrast, the specific activity of cAMP-phosphodiesterase in vivo is stimulated by cAMP and theophylline, supporting the hypothesis that cAMP and agents which increase intracellular cAMP concentrations induce the synthesis of cAMP-phosphodiesterase. Studies with actinomycin-D and cycloheximide support the hypothesis that cAMP can also mediate posttranslational activation of tyrosinase. Similar experiments suggest that imidazole, or a derivative thereof, can induce the synthesis of tyrosinase at the pretranslational level of control. We hypothesize that this type of regulation (pretranslational) by imidazole may define a role for the concept of "Metabolite Gene Regulation" (MGR), in mammalian cells.
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PMID:Regulation of cell division and of tyrosinase in B16 melanoma cells by imidazole: a possible role for the concept of metabolite gene regulation in mammalian cells. 626 Aug 21

The effect of theophylline, an inhibitor of phosphodiesterase, on tyrosine (Tyr) transport across cell membrane was studied using cultured B-16 mouse melanoma cells. 1.5 mM Theophylline in culture medium increased Tyr uptake velocity in linear fashion up to 36 h, after which it reached a plateau at which the cells showed about a 60% increase in Tyr transport velocity. This increase was independent of extracellular Na, essentially unaffected by cell density, and partially inhibited by concomitantly added cycloheximide. These results suggested that biosynthesis of macromolecules, probably acting as System L transporter, was induced by theophylline treatment.
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PMID:Effect of theophylline on the transport of tyrosine in cultured B-16 mouse melanoma cells. 643 10

Transfection of class I H-2Kb or H-2Kd into cells of a pigmented subclone of B16-F10 BL6 (termed BL6-8) results in the loss of melanin production. In contrast, transfected BL6-8 cells expressing H-2Dd, H-2Ld, class I H-21Ak and/or the neor genes maintained their pigmented phenotype. Melanogenesis was also inhibited in cells which expressed the endogenous H-2Kb, but not the endogenous H-2Db, gene. In order to identify the specific defects in the melanogenic pathway responsible for the absence of melanin production, factors known to be related to the regulation of pigment formation were evaluated in H-2K-expressing cells. These studies showed that: (1) transfection of BL6-8 cells with the H-2Kb or H-2Kd, but not with the H-2Dd, H-2Ld or H-21Ak, genes was associated with complete inhibition of tyrosinase activity; (2) alpha-melanocyte-stimulating hormone (MSH) and theophylline (an inhibitor of cAMP phosphodiesterase) failed to stimulate tyrosinase activity in H-2K-positive cells, whereas tyrosinase activities in untransfected, or H-2DdH-2Ld, neor or H-21Ak-transfected cells were dramatically increased by those agents; (3) treatment with MSH had no effect on cAMP levels in H-2K-positive cells but stimulated cAMP levels more than 100-fold in H-2K-negative cells; (4) in contrast to MSH, forskolin, a stimulator of adenylate cyclase, was able to stimulate cAMP levels in all cell lines tested, but in H-2Kb-positive cells the levels of forskolin-induced cAMP were significantly less than those elicited in H-2Kb-negative cells; (5) electron microscopy showed that H-2K-positive cells lacked mature melanosomes; (6) Northern blot analyses showed that H-2K-positive cells lacked mRNA for tyrosinase or for the MSH receptor. Taken together, expression of the endogenous or transfected H-2K gene in BL6 melanoma cells results in down-regulation of the entire melanogenic pathway, including the inhibition of tyrosinase and MSH receptor gene expression, cAMP responses and melanosomal biogenesis.
Melanoma Res 1995 Feb
PMID:Impairment of the melanogenic pathway in B16 melanoma cells transfected with class I H-2 genes. 773 52

We examined the in vitro effects of 8-chloro-adenosine 3':5'-monophosphate (8-Cl-cAMP), a reportedly stable, potent and site-selective analogue of cAMP, on the proliferation and sensitivity to doxorubicin (DXR) of two mouse cell lines, the B16 melanoma and Friend leukaemia, both as wild-type (B16, FLC) and DXR-resistant (B16/DXR, FLC/DXR) variants. The latter strains had characteristics of 'typical' multidrug resistance (MDR), including the over-expression of P-glycoprotein. Encouragingly, 8-Cl-cAMP affected almost equally the growth of the chemosensitive and chemoresistant variants of both cell lines. Its activity proved to be much more elevated on cells cultivated with fresh rather than heat-inactivated calf serum. In fact, the IC50 values for B16 and B16/DXR were about 4.7 microM in fresh serum and 215 microM in heat-inactivated serum; the IC50 values for FLC and FLC/DXR were about 12 microM in fresh serum and 70 microM in heat-inactivated serum. Furthermore, experiments with B16 showed that cotreatments with isobutylmethylxanthine (IBMX), a phosphodiesterase inhibitor, or adenosine deaminase (ADA) greatly reduce the activity of 8-Cl-cAMP bringing it to comparable levels in fresh and heat-inactivated serum. These results indicate that the antiproliferative effects of 8-Cl-cAMP may be due principally to metabolites formed by the enzymic activities of the serum, most probably including 8-chloro-adenosine (8-Cl-adenosine), as suggested by other authors. Moreover, the dose-response curves and the IC50 values of the latter compound for the various cell lines were compatible with those observed for 8-Cl-cAMP in fresh serum. Finally, there was no evidence that 8-Cl-cAMP, either in the presence of fresh or heat-inactivated serum, or 8-Cl-adenosine may increase the sensitivity to DXR of the MDR variants of B16 melanoma and Friend leukaemia.
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PMID:Effects of 8-chloro-cyclic adenosine monophosphate on the growth and sensitivity to doxorubicin of multidrug-resistant tumour cell lines. 783 Nov 98

A human cDNA clone encoding autotaxin, a tumor cell motility-stimulating protein, reveals that this protein is an ecto/exo-enzyme with significant homology to the plasma cell membrane differentiation antigen PC-1. ATX is a 125-kDa glycoprotein, previously isolated from a human melanoma cell line (A2058), which elicits chemotactic and chemokinetic responses at picomolar to nanomolar concentrations. Affinity-purified antipeptide antibodies to the ATX peptide, ATX-102, were employed to screen an A2058 cDNA expression library made in lambda gt11. The partial cDNA sequence which was obtained was then extended by utilizing reverse transcriptase on total cellular RNA followed by polymerase chain reaction amplification. The isolated cDNA clone contained 3251 base pairs, and the mRNA message size was approximately 3.3 kilobases. The deduced amino acid sequence of autotaxin matched 30 previously sequenced peptides and comprised a protein of 915 amino acids. Data base analysis of the ATX sequence revealed a 45% amino acid identity (including 30 out of 33 cysteines) with PC-1, a pyrophosphatase/type I phosphodiesterase expressed on the surface of activated B cells and plasma cells. ATX, like PC-1, was found to hydrolyze the type I phosphodiesterase substrate p-nitrophenyl thymidine-5'-monophosphate. Autotaxin now defines a novel motility-regulating function for this class of ecto/exo-enzymes.
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PMID:cDNA cloning of the human tumor motility-stimulating protein, autotaxin, reveals a homology with phosphodiesterases. 798 64

Isoenzymes of 3',5'-cyclic nucleotide phosphodiesterase (PDE) have been characterized in B16 murine melanoma cells and MCF-7 human mammary carcinoma cells. Separation of soluble phosphodiesterase activity by fast protein liquid chromatography on a Mono-Q column resolved three isoenzymes, MCF-7 cells contained a cyclic GMP-specific isoenzyme (PDE-V), a cyclic GMP-activable isoenzyme (PDE-II), and a cyclic AMP-specific isoenzyme (PDE-IV). B16 cells contained a cyclic GMP-specific isoenzyme (PDE-V), a Ca2+/calmodulin-activated isoenzyme (PDE-I), and a cyclic AMP-specific isoenzyme (PDE-IV). A series of PDE inhibitors was tested for their activity spectrum on PDE isoenzymes. Inhibition of PDE activity in B16 cells by the new compound DC-TA-46, was found to result specifically from PDE-IV inhibition [50% inhibition (IC50) = 0.03 microM]. Much lower inhibitory activity was observed for DC-TA-46 toward PDE-I (IC50 = 5 microM) and PDE-V (IC50 = 14 microM). DC-TA-46 was found to inhibit growth of B16 melanoma and MCF-7 mammary carcinoma cells dose dependently (B16: IC50 = 1.7 microM, MCF-7: IC50 = 2 microM). At 2 microM concentration, growth inhibition of B16 melanoma cells was 60%, concomitant with a decrease in PDE activity of 63% and an increase in cAMP level of 59%. In contrast, incubation with inhibitors specific for PDE-I and PDE-V resulted only in marginal or undetectable growth inhibition. The results suggest a correlation between PDE-IV inhibition and growth inhibition. PDE-IV thus appears to be a potential new target for antiproliferative treatment.
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PMID:3',5'-Cyclic nucleotide phosphodiesterase in tumor cells as potential target for tumor growth inhibition. 839 85

4 clonal sublines of Cloudman S91 melanoma cells, S91/mel, S91/I3, S91/6 and S91/amel, were evaluated for changes in growth, pigment content and plating efficiency during and after treatment with a cyclic-AMP phosphodiesterase inhibitor-melanin-stimulating agent, 3-isobutyl-1-methyl-xanthine (IBMX) plus beta-melanocyte stimulating hormone (beta-MSH) or IBMX alone. After combined treatment, increases in melanin content on day 3 were 48, 27, 11, and 2 pg/cell in the four cell lines respectively. In each case IBMX alone was less effective than IBMX plus beta-MSH. Doubling time increased and plating efficiency decreased with increased melanization. The increases in doubling time and decreases in plating efficiency were cell line dependent. The greatest rate of increase in doubling time and decrease in plating efficiency as a function of melanin content were seen in S91/amel, which produced the least pigment. The lowest rates of increase/decrease were seen in S91/mel, which produced the most pigment. Melanin pigment induced in the cells was classified as eumelanin by EPR determination. The differential response to induction of pigmentation makes these cell lines suitable models for comparative studies on the role of melanin in pigment cell biology.
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PMID:Growth and pigmentation in genetically related Cloudman S91 melanoma cell lines treated with 3-isobutyl-1-methyl-xanthine and beta-melanocyte-stimulating hormone. 853 13

Autotaxin (ATX) is an extracellular enzyme and an autocrine motility factor that stimulates pertussis toxin-sensitive chemotaxis in human melanoma cells at picomolar to nanomolar concentrations. This 125-kDa glycoprotein contains a peptide sequence identified as the catalytic site in type I alkaline phosphodiesterases (PDEs), and it possesses 5'-nucleotide PDE (EC 3.1.4.1) activity (Stracke, M. L., Krutzsch, H. C., Unsworth, E. J., Arestad, A., Cioce, V., Schiffmann, E., and Liotta, L. (1992) J. Biol. Chem. 267, 2524-2529; Murata, J., Lee, H. Y., Clair, T., Krutsch, H. C., Arestad, A. A., Sobel, M. E., Liotta, L. A., and Stracke, M. L. (1994) J. Biol. Chem. 269, 30479-30484). ATX binds ATP and is phosphorylated only on threonine. Thr210 at the PDE active site of ATX is required for phosphorylation, 5'-nucleotide PDE, and motility-stimulating activities (Lee, H. Y., Clair, T., Mulvaney, P. T., Woodhouse, E. C., Aznavoorian, S., Liotta, L. A., and Stracke, M. L. (1996) J. Biol. Chem. 271, 24408-24412). In this article we report that the phosphorylation of ATX is a transient event, being stable at 0 degrees C but unstable at 37 degrees C, and that ATX has adenosine-5'-triphosphatase (ATPase; EC 3.6.1.3) and ATP pyrophosphatase (EC 3.6.1.8) activities. Thus ATX catalyzes the hydrolysis of the phosphodiester bond on either side of the beta-phosphate of ATP. ATX also catalyzes the hydrolysis of GTP to GDP and GMP, of either AMP or PPi to Pi, and the hydrolysis of NAD to AMP, and each of these substrates can serve as a phosphate donor in the phosphorylation of ATX. ATX possesses no detectable protein kinase activity toward histone, myelin basic protein, or casein. These results lead to the proposal that ATX is capable of at least two alternative reaction mechanisms, threonine (T-type) ATPase and 5'-nucleotide PDE/ATP pyrophosphatase, with a common site (Thr210) for the formation of covalently bound reaction intermediates threonine phosphate and threonine adenylate, respectively.
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PMID:Autotaxin is an exoenzyme possessing 5'-nucleotide phosphodiesterase/ATP pyrophosphatase and ATPase activities. 899 94

Autotaxin (ATX) is a newly found autocrine tumor cell motility-stimulating factor. ATX is a member of the ecto-phosphodiesterase I (PD-I)/ nucleotide pyrophosphatase family. PD-Ialpha was found as a brain-type ecto-phosphodiesterase I/nucleotide pyrophosphatase. ATX and PD-Ialpha are alternative splicing products from one gene. ATX stimulates motility of A2058 melanoma cells in vitro; however, it has not been known if PD-Ialpha/ATX is expressed in naturally occurred human tumors. In this study, we examined the expression of the human PD-Ialpha/ATX gene in human neuroblastoma tumor tissues and the motility stimulating activity of recombinant ATX on neuroblastoma cells and investigated its transcriptional regulatory mechanism in a human neuroblastoma cell line. The PD-Ialpha/ATX gene was expressed in the primary tumor tissues from neuroblastoma patients to varying degrees. This gene is also expressed in the SMS-KAN neuroblastoma cell line. We identified both isoforms, PD-Ialpha and ATX, in these tumor tissues and SMS-KAN cells. The recombinant ATX stimulated the motility of SMS-KAN cells at low nanomolar concentration. We situated the promoter region, which is essential for its transcription in SMS-KAN cells, at -287 to -254 nucleotides by the promoter activity assay. The gel-shift assay revealed that there exists a nuclear protein in SMS-KAN cells that binds this region. These new insights about autocrine tumor cell motility-stimulating protein will help us to understand the metastatic mechanism of human neuroblastoma.
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PMID:Expression and transcriptional regulation of the PD-Ialpha/autotaxin gene in neuroblastoma. 919 34

Four closely related cyclic-nucleotide specific phosphodiesterase (PDE4) genes have been identified in both humans and rats: PDE4A, 4B, 4C and 4D. We have now cloned cDNAs for multiple splice variants of human PDE4C. Two splice variants, PDE4C-791 and PDE4C-426, were isolated from a fetal lung library. The longest open reading frame (ORF) of 791 amino acids (aa) is encoded by PDE4C-791, which is similar to a recently described cDNA [Engels, P., Sullivan, M., Muller, T. and Lubbert, H. FEBS Lett. 358 (1995) 305-10], except that an alternative 5'-end sequence upstream of the first methionine extends the PDE4C-791 ORF by 79 aa. The PDE4C-426 variant contains 3 insertions that are located 5' to the catalytic domain and encode several in-frame stop codons. The predicted 426 aa protein initiates at a methionine 365 aa within PDE4C-791. A baculovirus clone starting at this methionine expressed an enzymatically active protein. Two additional splice variants, PDE4C-delta54 and PDE4C-delta109, were found in testis mRNA. PDE4C-delta54 contained a novel 5'-end region and a deletion of 162 nt; the predicted protein deletes 54 aa from the amino-terminal region. The PDE4C-delta54 protein produced in baculovirus-infected cells was enzymatically active and sensitive to PDE4-specific inhibitors. The PDE4C-delta109 protein is similar to PDE4C-delta54 but has an additional 55 aa deleted in the catalytic domain; it lacked enzymatic activity. Analysis of uncloned total mRNA from 4 tissue sources by polymerase chain reaction (PCR) confirmed the presence of mRNAs with the two deletions and three insertions that we observed in cDNA clones. The PDE4C-delta54 variant was found only in testis and the 5'-extended region of PDE4C-791 was seen only in lung and the melanoma cell line G361. Hence, tissue-specific expression of various PDE4C isoforms should be considered in understanding how these gene products modulate cellular responses to cAMP.
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PMID:Multiple splice variants of phosphodiesterase PDE4C cloned from human lung and testis. 934 24


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