Bromodeoxyuridine- and cyclic AMP-mediated regulation of tyrosinase in Syrian hamster melanoma cells

In Bomirski Ab amelanotic hamster melanoma cells, L-tyrosine and/or L-dopa induce increases in tyrosinase activity as well as synthesis of melanosomes and melanin. L-tyrosine also modifies melanocyte-stimulating hormone (MSH) binding. In this paper we show that in the Bomirski amelanotic melanoma system MSH and agents that raise intracellular cyclic AMP induce dendrite formation, inhibit cell growth, and cause substantial increases in tyrosinase activity without inducing melanin synthesis. Tyrosinase activity is detected only in broken cell preparations, or cytochemically in fixed cells. In the continued absence of mature melanosomes, the induced enzyme remains in elements of the trans-Golgi reticulum. Comparative measurements of cyclic AMP in amelanotic and tyrosine-induced melanotic cells show similar basal levels. L-tyrosine and L-dopa have little or no effect, whereas MSH may cause a 1000% peak increase in cyclic AMP levels both in amelanotic and melanotic cells. None of these agents influences cyclic GMP or inositol trisphosphate (InsP3) levels. In agreement with the InsP3 assays, phorbol ester (TPA) has no effect on melanization, tyrosinase activity or cell proliferation. In conclusion, in the Bomirski amelanotic melanoma, MSH induces only partial cell differentiation associated with raised levels of cyclic AMP. Induction of melanosome synthesis and melanization by L-tyrosine or L-dopa appear to follow pathways unrelated to cyclic AMP, cyclic GMP or InsP3.

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The effects of fibronectin on the migration of human foreskin fibroblasts and Syrian hamster melanoma cells into three-dimensional gels of native collagen fibres

Journal of Cell Science ◽

10.1242/jcs.48.1.301 ◽

1981 ◽

Vol 48 (1) ◽

pp. 301-314

Author(s):

S.L. Schor ◽

A.M. Schor ◽

G.W. Bazill

Keyword(s):

Human Skin ◽

Syrian Hamster ◽

Melanoma Cells ◽

Skin Fibroblasts ◽

Collagen Gels ◽

Human Skin Fibroblasts ◽

Collagen Fibres ◽

3 Dimensional ◽

Native Collagen ◽

Hamster Melanoma

The effects of fibronectin on the migration of human skin fibroblasts and Syrian hamster melanoma cells into 3-dimensional gels of native collagen fibres have been examined. Cell migration into the 3-dimensional gel was measured by plating cells on the gel surface and then determining the percentage of cells within the gel at various times thereafter by direct microscopic examination. We find that fibronectin bound to collagen inhibits the migration of human skin fibroblasts and stimulates the migration of melanoma cells into the gel matrix. Fibronectin had no apparent effect on cell adhesion to the collagen gels, proliferation or morphology under the conditions studied.

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Dissociation of plasminogen activator from the transformed phenotype in a 5-Bromodeoxyuridine dependent mutant of syrian hamster melanoma cells

Journal of Cellular Physiology ◽

10.1002/jcp.1040950305 ◽

1978 ◽

Vol 95 (3) ◽

pp. 275-285 ◽

Cited By ~ 7

Author(s):

S. L. Rosenthal ◽

D. Zucker ◽

R. L. Davidson

Keyword(s):

Plasminogen Activator ◽

Syrian Hamster ◽

Melanoma Cells ◽

Hamster Melanoma

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Microtubule assembly in cultivated Greene melanoma cells is stimulated by dibutyryl adenosine 3':5'-cyclic monophosphate or cholera toxin.

The Journal of Cell Biology ◽

10.1083/jcb.71.3.735 ◽

1976 ◽

Vol 71 (3) ◽

pp. 735-748 ◽

Cited By ~ 26

Author(s):

A M DiPasquale ◽

J McGuire ◽

G Moellmann ◽

S J Wasserman

Keyword(s):

Cyclic Amp ◽

Cholera Toxin ◽

Gel Electrophoresis ◽

Unit Area ◽

Melanoma Cells ◽

Microtubule Assembly ◽

Dibutyryl Cyclic Amp ◽

Cyclic Monophosphate ◽

Cell Processes ◽

Hamster Melanoma

Both dibutyryl cyclic AMP (DBcAMP) and cholera toxin promote the formation and elongation of processes of cultivated Greene hamster melanoma cells. The formation and maintenance of these processes, which contain many microtubules, are sensitive to colcemid and vinblastine. Tubulin was measured by [3H]colchicine binding and by acrylamide gel electrophoresis. We found that DBcAMP or cholera toxin increases the ratio of polymerized to unpolymerized tubulin but not the total amount of tubulin per cell. The sum of the lengths of microtubules per unit area was significantly greater in cells treated with DBcAMP than in control cells. Our findings support the hypothesis that cyclic AMP promotes the elongation of cell processes by stimulating the assembly of microtubules from existing tubulin.

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