h-89 and Skin-Neoplasms

The serine/threonine kinase protein kinase D (PKD) has been proposed to be a pro-proliferative, anti-differentiative signal in epidermal keratinocytes. Indeed, the phorbol ester tumor promoter, 12-O-tetradecanoylphorbol 13-acetate (TPA) induces biphasic PKD activation, which mirrors the biphasic response of initial differentiation followed by proliferation and tumor promotion seen in TPA-treated keratinocytes in vitro and epidermis in vivo.. Our objective was to test the idea that PKD's pro-proliferative and/or anti-differentiative effects in keratinocytes contribute to TPA-induced tumorigenesis.. Using western analysis and assays of keratinocyte proliferation and differentiation, we investigated the effect of inhibitors of PKD on keratinocyte function.. We found that overexpression of a constitutively active PKD mutant increased, and of a dominant-negative PKD mutant decreased, keratinocyte proliferation. A recently described selective PKD inhibitor showed low potency to inhibit keratinocyte proliferation or PKD activation. Therefore, we tested the ability of known only relatively selective PKD inhibitors on keratinocyte function and protein kinase activation. H89 {N-[2-(p-bromocinnamylamino) ethyl]-5-isoquinoline-sulfonamide}, a reported inhibitor of PKD and cAMP-dependent protein kinase, enhanced the effect of a differentiating agent on a marker of keratinocyte differentiation. Another reported non-selective PKD inhibitor, resveratrol stimulated differentiation and inhibited proliferation. The protein kinase C/PKD inhibitor Gö6976 blocked the increase in proliferation (as measured by DNA specific activity) induced by chronic TPA without affecting the initial TPA-elicited differentiation.. Our results support the idea that relatively selective PKD inhibitors, such as Gö6976, H89 and resveratrol, might be useful for preventing/treating epidermal tumorigenesis without affecting keratinocyte differentiation.

Topics: Animals; Anticarcinogenic Agents; Carbazoles; Cell Differentiation; Cell Proliferation; Cells, Cultured; Epidermis; Isoquinolines; Keratinocytes; Mice; Protein Kinase C; Protein Kinase Inhibitors; Resveratrol; Skin Neoplasms; Stilbenes; Sulfonamides; Tetradecanoylphorbol Acetate

Interleukin-6 (IL-6) is a bifunctional growth factor in malignant melanoma; its expression increases during the malignant progression of the disease. Histamine, detected in large amounts in normal and pathological proliferating tissues, is an important paracrine and autocrine regulator of normal and tumour cell proliferation as well.. We investigated the presence and function of IL-6 and histamine in the WM35 primary human melanoma cell line with respect to their direct role in cell proliferation and their regulatory interactions.. IL-6 inhibited the proliferation of WM35 melanoma cells and increased significantly the expression of histidine decarboxylase as well as histamine production. It had dose-dependent effects on the proliferation: high concentration (10-5 M) was inhibitory through H1 histamine receptors while low histamine concentration acting on H2 receptors, with a simultaneous increase of cAMP, enhanced colony formation in the monolayer. Furthermore, IL-6 increased the H1- but decreased the H2-histamine receptor expression of the melanoma cells. On the other hand, histamine was locally synthesized by the WM35 melanoma cells.. We suggest that the growth arrest induced by IL-6 is in part mediated by its dual action on histamine: a shift toward H1 receptor predominance and an elevation of locally produced histamine with prevalent action on the inhibitory response triggered through the H1 receptor. These findings suggest a local cross-talk between histamine and IL-6 in the regulation of melanoma growth.

Topics: 8-Bromo Cyclic Adenosine Monophosphate; Bucladesine; Cell Division; Colforsin; Cyclic AMP-Dependent Protein Kinases; Dose-Response Relationship, Drug; Drug Synergism; Enzyme Inhibitors; Gene Expression; Guanidines; Histamine; Histamine H1 Antagonists; Histamine H2 Antagonists; Humans; Imidazoles; Interleukin-6; Isoquinolines; Melanoma; Polymerase Chain Reaction; Receptors, Interleukin-6; Skin Neoplasms; Sulfonamides; Tumor Cells, Cultured

Binding of integrins to the extracellular matrix (ECM) activates various signal transduction pathways and regulates gene expression in many cell types. Integrin-dependent cytoplasmic protein/protein interactions are necessary for activation of those signal transduction cascades. In our studies we investigated a possible association of pp125FAK, an adhesion involved tyrosine kinase, with the integrin beta 1 subunit. Further we wanted to know to which extent protein tyrosine phosphorylation affects cell adhesion to the ECM and the possible beta 1 integrin/pp125FAK complex. We were able to show that in HaCaT cells (a human keratinocyte derived cell line) the integrin beta 1 subunit is associated with tyrosine kinase pp125FAK. This association was observed in ECM-adherent cells and nonadherent cells and is independent of tyrosine phosphorylation. However, cell adhesion of HaCaT cells to specific substrates requires tyrosine phosphorylation since genistein treatment that blocks phosphorylation of many cellular proteins as pp125FAK led to a reduced substrate adhesion.

Topics: Carcinoma, Squamous Cell; Cell Adhesion; Cell Adhesion Molecules; Cyclic AMP-Dependent Protein Kinases; Enzyme Inhibitors; Extracellular Matrix; Fibronectins; Focal Adhesion Kinase 1; Focal Adhesion Protein-Tyrosine Kinases; Genistein; Humans; Integrin beta1; Isoquinolines; Keratinocytes; Macromolecular Substances; Neoplasm Proteins; Phosphorylation; Polyhydroxyethyl Methacrylate; Polylysine; Protein Kinase C; Protein Processing, Post-Translational; Protein-Tyrosine Kinases; Signal Transduction; Skin Neoplasms; Sulfonamides; Tumor Cells, Cultured