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

Focal adhesion kinase (pp125FAK) is a nonreceptor tyrosine kinase which colocalizes with integrins to focal contacts, sites where multiple proteins interact to regulate the assembly of the actin cytoskeleton. Autophosphorylation and activation of pp125FAK occur after integrin clustering or cell adhesion to ligands through cognate integrin receptors and are postulated to mediate integrin signaling events. In this report we examined pp125FAK expression and phosphorylation in normal human melanocytes, an adherent human metastatic melanoma cell line (SKMEL28), and a nonadherent human metastatic melanoma cell line (SKMEL1). We show that SKMEL28 cells express constitutively phosphorylated pp125FAK and that pp125FAK phosphorylation in melanocytes is induced by phorbol esters and growth factors present in melanocyte growth medium. Focal adhesion kinase phosphorylation could be enhanced by b1 integrin-activating antibodies in human melanocytes, but not in SKMEL28 cells. In contrast with SKMEL28 cells, constitutive phosphorylation of pp125FAK was not observed in SKMEL1 cells, and incubation with activating b1 integrin antibodies had no effect on pp125FAK phosphorylation. Absence of pp125FAK phosphorylation in SKMEL1 cells was not due to lack of expression of pp125FAK, as shown by immunoprecipitation of the pp125FAK protein from cell lysates. However, b1 integrin expression was significantly less in SKMEL1 cells than in human melanocytes and SKMEL28 cells. This study further supports the importance of integrins in pp125FAK-mediated signaling and indicates that transformation-related changes in pp125FAK phosphorylation exist in human melanocytes and melanoma cells.
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PMID:pp125FAK in human melanocytes and melanoma: expression and phosphorylation. 754 52

Differentiation therapy is an attractive option for the treatment of superficial, localized neoplastic lesions of the skin. Topical application of agents that induce differentiation could selectively inhibit tumor cell growth, inducing a program of cell death with the production of cross-linked protein envelopes as the terminal event of this process at the skin surface, effectively eliminating the neoplastic phenotype. The nonspecific kinase inhibitor staurosporine induces cornified envelope assembly in neoplastic keratinocytes and causes tumor regression (A. A. Dlugosz and S. H. Yuspa, Cancer Res., 51: 4677-4684, 1991). In pursuit of less toxic agents, specific tyrosine kinase inhibitors were tested for the ability to induce differentiation in keratinocyte-derived cells. Of a range of inhibitors tested, only MC was able to induce cross-linked protein and consequent cell death in mouse and human primary normal keratinocytes, 308 neoplastic mouse keratinocytes, HPV-18-infected immortalized human keratinocytes, and human lines SQCC-Y1 (squamous carcinoma) and A431 (epidermoid carcinoma). MC increased cross-linked protein in a dose-dependent manner (0.05-1 mM). To confirm differentiation, MC-treated mouse primary normal keratinocytes were tested for activation of the endogenous cross-linking enzyme transglutaminase, but no association was found between transglutaminase activity and MC-induced protein cross-linking. MC also induced protein cross-linking in the fibroblast cell line NIH3T3 and in B16 melanoma cells, in which cornified envelope assembly is not part of the differentiation process. This cross-linking occurred at 4 degrees C, suggesting a nonphysiological process. Western blot analysis of an in vitro assay with purified EGF receptor showed that MC was able to cross-link the receptor. As in NIH3T3 cells, DTT inhibited cross-linking, suggesting that oxidation of MC or an acceptor group may be required for this effect. Thus, MC does not induce differentiation by a physiological mechanism in epithelial cells but causes chemical protein cross-linking into cornified envelope-like structures at high concentration.
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PMID:The erbstatin analogue methyl 2,5-dihydroxycinnamate cross-links proteins and is cytotoxic to normal and neoplastic epithelial cells by a mechanism independent of tyrosine kinase inhibition. 758 35

Our previous work demonstrated that 12(S)-HETE, a lipoxygenase metabolite of arachidonic acid, promoted B16 amelanotic melanoma (B16a) cell spreading on fibronectin. In the current study, we investigated the biochemical mechanisms of the 12(S)-HETE induced response. 12(S)-HETE treatment resulted in a time-dependent increase in B16a cell spreading on fibronectin, which was blocked by either calphostin C or by genistein but not by H8. Two hours following cell plating, both spontaneous and 12(S)-HETE promoted cell spreading reached their maximum (nearly 100%). Spontaneous cell spreading was inhibited by the select 12-lipoxygenase inhibitor, BHPP, whose inhibitory effect could be overcome by increasing doses of exogenous 12(S)-HETE. 12(S)-HETE-treated B16a cells plated on either fibronectin or cultured on their own extracellular matrix demonstrated increased vinculin and tyrosine-phosphorylated proteins, which were colocalized at focal adhesions. The increase in vinculin localization to focal adhesions appeared to be a post-transcriptional process, since 12(S)-HETE treatment did not alter the overall protein level of vinculin in tumor cells, but resulted in a specific enrichment of vinculin to focal adhesions. Pretreatment of B16a cells with either calphostin C or genistein abolished 12(S)-HETE-increased formation of vinculin- and phosphotyrosine-containing focal adhesions. Immunoblotting using antiphosphotyrosine antibody 4G10 demonstrated, following 12(S)-HETE stimulation, an increased tyrosine phosphorylation of several proteins in focal adhesions; most prominently, a approximately 155 kd protein, a 120-130 kd protein cluster, a 76 kd protein, and a 42/44 kd complex. Immunoprecipitation with anti-phosphotyrosine antibody PY20 revealed increased tyrosine phosphorylation, post 12(S)-HETE stimulation, of proteins migrating at 120, 76, and 42/44 kd, of which the 120 kd protein co-migrated with pp125FAK. Immunoprecipitation with anti-FAK antibody BC-3 followed by immunoblotting with anti-phosphotyrosine antibody RC20H demonstrated a time-dependent hyperphosphorylation of pp125FAK. The present study suggests that 12(S)-HETE promoted melanoma cell spreading on fibronectin involves tyrosine phosphorylation of pp125FAK and protein kinase C- and tyrosine kinase-dependent focal adhesion formation.
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PMID:Melanoma cell spreading on fibronectin induced by 12(S)-HETE involves both protein kinase C- and protein tyrosine kinase-dependent focal adhesion formation and tyrosine phosphorylation of focal adhesion kinase (pp125FAK). 759 7

Focal adhesion kinase (p125FAK), a recently characterized protein localized within focal adhesion plaques, is believed to play a role in extracellular matrix-integrin-mediated signal transduction involving cytoskeletal proteins. We studied p125FAK expression, distribution, and relation to cell migration in six human melanoma cell lines. Western blot analysis detected differential expression of p125FAK among these lines that was directly proportional to the amount of phosphorylated p125FAK. Time-lapse image analysis of the cell lines exhibited 10-fold differences in the mean migration rates on fibronectin-coated substrates. Regression analysis revealed that p125FAK expression correlated significantly with mean migration rate in the six melanoma lines tested. Double immunofluorescent labeling for p125FAK and actin in these lines demonstrated p125FAK plaques that were localized to actin stress-fiber termination sites in the periphery of cells. The number of p125FAK plaques in the melanoma cell lines was heterogeneous, but the cell lines with more p125FAK plaques per cell exhibited significantly higher mean migration rates on fibronectin as compared with cell lines with fewer p125FAK plaques per cell. The findings support the hypothesis that focal adhesion tyrosine kinase modulates cytoskeletal function during melanoma cell migration on fibronectin.
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PMID:Focal adhesion kinase (p125FAK) expression correlates with motility of human melanoma cell lines. 761 62

Interleukin-1 (IL-1) induces programmed growth arrest in human melanoma cells, A375-C6. IL-1 action in these cells is associated with induction of a cell type-specific immediate-early (IE) gene expression program characterized by strong, rapid, and sustained induction of gro-alpha and gro-beta, but transient induction of c-jun, IRG-9, and NAK-1, and lack of induction of c-myc. With the exception of gro-alpha and gro-beta, these IE genes are also associated with growth-stimulatory responses in the melanoma cells, suggesting that the gro-genes may play key roles in the growth arrest action of the cytokine. To elucidate the early intracellular signals associated with IL-1 action, we are studying the second messenger signals and transcription factors required for induction of gro-genes. Here, we present evidence that IL-1-inducible gro-gene expression is dependent on tyrosine kinase signaling. Using gel retardation and transient expression assays, we show that IL-1 causes protein tyrosine phosphorylation-dependent activation of NF-kappa B enhancer binding protein, which then induces transcription of the gro-genes via an NF-kappa B site located 76 base pairs upstream from the cap site. IL-1-activated protein tyrosine phosphorylation is also required for gro-gene induction in human cervical carcinoma cells, HeLa; human fibroblast cells, WI-38; and mouse fibroblast cells, L929. Thus, in diverse cell types, IL-1 induces gro-genes via tyrosine kinase-dependent signals.
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PMID:Interleukin-1-inducible expression of gro-beta via NF-kappa B activation is dependent upon tyrosine kinase signaling. 768 36

Scatter factor (SF), which dissociates epithelial cell colonies into individual cells and stimulates the migration of epithelial cells, is identical to hepatocyte growth factor (HGF), a mitogen for melanocytes, endothelial cells and epithelial cells, including hepatocytes. It was previously shown by cDNA transfection that the mitogenic effect of SF/HGF is mediated by activation of the tyrosine phosphorylation of the c-Met receptor (the c-met proto-oncogene product). In this study, we constructed a cDNA encoding a chimeric receptor composed of the extracellular domain of the epidermal growth factor (EGF) receptor and the transmembrane and cytoplasmic domains of the c-Met receptor. We transfected the cDNA into the B16-F1 mouse melanoma cell line to investigate whether the cell dissociation and motility were mediated through this chimeric receptor following ligand stimulation. The chimeric receptor cDNA was expressed in the transfected cells and the protein product was transported to the cell surface in the correct transmembrane orientation. EGF treatment of the chimeric receptor-expressing cells markedly enhanced tyrosine phosphorylation of the chimeric receptor and led to scattered morphology and enhanced motility. This scattered morphology was inhibited by a tyrosine kinase inhibitor. Based on these results, we concluded that the cell dissociation and motility triggered by SF/HGF were mediated through the cytoplasmic domain of the c-Met receptor by activation of its tyrosine kinase. Thus, it is likely that the different biological effects of SF/HGF are mediated by different intracellular signal cascades.
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PMID:The cell dissociation and motility triggered by scatter factor/hepatocyte growth factor are mediated through the cytoplasmic domain of the c-Met receptor. 768 22

The c-yes proto-oncogene encodes a protein tyrosine kinase, p62c-yes (c-Yes) that belongs to the Src family of non-receptor type protein tyrosine kinases. We compared the levels of c-Yes kinase activity and protein by immune complex kinase assays and immune blot analysis in 20 human melanoma and 10 human melanocyte cell lines. Results show that the average kinase activity of c-Yes in most melanoma cell lines is 5-10-fold higher than that in melanocyte cell lines. The protein level of c-Yes in these melanoma cell lines is correspondingly higher than that in melanocytes. The increase in c-Yes kinase activity is most likely attributable to the elevated protein level because single-strand conformational polymorphism of all structural and functional domains detected no mutations in any of the c-yes coding regions. Subcellular fractionation analysis indicated that c-Yes localizes to the plasma membrane, perinuclear and cytosolic compartments while c-Src predominantly associates with plasma membranes. In melanoma cells in which an elevated level of c-Yes is observed, a protein of 39 kD is heavily phosphorylated on tyrosine. This protein is only observed in melanoma cells and not in melanocytes, suggesting a perturbed signaling pathway in melanoma cells that results in abnormal tyrosine phosphorylation of cellular proteins. These data suggest that derangement of expression of the c-Yes tyrosine kinase may have a role in the malignant progression of the human melanocyte.
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PMID:Elevated expression of protein tyrosine kinase c-Yes, but not c-Src, in human malignant melanoma. 769 Sep 26

Vascular endothelial growth factor (VEGF) is an angiogenic growth factor which binds to two structurally related tyrosine kinase receptors denoted KDR and FLT1. To compare the interaction of VEGF with each receptor, cell lines which express individual receptor subtypes were identified using Northern blot hybridization. Bovine aortic endothelial (ABAE) cells and WM35 melanoma cells were found to express KDR, while FLT1 was primarily expressed on SK-MEL-37. Both receptor subtypes were detected on another melanoma cell line (WM9). Heparin augmented VEGF binding to KDR-expressing cells (ABAE and WM35), but inhibited VEGF binding to FLT1-expressing cells (SK-MEL-37 and WM9). The concentration of heparin required for half maximal stimulation of VEGF binding to KDR-expressing cells (500 ng/ml) was 25 times greater than that required for half maximal inhibition of binding to FLT1-expressing cells (20 ng/ml). In WM9 cells, the effect of heparin was bimodal; low concentration inhibited, while higher concentrations stimulated binding of 125I-VEGF. Placenta growth factor (PIGF-1) is a recently described growth factor structurally similar to VEGF. PIGF-1 had a negligible or no effect on 125I-VEGF binding to KDR-expressing cells (ABAE, WM35), but did complete for binding to FLT1-expressing cells (SK-MEL-37 and WM9). Addition of heparin had no effect on its ability to compete for binding with 125I-VEGF. The data indicate differential regulation of the two VEGF receptors by heparin and extended specificity of FLT1 receptor, but not KDR, for binding PIGF-1 growth factor.
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PMID:VEGF receptor subtypes KDR and FLT1 show different sensitivities to heparin and placenta growth factor. 773 44

In this study, we evaluated the potential role for a specific melanoma-associated chondroitin sulfate proteoglycan core protein, termed NG2, to collaborate with alpha 4 beta 1 integrin in focal contact formation in human melanoma cells. Although melanoma cells adhered to substrata coated with either the alpha 4 beta 1 integrin binding fibronectin synthetic peptide CS1-OVA or anti-NG2 mAbs, no spreading or focal contact formation was observed on either substratum. However, melanoma cells spread and formed focal contacts on "chimeric substrata" coated with CS1-OVA and the anti-NG2 mAb, 9.2.27, indicating that engaging both adhesion receptors changes the adhesion phenotype of melanoma cells by reorganizing the cytoskeleton. The collaboration between the two receptors is specific to fibronectin, since cells adherent on substrata coated with low concentrations of either laminin and 9.2.27 or type IV collagen and 9.2.27 failed to spread, while cells adherent on low concentrations of fibronectin and 9.2.27 exhibited a fully spread morphology. Two selective tyrosine kinase inhibitors, genistein and herbimycin A, totally inhibited cell spreading on the substrata coated with CS1-OVA and 9.2.27, indicating that tyrosine kinase(s) is important for cell spreading and focal contact formation. When cells were cultured on substrata coated with CS1-OVA and 9.2.27, two proteins (M(r) 130,000 and 120,000) were tyrosine phosphorylated in a genistein- and herbimycin A-sensitive fashion. These proteins were not immunologically related to pp125FAK or alpha 4 beta 1 integrin. Importantly, when melanoma cells were cultured on substrata coated with CS1 and then stimulated with 9.2.27-conjugated microsphere beads, formation of focal contacts and stress fibers was also observed, indicating that NG2 can collaborate with alpha 4 beta 1 integrin when each receptor is engaged on distinct and separate substrata. These results demonstrate that NG2 acts as a coreceptor for spreading and focal contact formation in association with alpha 4 beta 1 integrin in melanoma cells and suggest a model in which the NG2 core protein communicates to alpha 4 beta 1 integrin by an inside-out signaling mechanism.
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PMID:Spreading and focal contact formation of human melanoma cells in response to the stimulation of both melanoma-associated proteoglycan (NG2) and alpha 4 beta 1 integrin. 774 21

Human melanocytes respond to several growth factors whose receptors have tyrosine kinase activity. Abnormalities in the expression of tyrosine kinase receptors may play an important role in the initiation and progression of melanoma. We therefore determined the steady-state mRNA expression of five tyrosine kinase receptors, epidermal growth factor receptor (EGF-R), c-met, nerve growth factor receptor (NGF-R), colony-stimulating factor receptor (CSF-R) and c-kit, in eleven human melanoma cell lines with different metastatic potentials in nude mice. All cell lines except for one nonmetastatic line established from a primary melanoma lost expression of c-kit. Expression of the other four tyrosine kinase receptors varied among the lines. The expression level of individual tyrosine kinase receptor did not correlate with the metastatic potential of the cells. These results suggest that metastatic human melanoma cell lines are heterogeneous for expression of tyrosine kinase receptors, with each cell type manifesting a distinct repertoire of receptor tyrosine kinases. The different profile of tyrosine kinase activities in different metastatic melanomas complicates its use for prognosis.
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PMID:Intertumoral heterogeneity of receptor-tyrosine kinases expression in human melanoma cell lines with different metastatic capabilities. 784 8


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