Introduction: Migration of cells involves a complex signaling network. The aim of the present study was to elucidate the impact of Rho-kinase (ROK) on G protein-coupled receptor-induced migration of human transitional cell carcinoma cells in an in vitro experimental setting. Materials and Methods: Intracellular calcium concentration ([Ca2+]i) was measured with the indicator dye Fura-2 in response to lysophosphatidic acid, thrombin and sphingosine-1-phosphate. Phospholipase C activity was determined in myo-[3H]inositol- (0.5 µCi/ml) labeled cells. Migration was performed using a Boyden chamber. Transient transfection of a dominant-negative mutant of ROK was done with calcium phosphate. For staining of actin filaments, tetramethylrhodamine isothiocyanate-conjugated phalloidin was used. Results: Lysophosphatidic acid, thrombin and sphingosine-1-phosphate cause increases in [Ca2+]i, cellular responses being accompanied by an enhancement of phospholipase C activity and sensitive to the Gi inhibitor pertussis toxin. Agonists potently stimulated migration of T24 and J82 cells. Inhibition of Rho proteins by Clostridium difficile toxin B abrogated cell migration. Inhibition of ROK using HA1077 and Y-27632 mimicked the properties of toxin B. Expression of a ROK mutant drastically reduced migration. Conclusions: G protein-coupled receptors potently stimulated cell migration in T24 and J82 cells. Rho proteins and ROK play a pivotal role in this signaling cascade. Rho and ROK may be putative targets for new therapy options in bladder cancer.
Background: Surgery, chemotherapy and radiotherapy are the mainstay of tumor management. However, in systemic disease cure can be achieved in yet a few tumor entities. Based on cellbiological research we have characterized the process of tumor progression and metastasis and disclosed that the loss of cell-cell adhesion in association with an increased tumor cell motility is an essential feature of the malignant potential of a tumor. Methods: According to this principle we derived therapeutical methods differing from hitherto existing treatments by being exclusively focused on tumor cell motility. Characterization of so-called anti-motility factors was performed biochemically as well as with motility assays by in vitro studies in established bladder carcinoma cell lines. Results: We evaluated the potential therapeutic benefit in a model of chemically induced bladder carcinoma followed by a phase I/II trial applying antimotility factors in patients with advanced bladder cancer. Conclusion: Both basic research as well as the results of first clinical trials confirm, that advanced carcinomas can be influenced by inhibition of tumor cell motility.
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