The endogenous electric field may provide an important signal for directional cell migration during cancer metastasis but the mechanism of cell electrotaxis is poorly understood. It was postulated that microtubules play a central role in the polarization and directional migration of several types of cells. In this paper we investigated the role of microtubules in electrotaxis of rat Walker carcinosarcoma WC256 cells. We found that colchicine-stimulated disassembly of microtubules caused the formation of blebs instead of lamellipodia at the front of about 45% of cells. Most of the remaining cells contracted and became rounded or transformed into non-polar cells. Depolymerization of microtubules in both subpopulations of cells reduced the directionality of cell migration to about 50% of the control, but bleb- forming cells migrated much more efficiently than lamellipodia-forming cells. The analysis of microtubules architecture in the presence of an endogenous electric field showed that there is no relationship between the direction of migration and the polarization of microtubules. These results suggest that microtubules are not indispensable for electrotaxis of WC256 cells, however they may improve the directionality of cell migration.
Numerous adverse effects limit the applicability of mitoxantrone for the treatment of drug-resistant tumors, including carcinosarcoma. Here, we estimated the additive effects of mitoxantrone and curcumin, a plant-derived biomolecule isolated from Curcuma longa, on the neoplastic and invasive potential of carcinosarcoma cells in vitro. Curcumin augmented the cytostatic, cytotoxic and anti-invasive effects of mitoxantrone on the Walker-256 cells. It also strengthened the inhibitory effects of mitoxantrone on the motility of drug-resistant Walker-256 cells that had retained viability after a long-term mitoxantrone/curcumin treatment. Thus, curcumin reduces the effective doses of mitoxantrone and augments its interference with the invasive potential of drug-resistant carcinosarcoma cells.
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Triterpene saponosides are widely distributed plant secondary metabolites characterized by relatively low systemic cytotoxicity and a range of biological activities. These include anti-inflammatory, antimicrobial, vasoprotective and antitumor properties. In particular, the ability of saponins to enhance the cytotoxicity of chemotherapeutic drugs opened perspectives for their application in combined cancer chemotherapy. Here, we used human prostate cancer DU-145 cells as an in vitro model to elucidate the synergy of the interactions between biological activities of an oleanane type 13β,28-epoxy triterpene saponoside (Lclet 4) and mitoxantrone, which is a cytostatic drug commonly used in prostate cancer therapy. No cytotoxic or pro-apoptotic effect of Lclet 4 and mitoxantrone administered at the concentrations between 0.05 and 0.1 µg/ml could be seen. In contrast, cocktails of these agents exerted synergistic pro-apoptotic effects, accompanied by the activation of the caspase 3/7 system. This effect was paralleled by attenuating effects of Lclet 4/mitoxantrone cocktails on the invasive potential, metalloproteinase expression and motility of DU-145 cells. Multifaceted and additive effects of Lclet 4 and mitoxantrone on basic cellular traits crucial for prostate cancer progression indicate that the combined application of both agents at systemically neutral concentrations may provide the basis for new promising strategies of prostate cancer chemotherapy.
Bronchial asthma is characterized by persistent airway inflammation and airway wall remodeling. Among many different cells and growth factors triggering changes in bronchi structure, transforming growth factor β1-induced fibroblast to myofibroblast transition is believed to be very important. The aim of this study was to evaluate whether theophylline (used in asthma therapy) and two other methylxanthines (pentoxifylline and its active metabolite lisofylline), may affect transforming growth factor β1-induced fibroblast to myofibroblast transition in bronchial fibroblasts derived from asthmatic patients. We show here for the first time that selected methylxanthines effectively reduce transforming growth factor β1-induced myofibroblast formation in asthmatic bronchial fibroblast populations. PTX was found to be the most effective methylxanthine. The number of differentiated myofibroblasts after PTX, LSF and THEO administration was reduced at least twofold. Studies on the use of methylxanthines opens a new perspective in the development of novel strategies in asthma therapy through their two-pronged, anti-inflammatory and anti-fibrotic action. In the future they can be considered as promising anti-fibrotic drugs.
Cellular stress responses determine tissue development, homeostasis and pathogenesis. Paracrine signaling, exchange of mechanical stimuli and intercellular transfer of small metabolites via connexin-built gap junctional channels are involved in the cellular stress detection and propagation of stress stimuli in multicellular networks. Cellular stress responses are also regulated through the activity of unpaired connexons (hemichannels) and via the intracellular interference of connexins with the cell cycle and pro-apoptotic machinery. Therefore, connexins are considered as multidirectional transmitters of the "outside-in" and "inside-out" stress signaling that are crucial for tissue homeostasis, regeneration and pathology. In particular, the disturbance of connexin function during the multi-stage process of tumor development leads to abnormal reactions of tumor cells to stress stimuli. In this review, we outline the current knowledge on the multidirectional role of connexins in the detection of stress signals. We also discuss the role of connexin-mediated intercellular transmittance of stress signals in tumour promotion, progression and metastatic cascade. Highlights: 1. Connexins and gap junctions protect cells from the microenvironmental stress and are involved in propagation and intracellular processing of stress signals. 2. The quality and quantity of stress stimuli, which may lead to cell adaptation or death by apoptosis, is determined by intrinsic properties of connexins and the cell phenotype. 3. Connexin deficiency increases the resistance of tumor cells to the "outside-in" stress signaling. 4. The connexin-mediated "inside-out" stress signaling participates in tumor cell invasion during the metastatic cascade.
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Cationic linear poly-cis-isoprenoid prepared from natural plant polyprenol in a mixture with dioleyl phosphatidylethanolamine was found to be an effective lipofection agent for eukaryotic cells. The transfecting activity is related to the poly-cis structure of the polyprenyl chain.
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