RESUMEN
Introduction: C60 fullerene has received great attention as a candidate for biomedical applications. Due to unique structure and properties, C60 fullerene nanoparticles are supposed to be useful in drug delivery, photodynamic therapy (PDT) of cancer, and reversion of tumor cells' multidrug resistance. The aim of this study was to elucidate the possible molecular mechanisms involved in photoexcited C60 fullerene-dependent enhancement of cisplatin toxicity against leukemic cells resistant to cisplatin. Methods: Stable homogeneous pristine C60 fullerene aqueous colloid solution (10-4 Ð, purity 99.5%) was used in the study. The photoactivation of C60 fullerene accumulated by L1210R cells was done by irradiation in microplates with light-emitting diode lamp (420-700 nm light, 100 mW·cm-2). Cells were further incubated with the addition of Cis-Pt to a final concentration of 1 µg/mL. Activation of p38 MAPK was visualized by Western blot analysis. Flow cytometry was used for the estimation of cells distribution on cell cycle. Mitochondrial membrane potential (Δψm) was estimated with the use of fluorescent potential-sensitive probe TMRE (Tetramethylrhodamine Ethyl Ester). Results: Cis-Pt applied alone at 1 µg/mL concentration failed to affect mitochondrial membrane potential in L1210R cells or cell cycle distribution as compared with untreated cells. Activation of ROS-sensitive proapoptotic p38 kinase and enhanced content of cells in subG1 phase were detected after irradiation of L1210R cells treated with 10-5M C60 fullerene. Combined treatment with photoexcited C60 fullerene and Cis-Pt was followed by the dissipation of Δψm at early-term period, blockage of cell transition into S phase, and considerable accumulation of cells in proapoptotic subG1 phase at prolonged incubation. Conclusion: The effect of the synergic cytotoxic activity of both agents allowed to suppose that photoexcited C60 fullerene promoted Cis-Pt accumulation in leukemic cells resistant to Cis-Pt. The data obtained could be useful for the development of new approaches to overcome drug-resistance of leukemic cells.
RESUMEN
The adaptor protein regulator for ubiquitous kinase/c-Cbl-interacting protein of 85kDa (Ruk/CIN85) was found to modulate HER1/EGFR signaling and processes like cell adhesion and apoptosis. Although these features imply a role in carcinogenesis, it is so far unknown how and by which molecular mechanisms Ruk/CIN85 could affect a certain tumor phenotype. By analyzing samples from breast cancer patients, we found high levels of Ruk(l)/CIN85 especially in lymph node metastases from patients with invasive breast adenocarcinomas, suggesting that Ruk(l)/CIN85 contributes to malignancy. Expression of Ruk(l)/CIN85 in weakly invasive breast adenocarcinoma cells deficient of Ruk(l)/CIN85 indeed converted them into more malignant cells. In particular, Ruk(l)/CIN85 reduced the growth rate, decreased cell adhesion, enhanced anchorage-independent growth, increased motility in both transwell migration and wound healing assays as well as affected the response to epidermal growth factor. Thereby, Ruk(l)/CIN85 led to a more rapid and prolonged epidermal growth factor-dependent activation of Src, Akt and ERK1/2 and treatment with the Src inhibitor PP2 and the PI3K inhibitor LY294002 abolished the Ruk(l)/CIN85-dependent changes in cell motility. Together, this study indicates that high levels of Ruk(l)/CIN85 contribute to the conversion of breast adenocarcinoma cells into a more malignant phenotype via modulation of the Src/Akt pathway.
