Cytoskeleton Dynamics Following Plasmonic Cell Fusion

Cell fusion is an important natural physiological process that occurs during normal development and in various disease phases, including cancer growth and metastasis. One of the key requirements for cancer cell motility is the dynamic reorganization of its actin cytoskeleton, which is critical for transdifferentiation of epithelial-like cells into motile mesenchymal-like cells, a key process in embryonic development, wound healing and cancer progression. Various methods have been used for artificial induction of cell fusion, including the use of PEG molecules, electric fields and focused laser beams. Our research group has recently presented an additional method for selective induction of cell fusion using specific gold nanoparticles and irradiation by intense femtosecond laser pulses. Here, we study cytoskeletal dynamics in fused MDA-MB-468 breast cancer cells that were targeted with anti-EGFR coated gold nanospheres and irradiated by a high-power femtosecond beam at 550 nm wavelength that matches the particles’ plasmonic resonance. The cells, which were transfected by a lentivirus for continuous expression of mCherry on their actin filaments, were imaged using time-lapse confocal microscopy for identifying spatiotemporal cytoskeletal dynamics. Immediately after irradiation, the actin cytoskeleton in each cell appeared to maintain its general orientation before the fusion. Over time, local interaction were observed between actin networks in neighboring fused cells. Ten hours after fusion between multiple cells, widespread actin network was observed covering the entire multinucleated giant hybrid cell. Long-range order was clearly noticed across the fusion product, yet with residual local orientations that resembled that of the original cells. The results suggest the cytoskeleton continues to evolve and regenerate in the large multinucleated fusion product. Further study of the mechanisms involved during and following plasmon-triggered cell fusion may help controlling this unique process and find potential applications in the fields of biotechnology, cancer research and tissue regeneration.