Fluorescence imaging of actin fine structure in tumor tissues using sir-actin staining

Abstract

Background: The rearrangement of actin cytoskeleton is being increasingly considered a marker of cancer cell activity, but the fine structure and remodeling of microfilaments within tumor tissue still remains unclear. Materials and Methods: We used the recently introduced silicon-rhodamine (SiR)-actin dye to visualize endogenous actin within tissues by confocal or total internal reflection fluorescence microscopy. We established imaging conditions for robust blinking of SiR-actin, which makes this dye applicable for super-resolution localization microscopy, as well as for an efficient background elimination. Results: We studied tumor tissue samples in two mouse models at high resolution and revealed a complex network of thick curved bundles of actin in cancer cells in tumors. This actin pattern differed strongly from that in cancer cells in vitro and in normal tissues. Conclusion: Localization microscopy with SiR-actin provides an efficient way to visualize fine actin structure in tumor tissues. It is potentially applicable to a variety of biological and clinical samples.