Visualization of the Invadosome Actin Core Arrangement in Cancer Cells

Invadosome-mediated matrix degradation is a hallmark of cancer metastasis, yet the architecture of these invasive structures, which mainly consist of actin cores, has not been well characterized. Here, we visualized the actin core of the invadosome of MDA-MB-231 cells, a highly invasive breast cancer cell line, by confocal microscopy and showed that the actin cores had a rosette-like arrangement near the nucleus. Then, high-resolution light microscopy was utilized to characterize the actin cores of the invadosome induced by TGF-β, which may resemble the conditions in metastasis. The resulting three-dimensional views of the actin cores showed that they were circularly arranged and assembled into a barrel-like structure elongating toward the interface of the cells with an extracellular matrix, suggesting that they might be correlated with the invasion of the cancer cells. Statistics were also made to evaluate the structural features of the actin core assemblies by measuring their distribution, area, and quantity. Furthermore, inhibitors targeting actin assemblies and the corresponding pathways were applied to investigate the structural changes of actin rosettes, which showed that different inhibitors had different impacts on the actin core arrangement and cell invasiveness. Overall, these results suggest that the actin cores of the invadosome have specific structural features that may correlate with the invasiveness of cancer cells, and the structural information may provide mechanistic insights for tumor cell invasion and facilitate therapeutic strategies against cancer.