Cells and tissues are some of the most sophisticated materials we know. These biological materials are soft and comprised of polymer networks that interact with molecular motors to drive complex functions. In this talk, we will examine the biological physics of cell spheroids, which are aggregates of cells embedded in a fibrous collagen network. The cells remodel and pull on the collagen network to spread out and invade the network, reminiscent of metastasizing

cancers. We show that fibroblasts and their cytoskeletal polymer vimentin is essential for this process. Specifically, vimentin increases spheroid contractile force generation, tissue fluidity, and nuclear elongation, all necessary steps for collective cell invasion through collagen networks. Further, vimentin’s effects in 3D, collective cell, collagen settings are surprising from its perceived functions when studied in comparison to cell spread on 2D glass cover slips. Vimentin is overexpressed and a marker of many different types of cancers, such that understanding its role in the biological physics of cancer can help reveal new therapeutic targets for disease.