Scale-free aggregation and interface fluctuations of cancer clusters in cancer-endothelial cell mixtures: From the dilute state to confluent monolayer

We experimentally investigate the multiscale dynamical and scaling behaviors of the morphology, motion, and area distribution of segregated cancer clusters of proliferating cancer-endothelial cell mixtures, from the initial randomly distributed dilute state to the jammed confluent monolayer state. Cancer cells (CCs) have higher motilities than endothelial cells (ECs) and weaker CC-EC and CC-CC cohesive couplings than EC-EC coupling. It is found that, with increasing waiting time tw, CCs proliferate, move, and aggregate into clusters with fractal cluster boundaries, increasing averaged cluster area, and the gradual transition to the self-similar power-law distribution of single cluster areas. In CC clusters, multiscale turbulentlike motion and the interaction with surrounding ECs are the keys for self-similar multiscale spatial fluctuations of the velocities and fractal structure of CC cluster boundaries. The larger CC cluster allows stronger longer-length fluctuations. It causes the increasing fractal dimension and scaling exponents of the relative motion of CC cluster boundaries, which can be suppressed by proliferation-induced crowding and dynamical slowing down.