Contributed Talk

Growing tumor spheroids from single cells is associated with changes in cell volume and mechanical properties

Vaibhav Mahajan¹, Keshav Gajendra Babu¹, Timon Beck^1,2, Antje Garside¹, Carsten Werner³, Raimund Schlussler^1,4, Anna Taubenberger¹

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Tumors are mechanically altered across multiple spatial scales, from the cellular level to complex tissues and these changes are thought to contribute to cancer progression. Effects of mechanically altered microenvironments on tumor cells are well studied in a systematic manner using bioengineered 3D in-vitro models. Previous studies indicate that tumor spheroids adapt their growth and mechanical properties when growing under 3D confinement. Still, the temporal dynamics and molecular basis of this mechanical adaption remain poorly understood. Here we studied single cancer cells forming tumor spheroids in mechanically well-defined 3D hydrogels. Confocal Brillouin microscopy revealed for several cell types consistent increases in the Brillouin frequency shift from single cells, to small clusters and tumor spheroids. These changes coincided with a drastic decrease in the median nuclear volume of up to 60%, together with overall cell volume decreases. The volume changes were not explained by growth-induced compressive stress but rather by both, water efflux from the cells, as well as cell cycle changes evidenced by the FUCCI cell cycle reporter. Specifically, smaller cells that were in the G1 cell cycle phase accumulated in the growing spheroids over time. Taken together, our study provides insights into how tumor cells adapt their cellular and nuclear volumes and mechanical properties when forming multicellular structures in 3D, which is relevant to tumor formation and progression.