Abstract
Tumour metastasis is a complex process that strongly influences the prognosis and treatment of cancer. Apart from intracellular factors, recent studies have indicated that metastasis also depends on microenvironmental factors such as the biochemical, mechanical and topographical properties of the surrounding extracellular matrix (ECM) of tumours. In this study, as a proof of concept, we conducted tumour spheroid dissemination assay on engineered surfaces with micrograting patterns. Nasopharyngeal spheroids were generated by the 3D culture of nasopharyngeal carcinoma (NPC43) cells, a newly established cell line that maintains a high level of Epstein-Barr virus, a hallmark of NPC. Three types of collagen I-coated polydimethylsiloxane (PDMS) substrates were used, with 15 μm deep "trenches" that grated the surfaces: (a) 40/10 μm ridges (R)/trenches (T), (b) 18/18 μm (R/T) and (c) 50/50 μm (R/T). The dimensions of these patterns were designed to test how various topographical cues, different with respect to the size of tumour spheroids and individual NPC43 cells, might affect dissemination behaviours. Spreading efficiencies on all three patterned surfaces, especially 18/18 μm (R/T), were lower than that on flat PDMS surface. The outspreading cell sheets on flat and 40/10 μm (R/T) surfaces were relatively symmetrical but appeared ellipsoid and aligned with the main axes of the 18/18 μm (R/T) and 50/50 μm (R/T) grating platforms. Focal adhesions (FAs) were found to preferentially formed on the ridges of all patterns. The number of FAs per spheroid was strongly influenced by the grating pattern, with the least FAs on the 40/10 μm (R/T) and the most on the 50/50 μm (R/T) substrate. Taken together, these data indicate a previously unknown effect of surface topography on the efficiency and directionality of cancer cell spreading from tumour spheroids, suggesting that topography, like ECM biochemistry and stiffness, can influence the migration dynamics in 3D cell culture models.