Visualising the dynamics of live pancreatic microtumours self-organised through cell-in-cell invasion

Pancreatic ductal adenocarcinoma (PDAC) reportedly progresses very rapidly through the initial carcinogenesis stages including DNA damage and disordered cell death. However, such oncogenic mechanisms are largely studied through observational diagnostic methods, partly because of a lack of live in vitro tumour imaging techniques. Here we demonstrate a simple live-tumour in vitro imaging technique using micro-patterned plates (micro/nanoplates) that allows dynamic visualisation of PDAC microtumours. When PDAC cells were cultured on a micro/nanoplate overnight, the cells self-organised into non-spheroidal microtumours that were anchored to the micro/nanoplate through cell-in-cell invasion. This self-organisation was only efficiently induced in small-diameter rough microislands. Using a time-lapse imaging system, we found that PDAC microtumours actively stretched to catch dead cell debris via filo/lamellipoedia and suction, suggesting that they have a sophisticated survival strategy (analogous to that of starving animals), which implies a context for the development of possible therapies for PDACs. The simple tumour imaging system visualises a potential of PDAC cells, in which the aggressive tumour dynamics reminds us of the need to review traditional PDAC pathogenesis.