Device to Study the Cell Invasion Behavior and Phenotypic Profile at Single Cell Level

Multiple methods for investigating cell invasion behavior in vitro have proven useful in exploring the mechanisms behind the epithelial-mesenchymal transition (EMT) and EMT-related tumor cell invasion, for example, by revealing that cell heterogeneity existed in EMT. However, several hypotheses and predictions regarding EMT heterogeneity have remained unproven because of the inability to quantitatively profile cell invasion at the single cell level. Here, we present a microfluidic chip that provides the capability of simultaneously investigating single cell invasion behavior, phenotypic diversity, and responsiveness to anti-invasion drugs. By assessing single cell invasion behavior in separate wells, cell-cell contacts and their corresponding interference in the invasion process could be excluded. The chip allowed for both precise quantitation of cell invasion and in situ phenotyping, such that any single cell heterogeneity could be detected and accurately quantified. This study has proven that the proposed hybrid epithelial/mesenchymal cell phenotype exists and is important in the EMT process. The invasion abilities of two cell lines were also assessed, either with or without EMT-promoting or EMT-inhibiting agents, proving that the chip can also be used to assess the effectiveness of antimetastatic agents. This study has demonstrated that the strategy of isolating single cells before studying their invasive properties is correct and that it provides an in vitro method for understanding cell heterogeneity during EMT. This approach also provides a mean of screening for anti-invasion agents that are focused on single cell invasion, a process known to be important for blood-borne metastasis to occur.