Evaluating Breast Cancer Cell Morphology as a Predictor of Invasive Capacity

Breast cancer is dangerous not for its activity at the initial site but due to the ability of cells within the primary tumor to breach the surrounding basement membrane, invade dense collagen I-rich breast tissue, and ultimately reach and form secondary tumors in distant organs with critical functions. Previous studies on breast cancer cell lines have shown correlations between measures of invasion and static properties including cell aggregate morphology. Specifically, it has been shown that cells demonstrating stellate aggregate morphology typically outperform cell lines demonstrating other aggregate morphologies in the Transwell invasion assay. To further assess whether morphology can be used as a predictor of invasive capacity, six cell lines that have previously been identified as forming putatively aggressive stellate aggregates or less aggressive grape-like aggregates were evaluated for their ability to invade in various contexts- from a simple two dimensional gap migration assay to a more complex three dimensional spheroid invasion assay that recapitulates cell-cell and cell-environment contacts as they exist in vivo in the context of the primary breast tumor. We found that morphology alone was insufficient to predict how well cells performed in each of these assays. Migratory ability on a two dimensional substrate, contractility of the three dimensional environment, and presence of proper integrins for binding to the extracellular matrix also failed to fully predict invasive capacity in a three dimensional environment. Correlations between performance in the three dimensional spheroid invasion assay and gene expression profiles suggest this assay can be used to identify invasive breast cancer cells independent of their morphology.