Direct visualization of emergent metastatic features within anex vivomodel of the tumor microenvironment

Abstract

ABSTRACTPreventing tumors from acquiring metastatic properties would dramatically reduce cancer mortality1–4. The emergence of metastatic cells is promoted by interactions with stromal cells under environmental conditions such as hypoxia and nutrient-deprivation5–11. Unfortunately, these conditions arise deep within tumor tissues – a far from the vasculature – and thus the observation of nascent metastases has been exceedingly challenging. We present anex vivomodel of the tumor microenvironment that enables the observation of tumor cells in their native 3D context with high spatial and temporal resolution. In this system, called 3MIC, tumor cells spontaneously create ischemic conditions so we can study how they impact the emergence of pro-metastatic features. Consistent with previous experimental and clinical data, we showed that ischemic-like conditions in the 3MIC increase cell migration and invasion in tumor spheroids formed from a panel of established and freshly derived tumor lines. The 3MIC allowed us to precisely observe when these pro-metastatic features emerge, to track ischemic cells with single cell resolution, and to directly observe how these cell behaviors change upon interactions with stromal cells. We used the 3MIC to observe the effects of drugs targeting cell migration and we found evidence that ischemic cells acquire resistance to paclitaxel. Overall, the 3MIC allows us to directly observe the emergence of metastatic tumor features in a physiologically relevant model of the tumor microenvironment. This simple and cost-effective system can dissect the complexity of the tumor microenvironment to test perturbations that may prevent tumors from becoming metastatic.