In previous DREAM-High activities, we studied cancer patient data from TCGA. Here we switch to a different kind of cancer model: **human cancer cell lines**. Cancer cell lines are cells that can grow in the laboratory. Researchers use them to study cancer biology and to test hypotheses about cancer behavior. In this activity, we will compare two breast cancer cell lines: - **T-47D** - **MDA-MB-231** We will ask: > Do differences in cell movement correspond to differences in gene expression? This is a core idea in systems biology: we connect a measurable behavior, or **phenotype**, to molecular data.