Ask AI: Propose a step-by-step approach to design a vascularised cancer spheroid in vitro model. Illustrate your answer where possible

. Step 1: Obtain tumor cells, endothelial cells and extracellular matrix (ECM) components of sufficient quality for use in the model. Step 2: Seed the tumor cells in a spherical mold and culture the cells in sufficient nutrients and oxygen. Ensure the cell density is kept high so the cells grow together. Step 3: Place the mold with the seeded tumor cells on an ECM gel or substrate and allow the tumor cells to adhere and spread. Step 4: Add endothelial cells to the tumor tissue and allow them to attach, spread and grow. Step 5: Incubate the tumor and endothelial cells in a culture medium with well-defined conditions that promote the growth and proliferation of both cell types. Step 6: Monitor the tumor cell-endothelial cell interactions and the formation of vascular channels in the spheroid for up to 3 weeks. Step 7: Introduce drugs or other treatments to the model to study their efficacy and observe the response of the tumor and endothelial cells.