Cancer has become the leading cause of disease death for middle aged Americans, while the overall effectiveness of therapeutic treatments is less than 50%.  At the same time, after a quarter century of rapid advances, cancer research has generated a rich a complex body of knowledge. We have developed a cell-based, multiscale modeling framework to model cancer development based on this body of knowledge. Our model includes a cellular model for cell dynamics (cell growth, division, death, migration and adhesion), an intracellular protein regulatory network for cell cycle control and a signaling network for cell decision-making, and extracellular reaction-diffusion chemical dynamics. This model has produced avascular tumor growth dynamics that agree with tumor spheroid experiments; it has generated realistic sprout patterns in tumor-induced angiogenesis; it has also shown potential for investigating chemotherapeutic strategies for tumor. Given the biological flexibility of the model, we believe that it can facilitate a deeper understanding of the cellular and molecular interactions associated with cancer progression and treatment, and potentially guide experimental design and interpretation.