The biology of cancer is a complex interplay of many underlying processes, taking place at different scales both in space and time. A variety of theoretical models have been developed, which enable to study certain components of the cancerous growth process. However, most previous approaches only focus on specific aspects of tumour development, largely ignoring the influence of the evolving tumour environment. In contrary, we present an integrative framework to simulate tumour growth, including those model components, which are considered to be of major importance. We start by addressing issues at the tissue level, where the phenomena are modelled as continuum partial differential equations. We extend this model with relevant components at the cellular or even sub-cellular level in a vertical fashion. We present an implementation of this framework, covering the major processes and treat the mechanical deformation due to growth, the biochemical response to hypoxia, blood flow, oxygenation and the explicit development of a vascular system in a coupled way. We also report on first efforts to validate certain aspects of the developed modeling and simulation framework by relying on murine tumour models. We are currently concentrating on the initialization of a realistic vascular model based on in vivo imaging observations, which is a necessary pre-condition of making meaningful comaprisons between predictive simulation and actual in vivo observations. Our results demonstrate the feasibility of the approach and its applicability to in silico studies of the influence of different treatment strategies (like the usage of novel anti-cancer drugs) for more effective therapy design.