Intra- and intercellular circuitry contributing to bladder tumorigenesis. A complex network of molecular signaling is involved in malignant transformation and tumor progression. Mitogenic signals from growth receptors (gray) on the cell surface are conducted along signal transduction pathways (molecules in black) to affect cell-cycle regulation (molecules in purple) and apoptosis (molecules in blue). This leads to gene-expression changes that are controlled by key transcription factors (yellow). The tumor cell also interacts with factors controlling angiogenesis (green) and invasion (orange). Reproduced from Mitra AP, Cote RJ; Annu Rev Pathol (4):2009 [PubMed].