AP-1 Transcription Factors and Steroid Hormone Re­ ceptors in Multistage Mouse Skin Carcinogenesis

Tumor development is a multi-step process during which genetic and epigenetic events determine the transition from normal to malignant cellular state. Apart from the fact that tumor cells bear an indefinite proliferative capacity, they also show activation of the signaling pathways that are involved in the transduction of mitogenic stimuli. This activation is either due to overexpression or mutation of signal transduction molecules. Such an example is the activating ras mutations, which are present in 30% of the human tumors and result in persistent signal transduction via the MAP kinase pathway, the PI-3 kinase pathway and possibly other downstream effector pathways.