[Cell signalling and cancer: characterisation of therapeutic targets]

Cellular communication is required for the life of pluricellular organisms. The informations exchanged between cells belong to six major types of order to be executed, opposite each other: proliferate or differentiate; remain attached or migrate; survive or die. The cancer cell is genetically unstable, able to explore all the functions encoded by the genome and to consider every proliferative or migratory advantage for selecting it and transmit it to its descent. All the signalling pathways involved in proliferation or differentiation, in adhesion and migration, in survival and death may be altered by oncogenic alterations. These alterations are precisely those which can be targeted for therapy: from this observation was forged the concept of targeted therapy. We present here some examples of therapeutic targeting at the level of a major proliferation pathway by showing how it was possible to identify and characterise relevant targets, invent original new therapeutic tools and decipher the mechanisms of resistance which occur and hinder the success of targeted therapies. This example is the proliferation signalling pathway which starts from the activation of tyrosine kinase receptors by cognate growth factors and ends by the activation of transcription factors which trigger the transcription of the genes required for DNA replication, after undergoing through numerous intermediate molecules constituting the MAP kinase pathway: RAS, RAF, MEK and ERK.