[The cellular mechanisms of photocarcinogenesis]

UV radiations can act as a complete carcinogenic factor, being capable to initiate and also to promote the tumoral process. They usually act by altering the DNA and also the cell functions involved in cell differentiation. In the last decade important progresses were made in understanding the genetic bases of cancer by the discovering of the protooncogenes. Their normal function is vital for the optimal regulation of cell growth and differentiation; alter of their structure or regulation of their expression under the viral action, ionic radiations or chemical substances can determine cancer development.