Filing Date: 2006-07-28.- Priority Data: EP 05076753.2 (2005-07-28).The invention relates to the graded expression level of SNAIL gene or its expression products, as a marker of the capacity of epithelial and mesenchymal tumours and/or cancers for disseminating to other tissues or organs. The invention further relates to a transgenic non-human mammal comprising in its genome a transgene that comprises a nucleic acid sequence encoding the SNAIL protein, and the use of SNAIL as a marker of epithelial and mesenchymal tumours and/or cancers as well as in DNA damage-based diseases In addition, the invention relates to the use of SNAIL as a therapeutic and diagnostic target for said pathologies.Peer reviewed