Somatically acquired loss-of-heterozygosity (LOH) is extremely common in cancer; deletions of recessive cancer genes, miRNAs, and regulatory elements, can confer selective growth advantage, whereas deletions over fragile sites are thought to reflect an increased local rate of DNA breakage. However, most LOHs in cancer genomes remain unexplained. Here we plan to combine a TALEN technology and the experimental models of cell transformation derived from primary human cells to delete specific chromosomal regions that are frequently lost in cancer samples. The development of novel strategies to introduce large chromosomal rearrangements into the genome of primary human cells will offer new perspectives for studying gene function, for elucidating chromosomal organisation, and for increasing our understanding of the molecular mechanisms and pathways underlying cancer development.Using this technology to genetically engineer cells that model cancer-associated genetic alterations, we will identify LOH regions critical for the development and progression of human cancers, and will investigate the cooperative effect of loss of genes, non-coding RNAs, and regulatory elements located within the deleted regions on cancer-associated phenotypes. We will assess how disruption of the three-dimensional chromosomal network in cells with specific chromosomal deletions contributes to cell transformation. Isogenic cell lines harbouring targeted chromosomal alterations will also serve us as a platform to identify compounds with specificity for particular genetic abnormalities. As a next step, we plan to unravel the mechanisms by which particular homozygous deletions contribute to cancer-associated phenotypes. If successful, the results of these studies will represent an important step towards understanding oncogenesis, and could yield new diagnostic and prognostic markers as well as identify potential therapeutic targets.