Some DNA mutations that promote cancer may work through extra copies not of genes, but of genetic regulatory sequences.

Duplications of the chromosomal sequences 17q23 and 20q13 predict poorer outcomes in certain breast cancers — but no genes in these regions suggest a mechanism for how. Tim Huang and co-workers at the University of Texas Health Science Center in San Antonio sequenced genomic regions that physically interact with other stretches of DNA that bind to the oestrogen receptor, a protein complex implicated in breast cancer. This identified sites within 17q23 and 20q13 called distant oestrogen response elements (DEREs), which help the genetic material to form loops that interact with far-off genomic regions. Extra DEREs promoted more looping and deregulated genes in ways expected to promote tumour growth.

Cancer Cell 24, 197–212 (2013)