Since the sequencing of the human genome in 2001, all our genes – around 20,000 in total – have been identified. But much is still unknown – for instance where and when each is active. Next to each gene sits a short DNA segment, and the activity of this regulatory segment determines whether the gene will be turned on, where and how strongly. These short regulatory segments are as – if not more – important than the genes, themselves. Indeed, 90% of the mutations that cause disease occur in these regulatory areas. They are responsible for the proper development of tissues and organs, determining, for instance, that eye cells – and only eye cells – contain light receptors, while only pancreatic cells function to produce insulin. Clearly, a deeper understanding of this regulatory system – its mechanisms and possibilities for malfunction – may lead to advances in biomedical research, especially in developing targeted therapies for individual patients.

Scientists at Mount Sinai School of Medicine have discovered a subpopulation of cells that display cancer stem cell properties and resistance to chemotherapy, and participate in tumor progression. This breakthrough could lead to the development of new tests for early cancer diagnosis, prognostic tests, and innovative therapeutic strategies, as reported in Cancer Cell.