( ng these molecules is disturbed. Wh...)A new link between stem cells and tumors

Whether Prospero and its partners get to the right place depends on the activity of specific genes in the stem cell. EMBL PhD student Emmanuel Caussinus from Gonz�lez's group created neuroblasts in which these genes were disrupted. "We no longer had normal neuroblasts and daughter cells capable of becoming part of a nerve," Caussinus says. "Instead, we had a tumor."

When these altered cells were transplanted into flies, the results were swift and dramatic. The tissue containing the altered cells grew to 100 times its initial size; cells invaded other tissues, and death followed. The growing tumor became "immortal", Caussinus says; cells could be retransplanted into new hosts for years, generation after generation, with similar effects.

The study proves that specific genes in stem cells ?those which control the fates of daughter cells ?are crucial. If such genes are disrupted, the new cells may no longer be able to control their reproduction, and this could lead to cancer. "It puts the focus on the events that create asymmetrical collections of molecules inside stem cells," Gonz�lez says. "This suggests new lines of investigation into the relationship between stem cells and tumors in other model organisms and humans."