Until now, most researchers believed that more than one cancer-causing mutation needed to take place in a single cell in order for tumors to grow. Tian Xu, from Yale University (Connecticut, USA), and colleagues have discovered that cancer-causing mutations can cooperate to promote tumor development even when they are located in different cells within a tissue. The researchers used a fruit fly model to study the activity of two genes known to be involved in development of human cancers: a gene called RAS that has been implicated in 30% of cancers, and a tumor-suppressing gene called scribble, which contributes to tumor development when mutated. While neither a mutated RAS nor the defective scribble alone can cause cancer, this research team previously showed that a combination of the two within the same cell could trigger malignant tumors. In the current study, the team found that these mutations did not have to co-exist in the same cell to cause tumors. A cell with only mutant RAS can develop into a malignant tumor if helped by a nearby cell with defective scribble. They also found stress conditions such as a wound could trigger cancer formation. Underlying both phenomena the researchers identified a signaling process called JNK, which is activated by environmental stress conditions.
