"Mucus is a barrier against all sorts of stress," Kufe comments. "Take your stomach, for example. It's a highly acidic place, you need mucus to prevent that acid from corroding your stomach wall."

If this barrier starts to break down, the MUCI molecule sends signals to the nucleus and mitochondria, the cell's command and energy centers. Through a complex process, not yet fully understood, the cell's machinery repairs breaks and holes in the protective sheath. But this neat survival mechanism also protects cancer cells.

"To survive, tumor cells have to adapt to stressful situations, too," Kufe explains. "They may outgrow their blood supply, be choked by a lack of oxygen, or attacked by cancer drugs. Cancer cells are very clever; they have pirated the mucus-signaling mechanism that evolved to protect normal cells. The difference is that tumor cells keep this machinery working all the time, while in normal cells it operates only when repair work is needed."

As long as the MUC1 system works, tumor cells can defend themselves against drugs and radiation. "But now that we understand how the system works, we can develop approaches that target MUC1 signals," Kufe notes. With the signals down, tumor cells would lose their protection and die, or become more susceptible to treatment. In addition to vaccines, Kufe's lab is thinking about how drugs might be made to disrupt the on-off mucus signals.

The scenario sounds good, but Kufe is cautious. "Cancer is a very complex disease," he admits. "Many pitfalls and false leads lie in the way of developing new and better treatments. We have found a novel mechanism that contributes to many cancers, but whether or not we can successfully exploit that mechanism remains to be seen."