Oregon Public Broadcasting

Cigarette smoking causes 87 percent of lung cancer deaths. But until now, researchers didn't know the medical step-by-step that turned cigarette smoke into cancerous cells.

Ethan Lindsey reports that Tuesday, an Oregon researcher says she's made the link. Her new study is published in the British Journal of Medicine.

Professor Laura Hays is a member of the Oregon Health & Science University Cancer Institute.

She says in the lab, she created a fake windpipe from donated human cells. And when she started poking at it, one protein jumped out of the Petri dish - figuratively - because it acts as sort of an internal physician that heals human cells.

This 'Protein, M.D.,' is called FANC-D2.

Laura Hays: “FANC-D2 works more like a doctor, where after you get hurt, you go in and see the doctor and the doctor works to fix the problem.”

Hays says the human body makes less of the protein when you smoke. And so with fewer tiny doctors in your body, when you smoke again, things get worse.

Laura Hays: “Once you smoke, this protein goes down, so its like you have either less visits to the doctor because the doctor is less available. Or the doctor's not there.”

Hays says in the future, the discovery may help scientists find new ways to treat lung disease.