Tobacco smoke makes lung cancer worse

SAN DIEGO, Jan. 20 (UPI) -- Repeated exposure to tobacco smoke makes lung cancer much worse, medical researchers in San Diego found.

Study leader Michael Karin, a professor of the University of California's San Diego School of Medicine, found that mice with early lung cancer lesions that were repeatedly exposed to tobacco smoke developed larger tumors -- and developed tumors more quickly -- than unexposed animals. The key contributing factor was lung tissue inflammation, Karin said.

"We've shown for the first time that tobacco smoke is a tumor promoter -- not only a tumor initiator -- and that it works through inflammation," Karin said in a statement.

"Other particulate materials, such as fine silicon dust, asbestos and coal dust, may promote lung cancer development through similar mechanisms. Such substances were never found to induce mutations, which are the essence of tumor formation."

More research is needed to explore the role and biochemical mechanisms of exposure to pro-inflammatory substances in the environment in early stages of cancer development, Karin said.

The findings are published in the journal Cancer Cell.