Smoking may bring on changes in cells that are linked with many cancers, including breast and gynecological cancers, a new study finds. These changes could provide an early warning sign of cancer, particularly in cheek cells, the research showed.

Researchers analyzed cheek swabs from 790 women, and found those who smoked were more likely to have certain changes associated with these cancers, which people may not realize are linked with smoking.

The researchers were looking for epigenetic changes in cells, which are changes in the complex system of chemicals and proteins that attach to DNA and turn genes on and off. Such changes are associated with cancer development and can be caused by exposure to environmental factors such as cigarette smoke.

"Our work shows that smoking has a major impact on the epigenome of normal cells that are directly exposed to the carcinogen," lead author Andrew Teschendorff, a research fellow at the University College London (UCL) Cancer Institute, said in a statement. "This research gets us closer to understanding the very first steps" in cancer's development, he said. The epigenome is network of chemical compounds around DNA that regulates the activity of genes.

The study findings could lead to better ways to predict people's risk of cancer, or to detect it early, Teschendorff said.

Environmental factors, such as smoking, can disrupt a cell's epigenome, eventually leading to the out-of-control cell growth seen in cancer, the researchers said.

In the study, the researchers analyzed the epigenetic changes within cells, and found a "signature" of smoking. By looking for this signature, the researchers found they could differentiate between normal and cancerous tissue with near absolute certainty, including cancers in other parts of the body.  [Kick the Habit: 10 Scientific Quit-Smoking Tips]

The signature could also be used to predict if a pre-cancerous lesion would progress to a full-blown invasive cancer, the researchers said.

The ability to quickly and easily identify such changes in cells could help doctors to predict and prevent cancers, the researchers said.

The researchers also found that cheek cells may be a better indicator of a woman's epigenetic changes than her blood cells. The cheek cells showed a 40-fold increase in abnormal genetic activities, compared with the blood samples taken from the same people.   

"These results pave the way for other studies in which easily accessible cells can be used" to look for epigenetic changes that may indicate a person's cancer risk, said the study's senior author Dr. Martin Widschwendter, of UCL's Institute for Women's Health.

"This is incredibly exciting for women's cancers such as ovary, breast and endometrial cancer, where predicting the cancer risk is a big challenge," Widschwendter said in a statement.

The researchers noted that because the study included only samples from women, it is unclear if the findings apply to men. Although previous epigenetic studies using blood samples have suggested that most smoking-related changes are independent of sex, only further research can prove if that holds true for cheek cells as well.

The study was published May 14 in the journal JAMA Oncology.

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