Smoking cigarettes substantially increases a person's risk of developing heart disease, as well as cancer of the mouth, pharynx, larynx, esophagus, pancreas, kidney, bladder and uterine cervix. Whether cigarette smoking increases the risk of breast cancer risk remains controversial.

Studies that have looked at the relationship between tobacco and breast cancer have found only weak correlations or none at all. Most of these studies, however, have focused on single chemical components of tobacco.

For their research, the Gainesville team used cigarette smoke condensate or tar that contains all of the chemicals present in cigarette smoke, 81 of which have been classified as cancer-causing.

"The use of cigarette smoke condensate...mimics the human smoking situation more closely," Dr. Satya Narayan told Reuters Health.

Narayan and colleagues found that after treatment with cigarette smoke condensate normal human breast epithelial cells in culture acquire mutations characteristic of malignancy. "The concentration of the condensate we used is much lower than it is present in one cigarette," Narayan pointed out.

The Gainesville research also pinpoints the mechanism by which cigarette smoke transforms normal breast cells into cancerous cells. Cigarette smoke "causes DNA damage and at the same time compromises the DNA repair capacity of the cell, perhaps, leading to mutation and transformation of targeted breast epithelial cells."

A DNA repair defect in a single cell that cannot be repaired efficiently before it divides can lead to the genesis of tumors, Narayan said.

When people smoke, they inhale 4,000 different chemicals, which can produce harmful effects in our body, Narayan said. Since the development of cancer is a complex phenomenon and requires several gene mutations during its progression, the defective cell can be present for several years before it acquires tumorigenic activity, the researcher added.

Therefore, the safest way around this is to stay away from cigarettes. "This will protect us from the long-term known and unknown causes of cigarette smoke chemicals on our health," Narayan said.

SOURCE: Oncogene, August 21, 2006.