Gender is a risk factor for lung cancer

Area of Science:

• Oncology
• Endocrinology
• Molecular Biology

Background:

• Epidemiological studies indicate women have a threefold higher lung cancer risk than men, even after accounting for smoking levels.
• Endocrine factors are hypothesized to contribute to this gender disparity in lung cancer.
• Human bronchial cells possess estrogen receptors and synthesize estrogens like 17β-estradiol (E(2)), which can be metabolized into potentially harmful compounds.

Purpose of the Study:

• To investigate the role of estrogen metabolism in the gender-dependent difference in lung cancer risk.
• To explore the interaction between cigarette smoking, estrogen metabolism, and DNA damage in lung carcinogenesis.

Main Methods:

• Analysis of estrogen metabolism pathways in human bronchial epithelial cells.
• Investigation of cytochrome p450 1B1 (CYP1B1) activity and its induction by cigarette smoke.
• Examination of DNA adduct formation in cancer-related genes (p53, K-ras) induced by catechol estrogens.

Main Results:

• Cytochrome p450 1B1 (CYP1B1), an enzyme that metabolizes 17β-estradiol (E(2)) into catechol estrogens (4-hydroxyestradiol and 4-hydroxyestrone), is present in bronchial cells and its activity is enhanced by smoking.
• Catechol estrogens are mutagenic and carcinogenic, forming DNA adducts in critical genes like p53 and K-ras.
• Women with lung cancer exhibit distinct p53 mutation patterns and higher K-ras mutation frequencies compared to men.

Conclusions:

• Cigarette smoking acts as a cofactor with 17β-estradiol (E(2)) in promoting lung cancer in women.
• Smoking stimulates the conversion of E(2) into genotoxic metabolites that damage DNA in genes such as p53 and K-ras.
• Estrogen may also contribute to tumor growth by stimulating cellular proliferation.