In premenopausal women, the pituitary gonadotropin Luteinizing Hormone (LH) is a main regulator of ovarian estrogen production by stimulating androgen production in the theca cells that surround growing follicles. Androgens are subsequently converted to estrogens by the granulosa cell enzyme aromatase, which is controlled by Follicle Stimulating Hormone (FSH). In postmenopausal women, however, estradiol is mainly derived from peripheral aromatization of circulating androgens, predominantly in the adipose tissue. In addition, in postmenopausal women 10 to 25 % of the production of androgen precursors is in the ovary, which is at least partially LH-dependent. Epidemiological evidence and animal studies indicate a carcinogenic role of estrogens in breast tissue. Here we report our studies on the impact of an LH receptor (LHR) gene variant on 1) receptor function and 2) patient and tumor characteristics in a large cohort of breast cancer patients. The insLQ polymorphism is located in the signal peptide, which enables nascent proteins during synthesis to be translocated into the Endoplasmic Reticulum (ER) membrane where protein maturation processes are carried out. Possible functional effects of the insertion were tested in in vitro transfection studies. It was found that the insLQ-LHR is more sensitive to stimulation with human Chorionic Gonadotropin (hCG) (logED50 insLQ-LHR: 0.19 vs. logED50 delLQ-LHR: 0.32 ng/ml hCG; P=0.02), and is expressed at a higher level at the plasma membrane (Bmax insLQ-LHR: 3.38±0.36 vs. Bmax delLQ-LHR: 2.41±0.26 fmol/RL; P=0.0006), indicating that the insLQ containing LHR signal peptide renders the insLQ-LHR allele more active. The frequency of the insLQ-LHR allele is 0.3. In a cohort of 751 breast cancer patients we validated the association between the insLQ-LHR variant and poor overall survival (OS) that we had reported previously. In addition, disease free survival (DFS) was shorter in insLQ carriers (HR=1.34; 95%CI (1.11-1.63); P=0.003). This negative effect of the insLQ polymorphism on DFS was stronger in premenopausal women who have an active pituitary-gonadal axis (HR=1.54 (95%CI 1.09-2.18; P=0.02). Finally the effect of androgen conversion in adipose tissue was studied by stratifying for obesity (defined as BMI > 27.5) in pre- and postmenopausal women. In both menopause groups, the HR of insLQ carriers was increased in obese women as compared to non-obese women. This effect was maximal in premenopausal obese women (HR=2.75 (95% CI (1.06-7.13); P=0.04). These results strongly suggest an involvement of LHR-regulated ovarian sex steroid hormone production followed by possible peripheral aromatization in adipose tissue. We conclude that the insLQ polymorphism negatively affects disease free survival in breast cancer patients, probably by causing an increase in estrogen exposure in female carriers of this allele, by up-regulating LHR activity.

[Proc Amer Assoc Cancer Res, Volume 46, 2005]