Correlation of body mass index and menopausal status with the intratumoral estrogen system in invasive breast cancer

Objective: Obesity is associated with an increased breast cancer risk in postmenopausal women. One reason for this association is the elevated non-glandular aromatase activity resulting in higher estradiol serum levels. We tested the hypothesis that obesity and menopausal status might also be associated with changes in the intratumoral estrogen system of breast cancer tissue.

Design: We studied expression of different genes in correlation to menopausal status, BMI and histopathological parameters. Breast cancer tissue and fasting serum were collected from 26 female patients. After microdissection of the frozen samples, RNA was isolated and expression of estrogen receptor (ER)alpha, ER beta1, ER beta2, ER beta5, CYP19 aromatase and steroid sulfatase was measured on mRNA level by means of real time RT-PCR. Fasting estradiol serum levels were analysed by ELISA.

Results: A significant inverse correlation between ER alpha and ERß2 expression was identified in invasive breast cancer tissue irrespective of BMI or menopausal status. Postmenopausal women older than 70 years exhibited a significantly higher expression both of steroid sulfatase and ER alpha than premenopausal women younger than 50 years. With regard to BMI, we did not observe any significant correlation with intratumoral gene expression, but we identified a significant positive correlation between BMI and lymphovascular/vascular invasion status.

Conclusion: In conclusion, we report an association between menopausal status, but not BMI, with the intratumoral expression of steroid sulfatase and ER alpha. Our observation that BMI was associated with invasiveness supports the hypothesis that metabolic factors are able to affect essential features of breast cancer.