Quantitative Association Between HER-2/neu and Steroid Hormone Receptors in Hormone Receptor-Positive Primary Breast Cancer

• Published in: JNCI : Journal of the National Cancer Institute Vol. 95; no. 2; pp. 142 - 153
• Main Authors: Konecny, Gottfried, Pauletti, Giovanni, Pegram, Mark, Untch, Michael, Dandekar, Sugandha, Aguilar, Zuleima, Wilson, Cindy, Rong, Hong-Mei, Bauerfeind, Ingo, Felber, Margret, Wang, He-Jing, Beryt, Malgorzata, Seshadri, Ram, Hepp, Herrmann, Slamon, Dennis J.
• Format: Journal Article
• Language: English
• Published: Cary, NC Oxford University Press 15-01-2003; Oxford Publishing Limited (England)
• Subjects: Biological and medical sciences; Breast cancer; Breast Neoplasms - chemistry; Breast Neoplasms - pathology; Correlation analysis; Enzyme-Linked Immunosorbent Assay; Female; Gene Expression Regulation, Neoplastic; Genes; Genes, erbB-2 - genetics; Gynecology. Andrology. Obstetrics; Hormones; Humans; Immunoenzyme Techniques; In Situ Hybridization, Fluorescence; Mammary gland diseases; Medical sciences; Middle Aged; Neoplasm Staging; Receptor, ErbB-2 - analysis; Receptors, Estrogen - analysis; Receptors, Progesterone - analysis; Transfection; Tumor Cells, Cultured; Tumors; Up-Regulation; Human; Mammary gland diseases; Estrogen receptor; C-Onc gene; Genetics; Mammary gland; Malignant tumor; Gene expression; Progesterone receptor; Protooncogene; Biological receptor; Hormonal receptor
• ISSN: 0027-8874; 1460-2105
• DOI: 10.1093/jnci/95.2.142

Background: HER-2/neu, which encodes a receptor tyrosine kinase, is amplified and overexpressed in 20%–25% of human breast cancers. Such tumors are often resistant to hormone therapy. Despite a general inverse association between HER-2/neu amplification/overexpression and estrogen receptor (ER) and/or progesterone receptor (PR) expression, a fraction of patients are both HER-2/neu- and hormone receptor (HR)-positive. The efficacy of hormone therapy in this group is currently a matter of debate. To better understand the relationship between HER-2/neu positivity and HR expression, we analyzed HER-2/neu, ER, and PR as continuous variables in breast cancer cell lines and two cohorts of primary breast cancer patients. Methods: HER-2/neu and ER/PR expression was analyzed by enzyme-linked immunosorbent assay (ELISA) and enzyme immunoassay (EIA), respectively, in 14 human breast cancer cell lines, some of which had been transfected with the HER-2/neu gene. For the clinical study population, HER-2/neu protein levels were assessed by ELISA (cohort A, n = 665), and HER-2/neu gene copy number was determined using fluorescence in situ hybridization (cohort B, n = 894). ER/PR expression was analyzed by EIA (cohort A) or radioligand binding (cohort B). Associations between HER-2/neu and ER/PR expression were analyzed using Spearman’s rho correlation and the chi-square test, and absolute levels were compared using the Mann–Whitney U test. All statistical tests were two-sided. Results: HR-positive human breast cancer cell lines transfected with the HER-2/neu gene expressed statistically significantly lower levels of ER and PR than parental lines. In the clinical cohorts, levels of HER-2/neu overexpression and gene amplification were inversely correlated with ER/PR levels (Cohort A [n = 112]: for ER, r = –0.34, P<.001; for PR, r = –0.24, P = .010. Cohort B [n = 188]: for ER, r = –0.39, P<.001; for PR, r = –0.26, P<.001). Among patients with HR-positive tumors, HER-2/neu-positive tumors had statistically significantly lower ER/PR levels than HER-2/neu-negative ones (Cohort A: for ER, median = 25 fmol/mg [interquartile range {IQR} = 13–78] versus median = 38.5 fmol/mg [IQR = 17–99] and P = .031; for PR, median = 35 fmol/mg [IQR = 12–119] versus median = 88.5 fmol/mg [IQR = 22–236] and P<.001. Cohort B: for ER, median = 44 fmol/mg [IQR = 13–156] versus median = 92 fmol/mg [IQR = 35–235] and P<.001; for PR, median = 36 fmol/mg [IQR = 13–108] versus median = 84 fmol/mg [IQR = 24–250] and P<.001). Patients with higher levels of HER-2/neu overexpression or amplification had statistically significantly lower levels of ER/PR than patients with lower levels of HER-2/neu overexpression or amplification. Conclusion: Because absolute HR levels are strongly related to response to hormone therapy in primary and advanced breast cancer, reduced ER/PR expression may be one mechanism to explain the relative resistance of HER-2/neu-positive:HR-positive tumors to hormone therapy.