Tumor Estrogen Receptor Levels Research Articles

Abstract P4-04-06: CD146 positive and negative stroma direct breast tumor estrogen receptor levels, therapeutic response and metastatic potential

Abstract Background: Cellular heterogeneity within all breast cancer subtypes remains a major cause of treatment failure and development of metastatic disease. Currently, both preclinical studies and drug development efforts focus almost exclusively on the epithelial component of breast cancers. Despite strong preclinical data novel therapies often fail in clinical testing. We propose that this failure is, in part, due to taking tumor cells out of their context and using pre-clinical models that fail to capture the complexity of human disease. We hypothesize that tumors hijack normal components of the tissue microenvironment and use it to their advantage. Here we demonstrate that similar to the normal hematopoetic niche, two major subtypes of breast cancer stroma can be defined by CD146 expression. We further show that the ratio of the stromal subtypes alters the response to therapy and increases the metastatic potential of breast cancer cells (BCC). Results: Tumor associated stroma, from all breast cancer subtypes, contains a mixture of CD146+ and CD146- fibroblasts. We isolated and derived pure human CD146+ and CD146- clonal lines. Both subtypes expressed markers of activated fibroblasts and clustered by gene expression profiling with normal stromal cell lines HS27A (CD146+) or HS5 (CD146-) according to CD146 expression. Although both stromal subtypes were derived from tumor associated tissue, CD146+ breast cancer stroma clustered with normal breast associated stroma and correlated with good clinical outcome (Finak et. al. Nature Med 2008). CD146- stroma clustered with breast cancer associated stroma and predicted worse outcome. Using cell line and patient-derived xenograft models of estrogen receptor (ER) positive breast cancer, we demonstrated that CD146+ compared to CD146- stroma supported significantly higher ER expression in BCCs. BCC co-cultured with CD146+ stroma responded more robustly to estrogen treatment and anti-endocrine therapy with tamoxifen. Next we used expression profiling data to predict stromal influence on treatment response. CD146+ stroma expressed 3-fold more TGFβ than CD146- stroma. Inhibiting TGFβ decreased proliferation 2-fold in BCCs grown in media conditioned by CD146+ stroma, but not by CD146- stroma. Conversely, HBEGF expression was 3-fold higher in CD146- stroma compared to CD146+ stroma. Inhibiting EGFR decreased proliferation 1.5-fold in BCCs grown in conditioned by CD146- stroma, but not by CD146+ stroma. In addition, intracardiac injection of stroma resulted in distant metastases in our primary orthotopic PDX model of breast cancer. Lastly we confirmed our preclinical observation using a small set of clinical samples. Patients with high CD146+ to CD146- stromal ratio had better clinical outcomes than patients with high CD146- to CD146+ stromal ratio. Conclusion: We conclude that stromal subtypes defined by CD146 expression direct the heterogeneity of ER expression, response to therapy and the metastatic potential of breast cancer cells. Citation Format: Heather M Brechbuhl, Jessica J Finlay-Schultz, Tomomi M Yamamoto, Austin E Gillen, Anthony Elias, Carol A Sartorius, Peter Kabos. CD146 positive and negative stroma direct breast tumor estrogen receptor levels, therapeutic response and metastatic potential [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P4-04-06.

Estrogen receptors in breast cancer. Association with epidemiologic risk factors.

This study examined the factors influencing estrogen receptor protein levels in a population-based group of 168 incident cases of breast cancer in Olmsted County, Minnesota. The medical histories of women with histologically confirmed breast cancer and measured estrogen receptor levels in the period from November 1977 through December 1982 were reviewed. Statistically significant positive univariate associations were found between tumor estrogen receptor protein level and age, postmenopausal status, nulliparity, late age at first birth, cholelithiasis and educational level. No association was found between tumor estrogen receptor level and other breast cancer risk factors. After adjustment for age, there was no association between the above factors and estrogen receptor protein level. On multivariate analysis, age remained a statistically significant predictor of a higher estrogen receptor protein level. These findings in a population-based group of women with breast cancer are similar to previous reports of hospital-based breast cancer patients.

Obesity, non-protein-bound estradiol levels, and distribution of estradiol in the sera of breast cancer patients.

This study attempted to determine the relationship of nutritional status, menopausal status, presence of breast cancer, stage of disease, and tumor estrogen receptor levels to percent non-protein-bound estradiol (%NPBE) and percent distribution of estradiol on sex hormone-binding globulin (SHBG) and albumin in breast cancer patients and control patients. Normal-weight controls had significantly lower %NPBE compared with overweight controls and normal-weight and overweight breast cancer patients. There was a significant shift in the percent distribution of estradiol from SHBG to albumin in breast cancer patients, independent of body weight. Elevated %NPBE and abnormal percent estradiol distribution on albumin persisted after mastectomy and were unrelated to menopausal status, presence and stage of disease, and tumor estrogen receptor levels. These results show that breast cancer patients have increased exposure to unbound circulating estradiol and an increased percentage of estradiol bound to albumin, which may influence the availability of estradiol, considering its low binding affinity to albumin. Because these abnormalities persist after mastectomy, the current results may be important in developing dietary intervention protocols that correct %NPBE and abnormal estradiol distribution on binding proteins.

Effects of reserpine administration on rat mammary tumors and uterine disease induced by N-Nitrosomethylurea

Reserpine 50 μg 100 g body weight administered s.c. to female rats on the day before, of and after each of three N-nitrosomethylurea (NMU) i.v. injections, influenced a number of experimental observations. The total doses of NMU given to the various treatment groups were 15, 12, 9, 6, 3 and 1.5 mg 100 g body weight. Tumor incidence ranged from approximately 100 to 0% in the control and reserpine-treated groups, depending on the dose of carcinogen given. Concurrent reserpine administration with the NMU decreased the number of tumors per rat; at 15 and 12 mg 100 g body weight NMU doses the values were only 58 and 55% of the respective controls. Reserpine treatment at these 2 NMU doses also increased the percentage of well-differentiated mammary tumors compared with corresponding controls. Tumor estrogen receptor levels in controls ranged from 71 to 78 fmol/mg protein and in the reserpine-treated groups from 96 to 105 fmol/mg protein; significant elevations were present in the rats given reserpine and the 2 highest doses of NMU. Tumor progesterone and prolactin receptor levels were similar in control and reserpine-treated groups. The estrous cycle of the controls was frequently arrested at estrus and 21 57 (37%) had a fluid-distended uterus and thickened uterine walls; only 2 52 (4%) of reserpine-treated rats had hydrometria and none exhibited cycle arrest at estrus. The effect of reserpine on mammary tumors was also studied when given after initial exposure to the carcinogen. NMU was administered to 65 rats in 3 doses of 5 mg 100 g body weight by i.v. injections 4 weeks apart. Equal numbers of animals comprised 1 control and 2 reserpine treatment groups. Reserpine was given at a daily dose of 20 μg 100 g body weight commencing 67 days after the first NMU dose (chronic regimen) or by the same schedule preceded by 50 μg 100 g doses given on the day before, with and on the day after the second and third NMU injections (acute/chronic regimen). A fourth group of rats received chronic reserpine treatment but no NMU. All 3 NMU-exposed groups had a 100% tumor incidence; none developed in the reserpine-treated controls. The acute/chronic reserpine treatment increased the rate of tumor development but neither drug schedule altered the number of tumors per rat or the mean final total tumor areas. Reserpine administration was associated with greater degrees of anaplasia in mammary tumors induced by NMU ( P < 0.01). The mean tumor estrogen receptor content was significantly higher in the acute/chronic reserpine-treated group ( P < 0.0002) and the chronic reserpine-treated animals ( P < 0.008) compared with controls. Tumor prolactin receptor content was unaffected by the drug. Peroxidase activity was higher in mammary tumors and lower in uteri from reserpine-treated rats compared with tumor-bearing controls. Also, there was a strong correlation ( r = 0.82) between the mammary tumor estrogen receptor and tumor peroxidase activity for rats treated with the acute/chronic reserpine regimen.

Estrogen receptor-like macromolecule in MtTW15 rat pituitary tumors: Effects of antiestrogens

To understand how estradiol-17β (E2) influences MtTW15 rat pituitary tumor function, we have evaluated the cytosolic E2 binding properties of tumors derived from control and steroid treated host animals. Specific E2 binding (approximately 3 pmoles/g tumor) was observed in all groups and was steroid responsive. The E2 binding macromolecule migrated to 7S following sucrose density gradient sedimentation and was specific for estrogenic steroids. Saturation analysis of E2 binding revealed a high affinity interaction ( K d = 5.5 ± 0.5 × 10 −10 M). Furthermore, E2 binding was temperature-sensitive and degraded by trypsin. Thus, the MtTW15 tumor contains an estrogen receptor. Accordingly, the effects of 4 antiestrogenic drugs on tumor estrogen-receptor levels, tumor growth and hormone production were evaluated. In general, these drugs reduced cytosolic estrogen receptor levels, promoted tumor growth and increased tumor growth-hormone production. It is suggested that these compounds can exert both estrogen agonist and antagonist properties in MtTW15 tumors.

Effects of estradiol and prolactin on steroid receptor levels in 7,12-dimethylbenz(a)anthracene-induced mammary tumors and uterus in the rat

In order to eliminate changes of pituitary hormone secretion secondary to treatment and be able to assess the direct effect of 17β-estradiol and prolactin at the level of hormone-dependent mammary tumors induced in the rat by 7,12-dimethylbenz(a)anthracene (DMBA), the effects of the two hormones on steroid receptor levels were investigated in hypophysectomized-ovariectomized animals. Treatment with prolactin alone led to tumor estrogen receptor levels higher than those found after estrogen administration. When the level of progesterone receptors was measured as parameter of estrogen action, it was found that combined treatment with prolactin and 17β-estradiol led to levels much higher than those found after individual hormone treatment. Tissue specificity of this interaction between prolactin and 17β-estradiol is indicated by the absence of effect of prolactin on the estrogen-induced stimulation of the progesterone receptor in uterine tissue. These data demonstrate the direct stimulatory effect of prolactin on estrogen receptor levels in DMBA-induced mammary carcinoma and indicate the central role of this pituitary hormone as modulator of estrogen action and growth of DMBA-induced mammary tumors.