Plasminogen activator as a functional marker for estrogen dependence in human breast cancer cells

To examine whether plasminogen activator reflects the functional state of estrogen receptors in human breast cancer, the enzyme activities were determined in extracts prepared from 160 breast cancer specimens and compared on qualitative and quantitative bases with the levels of steroid receptors, such as cytoplasmic estrogen receptor (ERC), progesterone receptor (PgR) and nuclear estrogen receptor (ERN). With any receptor, plasminogen activator activity was significantly higher in receptor-positive tumors than in receptor-negative tumors. When these breast tumors were categorized into 8 groups in terms of combinations of receptor status, breast cancers which were positive for all these receptors were found to contain the highest plasminogen activator activity. Furthermore, quantitative analyses demonstrated positive correlations of the enzyme activity with either ERC content (correlation coefficient +0.37, P less than 0.001) or PgR content (correlation coefficient +0.45, P less than 0.001). These results strongly suggest that plasminogen activator can be used as an effective functional marker for hormone dependence in human breast cancer.     

Epidermal growth factor gene expression in human breast cancer biopsy samples: relationship to estrogen and progesterone receptor gene expression

This paper addresses the expression of the epidermal growth factor (EGF) gene by human breast tumor biopsy samples. Northern analysis was used to demonstrate the presence of an approximately 5-kilobase mRNA which specifically hybridized with radiolabeled human EGF complementary DNA in some human breast tumor biopsy samples. Quantitation of EGF mRNA in 60 human breast tumor biopsies using the RNase protection assay revealed that 83% of tumors contained detectable EGF mRNA. Estrogen receptor (ER) and progesterone receptor (PgR) mRNAs were similarly quantitated in the same samples. It was found that 89.4% of the ER mRNA-positive breast tumor biopsies had detectable EGF mRNA, whereas only 58.3% of the ER mRNA-negative tumors had detectable EGF mRNA. Furthermore, whereas 90.5% of the PgR mRNA-positive tumors contained EGF mRNA, only 60% of the PgR mRNA-negative tumors contained EGF mRNA. chi 2 analysis indicated that the increased percentage of tumors expressing EGF in the receptor-positive groups was statistically significant (P less than 0.01). It was also found that the mean relative level of EGF mRNA in those tumors which were ER and PgR negative [9.8 +/- 5.6 (SEM) relative units] was significantly lower than those tumors which were ER and PgR positive (40.5 +/- 6.4 relative units, P less than 0.05) or ER positive and PgR negative (68.4 +/- 19.9 relative units, P less than 0.005). These observations suggest that the EGF-expressing tumors probably arose originally from hormonally responsive cell types and that EGF expression in a large proportion of human breast tumors in vivo may also be hormonally responsive.     

Distribution of epidermal growth-factor receptors in normal and neoplastic mammary tissues

Epidermal growth factor (EGF) is considered to be mitogenic for proliferation of mammary glands in animals. The action of EGF is mediated by specific EGF receptors (EFG-R). In the present study, we investigated distribution of EGF receptors during various physiological stages of mammary glands, N-methyl-N-nitrosourea (MNU)-induced mammary tumors in rats and human breast cancer samples. EGF receptor concentrations were determined by Scatchard analyses in the membrane fraction of the tissues. Results showed increased EGF receptor levels in the structurally differentiated mammary tissues from pregnant rats; whereas lower concentrations were observed in the functionally differentiated glands from lactating rats. EGF receptors were absent in the majority of the tumors induced by MNU. The loss of EGF receptor was not observed during the first 20 days post carcinogen treatment, but appeared to be correlated with the onset of the tumor. Consistent with the literature, the majority of the steroid receptor positive human breast cancer samples were EGF receptor negative, whereas steroid receptor negative samples contained EGF receptors. These results suggest that the loss of EGF receptors in ovarian hormone dependent mammary tumors does not occur gradually during carcinogenesis but appears to be a characteristic of hormone dependent mammary tumor cells.     

Epidermal growth factor binding by breast tumor biopsies and relationship to estrogen receptor and progestin receptor levels

Epidermal growth factor (EGF) may be important in regulating the growth of some breast cancer cells in vivo because of its mitogenic action on some breast cancer cell lines in vitro. Epidermal growth factor receptors (EGF-R) were measured in a series of breast tumors to determine what percentage of breast tumors express EGF-R and whether EGF-R was independent of expression of estrogen receptor and progestin receptor. Specific binding of 125I-EGF to membranes from pooled homogenates of breast tumors reached equilibrium after 45 min at 25 degrees and remained constant. Scatchard analysis of 125I-EGF binding indicated a single class of receptors with an apparent Kd of 2 nM and a binding capacity of 28 fmol/mg of membrane protein, and the binding of 125I-EGF was not effectively competed for by insulin, fibroblast growth factor, growth hormone, or prolactin. Specific binding of 125I-EGF of 1 fmol or greater/mg of membrane protein and 15% or greater specific binding was detected in 48% of 137 unselected primary and metastatic breast tumors. The frequency distribution of EGF binding values was unimodal, with a progressive decrease in the proportion of patients with high EGF binding values. The values of EGF binding ranged from 1 to 121 fmol/mg of protein, with an arithmetic mean of 8.4 fmol/mg of protein and a geometric mean of 3.2 fmol/mg of protein. Forty-two % of 24 metastatic breast tumors were positive for EGF binding, with an arithmetic mean of 6.3 fmol/mg of protein and a geometric mean of 4.1 fmol/mg of protein. The magnitude of EGF binding in individual tumors was independent of either estrogen receptor or progestin receptor levels, although the highest quantities of EGF binding were expressed by tumors lacking steroid receptors. Approximately 20% of the tumors in the study were EGF-R-positive and ER-negative, suggesting that the growth of these tumors may be regulated predominantly by a peptide hormone (EGF) rather than a steroid hormone (estrogen). EGF binding did not correlate significantly with age of the patients. Correlation analysis between EGF binding and the percentage of malignant and nonmalignant cell types present in sections of tumor adjacent to the area assayed for EGF binding indicated that the percentage of malignant cells is an important factor in determining the amount of EGF binding in tumor homogenates. The recent discovery of transforming growth factors which interact with the EGF-receptor system suggests additional roles for EGF receptors in breast cancer.     

Receptors for epidermal growth factor and steroid hormones in human breast cancer

Epidermal growth factor (EGF) seems to play an important role in regulating the proliferation of human breast cancer. Fifty-five primary breast tumors and 7 lymph node metastases were simultaneously assayed for the presence of EGF receptors (EGFR), estrogen receptors (ER), and progesterone receptors (PR). Overall, 42% (23/55) of the tumors were EGFR positive. EGFR were more frequently present in ER- and PR-negative than in ER- and PR-positive tumors. In particular, a negative correlation between EGFR and PR (chi 2 = 6.8; p greater than 0.01) was observed. All metastatic tumors were EGFR negative, and in all cases but 1 the levels of EGFR were higher in metastatic than in primary tumors. Our results suggest the presence of a subclass of breast tumors, the growth of which is primarily regulated by EGF or EGF-like substances rather than by steroid hormones. In this group, not amenable to endocrine therapy, EGF receptors should represent a target for therapeutic intervention.     

Molecular heterogeneity of somatostatin analogue BIM-23014C receptors in human breast carcinoma cells using the chemical cross-linking assay.

Distinct proteins complexed with somatostatin and the somatostatin analogue BIM-23014C were revealed in human breast cancer cells using the cross-linking assay. One BIM-23014C-specific complex (Mr 57,000) was observed in MCF-7 (monolayer, nodule, and tumor) and T47D. Growth inhibition of MCF-7 tumor xenografts by BIM-23014C was dose related in the 6-day subrenal capsule assay. Three complexes (Mr 27,000, 42,000, and 57,000) were detected in MDA-MB-231, and no complex was visible in HBL-100. No correlation was found between receptors for BIM-23014C and epidermal growth factor in these lines. Twenty-seven of 30 human breast tumors (90%) had at least one BIM-23014C receptor. Sixteen had three complexes (Mr 27,000, 42,000, and 57,000). Six had the two complexes (Mr 27,000 and 57,000), two had Mr 42,000 and 57,000 complexes, two had just the Mr 27,000 complex, and one had just the Mr 42,000 complex. The presence of the three BIM-23014C receptors was positively correlated (P less than 0.05) to the low amount of sex steroid receptors (less than 20 fmol/mg) [seven of eight (estrogen receptor negative, progesterone receptor negative) versus four of 14 (estrogen receptor positive, progesterone receptor positive)]. Another positive correlation was established between the absence of progesterone receptors and the presence of these three complexes [12 of 16 (progesterone receptor negative) versus four of 14 (progesterone receptor positive)]. This high percentage of BIM-23014C receptor-positive biopsies and its inhibitory activity would support its clinical potential for the treatment of breast cancer.     

Immunocytochemical determination of epidermal growth factor receptor with monoclonal EGFR1 antibody in primary breast cancer patients

Epidermal growth factor (EGF) has been shown to be important in regulating the growth of breast cancer cells in vivo because of its mitogenic action on some breast cancer cell lines in vitro. Immunocytochemical analysis of EGF receptor (EGFr) was carried out on frozen sections in 134 primary breast cancer patients. Overall 68 of 134 (51%) of the tumors were EGFr positive. There was no correlation between EGFr positivity and menopausal status. Regarding the histopathological features, no significant correlations were observed between EGFr expression and tumor size, grading and lymph nodes status. Estrogen (ER) and progesterone (PgR) receptors were detected by an immunocytochemical assay and an equal distribution of EGFr was found regarding steroid hormonal receptors expression. Finally, there was only a positive trend between the proliferative activity of the tumors, as measured by Ki-67 antibody, and the amount of EGFr. Our results suggest the presence of a subclass of breast tumors, characterized by the absence of ER and/or PgR and the presence of EGFr, whose growth appears to be mediated by autocrine growth factors rather than by steroid hormones. The overall picture is that of an independent relationship between EGFr expression and the known prognostic factors in breast cancer.     

Value of epidermal growth factor receptor, HER2, p53, and steroid receptors in predicting the efficacy of tamoxifen in high-risk postmenopausal breast cancer patients.

PURPOSE: Few studies have examined the possible importance of biologic prognostic factors in breast cancer connected with differentiation and growth in predicting response to a specific adjuvant treatment. HER2, epidermal growth factor receptor (EGFR), and p53 have all been suggested as possible markers of tamoxifen resistance. The aim of this study was to investigate interactions between adjuvant treatment with tamoxifen and the content of EGFR, HER2, and p53 in steroid receptor-positive patients. PATIENTS AND METHODS: A total of 1,716 high-risk postmenopausal breast cancer patients were randomly assigned to treatment with tamoxifen (868 women) or to observation (848 women) in a prospective trial (Danish Breast Cancer Cooperative Group's 77c protocol). The content of the steroid receptors and expression of p53, EGFR, and HER2 were determined by immunohistochemical analysis of paraffin-embedded tissue. The length of follow-up was 10 years. The end point for this analysis was disease-free survival. RESULTS: Multivariate analysis demonstrated no increased risk of recurrence after treatment with tamoxifen for HER2-, EGFR-, and p53-positive, high-risk, steroid receptor-positive patients. Patients with steroid receptor-positive tumors and positive immunohistochemical staining for HER2, EGFR or p53 benefited from treatment with tamoxifen for 1 year, although the latter variable contained independent prognostic information by itself. CONCLUSION: With the statistical power of the present randomized study, we did not find support for the hypothesis that HER2/EGFR or p53 status predicts benefit from tamoxifen treatment in estrogen receptor-positive patients with early-stage breast cancer. Thus, neither HER2, EGFR, nor p53 overexpression/accumulation should be used as a contraindication for giving tamoxifen.     

Distribution, frequency, and quantitative analysis of estrogen, progesterone, androgen, and glucocorticoid receptors in human breast cancer.

The distribution and frequency of steroid hormone receptors are described 329 patients with breast cancer. The distribution of each of the steroid hormone receptors is unimodal with a progressive increase in the proportion of patients positive at lower receptor values. Receptor values expressed as fmol/mg cytoplasmic protein are well correlated with values expressed as fmol/mg breast tumor. Estrogen receptor was positive in 53% of the patients; progesterone receptor was positive in 38% of the patients; glucocorticoid receptor was positive in 52% of the patients; and androgen receptor was positive in 31% of the patients. The type of tissue assayed did not affect steroid hormone receptor positivity. For primary tumors, there was no correlation between steroid hormone receptor positivity and location of the tumor in the breast, size of the tumor, or extent of the disease. Each of the steroid hormone receptors was positively associated with each of the other steroid hormone receptors. Estrogen receptor was correlated with menopausal status and axillary nodal status, but these correlations did not exist for the other steroid hormone receptors. Estrogen receptor was not correlated with age after adjustment for menopausal status. The other steroid hormone receptors were not correlated with age.     

Epidermal growth factor binding and protein kinase C activities in human breast cancer cell lines: possible quantitative relationship

Quantitative polyacrylamide gel electrophoresis analysis of Ca2+, phospholipid-dependent protein kinase (PKC) of human mammary tumor cell lines (MCF-7, ZR-75, T-47-D, MDA-MB-231, BT-20, and HBL-100) revealed that 80% of the total cellular PKC resided in the cytosol. The tumor cells with no detectable levels of estrogen receptors (MDA-MB-231, HBL-100, and BT-20 cells) exhibited significantly larger (P less than 0.001) cytosolic PKC activities than those cells that contained estrogen receptors (MCF-7, T-47-D, and ZR-75 cells). In addition, in estrogen receptor-negative cell lines, relatively high levels of specific low-affinity (apparent Kd = 700 pM) epidermal growth factor (EGF) binding activities were found as compared with estrogen receptor-positive cells with significantly (P less than 0.001) lower levels of specific high-affinity (apparent Kd = 90 pM) EGT binding. A significant positive correlation (P less than 0.01) was observed between the number of EGF receptor (Rs = 0.50) and/or the EGF receptor dissociation constants (Rs = 0.78) with the cytosolic PKC activity levels. These data indicate that, in human breast cancer cells, a positive relationship may exist between PKC activity, estrogen, and EGF receptors.     

Insulin-like growth factor-1 receptors and insulin-like growth factor-1-like activity in human primary breast cancer

In the current study the authors have investigated whether human primary breast cancer specimens contain insulin-like growth factor-1 (IGF-1) receptors (IGF-1-R) or IGF-1-like activities. Simultaneously, epidermal growth factor (EGF) receptors (EGF-R) and cytosolic estrogen receptor (ER), progesterone receptor (PR), and EGF-like activity were determined. All tumors assayed contained a single class of specific iodine 125 (125I)-IGF-1 binding sites (Kd: median 106, range 48-755 pM; n = 32) with limited capacity (Bmax: median 147, range 19-11,900 fmol/mg membrane protein). Seventy percent of 44 tumors (50% ER+, PR+), displayed specific 125I-EGF binding with a wide range of values (median 13, range 2-215 fmol/mg protein, n = 31). A positive relationship was apparent between the amount of IGF-1-R with ER and PR (Spearman; 2P less than 0.02 and 2P less than 0.01, respectively; n = 32), whereas for EGF-R a negative relationship was observed (for both 2P less than 0.01; n = 44). All tumors contained endogeneous IGF-1-like and EGF-like activities as measured by radioreceptor assay on acid-ethanol extracted cytosols (median 15, range 3-131 ng/mg protein, n = 78 for IGF-1; and median 86, range 26-517 ng/mg protein, n = 142 for EGF). Tumor contents of IGF-1-like and EGF-like activities showed a negative relationship with ER (2P less than 0.1 for IGF-1, n = 78; and 2P less than 0.001 for EGF, n = 142), and with PR (2P less than 0.05, n = 78; and 2P less than 0.001, n = 142). No relationship was observed between the tumor contents of IGF-1-like and EGF-like activities. In conclusion, these data support the view that IGF-1 and EGF can act as autocrine or paracrine growth factors in human breast cancer.     

125I]17-alpha-iodovinyl 11-beta-methoxyestradiol interaction in vivo with estrogen receptors in hormone-independent MCF-7 human breast cancer transfected with the v-rasH oncogene

[125I]17-alpha-Iodovinyl 11-beta-methoxyestradiol [( 125I]MIVE2) has been evaluated as a potential radiotracer for the diagnostic imaging of estrogen receptor (ER)-positive human breast cancer. In vivo distribution experiments with athymic ovariectomized nude mice bearing human breast tumors revealed an apparent correlation between uptake of 125I-labeled compound and estrogen receptor concentration in the tumors. At 4 h after i.v. injection of [125I]MIVE2, HS578T (ER negative), ZR75-B (intermediate ER), and MCF-7ras (high ER) tumors accumulated 0.320 +/- 0.186, 0.679 +/- 0.467, and 2.6163 +/- 1.0121% injected dose/g, respectively. With coinjection of unlabeled 17-beta-estradiol, levels of radioactivity in MCF-7ras tumors were decreased to 0.4859 +/- 0.1424% injected dose/g, indicating a receptor-mediated process. Peak activity of radioligand in MCF-7ras tumors and uteri was observed at 2 h and was retained for the 8-h time course. Blood and nontarget tissue, such as muscle, revealed a rapid clearance of 125I-labeled compound by 8 h. Eight hours after injection, uterus and tumor-to-blood ratios were calculated to be 225 and 21, respectively. Also, MCF-7ras tumors were shown to accumulate 6.5-fold more radioactivity than muscle. These data suggest that [125I]MIVE2 has the capability of interacting specifically and with high affinity with estrogen receptors in human breast tumors in nude mice and may possibly be used for imaging receptor-positive tumors in breast cancer patients with very low serum estrogen levels. Selective uptake of compound in MCF-7ras tumors emphasizes the usefulness of an estrogen receptor-positive tumor model which has a unique ability to grow in a host system without circulating estrogens.     

Epidermal growth factor receptor status and S-phase fractions in gastric carcinoma

The correlation with epidermal growth factor (EGF) receptor expression and clinicopathologic findings were studied in 242 gastric carcinomas. They were stained for EGF receptor by means of an immunohistochemical technique using a monoclonal antibody against the receptor. S-Phase fractions were measured by in vivo bromodeoxyuridine (BrdU) labeling and indirect immunohistochemical staining using anti-BrdU monoclonal antibody. In normal gastric epithelium, EGF receptor immunoreactivity could not be found. EGF receptor was found in 76 (31.4%) of 242 gastric carcinomas. Diffusely infiltrating types of carcinomas were more likely than localized tumors to be EGF receptor-positive. In addition, EGF receptor-positive tumors had significantly higher values of BrdU labeling indices than EGF receptor-negative tumors. The patients with EGF receptor-positive carcinomas also had a poorer prognosis than did negative cases. These results suggested that EGF receptor-positive tumors may have higher proliferative activity and local extension may progress more rapidly, and also seem to show that EGF receptor status may possibly be a useful prognostic marker for gastric carcinomas.     

Distribution of estrogen and progesterone receptors in primary tumor and lymph nodes in individual patients with breast cancer

Primary breast cancer tissue and lymph nodes were obtained from 48 patients. Estrogen receptors (ER) and progesterone receptors (PgR) were determined by a dextran-coated charcoal assay. ER were present in 72.9% of the primary tumors and in 62.4% of the malignant lymph nodes, whereas PgR were present in 73.0% and 50.0% of the cases, respectively. The primary tumor and the corresponding malignant lymph nodes showed an identical ER and PgR status, i.e., both tumor sites were receptor positive or both receptor negative in 89.6% and 77.1%, respectively. However, 10.4% of the patients had ER-positive tumors but ER-negative lymph nodes and 22.9% had PgR-positive primaries with PgR-negative lymph nodes. No receptor-positive lymph nodes showed a combination with receptor-negative primary tumor. This preliminary data shows that receptor-positive malignant lymph nodes mostly display the same receptor status as the corresponding primary tumor, whereas receptor-negative lymph nodes may have a receptor-positive primary tumor.     

Steroid Hormone Receptor Positive Breast Cancer Patient-Derived Xenografts

The vast majority of breast cancers are positive for estrogen receptor (ER) and depend on estrogens for growth. These tumors are treated with a variety of ER-targeted endocrine therapies, although eventual resistance remains a major clinical problem. Other steroid hormone receptors such as progesterone receptor (PR) and androgen receptor (AR) are emerging as additional prospective targets in breast cancer. The fundamental mechanism of action of these steroid receptors in gene regulation has been defined mainly by several breast cancer cell lines that were established in the late 1970s. More recently, breast cancer patient-derived xenografts (PDX) have been developed by multiple groups at institutions in several countries. These new models capture the large degree of heterogeneity between patients and within tumors and promise to advance our understanding of steroid hormone receptor positive breast cancer and endocrine resistance. Unfortunately, steroid hormone receptor positive breast cancers are much more difficult than their receptor negative counterparts to establish into sustainable PDX. Herein we discuss the derivation of steroid hormone receptor positive breast cancer PDX, several pitfalls in their genesis, and their utility in preclinical and translational steroid hormone receptor research.     

Detection of somatostatin receptors in surgical and percutaneous needle biopsy samples of carcinoids and islet cell carcinomas

Somatostatin (SS) receptor status was investigated in the tumor tissues from 62 patients with carcinoid tumors and 15 patients with islet cell carcinomas using receptor autoradiography techniques with two different iodinated somatostatin analogues as radioligands, a [Leu8, DTrp22, Tyr25]somatostatin-28 and a somatostatin octapeptide, Tyr3-octreotide. The carcinoid tumors were either primaries (n = 32) or metastases (n = 43), sampled as surgical specimens or as small needle liver biopsies. Fifty-four of 62 carcinoid patients had SS receptor-positive tumors (87%). All 15 islet cell carcinoma patients had positive tumors (4 primaries, 11 metastases), i.e., 3 vipomas, 3 insulinomas, 2 glucagonomas, 1 gastrinoma, 2 polyfunctional tumors, and 4 nonfunctioning tumors. Saturation and competition experiments on tissue sections revealed saturable, high affinity binding sites pharmacologically specific for bioactive SS analogues. In a majority of the tumors, the receptors were densely distributed and were always homogeneously found in the whole tumor. All except two tumors were labeled with both radioligands. Multiple liver metastases (n = 16) from three different patients were all shown to contain a comparable amount of receptors. SS receptors could be demonstrated even in very small tissue samples of liver metastases obtained by percutaneous liver biopsies (mean weight, 6.8 mg). The majority of the eight SS receptor-negative carcinoids were mainly bronchial carcinoids (n = 5), usually poorly differentiated. On the contrary, SS receptor-positive cases were never found to be anaplastic. All tumors except one from patients pretreated with octreotide (3 days to 3.8 years) were SS receptor positive. In the majority of carcinoids or islet cell carcinomas, the SS receptor status correlated with the in vivo biochemical response (hormone inhibition) to octreotide. These data demonstrate (a) the high prevalence of SS receptors in the primary tumors of both carcinoids and islet cell carcinomas, (b) their presence in metastases as well, (c) their continuous expression even during long term octreotide therapy, (d) the possibility of measuring SS receptors in percutaneous needle liver biopsies, and (e) the evidence of their functionality. This study therefore suggests that tumoral SS receptors may be the likely molecular basis for octreotide action and may be an important parameter for predicting the therapeutic efficacy of SS analogues in carcinoids and islet cell carcinomas.     

Binding characteristics and biological activity of 17 alpha-[125I]iodovinyl-11 beta-methoxyestradiol, an estrogen receptor-binding radiopharmaceutical, in human breast cancer cells (MCF-7)

17 alpha-[125I]Iodovinyl-11 beta-methoxyestradiol ([125I]MIVE2), a gamma-emitting analogue of estradiol, previously shown to bind to rat uterine estradiol receptor, was studied to determine the binding characteristics and biological activity in human breast cancer cells. In vitro determination of receptor binding by dextran-coated charcoal assays indicates that [125I]-MIVE2 binds specifically and with a high affinity to cytosolic estrogen receptors in the human breast cancer cell line, MCF-7. [3H]Estradiol binds to the receptor with approximately four times the affinity of [125I]-MIVE2 (Kd = 2.55 X 10(-9) M for [125I]MIVE2; Kd = 6.4 X 10(-10) M for [3H]estradiol). Unlabeled MIVE2 produces estrogenic effects similar to those of estradiol such as progesterone receptor induction and increases in thymidine incorporation in MCF-7 cells in culture. Cytosolic progesterone receptor levels were elevated 2.8-fold over control levels by 6 X 10(-9) M MIVE2. Stimulation of thymidine incorporation (approximately 300% above control levels) was observed after exposure to 1 X 10(-9) M MIVE2. Preliminary data show receptor-mediated uptake by the uterus in biodistribution studies in athymic nude mice given injections of [125I] MIVE2 (32-34 microCi). At 4 h, uterus:blood ratios are 20.5 and target tissue:nontarget tissue ratios are 12.9. In light of the fact that this compound can be prepared with a high specific activity, [125I]MIVE2 may have potential as a radiotracer for imaging estrogen receptor-positive breast tumors or metastatic lesions in human breast cancer patients.     

Estimation of epidermal growth factor receptor in 177 breast cancers: Correlation with prognostic factors

Summary Steroid receptors (ER, PR) and EGF-receptor were determined on 177 loco-regional primary breast cancers. Binding assay for EGF receptor was performed using a single saturating concentration of¹²⁵I-EGF incubated with membranes in the presence or absence of unlabeled EGF. With threshold values of 5 fmol/mg and 10 fmol/mg for EGF-R and steroid receptors respectively, we noted an inverse relationship between the expression of EGF-R, and ER and PR. EGF-R expression is decreased with tumor differentiation.     

Steroid hormone receptors in human colon cancers.

Tumors from patients with primary colon cancer were studied for the presence of steroid hormone receptors for estrogen (E2), progesterone (Prog), dihydrotestosterone (DHT) and glucocorticoid. Ten of 33 (30%) tumors contained high affinity E2 receptors. Four were males and six females with positive assays predominantly from the left colon. Twenty-three of these tumors were also assayed for DHT and Prog and six (26%) contained all three receptors. An additional twelve tumors had at least one receptor, so that 70% of the tumors studied contained one or more receptors. Five of 22 (23%) samples were positive for glucocorticoid receptors. Common etiological factors associated with colon and breast cancer were briefly discussed. These factors, along with the presence of hormone receptors in primary colon malignancies suggest that some large bowel cancers may be endocrine-dependent.     

Measurement of occupied and non-occupied epidermal growth factor receptor sites in 216 human breast cancer biopsies

Summary The epidermal growth factor (EGF) is one of several growth factors involved in normal breast epithelial development and tumor proliferation. EGF and EGF-like peptide TGF bind and activate the same membrane receptor protein. This receptor (EGF-R) has been recently studied in breast tumor biopsies and its detectability reported as a prognostic indicator.However, normal and tumor tissue themselves produce EGF and related peptides in variable amount. This suggests that the standard measurement of EGF-R by binding assay should reflect only the number of non-occupied receptor sites. Based on this observation, the presence of occupied sites (EGF-R2) has been assessed in 216 human mammary tumor biopsies simultaneously with the direct measurement of non occupied EGF receptor sites (EGF-R1) and the results compared to estrogen and progesterone receptor status (ER, PGR). EGF-R1 and EGF-R2 were evaluated by 2 separate (¹²⁵I) EGF binding assays performed on 2 aliquots of tumor crude membrane fraction, the first one directly, the other after dissociation of the endogenously bound ligand. The validity of the method has been assessed on membrane fractions prepared from human placenta. It is shown that the dissociation does not modify the binding dissociation constant. ER and PGR were measured by the dextran coated charcoal method. Results > 10 fmol/mg of membrane or cytosol protein were considered as positive.It is found that EGF-R1 and EGF-R2 are detectable in 54 and 90% of the cases, indicating that EGF-R is masked by endogenous ligand in 36% of the tumors. The mean incidence of EGF-R1 positivity is significantly higher in ER-(66%) than in ER+ tumors (49%) while EGF-R2 is detectable in 90% of tumors regardless of ER status. These data suggest that EGF-like peptides are locally produced in the majority of breast tumors. The positive relation between the presence of ER and the total occupancy of EGF-R sites could be in favor of their control by estrogens.