Abstract P6-07-04: Gene expression profiles of angiogenesis related cytokines and cognate receptors predict breast cancer progression and survival

Background: Angiogenesis plays a critical role in breast cancer development, invasion and metastasis, and VEGF, TGFß1, and IL10 genes and their cognate receptors are implicated in cancer behavior, mediating membrane and microenvironment remodeling. Our goal is to assess relationships of expression of these genes in LCM-procured carcinoma cells from primary breast cancers with clinical outcomes to predict risk of recurrence.

Methods: Gene expression determined by microarray and qPCR, ER/PR quantified by radio-ligand binding or EIA, features of primary breast cancers and clinical outcomes were performed by univariable and multivariable Cox regressions, Kaplan Meier plots and LASSO with R software v3.2.5. Microarray analyses of ˜22,000 genes utilized RNA isolated, purified and amplified from LCM-procured carcinoma cells. Gene expression was validated by qPCR while molecular signatures were externally validated with SurvExpress (Aguirre-Gamboa et al. PLoS One e74250, 2013).

Results: Univariable Cox regression of microarray results of cytokines and cognate receptor genes revealed IL10 expression was significant for prediction of Progression Free (PFS) or Overall Survival (OS) using an adjusted p-value of ≥ 0.30 (discovery cut-off). Without regard to ER/PR status, Kaplan Meier plots confirmed IL10 or TGFß1 expression was significant for predicting PFS and OS. Using ER+ cancers, IL10 or VEGF expression was related to PFS while only IL10R was related to OS of ER- cancers using univariable Cox regression. Validation by qPCR using tissue curls disclosed independent expression of either TGFß1 or VEGF predicted PFS and OS while that of TGFß1Rwas only related to PFS. IL10R expression only predicted OS of breast cancer patients. Violin plots of qPCR results indicated elevated expression of each of these six genes in ER+ primaries without regard to outcome. Multivariable Cox regression analyses of expression levels of cytokine-receptor gene pairs revealed that IL10-IL10R co-expression was highly significant for predicting OS. Strongly supportive, backwards selection (R software v3.2.5) utilizing microarray expression levels derived a significant model (molecular signature) consisting of IL10, IL10R and VEGFR genes for predicting OS. External validation of this 3-gene subset was accomplished utilizing patient data collected on SurvExpress. A second clinically relevant signature predicting OS in PR+ breast cancers was detected when TGFß1R expression was included with these 3 genes. Finally, backwards selection of qPCR data derived a significant 3-gene model composed of IL10R, TGFß1 and VEGF for predicting PFS that was undeniably validated by SurvExpress.

Conclusions: Using gene expression results derived from microarray analyses of LCM-procured breast carcinoma cells of primary lesions and validated by qPCR, subsets of angiogenesis related genes were identified that predict a patient's risk of recurrence and overall survival. Expression of candidate genes appears to be related to either/both ER or PR protein status of the primary lesion. Collectively, results suggest that expression of certain angiogenesis related genes may serve as biomarkers for assessing prognosis of breast carcinomas thus impacting clinical management.

Citation Format: Wittliff JL, Sereff SB, Smolenkova IA, Hameed ZR, Andres SA. Gene expression profiles of angiogenesis related cytokines and cognate receptors predict breast cancer progression and survival [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-07-04.

Abstract P1-01-12: Expression of autophagy related genes impacts clinical outcomes of human breast carcinoma and is associated with estrogen and progestin receptor status

The dual role of autophagy in breast cancer initiation, progression and responsiveness to various therapies is the focus of extensive studies. Our goal is to assess the relationship of expression of certain autophagy related genes in primary breast carcinomas to predict risk of recurrence. Our hypothesis includes the caveat that unique gene expression subsets will be deciphered by utilizing Laser Capture Microdissected breast carcinoma cells from tissue biopsies containing many cell types.

Methods: Comprehensive analyses of de-identified biomarker results, characteristics of 247 breast carcinoma specimens and clinical outcomes were performed by univariable Cox regressions, Kaplan Meier plots and LASSO with R software version 3.2.5. Microarray analyses were performed on RNA isolated from LCM-procured carcinoma cells to identify gene signatures associated with breast cancer behavior.

Results: Expression levels of 22 autophagy related genes analyzed by univariable Cox regression revealed that RB1CC1, KEAP1, ATG7, RUBCN, NOD2, HMOX1, BECN1, PIK3R4 were significant for predicting Progression Free Survival (PFS) at the discovery level of the adjusted p-value < 0.3. Of these, RB1CC1, KEAP1, & ATG7 were significant for Overall Survival (OS) without regard to ER/PR status. Using Kaplan Meier analyses, expression levels of each of 10 candidate genes predicted PFS of which expression of 6 of these genes also predicted OS using a median split cutoff without regard to ER/PR status. Applying LASSO computations without regard to ER/PR status of the primary breast cancer, a clinically relevant gene expression profile consisting of ATG7, BCL2, HMOX1, KEAP1, NOD2, PTEN, RB1CC1, and ULK4 predicted PFS. Collectively, expression of these 8 genes with TP53 and RUBCN predicted OS without regard to ER/PR status. Violin plots of relative gene expression of each of the 22 candidate genes known to be associated with autophagy pathways revealed that ATG7, ATG12, BCL2 and BECN1 were elevated in ER+ lesions while BCL2 and BECN1 were also elevated in PR+ breast carcinomas. Expression levels of 16 of the 22 autophagy related genes examined by univariable Cox regression were related to either ER or PR status of the primary lesion and predicted either PFS or OS. Refinement of clinically relevant gene subsets was accomplished by LASSO calculations in which either the ER or PR protein status of the primary breast carcinoma was considered. Of the genes in the molecular signatures derived, expression levels in breast carcinomas separated by either ER or PR status of the lesion were tested by Kaplan Meier analyses to assess relationships to PFS and OS.

Conclusions: Using gene expression results derived from microarray analyses of LCM-procured breast carcinoma cells of primary lesions, subsets of autophagy related genes were identified that predict a patient's risk of recurrence and overall survival. Expression of a number of candidate genes appears to be related to either/both the ER or PR protein status of the primary lesion. Collectively, results suggest that expression of certain autophagy related genes may serve as biomarkers for assessing prognosis of breast carcinoma thus impacting clinical management of breast cancer.

Citation Format: Wittliff JL, Hameed ZR, Daniels MW, Cheng A. Expression of autophagy related genes impacts clinical outcomes of human breast carcinoma and is associated with estrogen and progestin receptor status [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P1-01-12.

Abstract P3-05-11: Clinical outcomes of estrogen-receptor negative breast carcinoma are associated with protein hormone-cognate receptor gene expression

Background: Since certain protein hormones appear to be associated with progression of breast cancer cells in vitro, we employed a global approach by evaluating relationships between genes for these hormones and their cognate receptors in human breast cancer biopsies as independent predictors of risk of recurrence. Our goal is to derive clinically relevant molecular signatures correlating various ER/PR subtypes.

Methods: Microarray analyses of LCM-procured carcinoma cells from 247 de-identified biopsies determined expression of genes for 61 protein hormones (the ligands) and 81 cognate receptors. Total RNA was extracted, purified and amplified from cells to determine expression of 22,000 genes. Univariable and multivariable Cox regressions were determined using expression levels of each hormone/receptor gene. Kaplan-Meier plots were constructed with an adjusted p-value <0.30 (discovery cutoff) for each gene candidates with/without ER status of the lesion. Cox regression analyses with/without interaction models deciphered candidates of hormone-receptor complexes that predicted risk of recurrence as well as overall survival using clinical follow-up that extended as much as 12 years. LASSO was used to derive gene subsets to predict overall survival (OS) and progression free survival (PFS) within ER/PR subtypes.

Results: Expression levels of 7 genes for protein hormones and 10 receptor genes were significant for OS at an adjusted p-value of <0.30 while expression of 15 hormone and 19 receptor genes were significant for PFS without regard to ER/PR subtypes. When expression levels were considered with ER status only, 3 genes for ER+ lesions and 6 genes for ER- lesions were identified that predicted OS/PFS. Categorization of cancers according to combined ER and PR status revealed one gene for ER+/PR+, 3 genes for ER+/PR- and 2 genes for ER-/PR- associated with PFS/OS. After stratifying gene expression into above/below median for the linear predictor, Kaplan-Meier plots revealed patient groups with each signature for ER+/PR+, ER-/PR- and ER- lesions that exhibited significantly different survival. Molecular signatures comprising 16 genes for ER+/PR+ carcinomas, 10 genes for ER-/PR- lesions and 6 genes for ER- carcinomas predicted clinical outcomes with C-indices of 0.79, 0.76 and 0.71, respectively.

Conclusion: We revealed many breast carcinomas synthesize mRNA species for various protein hormones and their cognate receptors by determining gene expression directly on pure populations of these cells procured by LCM. We report a novel ten-gene ER-/PR- signature containing four genes in common with that of a six-gene ER- only signature that predicts breast cancer recurrence. Collectively, results of mRNA expression suggest that often breast carcinomas exhibit substantial elements of endocrine autonomy for regulating progression, warranting investigation of protein products of gene candidates in isolated populations of breast carcinoma cells.

Citation Format: Daniels MW, Wittliff JL, Brock GN. Clinical outcomes of estrogen-receptor negative breast carcinoma are associated with protein hormone-cognate receptor gene expression [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P3-05-11.

Abstract P3-04-06: Expression of genes for peptide/protein hormones and their receptors in breast carcinomas as biomarkers predicting risk of recurrence

Background: Several reports have suggested expression of certain peptide/protein hormones in breast cancer cells appear to be related to clinical behavior. We have taken a global approach by evaluating relationships between genes for these hormones and their cognate receptor proteins as independent predictors of risk of recurrence.

Methods: Expression of genes for 55 peptide/protein hormones (the ligands) and 73 of their cognate receptor proteins were measured by microarray analyses of LCM-procured carcinoma cells from 247 breast carcinoma biopsies. Using an IRB-approved biorepository and comprehensive database, total RNA was extracted from carcinoma cells to determine expression levels of 22,000 genes. Univariate and multivariate Cox regressions with interaction were determined using expression values of each ligand and its cognate receptor with an interaction term.

Results: When pairs of hormone ligand and cognate receptor genes were evaluated by multivariate Cox regression with interaction, the following sets of genes were identified that predicted risk of breast cancer recurrence (INS/IGF2R, HAMP/SLC40A1, POMC/MC4R, GH1/GHR and VIP/VIPR2) and OS (CORT/SSTR5, VIP/VIPR2 and GHRH/GHRHR, based on unadjusted p-value for interaction term < 0.05). Since expression in situ of both hormone and receptor are necessary to elicit endocrine action, a unique alternative approach using the minimum expression value between ligand and receptor for each patient was applied. These results revealed that the complex of HAMP/SLC40A1 showed significance in both the interaction and minimum models, and was further investigated by splitting the ligand and receptor into low (below 1st quartile) and high (above 1st quartile) expression groups. The group consisting of high expression for both ligand and receptor was contrasted with the other three groups (low expression for ligand, receptor, or both). The higher expression group exhibited a better DFS (hazard ratio (HR) = 0.56 95% CI 0.37-0.84, p=0.004) and OS (HR = 0.59 95% CI 0.37-0.93, p=0.022).

Conclusion: As a result of determining gene expression directly on pure populations of breast carcinoma cells procured by LCM, we have demonstrated the many lesions synthesize mRNA species for a wide variety of peptide and protein hormones as well as for their cognate receptor proteins. Using clinical follow-up that extended as much as 12 years, univariate and multivariate Cox regression analyses with and without interaction models revealed a number of noteworthy candidates of hormone-receptor complexes that predicted risk of breast cancer recurrence as well as overall survival. Collectively, our results suggests that many breast carcinomas exhibit considerable endocrine autonomy for controlling progression, which warrants investigation of the protein products of the gene candidates in isolated populations of breast carcinoma cells.

Citation Format: Wittliff JL, Daniels MW, Brock GN. Expression of genes for peptide/protein hormones and their receptors in breast carcinomas as biomarkers predicting risk of recurrence. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P3-04-06.

Abstract P6-03-14: Expression of genes for aromatase inhibitor targets to discriminate invasive lobular from invasive ductal carcinomas of the breast using LCM-procured cells to complement endocrine biomarkers

Background: The BIG 1-98 trial and later the ABCSG 8 study reported that patients with invasive lobular carcinoma (ILC) exhibited better response to aromatase inhibitors (AIs) compared to those with invasive ductal carcinoma (IDC). Aromatase cytochrome P450 (CYP19) synthesizes estrogen from androgens and is the target of AI's. CYP19 substrates are generated by upstream enzymes including estrone sulfatase (SULT1E1) and 3b-hydroxysteroid dehydrogenase type 1 (HSD3B1). Enzymes of the aromatase pathway have been reported to be expressed in intact tissue biopsies of breast cancer. To learn more about the pathogenic mechanisms that may underlie the survival benefit of ILCs treated with AIs, we analyzed expression levels of key enzymes related to the aromatase pathway in ILC and IDC. Unlike previous studies, we determined gene expression levels directly on pure populations of carcinoma cells procured by laser capture microdissection, eliminating the contribution of non-cancerous cells.

Methods: Using an IRB-approved biorepository and database, total RNA was extracted from carcinoma cells of 247 de-identified biopsies to perform microarray analyses of 22,000 genes. Of the 247 samples, 16 were ILC, 13 were low grade IDC, 55 were intermediate grade IDC and 85 were high grade IDC, and 107 of these were hormone receptor positive. CYP19, HSD3B1 and SULT1E1 expression was directly detected in LCM-procured breast carcinoma cells of ILC and of IDC. Expression of other genes generally associated with the aromatase pathway, e.g., NADPH-cytochrome P450 reductase (POR), ATP-binding cassette gene (ABCG2), catechol-o-methyltransferase (COMT) and uridine-5'-diphosphate glucuronosyltransferase (UGT1A3 & UGT1A9) as well as HSD17B2 were assessed with LCM-procured cells. Estrogen receptor (ER) and progesterone receptor (PR) proteins were quantified by radio-ligand binding and EIA, and gene expression was validated by qPCR.

Results: Univariate Cox regression analyses indicated that ABCG2, HSD17B2and UGTA3 independently predicted disease free and/or overall survival of breast carcinomas. We found that CYP19 expression in carcinoma cells, as well as SULT1E1, COMT, POR, HSD17B2 and UTG1A3 expression, decreased as either ER or PR protein increased. HSD3B1 appeared to be over-expressed in ILC compared to IDC, however this difference did not approach statistical significance, likely due to the small sample size. No differences were seen in expression levels of CYP19 and SULT1E1 between ILC and IDC.

Conclusions: An inverse relationship between CYP19 and ER and PR expression levels was observed and suggests that synthesis of estrogens by breast cancer cells in situ plays a significant role in defining tumor biology. Our results also indicate overexpression of HSD3B1 in ILC, although not statistically significant. This finding suggests that HSD3B1 may be a key contributor to the increased benefit of AI therapy seen in ILC. Collectively our results suggest a comprehensive study is warranted to ascertain the molecular basis for differences in expression of genes directing estrogen synthesis in situ in relationship to AI therapeutic responses of histologic subtypes of breast carcinomas.

Citation Format: Sanders MAG, Daniels MW, Wittliff JL. Expression of genes for aromatase inhibitor targets to discriminate invasive lobular from invasive ductal carcinomas of the breast using LCM-procured cells to complement endocrine biomarkers. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P6-03-14.

Abstract P4-04-03: A microgenomic approach using LCM procured breast cancer cells to identify clinically relevant gene signatures that underlie favorable response of ILC to aromatase inhibitors

Based on CGH analyses, invasive lobular carcinoma (ILC) is closely related to low grade invasive ductal carcinoma (IDC), and is genetically unrelated to intermediate and high grade invasive carcinomas (Pathol Res Pract 2005; 201:713). Results from the BIG 1-98 trial, showed that patients with ILC and luminal B (intermediate/high grade) IDC treated with Letrozole, an aromatase inhibitor (AI), had a significant improvement in overall survival, whereas patients with luminal A (low grade) IDC did not (Cancer Res 2012; 72(24 Suppl):Abstract nr S1-1). Despite genetic evidence suggesting a close relationship between ILC and low grade IDC, and disparity between ILC and intermediate and high grade IDC, a clinically relevant gene set underlying a tumor's biologic responsiveness to AIs likely exists. We are deciphering a gene subset that would differ in expression between low grade IDC and ILC, and would be shared by ILC and luminal B IDC. Identification of such a gene set should lead to a more robust marker for identifying AI responsive tumors rather than relying solely on histomorphology and/or immunohistochemistry for the pathologic diagnosis of ILC, since the distinction between ILC and IDC is not always straight forward in pathology practice.

Using 247 de-identified human breast carcinoma biopsies collected under standardized, stringent conditions, total RNA was extracted from carcinoma cells procured by laser capture microdissection to perform microarray analyses of approximately 22,000 genes to identify expression signatures associated with breast cancer characteristics. Of the 247 samples, 169 samples were used for the analysis and included 16 ILCs, 13 low grade IDCs, 55 intermediate grade IDCs and 85 high grade IDCs.

Preliminary analyses identified 1267 genes that were differentially expressed (p<0.01) between cell samples from patients with IDC compared to those with ILC. Gene expression levels in breast cancer cells from patients with low grade IDC compared to those with ILC yielded 200 genes that were statistically differentially expressed (p<0.01). When comparing high grade IDC to ILC, 149 of these genes were not differentially expressed indicating that this gene set may serve as a panel of candidate genes for identifying cancers responsive to AIs. Pathway analysis software (Ingenuity®) identified that these genes were associated with key molecular and cellular functions, e.g., cell-to-cell signaling, cell morphology, cell death and survival, cellular assembly and organization and carbohydrate metabolism. qPCR analyses are used to validate and refine the gene subset distinguishing ILC from low grade IDC. Our approach is revealing subtle molecular features that discriminate these lesions based on clinical behavior. Supported in part by a grant from the Phi Beta Psi Charity Trust.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P4-04-03.

Expression of small sets of genes in carcinoma and stromal cells predict clinical behavior of human breast cancer

Abstract #6146

Background: The Human Genome Project has provided opportunities to develop precise tests for diagnostics, therapy selection and monitoring. From reiterative analyses of various microarray studies, 14 genes expressed in human breast carcinoma cells procured from de-identified tissue sections by LCM and 18 genes predicted in adjacent stromal cells were identified, whose expression appears related to clinical outcome. An additional 11 genes were identified in estrogen receptor positive (ER+) breast cancer exhibiting different survival probabilities. These genes have been evaluated with qPCR and with a disposable TipChip array (Xceed Molecular) as candidates for development of a prognostic test measuring clinically relevant gene expression profiles.
 Materials and Methods: RNA was isolated from 118 frozen tissue biopsies using the RNeasy® Mini kit (Qiagen) and analyzed for quality and quantity using the Bioanalyzer (Agilent). cDNA for qPCR measurements was prepared in Tris-HCl buffer containing KCl, MgCl2, DTT (Invitrogen), dNTPs (Invitrogen), RNasin® (Promega) and Superscript® RT III (Invitrogen). qPCR reactions were performed using Power Sybr® Green PCR Master Mix (Applied Biosystems), forward/reverse primers and cDNA obtained from the reverse transcription reaction. Relative gene expression was calculated with the ddCt method, using β-actin as the housekeeping gene and Universal Human Reference RNA (Stratagene) as a calibrator. Prior to gene expression analyses, extensive QC experiments were conducted, e.g., qPCR reactions were performed in triplicate with duplicate wells in each 384-well plate, to ensure reproducibility.
 Results: Gene candidates were analyzed on the Ziplex® Automated Workstation (Xceed Molecular) with a TipChip array containing probes for 61 genes including normalization controls. Preliminary gene expression results by qPCR and the TipChip were comparable for many of the 43 candidate genes (r2 ≥ 0.5 with ESR1 = 0.6). These data were correlated with disease-free and over-all survival outcomes stored in our extensive IRB-approved database. Expression of SLC39A6, FUT8 and CX3CL1 in the carcinoma/stromal subset correlated independently with disease-free survival using Cox Regression analyses (p < 0.02). Using the 13-gene subset derived from ER+ breast cancers, CAXII, ERBB4 and RERG correlated independently with recurrence (p < 0.03). These genes, as well as BCL2, correlated independently with overall survival (p < 0.02).
 Conclusion: Expression profiles of 21 of the 32 candidate genes from this gene subset predicted early breast cancer recurrence. In an ER+/PR+ subpopulation, ERBB4 and HER-2 gene expression correlated best with recurrence in a multivariate Cox model (p = 0.001). Collectively, results suggest that an expression test based on these genes will predict clinical outcome. Supported in part by grants from Phi Beta Psi Charity Trust, University of Louisville's Office of Technology Transfer and from Xceed Molecular Corp. SAA & DAK II are recipients of IPBIS Graduate Fellowships.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 6146.

Thioether side chain cyclization for helical peptide formation: inhibitors of estrogen receptor-coactivator interactions

Cystine, lanthionine, and cystathionine containing cyclic peptides incorporating the signature nuclear receptor (NR) box (LXXLL) motif have been synthesized and the abilities of these peptides to inhibit estrogen receptor (ER)-coactivator interactions have been determined. We found that helicity of these peptides directly correlated with their bioactivity. Cystathionine proved to be a redox-stable, isosteric replacement for the cystine disulfide. Cystathionine containing peptide 3 showed higher helical character and a lower inhibition constant (Ki, 7 nm) when compared with its cystine counterpart.

Prognosis and treatment of patients with breast tumors of one centimeter or less and negative axillary lymph nodes

BACKGROUND

Uncertainty about prognosis and treatment of axillary lymph node-negative patients with estrogen receptor (ER)-negative or ER-positive invasive breast tumors of 1 cm or less prompted the analysis of data from five National Surgical Adjuvant Breast and Bowel Project randomized clinical trials.

METHODS

Two hundred thirty-five patients with ER-negative tumors and 1024 patients with ER-positive tumors were identified in these trials. Patients with ER-negative tumors received surgery alone or surgery and chemotherapy. Patients with ER-positive tumors received surgery alone; surgery and tamoxifen; or surgery, tamoxifen, and chemotherapy. End points were relapse-free survival (RFS), event-free survival, and overall survival. A result was considered to be statistically significant with a P value of.05 or less; all statistical tests were two-sided.

RESULTS

The 8-year RFS of women with ER-negative tumors who received surgery alone or with chemotherapy was 81% and 90%, respectively (P = .06). Survival was similar in both groups (93% and 91%; P = .65). The 8-year RFS of women with ER-positive tumors was 86% after surgery alone, 93% when tamoxifen was added (P = .01), and 95% after the addition of tamoxifen and chemotherapy (P = .07 compared with tamoxifen). Survival in the three groups was 90%, 92% (P = .41), and 97%, respectively. The difference between the latter two groups was significant (P = .01). Regardless of ER status or treatment, overall mortality was 8%; one half of the deaths were related to breast cancer. Several covariates affected the risk of recurrence in ER-negative and ER-positive patients. Risk was greater in women with tumors of 1 cm than in those with tumors of less than 1 cm, in women aged 49 years or younger than in those aged 50 years or older, and in women with infiltrating ductal or lobular carcinoma than in those with other histologic tumor types.

CONCLUSIONS

Chemotherapy and/or tamoxifen should be considered for the treatment of women with ER-negative or ER-positive tumors of 1 cm or less and negative axillary lymph nodes.

Clinical relevance of urokinase-type plasminogen activator, its receptor, and its inhibitor type 1 in endometrial cancer

OBJECTIVE

Tumor invasion involves degradation of extracellular matrix. The urokinase plasminogen activation system participates in this process. Urokinase-type plasminogen activator (uPA), its receptor (uPAR), and its inhibitor, plasminogen activator inhibitor type 1 (PAI-1), are proposed to be prognostic factors in some cancers. There are conflicting data regarding the prognostic role of this system in endometrial cancer.

METHODS

To determine the prognostic value of the urokinase plasminogen activation system, contents of uPA, uPAR, and PAI-1 were measured in extracts of endometrial cancer tissue using ELISAs. uPA, uPAR, and PAI-1 levels were determined in 91, 54, and 92 extracts, respectively, and correlated with tumor histology, stage, grade, lymph node involvement, prevalence of metastasis, and recurrence as well as with estrogen (ER), progesterone (PR), epidermal growth factor (EGFR) receptor and HER-2/neu contents.

RESULTS

Patients with cancers exhibiting advanced stage, high grade, unfavorable tumor histology, nodal involvement, recurrence, and lower PR levels determined by ligand binding had significantly higher uPA content than others. PAI-1 was significantly elevated in patients with advanced stage, high-grade tumor, recurrence, decreased ER content, and lower PR levels determined by ligand binding. uPAR did not show any relation to any of clinical and laboratory parameters. Elevated expression of PAI-1 was associated with significantly shorter disease-free (P = 0.005) and overall (P = 0.0003) survival. Multivariate analysis revealed that PAI-1 was a predictor of survival although stage was the strongest independent factor.

CONCLUSION

Elevated uPA and PAI-1 levels appear to correlate with unfavorable prognosis in endometrial cancer.

Clinical relevance of urokinase-type plasminogen activator, its receptor and inhibitor type 1 in ovarian cancer

Urokinase-type plasminogen activator (uPA), its receptor (uPAR) and inhibitor, plasminogen activator-type 1 (PAI-1) are proposed to be of prognostic significance in some cancers. To determine the prognostic value of the urokinase plasminogen activation system in ovarian cancer, levels of uPA, uPAR, and PAI-1 were measured in extracts of ovarian cancer tissue using ELISA tests. uPA and PAI-1 were determined in 70 tumor extracts and uPAR in 43 extracts. Levels were correlated with age, tumor histology, stage, grade, lymph node and metastatic status, residual disease, risk of recurrence, epidermal growth factor receptor (EGFR) expression, cathepsin D (Cath-D), and c-erbB-2 levels. uPA and uPAR did not exhibit correlation with any of these parameters. However, patients with high grade tumor, recurrence, and lower EGFR and Cath-D had significantly higher PAI-1 levels compared to those of others (P < 0.05). Kaplan-Meier plots of survival were compared. uPA and uPAR were not related to disease-free or overall survival. Although low PAI-1 appeared to predict a longer overall survival, the difference was not statistically significant. Multivariate analysis revealed that PAI-1 was a predictor for overall survival although it was not as strong as stage. These results suggest that elevated PAI-1 seems to be correlated with an unfavorable prognosis in ovarian cancer.

Interaction of angiogenesis inhibitor TNP-470 with basic fibroblast growth factor receptors

TNP-470 is a synthetic analogue of fumagillin that acts as a potent angiogenesis inhibitor. Recently, our laboratory demonstrated that systemic administration of TNP-470 (5.0 mg/kg) decreased the rate of cutaneous wound healing by greater than 20%. In this study, we tested the hypothesis that TNP-470 interferes with the wound repair-stimulating action of basic fibroblast growth factor (bFGF) by competing with endogenous bFGF for its binding sites on the receptor protein. The influence of TNP-470 was examined in vitro in a ligand competition assay of high- and low-affinity receptor binding to (125)I-bFGF in NIH/3T3 cells. Results demonstrated that recognition of (125)I-bFGF by low-affinity growth factor binding sites was significantly decreased (P < 0.01) in the presence of TNP-470. However, TNP-470 inhibition of radiolabeled bFGF binding to high-affinity sites was not significantly affected (P = 0.07). In view of recent studies demonstrating that the low-affinity receptors of bFGF were heparan sulfate proteoglycans, we suggest that the influence of TNP-470 on diminished wound healing is due to its direct recognition by these molecules.

Presence and characteristics of receptors for [D-Trp6]luteinizing hormone releasing hormone and epidermal growth factor in human ovarian cancer

This study was undertaken to establish the presence and characteristics of receptors for [D-Trp6]LH-RH on the membranes of human ovarian cancer. Specific binding of [125I, D-Trp6]LH-RH was found in 29 of 37 (78.4%) ovarian cancers and in 6 of 11 (54.5%) non-malignant human ovaries. Ligand binding was dependent on time and plasma membrane concentration in a fashion expected of a peptide hormone. Saturation, kinetic and displacement data were consistent with the presence of a highly specific, single class of non-cooperative binding site. On the basis of receptors affinity, LH-RH-receptor-positive ovarian cancers could be divided into two groups: high affinity group (Kd=2.71 +/- 0.60 nM; Bmax=0.46 +/- 0.07 pmol/mg membrane protein) comprising 55% of tumors, and low affinity group (Kd=78.0 +/- 19.6 nM; Bmax=9.44 +/- 2.68 pmol/mg membrane protein) which included 45% of tumors. LH-RH antagonist Cetrorelix showed an affinity to LH-RH receptors on ovarian cancers 14 times higher than the agonist [D-Trp6]LH-RH. Using 125I-epidermal growth factor, specific high affinity receptors were also detected in membranes from 13 of 24 (54%) ovarian cancers and 5 of 11 (45%) non-malignant ovaries. The demonstration of LH-RH receptors in human ovarian cancers provides a rationale for the use of therapeutic approaches based on LH-RH analogues in this malignancy. The probable involvement of growth factors in the development of ovarian cancers suggests the merit of trying a combined therapy based on analogs of LH-RH and somatostatin for this carcinoma.

Structural and functional analysis of N-terminal point mutants of the human estrogen receptor

Twenty N-terminal point mutations of the human estrogen receptor (hER) were constructed as ubiquitin fusion products and expressed under the control of the copper regulated promoter CUP1 in Saccharomyces cerevisiae. The objective of these studies was to overexpress hER in yeast and also to evaluate the functional properties of the N-terminal variants of hER. Fusion of the C-terminus of ubiquitin to the N-terminus of other proteins has been shown to increase the level of protein expression in yeast. Ubiquitin C-terminal hydrolases (UCHs) in yeast efficiently and precisely cleave at the junction with ubiquitin and render free hER with desired amino termini. The variant hER proteins, that were generated by mutating the N-terminus of hER, showed enormous differences in receptor protein levels and transactivation potential. All variant hER proteins were synthesized as 66 kDa species as identified by Western blotting with the exception of the proline-containing variant (Pro-ER). The UB-Pro-ER variant was cleaved inefficiently by UCHs in yeast. The UB-Pro-hER [correction of UB-Pro-hEr] variant also exhibited a different DNA band-shift profile compared to those of the other receptor variants and the wild-type. Val-, Thr-, and Lys-ER did not express, as measured by enzyme-immunoassay and Western blotting; nor did they transactivate a beta-galactosidase reporter gene in yeast. However, the Glu-ER was 50% more active in transactivation as compared to the wild-type. The results of the receptor content, DNA binding properties and transactivation analysis in yeast demonstrate that the N-terminal residue plays an important role in the structure and function of hER.

Quantitative analyses of epidermal growth factor receptors, HER-2/neu oncoprotein and cathepsin D in nonmalignant and malignant uteri

BACKGROUND

Hormone receptors and oncoproteins are receiving increased attention as possible prognostic factors in different carcinomas. Few data are available regarding quantification of their levels of expression in gynecologic malignancies.

METHODS

Epidermal growth factor (EGF) receptor specific binding capacities and affinities were measured by ligand binding assay using [125I]EGF in a competition mode with Accufit software (Lundon Software, Inc., Middlefield, OH). HER-2/neu oncoprotein was extracted from membranes and measured using an enzyme-linked immunosorbent assay. Cathepsin D was measured by an immunoradiometric assay using cytosols for steroid receptor analyses.

RESULTS

EGF receptors in 23 nonmalignant uteri ranged from undetectable to 50 fmol/mg membrane protein (median, 0), with dissociation constant values of 1.2 x 10(-9) M to 8.5 x 10(-10) M, compared with EGF receptors in 76 endometrial cancers that ranged from undetectable to 7674 fmol/mg (median, 52). HER-2/neu oncoprotein ranged from undetectable to 2.9 HER-2/neu units (HNU)/microg protein (median, 0.6) in 41 nonmalignant uteri and from undetectable to 5.8 HNU/microg protein (median, 2.5) in endometrial cancers (n = 53). Cathepsin D ranged from 5 to 32 pmol/mg cytosol protein (median, 11) in 42 nonmalignant uteri and 18 to 144 pmol/mg protein (median, 42) in 29 endometrial cancers.

CONCLUSIONS

Determination of the frequency and levels of EGF receptors, HER-2/neu protein, and cathepsin D in uteri with and without cancer and the availability of reference materials developed in our laboratory, will allow evaluation of their prognostic value in cancers of the uterus.

Relation between cathepsin D expression and other prognostic factors in breast carcinomas

We evaluated cathepsin D concentrations in 318 breast carcinoma specimens with a standardized IRMA and established distribution values of 5.9-217.8 nmol/g (median 51.8). Concentrations of cathepsin D did not correlate with age or with concentrations of HER-2/neu oncoprotein, estrogen receptor, or epidermal growth factor receptors. A significant correlation was observed between cathepsin D and progestin receptor (P = 0.009), but only in postmenopausal patients. In our role as a National Reference Laboratory for conducting interlaboratory comparisons of tumor markers, we evaluated cathepsin D assay proficiency by using control samples with intra- and interassay CVs of 2-8% and 10-13%, respectively. Human reference specimens containing known quantities of cathepsin D were developed to facilitate standardized testing. The IRMA procedure and the use of quality-assurance samples permits evaluation of the clinical significance of cathepsin D in human breast cancer trials.

Relation between cathepsin D expression and other prognostic factors in breast carcinomas

We evaluated cathepsin D concentrations in 318 breast carcinoma specimens with a standardized IRMA and established distribution values of 5.9-217.8 nmol/g (median 51.8). Concentrations of cathepsin D did not correlate with age or with concentrations of HER-2/neu oncoprotein, estrogen receptor, or epidermal growth factor receptors. A significant correlation was observed between cathepsin D and progestin receptor (P = 0.009), but only in postmenopausal patients. In our role as a National Reference Laboratory for conducting interlaboratory comparisons of tumor markers, we evaluated cathepsin D assay proficiency by using control samples with intra- and interassay CVs of 2-8% and 10-13%, respectively. Human reference specimens containing known quantities of cathepsin D were developed to facilitate standardized testing. The IRMA procedure and the use of quality-assurance samples permits evaluation of the clinical significance of cathepsin D in human breast cancer trials.

Characterization of bombesin/gastrin-releasing peptide receptors in human breast cancer and their relationship to steroid receptor expression

Bombesin (BN) and its mammalian counterpart, gastrin-releasing peptide (GRP), are hormonally active peptides which appear to function as autocrine or paracrine growth factors in a variety of cells. As part of a long-term investigation of the relationship of peptide and steroid hormone receptors to breast cancer progression and treatment, we examined the binding of [125I-Tyr4]BN to membranes isolated from 100 human breast carcinomas. Thirty-three of these tumors expressed BN/GRP receptor levels of > 10 fmol/mg membrane protein. Two classes of [Tyr4]BN-binding sites were detected using Scatchard analyses of radioligand association data from hormone displacement curves. The high-affinity binding sites exhibited a mean dissociation constant (Kd1) of 2.1 nM and a mean specific binding capacity (Bmax1) of 237 fmol/mg membrane protein. The low affinity binding sites had a mean dissociation constant (Kd2) of 0.3 microM and a mean binding capacity (Bmax2) of 5.9 pmol/mg membrane protein. BN/GRP receptor expression in a breast carcinoma was unrelated to patient age. When the levels of BN/GRP receptors were compared to the content of the sex steroid receptors, a highly significant positive correlation (P < 0.005) was observed between the binding capacities of high-affinity [Tyr4]BN-binding sites and estrogen receptor levels and between the concentrations of low affinity [Tyr4]BN-binding sites and progestin receptor levels (P < 0.05). This represents the first report of these labile, regulatory proteins in biopsies of human breast carcinomas. Expression of specific receptor proteins for BN/GRP, potent mitogens, in a large number of human breast cancers suggests that they may be involved in tumor cell progression. The approach based on determination of BN/GRP receptors might be useful to guide a hormonal therapy with BN/GRP antagonists in some women with breast cancer.

Comparison of cathepsin D determinations in human carcinomas by enzyme immunoassay and immunoradiometric assay

Overexpression of cathepsin D in several types of carcinoma in women appears to be associated with a poor clinical course. In this prospective investigation, cathepsin D levels in 170 specimens of normal and neoplastic human tissues were determined simultaneously by enzyme immunoassay (EIA) and immunoradiometric assay (IRMA) to allow comparisons in multicentric studies, such as cooperative clinical trials. Nonmalignant uteri and specially prepared reference powders were also evaluated. Linear regression analysis between the two assays for all specimens [EIA = 0.87(IRMA)-3.18] demonstrated a correlation coefficient (r) of 0.99 (P < 0.001). When malignancies were categorized by the tissue origin (i.e., breast, uterus, ovary, lymph node, and colon), highly significant correlations were also observed (regressions slopes ranged from 0.58 to 1.02). Intra- and interassay controls conducted for the new EIA procedure gave CV% ranging from 4.4 to 10.2, which was similar to the IRMA test for cathepsin D. The results of both assays correlated well and were highly reproducible. Either assay may be used with confidence that comparable cathepsin D values will be obtained in a wide range of tissue biopsies.

Expression of urokinase-type plasminogen activator and plasminogen activator inhibitor in colon disease

Surveillance colonoscopy and biopsy are inaccurate methods of predicting the likelihood of ulcerative colitis patients to develop colon carcinoma. We examined uPA and PAI-1 as potential markers for assessing these patients and those with familial polyposis who are at risk of developing colon cancer. For comparison, biopsies of normal colon and Crohn's disease were evaluated. We examined 77 colonic mucosa specimens taken from patients undergoing elective resection for benign and malignant colonic disease. uPA and PAI-1 were measured using a monoclonal antibody-based ELISA kit (American Diagnostica, Greenwich, CT) and expressed as ng/mg extract protein. Intra- and interassay controls of uPA gave CV = 3-4% and CV = 8-9%, respectively, while those for PAI-1 were 6-7% and 10-11%, respectively. The Mann-Whitney test showed that both uPA and PAI-1 expression were significantly higher in colon cancer, chronic ulcerative colitis, and Crohn's disease than in normal colon. uPA in familial polyposis samples was similar to that of normal colon, while PAI-1 was much lower than in normal colon. Neither patient age nor sex appeared to influence the expression of these potential markers in any tissue. The pattern of uPA and PAI-1 expression in normal, benign and malignant colon suggests these proteins deserve further consideration as markers for assessing colon carcinoma risk.

Inhibition of growth of the human malignant glioma cell line (U87MG) by the steroid hormone antagonist RU486

Treatment of nude mice bearing xenografts of the human malignant glioma U87MG cell line with the steroid hormone antagonist RU486 for 4 weeks resulted in a significant and dose-dependent suppression of tumor volume and weight. Receptor analyses of tumor cytosol preparations demonstrated a single class of high affinity binding sites for dexamethasone, but the absence of receptors for progesterone. RU486 also nullified the stimulatory effect of dexamethasone on proliferation of U87MG cells in vitro. These results indicate that the growth of U87MG human malignant glioma is dependent on corticoids. The antiproliferative effect of RU486 appears to be due to the inhibition of binding of glucocorticoid hormones to their receptor proteins. Our results suggest a new therapy for some brain tumors, such as malignant gliomas based on the steroid hormone antagonist RU486.

Expression of hormone receptors, cathepsin D, and HER-2/neu oncoprotein in normal colon and colonic disease

BACKGROUND

Chronic ulcerative colitis and familial adenomatous polyposis are associated with an increased risk of colorectal carcinoma. Currently, there are no reliable methods to assess carcinoma risk.

METHODS

Several prognostic factors known to be useful in breast carcinoma were determined in 102 specimens of colonic mucosa from 38 patients: 22 specimens from "normal," non-neoplastic colon, 49 from chronic ulcerative colitis, 10 from Crohn's colitis, 14 from familial adenomatous polyposis, four from mucosa adjacent to carcinoma, and three from colon carcinoma. Expression of estrogen receptor, progestin receptor, epidermal growth factor receptor, HER-2/neu (c-erb B-2) oncoprotein, and cathepsin D were determined.

RESULTS

Epidermal growth factor receptor expression was higher in chronic ulcerative colitis, Crohn's colitis, familial adenomatous polyposis, and colon carcinoma and varied with location within the colon for chronic ulcerative colitis, Crohn's colitis, and familial adenomatous polyposis. Epidermal growth factor receptor expression in mucosa adjacent to carcinoma was similar to that in "normal" colon.

CONCLUSION

Further analyses are needed to determine which parameters are related to and possibly predictive of increased carcinoma risk.

Bromodeoxyuridine labeling for S-phase measurement in breast carcinoma

BACKGROUND

The S-phase fraction relates to proliferation, an important determinant of tumor behavior, and has been measured most accurately with the DNA precursor tritiated thymidine (TT). The TT labeling index (LI) is a strong stage-independent prognostic indicator for breast carcinoma. The thymidine analogue 5-bromodeoxyuridine (BrdU) is also incorporated into DNA and has the advantage over TT of immunohistochemical detectability rather than requiring autoradiography, but it is less well studied in breast carcinoma. This report demonstrates the equivalence of TT and BrdU LI and explores the relationships between LI and other biologic measurements.

METHODS

The LI of 234 consecutive breast carcinomas were measured with TT as was a subsequent series of 450 cases with BrdU, both by incubation in vitro.

RESULTS

The mean BrdU LI was 6.4 +/- 0.3% in comparison with 6.9 +/- 0.4% in the prior TT series. LI was unaffected by storage for 24 hours at 4 degrees C before labeling with BrdU. The BrdU and TT LI both correlated: (1) positively with tumor size, histologic type, nuclear size, the number of axillary metastases, the level of DNA ploidy, and the percent S-phase by flow cytometry and (2) negatively with the age of the patient and the levels of estrogen receptor and progesterone receptor measured either by ligand binding or by immunohistochemistry.

CONCLUSIONS

BrdU labeling in vitro was an advantageous method for measuring S-phase fraction in breast carcinoma that produced results comparable to those from TT labeling. It should be equally effective for breast cancer kinetic classification and prognosis and is a suitable standard to evaluate newer methods for measuring cellular proliferation.

Influence of estrogen receptor variants in mammary carcinomas on the prognostic reliability of the receptor assay

We have used GR mouse mammary carcinomas as a model for evaluating the effect of estrogen receptor (ER) variants, present in the tumor cytosols, on the prognostic reliability of the receptor assay. Rapid, high resolution procedures were used for the assessment of wild-type and variant estrogen receptors in the cytosols of hormone-responsive and nonresponsive mammary tumors of GR mice. Two main ER types were resolved by high performance ion-exchange and size-exclusion chromatography: the wild-type receptor (II), and a fraction representing low molecular weight ER (I). ER types I and II both bound estradiol and both reacted with the anti-ER monoclonal antibodies H222 and D547 whose epitopes are in the C-terminal part of ER. The level of ER type II was higher in hormone-responsive than in hormone-nonresponsive tumors, whereas ER type I was about equally low in both types of tumor groups. ER types I and II both influence the standard ligand binding and antibody binding (Abbott EIA) test, but only the wild-type ER causes hormone-responsive growth of the tumor. These data suggest that prognostic clinical tests, currently in use for estimating ER in tumors of breast cancer patients, may be impaired by the presence of low molecular weight estrogen receptor variants in the tumor samples.

Regional heterogeneity in breast carcinoma: thymidine labelling index, steroid hormone receptors, DNA ploidy

We examined multiple samples of 65 primary breast carcinomas larger than 1 cm in diameter for thymidine labelling index (TLI), DNA index (DNAI, a measure of cellular DNA content by flow cytometry), and estrogen (ER) and progesterone (PgR) receptors by radioligand-binding. One or more axillary metastases were also assayed in 11 patients. Two to 15 samples were successfully assayed for TLI from 59 tumors, 2-31 samples for DNAI from 61 tumors, and 2-15 samples from 55 tumors for ER and PgR. Criteria for heterogeneity were excess inter-sample variance in comparison with intrasample variance at the p less than 0.05 level for TLI and DNAI, and variation of clinically significant magnitude in assay results for ER and PgR. Sixty-one percent of tumors were heterogeneous for TLI, 26% for DNAI, 24% for ER and 40% for PgR. High TLI disposed toward heterogeneity for TLI itself (p = 0.06), for ER (p = 0.04), and for PgR (p = 0.007). Young age favored heterogeneity for TLI (p = 0.12), ER (p = 0.002), and PgR (p = 0.04). Heterogeneity for DNAI was not related to age and TLI status but was more common in larger tumors (p = 0.08). After consideration of relationships between TLI, age, size, ER and PgR, TLI rather than age appears to be the more important determinant of heterogeneity for receptors. High TLI could lead to heterogeneity through increased numbers of cell divisions that favor emergence of variant stemlines, or by causing local vascular and humoral disparities through rapid growth. Regional heterogeneity can explain erroneous prognostic predictions in approximately 10% to 20% of breast carcinoma patients. We recommend multiple sampling of large breast carcinomas and analysis of axillary metastases for study of tumor markers.

Expression and characterization of an active human estrogen receptor as a ubiquitin fusion protein from Escherichia coli

The gene coding for the human estrogen receptor protein was expressed as a ubiquitin fusion under the control of the lambda PL promoter in Escherichia coli. Analysis of extracts by Western blot showed that intact receptor protein was produced only when PL promoter was depressed by nalidixic acid at 30 degrees C. To ascertain the intactness of the expressed protein, estrogen receptor in bacterial extracts was titrated with either 17 beta-[3H]estradiol or 17 beta-[125I]iodoestradiol, and the mass was quantified by enzyme immunoassay. Cell extracts contained 484 fmol of estrogen receptor per mg of soluble protein by titration with a Kd of 3.2 x 10(-10) M. The simultaneous analysis by enzyme immunoassay resulted in 487 fmol/mg of extract protein indicating that most of the expressed protein bound ligand with wild type properties. Ligand competition analysis demonstrated that expressed receptor contained a binding domain preferentially recognizing estrogenic substances identical with that of wild-type estrogen receptor. The E. coli-expressed estrogen receptor also associated specifically with estrogen response DNA elements. Full length receptor protein was detected by ligand binding and immunorecognition using size exclusion chromatography. Hydrophobic interaction chromatography showed a major isoform which exhibited both ligand binding and immuno-recognition identical with the estrogen receptor from human breast tumor tissues. These data indicate that estrogen receptor expressed in E. coli retained characteristics of the native protein found in human tissues.

Detection and partial characterization of receptors for [D-Trp6]-luteinizing hormone-releasing hormone and epidermal growth factor in human endometrial carcinoma

In view of advancements in treatment of certain hormone-dependent cancers with analogues of luteinizing hormone-releasing hormone (LH-RH), this study was undertaken to establish the presence and characteristics of receptors for [D-Trp6]LH-RH on the membranes of human endometrial cancer. Specific binding of [125I,D-Trp6]LH-RH was demonstrated in membrane preparations from 24 of 31 (77%) endometrial carcinomas and from 3 of 13 (23.1%) nonmalignant human endometrial specimens. Ligand binding was dependent on temperature, time, and plasma membrane concentration in a fashion expected of a peptide hormone. Mathematical analysis of the binding data showed that interaction of [125I,D-Trp6]LH-RH with the binding sites was consistent with the presence of a single class of high affinity, noncooperative receptors (Kd 9.88 +/- 4.59 x 10(-9) M; Bmax 0.70 +/- 0.14 x 10(-12) mol/mg membrane protein). The rates of association and dissociation were calculated to be 6.5 x 10(6) M-1 min-1 and 0.021 min-1, respectively. [125I,D-Trp6]LH-RH binding was not displaced by either unlabeled somatostatin or epidermal growth factor, but was displaced completely by native LH-RH. Using 125I-epidermal growth factor, specific, high-affinity receptors were also detected in membranes from 22 of 26 (85%) endometrial cancers and in all of 6 nonmalignant endometrial specimens (Kd 0.42 +/- 0.12 x 10(-9) M; Bmax 0.30 +/- 0.15 x 10(-12) mol/mg membrane protein). The potential functional role of the receptors for [D-Trp6]LH-RH in human endometrial carcinoma is not clear, but this finding provides a rationale for the use of therapeutic approaches based on LH-RH analogues in this malignancy.

Comparison of sex steroid receptor determinations in human breast cancer by enzyme immunoassay and radioligand binding

Most investigators comparing ligand-binding procedures for quantifying estrogen and progestin receptors in human breast cancer with procedures employing monoclonal antibody-based methods have utilized an inappropriate variety of reaction conditions, including the elimination of sodium molybdate in the steroid-binding assays. We studied 197 biopsies of human breast cancer, comparing the results of simultaneous measurements of both estrogen and progestin receptors in identical cytosols by enzyme immunoassay and by radioligand binding using the commercially available kits developed by Abbott Laboratories and by DuPont/NEN Products, respectively. Regression analyses comparing the results from the two procedures indicated a linear relationship, with correlation coefficients ranging from 0.79 to 0.93 for both types of receptors over a wide range of data. Using the widely established cutoff value of 10 fmol/mg of cytosol protein for the ligand-binding method, and calculating sensitivity and specificity limits according to McNeil et al. (1975), an equivalent cutoff value of 15 fmol/mg of cytosol protein was determined for the enzyme immunoassay of these receptors. Endocrine status of the patient did not appear to alter the cutoff values of either estrogen or progestin receptors when determined by enzyme immunoassay. We recommend that these cutoff values be considered until the results of clinical correlations are completed.

Influence of O.C.T. embedding compound on determinations of estrogen and progestin receptors in breast cancer

Estrogen receptor (ER) and progestin receptor (PR) concentrations in tumor biopsies are important predictive indicators of a clinical response to endocrine therapy of breast cancer. To assess interference of O.C.T. (optimum cutting temperature) embedding compound in assays of ER and PR by radioligand binding, we determined specific binding capacities and affinities of ER and PR in cytosols by a multipoint titration method, using split samples of 14 breast-tumor biopsies, one portion serving as untreated control, the other treated with O.C.T. There was no statistically significant difference between these two groups. We then compared these data with those of historical controls analyzed both in the presence and absence of sodium molybdate (10 mmol/L). Eighty breast-tumor specimens (mean +/- SD patients' ages, 59 +/- 14 y) embedded in O.C.T. compound and analyzed without molybdate gave ER and PR values that differed insignificantly from those for 306 samples (patients' ages, 61 +/- 14 y) untreated with O.C.T. Thirty-nine specimens (patients' ages, 58 +/- 15 y) embedded in O.C.T. compound were analyzed in the presence of molybdate and compared with the results for 288 specimens (patients' ages, 61 +/- 14 y) untreated with O.C.T. Again, there was an insignificant difference in the concentrations and affinities of receptors in the two groups. Evidently O.C.T. compound does not alter the receptor status of tumor biopsies.

Influence of O.C.T. embedding compound on determinations of estrogen and progestin receptors in breast cancer

Estrogen receptor (ER) and progestin receptor (PR) concentrations in tumor biopsies are important predictive indicators of a clinical response to endocrine therapy of breast cancer. To assess interference of O.C.T. (optimum cutting temperature) embedding compound in assays of ER and PR by radioligand binding, we determined specific binding capacities and affinities of ER and PR in cytosols by a multipoint titration method, using split samples of 14 breast-tumor biopsies, one portion serving as untreated control, the other treated with O.C.T. There was no statistically significant difference between these two groups. We then compared these data with those of historical controls analyzed both in the presence and absence of sodium molybdate (10 mmol/L). Eighty breast-tumor specimens (mean +/- SD patients' ages, 59 +/- 14 y) embedded in O.C.T. compound and analyzed without molybdate gave ER and PR values that differed insignificantly from those for 306 samples (patients' ages, 61 +/- 14 y) untreated with O.C.T. Thirty-nine specimens (patients' ages, 58 +/- 15 y) embedded in O.C.T. compound were analyzed in the presence of molybdate and compared with the results for 288 specimens (patients' ages, 61 +/- 14 y) untreated with O.C.T. Again, there was an insignificant difference in the concentrations and affinities of receptors in the two groups. Evidently O.C.T. compound does not alter the receptor status of tumor biopsies.

Separation of two molecular forms of human estrogen receptor by hydrophobic interaction chromatography. Gradient optimization and tissue comparison

High-performance hydrophobic interaction chromatography (HPHIC) was used to separate and characterize two molecular forms of estrogen receptor with a SynChropak propyl hydrophobic column (300 A pore size). The linear gradient utilized earlier with a polyether-bonded column (2 to 0 M) ammonium sulfate in 40 min, gave poor resolution with the propyl column. However, resolution was maximized with either an initial ammonium sulfate concentration of 1 M (40-min gradient) or with a two-phase gradient (2 to 0.5 M in 10 min, 0.5 to 0 M in 30 min). This indicated that the propyl column was more hydrophobic than the polyether column. Estrogen receptor separated into two isoforms, either in the presence [MI, retention time (tR) = 13-14 min; MII, tR = 20-21 min] or absence (I, tR = 21-23 min; II, tR = 31-33 min) of the estrogen receptor stabilizing reagent, sodium molybdate. Similar isoforms were observed in cytosols from human breast tumors, uterus, and MCF-7 breast cancer cells. Unlike others, MCF-7 estrogen receptor did not show MI. Since MCF-7 cells contain 90,000 dalton heat shock proteins (HSP-90), HSP-90 is probably not directly involved in MI formation. Sodium molybdate selectively interacted with isoform II and converted it to MI. All isoforms appeared to be high-molecular-weight proteins (greater than 60 A) when subsequently analyzed by high-performance size-exclusion chromatography. Interestingly, when estrogen receptor was immobilized on the stationary phase, no change was detected in either hydrophobicity or steroid-binding capacity. After 16-18 h, immobilized receptor was eluted with a slightly longer tR. During incubation on the column, component MI was converted into I and/or II. HPHIC appears to be a rapid, yet gentle procedure for isolating large receptor complexes in significant quantities with high recoveries. This allows one to discern the complicated structure-function relationships of estrogen receptor and associated non-receptor proteins and provides information about the on-column behavior of complex proteins.

Correlation of estrogen, progesterone, and androgen receptors in breast cancer

Breast cancer was induced in female Holtzman rats by intragastric administration of 7,12-dimethylbenz[a]antracene (DMBA). At tumor maturity, biopsies of viable tissue were obtained, frozen, and then assayed for estrogen, progesterone, and androgen receptor content. By simple linear regression analysis, progesterone receptor levels significantly correlated with both estrogen and androgen receptor levels, whereas estrogen and androgen receptor levels did not correlate with each other. Multiple regression analyses further substantiated the predictive value of the progesterone receptor for the other two hormone receptors. Knowledge of breast tumor androgen receptor levels may further enhance the value of the estrogen receptor and progesterone receptor in hormonal responsiveness. Further, the progesterone receptor may be the most sensitive of the steroid hormone receptors for selecting patients likely to respond to hormonal therapy.

Binding of 2-hydroxyestradiol and 4-hydroxyestradiol to estrogen receptors from human breast cancers

The binding of catechol estrogens, epoxyenones and methoxyestrogens was evaluated using estrogen receptors in cytosol prepared from human breast cancers. The relative affinity of 2-hydroxyestradiol, a metabolite formed in vitro from estradiol-17 beta by breast cancer cells, was indistinguishable from that of estradiol-17 beta. 4-Hydroxyestradiol, which is also a metabolite of estradiol-17 beta, associated with the estrogen receptor with a relative affinity approximately 1.5-fold greater than that of estradiol-17 beta. Epoxyenones and methoxyestrogens were weak competitors compared to the binding of estradiol-17 beta, exhibiting relative affinities 3% or less than the affinity of estradiol-17 beta. Sucrose density gradient centrifugation revealed that both 2- and 4-hydroxyestradiol inhibited the binding of estradiol-17 beta to both the 4S and 8S isoforms of the estrogen receptor in a competitive manner, with a Ki = 0.94 nM for 2-hydroxyestradiol and a Ki = 0.48 nM for 4-hydroxyestradiol. It can be concluded that these data demonstrate a specific receptor-mediated estrogenic action for both of these catechol estrogens.

Characteristics and distribution of receptors for [D-TRP6]-luteinizing hormone-releasing hormone, somatostatin, epidermal growth factor, and sex steroids in 500 biopsy samples of human breast cancer

Binding capacities and apparent dissociation constants of receptors for [D-Trp6]-luteinizing hormone-releasing hormone [( D-Trp6]-LH-RH), somatostatin (SS-14), epidermal growth factor (EGF), and estrogen and progesterone were determined in 500 breast cancer specimens using multipoint assays. Specific binding sites greater than 10 fmol/mg cytosol protein for estrogen were found in 408 carcinomas (81.6%), and for progesterone in 340 specimens (68%). High affinity EGF receptors were present in membrane preparations from 335 samples (67%). In 260 of 500 samples (52%), two classes of [D-Trp6]-LH-RH membrane receptor sites were also detected, one class showing high affinity and low capacity, and the other class showing low affinity and high capacity; 178 biopsy samples (35.6%) exhibited binding sites for SS-14. Statistically significant inverse correlations were found between the binding capacities of estrogen and EGF receptors as well as between Bmax of progesterone and EGF receptors. Significant positive correlations were demonstrated between binding capacities of estrogen and progesterone and between Bmax of high affinity and low affinity binding sites of [D-Trp6]-LH-RH receptors. However, no correlation was found between the dissociation constants of different receptor sites in human breast cancer specimens. These results demonstrate that numerous human breast cancers, in addition to receptors for estrogen and progesterone, also show binding sites for EGF, [D-Trp6]-LH-RH and SS-14. The methods described herein permit a routine quantification of receptor sites for [D-Trp6]-LH-RH, SS-14, and EGF in membrane preparations of biopsy samples of breast cancer and can be used in conjunction with the determination of estrogen and progesterone receptors in nuclear-cytosolic extracts. The simultaneous measurements using a microanalytic approach allow the determination of peptide and steroid hormone receptors that might be involved in the response mechanisms of human breast cancer. It should be possible to correlate the levels of these receptors with clinical parameters to better identify endocrine-responsive neoplasms. This approach might be useful to guide a rational hormonal therapy in women with breast cancer.

Lability of steroid hormone receptors following devascularization of breast tumors

Ischemia may invalidate hormone-receptor analyses. This study determined the effects of progressive ischemia on steroid hormone-receptor analyses. Breast cancer was induced in 50- to 60-day-old female Holtzman rats by intragastric administration of 25 mg of 7,12-dimethylbenz[a]anthracene. After 90 days, rats were anesthetized and breast tumors were devascularized in vivo. At 0, 30, 60, 90 and 150 minutes, a biopsy specimen from each tumor was taken and rapidly frozen. Steroid binding capacity for estrogen (ER), progesterone (PR), and androgen (AR) receptors was determined by incubation with tracer receptor ligand. Ischemia decreased ER and AR levels by 30 minutes, whereas PR levels were unchanged through 150 minutes of ischemia. Following mastectomy, tylectomy, or breast biopsy, PR may be the most reliable of the hormone receptors for determining endocrine-responsive breast cancer. However, for accurate determination of all hormone receptors, specimens should be frozen in liquid nitrogen immediately, then preserved at -70 degrees C, or processed immediately.

High-performance hydrophobic interaction chromatography as a means of identifying estrogen receptors expressing different binding domains

Methodology for high-performance hydrophobic interaction chromatography (HPHIC) of estrogen receptors (ER) was developed, utilizing a polyether-bonded stationary phase, which was non-ionic in nature. Using a descending salt gradient (2 M to 0 M ammonium sulphate in 40 min), ERs from human breast cancer separated into two isoforms, which retained ligand-binding domains. The same isoforms were observed with ER preparations from rat uterus. When sodium molybdate, a stabilizer of receptor structure, was incorporated into the mobile phase, it altered the ER characteristics, producing an earlier elution of one component, while the other one remained unchanged. Treatment of breast cancer cytosol with RNase A did not alter ER elution from either the hydrophobic or size-exclusion (TSK 3000 SW) columns. Modification of cysteine residues with N-ethylmaleimide led to a broad elution pattern of receptor from the hydrophobic column, implying the existence of multiple conformations of ER. Limited trypsin treatment of ER, which removes the DNA binding domain, led to the elution of only one receptor peak from the hydrophobic column. The receptor eluted at 24 min both in the presence and in the absence of sodium molybdate. Thus, at least one mechanism of the sodium molybdate effect must involve its direct interaction with ER to influence the sequence between the DNA-binding domain and the N-terminus. This also indicates that the most hydrophobic species of ER (sodium molybdate sensitive) may arise due to the interaction of the DNA-binding site with the stationary phase. Other possibilities, such as differential post-translational modifications of the receptor protein could also account for the two isoforms of ER, observed in HPHIC analysis.

Influence of column length and pore size on high-performance ion-exchange chromatography of estrogen and progestin receptors

A high-performance liquid chromatographic (HPLC) procedure has been evaluated to establish a routine test in the clinical laboratory for measuring the profiles of estrogen and progestin receptor isoforms in human breast and endometrial tumors. This procedure will be used to determine if there is a relationship between particular isoform profiles and response to various endocrine therapies. Evaluation of various HPLC modes has shown that high-performance ion-exchange chromatography (HPIEC) with silica-based anion exchangers offers a promising approach. In this paper, we have compared HPIEC columns of different lengths (10 and 25 cm) and pore sizes (300, 500 and 1,000 A) in order to obtain an optimal separation procedure. Because of receptor lability, all investigations were performed at 4 degrees C. The mobile phase consisted of 10-500 mM phosphate buffer, supplemented with the stabilizing agent, sodium molybdate at pH 7.4. Recoveries from each of the columns were between 70-100%. The length of the column did not influence significantly the retention time and salt concentration required for elution of receptor proteins. However, pore sizes appeared to alter these parameters. With a larger pore size (1,000 A), the retention of proteins was lower (elution with 50 mM phosphate) than that observed with the 500-A pore size column (elution with 100 mM phosphate) or of the 300-A pore size column (elution with 150 mM phosphate). Based solely on recovery patterns and peak shape, we conclude that separation of receptor isoforms on a 1,000-A, 25-cm column is best suited for clinical analysis.

High-resolution separation of molybdate-stabilized progestin receptors using high-performance liquid chromatography

Molecular heterogeneity of the human uterine progestin receptor was investigated employing sucrose density gradient centrifugation and high-performance liquid chromatography (HPLC) in size-exclusion (HPSEC), ion-exchange (HPIEC) and chromatofocusing (HPCF) modes. Synthetic progestomimetic ligands, [3H]R5020 and [3H]ORG-2058, were used to identify these receptors. Rapid centrifugation with a vertical tube rotor showed both 8-9 S and 4-5 S receptor species in the presence of 10 mM sodium molybdate with a 90-96% recovery. [3H]R5020 displayed greater nonspecific binding than [3H]ORG-2058. When separated receptor preparations were labeled, each with a different ligand, mixed and separated on optimized gradients, at least two receptor isoforms were identified in the components sedimenting at 8-9 S. HPSEC confirmed the presence of receptor isoforms displaying different molecular size and shape dependent upon the progestin ligand used. When the surface charge properties were examined by HPIEC using AX-1000, two distinct species were observed irrespective of the radioactive ligand. The first peak appeared in the void volume similar to the position of free steroid, indicating the possibility of ligand stripping by the column. The second peak bound steroid specifically and eluted with 100 mM phosphate. If either 8-S or 4-S progestin receptors were first separated by gradient centrifugation then by HPIEC, both receptor isoforms eluted with 60 mM phosphate. Re-chromatography of these on HPIEC also gave the isoform eluting at 60 mM phosphate. HPCF of ligand-bound receptors on AX-500 columns also identified one isoform eluting at pH 5.6-6.1. Using a combination of HPLC techniques and sucrose gradient centrifugation, heterogeneity of the progestin receptor has been demonstrated.

High-performance hydrophobic interaction chromatography of estrogen receptors and magnesium dependent protein kinase(s): detection of two molecular forms of estrogen receptors in the presence and absence of sodium molybdate

The separation characteristics of estrogen receptors (ER) from human breast cancer were evaluated based on their hydrophobic properties. Results show that (1) two distinct hydrophobic isoforms of ER exist either in the presence of sodium molybdate (peaks MI and MII with retention times of 15-17 min and 24-26 min) or in its absence (peaks I and II with retention times of 25-27 min and 34-36 min respectively); (2) this is observed whether molybdate (MoO2-4) is added to prepared cytosol or to the buffer prior to homogenization; (3) isoform MII and I separated with similar retention times suggesting they are the same ER species; and (4) isoform MI (Rt = 15-17 min) is a distinct ER species from either MII/I (Rt = 25-28 min) or II (Rt = 34-36 min). The latter isoform represents a highly hydrophobic species seen only in the absence of MoO2-4. Finally, (5) MoO2-4 ions appear to interconvert the most hydrophobic species (II) into the least hydrophobic isoform (MI) with virtually no change in the quantity of isoform(s) MII/I. However, it cannot be ascertained if the II----MI interconversion proceeds via isoform MII/I. Isoform II may result from the interaction with the stationary phase via its DNA binding site since MoO2-4, which is suggested to directly interact with this site, selectively interacts with peak II. These results imply the usefulness of inclusion of receptor stabilizing reagents in the mobile phase for preserving receptor integrity and in elucidating the interrelationships of ER isoforms and associated macromolecules.

Alterations in estrogen receptor isoforms in the mammary gland and uterus of the rat during differentiation

1. Estrogen receptors in lactating mammary glands and uteri of rats which were 10 and 19 days postpartum exhibited molecular heterogeneity based on their surface charge properties. 2. The polymorphism of estrogen receptors detected by high-performance ion exchange chromatography may be monitored in-line with a radioisotope detector. 3. Estrogen receptors from the mammary gland and uterus of rats at 10 days of lactation exhibited primarily two receptor isoforms eluting at 200-250 mM and 250-300 mM phosphate, whereas three ionic isoforms (eluting at 50-150, 200-250 and 325-375 mM phosphate) were found in the mammary glands of rats at 19 days of lactation. Similar changes in the profiles of estrogen receptor isoforms were observed in uterine cytosol preparations at each stage of postpartum differentiation. 4. The elution pattern of receptor-associated radioactivity was not altered by the addition of diisopropylphosphate, a potent inhibitor of trypsin-like proteases, either before, during or immediately after homogenization. This indicates that the differences observed in the receptor elution profile of 10 and 19 day postpartum lactating mammary glands were not due to artifactual proteolysis. 5. In summary, our data indicate that the differentiation stage of lactating mammary glands may dictate the final profile of receptor isoforms detected.

Characterization of estrogen receptors and associated protein kinase activity by high-performance hydrophobic-interaction chromatography

We have determined that high-performance hydrophobic-interaction chromatography (HPHIC) with weakly hydrophobic columns permit the rapid separation of the labile isoforms of estrogen receptor proteins. Previously we reported the use of the SynChrom propyl 500 column for HPHIC of steroid receptors. However, due to the strongly hydrophobic characteristics of the ligand, [125I]iodoestradiol-17 beta, and the receptor protein, organic solvent was required in the mobile phase for greater recovery of receptor proteins. Here, we report separation of steroid receptors from human breast tumors and rat uteri, using the Beckman CAA-HIC, a non-ionic polyether-bonded column, without the need for organic solvents and with virtually 100% recoveries. Receptors were extracted in 10 mM phosphate buffer (pH 7.4). Maximum resolution and separation were achieved when a descending salt gradient of ammonium sulfate in phosphate buffer (pH 7.4) was used (2-0 M in 30 min). Estrogen receptor (ER) was resolved into two isoforms with tR = 22 +/- 1 min (n = 16, designated as peak I) and 27.5 +/- 0.5 min (n = 14, designated as peak II) and a purification of five- to twenty-fold in a single pass. Free steroid was eluted at tR = 35 +/- 1 min (n = 4). Separation was dependent on adjusting the ionic strength of cytosol to 1.5 M ammonium sulfate. ER, purified by HPHIC, retained ligand binding capacity and exhibited protein kinase activity, which was dominant in the less hydrophobic peak I (tR = 22 min) when immunoprecipitated with the monoclonal antibody D547. This method of rapidly purifying ER with high retention of biological activity may now be applied to the study of the molecular interrelationships of steroid receptor isoforms.

Progestin receptors from tissues either exhibiting or lacking estrogen response mechanisms. Comparison of conventional and high-performance liquid chromatography methodology

Evidence from a variety of target organs has shown that progesterone receptor (PR) is induced by estrogen receptor (ER) in normal and neoplastic tissues. However, approximately 12% of the normal human uterine samples exhibit only PR with no measurable ER, suggesting the expression of both inducible and constitutive receptor isoforms. We investigated several molecular properties of PR from tissues either exhibiting or lacking ER. All studies were conducted in potassium phosphate buffer containing 10 mM sodium molybdate with a synthetic progestin, [3H]R5020 as the ligand. Radioinert R5020 was used as competitor to assess nonspecific association. Competition analysis showed that PR from both sources exhibited similar ligand specificities and affinities. Relative affinities were ORG 2058 greater than R5020 greater than medroxy-progesterone acetate greater than progesterone much greater than testosterone (Kd values ranged from 10(-9) to 10(-10) M; testosterone showed no specific competition). We utilized high-performance liquid chromatography in the size-exclusion (HPSEC) and ion-exchange (HPIEC) modes to probe the size and ionic properties of PR. HPSEC profiles showed that the PR isoform from both sources was eluted as a single, sharp peak greater than 75 A. HPIEC elution profiles indicated no differences in the surface ionic properties in that PR from both tissue types eluted with ca. 100 mM phosphate. These experiments show no difference between the inducible and the putative constitutive form of PR. Thus, some PR species may not require estrogen for their formation.

Assessment of estrogen receptor-monoclonal antibody interaction by high-performance liquid chromatography

High performance liquid chromatography (HPLC) was employed as a means of analyzing estrogen receptor (ER)-antibody recognition. This technique takes advantage of the fact that the majority of gamma-globulin-antigen complexes do not interact with the anion-exchange resins selected. A variety of monoclonal (MAb) and polyclonal antibodies (PAb) raised against ER and ER-associated proteins were assessed for their chromatographic behaviour after association with charged ER, based upon properties of size, shape, and surface charge. ER exhibits polymorphism, several isoforms being present in target cells. The monoclonal antibody H222Sp gamma demonstrated discrete specificity for the 150 mM ER isoform (normally eluting at 150 mM phosphate) from the high-performance ion-exchange chromatography column which was eluted unretained when complexed with antibody. However, the monoclonal reagent D547Sp gamma interacted directly with anion-exchange columns (SynChropak AX-1000 and Altex DEAE-5PW), complicating a clear evaluation of ER-MAb association. Only 50-60% of the 150 mM ER isoform was eluted at a lower salt concentration. Few conclusions could be drawn with respect to MAb interaction with the 50-60 mM ER isoform (normally eluting at 50-60 mM phosphate) since the antibody-receptor complex was also eluted at the same phosphate concentration. In addition, polyclonal and monoclonal antibodies to the ER and ER-associated proteins were assessed by HPLC. At present, heat shock proteins and protein kinase activity have been shown by other techniques to be associated with the ER. Size-exclusion resins, such as TSK 3000 SW, were employed in a fast method of determining ER isoform-antibody recognition. Thus, HPLC may be used to analyze soluble antibody-antigen interactions rapidly, with high recovery of biological activity.

The effects of ischemia on estrogen and progesterone receptor profiles in the rodent uterus

Ischemia is considered to invalidate the estrogen receptor (ER) and progesterone receptor (PR) values of tissues available for steroid hormonal analysis. To evaluate the temporal effect of devascularization on steroid receptors, complete uterine ischemia was induced in vivo in 64 female Buffalo rats (80-154 g). Animals were assigned to varying intervals of ischemia (0-90 min) and were maintained at a constant ambient (75 degrees F) and core-body temperature (100-102 degrees F). Following tissue preservation at -80 degrees C, multipoint titration of steroid binding capacity (SBC) was performed with [3H]estradiol 17-beta (3-0.15 nM) or [3H] R5020 (8-0.4 nM) in the presence or absence of a 200-fold excess of an unlabeled ligand. Applying nonlinear regression analysis, ischemia was observed to decrease the binding capacitance for both ER and PR profiles of rodent uterine tissues at 30 min with significant decay over the 90-min interval of devascularization (ER, P less than 0.01; PR, P less than 0.1). Significant reduction in SBC was evident after 80 min of ischemia for PR (P less than 0.05) and 90 min of tissue ischemia for ER (P less than 0.05) comparative to control (t0) valves. The detrimental effect of progressive ischemia on ER and PR values was such that it appears essential to assure rapid and reliable tissue aliquot preservation techniques when organ ischemia greater than or equal to 90 min is anticipated.

Molybdate and the molecular properties of the vervet monkey estrogen receptor

The Vervet monkey (Cercopithecus aethiops pygerythrus) uterine estrogen receptor was partially characterised. The effect of the molybdate oxyanion on various molecular properties of the receptor was investigated. Molybdate appeared to affect the subunit structure and apparent heterogeneity of the receptor. Anion exchange chromatography of uterine cytosols yielded two ligand binding subunits in a 1:1 ratio in the absence of sodium molybdate, while only a single labelled complex could be demonstrated in cytosols prepared in molybdate containing buffers. Chromatofocussing of the nonstabilized cytosols revealed substantial receptor heterogeneity (7 peaks) while a much simpler pattern (2 peaks) could be observed in the presence of the molybdate. Likewise, iso-electric focussing of labelled cytosols on agarose gels yielded at least 3 high affinity binding components (pI:6.8, 6.2, 5.9) in the absence and only one major band in the presence of sodium molybdate (pI 5.9).

HPLC analysis of estrogen receptor by a multidimensional approach

Previously we demonstrated the polymorphism of estrogen receptors (ER) in cytosol of various tissues based upon properties of size, shape and surface charge. This study describes the application of a multidimensional approach utilizing HPLC for characterization of ER. Cytosols from human uterus and endometrial carcinomas were characterized sequentially by high performance size exclusion chromatography (HPSEC) on Spherogel TSK-3000 SW, and high performance ion-exchange chromatography (HPIEC) using SynChropak AX-1000 anion exchange columns. Using HPSEC, specific estrogen binding was exhibited by a 30 A isoform and by one appearing after the V0 (approximately 60 A) in human uterus. However, in endometrial carcinoma other smaller binding components with Stoke's radii of less than 20 A were observed also. In buffers containing 400 mM KCl, predominantly a 28-30 A species was observed by HPSEC. Further characterization of the 28-30 A isoform from low and high salt elution from HPSEC was accomplished with an AX-1000 column. With either condition, 2 forms were eluted on HPIEC, 1 in the column wash (retention time 8-9 min), and the other at 50-70 mM phosphate. The elution profile of the larger species (approximately 60 A by HPSEC) on the ion-exchange column was time dependent. Immediate analysis (within 15 min) showed a profile similar to that of the original cytosol which contained minor components eluting in wash buffer and at 50-70 mM phosphate and a major isoform at 180 mM phosphate. However delayed analysis (after 2 h) of the 60 A isoform showed a similar profile (components in buffer wash and at 50-70 mM phosphate) obtained with the 30 A species. This time dependent change was not observed for the 30 A species or for the original cytosol. Estrogen receptors in cytosol sedimented at 10S and 4S in low ionic strength gradients and at 4S in sucrose gradients containing 400 mM KCl. The 28-30 A and 60 A species recovered from HPSEC sedimented at 3.5S. This multidimensional approach indicates that native estrogen receptors dissociated into a number of smaller molecular isoforms, which were distinguishable by different surface charge properties.

Interaction of estrogen receptor isoforms with immobilized monoclonal antibodies

High-performance liquid chromatography was performed to separate the various isoforms of estrogen receptor from human breast cancer, based on size (high-performance size-exclusion chromatography) and surface charge (high-performance ion-exchange chromatography) properties. The ability of these isoforms to interact with the monoclonal antibodies was assessed. All isoforms exhibited similar immunodeterminant sites, but when they are bound to [125I]iodoestradiol-17 beta (IE), only 30% binding of the radioactive complex to the immobilized monoclonal antibodies was observed. However, the mass of the receptor recognized by the antibody bead, via the estrogen receptor-enzyme immunoassay (ER-EIA), was always significantly higher. This was true for both fractionated and non-fractionated cytosols, suggesting that non-ligand binding forms, such as precursors and products of the estrogen receptor, were also recognized; or the ligand was only selecting for a particular conformer(s); or the monoclonal antibody on the bead recognized other proteins associated with estrogen receptor. Ion-exchange fractionation of unlabeled receptor showed loss of immunodeterminant sites. However, size-exclusion fractionation did not show this effect. Diethylstilbestrol, a competitor of IE binding, showed marked stability of receptor recognized by ER-EIA during both size-exclusion and ion-exchange chromatography. Limited trypsin treatment of the receptor caused the loss of immunodeterminant sites without altering the ligand binding sites. Thus, proteolysis of estrogen receptors in cytosols of human breast cancer could easily lead to underestimation by ER-EIA. Although the components with immunodeterminant sites recognized by ER-EIA were always eluted with the ligand-binding isoforms of the estrogen receptor, our data suggest that the concentration of the protein having the epitope associated with the monoclonal antibody is unequal to that recognized by the steroid ligand. We conclude that application of ER-EIA to clinical assays of estrogen receptors clearly needs further clarification.