Monoclonal antibody identification and characterization of a Mr 43,000 membrane glycoprotein associated with human breast cancer

A monoclonal antibody (323/A3) with a high degree of selectivity for binding to breast cancer cells was produced by immunization of mice with MCF-7 human breast cancer cells. The antigen recognized by 323/A3 on MCF-7 appears to be surface localized, and by enzyme-linked immunosorbent assay, the antibody was found to bind strongly with four of six breast cancer cell lines examined while no binding was detectable with nonbreast cancer cell lines. In vivo distribution of the 323/A3 antigen was screened by immunoperoxidase staining of formalin-fixed paraffin sections of normal human tissues and tumors. Among breast tissues, positive staining was detected with 75% (6 of 8) of metastatic lymph nodes, 59% (76 of 128) of primary breast tumors, 20% (13 of 63) of benign breast lesions, and 0% (0 of 10) of normal breast. No immunostaining was detected with a large variety and number of other normal human tissues with the exception of staining observed with epithelium of normal colon. Antigen distribution appears not to be disease specific, since positive staining was also observed with adenocarcinomas other than breast. The antigen recognized by the 323/A3 antibody was identified by Western blot analysis as a Mr 43,000 protein. The glycoprotein nature of the antigen was demonstrated by its binding to concanavalin A, specific elution with sugar, and immunoprecipitation of a Mr 43,000 radiolabeled protein from extracts of MCF-7 cells after pulse labeling with [3H]glucosamine. The 323/A3 antigen appears to be the same Mr 43,000 protein in cell lines as in breast tumors in vivo. Based on a comparison with the molecular weights of other known tumor-associated antigens and with their immunocytochemical tissue distribution, the Mr 43,000 glycoprotein described here represents a tumor-associated antigen previously undescribed in breast cancer or in other tumors. Since the Mr 43,000 glycoprotein is present on the surface of most breast cancer cells and is either absent or expressed at very low levels in most normal tissues including normal breast, the monoclonal antibody described here may have potential applications in diagnosis and management of breast cancer.     

Association between high concentrations of Mr 52,000 cathepsin D and poor prognosis in primary human breast cancer

The Mr 52,000 cathepsin D is the precursor of a lysosomal protease secreted in excess by breast cancer cells. This protease can degrade extracellular matrices and proteoglycans and is induced by estrogens in estrogen receptor-positive breast cancer cell lines. In a 4- to 6-yr retrospective cohort study, the concentration of the total cathepsin D (precursor plus intermediate and mature chains) was assayed in cytosols of primary tumors from 242 pre/perimenopausal and 154 postmenopausal breast cancer patients in a solid-phase immunoassay using two specific monoclonal antibodies. Patients were initially divided into groups with low, intermediate, or high concentrations of cathepsin D corresponding to the quartiles of the overall distribution. Using these groupings, the level of Mr 52,000 cathepsin D was not significantly associated with the recognized prognostic factors of age, lymph node involvement, tumor size, and/or grade of anaplasia. A significant association was found between cathepsin D concentrations and estrogen receptor status only among pre/perimenopausal patients. Receptor-positive tumors (greater than or equal to 10 fmol of estrogen receptor/mg of cytosol protein) had a significantly greater proportion of patients with high Mr 52,000 cathepsin D concentrations. Patients with high Mr 52,000 cathepsin D concentrations (greater than 78 pmol/mg for pre/perimenopausal and greater than 24 for postmenopausal patients) have shorter recurrence-free survival (P = 0.06 for pre/peri- and P = 0.039 for postmenopausal patients) and have a trend toward shorter overall survival (P = 0.30 and P = 0.089 for pre/peri- and postmenopausal groups, respectively). In multivariate analysis, Mr 52,000 cathepsin D status was found to be an independent prognostic factor for recurrence-free survival of about the same import as lymph node status for both menopausal groups. This first retrospective study demonstrates that the level of Mr 52,000 cathepsin D in cytosol of primary breast cancer biopsies is an independent prognostic factor in predicting relapses in both pre/peri- and postmenopausal patients.     

Nucleolar accumulation of cyclic adenosine 3':5'-monophosphate receptor proteins during regression of MCF-7 human breast tumor

Cyclic adenosine 3':5'-monophosphate (cAMP) receptor proteins (high-affinity binding proteins) present in growing and regressing MCF-7 human breast tumors were identified and characterized by the use of the photoaffinity-labeled 8-azido[32P]-cAMP and the affinity-purified antibodies to type I and type II regulatory subunits (RI and RII, respectively) of cAMP-dependent protein kinase. The cytosol fraction of growing MCF-7 tumors contained four major types of the 8-azido[32P]cAMP-binding proteins with molecular weights of 35,000, 47,000, 50,000, and 52,000. Following estrogen withdrawal, the amount of these proteins increased in the cytosol of regressing tumors. RI antibody immunoprecipitated cAMP receptor protein with a molecular weight of 47,000, whereas RII antibody immunoprecipitated Mr 50,000 and 52,000 proteins. The Mr 35,000 protein was not precipitated by either RI or RII antibodies. In the nuclear extracts of the growing tumors, the 8-azido-[32P]cAMP-binding proteins with molecular weights of 34,000, 35,000, 44,000, and 47,000 were detected. Following estrogen withdrawal, the 8-azido[32P]cAMP-binding proteins with molecular weights of 50,000 and 52,000 newly appeared in the nuclei of regressing tumors. The Mr 47,000 protein was immunoprecipitated by RI antibody and the Mr 34,000, 44,000, 50,000, and 52,000 proteins were precipitated by RII antibody. An indirect immunofluorescence revealed that, during regression of MCF-7 tumors, the intensity of immunofluorescence of RII proteins dramatically increased in the nucleoli, whereas immunofluorescence of RI remained the same in the nuclei. These results suggest that, during hormone-induced regression of human breast tumors, the Mr 50,000 and Mr 52,000 RII cAMP-binding proteins are translocated to the nucleoli from cytoplasm. Thus, the accumulation of these cAMP receptor proteins at nucleolar site(s) correlates with the regression of MCF-7 tumors.     

Tamoxifen treatment increases the concentration of 52K-cathepsin D and its precursor in breast cancer tissue

The pro-cathepsin D of Mr 52,000 is regulated by estrogens via the estrogen receptor (RE) and is secreted by breast cancer cells in vitro. In an attempt to predict the hormone responsiveness of breast cancer in vivo, we have assayed total 52K cathepsin D and its precursor in the primary breast cancer cytosol of 36 patients treated before surgery with 30 mg of tamoxifen daily for 1 to 5 weeks (average, 3 weeks). Compared to a similar control population, total 52K cathepsin D was increased by tamoxifen (P = 0.02) but less so than its precursor (P less than 0.001). Furthermore, 45% of the RE-positive tumors from tamoxifen-treated patients had a higher cathepsin D precursor concentration than the same type of tumor from control patients, or than RE-negative tumors from tamoxifen-treated patients. This 3-week challenge test was probably too short to avoid partial estrogenic activity of tamoxifen (flare) and the authors infer that longer time of treatment would decrease rather than increase the concentration of cathepsin D in the RE-responsive tumors. However, two cancers from patients with relapses after prolonged tamoxifen treatment (greater than 6 months) also had high concentrations of 52K cathepsin D and its precursor. The authors conclude that the concentration of cathepsin D and its precursor in breast cancer cytosol can be increased by short-term tamoxifen treatment, suggesting that these tumors are estrogen responsive.     

Vitamin E succinate (VES) induces Fas sensitivity in human breast cancer cells: role for Mr 43,000 Fas in VES-triggered apoptosis

Fas (CD95/APO-1) is an important mediator of apoptosis. We show that Fas-resistant MCF-7, MDA-MB-231, and MDA-MB-435 human breast cancer cells become responsive to anti-Fas (CD95) agonistic antibody-triggered apoptosis after pretreatment or cotreatment with vitamin E succinate (VES; RRR-alpha-tocopheryl succinate). In contrast, no enhancement of anti-Fas agonistic antibody-triggered apoptosis was observed following VES pretreatment or cotreatment with Fas-sensitive primary cultures of human mammary epithelial cells, immortalized MCF-10A cells, or T47D human breast cancer cells. Although VES is itself a potent apoptotic triggering agent, the 6-h pretreatment procedure for Fas sensitization did not initiate VES-mediated apoptosis. The combination of VES plus anti-Fas in pretreatment protocols was synergistic, inducing 2.8-, 3.0-, and 6.3-fold enhanced apoptosis in Fas-resistant MCF-7, MDA-MB-231, and MDA-MB-435 cells, respectively. Likewise, cotreatment of Fas-resistant MCF-7, MDA-MB-231, and MDA-MB-435 cells with VES plus anti-Fas enhanced apoptosis 1.9-, 2.0-, and 2.6-fold, respectively. Functional knockout of Fas-mediated signaling with either Fas-neutralizing antibody (MCF-7-, MDA-MB-231-, and MDA-MB-435-treated cells) or Fas antisense oligomers (MDA-MB-435-treated cells only), reduced VES-triggered apoptosis by approximately 50%. Analyses of whole cell extracts from Fas-sensitive cells revealed high constitutive expression of Mr 43,000 Fas, whereas Fas-resistant cells expressed low levels that were confined to the cytosolic fraction. VES treatment of the Fas-resistant cells caused a depletion of cytosolic Mr 43,000 Fas with a concomitant increase in Mr 43,000 membrane Fas. These data show that VES can convert Fas-resistant human breast cancer cells to a Fas-sensitive phenotype, perhaps by translocation of cytosolic Mr 43,000 Fas to the membrane and show that VES-mediated apoptosis involves Mr 43,000 Fas signaling.     

Distribution of the Mr 52,000 estrogen-regulated protein in benign breast diseases and other tissues by immunohistochemistry

A secreted glycoprotein with a molecular weight of 52,000 is induced by estrogen in breast cancer cells and has been purified to prepare monoclonal antibodies. The protein has been detected in some breast cancers but not in normal breast and uterus. In order to study its potential value as a marker, we have tested by immunohistochemistry frozen sections of several normal and malignant tissues and of benign mastopathies. Among different tissues tested, the Mr 52,000 protein was detected only in liver, sweat glands, and some sebaceous glands, and in malignant melanomas and some breast tumors. Other estrogen-responsive tissues (ovary, placenta, endometrium, etc.) gave negative results. Immunoradiometric assay of the Mr 52,000 protein in biological fluid revealed an elevated concentration in cyst fluid (0.5 to 7.4 micrograms/ml), pleural effusions of certain metastatic breast cancer, and sweat. By immunohistochemistry, the Mr 52,000 antigen was also detected in 42% of 129 benign mastopathies. Gynecomastia, fibrous disease, fibroadenoma, and adenosis were mainly negative, whereas ductal hyperplasia and cysts were positive. The Mr 52,000 protein was found mostly in proliferative ducts and in cysts but not in lobular hyperplasia and nonproliferative lesions without cyst. More Mr 52,000 protein was found in postmenopausal patients than in premenopausal patients. We conclude that the Mr 52,000 protein is a marker associated with mammary cysts and proliferative ducts. On the basis of the increased risk of breast cancer in proliferative mastopathies, we suggest that the Mr 52,000 protein is useful for predicting high-risk mastopathies acting as a marker associated with the proliferation of ductal tissue.     

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.     

Specific cytoplasmic alpha-fetoprotein binding protein in MCF-7 human breast cancer cells and primary breast cancer tissue

Summary Direct evidence was obtained for the existence of a specific high affinity alpha-fetoprotein (AFP)-binding protein in the cytosol of both MCF-7 human breast cancer cultured cells and primary breast cancer tissue from postmenopausal women using a nitrocellulose blotting assay. Scatchard analysis of the binding data for MCF-7 cells at 37° C revealed the presence of a single class of AFP binding sites with an apparent K_d of 4.5 × 10^–8 M, and 75,000 binding sites per cell. All 9 primary breast cancer cytosols obtained from postmenopausal women also contained measureable levels of this specific AFP-binding protein. The number of AFP molecules specifically bound varied considerably between patients and ranged from 29–250 fmol per mg cytosol protein. Levels of AFP-binding protein levels and estrogen receptor measured in these same breast cancer cytosols showed a positive statistical correlation (r = 0.85). Taken together, the present evidence for the existence of a specific cytoplasmic AFP-binding protein in MCF-7 cells and previously reported evidence forde novo synthesis of free immunoreactive and bound nonimmunoreactive forms of cytoplasmic AFP by MCF-7 cells is consistent with the conclusion that most of the endogenous AFP synthesized in breast cancer cells is rapidly bound to specific cytoplasmic AFP-receptors, and that binding of AFP to these receptors masks its immunoreactivity. The association of AFP synthesis with rapidly growing fetal liver and adult regenerating liver, germ-cell tumors, immature uterus, and breast cancer cells suggests that a positive correlation exists between cytoplasmic AFP-receptor levels and the proliferative capacity of malignant breast tumors, and therefore such measurements may provide useful therapeutic and/or prognostic information in individual patients.     

Phospho-serine-118 estrogen receptor-alpha expression is associated with better disease outcome in women treated with tamoxifen.

PURPOSE: The purpose of this research was to determine whether estrogen receptor alpha specifically phosphorylated at Ser(118) is associated with clinical outcome in primary breast tumors from estrogen receptor-positive and node-negative breast cancer patients. EXPERIMENTAL DESIGN: Estrogen receptor alpha specifically phosphorylated at Ser(118) was determined by immunohistochemistry in 117 primary breast tumors from node-negative patients who were subsequently treated with adjuvant tamoxifen. The relationship of estrogen receptor alpha specifically phosphorylated at Ser(118) expression to disease-free survival and overall survival was determined. RESULTS: Estrogen receptor alpha specifically phosphorylated at Ser(118) was limited to estrogen receptor alpha ligand binding assay-positive tumors and among this subset was expressed in 70 (62%) of these tumors. Estrogen receptor alpha specifically phosphorylated at Ser(118) expression was more frequently observed in progesterone receptor-positive tumors compared with progesterone receptor-negative tumors (chi(2) test, P = 0.012, n = 113). A significant correlation was also seen between estrogen receptor alpha specifically phosphorylated at Ser(118) and progesterone receptor levels (Spearman r = 0.236, P = 0.0118, n = 113). Kaplan-Meier outcome analysis showed that patients whose primary tumors expressed estrogen receptor alpha specifically phosphorylated at Ser(118) had a longer disease-free survival (P = 0.0018, n = 113) and a trend toward better overall survival, but this was not statistically significant. Among the subset of progesterone receptor-positive tumors, progesterone receptor-positive/estrogen receptor alpha specifically phosphorylated at Ser(118)-positive patients had a significantly longer disease-free survival that progesterone receptor-positive/estrogen receptor alpha specifically phosphorylated at Ser(118)-negative patients (P = 0.0041). CONCLUSIONS: Our data suggest that estrogen receptor alpha specifically phosphorylated at Ser(118) is a marker of a functional, intact ligand-dependent estrogen receptor signaling pathway in breast cancer and that estrogen receptor alpha specifically phosphorylated at Ser(118) status has the potential to provide a more precise biomarker of responsiveness to endocrine therapy in conjunction with estrogen receptor alpha and progesterone receptor status.     

Spontaneous conversion to estrogen receptor expression by the human breast epithelial cell line, MCF-10A

The human breast epithelial cell line, MCF-10A, derived from tissue from a woman undergoing a cutaneous mastectomy for fibrocystic breast disease, is negative for estrogen receptor expression, has undergone minimal genetic changes, retains many of the characteristics of normal breast epithelium and fails to exhibit growth in nude mice. When transfected with a functional copy of the estrogen receptor, both ER and MDM2 expression are negatively regulated by the presence of increasing concentrations of estradiol, as previously reported. We obtained the MCF-10A cell line from the American Type Culture Collection and confirmed that it was negative for ER expression. After approximately 20 passages under differing growth conditions, one subline was determined to be positive for ER expression. Growth of this ER-positive subline in phenol red-free media supplemented with charcoal-dextran stripped serum in the presence of nanomolar concentrations of estradiol failed to modulate ER and MDM2 expression, and induced expression of both pS2 and cathepsin D. Simultaneously with these observations, we observed that this subline, unlike the parent MCF-10A line, overexpressed P53 protein with a nuclear localization. Intermediate levels of the P53-inducible protein p21 WAF1/Cip1 were also detected in the ER-positive subline whereas levels of this protein in the parent subline were barely detectable, as measured by immunohistochemical methods. We conclude from these studies that ER expression and P53 alteration may constitute early steps in progression of malignant potential for breast cancer development.     

Adult human mesenchymal stem cells enhance breast tumorigenesis and promote hormone independence

Adult human mesenchymal stem cells (hMSCs) have been shown to home to sites of breast cancer and integrate into the tumor stroma. We demonstrate here the effect of hMSCs on primary breast tumor growth and the progression of these tumors to hormone independence. Co-injection of bone marrow-derived hMSCs enhances primary tumor growth of the estrogen receptor-positive, hormone-dependent breast carcinoma cell line MCF-7 in the presence or absence of estrogen in SCID/beige mice. We also show hormone-independent growth of MCF-7 cells when co-injected with hMSCs. These effects were found in conjunction with increased immunohistochemical staining of the progesterone receptor in the MCF-7/hMSC tumors as compared to MCF-7 control tumors. This increase in PgR expression indicates a link between MCF-7 cells and MSCs through ER-mediated signaling. Taken together, our data reveal the relationship between tumor microenvironment and tumor growth and the progression to hormone independence. This tumor stroma-cell interaction may provide a novel target for the treatment of estrogen receptor-positive, hormone-independent, and endocrine-resistant breast carcinoma.     

Loss of pigment epithelium-derived factor: a novel mechanism for the development of endocrine resistance in breast cancer

Introduction

Despite the benefits of endocrine therapies such as tamoxifen and aromatase inhibitors in treating estrogen receptor (ER) alpha-positive breast cancer, many tumors eventually become resistant. The molecular mechanisms governing resistance remain largely unknown. Pigment epithelium-derived factor (PEDF) is a multifunctional secreted glycoprotein that displays broad anti-tumor activity based on dual targeting of the tumor microenvironment (anti-angiogenic action) and the tumor cells (direct anti-tumor action). Recent studies indicate that PEDF expression is significantly reduced in several tumor types, including breast cancer, and that its reduction is associated with disease progression and poor patient outcome. In the current study, we investigated the role of PEDF in the development of endocrine resistance in breast cancer.

Methods

PEDF mRNA and protein levels were measured in several endocrine-resistant breast cancer cell lines including MCF-7:5C, MCF-7:2A, and BT474 and in endocrine-sensitive cell lines MCF-7, T47D, and ZR-75-1 using real-time PCR and western blot analyses. Tissue microarray analysis and immunohistochemistry were used to assess the PEDF protein level in tamoxifen-resistant breast tumors versus primary tumors. Lentiviruses were used to stably express PEDF in endocrine-resistant breast cancer cell lines to determine their sensitivity to tamoxifen following PEDF re-expression.

Results

We found that PEDF mRNA and protein levels were dramatically reduced in endocrine-resistant MCF-7:5C, MCF-7:2A, and BT474 breast cancer cells compared with endocrine-sensitive MCF-7, T47D, and ZR-75-1 cells, and that loss of PEDF was associated with enhanced expression of p^Ser167ERα and the receptor tyrosine kinase rearranged during transfection (RET). Importantly, we found that silencing endogenous PEDF in tamoxifen-sensitive MCF-7 and T47D breast cancer cells conferred tamoxifen resistance whereas re-expression of PEDF in endocrine-resistant MCF-7:5C and MCF-7:2A cells restored their sensitivity to tamoxifen in vitro and in vivo through suppression of RET. Lastly, tissue microarray studies revealed that PEDF protein was reduced in ~52.4% of recurrence tumors (31 out of 59 samples) and loss of PEDF was associated with disease progression and poor patient outcome.

Conclusion

Overall, these findings suggest that PEDF silencing might be a novel mechanism for the development of endocrine resistance in breast cancer and that PEDF expression might be a predictive marker of endocrine sensitivity.     

Prognostic significance of the metastasis-inducing protein S100A4 (p9Ka) in human breast cancer

The calcium-binding protein S100A4 is capable of inducing metastasis in rodent models for breast cancer. We now show that rabbit antibodies to recombinant rat S100A4 recognize specifically human S100A4 using Western blotting techniques and use them to assess the prognostic significance of S100A4 in primary tumors from a group of 349 patients treated between 1976 and 1982 for stage I and stage II breast cancer. The antibody stains normal breast tissue heterogeneously, but stains positively 41% of the carcinomas, leaving the remaining 59% as negatively stained. In addition to the carcinoma cells, some host stromal cells and lymphocytes are also stained, but these have been discounted in subsequent analyses. There is an association of staining of carcinomas for S100A4 with some tumor variables considered to be associated with poor prognosis for patients: tumor present in axillary lymph nodes (borderline P = 0.058), staining for c-erbB-3 (P = 0.002), cathepsin D (P = 0.024), and c-erbB-2 (P = 0.048). The association of staining for S100A4 with patient survival has been evaluated using life tables and analyzed using generalized Wilcoxon statistics. Eighty percent of the S100A4-negative patients but only 11% of the S100A4-positive patients are alive after 19 years of follow-up, and this association is highly significant (P < 0.0001); the former have a median survival of >228 months and the latter 47 months. The other tumor variables that show significant association with survival time are nodal status (P < 0.0001), tumor size (P = 0.0035), histological grade (P = 0.013), staining for c-erbB-2 (P = 0.0015), estrogen receptor (P = 0.028), and p53 (P = 0.032). Analysis of the association of patients with carcinomas staining for S100A4 and their survival in subgroups defined by these other tumor variables shows that in each subgroup, staining for S100A4 is associated with poorer survival. Patients whose tumors stain for S100A4 and possess involved lymph nodes (P < 0.0001), which are fixed to the chest wall (P = 0.015) or which stain for c-erbB-2 (P = 0.050), show a significant reduction in survival times over those with only S100A4-staining tumors. Patients with involved lymph nodes, or staining for c-erbB-2 in the S100A4-negative group fail to show any significant reduction in survival times. Multivariate regression analysis for 137 patients shows that staining for S100A4 is most highly correlated with patient deaths (P < 0.0001), but involved lymph nodes (P = 0.001), fixed tumors (P = 0.0002), and high histological grade (P = 0.022) are also significant independent prognostic variables. These results suggest that in this group of patients, the metastasis-inducing protein S100A4 is most tightly correlated with patient demise.     

High HSP90 expression is associated with decreased survival in breast cancer

The heat shock protein HSP90 chaperones proteins implicated in breast cancer progression, including Her2/neu. HSP90-targeting agents are in clinical trials for breast cancer. HSP90 expression is high in breast cancer cell lines, yet no large studies have been conducted on expression in human tumors and the association with clinical/pathologic variables. Tissue microarrays containing 10 cell lines and primary specimens from 655 patients with 10-year follow-up were assessed using our automated quantitative analysis (AQUA) method; we used cytokeratin to define pixels as breast cancer (tumor mask) within the array spot and measured HSP90 expression within the mask using Cy5-conjugated antibodies. We similarly assessed estrogen receptor, progesterone receptor, and Her2/neu expression. HSP90 expression was more variable in human tumors than in cell lines (P < 0.0001). High HSP90 expression was associated with decreased survival (P = 0.0024). On multivariable analysis, high HSP90 expression remained an independent prognostic marker. High HSP90 expression was associated with high Her2/neu and estrogen receptor, large tumors, high nuclear grade, and lymph node involvement. Although HSP90 levels were high in all our cell lines, expression in tumors was more variable. High HSP90 expression in primary breast cancer defines a population of patients with decreased survival. Evaluation of HSP90 expression in early-stage breast cancer may identify a subset of patients requiring more aggressive or pathway-targeted treatment. Prospective studies are needed to confirm the prognostic role of HSP90, as well as the predictive role of HSP90 expression in patients treated with HSP90 inhibitors.     

Novel senescence associated gene, YPEL3, is repressed by estrogen in ER+ mammary tumor cells and required for tamoxifen-induced cellular senescence

Estrogen signaling plays an important role in breast carcinogenesis. An increased understanding of estrogen gene targets and their effects will allow for more directed and effective therapies for individuals with breast cancer, particularly those with estrogen receptor positive tumors resistant to tamoxifen therapy. Here, we identify YPEL3 as a growth suppressive protein downregulated by estrogen in estrogen receptor positive breast cancer cell lines. Estrogen repression of YPEL3 expression was found to be independent of p53 but dependent on estrogen receptor alpha expression. Importantly, YPEL3 expression, which is induced by the removal of estrogen or treatment with tamoxifen triggers cellular senescence in MCF-7 cells while loss of YPEL3 increases the growth rate of MCF-7 cells. Taken together these findings suggest that YPEL3 may represent a potential target for directed hormonal therapy for estrogen receptor positive breast cancer patients.     

乳腺癌组织中PTEN和p27kip1蛋白的表达及其相互关系

目的:探讨PTEN和p27kip1在乳腺癌组织中的表达规律及其相互关系。方法:采用免疫组化SP法检测64例乳腺癌组织中PTEN和p27kip1蛋白的表达。结果:乳腺癌组织PTEN(34/64)和p27kip1(33/64)蛋白表达显著低于正常乳腺组织(15/15),P值分别为0·0082和0·0078。有腋淋巴结转移、远处转移及ER阴性组PTEN表达分别为13/33、3/11和16/38,明显低于无腋淋巴结转移(21/31)、无远处转移(31/53)和ER阳性组(18/26),P值分别为0·0240、0·0063和0·03475。p27kip1在乳腺癌有腋淋巴结转移、远处转移及ER阴性组的表达分别为7/33、2/11和8/38,明显低于无腋淋巴结转移(15/31)、无远处转移(20/53)和ER阳性组(14/26),P值分别为0·0230、0·0440和0·0071。两者表达均与肿瘤大小无关。两种蛋白表达水平具有显著的相关性,P=0·0041。结论:PTEN、p27kip1表达异常与乳腺癌转移及恶性程度密切相关,两种基因蛋白表达强度一致,显示其在乳腺癌演进中具有协同作用。     

HER-2/neu oncogene protein and prognosis in breast cancer

Amplification of the HER-2/neu oncogene was recently reported to predict poor clinical outcome in node-positive breast cancer patients. Since expression of the oncogene as its protein product might be even more closely related than gene amplification to disease progression, we have now examined levels of the HER-2/neu oncogene protein for its prognostic potential in both node-positive and node-negative breast cancer. Using Western blot analysis, levels of this protein were determined in 728 primary human breast tumor specimens. We examined relationships between this protein and other established markers of prognosis, as well as clinical outcome. In node-negative patients (n = 378), the HER-2/neu protein failed to predict disease outcome. However, in node-positive patients (n = 350), those patients with higher HER-2/neu protein had statistically shorter disease-free (P = .0014) and overall survival (P less than .0001) than patients with lower levels of the protein. Higher HER-2/neu protein was found in tumors without estrogen receptor (ER) (P = .02) or progesterone receptor (PgR) (P = .0003), and in patients with more than three positive lymph nodes (P = .04). A significant correlation between levels of the HER-2/neu gene protein and amplification of the gene itself was also found (n = 48, P less than .001). Multivariate analyses in these patients showed that the HER-2/neu protein is a significant independent predictor of both the disease-free and the overall survival in node-positive breast cancer, even when other prognostic factors are considered.