Diana Marquez

Estrogen and growth factor receptor interactions in human breast and non-small cell lung cancer cells.

Extranuclear estrogen receptors may mediate rapid effects of estradiol that communicate with nuclear receptors and contribute to proliferation of human cancers bearing these signaling proteins. To assess these growth-promoting pathways, we undertook controlled homogenization and fractionation of NIH-H23 non-small cell lung cancer cells. As many breast tumors, NIH-H23 cells express estrogen receptors (ER), with the bulk of specific estradiol binding in nuclear fractions. However, as in breast cells, a significant portion of specific, high-affinity estradiol-17beta binding-sites are also enriched in plasma membranes of lung tumor cells. These estrogen binding-sites co-purify with plasma membrane-marker enzymes and are not significantly contaminated by cytosol or nuclei. On further purification of membrane caveolae from lung tumor cells, proteins recognized by monoclonal antibodies to nuclear ER-alpha and to ER-beta were identified in close association with EGF receptor in caveolae. In parallel studies, ER-alpha and ER-beta are also detected in nuclear and extranuclear sites in archival human breast and lung tumor samples and are noted to occur in clusters at the cell membrane by using confocal microscopy to visualize fluorescent-labeled monoclonal antibodies to ER-alpha. Data on site-directed mutagenesis of cysteine-447 in ER-alpha suggest that association of ER forms with membrane sites may depend on acylation of cysteine by palmitate. Estrogen-induced growth of MCF-7 breast cancer and NIH-H23 lung cancer cells in vitro correlated closely with acute hormonal activation of mitogen-activated protein kinase signaling and was significantly reduced by treatment with Faslodex, a pure anti-estrogen. Further, combination of Faslodex with selected growth factor receptor inhibitors elicited a more pronounced inhibiton of tumor cell growth. Thus, extranuclear forms of ER play a role in promoting downstream signaling for hormone-mediated proliferation and survival of breast, as well as lung, cancers and offer a new target for anti-tumor therapy.

Membrane-associated binding sites for estrogen contribute to growth regulation of human breast cancer cells

Membrane-associated binding sites for estrogen may mediate rapid effects of estradiol-17β that contribute to proliferation of human breast cancers. After controlled homogenization and fractionation of MCF-7 breast cancer cells, the bulk of specific estradiol binding is found in nuclear fractions. However, a significant portion of specific, high-affinity estradiol-17β binding-sites are also enriched in plasma membranes. These estradiol binding-sites co-purify with 5′-nucleotidase, a plasma membrane-marker enzyme, and are free from major contamination by cytosol or nuclei. Electrophoresis of membrane fractions allowed detection of a primary 67-kDa protein and a secondary 46-kDa protein recognized by estradiol-17β and by a monoclonal antibody directed to the ligand-binding domain of the nuclear form of estrogen receptor. Estrogen-induced growth of MCF-7 breast cancer cells in vitro was blocked by treatment with the antibody to estrogen receptor and correlated closely with acute hormonal activation of mitogen-activated protein kinase and Akt kinase signaling. Estrogen-promoted growth of human breast cancer xenografts in nude mice was also significantly reduced by treatment in vivo with the estrogen receptor antibody. Thus, membrane-associated forms of estrogen receptor may play a role in promoting intracellular signaling for hormone-mediated proliferation and survival of breast cancers and offer a new target for antitumor therapy.

Aromatase Expression Predicts Survival in Women with Early-Stage Non-Small Cell Lung Cancer

Estrogen signaling is critical in the progression of tumors that bear estrogen receptors. In most patients with breast cancer, inhibitors that block interactions of estrogen with its receptors or suppress the production of endogenous estrogens are important interventions in the clinic. Recent evidence now suggests that estrogen also contributes to the pathogenesis of non-small cell lung cancer (NSCLC). We used a human lung cancer xenograph model system to analyze the effect of aromatase or estradiol on tumor growth. We further examined the level of protein expression of aromatase in 422 patients with NSCLC using a high-density tissue microarray. Results were confirmed and validated on an independent patient cohort (n = 337). Lower levels of aromatase predicted a greater chance of survival in women 65 years and older. Within this population, the prognostic value of aromatase was greatest in earlier stage lung cancer (stage I/II). In addition, for women with no history of smoking, lower aromatase levels were a strong predictor of survival. Our findings implicate aromatase as an early-stage predictor of survival in some women with NSCLC. We predict that women whose lung cancers have higher levels of aromatase might be good candidates for targeted treatment with aromatase inhibitors.

Estrogen receptors in membrane lipid rafts and signal transduction in breast cancer.

Regulation of breast cancer growth by estrogen is mediated by estrogen receptors (ER) in nuclear and extranuclear compartments. We assessed the structure and functions of extranuclear ER that initiate downstream signaling to the nucleus. ER, including full-length 66-kDa ER and a 46-kDa ER splice variant, are enriched in lipid rafts from MCF-7 cells with (MCF-7/HER-2) or without (MCF-7/PAR) HER-2 gene overexpression and co-localize with HER-1 and HER-2 growth factor receptors, as well as with lipid raft marker flotillin-2. In contrast, ER-negative MCF-7 cells do not express nuclear or lipid raft ER. ER knockdown with siRNA also elicits a marked loss of ER in MCF-7 cell rafts. In MCF-7/PAR cells, estrogen enhances ER association with membrane rafts and induces rapid phosphorylation of nuclear receptor coactivator AIB1, actions not detected in ER-negative cells. Thus, nuclear and lipid raft ER derive from the same transcript, and extranuclear ER co-localizes with HER receptors in membrane signaling domains that modulate downstream nuclear events leading to cell growth.

Epidermal growth factor receptor and tyrosine phosphorylation of estrogen receptor

Activation of estrogen receptor-α (ERα) by growth factors in the absence of estrogen is a well-documented phenomenon. To study further this process of ligand-independent receptor activation, COS-7 cells without ER were transfected with both ER and epidermal growth factor receptor (EGFR). In the absence of estrogen, epidermal growth factor (EGF) stimulated rapid tyrosine phosphorylation of ER in transfected COS-7 cells. Similarly, in MCF-7 breast cancer cells that have natural expression of ER and EGFR, EGF promoted acute phosphorylation of serine and tyrosine residues in ER, and a direct interaction between ER and EGFR after treatment with EGF was found. In confirmation of a direct interaction between ER and EGFR, activation of affinity-purified EGFR tyrosine kinase in vitro stimulated the phosphorylation of recombinant ER. The cross-communication between EGFR and ER appears to promote significant stimulation of cell proliferation and a reduction in the apoptotic loss of those cells that express both receptor signaling pathways. However, COS-7 cells transfected with both ER and EGFR show minimal stimulation of classical estrogen response element (ERE)-dependent transcriptional activity after stimulation by EGF ligand. This suggests that the proliferative and antiapoptotic activity of EGF-induced ER activation may be dissociated from ERE-dependent transcriptional activity of the ER.

Expression levels of estrogen receptor beta in conjunction with aromatase predict survival in non-small cell lung cancer

Estrogen signaling pathways may play a significant role in the pathogenesis of non-small cell lung cancers (NSCLC) as evidenced by the expression of aromatase and estrogen receptors (ERα and ERβ) in many of these tumors. Here we examine whether ERα and ERβ levels in conjunction with aromatase define patient groups with respect to survival outcomes and possible treatment regimens. Immunohistochemistry was performed on a high-density tissue microarray with resulting data and clinical information available for 377 patients. Patients were subdivided by gender, age and tumor histology, and survival data was determined using the Cox proportional hazards model and Kaplan-Meier curves. Neither ERα nor ERβ alone was predictor of survival in NSCLC. However, when coupled with aromatase expression, higher ERβ levels predicted worse survival in patients whose tumors expressed higher levels of aromatase. Although this finding was present in patients of both genders, it was especially pronounced in women ≥ 65 years old, where higher expression of both ERβ and aromatase indicated a markedly worse survival rate than that determined by aromatase alone. Expression of ERβ together with aromatase has predictive value for survival in different gender and age subgroups of NSCLC patients. This predictive value is stronger than each individual marker alone. Our results suggest treatment with aromatase inhibitors alone or combined with estrogen receptor modulators may be of benefit in some subpopulations of these patients.

Abstract 903: Expression of estrogen receptor beta together with aromatase predicts survival in non-small cell lung cancer

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL Lung cancer continues to be the leading cause of cancer mortality. There is increasing evidence suggesting estrogens and estrogen signaling play a significant role in lung cancer pathophysiology. Estrogen receptors (ER) alpha and beta are expressed in normal lung and many non-small cell lung cancers. Previously we found that in women 65 years and older with non-small cell lung cancer (NSCLC), higher aromatase levels in tumor cells conferred a worse prognosis for survival. Here we examine whether ER alpha and ER beta levels in conjunction with aromatase can further define different patient groups with respect to survival outcomes and possible treatment regimens. Methods: Immunohistochemistry was performed on a high-density tissue microarray with marker data and clinical information available for 378 patients. Patients were subcategorized by gender, age, smoking status and tumor histology. Survival data was determined using the Cox proportional hazards model and Kaplan-Meier curves. Results: Unlike aromatase, neither ER alpha nor ER beta alone were predictors of survival in NSCLC patients or any subset of these patients examined. However, when coupled with aromatase expression, higher ER beta levels predicted poorer survival in those patients whose tumors expressed higher levels of aromatase. Although this survival difference was present in patients of both genders, it was more pronounced in women > 65 years old, where higher expression of both ER beta and aromatase showed a markedly worse survival rate than that determined by aromatase alone. Conclusion: Combined expression of ER beta with aromatase has predictive value for survival in different gender and age subgroups of NSCLC patients. This predictive value is stronger than each individual marker alone. These results suggest that possibly treatment with aromatase inhibitors alone or combined with estrogen receptor modulators may have benefit in some subpopulations of NSCLC patients. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 903. doi:10.1158/1538-7445.AM2011-903

Abstract 5000: Tolerogenic transcription regulator Foxp3 controls the expression of immunosuppressive cytokines in melanoma cells

Foxp3 is a critical transcription regulator that is found commonly expressed in a subset of immunosuppressive CD4+/CD25+ T cells characterized as regulatory T cells (Tregs) in the immune system. Foxp3 is a member of the forkhead/winged-helix family of transcriptional regulators exhibiting both, activation and repression of transcription. Foxp3 is critically important for the development and function of Tregs and the consequent definition of immune-tolerance. Ectopic Foxp3 expression has been shown to -phenotypically and functionally- convert T cells to Tregs. Recently, we have characterized the expression of Foxp3 in a variety of human and mouse cancerous cells, either in tissue or in cultured cell lines. Although of cardinal importance, the specific role and mechanisms involved in the Foxp3-mediated immunosuppressive activity remains elusive. Thus, we hypothesize that tumor-derived Foxp3 is controlling the transcriptional expression of immunosuppressive cytokines by tumor cells and inducing immunotolerance in the tumor microenvironment. We have tested this hypothesis by interrogating the well-characterized B16-C57BL/6 syngeneic mouse model of melanoma. Foxp3-expressing B16-F0 cells (B16-Foxp3+) where specifically and stably knockdown for Foxp3 expression by lentivirus-mediated shRNA (B16-Foxp3-). In order to determine the specific role and mechanisms of melanoma-derived Foxp3 in controlling the expression of immunosuppressive cytokines generated by melanoma cells, we have evaluated the differential cytokine expression profile between the B16Foxp3+ and the B16-Foxp3- cultured cells using Multiplex Bead Immunoassay, Immunoblotting Assay of Proteins and Semiquantitative RT-PCR. Our results demonstrated that the suppression of expression of Foxp3 in melanoma cells showed a significant downregulation of a selected group of immunosuppressive cytokines, in particular IL-4, IL-6, IL-10, IL-12, TNF-alpha and GM-CSF. In contrast, Foxp3 did not have an appreciable effect on the expression of IL-1, IL-2, IL-5, and IFN-gamma. Altogether, our data suggest the specific role of tumor-derived expression of FOXP3 in the control of the expression of tolerogenic/immunosuppressive cytokines secreted by melanoma cells to the tumor microenvironment. Furthermore, selective suppression of Foxp3 expression and/or activity in cancerous cells may help to develop better and more effective targeted immunotherapy as treatment for malignant melanoma. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5000. doi:10.1158/1538-7445.AM2011-5000