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Membrane estrogen signaling enhances tumorigenesis and metastatic potential of breast cancer cells via estrogen receptor-?36 (ER?36).

ABSTRACT: Protein kinase C (PKC) signaling can be activated rapidly by 17?-estradiol (E(2)) via nontraditional signaling in ER?-positive MCF7 and ER?-negative HCC38 breast cancer cells and is associated with tumorigenicity. Additionally, E(2) has been shown to elicit anti-apoptotic effects in cancer cells counteracting pro-apoptotic effects of chemotherapeutics. Supporting evidence suggests the existence of a membrane-associated ER that differs from the traditional receptors, ER? and ER?. Our aim was to identify the ER responsible for rapid PKC activation and to evaluate downstream effects, such as proliferation, apoptosis, and metastasis. RT-PCR, Western blot, and immunofluorescence were used to determine the presence of ER splice variants in multiple cell lines. E(2) effects on PKC activity were measured with and without ER-blocking antibodies. Cell proliferation was determined by [(3)H]thymidine incorporation, and cell viability was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, (MTT) whereas apoptosis was determined by DNA fragmentation and TUNEL. Quantitative RT-PCR and sandwich ELISA were used to determine the effects on metastatic factors. The role of membrane-dependent signaling in cancer cell invasiveness was examined using an in vitro assay. The results indicate the presence of an ER? splice variant, ER?36, in ER?-positive MCF7 and ER?-negative HCC38 breast cancer cells, which localized to plasma membranes and rapidly activated PKC in response to E(2), leading to deleterious effects such as enhancement of proliferation, protection against apoptosis, and enhancement of metastatic factors. These findings propose ER?36 as a novel target for the development of therapies that can prevent progression of breast cancer in the primary tumor as well as during metastasis.

SUBMITTER: Chaudhri RA

PROVIDER: S-EPMC3293594 | biostudies-literature | 2012 Mar

REPOSITORIES: biostudies-literature

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Membrane estrogen signaling enhances tumorigenesis and metastatic potential of breast cancer cells via estrogen receptor-α36 (ERα36).

Chaudhri Reyhaan A RA Olivares-Navarrete Rene R Cuenca Natalia N Hadadi Agreen A Boyan Barbara D BD Schwartz Zvi Z

The Journal of biological chemistry 20120113 10

Protein kinase C (PKC) signaling can be activated rapidly by 17β-estradiol (E(2)) via nontraditional signaling in ERα-positive MCF7 and ERα-negative HCC38 breast cancer cells and is associated with tumorigenicity. Additionally, E(2) has been shown to elicit anti-apoptotic effects in cancer cells counteracting pro-apoptotic effects of chemotherapeutics. Supporting evidence suggests the existence of a membrane-associated ER that differs from the traditional receptors, ERα and ERβ. Our aim was to i ...[more]

PMID: 22247547

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Project description:BackgroundEstrogen receptor-? (ER?)-negative breast cancer is clinically aggressive and normally does not respond to conventional estrogen target-directed therapies. The soybean isoflavone, genistein (GE), has been shown to prevent and inhibit breast cancer and recent studies have suggested that GE can enhance the anticancer capacity of an estrogen antagonist, tamoxifen (TAM), especially in ER?-positive breast cancer cells. However, the role of GE in ER?-negative breast cancer remains unknown.MethodsWe have evaluated the in vitro and in vivo epigenetic effects of GE on ER? reactivation by using MTT assay, real-time reverse transcription-polymerase chain reaction (RT-PCR) assay, western-blot assay, immunoprecipitation (ChIP) assay, immunohistochemistry and epigenetic enzymatic activity analysis. Preclinical mouse models including xenograft and spontaneous breast cancer mouse models were used to test the efficacy of GE in vivo.ResultsWe found that GE can reactivate ER? expression and this effect was synergistically enhanced when combined with a histone deacetylase (HDAC) inhibitor, trichostatin A (TSA), in ER?-negative MDA-MB-231 breast cancer cells. GE treatment also re-sensitized ER?-dependent cellular responses to activator 17?-estradiol (E2) and antagonist TAM. Further studies revealed that GE can lead to remodeling of the chromatin structure in the ER? promoter thereby contributing to ER? reactivation. Consistently, dietary GE significantly prevented cancer development and reduced the growth of ER?-negative mouse breast tumors. Dietary GE further enhanced TAM-induced anti-cancer efficacy due at least in part to epigenetic ER? reactivation.ConclusionsOur studies suggest that soybean genistein can epigenetically restore ER? expression, which in turn increases TAM-dependent anti-estrogen therapeutic sensitivity in vitro and in vivo. The results from our studies reveal a novel therapeutic combination approach using bioactive soybean product and anti-hormone therapy in refractory ER?-negative breast cancer which will provide more effective options in breast cancer therapy.

Project description:Limited knowledge of the changes in estrogen receptor (ER) signaling during the transformation of the normal mammary gland to breast cancer hinders the development of effective prevention and treatment strategies. Differences in estrogen signaling between normal human primary breast epithelial cells and primary breast tumors obtained immediately following surgical excision were explored. Transcriptional profiling of normal ER+ mature luminal mammary epithelial cells and ER+ breast tumors revealed significant difference in the response to estrogen stimulation. Consistent with these differences in gene expression, the normal and tumor ER cistromes were distinct and sufficient to segregate normal breast tissues from breast tumors. The selective enrichment of the DNA binding motif GRHL2 in the breast cancer-specific ER cistrome suggests that it may play a role in the differential function of ER in breast cancer. Depletion of GRHL2 resulted in altered ER binding and differential transcriptional responses to estrogen stimulation. Furthermore, GRHL2 was demonstrated to be essential for estrogen-stimulated proliferation of ER+ breast cancer cells. DLC1 was also identified as an estrogen-induced tumor suppressor in the normal mammary gland with decreased expression in breast cancer. In clinical cohorts, loss of DLC1 and gain of GRHL2 expression are associated with breast cancer and are independently predictive for worse survival. This study suggests that normal ER signaling is lost and tumor-specific ER signaling is gained during breast tumorigenesis. Unraveling these changes in ER signaling during breast cancer progression should aid the development of more effective prevention strategies and targeted therapeutics. SIGNIFICANCE STATEMENT: Abnormal estrogen receptor (ER) signaling drives the majority of breast cancers and is targeted by endocrine therapies. However, in normal breast tissue, ER signaling has been demonstrated to promote benign functions such as development and differentiation. Using genomic techniques to characterize ER function in normal breast and breast tumors, this study reveals differential patterns of ER signaling, suggesting that normal ER signaling is lost and tumorigenic ER signaling gained during breast tumor formation. Better understanding of this process can aid the development of improved breast cancer prevention strategies and therapies.

Dataset Information

Membrane estrogen signaling enhances tumorigenesis and metastatic potential of breast cancer cells via estrogen receptor-?36 (ER?36).

Publications

Membrane estrogen signaling enhances tumorigenesis and metastatic potential of breast cancer cells via estrogen receptor-α36 (ERα36).

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