Androgen-induced human breast cancer cell proliferation is mediated by discrete mechanisms in estrogen receptor-alpha-positive and -negative breast cancer cells

Resveratrol and apoptosis

Resveratrol is a naturally occurring stilbene with desirable cardioprotective and anti-cancer properties. We have demonstrated the existence of a plasma membrane receptor for resveratrol near the arginine-glycine-aspartate (RGD) recognition site on integrin α(v)β₃ that is involved in stilbene-induced apoptosis of cancer cells. Resveratrol treatment in vitro causes activation and nuclear translocation of mitogen-activated protein kinase (ERK1/2), consequent phosphorylation of Ser-15 of p53, and apoptosis. An RGD peptide blocks these actions of resveratrol. By a PD98059-inhibitable process, resveratrol causes inducible COX-2 to accumulate in the nucleus where it complexes with pERK1/2 and p53. Chromatin immunoprecipitation reveals binding of nuclear COX-2 to promoters of certain p53-responsive genes, including PIG3 and Bax. NS-398, a specific pharmacologic inhibitor of COX-2, prevents resveratrol-induced complexing of nuclear ERK1/2 with COX-2 and with pSer-15-p53 and subsequent apoptosis; cyclooxygenase enzyme activity is not involved. Molecular steps in the pro-apoptotic action of resveratrol in cancer cells include induction of intranuclear COX-2 accumulation relevant to activation of p53. Epidermal growth factor, estrogen, and thyroid hormone act downstream of ERK1/2 to prevent resveratrol-induced apoptosis.

Androgen receptor expression and breast cancer survival in postmenopausal women

PURPOSE

Androgen receptor (AR) is commonly expressed in breast cancers. However, the association between tumor AR status and breast cancer survival is uncertain. Hence, we examined the association between AR status and breast cancer survival in the Nurses' Health Study (NHS).

EXPERIMENTAL DESIGN

It was a prospective study of postmenopausal women enrolled in the Nurses' Health Study with stage I to III breast cancer diagnosed between 1976 and 1997 and followed from the date of diagnosis until January 1, 2008 or death. Analyses were conducted using Kaplan-Meier methods and Cox proportional hazard models, to determine the association of AR status with survival outcomes adjusting for covariates.

RESULTS

Among 1467 breast cancers, 78.7% were AR-positive (AR+). Among 1,164 estrogen receptor (ER)-positive cases, 88.0% were AR+. AR positivity was associated with a significant reduction in breast cancer mortality (HR, 0.68; 95% CI, 0.47-0.99) and overall mortality (HR, 0.70; 95% CI, 0.53-0.91) after adjustment for covariates. In contrast, among women with ER-negative tumors (303 cases), 42.9% were AR+. There was a nonsignificant association between AR status and breast cancer death (HR, 1.59; 95% CI, 0.94-2.68).

CONCLUSIONS

The association of AR status and breast cancer survival is dependent on ER status. In particular, AR expression was associated with a more favorable prognosis among women with ER-positive tumors. Thus, determination of AR status may provide additional information on prognosis for postmenopausal women with breast cancer, and provide novel opportunities for targeted therapy.

Androgens regulate adenylate cyclase activity and intracellular calcium in stromal cells derived from human prostate

BACKGROUND

Increased smooth muscle tone is a significant component of benign prostatic hyperplasia, the onset of which correlates with age and declining serum testosterone levels. This study investigates the effects of androgens on key regulators of smooth muscle tone: intracellular calcium ([Ca(2+)](i)) and cyclic adenosine monophosphate (cAMP) in human cultured prostatic stromal cells (HCPSC).

METHODS

HCPSC were cultured in the absence or presence of dihydrotestosterone (DHT; 3, 30, and 300 nM) or testosterone (0.3-300 nM) alone or in the presence of flutamide (10 microM). Changes in [Ca(2+)](i) were determined in FURA-2AM (10 microM) loaded cells. Changes in cAMP were determined by Alpha Screen(R) assay.

RESULTS

Up to 32% of cultured cells exhibited spontaneous elevations of [Ca(2+)](i). The frequency of these elevations was reduced by nifedipine (10 microM), ryanodine (1 microM), and the adenylate cyclase inhibitor MDL 12,330A (20 microM). Compared to steroid-free cells, a 3-day incubation of cells with testosterone (only 3 nM) elevated basal, but not peak [Ca(2+)](i). In the presence of flutamide, all concentrations of testosterone tested elevated basal, but not peak [Ca(2+)](i). DHT (30 and 300, but not 3 nM) lowered peak and basal [Ca(2+)](i). Increased testosterone concentration dependently decreased resting cell cAMP (pIC(50): 7.64 +/- 0.29 nM).

CONCLUSIONS

These findings demonstrate that some HCPSC have the ability to spontaneously and transiently elevate [Ca(2+)](i). The magnitude of these [Ca(2+)](i) peaks, along with resting levels of calcium and cAMP, appear to be regulated by androgens.

Conjugated and non-conjugated androgens differentially modulate specific early gene transcription in breast cancer in a cell-specific manner

The role of androgen in breast cancer development is not fully understood, although androgen receptors (ARs) have been identified in breast cancer clinical samples and cell lines. However the whole spectrum of androgen actions cannot be accounted to the classic AR activation and the possible existence of a cell surface-AR has been suggested. Indeed, androgen, like all steroids, has been reported to trigger membrane-initiated signaling activity and exert specific actions, including ion channels and kinase signaling pathway activation, ultimately affecting gene expression. However, the molecular nature of membrane androgen sites represents another major persisting question. In the present study, we investigated early transcriptional effects of testosterone and the impermeable testosterone-BSA conjugate, in two breast cancer cell lines (T47D and MDA-MB-231), in an attempt to decipher specific genes modified in each case, providing evidences about specific membrane-initiating actions. Our data indicate that the two agents affect the expression of several genes. A group of genes were commonly affected while others were uniquely modified by each agent, including interaction with growth factors and K(+)-channels. In MDA-MB-231 cells, that are AR negative, the majority of genes affected by testosterone were also affected by testosterone-BSA indicating a membrane-initiated action. Subsequent analysis revealed that the two agents trigger different molecular pathways and cellular/molecular functions, suggestive of a molecular or functional heterogeneity of membrane and intracellular AR. In addition, the reported phenotypic interactions of membrane-acting androgen with growth factor were verified at the transcriptomic level, as well as their ion channel-modifying effects. Finally an interesting interplay between membrane-acting androgen with inflammation-related molecules, with potential clinical implications was revealed.

The normal breast microenvironment of premenopausal women differentially influences the behavior of breast cancer cells in vitro and in vivo

BACKGROUND

Breast cancer studies frequently focus on the role of the tumor microenvironment in the promotion of cancer; however, the influence of the normal breast microenvironment on cancer cells remains relatively unknown. To investigate the role of the normal breast microenvironment on breast cancer cell tumorigenicity, we examined whether extracellular matrix molecules (ECM) derived from premenopausal African-American (AA) or Caucasian-American (CAU) breast tissue would affect the tumorigenicity of cancer cells in vitro and in vivo. We chose these two populations because of the well documented predisposition of AA women to develop aggressive, highly metastatic breast cancer compared to CAU women.

METHODS

The effects of primary breast fibroblasts on tumorigenicity were analyzed via real-time PCR arrays and mouse xenograft models. Whole breast ECM was isolated, analyzed via zymography, and its effects on breast cancer cell aggressiveness were tested in vitro via soft agar and invasion assays, and in vivo via xenograft models. Breast ECM and hormone metabolites were analyzed via mass spectrometry.

RESULTS

Mouse mammary glands humanized with premenopausal CAU fibroblasts and injected with primary breast cancer cells developed significantly larger tumors compared to AA humanized glands. Examination of 164 ECM molecules and cytokines from CAU-derived fibroblasts demonstrated a differentially regulated set of ECM proteins and increased cytokine expression. Whole breast ECM was isolated; invasion and soft agar assays demonstrated that estrogen receptor (ER)-, progesterone receptor (PR)/PR- cells were significantly more aggressive when in contact with AA ECM, as were ER+/PR+ cells with CAU ECM. Using zymography, protease activity was comparatively upregulated in CAU ECM. In xenograft models, CAU ECM significantly increased the tumorigenicity of ER+/PR+ cells and enhanced metastases. Mass spectrometry analysis of ECM proteins showed that only 1,759 of approximately 8,000 identified were in common. In the AA dataset, proteins associated with breast cancer were primarily related to tumorigenesis/neoplasia, while CAU unique proteins were involved with growth/metastasis. Using a novel mass spectrometry method, 17 biologically active hormones were measured; estradiol, estriol and 2-methoxyestrone were significantly higher in CAU breast tissue.

CONCLUSIONS

This study details normal premenopausal breast tissue composition, delineates potential mechanisms for breast cancer development, and provides data for further investigation into the role of the microenvironment in cancer disparities.

Position paper: Rapid responses to steroids: current status and future prospects

Steroids exert their actions through several pathways. The classical genomic pathway, which involves binding of steroids to receptors and subsequent modulation of gene expression, is well characterized. Besides this, rapid actions of steroids have been shown to exist. Since 30 years, research on rapid actions of steroids is an emerging field of science. Today, rapid effects of steroids are well established, and are shown to exist for every type of steroid. The classical steroid receptors have been shown to be involved in rapid actions, but there is also strong evidence that unrelated structures mediate these rapid effects. Despite increasing knowledge about the mechanisms and structures which mediate these actions, there is still no unanimous acceptance of this category. This article briefly reviews the history of the field including current controversies and challenges. It is not meant as a broad review of literature, but should increase the awareness of the endocrinology society for rapid responses to steroids. As members of the organizing committee of the VI International Meeting on Rapid Responses to Steroid Hormones 2009, we propose a research agenda focusing on the identification of new receptoral structures and the identification of mechanisms of actions at physiological steroid concentrations. Additionally, efforts for the propagation of translational studies, which should finally lead to clinical benefit in the area of rapid steroid action research, should be intensified.

Translational implications of nongenomic actions of thyroid hormone initiated at its integrin receptor

A thyroid hormone receptor on integrin alphavbeta3 that mediates cell surface-initiated nongenomic actions of thyroid hormone on tumor cell proliferation and on angiogenesis has been described. Transduction of the hormone signal into these recently recognized proliferative effects is by extracellular-regulated kinases 1/2 (ERK1/2). Other nongenomic actions of the hormone may be transduced by phosphatidylinositol 3-kinase (PI3K) and are initiated in cytoplasm or at the cell surface. PI3K-mediated effects are important to angiogenesis or other recently appreciated cell functions but apparently not to tumor cell division. For those actions of thyroid hormone [L-thyroxine (T(4)) and 3,3'-5-triiodo-L-thyronine (T(3))] that begin at the integrin receptor, tetraiodothyroacetic acid (tetrac) is an inhibitor of and probe for the participation of the receptor in downstream intracellular events. In addition, tetrac has actions initiated at the integrin receptor that are unrelated to inhibition of the effects of T(4) and T(3) but do involve gene transcription in tumor cells. Discussed here are the implications of translating these nongenomic mechanisms of thyroid hormone analogs into clinical cancer cell biology, tumor-related angiogenesis, and modulation of angiogenesis that is not related to cancer.