Characterization of androgen receptor and nuclear receptor co-regulator expression in human breast cancer cell lines exhibiting differential regulation of kallikreins 2 and 3

Prognostic analyses of genes associated with anoikis in breast cancer

Breast cancer (BRCA) is the most diagnosed cancer worldwide and is responsible for the highest cancer-associated mortality among women. It is evident that anoikis resistance contributes to tumour cell metastasis, and this is the primary cause of treatment failure for BRCA. However, anoikis-related gene (ARG) expression profiles and their prognostic value in BRCA remain unclear. In this study, a prognostic model of ARGs based on The Cancer Genome Atlas (TCGA) database was established using a least absolute shrinkage and selection operator analysis to evaluate the prognostic value of ARGs in BRCA. The risk factor graph demonstrated that the low-risk group had longer survival than the high-risk group, implying that the prognostic model had a good performance. We identified 11 ARGs that exhibited differential expression between the two risk groups in TCGA and Gene Expression Omnibus databases. Through Gene Ontology and Kyoto Encyclopaedia of Genes and Genomes enrichment analyses, we revealed that the screened ARGs were associated with tumour progression and metastasis. In addition, a protein-protein interaction network showed potential interactions among these ARGs. Furthermore, gene set enrichment analysis suggested that the Notch and Wnt signalling pathways were overexpressed in the high-risk group, and gene set variation analysis revealed that 38 hallmark genes differed between the two groups. Moreover, Kaplan-Meier survival curves and receiver operating characteristic curves were used to identify five ARGs (CD24, KRT15, MIA, NDRG1, TP63), and quantitative polymerase chain reaction was employed to assess the differential expression of these ARGs. Univariate and multivariate Cox regression analyses were then performed for the key ARGs, with the best prediction of 3 year survival. In conclusion, ARGs might play a crucial role in tumour progression and serve as indicators of prognosis in BRCA.

Transcriptome profiling and proteomic validation reveals targets of the androgen receptor signaling in the BT-474 breast cancer cell line

BACKGROUND

Accumulating evidence suggests that the androgen receptor (AR) and its endogenous ligands influence disease progression in breast cancer (BCa). However, AR-mediated changes in BCa differ among the various BCa subtypes according to their hormone receptor profile [i.e., presence/absence of estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2, (HER2)]. Thus, we explored the androgen-regulated transcriptomic changes in the ER⁺PR⁺HER2⁺ BCa cell line, BT-474, and compared them with PR-mediated changes.

METHODS

We performed RNA sequencing analysis in treated BT-474 cells with dihydrotestosterone (DHT) and progesterone. Validation of the top ten differentially androgen-regulated genes and a number of other genes found in enriched signaling pathways was performed by qRT-PCR in BT-474 and other BCa cell lines. In addition, a parallel reaction monitoring targeted proteomic approach was developed to verify selected transcripts at the protein level.

RESULTS

In total 19,450 transcripts were detected, of which 224 were differentially regulated after DHT treatment. The increased expression of two well-known androgen-regulated genes, KLK2 (p < 0.05) and KLK3 (p < 0.001), confirmed the successful androgen stimulation in BT-474 cells. The transcription factor, ZBTB16, was the most highly upregulated gene, with ~ 1000-fold change (p < 0.001). Pathway enrichment analysis revealed downregulation of the DNA replication processes (p < 0.05) and upregulation of the androgen signaling and fatty acid metabolism pathways (p < 0.05). Changes related to progesterone treatment showed opposite effects in gene expression than DHT treatment. Similar expression profiles were observed among other BCa cell lines expressing high levels of AR (ZR75.1 and MBA-MB-453). The parallel reaction monitoring targeted proteomic analysis further confirmed that altered protein expression (KLK3, ALOX15B) in the supernatant and cell lysate of DHT-treated BT-474 cells, compared to control cells.

DISCUSSION

Our findings suggest that AR modulates the metabolism of BT-474 cells by affecting the expression of a large number of genes and proteins. Based on further pathway analysis, we suggest that androgen receptor acts as a tumor suppressor in the BT-474 cells.

Contraceptive progestins with androgenic properties stimulate breast epithelial cell proliferation

Hormonal contraception exposes women to synthetic progesterone receptor (PR) agonists, progestins, and transiently increases breast cancer risk. How progesterone and progestins affect the breast epithelium is poorly understood because we lack adequate models to study this. We hypothesized that individual progestins differentially affect breast epithelial cell proliferation and hence breast cancer risk. Using mouse mammary tissue ex vivo, we show that testosterone-related progestins induce the PR target and mediator of PR signaling-induced cell proliferation receptor activator of NF-κB ligand (Rankl), whereas progestins with anti-androgenic properties in reporter assays do not. We develop intraductal xenografts of human breast epithelial cells from 36 women, show they remain hormone-responsive and that progesterone and the androgenic progestins, desogestrel, gestodene, and levonorgestrel, promote proliferation but the anti-androgenic, chlormadinone, and cyproterone acetate, do not. Prolonged exposure to androgenic progestins elicits hyperproliferation with cytologic changes. Androgen receptor inhibition interferes with PR agonist- and levonorgestrel-induced RANKL expression and reduces levonorgestrel-driven cell proliferation. Thus, different progestins have distinct biological activities in the breast epithelium to be considered for more informed choices in hormonal contraception.

Co-Adjuvant Therapy Efficacy of Catechin and Procyanidin B2 with Docetaxel on Hormone-Related Cancers In Vitro

Prostate (PC) and breast cancer (BC) are heterogeneous hormonal cancers. Treatment resistance and adverse effects are the main limitations of conventional chemotherapy treatment. The use of sensitizing agents could improve the effectiveness of chemotherapeutic drugs as well as obviate these limitations. This study analyzes the effect of single catechin (CAT), procyanidin B2 (ProB2) treatment as well as the co-adjuvant treatment of each of these compounds with docetaxel (DOCE). We used PC- and BC-derived cell lines (PC3, DU-145, T47D, MCF-7 and MDA-MB-231). The short and long-term pro-apoptotic, anti-proliferative and anti-migratory effects were analyzed. RT-qPCR was used to discover molecular bases of the therapeutic efficacy of these compounds. ProB2 treatment induced a two- to five-fold increase in anti-proliferative and pro-apoptotic effects compared to single DOCE treatment, and also had a more sensitizing effect than DOCE on DU145 cells. Regarding BC cells, ProB2- and CAT-mediated sensitization to DOCE anti-proliferative and pro-apoptotic effects was cell-independent and cell-dependent, respectively. Combined treatment led to high-efficacy effects on MCF-7 cells, which were associated to the up-regulation of CDKN1A, BAX, caspase 9 and E-cadherin mRNA under combined treatment compared to single DOCE treatment. CAT and ProB2 can enhance the efficacy of DOCE therapy on PC and BC cells by the sensitizing mechanism.

Comparative metabolomics of MCF-7 breast cancer cells using different extraction solvents assessed by mass spectroscopy

Metabolic profiling of cancer cells can play a vital role in revealing the molecular bases of cancer development and progression. In this study, gas chromatography coupled with mass spectrometry (GC-MS) was employed for the determination of signatures found in ER+/PR+ breast cancer cells derived from MCF-7 using different extraction solvents including: A, formic acid in water; B, ammonium hydroxide in water; C, ethyl acetate; D, methanol: water (1:1, v/v); and E, acetonitrile: water (1:1, v/v). The greatest extraction rate and diversity of metabolites occurs with extraction solvents A and E. Extraction solvent D showed moderate extraction efficiency, whereas extraction solvent B and C showed inferior metabolite diversity. Metabolite set enrichment analysis (MSEA) results showed energy production pathways to be key in MCF-7 cell lines. This study showed that mass spectrometry could identify key metabolites associated with cancers. The highest enriched pathways were related to energy production as well as Warburg effect pathways, which may shed light on how energy metabolism has been hijacked to encourage tumour progression and eventually metastasis in breast cancer.

Androgen receptor: A promising therapeutic target in breast cancer

Breast cancer (BCa) is the second most common cancer worldwide and the most prevalent cancer in women. The majority of BCa cases are positive (+) for the estrogen receptor (ER⁺, 80%) and progesterone receptor (PR⁺, 65%). Estrogen and progesterone hormones are known to be involved in cancer progression, and thus hormonal deprivation is used as an effective treatment for ER⁺PR⁺ BCa subtypes. However, some ER⁺PR⁺ BCa patients develop resistance to such therapies. Meanwhile, chemotherapy is the only available treatment for ER^-PR^- BCa tumors. Another hormone receptor known as the androgen receptor (AR) has also been found to be widely expressed in human breast carcinomas. However, the mechanisms of AR and its endogenous androgen ligands is not well-understood in BCa and its biological role in this hormone-related disease remains unclear. In this review, we aim to address the importance of the AR in BCa diagnosis and prognosis, current AR-targeting approaches in BCa, and the potential for AR-downstream molecules to serve as therapeutic targets.

The Divergent Function of Androgen Receptor in Breast Cancer; Analysis of Steroid Mediators and Tumor Intracrinology

Androgen receptor (AR) is the most widely expressed steroid receptor protein in normal breast tissue and is detectable in approximately 90% of primary breast cancers and 75% of metastatic lesions. However, the role of AR in breast cancer development and progression is mired in controversy with evidence suggesting it can either inhibit or promote breast tumorigenesis. Studies have shown it to antagonize estrogen receptor alpha (ERα) DNA binding, thereby preventing pro-proliferative gene transcription; whilst others have demonstrated AR to take on the mantle of a pseudo ERα particularly in the setting of triple negative breast cancer. Evidence for a potentiating role of AR in the development of endocrine resistant breast cancer has also been mounting with reports associating high AR expression with poor response to endocrine treatment. The resurgence of interest into the function of AR in breast cancer has resulted in various emergent clinical trials evaluating anti-AR therapy and selective androgen receptor modulators in the treatment of advanced breast cancer. Trials have reported varied response rates dependent upon subtype with overall clinical benefit rates of ~19-29% for anti-androgen monotherapy, suggesting that with enhanced patient stratification AR could prove efficacious as a breast cancer therapy. Androgens and AR have been reported to facilitate tumor stemness in some cancers; a process which may be mediated through genomic or non-genomic actions of the AR, with the latter mechanism being relatively unexplored in breast cancer. Steroidogenic ligands of the AR are produced in females by the gonads and as sex-steroid precursors secreted from the adrenal glands. These androgens provide an abundant reservoir from which all estrogens are subsequently synthesized and their levels are undiminished in the event of standard hormonal therapeutic intervention in breast cancer. Steroid levels are known to be altered by lifestyle factors such as diet and exercise; understanding their potential role in dictating the function of AR in breast cancer development could therefore have wide-ranging effects in prevention and treatment of this disease. This review will outline the endogenous biochemical drivers of both genomic and non-genomic AR activation and how these may be modulated by current hormonal therapies.

Androgen Receptor Immunohistochemistry as a Companion Diagnostic Approach to Predict Clinical Response to Enzalutamide in Triple-Negative Breast Cancer

Purpose

The androgen receptor (AR) is increasingly recognized as a potential biomarker for identifying a subset of patients with possible hormonally driven triple-negative breast cancer (TNBC). However, its performance as a companion diagnostic remains elusive. Thus, we evaluated AR expression by immunohistochemistry in patients with advanced TNBC before treatment with the AR inhibitor enzalutamide.

Methods

We optimized and validated immunohistochemistry assays in breast and prostate cancer cell lines and tissues using two commercial AR monoclonal antibodies (SP107 and AR441). AR expression was then examined in patients with advanced TNBC enrolled in a phase II study of enzalutamide (ClinicalTrials.gov identifier: NCT01889238) on archived or fresh tissue before treatment. Association with clinical response was assessed by sensitivity, specificity, positive predictive value (PPV), drop-out rate, and survival.

Results

AR expression was detected in 80% and 63% of breast cancer tissue using SP107 and AR441, respectively. SP107 was selected for additional analyses because of its higher sensitivity and robustness. Total AR nuclear staining demonstrated the best accuracy in predicting clinical response (area under receiver operating characteristic curve, 0.72; P = .0001). At a threshold of 10%, 74.6% of patients were AR positive, leading to 30% PPV, 90% sensitivity, and 30% specificity. These patients showed a significantly higher median progression-free survival (hazard ratio, 0.56; 95% CI, 0.36 to 0.88; P = .011) and overall survival (hazard ratio, 0.54; 95% CI, 0.32 to 0.91; P = .019) compared with those with AR-negative (< 10%) TNBC.

Conclusion

At a threshold of ≥ 10% nuclear expression, the AR was associated with TNBC response to enzalutamide. However, the modest PPV may restrict its clinical application, and additional diagnostic tools may be helpful for improved patient selection.

Expression of the Transcriptional Coregulator FHL2 in Human Breast Cancer: A Clinicopathologic Study

OBJECTIVE

Although the Four and a Half LIM domain protein 2 (FHL2) has been suggested to play an important role in tumor development, this has not been investigated in breast cancer.

METHODS

Paraffin-embedded tissues from patients (n = 85) with primary breast cancer were submitted to immunohistochemical investigation of FHL2 expression and subsequent correlation with clinicopathologic parameters and patient survival.

RESULTS

The expression of FHL2 was confined to the cytoplasm of the tumor cells. Forty (47%) of 85 samples showed weak expression of FHL2, whereas high expression was found in 45 tumors (53%). A statistically significant positive correlation was observed between FHL2 and androgen receptor expression (P = .029). Patients with tumors expressing low amounts of FHL2 were characterized by a significantly better survival compared to those with high intratumoral FHL2 expression (P = .0215, log-rank test). The additional stratification according to adjuvant tamoxifen treatment revealed a significantly improved survival rate for patients receiving tamoxifen and being diagnosed with a tumor expressing high amounts of FHL2. This might indicate that tamoxifen is at least partially capable of reversing the negative prognostic impact of high FHL2 expression. Multivariate Cox regression analysis revealed FHL2 expression as a significant independent predictor of survival.

CONCLUSION

The specific expression in tumor tissue points to an important functional role of FHL2 in human breast cancer. Our survival data indicate that the expression of FHL2 in primary breast cancer is a potentially relevant prognostic factor. Further studies are warranted to elucidate whether analysis of FHL2 expression is suitable to predict response to antihormonal treatment with tamoxifen.

A molecular analysis provides novel insights into androgen receptor signalling in breast cancer

BACKGROUND

Androgen Receptor (AR) is an essential transcription factor for the development of secondary sex characteristics, spermatogenesis and carcinogenesis. Recently AR has been implicated in the development and progression of breast and prostate cancers. Although some of the functions of the AR are known but the mechanistic details of these divergent processes are still not clear. Therefore understanding the regulatory mechanisms of the functioning of the AR in ER-/AR+ breast cancer will provide many novel targets for the purpose of therapeutic intervention.

METHODS/RESULTS

Using bioinformatics tools, we have identified 75 AR targets having prominent roles in cell cycle, apoptosis and metabolism. Herein, we validated 10 genes as AR targets by studying the regulation of these genes in MDA-MB-453 cell line on stimulation by androgens like 5α-dihydrotestosterone (DHT), using RT-qPCR and ChIP assay. It was observed that all the identified genes involved in cell cycle except MAD1L1 were found to be up regulated whereas expression of apoptosis related genes was decreased in response to DHT treatment. We performed an exhaustive, rigid-body docking between individual ARE and DNA binding domain (DBD) of the AR protein and it was found that novel residues K567, K588, K591 and R592 are involved in the process of DNA binding. To verify these specific DNA-protein interactions electrostatic energy term calculations for each residue was determined using the linearized Poisson-Boltzmann equation. Our experimental data showed that treatment of breast cancer cells with DHT promotes cell proliferation and decreases apoptosis. It was observed that bicalutamide treatment was able to reverse the effect of DHT.

CONCLUSION

Taken together, our results provide new insights into the mechanism by which AR promotes breast cancer progression. Moreover our work proposes to use bicalutamide along with taxanes as novel therapy for the treatment of TNBCs, which are positive for downstream AR signalling.

Prolactin-induced protein is required for cell cycle progression in breast cancer

Prolactin-induced protein (PIP) is expressed in the majority of breast cancers and is used for the diagnostic evaluation of this disease as a characteristic biomarker; however, the molecular mechanisms of PIP function in breast cancer have remained largely unknown. In this study, we carried out a comprehensive investigation of PIP function using PIP silencing in a broad group of breast cancer cell lines, analysis of expression microarray data, proteomic analysis using mass spectrometry, and biomarker studies on breast tumors. We demonstrated that PIP is required for the progression through G1 phase, mitosis, and cytokinesis in luminal A, luminal B, and molecular apocrine breast cancer cells. In addition, PIP expression is associated with a transcriptional signature enriched with cell cycle genes and regulates key genes in this process including cyclin D1, cyclin B1, BUB1, and forkhead box M1 (FOXM1). It is notable that defects in mitotic transition and cytokinesis following PIP silencing are accompanied by an increase in aneuploidy of breast cancer cells. Importantly, we have identified novel PIP-binding partners in breast cancer and shown that PIP binds to β-tubulin and is necessary for microtubule polymerization. Furthermore, PIP interacts with actin-binding proteins including Arp2/3 and is needed for inside-out activation of integrin-β1 mediated through talin. This study suggests that PIP is required for cell cycle progression in breast cancer and provides a rationale for exploring PIP inhibition as a therapeutic approach in breast cancer that can potentially target microtubule polymerization.

Role of the androgen receptor in breast cancer and preclinical analysis of enzalutamide

Introduction

The androgen receptor (AR) is widely expressed in breast cancers and has been proposed as a therapeutic target in estrogen receptor alpha (ER) negative breast cancers that retain AR. However, controversy exists regarding the role of AR, particularly in ER + tumors. Enzalutamide, an AR inhibitor that impairs nuclear localization of AR, was used to elucidate the role of AR in preclinical models of ER positive and negative breast cancer.

Methods

We examined nuclear AR to ER protein ratios in primary breast cancers in relation to response to endocrine therapy. The effects of AR inhibition with enzalutamide were examined in vitro and in preclinical models of ER positive and negative breast cancer that express AR.

Results

In a cohort of 192 women with ER + breast cancers, a high ratio of AR:ER (≥2.0) indicated an over four fold increased risk for failure while on tamoxifen (HR = 4.43). The AR:ER ratio had an independent effect on risk for failure above ER % staining alone. AR:ER ratio is also an independent predictor of disease-free survival (HR = 4.04, 95% CI: 1.68, 9.69; p = 0.002) and disease specific survival (HR = 2.75, 95% CI: 1.11, 6.86; p = 0.03). Both enzalutamide and bicalutamide inhibited 5-alpha-dihydrotestosterone (DHT)-mediated proliferation of breast cancer lines in vitro; however, enzalutamide uniquely inhibited estradiol (E2)-mediated proliferation of ER+/AR + breast cancer cells. In MCF7 xenografts (ER+/AR+) enzalutamide inhibited E2-driven tumor growth as effectively as tamoxifen by decreasing proliferation. Enzalutamide also inhibited DHT- driven tumor growth in both ER positive (MCF7) and negative (MDA-MB-453) xenografts, but did so by increasing apoptosis.

Conclusions

AR to ER ratio may influence breast cancer response to traditional endocrine therapy. Enzalutamide elicits different effects on E2-mediated breast cancer cell proliferation than bicalutamide. This preclinical study supports the initiation of clinical studies evaluating enzalutamide for treatment of AR⁺ tumors regardless of ER status, since it blocks both androgen- and estrogen- mediated tumor growth.

Androgen receptor in triple negative breast cancer

The clinical management of triple negative breast cancer (TNBC) is challenging due to the relatively aggressive biological behaviour and paucity of specific targeted therapy. A subset of TNBC patients has been reported to express androgen receptor (AR) in carcinoma cells and the manipulation of androgen signalling or AR targeted therapies have been proposed. However, the biological significance of AR in TNBC has remained relatively unknown. Therefore, this review aims to summarise the reported studies assessing the rates of AR positivity in TNBC patients and androgenic effects in TNBC cell lines. The rates of AR positivity among TNBC cases varied depending on the study population (0-53% of all TNBC patients). This difference among the reported studies may be largely due to the methodological differences of analysing AR. While the majority of cell line studies suggest that androgen increase proliferation and preliminary clinical studies suggest that AR antagonists improve the prognosis of AR positive TNBC patients, cell line transfection experiments and survival analyses of histological samples suggest that the presence of AR in tumour is either benign or predicts better survival. Therefore further translational investigations regarding the mechanisms of androgen action in TNBC are required to explain this discrepancy between clinical and basic studies.

Significant alterations in the expression pattern of kallikrein-related peptidase genes KLK4, KLK5 and KLK14 after treatment of breast cancer cells with the chemotherapeutic agents epirubicin, docetaxel and methotrexate

Given that 1.3 million new cases of breast cancer are universally registered among women and approximately 36 % of the patients die annually, the revelation of new predictive markers for treatment efficiency is of vital importance. Recently, our group has depicted that KLK4, KLK5, and KLK14 are differentially expressed in breast carcinoma. The objective of this study was to determine and investigate the expression pattern of the KLK4, KLK5, and KLK14 genes in breast cancer cells after treatment with established chemotherapeutic agents. We evaluated these genes' expression after treatment of the BT-20 cells with epirubicin, docetaxel and methotrexate, determining their cytotoxic effect by MTT and trypan blue assays. The relative quantification of genes' mRNA levels was performed by using the SYBR Green® chemistry, and the HPRT1 served as an endogenous control gene. The drugs triggered apoptosis in treated cells and induced deregulations in the expression of the above KLKs. The most significant alterations were a 12-fold and tenfold increase of KLK5 in docetaxel and methotrexate-treated cells, respectively, while the KLK4 levels decreased by ten-fold in epirubicin, five-fold in docetaxel and twenty-fold in methotrexate treated-cells, compared to the untreated ones. In the case of KLK14 levels, a twofold increase in epirubicin and threefold decrease in methotrexate-treated cells were observed. Present significant alterations in the expression pattern of KLK4, KLK5, and KLK14 could comprise an initial stage for predicting chemotherapy response in breast cancer and should be further investigated as predictive markers in the future.

Elevated nuclear expression of the SMRT corepressor in breast cancer is associated with earlier tumor recurrence

Silencing mediator of retinoic acid and thyroid hormone receptor (SMRT), also known as nuclear corepressor 2 (NCOR2) is a transcriptional corepressor for multiple members of the nuclear receptor superfamily of transcription factors, including estrogen receptor-α (ERα). In the classical model of corepressor action, SMRT binds to antiestrogen-bound ERα at target promoters and represses ERα transcriptional activity and gene expression. Herein SMRT mRNA and protein expression was examined in a panel of 30 breast cancer cell lines. Expression of both parameters was found to vary considerably amongst lines and the correlation between protein and mRNA expression was very poor (R (2) = 0.0775). Therefore, SMRT protein levels were examined by immunohistochemical staining of a tissue microarray of 866 patients with stage I-II breast cancer. Nuclear and cytoplasmic SMRT were scored separately according to the Allred score. The majority of tumors (67 %) were negative for cytoplasmic SMRT, which when detected was found at very low levels. In contrast, nuclear SMRT was broadly detected. There was no significant difference in time to recurrence (TTR) according to SMRT expression levels in the ERα-positive tamoxifen-treated patients (P = 0.297) but the difference was significant in the untreated patients (P = 0.01). In multivariate analysis, ERα-positive tamoxifen-untreated patients with high nuclear SMRT expression (SMRT 5-8, i.e., 2nd to 4th quartile) had a shorter TTR (HR = 1.94, 95 % CI, 1.24-3.04; P = 0.004) while there was no association with SMRT expression for ERα-positive tamoxifen-treated patients. There was no association between SMRT expression and overall survival for patients, regardless of whether they received tamoxifen. Thus while SMRT protein expression was not predictive of outcome after antiestrogen therapy, it may have value in predicting tumor recurrence in patients not receiving adjuvant tamoxifen therapy.

Role of KCNMA1 in breast cancer

KCNMA1 encodes the α-subunit of the large conductance, voltage and Ca²⁺-activated (BK) potassium channel and has been reported as a target gene of genomic amplification at 10q22 in prostate cancer. To investigate the prevalence of the amplification in other human cancers, the copy number of KCNMA1 was analyzed by fluorescence-in-situ-hybridization (FISH) in 2,445 tumors across 118 different tumor types. Amplification of KCNMA1 was restricted to a small but distinct fraction of breast, ovarian and endometrial cancer with the highest prevalence in invasive ductal breast cancers and serous carcinoma of ovary and endometrium (3–7%). We performed an extensive analysis on breast cancer tissue microarrays (TMA) of 1,200 tumors linked to prognosis. KCNMA1 amplification was significantly associated with high tumor stage, high grade, high tumor cell proliferation, and poor prognosis. Immunofluorescence revealed moderate or strong KCNMA1 protein expression in 8 out of 9 human breast cancers and in the breast cancer cell line MFM223. KCNMA1-function in breast cancer cell lines was confirmed by whole-cell patch clamp recordings and proliferation assays, using siRNA-knockdown, BK channel activators such as 17ß-estradiol and the BK-channel blocker paxilline. Our findings revealed that enhanced expression of KCNMA1 correlates with and contributes to high proliferation rate and malignancy of breast cancer.

An androgen receptor mutation in the MDA-MB-453 cell line model of molecular apocrine breast cancer compromises receptor activity

Recent evidence indicates that the estrogen receptor-α-negative, androgen receptor (AR)-positive molecular apocrine subtype of breast cancer is driven by AR signaling. The MDA-MB-453 cell line is the prototypical model of this breast cancer subtype; its proliferation is stimulated by androgens such as 5α-dihydrotestosterone (DHT) but inhibited by the progestin medroxyprogesterone acetate (MPA) via AR-mediated mechanisms. We report here that the AR gene in MDA-MB-453 cells contains a G-T transversion in exon 7, resulting in a receptor variant with a glutamine to histidine substitution at amino acid 865 (Q865H) in the ligand binding domain. Compared with wild-type AR, the Q865H variant exhibited reduced sensitivity to DHT and MPA in transactivation assays in MDA-MB-453 and PC-3 cells but did not respond to non-androgenic ligands or receptor antagonists. Ligand binding, molecular modeling, mammalian two-hybrid and immunoblot assays revealed effects of the Q865H mutation on ligand dissociation, AR intramolecular interactions, and receptor stability. Microarray expression profiling demonstrated that DHT and MPA regulate distinct transcriptional programs in MDA-MB-453 cells. Gene Set Enrichment Analysis revealed that DHT- but not MPA-regulated genes were associated with estrogen-responsive transcriptomes from MCF-7 cells and the Wnt signaling pathway. These findings suggest that the divergent proliferative responses of MDA-MB-453 cells to DHT and MPA result from the different genetic programs elicited by these two ligands through the AR-Q865H variant. This work highlights the necessity to characterize additional models of molecular apocrine breast cancer to determine the precise role of AR signaling in this breast cancer subtype.

Apigenin induces apoptosis and blocks growth of medroxyprogesterone acetate-dependent BT-474 xenograft tumors

Recent clinical and epidemiological evidence shows that hormone replacement therapy (HRT) containing both estrogen and progestin increases the risk of primary and metastatic breast cancer in post-menopausal women while HRT containing only estrogen does not. We and others previously showed that progestins promote the growth of human breast cancer cells in vitro and in vivo. In this study, we sought to determine whether apigenin, a low molecular weight anti-carcinogenic flavonoid, inhibits the growth of aggressive Her2/neu-positive BT-474 xenograft tumors in nude mice exposed to medroxyprogesterone acetate (MPA), the most commonly used progestin in the USA. Our data clearly show that apigenin (50 mg/kg) inhibits progression and development of these xenograft tumors by inducing apoptosis, inhibiting cell proliferation, and reducing expression of Her2/neu. Moreover, apigenin reduced levels of vascular endothelial growth factor (VEGF) without altering blood vessel density, indicating that continued expression of VEGF may be required to promote tumor cell survival and maintain blood flow. While previous studies showed that MPA induces receptor activator of nuclear factor kappa-B ligand (RANKL) expression in rodent mammary gland, MPA reduced levels of RANKL in human tumor xenografts. RANKL levels remained suppressed in the presence of apigenin. Exposure of BT-474 cells to MPA in vitro also resulted in lower levels of RANKL; an effect that was independent of progesterone receptors since it occurred both in the presence and absence of the antiprogestin RU-486. In contrast to our in vivo observations, apigenin protected against MPA-dependent RANKL loss in vitro, suggesting that MPA and apigenin modulate RANKL levels differently in breast cancer cells in vivo and in vitro. These preclinical findings suggest that apigenin has potential as an agent for the treatment of progestin-dependent breast disease.

Expression and function of nuclear receptor co-activator 4: evidence of a potential role independent of co-activator activity

Nuclear receptor coactivator 4 (NcoA4), also known as androgen receptor-associated protein 70 (ARA70), was initially discovered as a component of Ret-Fused Gene expressed in a subset of papillary thyroid carcinomas. Subsequent studies have established NcoA4 as a coactivator for a variety of nuclear receptors, including peroxisome proliferator activated receptors α and γ, and receptors for steroid hormones, vitamins D and A, thyroid hormone, and aryl hydrocarbons. While human NcoA4 has both LXXLL and FXXLF motifs that mediate p160 coactivator nuclear receptor interactions, this ubiquitously expressed protein lacks clearly defined functional domains. Several studies indicate that NcoA4 localizes predominantly to the cytoplasm and affects ligand-binding specificity of the androgen receptor, which has important implications for androgen-independent prostate cancer. Two NcoA4 variants, which may exert differential activities, have been identified in humans. Recent studies suggest that NcoA4 may play a role in development, carcinogenesis, inflammation, erythrogenesis, and cell cycle progression that may be independent of its role as a receptor coactivator. This review summarizes what is currently known of the structure, expression, regulation, and potential functions of this unique protein in cancerous and non-cancerous pathologies.

Dynamic distribution of nuclear coactivator 4 during mitosis: association with mitotic apparatus and midbodies

The cytoplasmic localization of Nuclear Receptor Coactivator 4 (NcoA4), also referred to as androgen receptor associated protein 70 (ARA70), indicates it may possess activities in addition to its role within the nucleus as a transcriptional enhancer. Towards identifying novel functions of NcoA4, we performed an in silico analysis of its amino acid sequence to identify potential functional domains and related proteins, and examined its subcellular distribution throughout the cell cycle. NcoA4 has no known or predicted functional or structural domains with the exception of an LxxLL and FxxLF nuclear receptor interaction motif and an N-terminal putative coiled-coil domain. Phylogenetic analysis indicated that NcoA4 has no paralogs and that a region referred to as ARA70-I family domain, located within the N-terminus and overlapping with the coiled-coil domain, is evolutionarily conserved in metazoans ranging from cnidarians to mammals. An adjacent conserved region, designated ARA70-II family domain, with no significant sequence similarity to the ARA70-I domain, is restricted to vertebrates. We demonstrate NcoA4 co-localizes with microtubules and microtubule organizing centers during prophase. Strong NcoA4 accumulation at the centrosomes was detected during interphase and telophase, with decreased levels at metaphase and anaphase. NcoA4 co-localized with tubulin and acetylated tubulin to the mitotic spindles during metaphase and anaphase, and to midbodies during telophase. Consistent with these observations, we demonstrated an interaction between NcoA4 and α-tubulin. Co-localization was not observed with microfilaments. These findings indicate a dynamic distribution of NcoA4 with components of the mitotic apparatus that is consistent with a potential non-transcriptional regulatory function(s) during cell division, which may be evolutionarily conserved.

Distinct function of androgen receptor coactivator ARA70α and ARA70β in mammary gland development, and in breast cancer

Steroid receptor coactivators are important in regulating the function of the receptors in endocrine organ development and in cancers, including breast. Androgen receptor (AR) coactivator ARA70, was first identified as a gene fused to the ret oncogene and later characterized as an AR coactivator. We previously reported that the full length ARA70α functions as a tumor suppressor gene and that ARA70β functions as an oncogene in prostate cancer. Here we show that both ARA70α and ARA70β function as AR and estrogen receptor (ER) coactivators in breast cancer cells. However, ARA70α and ARA70β serve different functions in mammary gland development and breast cancer tumorigenesis. We observed hypoplastic development of mammary glands in MMTV driven ARA70α transgenic mice and overgrowth of mammary glands in ARA70β transgenic mice at virgin and pregnant stages. We determined that ARA70α inhibited cell proliferation, and that ARA70β promotes proliferation in MCF7 breast cancer cells. These effects were observed in hormone-free media, or in media with androgen or estrogen, though to varying degrees. Additionally, we observed that ARA70β strongly enhanced the invasive ability of MCF7 breast cancer cells in in vitro Matrigel assays. Significantly, decreased ARA70α expression is associated with increased tendency of breast cancer metastasis. In summary, ARA70α and ARA70β have distinct effects in mammary gland development and in the progression of breast cancer.

Differential effects of a complex organochlorine mixture on the proliferation of breast cancer cell lines

Organochlorine compounds (OCs) are a group of persistent chemicals that accumulate in fatty tissues with age. Although OCs has been tested individually for their capacity to induce breast cancer cell proliferation, few studies examined the effect of complex mixtures that comprise compounds frequently detected in the serum of women. We constituted such an OC mixture containing 15 different components in environmentally relevant proportions and assessed its proliferative effects in four breast cancer cell lines (MCF-7, T47D, CAMA-1, MDAMB231) and in non-cancerous CV-1 cells. We also determined the capacity of the mixture to modulate cell cycle stage of breast cancer cells and to induce estrogenic and antiandrogenic effects using gene reporter assays. We observed that low concentrations of the mixture (100 × 10(3) and 50 × 10(3) dilutions) stimulated the proliferation of MCF-7 cells while higher concentrations (10 × 10(3) and 5 × 10(3) dilutions) had the opposite effect. In contrast, the mixture inhibited the proliferation of non-hormone-dependent cell lines. The mixture significantly increased the number of MCF-7 cells entering the S phase, an effect that was blocked by the antiestrogen ICI 182,780. Low concentrations of the mixture also caused an increase in CAMA-1 cell proliferation but only in the presence estradiol and dihydrotestosterone (p<0.05 at the 50 × 10(3) dilution). DDT analogs and polychlorinated biphenyls all had the capacity to stimulate the proliferation of CAMA-1 cells in the presence of sex steroids. Reporter gene assays further revealed that the mixture and several of its constituents (DDT analogs, aldrin, dieldrin, β-hexachlorocyclohexane, toxaphene) induced estrogenic effects, whereas the mixture and several components (DDT analogs, aldrin, dieldrin and PCBs) inhibited the androgen signaling pathway. Our results indicate that the complex OC mixture increases the proliferation of MCF-7 cells due to its estrogenic potential. The proliferative effect of the mixture on CAMA-1 cells in the presence of sex steroids appears mostly due to the antiandrogenic properties of p,p'-DDE, a major constituent of the mixture. Other mixtures of contaminants that include emerging compounds of interest such as brominated flame retardants and perfluoroalkyl compounds should be tested for their capacity to induce breast cancer cell proliferation.

A novel HSP90 inhibitor delays castrate-resistant prostate cancer without altering serum PSA levels and inhibits osteoclastogenesis

PURPOSE

Prostate cancer responds initially to antiandrogen therapies; however, progression to castration-resistant disease frequently occurs. Therefore, there is an urgent need for novel therapeutic agents that can prevent the emergence of castrate-resistant prostate cancer (CRPC). HSP90 is a molecular chaperone involved in the stability of many client proteins including Akt and androgen receptor (AR). 17-Allylamino-17-demethoxy-geldanamycin (17-AAG) has been reported to inhibit tumor growth in various cancers; however, it induces tumor progression in the bone microenvironment.

METHODS

Cell growth, apoptosis, and AR transactivation were examined by crystal violet assay, flow cytometric, and luciferase assays, respectively. The consequence of HSP90 therapy in vivo was evaluated in LNCaP xenograft model. The consequence of PF-04928473 therapy on bone metastasis was studied using an osteoclastogenesis in vitro assay.

RESULTS

PF-04928473 inhibits cell growth in a panel of prostate cancer cells, induces cell-cycle arrest at sub-G(1), and leads to apoptosis and increased caspase-3 activity. These biological events were accompanied by decreased activation of Akt and Erk as well as decreased expression of Her2, and decreased AR expression and activation in vitro. In contrast to 17-AAG, PF-04928473 abrogates RANKL-induced osteoclast differentiation by affecting NF-κB activation and Src phosphorylation. Finally, PF-04929113 inhibited tumor growth and prolonged survival compared with controls. Surprisingly, PF-04929113 did not reduce serum prostate-specific antigen (PSA) levels in vivo; in parallel, these decrease in tumor volume.

CONCLUSION

These data identify significant anticancer activity of PF-04929113 in CRPC but suggest that serum PSA may not prove useful as pharmacodynamic tool for this drug.

Radiolabeled 5-iodo-3'-O-(17beta-succinyl-5alpha-androstan-3-one)-2'-deoxyuridine and its 5'-monophosphate for imaging and therapy of androgen receptor-positive cancers: synthesis and biological evaluation

High levels of androgen receptor (AR) are often indicative of recurrent, advanced, or metastatic cancers. These conditions are also characterized by a high proliferative fraction. 5-Radioiodo-3'-O-(17beta-succinyl-5alpha-androstan-3-one)-2'-deoxyuridine 8 and 5-radioiodo-3'-O-(17beta-succinyl-5alpha-androstan-3-one)-2'-deoxyuridin-5'-yl monophosphate 13 target AR. They are also degraded intracellularly to 5-radioiodo-2'-deoxyuridine 1 and its monophosphate 20, respectively, which can participate in the DNA synthesis. Both drugs were prepared at the no-carrier-added level. Precursors and methods are readily adaptable to radiolabeling with various radiohalides suitable for SPECT and PET imaging, as well as endoradiotherapy. In vitro and in vivo studies confirm the AR-dependent interactions. Both drugs bind to sex hormone binding globulin. This binding significantly improves their stability in serum. Biodistribution and imaging studies show preferential uptake and retention of 8 and 13 in ip xenografts of human ovarian adenocarcinoma cells NIH:OVCAR-3, which overexpress AR. When these drugs are administered at therapeutic dose levels, a significant tumor growth arrest is observed.

Variable expression of nuclear receptor coactivator 4 (NcoA4) during mouse embryonic development

Human nuclear receptor coactivator 4 (NcoA4) amplifies the activity of several ligand-activated nuclear transcription factors, including the aryl hydrocarbon receptor (AhR) and androgen receptor (AR). Because these receptors exert important regulatory effects during development, with AhR ubiquitously expressed after embryonic day 9.5 (E9.5) and AR expressed from E12 onward, we examined NcoA4 expression in mouse embryos from E9.5 to E17.5. Full-length NcoA4 transcript was detected by RT-PCR at all embryonic stages and in all adult mouse tissues examined, although a novel splice variant was also detected. Western blot analysis indicated the expression of full-length NcoA4 protein, which was more highly expressed at later (E15.5-E17.5) embryonic stages. NcoA4 protein was also present at varying levels in all adult mouse tissues examined. A dynamic expression profile for NcoA4 during early development was indicated by immunohistochemistry in cardiac, hepatic, and lung tissue. Unlike human NcoA4, murine NcoA4 lacks an LXXLL motif, which has been implicated in the interaction with AR. Overexpression of murine NcoA4 augmented the transcriptional activity of AhR by 5-fold and AR by only 1.5-fold in COS cells. These studies demonstrate ubiquitous NcoA4 expression throughout development and suggest that this coactivator may play a role in modulating nuclear receptor activity, particularly that of the AhR, during development.

Genes and networks expressed in perioperative omental adipose tissue are correlated with weight loss from Roux-en-Y gastric bypass

CONTEXT

Gastric bypass surgery is the most commonly performed bariatric surgical procedure in the United States. Variable weight loss following this relatively standardized intervention has been reported. To date, a method for reliable profiling of patients who will successfully sustain weight loss for the long term has not been established. In addition, the mechanisms of action in accomplishing major weight loss as well as the explanation for the variable weight loss have not been established.

OBJECTIVE

To examine whether gene expression in perioperative omental adipose is associated with gastric bypass-induced weight loss.

DESIGN

Cross-sectional study of gene expression in perisurgical omental adipose tissues taken/available at the time of operation and total excess weight loss (EWL).

SUBJECTS

Fifteen overweight individuals who underwent Roux-en-Y gastric bypass (RYGB) surgery at the University of California Davis Medical Center (BMI: 40.6-72.8 kg/m(2)).

MEASUREMENTS

Body weight before and following weight stabilization 18-42 months after surgery. Perioperative omental adipose RNA isolated from 15 subjects was hybridized to Affymetrix HG-U133A chips for 22,283 transcript expression measurements.

RESULTS

Downstream analysis identified a set of genes whose expression was significantly correlated with RYGB-induced weight loss. The significant individual genes include acyl-coenzyme A oxidase 1 (ACOX1), phosphodiesterase 3A cGMP-inhibited (PDE3A) and protein kinase, AMP-activated, beta 1 non-catalytic subunit (PRKAB1). Specifically, ACOX1 plays a role in fatty acid metabolism. PDE3A is involved in purine metabolism and hormone-stimulated lipolysis. PRKAB1 is involved in adipocytokine signaling pathway. Gene network analysis revealed that pathways for glycerolipid metabolism, breast cancer and apoptosis were significantly correlated with long-term weight loss.

CONCLUSION

This study demonstrates that RNA expression profiles from perioperative adipose tissue are associated with weight loss outcome following RYGB surgery. Our data suggest that EWL could be predicted from preoperative samples, which would allow for informed decisions about whether or not to proceed to surgery.

New insights into the functional mechanisms and clinical applications of the kallikrein-related peptidase family

The Kallikrein-related peptidase (KLK) family consists of fifteen conserved serine proteases that form the largest contiguous cluster of proteases in the human genome. While primarily recognized for their clinical utilities as potential disease biomarkers, new compelling evidence suggests that this family plays a significant role in various physiological processes, including skin desquamation, semen liquefaction, neural plasticity, and body fluid homeostasis. KLK activation is believed to be mediated through highly organized proteolytic cascades, regulated through a series of feedback loops, inhibitors, auto-degradation and internal cleavages. Gene expression is mainly hormone-dependent, even though transcriptional epigenetic regulation has also been reported. These regulatory mechanisms are integrated with various signaling pathways to mediate multiple functions. Dysregulation of these pathways has been implicated in a large number of neoplastic and non-neoplastic pathological conditions. This review highlights our current knowledge of structural/phylogenetic features, functional role and regulatory/signaling mechanisms of this important family of enzymes.

Human kallikrein 10, a predictive marker for breast cancer

Our laboratory is involved in identifying genes that can be used as early diagnostic or prognostic markers in breast cancer. We previously identified a gene (NES1) that is expressed in normal but not in transformed mammary epithelial cells (MECs). NES1 is located on chromosome 19q13.4 within the kallikrein locus and thus was designated as human kallikrein 10 (hK10), although we have been unable to detect any protease activity. Importantly, hK10 expression is decreased in a majority of breast cancer cell lines. Transfection of hK10 into hK10-negative breast cancer cells reduces the tumorigenicity. Using methylation-specific PCR and subsequent sequencing, we demonstrate a strong correlation between hypermethylation of hK10 and loss of mRNA expression. Further analysis showed that essentially 100% of normal breast specimens had hK10 expression, whereas 46% of ductal carcinoma in situ (DCIS) and the majority of infiltrating ductal carcinoma (IDC) samples lacked the hK10 mRNA. Importantly, hK10-negative DCIS diagnosed at the time of biopsy were subsequently diagnosed as IDC at the time of definitive surgery. It has been shown that hK10 protein expression is regulated by steroids. In addition to breast cancers, hK10 is downregulated in cervical cancer, prostate cancer and acute lymphocytic leukemia, whereas it is upregulated in ovarian cancers. These results point to the paradoxical role of hK10 in human cancers and underscore the importance of further studies of this kallikrein.

Serum and Urine Tissue Kallikrein Concentrations in Male-to-Female Transsexuals Treated with Antiandrogens and Estrogens

Background: The expression of human tissue kallikrein genes is regulated by steroid hormones, but most studies have been conducted with cancer cell lines. Our purpose was to examine serum and urinary tissue kallikrein concentration changes in male-to-female transsexuals before and after treatment with antiandrogens and estrogens.

Methods: Thirty-five male-to-female transsexuals receiving cyproterone acetate and estrogens (orally or transdermally) were included in this study. Serum and urine samples were collected before initiation of therapy and 4 and 12 months post therapy. ELISAs were used to measure multiple kallikreins in serum and urine.

Results: After antiandrogen and estrogen therapy, serum testosterone concentrations decreased dramatically, as did serum and urinary concentrations of human glandular kallikrein (hK2) and prostate-specific antigen (PSA; hK3). Statistically significant but relatively small changes in serum and urinary concentrations of many other kallikreins were also seen. Kallikreins in serum and urine were correlated before and after treatment.

Conclusions: The concentrations of hK2 and hK3, but not of any other kallikreins, decrease dramatically after combined antiandrogen and estrogen treatment in male-to-female transsexuals. The smaller responses of the other kallikreins presumably reflect their expression in multiple tissues.

Functional interaction of nuclear receptor coactivator 4 with aryl hydrocarbon receptor

Aryl hydrocarbon receptor (AhR) transcriptional activity is enhanced by interaction with p160 coactivators. We demonstrate here that NcoA4, a nuclear receptor coactivator, interacts with and amplifies AhR action. NcoA4-AhR and NcoA4-ARNT interactions were demonstrated by immunoprecipitation in T47D breast cancer and COS cells and was independent of ligand. Overexpression of NcoA4 enhanced AhR transcriptional activity 3.2-fold in the presence of dioxin, whereas overexpression of a splice variant, NcoA4beta, as well as a variant lacking the C-terminal region enhanced AhR transcriptional activity by only 1.6-fold. Enhanced AhR signaling by NcoA4 was independent of the LXXLL and FXXLF motifs or of the activation domain. NcoA4 protein localized to cytoplasm in the absence of dioxin and in both the cytoplasm and nucleus following dioxin treatment. NcoA4-facilitation of AhR activity was abolished by overexpression of androgen receptor, suggesting a potential competition of AhR and androgen receptor for NcoA4. These findings thus demonstrate a functional interaction between NcoA4 and AhR that may alter AhR activity to affect disease development and progression.

The human kallikrein 10 promoter contains a functional retinoid response element

Human kallikrein 10 (hK10) protein is expressed in normal breast but is significantly downregulated in a majority of invasive breast cancers. Thus, understanding how hK10 expression is regulated is of substantial significance. In this study, we analyzed the promoter region of hK10 using a website software (TRANSFAC 3.0), which predicted three possible retinoic acid response elements (RAREs), RARE1 at -1041 (TGACCTCGTGATCC), RARE2 at -859 (TGACCTCCTATGA) and RARE3 at -765 (TGACCTCCTGTGA), each with a half-site of a canonical sequence (TGACCT; reverse complement AGGTCA). Using electrophoretic mobility shift assays and nucleotide competition analysis, as well as chromatin immunoprecipitation of the native hK10 promoter, we demonstrated specific binding of RXR only to RARE1. The functional importance of RARE in the hK10 promoter was demonstrated by retinoid induction of hk10 promoter-reporters; furthermore, mutation of RARE1 but not of RARE2 or RARE3 abolished the induction of the reporter. Finally, we demonstrated the induction of hK10 mRNA and protein expression upon retinoid treatment of cells. In view of the correlation of the downregulation of hK10 mRNA and protein with breast cancer progression, these findings suggest a potential approach to restore hK10 expression in cancer patients.

The progestational and androgenic properties of medroxyprogesterone acetate: gene regulatory overlap with dihydrotestosterone in breast cancer cells

Introduction

Medroxyprogesterone acetate (MPA), the major progestin used for oral contraception and hormone replacement therapy, has been implicated in increased breast cancer risk. Is this risk due to its progestational or androgenic properties? To address this, we assessed the transcriptional effects of MPA as compared with those of progesterone and dihydrotestosterone (DHT) in human breast cancer cells.

Method

A new progesterone receptor-negative, androgen receptor-positive human breast cancer cell line, designated Y-AR, was engineered and characterized. Transcription assays using a synthetic promoter/reporter construct, as well as endogenous gene expression profiling comparing progesterone, MPA and DHT, were performed in cells either lacking or containing progesterone receptor and/or androgen receptor.

Results

In progesterone receptor-positive cells, MPA was found to be an effective progestin through both progesterone receptor isoforms in transient transcription assays. Interestingly, DHT signaled through progesterone receptor type B. Expression profiling of endogenous progesterone receptor-regulated genes comparing progesterone and MPA suggested that although MPA may be a somewhat more potent progestin than progesterone, it is qualitatively similar to progesterone. To address effects of MPA through androgen receptor, expression profiling was performed comparing progesterone, MPA and DHT using Y-AR cells. These studies showed extensive gene regulatory overlap between DHT and MPA through androgen receptor and none with progesterone. Interestingly, there was no difference between pharmacological MPA and physiological MPA, suggesting that high-dose therapeutic MPA may be superfluous.

Conclusion

Our comparison of the gene regulatory profiles of MPA and progesterone suggests that, for physiologic hormone replacement therapy, the actions of MPA do not mimic those of endogenous progesterone alone. Clinically, the complex pharmacology of MPA not only influences its side-effect profile; but it is also possible that the increased breast cancer risk and/or the therapeutic efficacy of MPA in cancer treatment is in part mediated by androgen receptor.

Human tissue kallikrein gene family: applications in cancer

Human tissue kallikrein genes, located on the long arm of chromosome 19, are a subgroup of the serine protease family of proteolytic enzymes. Initially thought to consist of three members, the human kallikrein locus has now been extended and includes 15 tandemly located genes. These genes, and their protein products, share a high degree of homology and are expressed in a wide array of tissues, mainly those that are under steroid hormone control. PSA (hK3) is one of the human kallikreins, and is the most useful tumor marker for prostate cancer screening, diagnosis, prognosis and monitoring. hK2, another prostate-specific kallikrein, has also been proposed as a complementary prostate cancer biomarker. In the past 5 years, the newly discovered kallikreins (KLK4-KLK15) have been associated with several types of cancer. For example, hK4, hK5, hK6, hK7, hK8, hK10, hK11, hK13 and hK14 are emerging biomarkers for ovarian, breast, prostate and testicular cancer. New evidence raises the possibility that some kallikreins are directly involved with cancer progression. We here review the evidence linking kallikreins and cancer and their applicability as novel biomarkers for cancer diagnosis and management.

The emerging roles of human tissue kallikreins in cancer

Human tissue kallikreins (hKs), which are encoded by the largest contiguous cluster of protease genes in the human genome, are secreted serine proteases with diverse expression patterns and physiological roles. Although primarily known for their clinical applicability as cancer biomarkers, recent evidence implicates hKs in many cancer-related processes, including cell-growth regulation, angiogenesis, invasion and metastasis. They have been shown to promote or inhibit neoplastic progression, acting individually and/or in cascades with other hKs and proteases, and might represent attractive targets for therapeutic intervention.

Paxillin: adapting to change

Molecular scaffold or adaptor proteins facilitate precise spatiotemporal regulation and integration of multiple signaling pathways to effect the optimal cellular response to changes in the immediate environment. Paxillin is a multidomain adaptor that recruits both structural and signaling molecules to focal adhesions, sites of integrin engagement with the extracellular matrix, where it performs a critical role in transducing adhesion and growth factor signals to elicit changes in cell migration and gene expression.

Discovery of estrogen receptor alpha target genes and response elements in breast tumor cells

Microarray analysis has identified 89 estrogen target genes. The cis-regulatory elements found upstream of those genes are not well conserved in mouse and human.

Background

Estrogens and their receptors are important in human development, physiology and disease. In this study, we utilized an integrated genome-wide molecular and computational approach to characterize the interaction between the activated estrogen receptor (ER) and the regulatory elements of candidate target genes.

Results

Of around 19,000 genes surveyed in this study, we observed 137 ER-regulated genes in T-47D cells, of which only 89 were direct target genes. Meta-analysis of heterogeneous in vitro and in vivo datasets showed that the expression profiles in T-47D and MCF-7 cells are remarkably similar and overlap with genes differentially expressed between ER-positive and ER-negative tumors. Computational analysis revealed a significant enrichment of putative estrogen response elements (EREs) in the cis-regulatory regions of direct target genes. Chromatin immunoprecipitation confirmed ligand-dependent ER binding at the computationally predicted EREs in our highest ranked ER direct target genes, NRIP1, GREB1 and ABCA3. Wider examination of the cis-regulatory regions flanking the transcriptional start sites showed species conservation in mouse-human comparisons in only 6% of predicted EREs.

Conclusions

Only a small core set of human genes, validated across experimental systems and closely associated with ER status in breast tumors, appear to be sufficient to induce ER effects in breast cancer cells. That cis-regulatory regions of these core ER target genes are poorly conserved suggests that different evolutionary mechanisms are operative at transcriptional control elements than at coding regions. These results predict that certain biological effects of estrogen signaling will differ between mouse and human to a larger extent than previously thought.

Human Tissue Kallikreins: Physiologic Roles and Applications in Cancer

Tissue kallikreins are members of the S1 family (clan SA) of trypsin-like serine proteases and are present in at least six mammalian orders. In humans, tissue kallikreins (hK) are encoded by 15 structurally similar, steroid hormone–regulated genes (KLK) that colocalize to chromosome 19q13.4, representing the largest cluster of contiguous protease genes in the entire genome. hKs are widely expressed in diverse tissues and implicated in a range of normal physiologic functions from the regulation of blood pressure and electrolyte balance to tissue remodeling, prohormone processing, neural plasticity, and skin desquamation. Several lines of evidence suggest that hKs may be involved in cascade reactions and that cross-talk may exist with proteases of other catalytic classes. The proteolytic activity of hKs is regulated in several ways including zymogen activation, endogenous inhibitors, such as serpins, and via internal (auto)cleavage leading to inactivation. Dysregulated hK expression is associated with multiple diseases, primarily cancer. As a consequence, many kallikreins, in addition to hK3/PSA, have been identified as promising diagnostic and/or prognostic biomarkers for several cancer types, including ovarian, breast, and prostate. Recent data also suggest that hKs may be causally involved in carcinogenesis, particularly in tumor metastasis and invasion, and, thus, may represent attractive drug targets to consider for therapeutic intervention.

Testosterone effects on the breast: implications for testosterone therapy for women

Androgens have important physiological effects in women. Postmenopausal androgen replacement, most commonly as testosterone therapy, is becoming increasingly widespread. This is despite the lack of clear guidelines regarding the diagnosis of androgen insufficiency, optimal therapeutic doses, and long-term safety data. With respect to the breast specifically, there is the potential for exogenous testosterone to exert either androgenic or indirect estrogenic actions, with the latter potentially increasing breast cancer risk. In experimental studies, androgens exhibit growth-inhibitory and apoptotic effects in some, but not all, breast cancer cell lines. Differing effects between cell lines appear to be due primarily to variations in concentrations of specific coregulatory proteins at the receptor level. In rodent breast cancer models, androgen action is antiproliferative and proapoptotic, and is mediated via the androgen receptor, despite the potential for testosterone and dehydroepiandrosterone to be aromatized to estrogen. The results from studies in rhesus monkeys suggest that testosterone may serve as a natural endogenous protector of the breast and limit mitogenic and cancer-promoting effects of estrogen on mammary epithelium. Epidemiological studies have significant methodological limitations and provide inconclusive results. The strongest data for exogenous testosterone therapy comes from primate studies. Based on such simulations, inclusion of testosterone in postmenopausal estrogen-progestin regimens has the potential to ameliorate the stimulating effects of combined estrogen-progestin on the breast. Research addressing this is warranted; however, the number of women that would be required for an adequately powered randomized controlled trial renders such a study unlikely.

Steroid hormone regulation of the human kallikrein 10 (KLK10) gene in cancer cell lines and functional characterization of the KLK10 gene promoter

BACKGROUND

The human kallikrein 10 (KLK10) gene is a new member of the human tissue kallikrein gene family. It encodes for a secreted serine protease (hK10) with predicted trypsin-like enzymatic activity. KLK10 is highly expressed in the sex organs and its expression level changes in malignancy.

METHODS

To determine the role of steroid hormones in KLK10 gene expression, we investigated its modulation by 17beta-estradiol, 5alpha-dihydrotestosterone, norgestrel, dexamethasone and aldosterone, at both the transcription and translation level, in a panel of cancer cell lines. After steroid hormone stimulation, the change of KLK10 mRNA was monitored with reverse transcriptase polymerase chain reaction and hK10 protein levels in the culture supernatant were quantified with an hK10-specific immunoassay. The presence of hormone response elements in the KLK10 gene promoter was examined with the chloramphenicol acetyltransferase reporter gene system.

RESULTS

The KLK10 expression was mainly up-regulated by estrogens, androgens and progestins, and to a lesser extent by dexamethasone and aldosterone in the breast cancer cell lines BT-474, MCF-7 and T-47D, both at the mRNA and protein levels. The effect of stimulation of these steroids on KLK10 expression varied among the cell lines. Estrogens, androgens and progestins were most potent in the BT-474, T-47D and MCF-7 cells, respectively. The up-regulation effect of estrogens, androgens, and progestins on KLK10 expression can be blocked by their antagonists ICI-182, 780, RU-56,187, and mifepristone, respectively. Time course studies showed that hK10 protein started to increase 1 day after steroid hormone stimulation and this increase persisted for 7 days. These data suggest that steroid hormones up-regulate KLK10 gene expression through direct interaction between hormone-receptor complexes and their cognate hormone response elements. To search for hormone response elements, we functionally characterized the KLK10 promoter by placing it upstream of the chloramphenicol acetyltransferase reporter gene. We found that KLK10 promoter activity did not rely on the presence of functional estrogen and androgen receptors. Also, the presence of functional estrogen and androgen receptors did not increase its constitutive activity. We suggest that the hormone response elements that mediate the transcriptional regulation of KLK10 are unlikely to locate in the KLK10 promoter.

CONCLUSIONS

Estrogens, androgens and progestins modulate KLK10 expression through their own receptors but this regulation is not mediated by steroid hormone response elements in the promoter of the KLK10 gene.

Androgens and cardiovascular disease

Globally, cardiovascular disease will continue causing most human deaths for the foreseeable future. The consistent gender gap in life span of approximately 5.6 yr in all advanced economies must derive from gender differences in age-specific cardiovascular death rates, which rise steeply in parallel for both genders but 5-10 yr earlier in men. The lack of inflection point at modal age of menopause, contrasting with unequivocally estrogen-dependent biological markers like breast cancer or bone density, makes estrogen protection of premenopausal women an unlikely explanation. Limited human data suggest that testosterone exposure does not shorten life span in either gender, and oral estrogen treatment increases risk of cardiovascular death in men as it does in women. Alternatively, androgen exposure in early life (perinatal androgen imprinting) may predispose males to earlier onset of atherosclerosis. Following the recent reevaluation of the estrogen-protection orthodoxy, empirical research has flourished into the role of androgens in the progression of cardiovascular disease, highlighting the need to better understand androgen receptor (AR) coregulators, nongenomic androgen effects, tissue-specific metabolic activation of androgens, and androgen sensitivity. Novel therapeutic targets may arise from understanding how androgens enhance early plaque formation and cause vasodilatation via nongenomic androgen effects on vascular smooth muscle, and how tissue-specific variations in androgen effects are modulated by AR coregulators as well as metabolic activation of testosterone to amplify (via 5alpha-reductase to form dihydrotestosterone acting on AR) or diversify (via aromatization to estradiol acting upon estrogen receptor alpha/beta) the biological effects of testosterone on the vasculature. Observational studies show that blood testosterone concentrations are consistently lower among men with cardiovascular disease, suggesting a possible preventive role for testosterone therapy, which requires critical evaluation by further prospective studies. Short-term interventional studies show that testosterone produces a modest but consistent improvement in cardiac ischemia over placebo, comparable to the effects of existing antianginal drugs. By contrast, testosterone therapy has no beneficial effects in peripheral arterial disease but has not been evaluated in cerebrovascular disease. Erectile dysfunction is most frequently caused by pelvic arterial insufficiency due to atherosclerosis, and its sentinel relationship to generalized atherosclerosis is insufficiently appreciated. The commonality of risk factor patterns and mechanisms (including endothelial dysfunction) suggests that the efficacy of antiatherogenic therapy is an important challenge with the potential to enhance men's motivation for prevention and treatment of cardiovascular diseases.