Overexpression of cyclin D1 is rare in human prostate carcinoma

MCM7 affects the cisplatin resistance of liver cancer cells and the development of liver cancer by regulating the PI3K/Akt signaling pathway

OBJECTIVE

Aberrant DNA replication is regarded as a component of cancer development. Minichromosome maintenance protein 7 (MCM7), which is critical for the initiation of DNA replication, is overexpressed in multiple malignancies. The effect of MCM7 on cell proliferation, apoptosis, and drug resistance of liver cancer and its mechanism were investigated in this study.

METHODS

MCM7 expression in normal liver cells, liver cancer cell lines, and tissues, as well as adjacent tissues, was determined by qRT-PCR. CCK-8 and flow cytometry was performed to detect cell viability, apoptosis, and cell cycle, respectively. The related mRNA and protein expressions were detected by qRT-PCR and western blot.

RESULTS

High expression of MCM7 was found in liver cancer tissues and cells, which results in notably lower survival time of patients. Cisplatin (DDP) could inhibit cell proliferation and affect MCM7 expression. Silencing of MCM7 inhibited cell viability, promoted cell apoptosis, arrested cell cycle at G1 phase, and enhanced the effect of DDP on cancer cells, while overexpression of MCM7 did the opposite. Moreover, silencing of MCM7 inhibited cyclinD1 and Ki-67 expressions. The overexpression of MCM7 increased phosphorylation levels of PI3K and AKT, activated the PI3K/AKT pathway, and weakened the inhibitory effect of DDP on the PI3K/AKT pathway.

CONCLUSION

Silencing of MCM7 may inhibit cell proliferation and promote apoptosis by regulating the PI3K/AKT pathway to affect the cell cycle, thus affecting the development of liver cancer, and improving the sensitivity of liver cancer cells to DDP.

Immunohistochemical expression of Cyclin D1 among Sudanese patients diagnosed with benign and malignant prostatic lesions

Objectives

Prostate cancer (PC) is common cancer worldwide. Several markers have been developed to differentiate between benign prostatic hyperplasia (BPH) from PC. A descriptive retrospective hospital-based study aimed at determining the expression of Cyclin D1 in BPH and PC. The study took place at different histopathology laboratories in Khartoum state, Sudan, from December 2016 to January 2019. Formalin-fixed paraffin-embedded blocks were sectioned and fixed in 3-aminopropyltriethoxysilane coated slides incubated into primary antibody for Cyclin D1. The assessment of immunoreactivity of Cyclin D1 of each section was done using the Gleason scoring system.

Results

A total of 153 males’ prostate sections included in this study, of them, 120 (78.4%) were PC, and 33 (21.6%) were BPH. Their age ranged from 45 to 88 years, mean age was 66.19 ± 8.599. 142 (92.8%) did not have a family history of PC, while 11 (7.2%) patients reported having a family history. The Gleason scoring showed a total of 81 (52.9%) patients with high-grade and 39 (25.5%) with low-grade. 118 (97.5%) patients had PC showed positive results for Cyclin D1, while BPH was 3 (2.5%). P value < 0.001. Cyclin D1 staining was associated with high-grade Gleason score and perineural invasion, P value 0.001.

Effects of Baneh (Pistacia atlantica) Gum on Human Breast Cancer Cell Line (MCF-7) and Its Interaction with Anticancer Drug Doxorubicin

Pistacia atlantica is one of the species of Anacardiaceae that grows in the wild in different regions of Iran. Traditionally, anacardiaceae family has antibacterial, fungicidal, and cytotoxic properties. Therefore, the present study was designed to investigate the possible cytotoxic and anti-proliferative properties of Baneh gum. Cytotoxicity of the plant gum was determined using MTT assay on MCF-7 human breast cancer cells. The cellular makers of apoptosis (caspase3 and P53) and cell proliferation (Cyclin-D1) were evaluated by western blotting. Doxorubicin was used as anticancer control drug in combination treatment. The result showed that Baneh gum (100 µg/mL) significantly induced cell damage, activated caspase3, and increased P53 protein level. In addition, Cyclin-D1 was significantly decreased in gum-incubated cells. Furthermore, combination treatment of cells with Baneh gum (25 µg/mL) and doxorubicin (200 nM) produced a significant cytotoxic effect as compared to each drug alone. In conclusion, Baneh gum (100 µg/mL) has a potential pro-apoptotic/anti-proliferative property against human breast cancer cells and its combination with doxorubicin in low doses may induce cell death effectively and be a potent modality to treat this type of cancer.

Estrogen receptor beta (ERβ) mediates expression of β-catenin and proliferation in prostate cancer cell line PC-3

The aim of the present study was to characterize the mechanism underlying estrogen effects on the androgen-independent prostate cancer cell line PC-3. 17β-estradiol and the ERβ-selective agonist DPN, but not the ERα-selective agonist PPT, increased the incorporation of [methyl-(3)H]thymidine and the expression of Cyclin D2, suggesting that ERβ mediates the proliferative effect of estrogen on PC-3 cells. In addition, upregulation of Cyclin D2 and incorporation of [methyl-(3)H]thymidine induced by 17β-estradiol and DPN were blocked by the ERβ-selective antagonist PHTPP in PC-3 cells. Upregulation of Cyclin D2 and incorporation of [methyl-(3)H]thymidine induced by DPN were also blocked by PKF118-310, a compound that disrupts β-catenin-TCF (T-cell-specific transcription factor) complex, suggesting the involvement of β-catenin in the estradiol effects in PC-3 cells. A diffuse immunostaining for non-phosphorylated β-catenin was detected in the cytoplasm of PC-3 cells. Low levels of non-phosphorylated β-catenin immunostaining were also detected near the plasma membrane and in nuclei. Treatment of PC-3 cells with 17β-estradiol or DPN markedly increased non-phosphorylated β-catenin expression. These effects were blocked by pretreatment with the ERβ-selective antagonist PHTPP, PI3K inhibitor Wortmannin or AKT inhibitor MK-2206, indicating that ERβ-PI3K/AKT mediates non-phosphorylated β-catenin expression. Cycloheximide blocked the DPN-induced upregulation of non-phosphorylated β-catenin, suggesting de novo synthesis of this protein. In conclusion, these results suggest that estrogen may play a role in androgen-independent prostate cancer cell proliferation through a novel pathway, involving ERβ-mediated activation of β-catenin.

Proapoptotic and Antiproliferative Effects of Thymus caramanicus on Human Breast Cancer Cell Line (MCF-7) and Its Interaction with Anticancer Drug Vincristine

Thymus caramanicus Jalas is one of the species of thymus that grows in the wild in different regions of Iran. Traditionally, leaves of this plant are used in the treatment of diabetes, arthritis, and cancerous situation. Therefore, the present study was designed to investigate the selective cytotoxic and antiproliferative properties of Thymus caramanicus extract (TCE). MCF-7 human breast cancer cells were used in this study. Cytotoxicity of the extract was determined using MTT and neutral red assays. Biochemical markers of apoptosis (caspase 3, Bax, and Bcl-2) and cell proliferation (cyclin D1) were evaluated by immunoblotting. Vincristine was used as anticancer control drug in extract combination therapy. The data showed that incubation of cells with TCE (200 and 250 μg/mL) significantly increased cell damage, activated caspase 3 and Bax/Bcl2 ratio. In addition, cyclin D1 was significantly decreased in TCE-treated cells. Furthermore, concomitant treatment of cells with extract and anticancer drug produced a significant cytotoxic effect as compared to extract or drugs alone. In conclusion, thymus extract has a potential proapoptotic/antiproliferative property against human breast cancer cells and its combination with chemotherapeutic agent vincristine may induce cell death effectively and be a potent modality to treat this type of cancer.

Cyclin D1 (CCND1) expression is involved in estrogen receptor beta (ERβ) in human prostate cancer

BACKGROUND

Estrogen receptor beta (ERβ) has been demonstrated to be expressed in prostate carcinoma cells and estrogen signals through ERβ to act as a tumor suppressor in prostate cancer patients. ERβ is thought to regulate the cell cycle of prostate carcinoma cells by controlling the expression of cell cycle regulators including cyclin D1 (CCND1). This interaction is of particular interest as CCND1 has been implicated in the development of prostate cancer.

METHODS

We evaluated ERβ and CCND1 immunoreactivity in human prostate cancer (n = 112, surgical specimens), and correlated the findings with clinicopathological features of the patients. Subsequent in vitro experiments using PC-3 prostate carcinoma cells were also performed to examine whether estradiol (E2) could change the expression level of CCND1 mRNA.

RESULTS

CCND1 immunoreactivity was detected in 78/112 cases (70%), and was significantly correlated with incidence of perineural invasion and ERβ immunoreactivity (P < 0.05). Forty-eight hours incubation with E2 (10 nM) increased the expression level of CCND1 mRNA as well as c-jun (JUN) and c-fos (FOS) in PC-3 cells, and PHTPP (ERβ antagonist) suppressed E2 -induced expression of those mRNAs.

CONCLUSIONS

These findings suggest that CCND1 expression is possibly regulated by estrogens via ERβ and that this signaling pathway may influence prostate cancer development.

Molecular mechanisms of curcumin action: gene expression

Curcumin derived from the tropical plant Curcuma longa has a long history of use as a dietary agent, food preservative, and in traditional Asian medicine. It has been used for centuries to treat biliary disorders, anorexia, cough, diabetic wounds, hepatic disorders, rheumatism, and sinusitis. The preventive and therapeutic properties of curcumin are associated with its antioxidant, anti-inflammatory, and anticancer properties. Extensive research over several decades has attempted to identify the molecular mechanisms of curcumin action. Curcumin modulates numerous molecular targets by altering their gene expression, signaling pathways, or through direct interaction. Curcumin regulates the expression of inflammatory cytokines (e.g., TNF, IL-1), growth factors (e.g., VEGF, EGF, FGF), growth factor receptors (e.g., EGFR, HER-2, AR), enzymes (e.g., COX-2, LOX, MMP9, MAPK, mTOR, Akt), adhesion molecules (e.g., ELAM-1, ICAM-1, VCAM-1), apoptosis related proteins (e.g., Bcl-2, caspases, DR, Fas), and cell cycle proteins (e.g., cyclin D1). Curcumin modulates the activity of several transcription factors (e.g., NF-κB, AP-1, STAT) and their signaling pathways. Based on its ability to affect multiple targets, curcumin has the potential for the prevention and treatment of various diseases including cancers, arthritis, allergies, atherosclerosis, aging, neurodegenerative disease, hepatic disorders, obesity, diabetes, psoriasis, and autoimmune diseases. This review summarizes the molecular mechanisms of modulation of gene expression by curcumin.

Induction of apoptosis coupled to endoplasmic reticulum stress in human prostate cancer cells by n-butylidenephthalide

BACKGROUND

N-butylidenephthalide (BP) exhibits antitumor effect in a variety of cancer cell lines. The objective of this study was to obtain additional insights into the mechanisms involved in BP induced cell death in human prostate cancer cells.

METHODS/PRINCIPAL FINDINGS

Two human prostate cancer cell lines, PC-3 and LNCaP, were treated with BP, and subsequently evaluated for their viability and cell cycle profiles. BP caused cell cycle arrest and cell death in both cell lines. The G0/G1 phase arrest was correlated with increase levels of CDK inhibitors (p16, p21 and p27) and decrease of the checkpoint proteins. To determine the mechanisms of BP-induced growth arrest and cell death in prostate cancer cell lines, we performed a microarray study to identify alterations in gene expression induced by BP in the LNCaP cells. Several BP-induced genes, including the GADD153/CHOP, an endoplasmic reticulum stress (ER stress)-regulated gene, were identified. BP-induced ER stress was evidenced by increased expression of the downstream molecules GRP78/BiP, IRE1-α and GADD153/CHOP in both cell lines. Blockage of IRE1-α or GADD153/CHOP expression by siRNA significantly reduced BP-induced cell death in LNCaP cells. Furthermore, blockage of JNK1/2 signaling by JNK siRNA resulted in decreased expression of IRE1-α and GADD153/CHOP genes, implicating that BP-induced ER stress may be elicited via JNK1/2 signaling in prostate cancer cells. BP also suppressed LNCaP xenograft tumor growth in NOD-SCID mice. It caused 68% reduction in tumor volume after 18 days of treatment.

CONCLUSIONS

Our results suggest that BP can cause G0/G1 phase arrest in prostate cancer cells and its cytotoxicity is mediated by ER stress induction. Thus, BP may serve as an anticancer agent by inducing ER stress in prostate cancer.

Inhibitory effects of the HDAC inhibitor valproic acid on prostate cancer growth are enhanced by simultaneous application of the mTOR inhibitor RAD001

AIMS

To analyze the combined impact of the histone deacetylase (HDAC) inhibitor valproic acid (VPA) and the mammalian target of rapamycin (mTOR) inhibitor RAD001 on prostate cancer cell growth.

MAIN METHODS

PC-3, DU-145 and LNCaP cells were treated with RAD001, VPA or with an RAD001-VPA combination for 3 or 5 days. Tumor cell growth, cell cycle progression and cell cycle regulating proteins were then investigated by MTT assay, flow cytometry and Western blotting, respectively. Effects of drug treatment on cell signaling pathways were determined.

KEY FINDINGS

Separate application of RAD001 or VPA distinctly reduced tumor cell growth and impaired cell cycle progression. Significant additive effects were evoked when both drugs were used in concert. Particularly, the cell cycle regulating proteins cdk1, cdk2, cdk4 and cyclin B were reduced, whereas p21 and p27 were enhanced by the RAD001-VPA combination. Signaling analysis revealed deactivation of EGFr, ERK1/2 and p70S6k. Phosphorylation of Akt was diminished in DU-145 but elevated in PC-3 and LNCaP cells.

SIGNIFICANCE

The RAD001-VPA combination exerted profound antitumor properties on a panel of prostate cancer cell lines. Therefore, simultaneous blockage of HDAC and mTOR related pathways should be considered when designing novel therapeutic strategies for treating prostate carcinoma.

Prostasin regulates iNOS and cyclin D1 expression by modulating protease-activated receptor-2 signaling in prostate epithelial cells

BACKGROUND

Prostasin is down-regulated during inflammation and in invasive cancers, and plays a role in regulation of inflammatory gene expression and invasion.

METHODS

We used the human benign prostatic hyperplasia cell line BPH-1 to investigate gene expression changes associated with siRNA-mediated loss of prostasin expression. Quantitative PCR and/or western blotting were used to evaluate the expression changes of iNOS, ICAM-1, cyclin D1, IL-6, and IL-8. Gene expression changes were also evaluated in the presence of a PAR-2 antagonist. The PC-3 human prostate cancer cell line was used for evaluation of gene expression in response to prostasin re-expression.

RESULTS

Prostasin silencing in BPH-1 was associated with up-regulation of iNOS, ICAM-1, IL-6, and IL-8, and down-regulation of cyclin D1; as well as reduced proliferation and invasion. The iNOS up-regulation and cyclin D1 down-regulation associated with prostasin silencing were inhibited by a PAR-2 antagonist. Re-expression of prostasin, a serine active-site mutant, and a GPI-anchor-free mutant, in the PC-3 cells resulted in PAR-2 and cyclin D1 transcription up-regulation. Transcription up-regulation of IL-6 and IL-8 was associated with re-expression of the serine active-site mutant prostasin in the PC-3 cells. Transcription up-regulation of IL-8, but to a lesser extent, was also observed in PC-3 cells expressing the wild-type prostasin. Expression of a serine protease active prostasin, GPI-anchored or anchor-free, prevented the IL-6 induction in response to PAR-2. The GPI-anchor-free prostasin also prevented the IL-8 induction.

CONCLUSIONS

Prostasin plays a negative regulatory role on PAR-2-mediated signaling in prostate epithelial cells.

Tailoring to RB: tumour suppressor status and therapeutic response

The retinoblastoma tumour suppressor (RB) is a crucial regulator of cell-cycle progression that is invoked in response to a myriad of anti-mitogenic signals. It has been hypothesized that perturbations of the RB pathway confer a synonymous proliferative advantage to tumour cells; however, recent findings demonstrate context-specific outcomes associated with such lesions. Particularly, loss of RB function is associated with differential response to wide-ranging therapeutic agents. Thus, the status of this tumour suppressor may be particularly informative in directing treatment regimens.

Genetic changes and DNA damage responses in the prostate

The integrity of genomic DNA is challenged by genotoxic stress originating during normal cellular metabolism or by external insults. Cellular responses to DNA damage involve elegant checkpoint cascades enforcing cell cycle arrest, damage repair, apoptosis or cellular senescence. The loss or alterations of genes involved in the damage response pathways have been reported in many cancer susceptibility syndromes and in sporadic tumors. Furthermore, this surveillance pathway is activated during early tumourigenesis presumably due to uncontrolled replicative cycles and has been recognized as one of the main barriers against the development of cancer. This review discusses the relevance of prostatic epithelial cells in prostate tumourigenesis and highlights common molecular changes associated with prostate cancer. Furthermore, DNA damage responses of primary cultures of human prostatic epithelial cells and fresh human prostate tissues are discussed providing evidence for alterations in crucial DNA damage checkpoint molecules. New insights connecting prostate tumourigenesis to alterations and defects in the pathways maintaining genomic integrity will be discussed.

Role of curcumin in health and disease

Curcumin (diferuloylmethane) is an orange-yellow component of turmeric (Curcuma longa), a spice often found in curry powder. In recent years, considerable interest has been focused on curcumin due to its use to treat a wide variety of disorders without any side effects. It is one of the major curcuminoids of turmeric, which impart its characteristic yellow colour. It was used in ancient times on the Indian subcontinent to treat various illnesses such as rheumatism, body ache, skin diseases, intestinal worms, diarrhoea, intermittent fevers, hepatic disorders, biliousness, urinary discharges, dyspepsia, inflammations, constipation, leukoderma, amenorrhea, and colic. Curcumin has the potential to treat a wide variety of inflammatory diseases including cancer, diabetes, cardiovascular diseases, arthritis, Alzheimer's disease, psoriasis, etc, through modulation of numerous molecular targets. This article reviews the use of curcumin for the chemoprevention and treatment of various diseases.

Tissue-Specific Consequences of Cyclin D1 Overexpression in Prostate Cancer Progression

The cyclin D1 oncogene encodes the regulatory subunit of a holoenzyme that phosphorylates and inactivates the Rb protein and promotes progression through G(1) to S phase of the cell cycle. Several prostate cancer cell lines and a subset of primary prostate cancer samples have increased cyclin D1 protein expression. However, the relationship between cyclin D1 expression and prostate tumor progression has yet to be clearly characterized. This study examined the effects of manipulating cyclin D1 expression in either human prostatic epithelial or stromal cells using a tissue recombination model. The data showed that overexpression of cyclin D1 in the initiated BPH-1 cell line increased cell proliferation rate but did not elicit tumorigenicity in vivo. However, overexpression of cyclin D1 in normal prostate fibroblasts (NPF) that were subsequently recombined with BPH-1 did induce malignant transformation of the epithelial cells. The present study also showed that recombination of BPH-1 + cyclin D1-overexpressing fibroblasts (NPF(cyclin D1)) resulted in permanent malignant transformation of epithelial cells (BPH-1(NPF-cyclin D1) cells) similar to that seen with carcinoma-associated fibroblasts (CAF). Microarray analysis showed that the expression profiles between CAFs and NPF(cyclin D1) cells were highly concordant including cyclin D1 up-regulation. These data indicated that the tumor-promoting activity of cyclin D1 may be tissue specific.

Impact of differential cyclin D1 expression and localisation in prostate cancer

Cyclin D1 is a critical regulator of androgen-dependent transcription and cell cycle progression in prostate cancer cells. Despite the influence of D-type cyclins on prostate cancer proliferation, few studies have examined the expression of cyclin D1 in localised tumours or challenged its relevance to disease progression. Cyclin D1 status was characterised using immunohistochemistry in 38 non-neoplastic prostate samples, 138 primary human prostate carcinomas, and three lymph node metastatic specimens. Relevance of cyclin D1 to preoperative prostate-specific antigen (PSA) levels, Ki-67 index, and p21^Cip1 status was also examined. Cyclin D1-positive phenotype was increased in primary carcinoma compared to non-neoplastic tissue, and was evident in all lymph node metastases cases. Interestingly, at least three distinct localisation patterns were observed in the cyclin D1-positive cohort, wherein cytoplasmic localisation was identified in a large fraction, and this pattern was predominant in lower grade tumours. Relevance of altered cyclin D1 status was observed, wherein cyclin D1-positive tumours were associated with low preoperative PSA levels, consistent with in vitro reports that cyclin D1 may alter the expression of this tumour marker. Moreover, tumours with predominantly cytoplasmic cyclin D1 showed the lowest Ki-67 index, whereas nuclear cyclin D1 was associated with higher grade, elevated Ki-67, and increased nuclear p21^Cip1. These data demonstrate that differential cyclin D1 status may influence clinicopathological parameters, and reveal new insight as to the regulation and potential consequence of cyclin D1 expression in prostate cancer.

Regulation of cell proliferation in a stratified culture system of epithelial cells from prostate tissue

Mechanisms controlling epithelial proliferation and differentiation in the prostate have been primarily investigated in mouse models. The regulation of proliferation and differentiation is poorly understood in human prostate epithelial cells. In vivo, the glandular prostate epithelium consists of a p63-positive proliferating basal cell layer and a post-mitotic p27-positive secretory cell layer. We have established an organized stratified culture system of human primary prostate epithelial cells to gain insight into mechanisms regulating proliferation and differentiation. In this system, expression of p63 is observed in the bottom layer. In addition, BrdU incorporation persists even though cells are confluent. In contrast, in the upper layer, p63 expression is greatly diminished, p27 is expressed, and the cells are growth arrested. Overexpression of cyclin D1 or knockdown of p27 does not increase proliferation. After inactivation of the nuclear phosphoprotein Rb, the cell layers remain organized and cell proliferation increases only in the bottom layer. Furthermore, the expression of p63 remains confined to the bottom layer after Rb inactivation. Altogether, this in vitro model recapitulates certain aspects of in vivo growth regulation and differentiation and suggests that the loss of Rb family proteins in human cells trigger hyperplasia but is not sufficient for transformation.

Molecular targets of dietary agents for prevention and therapy of cancer

While fruits and vegetables are recommended for prevention of cancer and other diseases, their active ingredients (at the molecular level) and their mechanisms of action less well understood. Extensive research during the last half century has identified various molecular targets that can potentially be used not only for the prevention of cancer but also for treatment. However, lack of success with targeted monotherapy resulting from bypass mechanisms has forced researchers to employ either combination therapy or agents that interfere with multiple cell-signaling pathways. In this review, we present evidence that numerous agents identified from fruits and vegetables can interfere with several cell-signaling pathways. The agents include curcumin (turmeric), resveratrol (red grapes, peanuts and berries), genistein (soybean), diallyl sulfide (allium), S-allyl cysteine (allium), allicin (garlic), lycopene (tomato), capsaicin (red chilli), diosgenin (fenugreek), 6-gingerol (ginger), ellagic acid (pomegranate), ursolic acid (apple, pears, prunes), silymarin (milk thistle), anethol (anise, camphor, and fennel), catechins (green tea), eugenol (cloves), indole-3-carbinol (cruciferous vegetables), limonene (citrus fruits), beta carotene (carrots), and dietary fiber. For instance, the cell-signaling pathways inhibited by curcumin alone include NF-kappaB, AP-1, STAT3, Akt, Bcl-2, Bcl-X(L), caspases, PARP, IKK, EGFR, HER2, JNK, MAPK, COX2, and 5-LOX. The active principle identified in fruit and vegetables and the molecular targets modulated may be the basis for how these dietary agents not only prevent but also treat cancer and other diseases. This work reaffirms what Hippocrates said 25 centuries ago, let food be thy medicine and medicine be thy food.

Molecular changes in prostatic cancer

Prostate cancer is one of the most commonly diagnosed and potentially devastating cancers in men, throughout the world. However, the clinical manifestation of this disease varies greatly, from indolent tumours, requiring little or no treatment, to those aggressive cancers which require radical therapies. Prostate cancer, like all other cancers, develops and progresses as a consequence of an accumulation of genetic changes. While several putative genes have been isolated for the development of breast, ovarian and colon cancer, the aetiology and pathogenesis of prostate cancer remains poorly understood. In this review, we discuss important genetic markers in early, metastatic and hormone refractory prostate cancer which may, in the future, be used as markers for diagnosis and prognosis, as well as targets for therapeutic intervention.

Interaction of nuclear receptors with the Wnt/beta-catenin/Tcf signaling axis: Wnt you like to know?

The cross-regulation of Wnt/beta-catenin/Tcf ligands, kinases, and transcription factors with members of the nuclear receptor (NR) family has emerged as a clinically and developmentally important area of endocrine cell biology. Interactions between these signaling pathways result in a diverse array of cellular effects including altered cellular adhesion, tissue morphogenesis, and oncogenesis. Analyses of NR interactions with canonical Wnt signaling reveal two broad themes: Wnt/beta-catenin modulation of NRs (theme I), and ligand-dependent NR inhibition of the Wnt/beta-catenin/Tcf cascade (theme II). Beta-catenin, a promiscuous Wnt signaling member, has been studied intensively in relation to the androgen receptor (AR). Beta-catenin acts as a coactivator of AR transcription and is also involved in co-trafficking, increasing cell proliferation, and prostate pathogenesis. T cell factor, a transcriptional mediator of beta-catenin and AR, engages in a dynamic reciprocity of nuclear beta-catenin, p300/CREB binding protein, and transcriptional initiation factor 2/GC receptor-interaction protein, thereby facilitating hormone-dependent coactivation and transrepression. Beta-catenin responds in an equally dynamic manner with other NRs, including the retinoic acid (RA) receptor (RAR), vitamin D receptor (VDR), glucocorticoid receptor (GR), progesterone receptor, thyroid receptor (TR), estrogen receptor (ER), and peroxisome proliferator-activated receptor (PPAR). The NR ligands, vitamin D(3), trans/cis RA, glucocorticoids, and thiazolidines, induce dramatic changes in the physiology of cells harboring high Wnt/beta-catenin/Tcf activity. Wnt signaling regulates, directly or indirectly, developmental processes such as ductal branching and adipogenesis, two processes dependent on NR function. Beta-catenin has been intensively studied in colorectal cancer; however, it is now evident that beta-catenin may be important in cancers of the breast, prostate, and thyroid. This review will focus on the cross-regulation of AR and Wnt/beta-catenin/Tcf but will also consider the dynamic manner in which RAR/RXR, GR, TR, VDR, ER, and PPAR modulate canonical Wnt signaling. Although many commonalities exist by which NRs interact with the Wnt/beta-catenin signaling pathway, striking cell line and tissue-specific differences require deciphering and application to endocrine pathology.

Molecular markers of prostate cancer outcome

Molecular markers have the potential to serve not only as prognostic factors but may be targets for new therapeutic strategies and predictors of response in a range of cancers. Prostate cancer development and progression is predicated on a series of genetic and epigenetic events within the prostate cell and its milieu. Within this review, we identify candidate molecules involved in diverse processes such as cell proliferation, death and apoptosis, signal transduction, androgen receptor (AR) signalling, cellular adhesion and angiogenesis that are linked to outcome in prostate cancer. Current markers with potential prognostic value include p53, Bcl-2, p16INK4A, p27Kip1, c-Myc, AR, E-cadherin and vascular endothelial growth factor. Evolving technology permits the identification of an increasing number of molecular markers with prognosis and predictive potential. We also review the use of gene microarray analysis in gene discovery as a means of identifying and cosegregating novel markers of prostate cancer outcome. By integrating selected markers into prospective clinical trials, there is potential for us to provide specific targeted therapy tailored for an increasing number of patients.

Cyclin-dependent kinase 6 associates with the androgen receptor and enhances its transcriptional activity in prostate cancer cells

Cyclin-dependent kinase 6 (CDK6) binds to and is activated by cyclin D1 and thereby enhances the transition of cells through the G1 phase of the cell cycle. The present study indicates that, in human prostate cancer cells, CDK6 can also bind to the androgen receptor (AR) and stimulate its transcriptional activity in the presence of dihydrotestosterone. This effect of CDK6 does not require its kinase activity and is inhibited by cyclin D1 and p16INK4a. The T877A mutant of the AR frequently found in advanced cases of prostate cancer displays an exaggerated stimulation of transcriptional activity by CDK6. Androgen-sensitive LNCaP prostate cancer cells engineered to stably overexpress CDK6 display increased expression of the prostate-specific antigen and enhanced growth in the presence of dihydrotestosterone. CDK6 is present in the chromatin structure of these cells in association with the AR and the promoter region of the prostate-specific antigen gene. These findings suggest that CDK6 may play an important role in the development and/or progression of a subset of human prostate cancers by stimulating the activity of the AR.

A central domain of cyclin D1 mediates nuclear receptor corepressor activity

Regulation of nuclear receptor activity is the focus of numerous ongoing studies to develop novel therapies for the treatment of hormone-related cancer. Although cyclin D1 functions to control the activity of several nuclear receptors, the region(s) of the protein responsible for such transcriptional comodulation remain poorly defined. Herein, we map the region of cyclin D1 required for binding and repression of the androgen receptor (AR) to a central, exclusively alpha-helical domain. Deletion of this domain disrupted AR binding and corepressor activity. Further investigations showed that this domain is sufficient for AR interaction and possesses the ability to bind histone deacetylase 3. Strikingly, overexpression of this repressor region attenuates cell cycle progression in prostatic adenocarcinoma cells. The requirement of this domain for nuclear receptor repression was conserved with respect to thyroid hormone receptor beta-1, whereas cyclin D1 activation of the estrogen receptor occurred independently of the central region. Together, these data identify a minimal repression module within cyclin D1 and demonstrate that the coactivator and corepressor functions of cyclin D1 are distinct. In addition, our data suggest that properties of the cyclin D1 central domain could be exploited to develop novel prostate cancer therapeutics.

Conditional deletion of Rb causes early stage prostate cancer

Prostate cancer remains the second leading cause of cancer-related death for men in the United States. Mutations in tumor suppressor genes including retinoblastoma (Rb), p53, and PTEN have been linked to the development of prostate cancer in man and mouse models, and loss of heterozygosity of the Rb locus has been observed in up to 60% of clinical cases. In this study we demonstrate that conditional somatic deletion of even a single Rb allele in the epithelial cells of the mouse prostate causes focal hyperplasia, thereby establishing a causal relationship between Rb loss and development of early stage prostate cancer. As a consequence of Rb ablation we observed increased expression of E2F target genes and a concomitant increase in proliferation in the epithelial compartment. However, by 52 weeks of age these lesions had not become malignant and represent an early stage of the disease. Nevertheless, the multifocal nature of the phenotype in the mice closely resembled multifocality of clinical disease. Taken together, our data demonstrated that loss of pRB-mediated cell cycle control directly caused the initiation of proliferative prostate disease but was insufficient to cause malignancy. Establishment of this early initiation model will aid efforts to thoroughly characterize early prostate disease as well as the elucidation of molecular mechanisms that cooperate with Rb loss to facilitate progression and metastasis.

Expression of androgen receptor coregulators in prostate cancer

PURPOSE

The androgen receptor (AR)-mediated signaling pathway seems to be essentially involved in the development and progression of prostate cancer. In vitro studies have shown that altered expression of AR coregulators may significantly modify transcriptional activity of AR, suggesting that these coregulators could also contribute to the progression of prostate cancer. Here, our goal was to assess alterations in the expression of the AR coregulators in prostate cancer in vivo.

EXPERIMENTAL DESIGN

The expression of 16 AR coactivators and corepressors (SRC1, beta-catenin, TIF2, PIAS1, PIASx, ARIP4, BRCA1, AIB1, AIB3, CBP, STAT1, NCoR1, AES, cyclin D1, p300, and ARA24) was measured in prostate cancer cell lines, xenografts, and clinical prostate tumor specimens by using real-time quantitative reverse transcription-PCR. In addition, gene copy number of SRC1 was analyzed by fluorescence in situ hybridization.

RESULTS

Both AR-positive and AR-negative cell lines and xenografts expressed the coregulators. Most of the coregulators studied were expressed at equal levels in benign prostatic hyperplasia and untreated and hormone-refractory carcinomas. However, the expression of PIAS1 and SRC1 was significantly (P = 0.048 and 0.017, respectively) lower in hormone-refractory prostate tumors than in untreated prostate tumors. No overexpression of the coregulators was found in the clinical material. Paradoxically, the SRC1 gene was found to be amplified and highly expressed in a LuCaP 70 prostate cancer xenograft.

CONCLUSIONS

These findings suggest that the decreased expression of PIAS1 and SRC1 could be involved in the progression of prostate cancer. In addition, gene amplification of SRC1 in one of the xenografts implies that, in some tumors, genetic alteration of SRC1 may provide a growth advantage.

Increased risk of prostate cancer associated with AA genotype of cyclin D1 gene A870G polymorphism

CCND1 mRNA is alternatively spliced to produce 2 transcripts, and the splicing pattern may be modulated by a frequent A870G single-nucleotide polymorphism within the conserved splice donor site of exon 4. Several studies have suggested a significant association between the CCND1 genotype and onset or progression of various cancers. To investigate the correlation of the polymorphism with genetic susceptibility to PCa and its disease status, we examined the polymorphism in 214 cases of PCa, 234 cases of BPH and 254 male controls. The CCND1 A allele was more frequently observed in the PCa group (p = 0.015) and the BPH group (p = 0.018) than the control group. Men with the AA genotype had an increased risk of PCa (aOR = 1.93, 95% CI 1.13-3.30, p = 0.016) and BPH (aOR = 1.84, 95% CI 1.09-3.09, p = 0.023) compared to those with the GG genotype. No significant association was observed when men with the AG genotype were compared to those with the GG genotype (PCa: aOR = 1.00, 95% CI 0.65-1.54, BPH: aOR = 0.91, 95% CI 0.60-1.39). The risk of PCa associated with the AA genotype appeared to be stronger in men aged 73 years or younger (aOR = 2.89, 95% CI 1.38-6.01, p = 0.005), whereas no association was found in men older than 73 years (aOR = 1.02, 95% CI 0.44-2.34). No significant difference in genotype frequency was found among patients with low-, intermediate- and high-grade tumors (p = 0.730) or between patients with localized and metastatic PCa (p = 0.679). However, in patients with high-grade or metastatic PCa, a significantly increased risk associated with the AA genotype compared to controls was observed, while no significant results were found in those with low/intermediate or localized PCa. The A allele of the CCND1 A870G polymorphism was recessively associated with susceptibility to PCa and BPH in a Japanese population, giving a 2-fold increased risk of PCa and BPH in men with the AA genotype compared to those with the GG genotype. Although the risk of PCa associated with the AA genotype appeared to contribute especially to men aged 73 years or younger and the A allele may be associated with disease status of PCa, these conjectures require validation in future studies on a larger number of subjects.

Curcumin-induced suppression of cell proliferation correlates with down-regulation of cyclin D1 expression and CDK4-mediated retinoblastoma protein phosphorylation

Cyclin D1 is a proto-oncogene that is overexpressed in many cancers including breast and prostate. It plays a role in cell proliferation through activation of cyclin-dependent kinases. Curcumin, a diferuloylmethane, is a chemopreventive agent known to inhibit the proliferation of several breast and prostate cancer cell lines. It is possible that the effect of curcumin is mediated through the regulation of cyclin D1. In the present report we show that inhibition of the proliferation of various prostate, breast and squamous cell carcinoma cell lines by curcumin correlated with the down-regulation of the expression of cyclin D1 protein. In comparison, the down-regulation by curcumin of cyclin D2 and cyclin D3 was found only in selective cell lines. The suppression of cyclin D1 by curcumin led to inhibition of CDK4-mediated phosphorylation of retinoblastoma protein. We found that curcumin-induced down-regulation of cyclin D1 was inhibited by lactacystin, an inhibitor of 26S proteosome, suggesting that curcumin represses cyclin D1 expression by promoting proteolysis. We found that curcumin also down-regulated mRNA expression, thus suggesting transcriptional regulation. Curcumin also inhibited the activity of the cyclin D1 promoter-dependent reporter gene expression. Overall our results suggest that curcumin down-regulates cyclin D1 expression through activation of both transcriptional and post-transcriptional mechanisms, and this may contribute to the antiproliferative effects of curcumin against various cell types.

Cyclin D1: mechanism and consequence of androgen receptor co-repressor activity

Androgen receptor regulation is pivotal for prostate growth and development. Activation of the receptor is dictated by association with androgen (ligand) and through interaction with co-activators and co-repressors. We have shown previously that cyclin D1 functions as a co-repressor to inhibit ligand-dependent androgen receptor activation. We demonstrate that cyclin D1 directly binds the N terminus of the androgen receptor and that this interaction is independent of ligand. Furthermore, we show that the interaction occurs in the nucleus and does not require the LXXLL motif of cyclin D1. Although two distinct transactivation domains exist in the N terminus (AF-1 and AF-5), the data shown support the hypothesis that cyclin D1 targets the AF-1 transactivation function. The constitutively active AF-5 domain was refractory to cyclin D1 inhibition. By contrast, cyclin D1 completely abolished androgen receptor activity, even in the presence of potent androgen receptor co-activators. This action of cyclin D1 at least partially required de-acetylase activity. Finally, we show that transient, ectopic expression of cyclin D1 results in reduced cell cycle progression in androgen-dependent LNCaP cells independent of CDK4 association. Collectively, our data support a model wherein cyclin D1 has a mitogenic (CDK4-dependent) function and an anti-mitogenic function (dependent on regulation of the AF-1 domain) that can collectively control the rate of androgen-dependent cellular proliferation. These findings provide insight into the non-cell cycle functions of cyclin D1 and provide the impetus to study its pleiotropic effects in androgen-dependent cells, especially prostatic adenocarcinomas.

Laminin-5-mediated gene expression in human prostate carcinoma cells

Interactions between extracellular matrix (ECM) proteins and prostate carcinoma cells provide a dynamic model of prostate tumor progression. Previous work in our laboratory showed that laminin-5, an important member of a family of ECM glycoproteins expressed in the basal lamina, is lost in prostate carcinoma. Moreover, we showed that the receptor for laminin-5, the alpha6beta4 integrin, is altered in prostate tumors. However, the genes that laminin-5 potentially regulates and the significance of its loss of expression in prostate cancer are not known. We selected cDNA microarray as a comprehensive and systematic method for surveying and examining gene expression induced by laminin-5. To establish a definitive role for laminin-5 in prostate tumor progression and understand the significance of its loss of expression, we used a cDNA microarray containing 5289 human genes to detect perturbations of gene expression when DU145 prostate carcinoma cells interacted with purified laminin-5 after 0.5, 6, and 24 h. Triplicate experiments showed modulations of four, 61, and 14 genes at 0.5, 6, and 24 h, respectively. Genes associated with signal transduction, cell adhesion, the cell cycle, and cell structure were identified and validated by northern blot analysis. Protein expression was further assessed by immunohistochemistry. Mol. Carcinog. 30:119-129, 2001.